Formation Of The Planets 

 

The formation and evolution of the Solar System began 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud.

Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed.

This model, known as the nebular hypothesis was first developed in the 18th century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace.

Its subsequent development has interwoven a variety of scientific disciplines including astronomy, physics, geology, and planetary science.

 

          Emanuel Swedenborg                             Immanuel Kant                              Pierre-Simon Laplace

Self-accretion of cosmic dust accelerates the growth of the particles into boulder-sized planetesimals. The more massive planetesimals accrete some smaller ones, while others shatter in collisions.

Collisions and gravitational interactions between planetesimals combine to produce Moon-size planetary embryos (protoplanets)

Finally, the planetary embryos collide to form planets.

In the formation of terrestrial planets or planetary cores, several stages can be considered. First, when gas and dust grains collide, they agglomerate by microphysical processes forming micrometre-sized particles.

Planetesimal formation in the centimetre-to-meter range is not well understood, and no convincing explanation is offered as to why such grains would accumulate rather than simply rebound.

This problem is known as the "meter size barrier

A number of mechanisms have been proposed for crossing the 'meter-sized' barrier. Local concentrations of pebbles may form, which then gravitationally collapse into planetesimals the size of large asteroids.

Or the particles may take an active role in their concentration via a feedback mechanism referred to as a streaming instability.

In a streaming instability the interaction between the solids and the gas in the protoplanetary disk results in the growth of local concentrations, as new particles accumulate in the wake of small concentrations, causing them to grow into massive filaments.

Alternatively, if the grains that form due to the agglomeration of dust are highly porous their growth may continue until they become large enough to collapse due to their own gravity.

The planets were originally thought to have formed in or near their current orbits. From that a minimum mass of the nebula i.e. the protoplanetary disc, was derived which was necessary to form the planets – the minimum mass solar nebula. It was derived that the nebula mass must have exceeded 3585 times that of the Earth.

However, this has been questioned during the last 20 years. Currently, many planetary scientists think that the Solar System might have looked very different after its initial formation.

Cores of the Rocky Planets

The cores of the rocky planets were initially characterized by analysing data from spacecraft, such as NASA's Mariner 10 that flew by Mercury and Venus to observe their surface characteristics.

The cores of other planets cannot be measured using seismometers on their surface, so instead they have to be inferred based on calculations from these fly-by observation. Mass and size can provide a first-order calculation of the components that make up the interior of a planetary body.

 

All of the rocky inner planets, as well as the moon, have an iron-dominant core. Venus and Mars have an additional major element in the core.

Venus’ core is believed to be iron-nickel, similarly to Earth. Mars, on the other hand, is believed to have an iron-sulphur core and is separated into an outer liquid layer around an inner solid core.

Mercury has an observed magnetic field, which is believed to be generated within its metallic core. Mercury's core occupies 85% of the planet's radius, making it the largest core relative to the size of the planet in the Solar System.

 

Mercury

Mercury appears to have a solid silicate crust and mantle overlying a solid, iron sulphide outer core layer, a deeper liquid core layer, and a solid inner core.

 

.

 

The inner core of Venus is mostly made up of iron and nickel.

The similarity in size and density between Venus and Earth suggests they share a similar internal structure: a core, mantle, and crust.

Like that of Earth, the Venusian core is at least partially liquid because the two planets have been cooling at about the same rate.

The slightly smaller size of Venus means pressures are 24% lower in its deep interior than Earth's.

 

 

The outer core of the Earth is a liquid layer about 2,260 kilometres thick. It is made of iron and nickel. This is above the Earth's solid inner core and below the mantle.

Its outer boundary is 2,890 km (1,800 mi) beneath the Earth's surface. The transition between the inner core and outer core is approximately 5,000 km (3,100 mi) beneath the Earth's surface.

Without the outer core, life on Earth would be very different. Convection of liquid metals in the outer core creates the Earth's magnetic field. This magnetic field extends outward from the Earth for several thousand kilometres, and creates a protective magnetosphere around the Earth that deflects the Sun's solar wind.

Without this field, the solar wind would directly strike the Earth's atmosphere.This might have removed the Earth's atmosphere, making the planet nearly lifeless. It may have happened to Mars.

 

Mars

Mars possibly hosted a core-generated magnetic field in the past. The dynamo ceased within 0.5 billion years of the planet's formation.

Like Earth, Mars is a differentiated planet, meaning that it has a central core made up of metallic iron and nickel surrounded by a less dense, silicate mantle and crust.

The planet's distinctive red colour is due to the oxidation of iron on its surface.

Outer Gas and Ice Giants

Current understanding of the outer planets in the solar system, the ice and gas giants, theorizes small cores of rock surrounded by a layer of ice, and in Jupiter and Saturn models suggest a large region of liquid metallic hydrogen and helium.

Jupiter and Saturn appear to release a lot more energy than they should be radiating just from the sun, which is attributed to heat released by the hydrogen and helium layer. Uranus does not appear to have a significant heat source, but Neptune has a heat source that is attributed to a “hot” formation.

The giant planets formed further out, beyond the frost line, which is the point between the orbits of Mars and Jupiter where the material is cool enough for volatile icy compounds to remain solid.

The ices that formed the Jovian planets were more abundant than the metals and silicates that formed the terrestrial planets, allowing the giant planets to grow massive enough to capture hydrogen and helium, the lightest and most abundant elements.

 

 

Jupiter

Jupiter has a rock and/or ice core 10–30 times the mass of the Earth, and this core is likely soluble in the gas envelope above, and so primordial in composition.

Jupiter has an observed magnetic field generated within its core, indicating some metallic substance is present. Its magnetic field is the strongest in the Solar System after the Sun's.

 

Saturn

Despite consisting mostly of hydrogen and helium, most of Saturn's mass is not in the gas phase, because hydrogen becomes a liquid at high density.

The temperature, pressure, and density inside Saturn all rise steadily toward the core, which causes hydrogen to be a metal in the deeper layers.

Standard planetary models suggest that the interior of Saturn is similar to that of Jupiter, having a small rocky core surrounded by hydrogen and helium with trace amounts of various volatiles.

 

Uranus

Uranus's mass is roughly 14.5 times that of Earth, making it the least massive of the giant planets. Its diameter is slightly larger than Neptune's at roughly four times that of Earth. A resulting density of 1.27 g/cm3 makes Uranus the second least dense planet, after Saturn. This value indicates that it is made primarily of various ices, such as water, ammonia, and methane.

The standard model of Uranus's structure is that it consists of three layers: a rocky (silicate/iron–nickel) core in the centre, an icy mantle in the middle and an outer gaseous hydrogen/helium envelope.

 

 

Neptune's internal structure resembles that of Uranus. Its atmosphere forms about 5% to 10% of its mass and extends perhaps 10% to 20% of the way towards the core.

The mantle is equivalent to 10 to 15 Earth masses and is rich in water, ammonia and methane.

The conditions may be such that methane decomposes into diamond crystals that rain downwards like hailstones. Scientists also believe that this kind of diamond rain occurs on Jupiter, Saturn, and Uranus.

The core of Neptune is likely composed of iron, nickel and silicates, with an interior model giving a mass about 1.2 times that of Earth.

The pressure at the centre is about twice as high as that at the centre of Earth.

Currently, many planetary scientists think that the Solar System might have looked very different.

Several objects at least as massive as Mercury were present in the inner Solar System, the outer Solar System was much more compact than it is now, and the Kuiper belt was much closer to the Sun.

Models show that density and temperature variations in the disk governed this rate of migration, but the net trend was for the inner planets to migrate inward as the disk dissipated, leaving the planets in their current orbits.

 

 

 

Antikythera Mechanism

The movements of the stars and the planets have been studied in many cultures, to develop calendars and divide time into meaningful units.

Knowledge of the regular repeating cycles of the Sun and stars similarly provided a means of determining direction.

Accurate knowledge of time and direction is crucial in many cultures, and this need has driven people to harness their knowledge of the skies and invent precise instruments to measure and record it.

The Antikythera mechanism is an ancient Greek analogue computer used to predict astronomical positions and eclipses for calendar and astrological purposes decades in advance.

This artefact was retrieved from the sea in 1901, among wreckage retrieved from a wreck off the coast of the Greek island Antikythera.

The instrument is believed to have been designed and constructed by Greek scientists and has been variously dated to about 87 BC, or between 150 and 100 BC, or to 205 BC.

 

       

           Computer Graphic of Front                                     Computer Graphic of Rear

It is a complex clockwork mechanism composed of at least 30 meshing bronze gears.

A team led by Mike Edmunds and Tony Freeth at Cardiff University used modern computer x-ray and high resolution surface scanning to image inside fragments of the crust-encased mechanism and read the faintest inscriptions that once covered the outer casing of the machine.

Detailed imaging of the mechanism suggests that was able it to follow the movements of the Moon and the Sun through the zodiac, to predict eclipses and even to model the irregular orbit of the Moon.

All known fragments of the Antikythera mechanism are now kept at the National Archaeological Museum in Athens, along with a number of artistic reconstructions and replicas of the mechanism to demonstrate how it may have looked and worked.

The knowledge of this technology was lost at some point in antiquity, works with similar complexity did not appear again until the development of mechanical astronomical clocks in Europe in the fourteenth century.

 

An astrolabe is an elaborate inclinometer, historically used by astronomers and navigators to measure the altitude above the horizon of a celestial body, day or night. It can be used to identify stars or planets, to determine local latitude given local time.

An early astrolabe was invented in the Hellenistic civilization between 220 and 150 BC. The astrolabe was a marriage of the planisphere and effectively an analogue calculator capable of working out several different kinds of problems in astronomy.  

 

Astrolabe of Jean Fusoris, made in Paris, 1400

 

A spherical astrolabe from medieval Islamic astronomy, c. 1480, most likely Syria or Egypt, in the Museum of the History of Science, Oxford

 

An astronomical clock, is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the sun, moon, zodiacal constellations, and sometimes major planets.

In the 11th century, the Song dynasty Chinese horologist, mechanical engineer, and astronomer SuSong created a water-driven astronomical clock for his clock-tower of Kaifeng City.

Muslim astronomers and engineers also constructed a variety of highly accurate astronomical clocks for use in their observatories.

The early development of mechanical clocks in Europe is not fully understood, but there is general agreement that by 1300–1330 there existed mechanical clocks (powered by weights rather than by water and using an escapement).

Which were intended for two main purposes: for signalling and notification (e.g. the timing of services and public events), and for modelling the solar system.

 

Prague Astronomical Clock

The clock was first installed in 1410, making it the third-oldest astronomical clock in the world and the oldest clock still operating.

 

An orrery is a mechanical model of the Solar System that illustrates or predicts the relative positions and motions of the planets and moons, usually according to the heliocentric model.

It may also represent the relative sizes of these bodies; but since accurate scaling is often not practical due to the actual large ratio differences, a subdued approximation may be used instead.

Though the Greeks had working planetaria, the first orrery that was a planetarium of the modern era was produced in 1704, and one was presented to Charles Boyle, 4th Earl of Orrery – hence the name.

They are typically driven by a clockwork mechanism with a globe representing the Sun at the centre, and with a planet at the end of each of the arms.

In 1348, Giovanni Dondibuilt the first known clock driven mechanism which displays the ecliptical position of Moon, Sun, Mercury, Venus, Mars, Jupiter and Saturn according to the complicated Ptolemaic planetary theories.

The clock itself is lost, but Dondileft a complete description of the astronomic gear trains of his clock.

 

An orrery made by Robert Brettell Bate, circa 1812

Now in Thinktank, Birmingham Science Museum.

 

The Analytical Engine was a proposed mechanical general-purpose computer designed by English mathematician and computer pioneer Charles Babbage.

It was first described in 1837 as the successor to Babbage's difference engine, a design for a simpler mechanical computer.

The Analytical Engine is one of the most successful achievements of Charles Babbage.

 

Charles Babbage 26 December 1791 to 18 October 1871

He was an English polymath. A mathematician, philosopher, inventor and mechanical engineer,

The Analytical Engine incorporated an arithmetic logic unit, control flow in the form of conditional branching and loops, and integrated memory, making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete.

Babbage was never able to complete construction of his Analytical Engine due to conflicts with his chief engineer and inadequate funding.

Late in his life, Babbage sought ways to build a simplified version of the machine, and assembled a small part of it before his death in 1871.

Babbage was instrumental in founding the Royal Astronomical Society in 1820, initially known as the Astronomical Society of London.

Its original aims were to reduce astronomical calculations to a more standard form, and to circulate data.

These directions were closely connected with Babbage's ideas on computation, and in 1824 he won its Gold Medal, cited "for his invention of an engine for calculating mathematical and astronomical tables".

In 1878, a committee of the British Association for the Advancement of Science described the Analytical Engine as "a marvel of mechanical ingenuity", but recommended against constructing it.

The committee acknowledged the usefulness and value of the machine, but could not estimate the cost of building it, and were unsure whether the machine would function correctly after being built.

Parts of Babbage's incomplete mechanisms are on display in the Science Museum in London.

In 1991, a functioning difference engine was constructed from Babbage's original plans.

Built to tolerances achievable in the 19th century, the success of the finished engine indicated that Babbage's machine would have worked.

 

The Science Museum's Difference Engine No. 2, Built From Babbage's Design

 

Augusta Ada King, Countess of Lovelace

10 December 1815 to 27 November 1852

Augusta Ada King, Countess of Lovelace (née Byron); was an English mathematician and writer, chiefly known for her work on Charles Babbage's proposed Analytical Engine.

She was the first to recognise that the machine had applications beyond pure calculation, and published the first algorithm intended to be carried out by such a machine.

Lovelace was the only legitimate child of poet Lord Byron and his wife Lady Byron. All of Byron's other children were born out of wedlock to other women.

Byron separated from his wife a month after Ada was born and left England forever four months later.

On 8 July 1835, she married William, 8th Baron King, becoming Lady King.

Her educational and social exploits brought her into contact with scientists such as Andrew Crosse, Charles Babbage, Sir David Brewster, Charles Wheatstone, Michael Faraday and the author Charles Dickens

Ada described her approach as "poetical science" and herself as an Analyst.

When Ada was twelve years old, this future "Lady Fairy", as Charles Babbage affectionately called her, decided she wanted to fly. Ada Byron went about the project methodically, thoughtfully, with imagination and passion. Her first step, in February 1828, was to construct wings. She investigated different material and sizes. She considered various materials for the wings: paper, oilsilk, wires, and feathers. She examined the anatomy of birds to determine the right proportion between the wings and the body.

When she was a teenager, her mathematical talents led her to a long working relationship and friendship with fellow British mathematician Charles Babbage, who is known as "the father of computers".

She was in particular interested in Babbage's work on the Analytical Engine. Lovelace first met him in June 1833, through their mutual friend, and her private tutor, Mary Somerville.

In 1840, Babbage was invited to give a seminar at the University of Turin about his Analytical Engine. Luigi Menabrea, a young Italian engineer and the future Prime Minister of Italy, transcribed Babbage's lecture into French.

Babbage's friend Charles Wheatstone commissioned Ada Lovelace to translate Menabrea'spaper into English. She then augmented the paper with notes, which were added to the translation.

Ada Lovelace spent the better part of a year doing this, assisted with input from Babbage.

Ada Lovelace's notes were considered to be the first published algorithm ever specifically tailored for implementation on a computer, and Ada Lovelace has often been cited as the first computer programmer for this reason.

 

 

The ancient Greek philosopher Anaxagoras (428 BC) reasoned that the Sun and Moon were both giant spherical rocks, and that the latter reflected the light of the former.

In his little book On the Face in the Moon's Orb, Plutarch (AD46-120) suggested that the Moon had deep recesses in which the light of the Sun did not reach and that the spots are nothing but the shadows of rivers or deep chasms. He also entertained the possibility that the Moon was inhabited.

By the Middle Ages, before the invention of the telescope, an increasing number of people began to recognise the Moon as a sphere, though many believed that it was "perfectly smooth".

The invention of the optical telescope brought about the first leap in the quality of lunar observations.

Galileo Galilei is generally credited as the first person to use a telescope for astronomical purposes; having made his own telescope in 1609, the mountains and craters on the lunar surface were among his first observations using it.

Thomas Harriot as well as Galilei, drew the first telescopic representation of the Moon and observed it for several years. His drawings, however, remained unpublished.

 

Portrait of Galileo Galilei, 1636

 

Photo of the Moon made by Lewis Rutherfurd in 1865

The physical exploration of the Moon began when Luna 2, which was the sixth of the Soviet Union's Luna programme spacecraft launched to the Moon.

It was the first spacecraft to reach the surface of the Moon, on September 14, 1959. And the first human-made object to make contact with another celestial body.

Luna 2 carried five different instruments to conduct various tests while it was on its way to the Moon.

The spacecraft also carried Soviet pennants. Two of them, located in the spacecraft, were sphere-shaped, with the surface covered by pentagonal elements.

In the center was an explosive charge designed to shatter the sphere, sending the pentagonal shields in all directions.

 

Luna 2

 

Soviet Pennants

In the early 1960's NASA produced and flew a series of Ranger spacecraft to study the moon. These missions, which were the first American spacecraft to land on the moon, helped lay the groundwork for the Apollo program.

All the Ranger spacecraft were designed to head straight into the Moon and send close-range images back to Earth right up until they crashed into the surface.

After a frustrating series of malfunctions (these were the early days of space exploration), Rangers 7, 8 and 9 were successful.

 

NASA Ranger

In November 1960, John F. Kennedy was elected president after a campaign that promised American superiority over the Soviet Union in the fields of space exploration and missile defence.

Despite Kennedy's rhetoric, he did not immediately come to a decision on the status of the Apollo program once he became president. He knew little about the technical details of the space program, and was put off by the massive financial commitment required by a crewed Moon landing.

On April 20, Kennedy sent a memo to Vice President Lyndon B. Johnson, asking Johnson to look into the status of America's space program, and into programs that could offer NASA the opportunity to catch up.

His reply concluded that a crewed Moon landing was far enough in the future that it was likely the United States would achieve it first.

On May 25, 1961, twenty days after the first US crewed spaceflight Freedom 7, Kennedy proposed the manned Moon landing in a Special Message to the Congress on Urgent National Needs:

NASA had not yet sent an astronaut into orbit. Even some NASA employees doubted whether Kennedy's ambitious goal could be met.

NASA Apollo program was the first, and to date only, mission to successfully land humans on the Moon which it did six times.

The program was named after Apollo, the Greek god of light, music, and the sun, by NASA manager Abe Silverstein.

The Soviet Union had sent two tortoises, mealworms, wine flies, and other lifeforms around the Moon on September 15, 1968, aboard Zond 5, and it was believed they might soon repeat the feat with human cosmonauts.

Apollo 1, initially designated AS-204, was the first crewed mission of the United States Apollo program, the program to land the first men on the Moon. Planned as the first low Earth orbital test of the Apollo command and service module with a crew, to launch on February 21, 1967, the mission never flew; a cabin fire during a launch rehearsal test at Cape Kennedy Air Force Station Launch Complex 34 on January 27 killed all three crew members—Command Pilot Virgil I. "Gus" Grissom, Senior Pilot Ed White, and Pilot Roger B. Chaffee—and destroyed the command module.

Apollo 8, the second manned spaceflight mission flown in the United States Apollo space program, was launched on December 21, 1968, and became the first manned spacecraft to leave low Earth orbit, reach the Moon, orbit it, and return.

The three-astronaut crew—Frank Borman, James Lovell, and William Anders—were the first humans to fly to the Moon, to witness and photograph an Earthrise.

The crew orbited the Moon ten times over the course of twenty hours.

 

Apollo 8 Earthrise

Apollo 9 was the third crewed mission in the United States Apollo space program, the second to be sent into orbit by a Saturn V rocket, and the first flight of the full Apollo spacecraft: the command and service module (CSM) with the Lunar Module (LM).

Flown in Low Earth Orbit, its major purposes were to qualify the LM for lunar orbit operations and to show that it and the CSM could separate and move well apart, before rendezvousing and docking again, as they would have to do on subsequent lunar landing missions.

Apollo 10 (Snoopy) was the fourth crewed mission in the United States Apollo space program, and the second (after Apollo 8) to orbit the Moon.

Launched on May 18, 1969, a "dress rehearsal" for the first Moon landing, testing all of the components and procedures, just short of actually landing.

Kennedy's goal was accomplished on the Apollo 11 mission when astronauts Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Module (LM) on July 20, 1969, and walked on the lunar surface.

While Michael Collins remained in lunar orbit in the command and service module (CSM), and all three landed safely on Earth on July 24.

 

Apollo 11 Crew

 

Apollo 11 Lunar Lander Eagle on the Moon

 

Buzz Aldrin

Apollo 12 was the sixth manned flight in the United States Apollo program and the second to land on the Moon. It was launched on November 14, 1969, from the Kennedy Space Center, Florida, four months after Apollo 11.

Commander Charles "Pete" Conrad and Lunar Module Pilot Alan L. Bean performed just over one day and seven hours of lunar surface activity while Command Module Pilot Richard F. Gordon remained in lunar orbit.

 

Apollo 12 Crew

Apollo 13 was the seventh manned mission in the Apollo space program and the third intended to land on the Moon.

The craft was launched on April 11, 1970 from the Kennedy Space Center, Florida, but the lunar landing was aborted after an oxygen tank exploded two days later, crippling the service module (SM) upon which the command module (CM) had depended.

Despite great hardship caused by limited power, loss of cabin heat, shortage of potable water, and the critical need to make makeshift repairs to the carbon dioxide removal system, the crew returned safely to Earth on April 17, 1970, six days after launch.

 

Apollo 13 Crew

Apollo 14 was the eighth crewed mission in the United States Apollo program, the third to land on the Moon, and the first to land in the lunar highlands. It was the last of the "H missions," targeted landings with two-day stays on the Moon with two lunar EVAs, or moonwalks.

Commander Alan Shepard, Command Module Pilot Stuart Roosa, and Lunar Module Pilot Edgar Mitchell launched on their nine-day mission on Sunday, January 31, 1971.

 

Apollo 14 Crew

 

The "Big Bertha" rock was the third largest rock collected during the Apollo program. In 2019, it was discovered that this is the oldest known rock from Earth, 4 billion years old.

Apollo 15 was the ninth crewed mission in the United States' Apollo program, the eighth to be successful, and the fourth to land on the Moon. It was the first mission, with a longer stay on the Moon and a greater focus on science than earlier landings. Apollo 15 saw the first use of the Lunar Roving Vehicle.

The mission began on July 26, 1971, and ended on August 7, the lunar surface exploration taking place between July 30 and August 2.

Commander David Scott and Lunar Module Pilot James Irwin landed near Hadley Rille and explored the local area using the rover, allowing them to travel further from the lunar module than had been possible on previous missions. And collected 170 pounds (77 kg) of surface material.

 

Apollo 15 Crew

 

Apollo15 Luna Rover

Apollo 16 was the tenth crewed mission in the United States Apollo space program, the fifth and second-to-last to land on the Moon, and the second to land in the lunar highlands.

The second of the so-called "J missions," it was crewed by Commander John Young, Lunar Module Pilot Charles Duke and Command Module Pilot Ken Mattingly.

Launched from the Kennedy Space Center in Florida on April 16, 1972, the mission lasted 11 days, 1 hour, and 51 minutes, and concluded on April 27. Young and Duke spent 71 hours just under three days on the lunar surface, during which they conducted three extra-vehicular activities or moonwalks, totalling 20 hours and 14 minutes. The pair drove the Lunar Roving Vehicle (LRV), the second produced and used on the Moon, Young and Duke collected 211 lb of lunar samples for return to Earth.

 

Apollo 16 Crew

Apollo 17 (December 7-19, 1972) was the final mission of NASA's Apollo program; it remains the most recent time humans have travelled beyond low Earth orbit. Its crew consisted of Commander Eugene Cernan, Lunar Module Pilot Harrison Schmitt geologist, and Command Module Pilot Ronald Evans.

Launched on December 7, 1972, Apollo 17 was a "J-type mission" that included three days on the lunar surface, extended scientific capability, and the use of the third Lunar Roving Vehicle (LRV).

Cernan and Schmitt completed three moonwalks, taking lunar samples and deploying scientific instruments.

The landing site had been chosen to further the mission's main goals: to sample lunar highland material, and to investigate the possibility of relatively recent volcanic activity.

Evans remained in lunar orbit in the command and service module (CSM), taking scientific measurements and photographs.

Apllo 17 Crew

 

 

The Lunar plaques are stainless steel commemorative plaques measuring 9 by 7 inches attached to the ladders on the descent stages of the Apollo Lunar Modules flown on lunar landing missions Apollo 11 through Apollo 17, to be left permanently on the lunar surface.

Today, India, China, and Japan all have lunar exploration projects in development. The United States' own plan is perhaps the most ambitious to return humans to the moon by 2024 and eventually use the moon as a staging point for human flight to Mars and beyond.

NASA is taking the next small step in the development of a proposed Deep Space Gateway  NASA describes the gateway as “a lunar-orbiting, crew-tended spaceport” that would also include a habitation module and docking ports.

 

 

 

 

 

Definition of Deep Space

Any region in space outside the solar system.

Hubble Ultra-Deep Field

The Hubble Ultra-Deep Field (HUDF) is an image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies.

The original release was combined from Hubble Space Telescope data accumulated over a period from September 24, 2003, through to January 16, 2004.

Looking back approximately 13 billion years (between 400 and 800 million years after the Big Bang) it has been used to search for galaxies that existed at that time.

 

The Hubble Ultra-Deep Field

In August and September 2009 the HUDF field was observed at longer wavelengths (1.0 to 1.6 micrometers) using the infrared channel of the recently attached Wide Field Camera 3 (WFC3) instrument.

When combined with existing HUDF data, astronomers were able to identify a new list of potentially very distant galaxies. Smaller than a 1 mm by 1 mm square of paper held at 1 meter away, and equal to roughly one twenty-six-millionth of the total area of the sky.

In September 25, 2012, NASA released a further refined version of the Ultra-Deep Field dubbed the eXtremeDeep Field (XDF). The XDF reveals galaxies that span back 13.2 billion years in time, revealing a galaxy theorized to be formed only 450 million years after the big bang event.

In June 3, 2014, NASA released the Hubble Ultra-Deep Field image composed of, for the first time, the full range of ultraviolet to near-infrared light.

In January 23, 2019, released an even deeper version of the infrared images of the Hubble Ultra Deep Field obtained with the WFC3 instrument, named the ABYSS Hubble Ultra Deep Field.

The new images improve the previous reduction of the WFC3/IR images, including careful sky background subtraction around the largest galaxies on the field of view. After this update, some galaxies were found to be almost twice as big as previously measured.

 

The ABYSS Hubble Ultra Deep Field.

Deep-sky Object

Deep-sky object is a term designating any astronomical object that is not an individual star or Solar System object (such as Sun, Moon, planet, comet, etc.).

The classification is used for the most part by amateur astronomers to denote visually observed faint naked eye and telescopic objects such as star clusters, nebulae and galaxies.

This distinction is practical and technical, implying a variety of instruments and techniques appropriate to observation, and does not distinguish the nature of the object itself.

Classifying non-stellar astronomical objects began soon after the invention of the telescope. One of the earliest comprehensive lists was Charles Messier's 1774 Messier catalogue, which included 103 "nebulae" and other faint fuzzy objects he considered a nuisance since they could be mistaken for comets.

As telescopes improved these faint nebulae would be broken into more descriptive scientific classifications such as interstellar clouds, star clusters, and galaxies.

There are many astronomical object types that come under the description of deep-sky objects.

Since the definition is objects that are non-Solar System and non-stellar the list includes.

Star clusters

Open clusters

Globular clusters

Star clusters are very large groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds to millions of old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain fewer than a few hundred members, and are often very young.

 

Globular Cluster Messier 80

 

Open Cluster NGC 3572

Nebulae

Bright nebulae

Emission nebulae

Reflection nebulae

Dark nebulae

Planetary nebulae

A nebula (Latin for 'cloud' or 'fog'. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Most nebulae are of vast size; some are hundreds of light-years in diameter.

A nebula that is barely visible to the human eye from Earth would appear larger, but no brighter, from close by. 

Although denser than the space surrounding them, most nebulae are far less dense than any vacuum created on Earth – a nebular cloud the size of the Earth would have a total mass of only a few kilograms.

Nebulae are often star-forming regions, such as in the "Pillars of Creation" in the Eagle Nebula. In these regions the formations of gas, dust, and other materials "clump" together to form denser regions.

 

Pillars of Creation

Galaxies

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek galaxias (γαλαξίας), literally "milky", a reference to the Milky Way.

Galaxies range in size from dwarfs with just a few hundred million stars to giants with one hundred trillion stars, each orbiting its galaxy's center of mass.

Galaxies are categorized according to their visual morphology as elliptical, spiral, or irregular.

Many galaxies are thought to have supermassive black holes at their centres.

 

 

Deep Space Exploration

Deep space exploration is the branch of astronomy, astronautics and space technology that is involved with exploring the distant regions of outer space.

Physical exploration of space is conducted both by human spaceflights (deep-space astronautics) and by robotic spacecraft.

At present the furthest space probes mankind has constructed and launched from Earth is Voyager 1, which was announced on December 5, 2011, to have reached the outer edge of the Solar system, and entered interstellar space on August 25, 2012. And Voyager 2 entered interstellar space on November 5th 2018.

Deep space exploration further than these vessel's capacity is not yet possible due to limitations in the space-engine technology currently available.

 Some of the best candidates for future deep space engine technologies include anti-matter, nuclear power and beamed propulsion.

The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.

 

 

 

Front page

 

WHY THE STARS MOVE

The movement of Earth makes the stars appear to march across the sky from East to West.

The Earth turns on its axis once a day. And takes a year to go round the Sun. A day in this context is the solar day, the time it takes our planet to complete one rotation on its axis relative to the Sun, which lasts for 23.93 hours. A year is the time it takes for Earth to complete an orbit of the Sun 365.26 days.

 

Movement of Earth

It is the fact that Earth is spinning on its axis that gives us the impression that the Sun and every other celestial object move across the sky.

The distance between Earth and the Sun does change, as our planet’s orbital path is slightly elliptical (like a squashed oval) rather than circular, which leads to a difference of 5 million km between Earth’s closest point to the Sun (perihelion), and its farthest (aphelion).

Poles Apart

On the day that the north pole is tilted 23.5° towards the Sun, the south pole points away by the same inclination.

For the northern hemisphere, the day this happens is the longest in terms of daylight hours (the summer solstice) and for the southern hemisphere it is the shortest (the winter solstice).

As Earth goes round the Sun, its axis always tilts in the same direction in relation to the stars.

Earth’s rotation with respect to the stars only takes 23 hours and 56 minutes for the stars to return to the same position that they were the night before, a period known as the sidereal day

The reason for this discrepancy is that, from one day to the next, Earth completes 1/365th of its orbit around the Sun.

So each night, if you were to look due east, you would be looking out onto a slightly different region of space. This time difference between the solar and sidereal days, although short, causes the stars to rise almost four minutes earlier each day.

Over the weeks and months, this causes the constellations visible in the night sky to change. After 12 months, the stars will have cycled all the way back to the same positions they were in a year ago.

THE ECLIPTIC

The path of the Sun, where you’ll find the rest of the Solar System’s planets, is the second of two important lines that astronomers use to divide up the night sky.

The ecliptic is the invisible path that the Sun traces as it moves around the sky. Think of it like this: if the Sun were to drop breadcrumbs behind it like a cosmic Hansel and Gretel, this is the trail it would leave behind.

The eliptic

All of the planets in the Solar System occupy orbital planes similar to our own. This is because when the Solar System formed, billions of years ago, dust and gas surrounding our nascent star was pulled into a disc under the influence of gravity.

The planets we know today all formed within this disc, and hence they all occupy planes similar to the ecliptic.

It’s this ‘coplanar’ nature of the Sun and planets that allows many of the events that captivate astronomers to occur so often. When our Moon and the Sun line up, we see an eclipse.

When a planet appears to be in the same region of sky as another, or our own Moon, we call it a conjunction. Even seemingly rare events, such as a transit of Venus, are really quite frequent in cosmological terms.

 

Opposition

EQUAL NIGHTS

The two points at which the ecliptic crosses the celestial equator mark the moments when the hours of day and night are roughly the same.

These are known as equinoxes, from the Latin for ‘equal night’. In the northern hemisphere, the equinox in mid-March heralds spring, while the one in mid-September signals the beginning of autumn. At these two points in its orbit, Earth has no tilt relative to the Sun.

From the March equinox, the days slowly lengthen until mid-June, when Earth reaches the point in its orbit where it is at its greatest tilt relative to the Sun a solstice.

This is both the first day of summer and the longest day of the year. At this point, the ecliptic and the celestial equator are at their farthest apart. There’s another solstice six months later in mid December, when the tilt of the poles is completely reversed in relation to the Sun.

YOUR FIRST NIGHT OUTSIDE

Standing under a starry sky, awash with pinpricks of light, can as bewildering as it is mesmerising. So, once you have a clear night, where do you begin? Assuming you live in the northern hemisphere at a mid-to-high latitude – which do if you live in the UK your first goal is to find the group of seven stars known as the Plough.

The Plough is an asterism within the constellation of Ursa Major, the Great Bear; an asterism being a bright and recognisable pattern of stars often (but not always) from a single constellation.

It’s worth noting that each of the Plough’s seven stars has a name; not all stars do.

Big Dipper

Now that you know where Dubhe and Merak are, you’ve discovered two of the most useful stars in the night sky. These two stars are known as the Pointers, because they can make it easy to locate the Pole Star, which astronomers know by the name Polaris. We’ll do this using a technique that has been tried and tested over thousands of years, known as star hopping.

Starting at Merak, draw an imaginary line through Dubhe and keep going. The next star of any note you come across is Polaris.

You’ve already seen how to locate Polaris. Now continue this imaginary line onwards for the same distance that you’ve already come from the Plough, take a slight bend to the right, and you arrive at the constellation of Cassiopeia (the Queen), which appears in the form of a W of stars.

Star hopping

To get to Castor and nearby Pollux, the main stars of Gemini (the Twins) start from the Plough star Megrez. Draw an imaginary line to Merak, diagonally opposite it, and keep going. Almost halfway to your target you’ll pass the two stars that form the front paws of Ursa Major.

STAR HOPPING FROM ORION’S BELT

Extend a line through Orion’s Belt northwest for 22°, where you will find the bright orange star Aldebaran at one tip of a V of stars. This is the Hyades open cluster.

Now extend it 14° farther on and you will find the Pleiades open cluster, commonly called the Seven Sisters.

 

From Orion’s Belt, look about 20° southeast to reach the bright star Sirius which, with Betelgeuse, is part of the Winter Triangle asterism.

Imagine that Sirius and Betelgeuse are the base of an equilateral triangle. At the other apex is the third star, Procyon.

To get to Leo (the Lion) you also start from Megrez, but this time trace a line through Phecda, the star below it in the Plough. Continuing on this line will take you to Regulus, the brightest star in Leo.

The head of the Lion is made by an easily seen hook-shaped asterism called the Sickle that works up from Regulus.

To find Auriga (the Charioteer) start again from Megrez, but this time take a route through Dubhe, to its right. After an expanse of emptiness that includes the very faint constellation of Camelopardalis (the Giraffe) you will eventually arrive at the yellow star Capella, the brightest star of Auriga.

UNDERSTANDING THE NIGHT SKY

LET YOUR EYES ADJUST

This is crucial. If you go outside from a brightly lit room, you’ll probably only see a handful of stars. Wait and let your eyes adjust to the darkness – ideally for 30 minutes – and you’ll notice an incredible difference.

PICK UP A STAR CHART

They are a great way to learn your way around the night sky. You can begin by identifying patterns of bright stars.

From there you can gradually learn your way around the constellations, and before too long they’ll become familiar and you’ll be able navigate your way around the night sky without reference to a book or chart. They frequently list the locations of prominent deep-sky objects, which, being dim, can be harder to locate.

TAKE A RED TORCH AND A COMPASS

Your eyes are dark-adapted, yet you’d still like to .see charts and be sure that you’re not about to step on a hedgehog. The answer is a red-light torch, as dark-adapted eyes are much less sensitive to red light than they are to white. You can buy dedicated red-light torches, or make a DIY one by taking a normal torch and fixing a piece of red acetate over the front. A compass will help you find north, and is useful in using star charts.

AVOID ARTIFICIAL LIGHTS

Make sure any light sources are obscured from your observing position, as they will prevent your eyes from acclimatising to the darkness properly.

If you can get out to the countryside you can take advantage of properly dark skies this will really make a difference.

TAKE YOUR TIME

The fact is that there is an awful lot to get your head around, and no one has ever looked at the night sky and instantly understood how to find their way around.

Not even Sir Patrick Moore was immune to this; he did it by learning one new constellation each night.

HOW TO DEAL WITH LIGHT POLLUTION

This vexation comes in two flavours: sky glow, the rusty orange haze cast by the massed lights over a wide area, and local glare from line-of-sight sources nearby streetlights, security lights, car headlights, even the light emanating from your neighbours’ windows.

Sky glow washes out the night and blots out the stars, while local sources are more prone to ruining your night vision.

For local sources of light pollution, your biggest consideration is where you position your self in your garden. You need to find a spot that puts a barrier between yourself and the irksome source of glare.

That barrier could be anything a fence, a tree, the side of a building – so long as it isn’t so big it also masks the part of the sky you want to look at.

In many places there is a noticeable drop off in sky glow after midnight as more and more people and businesses turn off their interior lights, meaning the wee hours often offer better views. You may also find that your local authority turns off streetlights at a set time.If sky glow is a particular problem, make sure you wait until your chosen target is well clear of the horizon before you attempt to view it.

1 GET YOUR BEARINGS

There’s one thing you need to know before using a planisphere, the cardinal points from where you live.

If you don’t have a compass, use the Sun. It rises roughly in the east and sets roughly in the west.

2 SET THE PLANISPHERE

Let’s say you’re heading out at 9pm on 15 January. Align the 9pm marker on the upper disc with the 15 January marker on the lower disc. The stars in the oval window should now match those in the skies above.

3 HOLD IT UP

To start with, look north, holding the planisphere so that the word ‘north’ is at the bottom. If you change the direction you’re facing, move the planisphere round so that the corresponding compass point is now at the bottom.

4 STAR HOPPING

The central pin represents Polaris andthenorth celestial pole. Just to its lower right will be the seven bright stars of the Plough. Use these and the five stars forming the W shape of Cassiopeia to get to know theconstellations.

THE PLOUGH

Polaris

(the Pole Star)

CASSIOPEIA

 

The Moon

You may be forgiven for thinking that full Moon is the best time to examine our close companion  not so. While this is a good time to see the long, bright rays of ejecta surrounding prominent craters such as Tycho, the high altitude of the Sun in the lunar sky means no shadows are cast, resulting in a washed-out view of the Moon.In general, the best time to view a given lunar feature is when the terminator, the demarcating line that separates lunar day and night, is nearby.

 

The Planets

Because Mercury and Venus are closer to the Sun than Earth, they are known as the inferior planets. The best time to observe them is when they are at their farthest angular distance from the Sun. At these times, the planets are only half lit by the Sun, but after this they swing back into the solar glare, where they become less visible.

 

The planets further out from Earth are called superior planets. The best time to observe the superior planets is when they are close to Earth.This happens at opposition, when the planet is on the opposite side of the sky to the Sun, so we are presented with a fully illuminated disc: visually it’s close to or at its biggest and brightest.

 

METEOROID

A piece of rocky debris in space that is smaller than an asteroid.

METEOR

A small piece of space debris, typically the size of a grain of sand, that has entered Earth’s atmosphere. Heating causes it to glow, causing streaks to appear in the sky. They’re popularly known as ‘shooting stars’.

METEORITE

A meteor that survives being burnt up in Earth’s atmosphere and crashes into the ground. Such fragments are useful sources of information about the history of the Solar System.

RADIANT

The radiant is the point in the sky where meteors (associated with a specific meteor shower) appear to come from. The constellation where the radiant is located determines the name of the meteor shower. So for example, the Orionids have their radiant in Orion.

Meteor showers have what’s known as a ‘peak’, the night when you can expect to see the greatest number of meteors.

The rates can vary quite substantially, but prominent displays such as the Perseids can produce an average of one meteor a minute under clear, moonless skies at their peak.

Don’t look directly at the radiant, but concentrate your gaze high in the direction of the darkest portion of the sky that’s free from obscuring trees and buildings.

 

Wanderers of the Solar System, comets can be amongst the most spectacular of astronomical sights when they appear in our skies.

These mysterious visitors never fail to capture imaginations when they pass by, and after years of careful observations astronomers have coaxed out the secrets hidden by their glow. The heart of a comet is its nucleus, a core of ice laced with rock and dust.

Though sometimes called a ‘dirty snowball’, the ice found on comets is far more exotic than that on Earth. These snowballs travel in huge elliptical orbits, briefly visiting the inner Solar System at one end before travelling billions of kilometres to the outer regions. As the comet gets closer to the Sun, it begins to feel the solar influence even more acutely, as its wind and magnetic field sweep the dust and gas out into a huge tail.

This can extend for millions of kilometres, spanning huge swathes of the Solar System. Some of the tail’s debris is left behind in its orbit to form a meteoroid stream.

Several of these cross the Earth’s orbit, and when we pass through them every year, we see the debris burning up in the atmosphere as a meteor shower.

 

 

Modern Astronomers

 

                        

                          

 

 

      

Edwin Hubble   November 20, 1889   September 28, 1953

Edwin Hubble was born to Virginia Lee Hubble and John Powell Hubble, an insurance executive, in Marshfield, Missouri, and moved to Wheaton, Illinois, in 1900.

In his younger days, he was noted more for his athletic prowess than his intellectual abilities, although he did earn good grades in every subject except for spelling.

His studies at the University of Chicago were concentrated on law, which led to a bachelor of science degree in 1910.

He spent the three years at The Queen's College, Oxford after earning his bachelor's as one of the university's first Rhodes Scholars, initially studying jurisprudence (Study of the Law) instead of science (as a promise to his dying father), and later added literature and Spanish, and earning his master's degree.

Edwin Hubble's arrival at Mount Wilson Observatory, California in 1919 coincided roughly with the completion of the 100-inch (2.5 m) Hooker Telescope, then the world's largest.

At that time, the prevailing view of the cosmos was that the universe consisted entirely of the Milky Way Galaxy.

Using the Hooker Telescope at Mt. Wilson, Hubble identified Cepheid variables (a kind of star that is used as a means to determine the distance from the galaxy also known as standard candle) in several spiral nebulae, including the Andromeda Nebula and Triangulum.

His observations, made in 1922–1923, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside our own.

Using The 100-inch Hooker telescope at Mount Wilson Observatory Hubble measured galaxy distances and a value for the rate of expansion of the universe. Light from many of these nebulae was strongly red-shifted, indicative of high recession velocities known as Hubble’s Law.

Hubble, then a thirty-five-year-old scientist, had his findings first published in The New York Times on November 23, 1924, then presented them to other astronomers at the January 1, 1925 meeting of the American Astronomical Society.

Hubble's name is most widely recognized for the Hubble Space Telescope which was named in his honour, with a model prominently displayed in his hometown of Marshfield, Missouri.

 

 

Bernard Lovell  31 August 1913  6 August 2012

Sir Alfred Charles Bernard Lovell OBE FRS was an English physicist and radio astronomer. He was the first Director of Jodrell Bank Observatory, from 1945 to 1980.

Lovell was born at Oldland Common, Bristol in 1913, the son of Gilbert and Emily Laura Lovell. His childhood hobbies and interests included cricket and music, mainly the piano. He had a Methodist upbringing and attended Kingswood Grammar School.

Lovell studied physics at the University of Bristol obtaining a Bachelor of Science degree in 1934, and a PhD in 1936

At this time he also received lessons from Raymond Jones, a teacher at Bath Technical School and later organist at Bath Abbey. The church organ was one of the main loves of his life, apart from science.

At the end of the Second World War, Lovell attempted to continue his studies of cosmic rays with an ex-military radar detector unit but suffered much background interference from the electric trams on Manchester's Oxford Road.

He moved his equipment to a more remote location, one which was free from such electrical interference, and where he established the Jodrell Bank Observatory, near Goostrey in Cheshire.

 

Early Equipment

With university funding, he constructed the then-largest steerable radio telescope in the world, which now bears his name: the Lovell Telescope.

Over 50 years later, it remains a productive radio telescope, now operated mostly as part of the MERLIN and European VLBI (very-long-baseline interferometry) Network interferometric arrays of radio telescopes.

 

Lovell Radio Telescope 76.2 m (250 ft) in Diameter

 

 

Fred Hoyle June 1915 20 August 2001

Sir Fred Hoyle FRS was a British astronomer who formulated the theory of stellar nucleosynthesis. He also held controversial stances on other scientific matters in particular his rejection of the "Big Bang" theory, a term coined by him on BBC radio, and his promotion of panspermia as the origin of life on Earth.

He also wrote science fiction novels, short stories and radio plays, and co-authored twelve books with his son, Geoffrey Hoyle.

He spent most of his working life at the Institute of Astronomy at Cambridge and served as its director for six years.

Hoyle was a member of the joint policy committee (since 1967), during the planning stage for the 150-inch Anglo-Australian Telescope at Siding Spring Observatory in New South Wales.

He became chairman of the Anglo-Australian Telescope board in 1973, and presided at its inauguration in 1974 by Charles, Prince of Wales.

The telescope was commissioned in 1974 with a view to allowing high quality observations of the sky from the southern hemisphere.

It was the largest telescope in the Southern hemisphere from 1974-1976,

Hoyle, along with Thomas Gold and Hermann Bondi in 1948 began to argue for the universe as being in a "steady state" and formulated their Steady State theory.

The theory tried to explain how the universe could be eternal and essentially unchanging while still having the galaxies we observe moving away from each other.

The theory hinged on the creation of matter between galaxies over time, so that even though galaxies get further apart, new ones that develop between them fill the space they leave.

 

Patrick Moore 4 March 1923  9 December 2012

Sir Patrick Alfred Caldwell-Moore, CBE HonFRS FRAS was an English amateur astronomer who attained prominent status in that field as a writer, researcher, radio commentator and television presenter.

Moore was born in Pinner, Middlesex on 4 March 1923 to Capt. Charles Trachsel Caldwell-Moore MC  and Gertrude. His family moved to Bognor Regis, and subsequently to East Grinstead where he spent his childhood.

His youth was marked by heart problems, which left him in poor health and he was educated at home by private tutors. He developed an interest in astronomy at the age of six and joined the British Astronomical Association at the age of eleven.

Moore was also a self-taught xylophonist, glockenspiel player and pianist, as well as an accomplished composer. He was an amateur cricketer, golfer and chess player.

He was a teacher in Woking and at Holmewood House School in Langton Green, from 1945 to 1953. While teaching at Holmewood he set up a 12½ inch reflector telescope at his home, which he kept into his old age.

He became known as a specialist in Moon observation. He developed a particular interest in the far side of the Moon. And for creating the Caldwell catalogue.

Moore was President of the British Astronomical Association, co-founder and president of the Society for Popular Astronomy.

Author of over seventy books on astronomy, and presenter of the world's longest-running television series with the same original presenter, BBC's The Sky at Night. The programme was originally named Star Map before The Sky at Night was chosen in the Radio Times.

His first television appearance was in a debate about the existence of flying saucers following a spate of reported sightings in the 1950s; Moore argued against Lord Dowding and other UFO proponents.

Moore appears in the Guinness World Records book as the world's longest-serving TV presenter having presented the programme since 1957.

 

 

Carl Sagan November 9, 1934  December 20, 1996

Carl Edward Sagan  was an American astronomer, cosmologist, astrophysicist, astrobiologist, author,  and science communicator in astronomy and other natural sciences.

His best known scientific contribution is research on extra-terrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation.

Carl Sagan was born in Brooklyn, New York. His father, Samuel Sagan, was an immigrant garment worker from part of the then Russian Empire, in today's Ukraine.

His mother, Rachel Molly Gruber, was a housewife from New York. Carl was named in honour of Rachel's biological mother, Clara, in Sagan's words, "the mother she never knew."

Soon after entering elementary school he began to express a strong inquisitiveness about nature. Sagan recalled taking his first trips to the public library alone, at the age of five, when his mother got him a library card.

He wanted to learn what stars were, since none of his friends or their parents could give him a clear answer.

Sagan attended the University of Chicago, which was one of the few colleges he applied to that would consider admitting a sixteen-year-old, despite his excellent high school grades.

He spent most of his career as a professor of astronomy at Cornell University, where he directed the Laboratory for Planetary Studies. Sagan and his works received numerous awards and honours, including the NASA Distinguished Public Service Medal,

Sagan assembled the first physical messages sent into space: the Pioneer plaque and the Voyager Golden Record, universal messages that could potentially be understood by any extra-terrestrial intelligence that might find them.

Sagan argued the now accepted hypothesis that the high surface temperatures of Venus can be attributed to and calculated using the greenhouse effect.

Sagan published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books.

He narrated and co-wrote the award-winning 1980 television series Cosmos: A Personal Voyage. The most widely watched series in the history of American public television. Cosmos has been seen by at least 500 million people across 60 different countries. 

He further contributed insights regarding the atmospheres of Venus and Jupiter as well as seasonal changes on Mars.

He also perceived global warming as a growing, man-made danger and likened it to the natural development of Venus into a hot, life-hostile planet through a kind of runaway greenhouse effect.

 

Stephen Hawking 8 January 1942 14 March 2018

Stephen William Hawking CH CBE FRS FRSA (was an English theoretical physicist, cosmologist, author and Director of Research at the Centre for Theoretical Cosmology within the University of Cambridge.

His scientific works included a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity and the theoretical prediction that black holes emit radiation, often called Hawking radiation.

Hawking was born in Oxford to Frank and Isobel Eileen Hawking his mother was born into a family of doctors in Glasgow.

His wealthy paternal great-grandfather, from Yorkshire, over-extended himself buying farm land and then went bankrupt in the great agricultural depression during the early 20th century.

In 1950, when Hawking's father became head of a division of the National Institute for Medical Research, the family moved to St Albans, Hertfordshire.

In St Albans, the family was considered highly intelligent and somewhat eccentric; meals were often spent with each person silently reading a book. They lived a frugal existence in a large, cluttered, and poorly maintained house and travelled in a converted London taxicab.

Hawking didn’t have the sort of sparkling early academic career you'd expect from a Grade-A genius. He claimed he didn't learn to properly read until he was 8 years old, and his grades never surpassed the average scores of his classmates at St. Albans School.

Of course, there was a reason those same classmates nicknamed him "Einstein"; Hawking built a computer with friends as a teenager, and demonstrated a tremendous capacity for grasping issues of space and time.

Hawking began his university education at University College Oxford, in October 1959 at the age of 17. For the first 18 months, he was bored and lonely  he found the academic work "ridiculously easy".

His physics tutor, Robert Berman, later said, "It was only necessary for him to know that something could be done, and he could do it without looking to see how other people did it."

Hawking achieved commercial success with several works of popular science in which he discusses his own theories and cosmology in general.

His book A Brief History of Time appeared on the British Sunday Times best-seller list for a record-breaking 237 weeks.

In 2002, Hawking was ranked number 25 in the BBC's poll of the 100 Greatest Britons. 

In 1963, Hawking was diagnosed with an early-onset slow-progressing form of motor neurone disease that gradually paralysed him over the decades.

Even after the loss of his speech, he was still able to communicate through a speech-generating device, initially through use of a hand-held switch, and eventually by using a single cheek muscle.

 

Martin Rees 23 June 1942

Martin John Rees, Baron Rees of Ludlow, OM, FRS, FREng, FMedSci, FRAS  is a British cosmologist and astrophysicist.

He has been Astronomer Royal since 1995 and was Master of Trinity College, Cambridge from 2004 to 2012 and President of the Royal Society between 2005 and 2010.

Rees was born in York,  his parents, both teachers, settled with Rees, an only child, in a rural part of Shropshire near the border with Wales.

There, his parents founded Bedstone College, a boarding school based on progressive educational concepts, that thrives to this day.

He was educated at Bedstone College, then from the age of 13 at Shrewsbury School. He studied for the mathematics at Trinity College, Cambridge, graduating with first class honours.

He then undertook post-graduate research at Cambridge and completed a PhD supervised by Dennis Sciama in 1967.

Rees is the author of more than 500 research papers, and he has made contributions to the origin of cosmic microwave background radiation, as well as to galaxy clustering and formation.

His studies of the distribution of quasars led to final disproof of Steady State theory.

Since the 1990s, Rees has worked on gamma-ray bursts, and on how the "cosmic dark ages" ended when the first stars formed.

Rees is an author of books on astronomy and science intended for the lay public and gives many public lectures and broadcasts. In 2010 he was chosen to deliver the Reith Lectures for the BBC.

In a more speculative vein, he has, since the 1970s, been interested in anthropic reasoning, and the possibility that our visible universe is part of a vast "multiverse”.

 

Jocelyn Bell Burnell Born 15 July 1943

Dame Susan Jocelyn Bell Burnell DBE FRS FRSE FRAS is an astrophysicist from Northern Ireland who, as a postgraduate student, co-discovered the first radio pulsars in 1967.

She was credited with "one of the most significant scientific achievements of the 20th century". The discovery was recognised by the award of the 1974 Nobel Prize in Physics, but despite the fact that she was the first to observe the pulsars, Bell was excluded from the recipients of the prize.

Jocelyn Bell was born in Lurgan, Northern Ireland, to M. Allison and G. Philip Bell.

Her father was an architect who had helped design the Armagh Planetarium, and during visits she was encouraged by the staff to pursue astronomy professionally.

She grew up in Lurgan and attended the Preparatory Department of Lurgan College from 1948 to 1956, where she, like the other girls, was not permitted to study science until her parents (and others) protested against the school's policy.

Previously, the girls' curriculum had included such subjects as cooking and cross-stitching rather than science.

She graduated from the University of Glasgow with a Bachelor of Science degree in Natural Philosophy (physics), with honours, in 1965 and obtained a PhD degree from the University of Cambridge in 1969.

At Cambridge, she attended New Hall, Cambridge, and worked with Hewish and others to construct the Interplanetary Scintillation Array to study quasars, which had recently been discovered.

In July 1967, she detected a bit of "scruff" on her chart-recorder papers that tracked across the sky with the stars. She established that the signal was pulsing with great regularity, at a rate of about one pulse every one and a third seconds. Temporarily dubbed "Little Green Man 1" (LGM-1) the source (now known as PSR B1919+21) was identified after several years as a rapidly rotating neutron star. This was later documented by the BBC Horizon series.

In 2018, she was awarded the Special Breakthrough Prize in Fundamental Physics.

She gave the whole of the £2.3m prize money to help women, ethnic minority, and refugee students become physics researchers.

 

 

A constellation is a group of stars that forms an imaginary outline or pattern on the celestial sphere, typically representing an animal, mythological person or creature, a god, or an inanimate object.

The origins of the earliest constellations likely go back to prehistory. People used them to relate stories of their beliefs, experiences, creation, or mythology.

The earliest evidence for the humankind's identification of constellations comes from Mesopotamian (within modern Iraq) inscribed stones and clay writing tablets that date back to 3000 BC.

It seems that the bulk of the Mesopotamian constellations were created within a relatively short interval from around 1300 to 1000 BC. Mesopotamian constellations appeared later in many of the classical Greek constellations.

Different cultures and countries adopted their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized.

Adoption of constellations has changed significantly over time. Many have changed in size or shape. Some became popular, only to drop into obscurity. Others were limited to single cultures or nations.

The 48 traditional Western constellations are Greek. There is only limited information on ancient Greek constellations, with some fragmentary evidence being found in the Works and Days of the Greek poet Hesiod, who mentioned the "heavenly bodies".

Greek astronomy essentially adopted the older Babylonian system in the Hellenistic era, first introduced to Greece in the 4th century BC.

The basis of Western astronomy as taught during Late Antiquity and until the Early Modern period is the Almagest by Ptolemy, written in the 2nd century.

In 1929, the International Astronomical Union (IAU) officially defined 88 constellations across the sky. But these constellations aren't drawn to connect certain stars, they're actually more-or-less rectangular slices of the heavens holding the stars within them.

Alphabetical Listing of IAU Constellations

Andromeda Antlia Apus Aquarius Aquila Ara Aries Auriga

Boötes

Caelum Camelopardalis Cancer Canes Venatici CanisMajor CanisMinor Capricornus Carina Cassiopeia Centaurus Cepheus Cetus Chamaeleon Circinus Columba Coma Berenices Corona Austrina Corona Borealis Corvus Crater Crux Cygnus

Delphinus Dorado Draco

Equuleus Eridanus

Fornax

Gemini Grus

Hercules Horologium Hydra Hydrus

Indus

Lacerta Leo LeoMinor Lepus Libra Lupus Lynx Lyra

Mensa Microscopium Monoceros Musca

Norma

Octans Ophiuchus Orion

Pavo Pegasus Perseus Phoenix Pictor Pisces PiscisAustrinusPuppis Pyxis

Reticulum

Sagitta Sagittarius Scorpius Sculptor Scutum Serpens Sextans

Taurus Telescopium Triangulum Triangulum Australe Tucana

Ursa Major Ursa Minor

Vela Virgo Volans Vulpecula

The month of March marks the beginning of a transition from the Winter Constellations to the Spring Constellations in the northern hemisphere.

Northern Circumpolar Constellations

Constellations in the northern circumpolar sky include Auriga, Camelopardalis, Cassiopeia, Cepheus, Draco, Lynx, Perseus, UrsaMajor, and UrsaMinor. These constellations are always visible in the night sky of the Northern Hemisphere.

 

 

Auriga

Auriga is one of the 88 modern constellations; it was among the 48 constellations listed by Ptolemy. Located north of the celestial equator, its name is the Latin word for “the charioteer”, associating it with various mythological beings.

Traditionally, illustrations of Auriga represent it as a chariot and its driver. The charioteer holds a goat over his left shoulder and has two kids under his left arm.

However, depictions of Auriga have been inconsistent over the years. The reins in his right hand have also been drawn as a whip, though the star Capella is almost always over his left shoulder and the Kids under his left arm.

Its brightest star, Capella, is an unusual multiple star system among the brightest stars in the night sky.

 

 

Camelopardalis

Camelopardalis /kəˌmɛləˈpɑːrdəlɪs/ is a large but faint constellation of the northern sky representing a giraffe. The constellation was introduced in 1612 or 1613 by Petrus Plancius

First attested in English in 1785, the word camelopardalis comes from Latin, and it is the romanization of the Greek "καμηλοπάρδαλις" meaning "giraffe",from "κάμηλος" (kamēlos), "camel" + "πάρδαλις" (pardalis), "leopard", because it has a long neck like a camel and spots like a leopard.

 

 

Cassiopeia

Cassiopeia has a very distinct shape. She looks like a "W" or "M" in the sky, depending on where she is. Some legends say that Cassiopeia was chained into the sky and sometimes hangs upside-down to remind others not to be so boastful.

 

 

King Cepheus

Cepheus was king of a land called Ethiopia in Greek myth. He had a wife named Cassiopeia and a daughter, Andromeda.

Cepheus looks like a house. The point on top is a special star called a cepheid. These stars are used to measure long distances.

 

Draco

Draco is a constellation in the northern sky. Its name is Latin for dragon. It was one of the 48 constellations listed by Ptolemy, and remains one of the 88 modern constellations today.

In Greco- Roman legend, Draco was a dragon killed by the goddess Minerva and tossed into the sky upon his defeat.

The easiest way to spot Draco is by finding his head. It consists of four stars in a trapezoid, burning brightly just north of Hercules.

 

Lynx

Lynx is a constellation named after the animal, usually observed in the northern sky. The constellation was introduced in the late 17th century by Johannes Hevelius. It is a faint constellation, with its brightest stars forming a zigzag line.

 

Perseus

Perseus is a constellation in the northern sky, being named after the Greek mythological hero Perseus. It is one of the 48 ancient constellations listed by Ptolemy, and among the 88 modern constellations.

It is located near several other constellations named after ancient Greek legends surrounding Perseus, including Andromeda to the west and Cassiopeia to the north.

The Perseids are a prominent annual meteor shower that appear to radiate from Perseus from mid-July, peaking in activity between 9th and 14th August each year.

 

 

Ursa Major

Ursa Major is probably the most famous constellation, with the exception of Orion. Whose associated mythology likely dates back into prehistory.

Its Latin name means "greater she-bear", standing as a reference to and in direct contrast with nearby Ursa Minor, the lesser bear.

The Big Dipper or the Plough consisting of seven bright stars of the constellation Ursa Major; six of them are of second magnitude and one, Megrez, of third magnitude.

Four define a "bowl" or "body" and three define a "handle" or "head". It is recognized as a distinct grouping in many cultures.

 

 

Ursa Minor

Ursa Minor, or Little Bear. The body and tail of the bear make up what is known as the Little Dipper. Also called names such as the Plough, the Wain and even the Wagon.

Probably the most important of all is the last star in the tail. This spot is held by the North Star, Polaris.