•  Halley's Comet is classed as a short period comet, a classification given to any comet that takes less than 200 years to orbit the Sun. It is believed that it was once a long period comet, but at some point the gravity of one of the Gas Giants (Jupiter, Saturn, Uranus or Neptune) attracted the comet. It didn't collide with any of these planets, but instead was flung into the inner Solar System towards the Sun. After orbiting the Sun, it is flung back outwards before being drawn back. This is kind of like a sling shot effect.
• Halley's Comet is darker than coal, and reflects only 4% of the sunlight it receives. It only shines brightly when it is close enough to the Sun for its dust and vapours to be burnt off.
•  Halley's Comet is shaped like a peanut and is about 15 kilometres (9 miles) long, and 8 kilometres (5 miles) wide and thick.
•  Halley's Comet is estimated to be 4.5 billion years old. 
• Halley's Comet made of composition is comprised of water, hydrocarbons, iron, carbon monoxide, methane, ammonia, and sodium. 
• The first up-close observation of the comet took place on March 4, 1986 when the Soviet Vega 1 probe started sending back images of Halley.
•  Records of humans observing Halley’s Comet go back thousands of years, with appearances noted by Babylonian, Chinese and European star gazers.
• It last appeared in the inner Solar System in 1986 and will return again sometime in 2061.
• American writer Mark Twain was born on November 30th 1835, two weeks after an appearance of Halley's Comet's. In his biography, he stated that he was born with Halley's Comet, and is likely to die with it. Mark Twain died on April 21st 1910 - the day after Halley's Comet reappeared.
  
  (photograph of Halley's Comet was taken January 13,1986, by James W. Young, resident astronomer of JPL's Table Mountain Observatory

•    583 BC        :     First Prediction of the eclipse of the sun
•    130BC         :     Hipparchus calculates distance and size of moon
•    AD 1543      :     Coppernicus shows that the sun is at the centre of the solarsystem
•    1609             :     Johannes Kepler describes laws of planetary motion
•    1610            :     Galileo Galilei discovers moons of jupiter
•    1655            :     Christiaan Huygens discovers Titan, moon of Saturn
•    1668            :      Issac Newton build first reflecting telescope
•    1687            :      Issac Newton publishes theories of motions of planets , etc
•    1705            :      Edmond Halley predicts return of comet
•    1671-84      :      Giovanni Cassini Discovers four moons of Saturn
•    1774            :      Charles Messier compiles star catalogue
•    1781            :       William Herschel discovers 7th planet, uranus
•    1801           :        First asteriod, Ceres, discovered by Giuseppe Piazzi
•    1846           :       Johan Galle and Urbain Le Verrier discover 8th planet Neptune
•    1787-89     :       Herschel finds two moons of uranus and two of saturn
•    1839-40      :       First photographs of moon
•    1894            :      Flagstaff Observatory, Arizona, founded
•    1905           :       Einstein's special theory of Relativity first proposed
•    1908           :       Giant and Dwarf stars described
•    1923           :       Galaxies beyond Milky Way proved
•    1927           :      Big Bang theory first proposed
•    1930           :      Pluto, discovered by Clyde Tombaugh
•    1959           :      First photographs of the far side of the moon by Soviet satellite Luna 3
•    1961           :      First Quasars discovered
•    1967           :      First pulsars identified
•    1971           :      Black Hole first detected
•    1973           :      Skylab space laboratory launched
•    1976           :      Rings of Uranus are discovered
•    1977           :      Voyager deep space probes launched
•    1980           :       Voyager 1 explores Saturn
•    1978           :      Space probes Pioneer 1 and 2 reach Venus
•    1985-89      :      Voyager 2 discovers moons of Uranus and Neptune
•    1994           :       Comet Shoemaker-Levy Observed crashing into Jupiter
•    1995           :      Galileo probe reaches Jupiter
•    1997           :       Mars Pathfinder lands
•    1997           :      Cassini probe launched to Saturn
•    1998           :      International space station construction starts
•    1999           :      Chanda X-Ray observatory Launched
•    2003           :      Galileo probe deliberately crash-landed on Jupiter
•    2006           :      New Horizons space probe launched to pluto

          1. The Cosmic Web:
                                  Most astronomers agree that the biggest thing in the universe is the cosmic web. It’s an endless scaffolding of clusters and superclusters of galaxies surrounded by dark matter and resembles a three dimensional spiderweb. Clusters of galaxies and dark matter make up “hubs” and filaments of galaxies connect these hubs producing a web like appearance



        2. Shapley  Super Cluster :
                                      It is the most massive gravitationally bound object that we currently know of. The Shapley Supercluster is a collection of galaxies some 400+ million light years long. This puts our Milky Way galaxy around 4,000 times smaller



       3.  Boötes void :
                                The Boötes void or the Great Void is a huge and approximately spherically shaped region of space, containing very few galaxies. It is located in the vicinity of the constellation Boötes, hence its name. Its center is located at approximately right ascension 14^h 20^m and declination 26°



        4. Lyman Alpha Blobs:
                                In astronomy, a Lyman-alpha blob (LAB) is a huge concentration of a gas emitting the Lyman-alpha emission line. LABs are some of the largest known individual objects in the Universe. Some of these gaseous structures are more than 400,000 light years across. So far they have only been found in the high-redshift universe because of the ultraviolet nature of the Lyman-alpha emission line. Since the Earth's atmosphere is very effective at filtering out UV photons, the Lyman-alpha photons must be redshifted in order to be transmitted through the atmosphere. 



         5. Radio Lobes :
                                    Radio lobes are powered by the accretion disk of super massive black holes. Black holes that sit at the center of most galaxies. As material gets consumed by a black hole, some energy and matter is flung away at high speeds which occur at the poles of black holes. These emissions are in the form of radio energy jets which can be seen with a radio telescope. The largest is located in the galaxy is 3C236 which is located in the constellation Leo minor. Its jets span 40 million light years across. The jets from end to end are by far larger than any galaxy.



        6. Largest Galaxy :

                                    The largest that we’ve discovered so far, is arguably the IC1101 super galaxy. It is 6 million light years across. Compare that to the Milky Way which is a mere 100 thousand light years across. IC1101 is a staggering 60 times larger than our own.



       7. Largest Black Hole:
                                   Black holes are not physically large regions of space. But when you include their mass, they are among the top competitors for the largest things in the universe. And quasar OJ287 is the largest black hole we’ve spotted. It’s estimated to be 18 billion times the mass of our sun and is a supermassive black hole located in the center of a galaxy.



     8. Largest Star:
                                    VY Canis Majoris is the largest star (in diameter) that we know of. It’s in a class of star known as Red Hyper Giants. It’s 2,000 times wider than the sun and would take the world’s fastest race car 2,600 years to circle it once. If you replaced our Sun with VY Canis Majoris, it’s radius would extend out beyond Saturn.



    9. Largest Planet:
                                   Jupiter is the largest planet in our Solar System, scientists have discovered a larger one in another Solar System in the constellation of Hercules. Discovered in 2006, the planet is known as TrES-4. Its diameter is 1.7 times that of Jupiter’s. Even though it is 70% larger than Jupiter is, the planet’s mass is only 75% of Jupiter’s mass



 10. Largest Asteriod:
                           Ceres is the largest asteroid we know of. It is almost 600 miles in diameter which makes it as large as California. It’s massive enough that its gravity forces it to have a spherical shape and also shares the title of ‘Dwarf Planet’. 
 

                                                      Dwarf planets are worlds that are too small to be considered full-fledged planets, but too large to fall into smaller categories.In recent years, there's been a lot of hubbub about Pluto losing its status as one of the planets in our solar system. Pluto is no longer considered the ninth planet in the series of major planetary objects, but instead is now just one of the many so-called "dwarf planets." Astronomers estimate that there could be as many as 200 dwarf planets in the solar system and Kuiper Belt.
                                                       The International Astronomical Union defines a planet as being in orbit around the sun, has enough gravity to pull its mass into a rounded shape (hydrostatic equilibrium), and has cleared its orbit of other, smaller objects. This last criterion is the point at which planets and dwarf planets differ. A planet's gravity either attracts or pushes away the smaller bodies that would otherwise intersect its orbit; the gravity of a dwarf planet is not sufficient to make this happen
 
                                                        Pluto, Eris, Haumea, and Makemake are all known as "plutoids," unlike the asteroidal dwarf planetoid Ceres. A plutoid is a dwarf planet with an orbit outside that of Neptune. Plutoids are sometimes also referred to as "ice dwarfs" due to their diminutive size and cold surface temperatures.
                                                         The outer planets show evidence of interaction with plutoids. The largest moon of Neptune is likely a captured plutoid, and it is even possible that the odd tilt of Uranus on its axis is due to a collision with a plutoid. Similarly to dwarf planets, there are potentially hundreds of plutoid objects in the solar system that have yet to be given official status.


Facts : 
              In 2006 the International Astronomical Union adopted the term ‘dwarf planet’ for solar system objects that were bigger than small solar system bodies such as comets and asteroids but not quite planets.

               All the dwarf planets are found in the Kuiper Belt with the exception of Ceres which is found in the asteroid belt.

               No dwarf planets have yet been visited by space probes though in 2015 NASA’s Dawn and New Horizons missions will reach Ceres and Pluto respectively.
            

                                             Asteroids are small, airless rocky worlds revolving around the sun that are too small to be called planets. They are also known as planetoids or minor planets. In total, the mass of all the asteroids is less than that of Earth's moon. But despite their size, asteroids can be dangerous. Many have hit Earth in the past, and more will crash into our planet in the future. That's one reason scientists study asteroids and are eager to learn more about their numbers, orbits and physical characteristics. If an asteroid is headed our way, we want to know that.
                                           Most asteroids lie in a vast ring between the orbits of Mars and Jupiter. This main belt holds more than 200 asteroids larger than 60 miles (100 kilometers) in diameter. Scientists estimate the asteroid belt also contains more than 750,000 asteroids larger than three-fifths of a mile (1 kilometer) in diameter and millions of smaller ones. Not everything in the main belt is an asteroid — for instance, comets have recently been discovered there, and Ceres, once thought of only as an asteroid, is now also considered a dwarf planet.  Many asteroids lie outside the main belt. For instance, a number of asteroids called Trojans lie along Jupiter's orbital path. Three groups — Atens, Amors, and Apollos — known as near-Earth asteroids orbit in the inner solar system and sometimes cross the path of Mars and Earth.





 Physical Characteristics : 
                                       
                                       Asteroids can reach as large as Ceres, which is 940 kilometers (about 583 miles) across and is also considered a dwarf planet. On the other hand, one of the smallest, discovered in 1991 and named 1991 BA, is only about 20 feet (6 meters) across.
                                     Nearly all asteroids are irregularly shaped, although a few are nearly spherical, such as Ceres. They are often pitted or cratered — for instance, Vesta has a giant crater some 285 miles (460 km) in diameter.
                                      As asteroids revolve around the Sun in elliptical orbits, they rotate, sometimes tumbling quite erratically. More than 150 asteroids are also known to have a small companion moon, with some having two moons. Binary or double asteroids also exist, in which two asteroids of roughly equal size orbit each other, and triple asteroid systems are known as well. Many asteroids seemingly have been captured by a planet's gravity and become moons — likely candidates include among Mars' moons Phobos and Deimos and most of the distant outer moons of Jupiter, Saturn, Uranus and Neptune.
                                      The average temperature of the surface of a typical asteroid is minus 100 degrees F (minus 73 degrees C). Asteroids have stayed mostly unchanged for billions of years — as such, research into them could reveal a great deal about the early solar system.

 Classification : 
                            In addition to classifications of asteroids based on their orbits, most asteroids fall into three classes based on composition. The C-type or carbonaceous are greyish in color and are the most common, including more than 75 percent of known asteroids. They probably consist of clay and stony silicate rocks, and inhabit the main belt's outer regions. The S-type or silicaceous asteroids are greenish to reddish in color, account for about 17 percent of known asteroids, and dominate the inner asteroid belt. They appear to be made of silicate materials and nickel-iron. The M-type or metallic asteroids are reddish in color, make up most of the rest of the asteroids, and dwell in the middle region of the main belt. They seem to be made up of nickle-iron. There are many other rare types based on composition as well — for instance, V-type asteroids typified by Vesta have a basaltic, volcanic crust

Interesting Facts About Asteroids

                                  This dust is called regolith. It is a rocky rubble more that dust and is the result of constant collisions in space. These collision are between asteroids and any other body that crosses their path. The larger object wins and ends up covered in the rubble from the losing object. Sometimes space weathering has shown that some asteroids are OC meteorites that are covered in regolith