Showing posts with label Comet. Show all posts
Showing posts with label Comet. Show all posts

Halley's Comet

Comet Halley 



                            Orbital period                :            75 years
                            Discovered                    :           1705
                            Last perihelion               :            February 9, 1986
                            Orbits                            :           Sun
                            Discoverer                     :           Edmond Halley
                            Meteor shower spawned:          Orionids, Eta Aquarids







                                                       British astronomer Edmond Halley(1656-1742) was the first to prove that comets travel in orbits, making it possible to calculate when they will next be seen from Earth. He predicted that the comet he saw in1682 would return in1759. It did and was named in his honour.





  •  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
                              Date closest to Sun  and Observations
 25 May 240 BC             :              Seen in China.

  10 October 12 BC          :             Belived to mark the deth of Roman general Agrippa.

  28 June AD 451             :              Belived to mark the defeat of Attila the Hun.

  20 March 1066              :              William believed the comet was the sign of imminent victory over king Harold at the battle of Hastings.


  9 June 1456                    :             The defeat of the Turkish army by papal forces was thought to be linked to the comet.

15 September 1682           :            Observed by Edmond Halley, who predicted its return.

 13 March 1759                 :            The comet's first return, as predicted by Halley, proving his calculations correct.

 16 November 1835           :           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. 

 10 April 1910                  :             There was a panic as many believed the world would come to an end. 

 9 February 1986              :             The Soviet Union sent Vega 1 and Vega 2 to visit Halley's Comet, and the European Space Agency sent Giotto. They recorded data and sent back images of the comet. 

 28 July 2061                    :            Next due to appear.





                   

Posted by Unknown | at 20:59 | 0 comments

Comet-2

Comet - 2





                                                   Comets inspired both awe and alarm, "hairy stars" resembling fiery swords that appeared unpredictably in the sky. Often, comets seemed to be omens of doom — the most ancient known mythology, the Babylonian "Epic of Gilgamesh," described fire, brimstone, and flood with the arrival of a comet, and Emperor Nero of Rome saved himself from the "curse of the comet" by having all possible successors to his throne executed. This fear was not just limited to the distant past — in 1910, people in       Chicago sealed their windows to protect themselves from what they thought was the comet’s poisonous tail.
                                                  For centuries, scientists thought comets traveled in the Earth's atmosphere, but in 1577, observations made by Danish astronomer Tycho Brahe revealed they actually traveled far beyond the moon. Isaac Newton later discovered that comets move in elliptical, oval-shaped orbits around the Sun, and correctly predicted that they could return again and again.
                                                Chinese astronomers kept extensive records on comets for centuries, including observations of Halley's Comet going back to at least 240 BC, historic annals that have proven valuable resources for later astronomers.


Orbital Characteristics : 







                                               Asteroids classify comets based on the durations of their orbits around the sun. Short-period comets need roughly 200 years or less to complete one orbit, long-period comets take more than 200 years, and single-apparition comets are not bound to the sun, on orbits that take them out of the solar system. Recently, scientist have also discovered comets in the main asteroid belt — these main-belt comets might be a key source of water for the inner terrestrial planets.
                                               Scientists think short-period comets, also known as periodic comets, originate from a disk-shaped band of icy objects known as the Kuiper belt beyond Neptune's orbit, with gravitational interactions with the outer planets dragging these bodies inward, where they become active comets. Long-period comets are thought to come from the nearly spherical Oort cloud even further out, which get slung inward by the gravitational pull of passing stars.
Some comets, called sun-grazers, smash right into the sun or get so close that they break up and evaporate

Formation :
              Astronomers think comets are leftovers from the gas, dust, ice and rocks that initially formed the solar system about 4.6 billion years ago.

 Comet Life Cycle :
  •  Some comets are not bound to the sun, on orbits that take them out of the solar system.
  •  Comets lose ice and dust each time they come near the sun, leaving behind trails of debris. Eventually, they can lose all their ices, with some turning into fragile, inactive objects similar to asteroids.
  • Other comets, upon losing all their ices, break up and dissipate into clouds of dust.
  • The orbits comets take sometimes end with them colliding with planets and their moons. Many impact craters seen in the solar system were caused by such collisions.
( Comet Breakup )









Posted by Unknown | at 19:45 | 0 comments

Comet - 1

Comets -1



                                                       Comets are small, fragile, irregularly shaped bodies composed of a mixture of non-volatile grains and frozen gases. They have highly elliptical orbits that bring them very close to the Sun and swing them deeply into space, often beyond the orbit of Pluto. 
                                                       As comets approach the Sun they develop enormous tails of luminous material that extend for millions of kilometers from the head, away from the Sun. When far from the Sun, the nucleus is very cold and its material is frozen solid within the nucleus. In this state comets are sometimes referred to as a "dirty iceberg" or "dirty snowball," since over half of their material is ice. When a comet approaches within a few AU of the Sun, the surface of the nucleus begins to warm, and volatiles evaporate. The evaporated molecules boil off and carry small solid particles with them, forming the comet's coma of gas and dust. 

 Physical Characteristics : 
                                                   The solid nucleus or core of a comet consists mostly of ice and dust coated with dark organic material, with the ice composed mainly of frozen water but perhaps other frozen substances as well, such as ammonia, carbon dioxide, carbon monoxide and methane. The nucleus might have a small rocky core.
                                                    As a comet gets closer to the sun, the ice on the surface of the nucleus begins turning into gas, forming a cloud known as the coma. Radiation from the sun pushes dust particles away from the coma, forming a dust tail, while charged particles from the sun convert some of the comet's gases into ions, forming an ion tail. Since comet tails are shaped by sunlight and the solar wind, they always point away from the sun.
                                                   The nuclei of most comets are thought to measure 10 miles (16 km) or less. Some comets have comas that can reach nearly 1 million miles (1.6 million kilometers) wide, and some have tails reaching 100 million miles (160 million kilometers) long.
                                                    We can see a number of comets with the naked eye when they pass close to the sun because their comas and tails reflect sunlight or even glow because of energy they absorb from the sun. However, most comets are too small or too faint to be seen without a telescope.
                                                     Comets leave a trail of debris behind them that can lead to meteor showers on Earth. For instance, the Perseid meteor shower occurs every year between August 9 and 13 when the Earth passes through the orbit of the Swift-Tuttle comet.

 Naming : 
                                                    In general, comets are named after their discoverer, either a person. For example, comet Shoemaker-Levy 9 got its name because it was the ninth short-periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy. Spacecraft have proven very effective at spotting comets as well, so the names of many comets incorporate the names of missions such as SOHO or WISE.

 (Hally's comet)

COMET HALE-BOPP)


(comet hyakutake)

Posted by Unknown | at 19:41 | 0 comments

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