Comet:
The name comet has been derived from the Greek word Kometes meaning ”Hair Like”. A comet is a large snowball of frozen gases with very little solid matter. it possesses a small nucleus of ice and dust surrounded by a bright cloud of gas and dust. there are about 100,000 comets in our solar system. The comets can be classified into short-period comets and long-period comets. Out of these, the former such as Hailey’s Comet has an orbital period of fewer than 150 years whereas the latter have orbital periods of ten thousand years. Some important comets are detailed as under:
(1). Hailey’s Comet:
This comet was discovered by Edmund Hailey in 1682. This comet appears after 76 years period. In 1705, Edmund Hailey said that the comet appearing in the years 1531, 1607, 1682 was the same as Hailey’s comet. according to Hailey’s prediction, this comet reappeared in 1758, 1910, 1986.
(2). Comet Smith Tuttle:
This comet was first sighted in 1862 and reappeared in 1992. comet ‘Smith Tuttle is a k kilometer huge ball traveling with a speed of 60 km/s.
(3). Comet Shoemaker Levy-9:
This comet was discovered by scientists Shoemaker, Carolyn, and Levy. It is about 10 km long and weighs about 500 billion tons.
A comet can have a nucleus up to 1000 miles in diameter and a tail up to 20 million miles long. On 16th July 1994, comet Shoemaker was broken into 21 pieces when it crashed into the surface of Jupiter producing scars on the planet.
Stars:
A star is a gigantic ball of superheated gas that keeps hot through nuclear reactions in its center. Sun is also a star in which heat and light are produced through the fusion of hydrogen and fission of Helium. It is estimated that the temperature at the core of the Sun is 36 million-degree Fahrenheit. Thus Star is a luminous body in the sky. Large stars explode supernovae and the surviving core forms Neutron Stars or Black Hole. Through their gravitational forces, the stars form galaxies by attracting millions of other smaller stars.
Brightest Stars of the Universe
| Sr. No | Name of Stars | Constellations | Mag | Distance in Light years |
| 1 | Serius | Canis Major | -1.5 | 8 |
| 2 | Canopus | Carina | -0.9 | 650 |
| 3 | Alpha Centari | Centaurus | 0.1 | 4 |
| 4 | Vega | Lyra | 0.1 | 23 |
| 5 | Capella | Auriga | 0.2 | 42 |
| 6 | Arcturiss | Bootes | 0.2 | 32 |
| 7 | Rigel | Orion | 0.3 | 545 |
| 8 | Procyon | Canis Minor | 0.5 | 10 |
| 9 | Achemar | Eridanus | 0.6 | 70 |
| 10 | Beta Centauri | Centarius | 0.9 | 130 |
| 11 | Altair | Aquita | 0.9 | 18 |
| 12 | Betelgewse | Orion | 0.9 | 600 |
| 13 | Aldebaran | Taurus | 1.1 | 54 |
| 14 | Spica | Virgo | 1.2 | 170 |
| 15 | Pollux | Gemini | 1.2 | 90 |
| 16 | Antares | Scorpions | 1.2 | 170 |
| 17 | Fomalhunt | Piscis | 1.3 | 27 |
| 18 | Deneb | Cygnus | 1.3 | 465 |
| 19 | Regulus | Leo | 1.3 | 70 |
| 20 | Beta Crucis | Crux | 1.5 | 465 |
| 21 | Eta Carinae | Carina | 1.7 | 465 |
| 22 | Alpha One | Crux | 1.6 | 150 |
| 23 | Castor | Gemini | 1.6 | 44 |
| 24 | Gamma Crucis | Crux | 1.6 | 44 |
| 25 | Epsilon Canis | Canis Major | 1.6 | 325 |
| 26 | Epsilon Ursae | ursa Major | 1.7 | 50 |
| 27 | Bellatrix | Orion | 1.7 | 215 |
| 28 | Lambde Scorpii | Scorpion | 1.7 | 325 |
| 29 | Epsilon Carina | Carina | 1.7 | 325 |
| 30 | Mira | Cetus | 2.1 | 250 |