ASTRONOMY

Compiled by Chilman Sahni

Astronomy is the scientific study of the universe and the bodies it contains, known as the celestial bodies. The scientists who study, or specialize in, astronomy are called Astronomers.

LIGHT YEARS

A light year measures distance, not time. The distance that light covers or travels in one year is called a Light Year. Lights from different bodies reach earth in different periods of time. For example the light reaches earth from moon in 1.26 seconds while from the sun it takes 08 minutes and 17 seconds. From the furthest visible star light reaches the earth 2,309,000 years and from the most distant known quasar it would take  14,000,000,000 years.

WHY DO STARS TWINKLE?

 As we know our planet is surrounded with atmosphere. Stars seem to twinkle because we see them through the layers of the Earth’s atmosphere, comprising nitrogen (78 per cent), oxygen (21 per cent), argon (0.9 per cent), carbon dioxide (0.03 per cent), varying amounts of water vapour, and trace amounts of hydrogen, ozone, methane, carbon monoxide, helium, neon, krypton, and xenon. As light passes through these layers, it is distorted so that the amount of light we actually see changes constantly. The stars near the horizon appear to twinkle the most because the light is passing through a greater depth of atmosphere.

STAR

 A star is a luminous body of gas, mostly hydrogen and helium.

BRIGHTEST STAR

The Sun looks the brightest because it is nearest to the earth and is part of our solar system. However, outside our solar system the brightest star as seen from Earth is Sirius, known as the Dog Star, in the constellation of Canis Major. It has a diameter of 149,598,020km and is more than 24 times brighter than the Sun. The star Cygnus OB2 No 12, discovered in 1992, is so far away that it cannot be seen from the earth. It may be the brightest star in the galaxy – up to 6 million times as bright as sun!

HEAVIEST STAR

 HDE 269810 is a star in the large maggellanic cloud – 170,000 light years from the earth. It has been discovered by the Hopkins Ultraviolet Telescope to be 190 times as heavy as our Sun.

Q- Which is the star nearest to earth? How many years would it take to reach it with the help of a spaceship?

Ans: Proxima Centauri, discovered in 1915, is 4.22 light years (39,953,525,879,212km) from Earth. A spaceship moving at 40,000km/h, which is faster than any human has yet travelled in space, would take more than 114,000 years to reach it.

LARGEST ORION CONSTELLATION

 The largest star is the M-class supergiant Betelgeuse, or Alpha Orionis. It is the top left star in the constellation of Orion, which is 300 light years away. It has a diameter of 700 million km, which is about 500 times greater than Sun.

SUPERNOVAE

 These are vast expansions in which a whole star is blown up. They are extremely bright, rivaling for a few days the combined light output of all the stars in the galaxy. Supernovae are rare – the last one in our galaxy was seen in 1604 by the German astronomer Johannes Kepler.

QUASARS

 Quasars are extremely distant radio galaxies – galaxies giving out large amounts of radio energy – and the brightest objects in the universe. Even those near the most distant edge of the observable Universe are easily detected by small radio

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