Sunday, October 11, 2009

Why is it now possible to measure distances from the stars?

Scientists cannot stretch a measuring tape from the Earth to a nearby star, so how do they know how far away they are? It's always been known that the stars are very remote, but it was not until 1838, that the first star distance was measured, using the method of parallax, by F W Bessel. A star, viewed from different points in the Earth's orbit will shift against its background of more distant stars. The deviation in the angle can be used to calculate the distance.

Today, scientists use special cameras to calculate distances. Special types of telescopes are used to photograph large areas of the sky. Scientists also use instruments like a spectroscope, radio telescope, etc. to determine how far is a star from our Earth.

Light years are the unit of distances in space. This sounds like a unit of time, but a light year is actually the distance that light travels in one year. Light travels 299,792 kilometres per second. So, a light year is about 9,460,700,000,000 kms long.

It has been calculated that the nearest galaxy is the Andromeda, which is at a distance of 2.2 million light years, from Earth.

Did you know that the Sun is positioned only 8 light minutes away from Earth?

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