Astronomy

When we talk about distance, we must use certain unit of measurement. We usually use units of miles or kilometers for depicting distance between two places on Earth. But how about on outer space?

If we describe average distance between Earth and Sun, we got the number of 149.598.000 kilometers. And then, we use this number as a unit called “Astronomical Unit” (AU). So, distance from Sun to Earth, Mercury, and Jupiter is 1 AU, 0.38 AU, and 5.2 AU, respectively. Just multiply the number with 149.598.000 and you have the distance in kilometers. Please note that the number is an average distance, and might not describe the actual distance, since all members of Solar System had orbiting the Sun with elliptical path. So, we have longest distance from the object to Sun (called Aphelion), and shortest distance (called Perihelion).

Astronomical Unit is better use to avoid long series of number if we describe it on conventional unit like miles or kilometers. But what if the object lies so far away, beyond our Solar System, such as another star or galaxy?

For such an object, astronomer uses another unit known as “light years”. Light years is defined as the distance that light travels in a vacuum in one year, or approximately 9.46 trillion (9.46 × 10¹²) kilometers. So, we can describe the distance to Proxima Centaury, our nearest “neighbor” star as 4.3 light years.

These distance unit will often to be appearing on our next posts, so please keep it on mind.

Post to: delicious, Digg, ma.gnolia, Stumbleupon