Light Years

We've all heard the term 'light year', and may even know it as 'the distance light travels in a year'. Which is exactly true. End of story? Not quite.

The distance of a light year had been developed for a long time.The first appearance of it used as measurement of distance was in 1838 by Friedrich Bessel. Since then, there are all sorts of other measurements using light, such as the 'light-month' (distance light travels in a month), the kilolight-year (1,000 light years), the megalight-year (one million light years), and the gigalight-year (one billion light years).

In space, the distances are so vast that miles just don't seem to work as a valid measurement. To show you what I mean, take the sun. It's close enough that miles seem to be just okay as a measurement: it's approximately 93 million miles away (93,000,000). That's a long way. It's so far that if the light of the sun would vanish, it would take eight minutes for us to notice here on earth. To give you another example, the farthest (accepted) planet from the sun is Neptune, which is approximately 2.8 billion miles away (2,800,000,000), and just the distance from the sun in one direction and not the whole orbit. But what about the next closest star? The next closest star is called Proxima Centauri. How far is it? It's around 24 trillion miles away (24,000,000,000,000). And that's the closest star. How many zeros would it take if they were farther away? Many, many, many more zeros. And that's one of the reasons we have the light year.

To get a simple distance of the light year, you must first take the distance light travels in a second, which is 186,000 miles, then you multiply up. You multiply 186,000 times 60 (for seconds in a minute), then another 60 (for minutes in an hour), then 24 (for hours in a day, then 365 (for days in a year). I'll save you the trouble of figuring it out: it's just under 6 trillion miles (6,000,000,000,000). So how far away is Proxima Centauri in light years? It's about 4.22 light years. Doesn't seem far at all now. However, you have to keep in mind that it means that if you were traveling at the speed of light, it would take you 4.22 years to reach Proxima Centauri.

Once you grasp how large a light year is, then you begin to understand the vast distances that exist in space. The Milky Way galaxy (our own) is approximately 100,000 light years across. The closest galaxy out of the range of our own is the Large Megallanic Cloud, which is about 180,000 light years away. The closest spiral galaxy to our own is the Andromeda Galaxy, which is 2 million light years away (2,000,000).

So what's the farthest objects seen? The farthest confirmed galaxy is called IOK-1, and it is 12.9 billion light years away (12,900,000,000). However, in 2009, what appeared to be another galaxy even farther away was found. It's called Abell 1835 IR1916, and it's about 13.2 billion light years away (13,200,000,000). However, there is a lot of speculation and controversy as to whether or not this latest discovery is actually a galaxy or not.

Bet you didn't know that!