Thursday, December 15, 2011

Exoplanets, Kepler 22b, and the speed of light

About a week ago NASA announced the discovery of yet another exoplanet (so far about two thousand has been discovered and we are discovering more every week). What was special about this exoplanet which has the name kepler 22b, was that it was the most earth like discovered to date. Its radius is 2.4 times the radius of the earth and the orbital period is about 290 days. Depending on how much atmosphere the planet has its surface temperature would be either -11C or +22C (with atmosphere similar to hours). In other words, this could potentially be a planet that we could live on, just one problem, it is 600 lights years away from us... This means that it is hard to get to... Here is my calculation.

  • 600 light years is how long light travels in 600 years
  • In one second light travels 300.000 kilometers or 7.5 times around the earth, or 3/4 of the way to the moon (384.000 kilometers)
  • In one minute light travel 60 x 300.000 kilometers = 18.000.000 kilometers, 18 million kilometers
  • In one hour light travels 60 x 60 x 300.000 kilometers = kilometers, 1 billion kilometers
  • In one day light travels 24 x 60 x 60 x 300.000 kilometers = 25.920.000.000, 26 billion kilometers
  • In one years light travels 365 x 24 x 60 x 60 x 300.000  kilometers = 9.460.800.000.000, 9.5 trillion kilometers
  • In 600 years light travels 600 x 365 x 24 x 60 x 60 x 300.000 kilometers = 5.676.480.000.000.000, 5.7 quadrillion kilometers.

Some distances to compare this to:

  • The earths circumference is 40.000 kilometers
  • The distance to the moon is 384.000 kilometers
  • The distance to Mars from earth (when it is at the nearest point) is 54.000.000 kilometers
  • The distance to the sun is one AU which is 1.500.000.000 or 1.5 billion kilometers 
  • The distance to uranus is 2.570.000.000, or 2.57 billion kilometers
  • Distance to nearest star, called Proxima centauri (which is not the sun) is 4.22 light years or 39.900.000.000.000 kilometers, or 39 trillion kilometers away

How long would it take to go to exoplanet Kepler 22b? Well, that depends on the speed of your spacecraft of course. According to wikipedia, the fastest spacecraft we have build so far is the helios probe (unmanned), which had a maximum speed of approximately 260.000 kilometers per hour or about 71 kilometers per second. If we assume that space research gets lots of money and manage to recruit clever scientists and we eventually get a spacecraft that goes more than 10 times as fast, say 1000 kilometers per second then it would take

5.676.480.000.000.000 / 1000 = 5.676.480.000.000 or 5.7 trillion seconds, which translates to 180.000 years, or about 6000 human generations. In other words, if you went not only would you have to spend the rest of your life travelling in space but your son or daughter would also have to spend their life on the spacecraft. Also your grandchild, grand grand child, grand grand grand child and grand grand grand grand grand grand grand (six thousand times), would have to live on the spacecraft. It seems likely that on the

In other words we need to find an exoplanet that is much closer and still earth-like, however, I am optimistic!


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Anonymous said...

It was found another habitable planet. It's called GJ667Cc and is at 24 light years from us.

rasmussenanders said...


I have missed that, what is it called.
Guess even 24 light years is too much, but there is certainly hope.