## Friday, July 24, 2015 ... /////

### Earth-like planet orbiting a Sun-like star

Could it harbor human-like aliens in Škoda-like cars?

Yesterday, NASA announced the discovery of the most accurate impersonation of the Earth-Sun system so far.

Kepler-452 is a G-class star (like the Sun) with almost the same surface temperature as the Sun, 10 percent larger in diameter, 4 percent larger in mass, and 20 percent brighter than the Sun. As you can see, it is almost the same thing as the Sun. But it is also 30% older than the Sun, about 6 billion years.

This star may be found in the constellation of Cygnus (North sky) and its distance from us is 1,400 light years. You need 1,400 years to get there even if you travel (nearly) by the speed of light, the maximum allowed (or marginally forbidden) speed in Nature. That's a long time but it is shorter than the lifespan of the human civilization.

The fastest spaceship that has been constructed so far (New Horizons) would need 26 million years to get there.

A Sun-like star isn't so rare but NASA has also discovered an Earth-like planet orbiting this star, Kepler-452b. It is the second most Earth-like exoplanet that is known so far but because the first Earth-like exoplanet Kepler-438b is orbiting a red dwarf, Kepler-438, the pair Kepler 452-452b is the most Sun-Earth-like exosystem. If you believe that both a planet and a star is needed to obtain life like ours, 452-452b is better.

The radius of the new planet is some 1.4-1.8 times larger than the Earth's radius and the mass is 3-7 times heavier than the Earth's mass. The gravitational acceleration could therefore be about 2 times larger than ours, $2g$. From the viewpoint of the planetary surface, their Sun looks almost identical to our Sun as seen from the Earth. The surface temperature on the planet could be almost identical to the temperature on Earth, plus minus a dozen of degrees or two.

One year (orbit) takes about 385 terrestrial days, almost the same period as our annual cycles.

All the "usual" conditions for life to emerge seem to be satisfied and the life plus smartphones have had 1.5 billion extra years to have evolved. I think that if there's been no advanced life on Kepler-452b, the widespread opinion that the life is "everywhere on habitable zone planets" etc. is simply falsified. So you should better find some aliens over there. Do you really believe that there is alien life on Kepler-452b? I don't.

Some people will probably be sending messages to Kepler-452b. If you wait for 2,800 years, you may get a reply. "Hi, Kepler-452bians, how are you?" [2,800 years of silence] "I don't speak English; could you please repeat the same sentence in Czech?"

Aside from these lagging telephone conversations, there is one more possible application of Kepler-452b. Ecoterrorists have been telling us for years that there's no Planet B. Well, there is a Planet B. There are probably many Planets B like that. We may use this Planet B as a backup copy of the terrestrial life.

Do you think that the mankind is capable of sending a spaceship over there that will be accurately directed to the target and land on Kepler-452b in 26 million years? We could send a Noah's arc to Kepler-452b – lots of samples of bacteria and perhaps some frozen seeds and eggs that may kickstart life over there.

After all, as some science-fiction movies suggest, that's how life could have started on Earth, too. ;-) I just saw a movie like that two weeks ago. In that movie, life on Earth had been ignited by the Martians.

My expectations are that 1) life is very rare in the Universe and the absence of advanced life on planets like Kepler-452b will gradually convince people that this point of mine is right; 2) even when life exists somewhere, it's rather likely that it was sent there deliberately from other places of the Cosmos, and as we start to send Noah's Arcs into many directions, we will be increasingly realizing that this is what could have happened on Earth, too.