February 27, 2017

More New Earths?

"Scientists say life may have already evolved on at least three of the planets."

Every time they announce that new "Earth-like" planets have been discovered, it is the same thing over and over again.

The headlines claim that three of the planets orbiting TRAPPIST-1 "could support alien life." But looking closer, the only reason they say that is because these planets might have temperatures that would keep water in liquid form--if they have water. Then the assumption is that since Earth isn't anything special (assumption), life must spring up fairly easily when there is liquid water (assumption).

The vast majority of planets that have been discovered elsewhere are "Hot Jupiters" i.e., enormous gas giants orbiting extremely close to their star, with no solid surface and temperatures that would make life impossible. So when the articles say that these planets are "just like earth" it is only by comparison to these Hot Jupiters.

The planets around TRAPPIST-1 are similar to Earth in mass, but still very different from Earth. Here are a few of the differences: 
  1. They orbit a very small "ultra cool dwarf star" about 11% the radius of our yellow Sun. 
  2. These planets are tidally locked to the star, meaning that one side of the planet always faces the star and the other side always faces away. This means that one side would be extremely hot and the other extremely cold. The only place liquid water might exists would be on the thin strip between the two halves. 
  3. The three planets that could maintain liquid water (e, f, and g) are extremely close to their star. The closest is only 2.8% of the distance from its star that Earth is from the Sun. The furthers of the three is 4.5% the distance of the Earth from the Sun. This means they would be much more susceptible to solar flares and radiation. 
  4. These planets orbit their star every 6-12 days. That is a very short year!
Also remember that any pictures you see of these planets are artist interpretations. We do not have actual photographs of these planets. The planets are detected by noticing the dimming of the star as the planets block some of the light when they orbit in front of it. The pictures--like the NASA illustration above--may show oceans, but those are from the artist rather than evidence.

I wrote an article on this several years ago about another planet they claimed was "just like Earth." Most of what I wrote applies to these new planets as well. The one big difference is that at the time they had only discovered about 500 planets outside our solar system. Now, the number is about 3,500. However, of the 3,500 they only think that maybe 22 do not already have the possibility of supporting life ruled out. That about half of 1%. For the other 99.4% they know there isn't the slightest chance.

I love these scientific discoveries, but what they tell me is that Earth is much more special than we assume.

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