Making Planets or Discovering Them?

Are we pretending to be like God?

If you can imagine a planet, and then discover one that could maybe be a little like the one you imagined, that's the same as making one, right?

Apparently so.  At least one could get that impression, based on two different articles - one from sciencemag.org and the other from arstechnica.com.

Awesome stuff.  Sounds incredible.

But how real is it?

Have we become like God - able to make planets?

The sciencemag.org article is titled How to make a planet just like Earth.  

I enjoy cooking and baking, so I'm expecting to see a recipe, step by step, hopefully with pictures, 'cause I like to verify that what I'm making looks like it's supposed to.  And for baking, it's got to be really exact, otherwise the right chemical reactions won't happen, and I've got a mess.

I also enjoy doing woodworking, so a really nice blueprint with exact dimensions would be anticipated.  I'd really like to see some well laid out cut sheets too. Makes the whole thing so much easier.

The article from arstechnica.com is titled Earth-sized planets discovered by Kepler may really be Earth-like.  This seems to lower the bar for my expectations.  A lot.  But then I read the caption for the picture at the top of this post - With the right ingredients, you can mix up an Earth-like planet - and they go way back up again.  This is really beginning to sound like baking.  And they do have pictures!    

 OK - obviously my expectations are way over the top.  At least I hope that was obvious.  But just look at the way theses things are described - especially from the point of view of someone who only reads the headlines, looks at the pictures, and maybe reads a paragraph or two.  

It really sounds like scientists know a whole lot about what they're doing.  
Here are the first paragraphs from each of the articles.  (Color coding back to the titles will let you know which one.)

Ever since exoplanets were first discovered in the 1990's, astronomers have dreamed of finding an Earth-like planet amongst the stars. Better detection techniques have allowed us to find smaller and smaller exoplanets. But when we spot a planet beyond our Solar System, does “Earth-sized” really mean “Earth-like?” A new study presented at this week’s American Astronomical Society meeting shows that the smallest exoplanets are much more likely to be similar to Earth than we thought.

Only a small number of worlds around other stars look anything like Earth: roughly the same size and at the right distance from their star for liquid water to be present. But are these Earth-like exoplanets really made from the same sort of stuff—a rocky surface, an iron core, and just a dash of water? A study presented here today at a meeting of the American Astronomical Society suggests that exoplanets, at least up to 1.6 times the mass of Earth, follow pretty much the same recipe as our home. So if we’re looking for life out there, we can probably ignore anything bigger than that.

Both sound very positive.  We know what we're doing.  We understand this stuff.  You can trust us.

Let's go a bit deeper.

Does a composition similar to that of Earth mean that the planet is truly Earth-like? There are other factors to consider before this determination can be made. Location in its system is another major factor that contributes to the environment on an exoplanet. For example, Kepler-93b, though Earth-like in composition, is in a very tight, 4.7-day orbit around its star. In order to support liquid water on its surface, an exoplanet needs to be at the right distance, and this one is much too close.

There are other, more nuanced factors in a planet’s history that will ultimately determine if it has liquid water or other conditions needed for it to be considered habitable by life as we know it. Nevertheless, having a composition similar to that of Earth is a good start.

The team calculated the masses of 10 known exoplanets with diameters that are less than 2.7 times that of Earth. Plotting the mass results against the planets’ diameters, the researchers found that the five smallest exoplanets—all less than 1.6 times Earth’s diameter—lay on the curve typical of a largely rocky planet with an iron core, the same curve that Earth and Venus sit on. “This suggests that they have the same recipe as Earth,” Dressing told a press conference here today.