[LINK] On the discovery of ancient planets around Kepler-444

[rfmcdonald]

Bad Astronomy's Phil Plait notes the discovery of five rocky planets in orbit of nearbyish orange dwarf Kepler-444 and what this means.

•The star is called Kepler-444. It’s a bit cooler, more orange, and smaller than the Sun (a K0 dwarf, if you want the details), and is about 117 light-years from Earth. That’s relatively close! Amazingly, it’s actually a triple-star system: There’s a pair of cool red M dwarfs orbiting each other, and the pair in turn orbits the K star. The binary is about 10 billion kilometers from the K star, about twice the distance Neptune is from the Sun.

•The five planets orbit the primary K star, and are called Kepler-444b up to Kepler-444f. All five are smaller than Earth, and get bigger in order with their distance from the star: Kepler-444b has a diameter of 0.403 Earth, Kepler-444c is 0.497 Earth, d is 0.530, e is 0.546, and f is the biggest at 0.741 our home planet’s size.

The import of this particular discovery? Kepler-444 is ancient, just a couple of billion years older than the universe. Earth-like environments plausibly existed very early on, environments capable of sustaining life.

When Kepler-444 formed, there were relatively fewer of these heavy elements, and spectra of the star confirm a paucity of elements like iron. We’ve discovered enough exoplanets now that we see an interesting relationship between heavy elements and planets: Gas giants (like Jupiter and Saturn) tend to form around stars that have more heavy elements; these elements aid in the formation of larger planets. But when you look at smaller, more Earth-sized planets, that relationship goes away. Smaller planets form around stars that have lots of heavy elements, and they also form around stars that have relatively few.

The Kepler-444 system supports this. A gas giant planet would’ve been seen, so it looks like these five planets are all it has (or the biggest it has), and each is small and presumably rocky.

[. . .]

Take a step back and realize that what this means is that Earth-sized planets could form around Sunlike stars even 11 billion years ago! That may have profound implications for life.

You may have heard of the Fermi paradox: If life is easy to get started on planets, then where are the aliens? We do know that life formed on Earth not too long after the planet’s crust had cooled enough to support it. Let’s say it takes 4 billion years for those protozoa to evolve and build spaceships. It turns out that, even with the vast distances between stars and limiting your ships to far less than the speed of light, you can colonize the entire galaxy in just a few million years. That’s far less than the age of the galaxy.

Perhaps you see the problem. If planets like Earth formed 11 billion years ago, and happened to form at the right distance for more clement conditions on the surface, life could have arisen long enough ago and started building spaceships long before the Earth even formed! They’d have planted their flags on every Earth-sized habitable planet in the Milky Way by now.

Where are they?