This was a fascinating find, as the planet discovered — Kepler-10b — is only 1.4 times the size of Earth, and probably terrestrial (rocks and metal; not a gas giant) in nature. This discovery marks the smallest exoplanet yet discovered! Not bad, for something 560 light years away.
Remember, Kepler’s goal is to discover “Earth-like” planets, and then determine how many of them might be in a habitable zone. Is Kepler-10b habitable? It would be highly unlikely. The planet orbits its host star, Kepler 10 (see how they do that?), in an orbit that brings it much closer than Mercury is to the Sun; more than 20 times closer. This means Kepler-10b is hot… several thousand degrees hot! On top of that, it has more than 4-and-half times the mass of the Earth. Standing on Kepler-10b would give new meaning to the phrase, “hot and heavy”.
Another interesting bit of information, is that it’s expected to be tidally locked to Kepler 10. Just as the Moon only shows its one face to Earth, Kepler-10b only shows one face to its star. My imagination quickly conjures up an imagination of a planet habitable on one side, and a scorched realm of hellfire on the other — but the facts probably indicate the entire thing is closer to the latter; a big dense glob of molten material.
So, let’s quickly recap some of the highlights of Kepler’s 9th confirmed exoplanet discovery.
Diameter: 1.4 Earths
Mass: 4.6 Earth mass
Smallest exoplanet ever discovered
Orbital period: .84 days (that thing is screaming around the Kepler 10)
Harbors Life?: Highly improbably (no, not even arsenic-based life!)
Following the announcement, NASA/Kepler held a chat with Kepler Mission expert, Natalie Batalha. It was open to anyone who wanted to join in, and I noticed about 250 participants during the event. There were some great questions and answers, and a full transcript should be up within a couple of days.
I collected a few questions and answers to keep you interested while we wait:
Q: Can Kepler determine anything about the chemical content of a candidate planet’s atmosphere to determine if it would be suitable for life as we know it?
Natalie: Kepler can not probe the atmosphere of the planet, no. However, I fully expect other telescopes and missions to do transmission spectroscopy to see if it has an atmosphere. With transmission spectroscopy, you observe the planet when it is right in front of the star (allowing starlight to stream through its atmosphere) and then you observe it when it is not in front of the star. Then, you compare the two to see what the atmosphere might have done to the starlight.
Q: How do you measure the planet mass, size and the distance to the star? And the planet composition?
Natalie: Mass comes from the Doppler measurements of the wobble of the star as the planet/star orit about their commone center of mass. Radius comes from the amount of dimming of starlight that occurs during transit. The distance can be derived if you know the surface temperature and radius of the star. Together they give the intrinsic brightness. We know how bright the star appears to us. Knowing how right it SHOULD be instrinsically allows us to determine how far away it is — 560 light-years for Kepler-10.
Q: What are the prospects for additional planets in the Kepler 10 star system? Any hints?
Natalie: There is actually already a very compelling signature of another potential planet in this system. There is a transit event that recurs once every 45 days and is suggestive of a planet a bit larger than 2 times the radius of the Earth.
The Kepler Mission is a wonderful tool to unlocking our understanding of planets outside our own solar system. It’s an exciting time to be on the one known planet (so far!) that allows us to enjoy it.