Potentially habitable planets found in supercool solar system
The interstellar real estate market may have more options than we’d previously considered, as demonstrated by three new, rocky exoplanets recently discovered 40 light years away. They orbit a supercool red dwarf star called TRAPPIST-1, where astronomers had once thought that no such planets would even exist around such a small star. There’s a lot of excitement about this, not only because of the possibilities it raises for other dwarf solar systems, but also because rocky planets are on our checklist for places that might sustain life. That said, these three planets are probably a bit on the “fixer-upper” side of things, so maybe hold off on packing your bags for a while longer.
The upside of these three planets is that they’re all around the size of the Earth, which is the first clue about their composition. We’ve identified tons of exoplanets across the galaxy, but larger objects are likely to be gas giants like Saturn or Jupiter, potentially without much structure for life to get started on. The second piece of good news is that the third planet from this Jupiter-sized sun is possibly far enough out to be in what’s known as the ‘habitable zone,’ where temperatures might allow for water to exist as a liquid, another thing life as we know it seems to enjoy. Even if it’s not in that sweet spot, it might be able to carry liquid water under an outer frozen shell, a model we’ve seen closer to home in the the moon Enceladus.
Short years, never ending night
Now, none of these planets are likely ‘move-in ready,’ but it’s nothing too difficult. The first two planets might be a bit too close to TRAPPIST-1, forcing them to be tidally-locked to the star. This means that these planets have no day and night, as one side of the planet always faces the sun, and the other always faces the dark of space, similar to how Earth’s Moon always shows us the same side. What the planets lack in day and night is made up for in years though, as they complete orbit around their tiny star in just 1.5 and 2.4 Earth days. Let’s move on?
Passable, but not necessarily pleasant
TRAPPIST-1d, the planet most likely to support life, would probably require some very different forms of life. Aside from an orbit no more than 73 Earth days long, the bigger issue of this planet for life is actually the light from the TRAPPIST-1 start itself. The energy emitted from this “supercool” star doesn’t extend past red light, so no organisms would be sensitive to yellows or blues, meaning any alien plant would likely be red, not green. To our eyes, it would all be reds and blacks, as much of the energy available would be in the infrared portion of the electromagnetic spectrum. Again, it’s a great new neighborhood, but a planet with under an ice dome that’s bathed in nothing but red 73 days out of the year might not be for everyone.
Source: New Earth-Size Planets Would Be Nothing Like Earth by Nadia Drake, National Geographic