Many astrophysicists are focused on what makes a planet habitable.
We know a good deal about why our own has been such a supportive host for life, but we’re still discovering new aspects of how those particular circumstances came to be.
Now, exoplanet Phoenix is shaking things up, revealing that there could be other ways for a planet to hold onto its atmosphere than previously believed.
The planet, officially called TIC265102760, is smaller, hotter, and older than anyone expected for its class. It’s also lightly larger than Earth, more in the category of Neptune.
This is a big deal, considering Phoenix is six times closer to its sun than Mercury is to ours – and its sun is hotter, classified as a red giant.
This what our sun will one day evolve into, a move that until now, was thought to be the beginning of the end for the habitability of Earth.
The temperature and the relentless stream of particles should have stripped the atmosphere long ago, and scientists like Sam Grunblatt, who was the lead author on the current paper, are keen to find out what makes it the exception.
“This planet isn’t evolving the way we thought it would, it appears to have a much bigger, less dense atmosphere than we expected for these systems. How is held on to that atmosphere despite being so close to such a large host star is a big question.”
There are other “hot Neptunes” out there, but Phoenix isn’t like any of them.
“It’s the smallest planet we’ve ever found around one of these red giants, and probably the lowest mass planet orbiting a red giant star we’ve ever seen. That’s why it looks really weird. We don’t know why it still has an atmosphere when other ‘hot Neptunes’ that are much smaller and much denser seem to be losing their atmospheres in much less extreme environments.”
Don’t get us wrong, Phoenix’s atmosphere is being stripped, but so slowly that it will probably survive the death of the planet.
As stars grow and grow, becoming red giants, they affect the orbits of the planets nearest to them, the closest of which will spiral inward and be destroyed.
This is likely the fate of Phoenix around 100 million years from now – and of Earth, too, 5 billion years in the future.
These observations, though, suggest we don’t know for sure how our home planet will get from point A to point B.
“We don’t understand the late-stage evolution of planetary systems very well. This is telling us that maybe Earth’s atmosphere won’t evolve exactly how we thought it would.”
Realizing that there is so much more to learn is what scientists truly love about their work.
Space truly is the last frontier, and there’s no doubt that more questions than answers remain out there.
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