A new year arrives every 47.5 hours on exoplanet TOI 674b, roughly the size of Neptune, making it something of a rare creature.
Despite years of hunting, surprisingly few medium-sized gas giants with orbits shorter than a few days have been seen creating what astronomers call the Neptunian desert of incredibly hot, star-slicing intermediate-mass planets.
Why this is so is a bit of a mystery. Eventually, several Earth-sized rock balls (such as the hot TOI 270b) fly around their star. Hot Jupiters also appear regularly, with orbits measured by clocks.
So where are all the hot Neptunes? Something about their size, composition, or location in their solar system makes them much less likely to get too personal with a nearby star. Or, on rare occasions, they don’t stick around long enough to brag about it.
Fortunately, astronomers have noticed something else unusual about this newly discovered mid-range giant, a discovery that may help us explain why it’s so special: there are hints of water in its atmosphere.
Observing water on planets far from our own oceanic world is interesting for a number of reasons, not least because it allows us to understand how unique our own planet can be.
But having a breakdown of the types of gases in an exoplanet’s atmosphere, especially water vapor, is like having the details of her cosmic birth certificate, giving planetary scientists a clearer picture of how and where she formed in her solar system.
Planets that form beyond the point where the star’s radiation can easily sublimate ice into gas will have a much better chance of surviving on water, such as a short-orbit Neptune with plenty of water more likely to be far from its birthplace. .
The next step will be to collect more data on the exact amount of water in TOI 674b’s atmosphere, as well as other characteristics such as its metallicity.
The planet was on our radar for only about a year after it was discovered using data from NASA’s Transiting Exoplanet Survey Satellite. But researchers have already found it interesting enough to send other instruments, such as the Hubble Space Telescope, to the planet to explore its secrets. (The team also looked at older data from the former Spitzer Space Telescope.)
At about half the mass of our Sun, the M-class red dwarf it orbits isn’t particularly bright, meaning there’s enough light to see, but the planet doesn’t get lost in the bright light as much. What’s more, at only 150 light-years away, the entire planetary system is more or less in our backyard.
This triple proximity to the parent star, close to us, and soft radiation means it will be much easier for current generation spectrographs to analyze the light flickering through its clouds.
One instrument ideal for studying exoplanets is the recently launched James Webb Space Telescope, whose design will give us an unparalleled view of distant stars and their planets.
Knowing how TOI 674b got into such a heated embrace with its star will help us fill in the bigger picture of how other solar systems evolve, and whether our own is a dull normal or a unique gem in an ocean of chaos.
Preprint available on arXiv and submitted Astrophysical Journal.