The search for habitability elsewhere in the universe may well be reduced to the search for water. We have not yet found life forms that would decouple this substance from our concept of “life” itself, so we have no choice but to accept the cosmic water trail as our pole star in the search for worlds that mirror our own.
For this reason, scientists jump a little for joy when they find an exoplanet that likely has water at all — specifically, liquid water, rather than ice or water vapor. And I hope at least one astronomer has been jumping for joy somewhere recently, as a team of researchers has just announced the discovery of a tantalizing planet beyond the solar system could have a temperate ocean about half the size of the Atlantic. Better yet, the discovery is due to the James Webb Space Telescope.
“Of all the currently known temperate exoplanets, LHS 1140 b may represent our best chance to one day indirectly confirm liquid water on the surface of an alien world outside our solar system,” said Charles Cadieux, lead author of a paper on the discovery and a doctoral student at the Université de Montréal. said in a statement“This would be an important milestone in the search for potentially habitable exoplanets.”
The LHS 1140 b, the exoplanet revolves around a red dwarf star about one-fifth the size of the sun and sits 48 light years away from Soil in the constellation Cetus, which, as fate would have it, translates to “the whale.” But the most important thing about LHS 1140 b is the fact that it lives in its star’s habitable zone, also known as its “Goldilocks zone.” As the nickname suggests, this is the region around a star where it’s neither too hot nor too cold for a world to harbor liquid water, but rather meets the standards set by the fairy-tale character Goldilocks. There’s also a second big win for the world.
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“This is the first time we’ve seen any trace of an atmosphere on a planet. habitable zone rocky or ice-rich exoplanet,” said Ryan MacDonald, a NASA Sagan Fellow of the University of Michigan’s Department of Astronomy, who helped analyze LHS 1140 b’s atmosphere, said in the statement. According to Macdonald, the team may even have found evidence of “air” on it.
As for the first part of that statement, you may notice that MacDonald suggests that the exoplanet could be rocky or icy. This brings us to a backstory.
LHS 1140 b-tradition
Although it is now in the news because of the new study using JWST data, LHS 1140 b has been on the radar of planetary hunters for a while. In fact, experts have suggested in the past that it could be a water world, and they have even shared similar sentiments about how it could provide humanity with the very first direct evidence of exoplanetary liquid water. None of this is new. Cadieux himself has previously touted the promise of the world, and an army of telescopes has explored it in detail, including the now-retired Spitzer telescope, the Hubble Space Telescope and the Transiting Exoplanet Survey Satellite (TESS).
But until now, something has been missing: the sharp eye of the James Webb Space Telescope.
It was necessary because there was something of a gap in the literature about LHS 1140 b for a long time. The problem was that scientists could not fully confirm whether the exoplanet is a mini-Neptune — a planet that is less massive than our original Neptunebut one that still has Neptunian characteristics — or a super-Earth. A super-Earth is a world that is larger than Earth but still rocky or watery. The latter usually sounds the alarm for “potential habitability,” and the JWST, scientists had imagined, might be the one to sound the alarm.
This seems to have been a correct conclusion. As the team’s statement on the study suggests, their work not only “strongly ruled out” the mini-Neptune scenario, but also confirmed that the world may have a nitrogen-rich atmosphere like Earth. “Although still only a preliminary result, the presence of a nitrogen-rich atmosphere would suggest that the planet has retained a substantial atmosphere, creating conditions that could support liquid water,” the report said.
It is certainly worth noting that LHS 1140 b is not entirely alone in its exciting properties; there are also a variety of other exoplanets in the habitable zone that scientists are attracted to. The most obvious are probably the seven worlds of the TRAPPIST-1 system, a planetary arrangement that is almost disturbingly similar to the structure of our solar system. The septet of orbs resembles our octet (day, Pluto) and some of them are in the habitable zone, just like Earth.
However, a very interesting JWST study recently complicated the search for habitability in TRAPPIST-1. It revealed that the system’s anchor star is so incredibly active that it crooked our observations, which lead us to believe that a world in the system is habitable, when in fact it is not. Even the JWST has its limitations. So, for that reason, LHS 1140 b has some special decorations.
“The star LHS 1140 appears to be calmer and less active,” Macdonald assured, “making it much easier to distinguish the atmosphere of LHS 1140 b from stellar signals caused by starspots.”
Get ready for even more specs
The excitement about LHS 1140 b is quite infectious. There is so much to say about it.
For example, the JWST data further suggests that the exoplanet’s mass could be 10 to 20 percent liquid water — and it paints a fantastic picture of what the planet might look like in simple terms. It would essentially look like a snowball orbiting its star while rotating in such a way that one side always faces that star. It’s a bit like the moon’s orbit around the Earth; we can never see the backside of the moon because the moon rotates at the same speed as the earth. One side never faces us, and the other side always does.
Likewise, if the JWST illustration of the LHS 1140 b scene is correct, this would mean that the side of the planet that always faces the Sun would be exposed to a lot of heat. This would be the part of the snowball that is “melted” into a liquid ocean.
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Voila.
“Current models indicate that if LHS 1140 b has an atmosphere similar to Earth’s, it would be a snowball planet with an ocean located about 4,000 kilometers away [2,485 miles] in diameter,” the statement said, adding that the temperature at the ocean’s surface could be a “comfortable” 20 degrees Celsius (68 degrees Fahrenheit).
Alas, while the team assures that much more work needs to be done, particularly with the JWST, to observe the nuances of LHS 1140 b — it’s always nice to have a trail to follow when looking for needles in a giant haystack. And, as MacDonald puts it, “this is a promising start.”
A pre-print version of the study can be viewed on arXiv.