The search for habitability elsewhere in space can probably be reduced to the search for water. We have not yet found life forms that separate this substance from our concept of “life” itself, so we have no choice but to accept the cosmic waterway as our north star in our quest to find worlds that mirror our own.
For this reason, scientists jump a little for joy when they find an exoplanet that is likely to hold any water at all—but especially liquid water, rather than ice or water vapor. And I hope at least one astronomer jumped for joy recently because a team of researchers just announced that an exciting planet outside Solar System it may have a temperate water ocean half the size of the Atlantic. Even better, the find is thanks The James Webb Space Telescope.
“Of all the currently known temperate exoplanets, LHS 1140 b could be our best bet to one day indirectly confirm liquid water on the surface of an alien world outside our solar system,” Charles Cadieux, lead author of the discovery paper and a PhD student at the Université de Montreal, he said in a statement. “This would be a significant milestone in the search for potentially habitable exoplanets.”
Dubbed LHS 1140 b exoplanet orbits a Red dwarf a star about one-fifth the size sun and sits 48 light years away from Earth in the constellation Cetus, which luckily means “whale”. But the most important thing about LHS 1140 b is the fact that it lives in its star’s habitable zone, otherwise known as its “Goldilocks zone.” As the moniker would suggest, this is a region around a star that is neither too hot nor too cold for the world to host liquid water, but rather meets the standard that the fairytale character Goldilocks lives by. The world also has a second great victory.
Related: A nearby exoplanet may be rich in life-giving water, study finds
“This is the first time we’ve ever seen a hint of an atmosphere on a habitable zone rocky or ice-rich exoplanet,” Ryan MacDonald, a NASA Sagan Fellow in the University of Michigan Department of Astronomy, who helped analyze the atmosphere of LHS 1140 b, said in a statement. According to Macdonald, the team may even have found evidence of “air” on it.
Regarding the previous part of this statement, you may notice that MacDonald suggests that the exoplanet could be rocky or icy. This brings us to a story.
LHS 1140 b lore
Although it’s now making headlines because of a new study involving JWST data, LHS 1140b has actually been on the radars of planet hunters for some time. In fact, experts have theorized in the past that it could be a water world, and even shared similar sentiments about how it could offer humanity the first ever direct evidence exoplanetary liquid water. None of this is new. Cadieux himself had previously held out the world’s promise, and an army of telescopes had explored it in solid detail, including the now-retired Spitzer Telescope, the so-called Hubble Space Telescope and the Transiting Exoplanet Survey Satellite (TESS).
But until now, something was missing: the keen eye of the James Webb Space Telescope.
This was necessary because there had long been something of a gap in the literature on LHS 1140b. Basically, the problem was that scientists couldn’t quite confirm whether the exoplanet was a mini-Neptune – a planet less massive than our original. Neptune, but one that still has Neptunian qualities – or super Earths. A super-Earth is a world that is larger than Earth but is still either rocky or rich in water. The latter usually sets off a “potential habitability” alarm, and JWST, scientists imagined, could be the one to set it off.
That seems to have been an accurate conclusion. As the team’s statement on the study suggests, their work not only “strongly rules out” the mini-Neptune scenario, but also confirms that the world may have a nitrogen-saturated atmosphere like Earth’s. “Although still a preliminary result, the presence of a nitrogen-rich atmosphere would indicate that the planet retained a substantial atmosphere and created conditions that could support liquid water,” he says.
It is certainly worth noting that the LHS 1140 b is not completely alone in its exciting features; there are also a number of other exoplanets in habitable zones that scientists are attracted to. The most obvious is probably the seven worlds TRAPPIST-1 system, a planetary system that looks almost disturbingly similar to the structure of our solar system. The septet of spheres resembles our octet (goodbye Pluto) and some of them are in the habitable zone like Earth.
However, a very interesting JWST study actually quite recently complicated the search for habitability in TRAPPIST-1. The system’s anchor star turns out to be incredibly active in a way that it could skew our observations that lead us to believe that the world in the system is habitable when in fact it is not. Even JWST has its limitations. For this purpose, the LHS 1140 b has several special decorations.
“The star LHS 1140 appears to be quieter and less active,” Macdonald assured, “making it significantly less challenging to separate the atmosphere of LHS 1140 b from the stellar signals caused by starspots.”
Get ready for even more specs
The excitement about the LHS 1140 b is quite contagious. There is so much to say about it.
For example, the JWST data further suggests that an exoplanet’s mass could be made up of 10% to 20% liquid water—painting a fantastic picture of what a planet might simply look like. It could essentially look like a snowball orbiting its star, rotating in such a way that one side always faces that star. It is something like the orbit of the moon around the earth; we can never see the other side Moon because the moon rotates at the same speed as it orbits the earth. One side never faces us and the other always does.
Similarly, this would mean that if the LHS 1140 bz JWST scene illustration is correct, the side of the planet always facing the sun would be exposed to a lot of heat. That would be the part of the snowball that “melted” into the liquid ocean.
Voila.
“Current models suggest that if LHS 1140b has an Earth-like atmosphere, it would be a snowball planet with a bull’s-eye ocean about 4,000 kilometers across.” [2,485 miles] on average,” it said in a statement, adding that the ocean’s surface temperature may very well be even a “comfortable” 20 degrees Celsius (68 degrees Fahrenheit).
Unfortunately, while the team assures that much more work needs to be done, especially with JWST, in observing the nuances of LHS 1140 b – it’s always nice to have a lead to follow when looking for needles in a huge haystack. And as MacDonald says, “this is a very promising start.”
A preprint version of the study is available on arXiv.