Astronomers have detected traces of helium in the atmosphere of LHS 1140 b, a rocky exoplanet about 49 light-years away that orbits a dim red dwarf star, in a finding published Friday in the journal Science that researchers say is still tentative. The planet sits far beyond the reach of ordinary people, but the machinery of science keeps sorting the universe into what can be known, what can be funded, and what gets called a breakthrough.
Who Gets to Look
Collin Cherubim, who led the study while at Harvard University, said: "This [planet] is the best place currently to look for life outside of our Solar System because it has all the main ingredients that we think are essential for life." He also said: "I hope this is just the first [discovery] of many to come." Cherubim said LHS 1140 b is "mostly rocky," that scientists think it is the right temperature to have liquid water, and that it "just happens to be really nearby, relatively." He said it orbits "a star that's very old and quiet" and that it has "never been seen to flare ... which are all really good things for habitability."
That language matters. The people with access to the telescopes, the models, and the time get to define what counts as a promising world. Everyone else gets the press release version, polished by institutions that decide which mysteries are worth chasing and which are left to rot in obscurity.
LHS 1140 b was first discovered in 2017. Scientists had previously used the James Webb Space Telescope to look for signs of different chemicals around rocky planets including LHS 1140 b, but those observations were inconclusive. Cherubim and his colleagues instead used a relatively new technique and ground-based telescopes to look directly for the specific fingerprint of helium escaping an atmosphere. Helium can be found much farther away from a planet than some other atmospheric gases, which makes it easier to detect. The technique has mostly been used on large, gassy planets because it was assumed smaller planets would not show the same telltale signature.
What They Missed Before
Cherubim said: "Nobody bothered looking for helium on a rocky, Earth-like planet, especially at Earth-like temperatures as well." He said: "People thought it would be a waste of time because you wouldn't expect a lot of hydrogen or helium ... because they're such light gases that can evaporate to space over time." He said the team had developed a model of how planetary atmospheres evolve over long time frames, especially atmospheres with high levels of helium, and that LHS 1140 b had "a relatively high probability of having this helium-dominated atmosphere." Cherubim said: "And that target jumped out at me because it's a rocky planet, it's in the habitable zone. It would be crazy if it had a helium-dominated atmosphere." When the team looked, he said, "Lo and behold, there it was."
The whole thing reads like a reminder that even in astronomy, the gatekeepers set the terms. If a target doesn't fit the assumptions, it gets passed over. If the model says it's unlikely, the search stops. Then, when the right team with the right tools finally looks, the result gets framed as discovery rather than a correction to the narrowness of the original search.
The study suggests LHS 1140 b could potentially be a water world. The planet is a bit larger than Earth and has five times Earth’s mass. It sits within its star’s Goldilocks zone, the region with temperatures that can support water on a planet’s surface. Atmospheres are thought to be vital to life on rocky exoplanets because they can provide a more stable climate, protect a planet from radiation and trap water.
What the Models Say
Tom Evans-Soma, an astronomer at the University of Newcastle who specialises in exoplanets and was not involved in the research, said the signal looked convincing and called it "very exciting." He said he had been part of an international team that made the first-ever detection of helium in the air of an alien world, though not a rocky Earth-like one. Evans-Soma said: "All of the rocky planets that had hints of atmospheres detected so far have been much hotter and less hospitable planets." He noted that the signal from LHS 1140 b was detected once and not found in a second observation, but said that was not unusual for helium.
Evans-Soma said the modelling by Cherubim and the team suggested two possible versions of the planet: one with a low amount of water and a thick atmosphere, and one with significantly more water than Earth. He said: "[The model] seems to favour this water world scenario where you've got a mostly Earth-like rocky composition plus 10 per cent water by mass." He added: "And I think that's very exciting — to imagine what such a planet might be like, especially in the habitable zone, where that water could be in the liquid form on the surface of the planet." The model suggested that, along with a large amount of helium, the planet might have water vapour, carbon dioxide, carbon monoxide and small amounts of oxygen.
Cherubim and Evans-Soma both said more research was needed to confirm what type of atmosphere the planet has. Cherubim said: "It's still a bit tentative." He said: "It's not like a smoking gun that it's a helium-dominated atmosphere, but it's consistent with the prediction." He also said he planned to look for helium signatures in other planets that lie within their star's habitable zone. "I have already been awarded time on the same [telescope] to observe a planet that's like a LHS 1140 b twin," he said. "It's a very similar star that it's orbiting, it's a very similar size, it's a little bit smaller." He said: "That one I'm really excited about."
The result may be tentative, but the hierarchy behind it is not. Telescope time gets awarded. Models get built. Assumptions decide what gets searched. Then the institutions call it progress and move on to the next target, while the rest of the world is left watching from outside the control room.