New measurements by the James Webb Space Telescope found that a rocky exoplanet orbiting a star known as TRAPPIST-1 most likely has no atmosphere.
The finding squashes hopes that this intriguing world might host life. But don't despair — there are six more Earth-like exoplanets in the TRAPPIST-1 star system, and now that Webb has proven its ability to study them, we can hope for some more exciting news in the not so distant future.
Astronomers used the James Webb Space Telescope's Mid-Infrared Instrument (MIRI) to measure the temperature of the planet TRAPPIST-1b. Out of the seven planets that make up the TRAPPIST-1 star system, this planet orbits the closest to the parent star and is about 1.4 times as large as Earth.
Related: Webb meets the 7 intriguing exoplanets of TRAPPIST-1
The measurement, which according to the European Space Agency (ESA) represents Webb's first detection of "any form of light" emitted by a rocky exoplanet, revealed that the planet's daytime temperature was a scorching 446 degrees Fahrenheit (230 degrees Celsius). Astronomers think that's too high for the planet to have an atmosphere.
Thomas Greene, an astrophysicist in the Space Science and Astrobiology Division at NASA's Ames Research Center in California who led the observations, told Space.com in an email that he had hoped for a different result.
"Some theory groups predicted that the planet would have a dense atmosphere, while others thought it might not," Greene said. "I was more disappointed than surprised to see it had no atmosphere."
The distance between TRAPPIST-1b and its star is only about one hundredth of the sun-Earth distance. That's 40 times closer than the distance between the sun and the solar system's innermost planet Mercury.
Although the star at the center of the TRAPPIST-1 system is much dimmer than our sun, the planet still receives about four times as much starlight as Earth receives from the sun. Astronomers therefore didn't expect this planet to be habitable prior to ruling out the presence of an atmosphere. The observation, however, is still a breakthrough, as it shows that Webb can directly gather information about such distant Earth-like worlds.
In the TRAPPIST-1 system, there are at least three planets — TRAPPIST-1e, 1f and 1g — that have conditions for the existence of liquid water on their surfaces and therefore might host life.
The TRAPPIST-1 system is a hugely popular target for exoplanet research and the best explored planetary system other than our own solar system, according to NASA. Located some 40 light-years away from the sun, the star at the center of the TRAPPIST-1 system is a so-called M dwarf. Sometimes also referred to as red dwarfs, these stars are the smallest known type of stars capable of burning hydrogen in their cores. They range in size from 0.08 to 0.6 times the size of the sun and are the most numerous type of star in our galaxy, the Milky Way.
"There are about ten times as many M stars like TRAPPIST-1 than G stars like the sun," Greene wrote. "M stars are also about twice as likely to have rocky, Earth-sized planets. Therefore about 95% of the Earth-sized rocky planets in the Milky Way will have stars like TRAPPIST-1 and not like the sun."
For this reason, the TRAPPIST-1 star system is an important testbed that could help astronomers better understand where best conditions for life exist.
Previous observations with the Hubble Space Telescope and the now retired Spitzer Space Telescope found no traces of atmospheres on any of the TRAPPIST-1 planets. However, Greene said, a possibility still exists that a very thin atmosphere surrounds TRAPPIST-1b, one that might be completely different from the atmospheres shrouding planets in the solar system.
"We have some follow-up observations scheduled in June at another wavelength and have proposed observing a bigger part of the planet's orbit to look into and maybe rule out some other types of atmospheres," Greene said.
The study was published in the journal Nature on Monday, March 27.
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The exoplanet atmosphere site shows TRAPPIST-1 b too. http://research.iac.es/proyecto/exoatmospheres/view.php?name=TRAPPIST-1%20b.
This is not the first report of an exoplanet indicating no atmosphere observed. GJ 1252 b, Discovery could dramatically narrow search for space creatures, https://phys.org/news/2022-10-discovery-narrow-space-creatures.html
Are planets with oceans common in the galaxy? It's likely, NASA scientists find, https://phys.org/news/2020-06-planets-oceans-common-galaxy-nasa.html, "...When Webb launches, scientists will try to detect chemical signatures in the atmospheres of some of the planets in the TRAPPIST-1 system, which is 39 light years away in the constellation Aquarius. In 2017, astronomers announced that this system has seven Earth-size planets. Some have suggested that some of these planets could be watery, and Quick's estimates support this idea. According to her team's calculations, TRAPPIST-1 e, f, g and h could be ocean worlds, which would put them among the 14 ocean worlds the scientists identified in this study."
Do the TRAPPIST-1 planets have atmospheres?, https://phys.org/news/2020-07-trappist-planets-atmospheres.html
A review of possible planetary atmospheres in the TRAPPIST-1 system, https://arxiv.org/abs/2007.03334, 07-July-2020. “TRAPPIST-1 is a fantastic nearby (~39.14 light years) planetary system made of at least seven transiting terrestrial-size, terrestrial-mass planets all receiving a moderate amount of irradiation. To date, this is the most observationally favourable system of potentially habitable planets."
Much hope is in the galaxy (looking for habitable exoplanets) because of TRAPPIST-1 exoplanet system. Much remains to be confirmed and shown true about those exoplanets as well.
Trappist-1e seems favorable, though it didn't make the list using the atmospheric method.
James Webb Space Telescope confirms giant planet atmospheres vary widely, https://phys.org/news/2023-03-james-webb-space-telescope-giant.html
Ref - High atmospheric metal enrichment for a Saturn-mass planet, https://www.nature.com/articles/s41586-023-05984-y, 27-March-2023.
It remains to be seen just how many *rocky* exoplanets have no atmospheres, and how many gas giant exoplanets depart from the solar system model standard. As the phys.org report concludes: "While an abundance of carbon might seem favorable for chances of life, a high carbon to oxygen ratio actually means less water on a planet or in a planetary system—a problem for life as we know it. Smertrios is an interesting first case of atmospheric composition for this particular study, said Lunine, who has plans in place to observe five more giant exoplanets in the coming year using JWST. Many more observations are needed before astronomers can discover any patterns among giant planets or in systems with multiple giant planets or terrestrial planets to the compositional diversity astronomers are beginning to document. "The origin of this diversity is a fundamental mystery in our understanding of planet formation," Bean said. "Our hope is that further atmospheric observations of extrasolar planets with JWST will quantify this diversity better and yield constraints on more complex trends that might exist."
Webb measures temperature of rocky exoplanet for first time, https://phys.org/news/2023-03-webb-temperature-rocky-exoplanet.html
ref - Thermal Emission from the Earth-sized Exoplanet TRAPPIST-1 b using JWST, https://www.nature.com/articles/s41586-023-05951-7, 27-March-2023.
My note. http://exoplanet.eu/catalog/trappist-1_b/, shows the measured temperature is 503 K citing Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST, https://arxiv.org/abs/2303.14849, 26-March-2023. The calculated temperature was 400 K so JWST increased the exoplanet temperature by 100 K. This site still reports 400 K, JWST has changed this view of TRAPPIST-1 b exoplanet. http://research.iac.es/proyecto/exoatmospheres/view.php?name=TRAPPIST-1%20b
In the very distant future, our "descendants" (for certain values of the word) could still explore the length and breadth of the Milky Way, but they will either be purely mechanical embodiments of artificial general intelligence ... or genetically engineered organisms capable of withstanding millenniae of interstellar travel. If the latter, my money is on cognitively enhanced tardigrades. These tiny animals (please don't call them ugly!) are already famed today for resilience and longevity in the harshest conditions including airlessness, radioactivity and cold. Perhaps a smattering of human DNA will be preserved in the genome of the tardigrades-plus (for sentimental reasons).
Tardigrades survive impacts of up to 825 meters per second, https://phys.org/news/2021-05-tardigrades-survive-impacts-meters.html
"To find out, the research pair obtained 20 tardigrade specimens and put them in a deep freeze to induce their sleep-like state. They then placed them in groups of two or three into thin cylinders filled with water. The cylinders were then placed inside of a larger cylinder that served as an ammunition shell for a two-stage light gas gun. The gun was placed inside of a vacuum chamber where its shell was fired at a target made of sand. Shots were fired from the gun at different speeds to see what impact each would have on the passenger tardigrades. The researchers found that the tardigrades shot from the gun at speeds up to 825 meters per second could be resuscitated after removal from the cylinder. Those experiencing higher-speed impacts were torn apart and did not survive. The researchers suggest that tardigrades would likely not survive an impact with a planet if they traveled across space on an asteroid (as some have suggested), as such impacts tend to be at higher speeds than the tardigrades could tolerate."
My observation. This is a blow to panspermia thinking and life transferring around to other planets via asteroid and meteor impacts. Velocities and kinetic energy too high for survival of tardigrades.
The methods used to calculate temperatures for planets is subject to how accurate the input data is. The equilibrium temp. method, for example, assumes a bond albedo of 0.3 for the planet, which is just a guess. A lower albedo would make the planet more likely to be hotter.
Another method uses the radius of the star, which can't be determined to great accuracy since most stars can't even be seen as anything other than a tiny point.
For this reason, I like to show where in the HZ a planet is calculated to be, thus one can play with the probability a little better when knowing if it's in the middle of the zone or on the edge.