First Earth-like exoplanet with discernable atmospheric conditions found

March 4, 2021

A new telescope will have an exciting new exoplanet to study. (Jose Caballero and Javier Bollain)

NASA’s James Webb Space Telescope promises to permanently alter knowledge of the universe, and in time for its launch this year, scientists working with the space agency have located a terrific candidate for observation: The first Earth-like exoplanet with detectable atmospheric conditions.

After surveying about 350 small red dwarf stars for signs of orbiting low-mass planets, the team of astronomers came across the exoplanet Gliese 486b. Its name is derived from the bright star it orbits, Gliese 486. This rocky planet is the first of its kind found to have the ideal conditions for atmospheric measurements, and details of the the discovery were published March 4 in Science. 

“Gliese 486b is likely to become the ‘rosetta stone’ for atmospheric investigations of rocky exoplanets,” said the lead author of the paper, Trifon Trifonov, referencing the etchings that first unlocked hieroglyphics.

The understanding of an Earth-like exoplanet’s atmosphere — or lack thereof — will help scientists map the universe more accurately, potentially increasing the likelihood of finding life on other exoplanets outside the solar system, or even locating one inside the habitable zone.

Trifonov, a postdoctoral researcher at the Max Planck Institute for Astronomy in Germany, describes the newly discovered exoplanet as a combination of Earth and Venus. Because it’s closer in temperature to the latter, at about 700 K, it isn’t habitable for humans. But in a silver lining, the Venus-like temperature makes it ideal for emission spectroscopy, which is used in atmospheric studies.

“Its correspondingly higher planetary equilibrium temperature makes Gliese 486b suitable for emission spectroscopy and phase curve studies to search for an atmosphere," Trifonov told The Academic Times. "It makes it an exceptional discovery." 

He added, “The proximity and the combination of physical and orbital characteristics of the planet are the most favorable for detecting an exoplanet atmosphere, around an Earth-sized planet, especially with the upcoming James Webb Space Telescope."

About half the size of a Boeing 737 airplane and foldable origami style, the James Webb Space Telescope, or JWST, will be 100 times more powerful than the Hubble Space Telescope, NASA's pioneering telescope for space exploration. It can access information in the universe from 13.5 billion years ago, right after the Big Bang, and is so sensitive that it can “detect the heat signature of a bumblebee at the distance of the moon.” Most important for Gliese 486b, it can thoroughly dissect exoplanet atmospheres.

Gliese 486b exhibits a mass that is 2.8 times that of Earth, even though it is only about 30% larger. Its position from Earth is only 26 light-years away, as opposed to the majority of exoplanets that are hundreds of thousands of light-years away. 

It boasts a reasonable orbital period and directly faces the star around which it rotates, like the moon faces the Earth. Its route even periodically crosses NASA’s Transiting Exoplanet Survey Satellite, TESS, a rarity. 

Evidently, Gliese 486b meets an overwhelming number of requirements for easy observation.

“The orbital period was only 1.47 days, which allowed us to recover its orbital parameters with great accuracy, and the proximity of Gliese 486b allowed us to measure its mass with unprecedented precision, thanks to observations done with the CARMENES and the MAROON-X instruments,” Trifonov said.

The team used the Doppler spectroscopy method to study the star that the exoplanet orbits, calling the famous instrument CARMENES its "primary weapon." This telescope is able to measure the velocity of stars with extreme precision. 

Doppler spectroscopy, colloquially called the wobble method, indirectly finds exoplanets around stars by noting changes in a targeted star’s velocity over time. Changes indicate planetary companions, like Gliese 486b is to Gliese 486.

“The CARMENES provides state-of-the-art Doppler radial velocity precision of the order of 1 meter per second,” Trifonov said. “Imagine — we can measure the velocity of stars with the velocity-precision of an average human walking.”

He continued, “We immediately realized that the combination of precise Doppler and transit data will make this discovery of extreme scientific value, which was very exciting."

Trifonov and his team zeroed in on red dwarf stars, such as Gliese 486, because they are abundant, small and low in mass, making their exoplanets more accessible. Going forward, he says that Gliese 486 will be observed by the European CHEOPS space telescope mission, and that its associated exoplanet will likely soon be a subject of NASA's breakthrough telescope. 

“Our best chance is JWST. Soon after it becomes operational, we may plan observations of Gliese 486b,” Trifonov said. “Best case, it will be a year from now.”

The paper, “A nearby transiting rocky exoplanet that is suitable for atmospheric investigation,” was published March 4 in Science. It was authored by T. Trifonov, Th. Henning, D. Kossakowski and M. Kürster, Max-Planck-Institut für Astronomie; J. A. Caballero, M. Cortés-Contreras, J. Sanz-Forcada and C. Cifuentes, Instituto Nacional de Técnica Aeroespacial; J. C. Morales, M. Lafarga, I. Ribas, E. Herrero and G. Anglada-Escudé, Institut de Ciències de l’Espai; A. Seifahrt, J. L. Bean and D. Kasper, University of Chicago; A. Reiners, S. Dreizler, S. V. Jeffers and M. Zechmeister, Georg-August-Universität; R. Luque, M. Stangret, M. Oshagh, N. Narita, N. Casasayas-Barris, A. Fukui, E. Esparza-Borges, V. J. S. Béjar, H. Parviainen, E. Pallé and F. Murgas, Instituto de Astrofísica de Canarias; S. Stock, K. Molaverdikhani, J. Stürmer, A. Kaminski, A. Quirrenbach and P. Bluhm, Universität Heidelberg; P. J. Amado and C. Rodríguez López, Instituto de Astrofísica de Andalucía; M. Azzaro, Observatorio de Calar Alto; T. Barclay, NASA Goddard Space Flight Center; K. A. Collins, S. N. Quinn and D. W. Latham, Harvard & Smithsonian; K. I. Collins, George Mason University; J. de Leon, University of Tokyo; C. D. Dressing, University of California at Berkeley; N. Espinoza, Space Telescope Science Institute; M. Fausnaugh, R. Vanderspek, P. Tenenbaum, A. Shporer, S. Seager and G. R. Ricker, Massachusetts Institute of Technology; A. P. Hatzes, Thüringer Landessternwarte Tautenburg; C. Hellier, Keele University; C. E. Henze, J. D. Twicken and J. M. Jenkins, NASA Ames Research Center; E. L. N. Jensen, Swarthmore College; A. W. Mann, University of North Carolina at Chapel Hill; D. Montes, Departamento de Física de la Tierra y Astrofísica and Instituto de Física de Partículas y del Cosmos; B. T. Montet, University of New South Wales; V. M. Passegger and A. Schweitzer, Universität Hamburg; D. Pollacco, University of Warwick; R. P. Schwarz, Patashnick Voorheesville Observatory; T. G. Tan, Perth Exoplanet Survey Telescope and J. N. Winn, Princeton University.

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