Il Kitt Peak Telescope del National Observatory aiuta a determinarlo[{” attribute=””>Jupiter-like Planet is the lowest-density gas giant ever detected around a red dwarf.
A gas giant exoplanet with the density of a marshmallow has been detected in orbit around a cool red dwarf star. A suite of astronomical instruments was used to make the observations, including the NASA-funded NEID radial-velocity instrument on the WIYN 3.5-meter Telescope at Kitt Peak National Observatory, a Program of NSF’s NOIRLab. Named TOI-3757 b, the exoplanet is the fluffiest gas giant planet ever discovered around this type of star.
Using the WIYN 3.5-meter Telescope at Kitt Peak National Observatory in Arizona, astronomers have observed an unusual Jupiter-like planet in orbit around a cool red dwarf star. Located in the constellation of Auriga the Charioteer around 580 light-years from Earth, this planet, identified as TOI-3757 b, is the lowest-density planet ever detected around a red dwarf star and is estimated to have an average density akin to that of a marshmallow.
Red dwarf stars are the smallest and dimmest members of so-called main-sequence stars — stars that convert hydrogen into helium in their cores at a steady rate. Although they are “cool” compared to stars like our Sun, red dwarf stars can be extremely active and erupt with powerful flares. This can strip orbiting planets of their atmospheres, making this star system a seemingly inhospitable location to form such a gossamer planet.
Shubham Kanodia, ricercatore presso il Carnegie Institution for Science’s Earth and Planetary Laboratory e primo autore di un articolo pubblicato su Viaggio astrologicoa. Finora questo è stato visto solo da piccoli campioni di indagini Doppler, che di solito hanno trovato pianeti giganti lontani da queste stelle nane rosse. Finora non abbiamo avuto un campione sufficientemente ampio di pianeti per trovare pianeti gassosi vicini in modo robusto”.
Ci sono ancora misteri inspiegabili che circondano TOI-3757 b, primo fra tutti come potrebbe formarsi un pianeta gigante gassoso attorno a una stella nana rossa, in particolare un pianeta a bassa densità. Tuttavia, il team di Kanodia crede di poter avere una soluzione a questo mistero.
Suggeriscono che la densità estremamente bassa di TOI-3757 b potrebbe essere il risultato di due fattori. Il primo riguarda il nucleo roccioso del pianeta; Si pensa che i giganti gassosi inizino come enormi nuclei rocciosi con una massa circa dieci volte la massa della Terra, a quel punto attingono rapidamente grandi quantità di gas nelle vicinanze per formare i giganti gassosi che vediamo oggi. TOI-3757b ha un’abbondanza di elementi pesanti inferiore rispetto ad altre nane M con giganti gassosi, e ciò potrebbe aver portato alla formazione del nucleo roccioso più lentamente, ritardando l’inizio dell’accumulo di gas e influenzando così la densità complessiva del pianeta.
Un secondo fattore potrebbe essere l’orbita del pianeta, che si pensa sia leggermente ellittica. Ci sono momenti in cui si avvicina alla sua stella rispetto ad altre volte, provocando un notevole riscaldamento in eccesso che può far gonfiare l’atmosfera del pianeta.
Satellite in transito della NASA per l’indagine sugli esopianeti ([{” attribute=””>TESS) initially spotted the planet. Kanodia’s team then made follow-up observations using ground-based instruments, including NEID and NESSI (NN-EXPLORE Exoplanet Stellar Speckle Imager), both housed at the WIYN 3.5-meter Telescope; the Habitable-zone Planet Finder (HPF) on the Hobby-Eberly Telescope; and the Red Buttes Observatory (RBO) in Wyoming.
TESS surveyed the crossing of this planet TOI-3757 b in front of its star, which allowed astronomers to calculate the planet’s diameter to be about 150,000 kilometers (100,000 miles) or about just slightly larger than that of Jupiter. The planet finishes one complete orbit around its host star in just 3.5 days, 25 times less than the closest planet in our Solar System — Mercury — which takes about 88 days to do so.
The astronomers then used NEID and HPF to measure the star’s apparent motion along the line of sight, also known as its radial velocity. These measurements provided the planet’s mass, which was calculated to be about one-quarter that of Jupiter, or about 85 times the mass of the Earth. Knowing the size and the mass allowed Kanodia’s team to calculate TOI-3757 b’s average density as being 0.27 grams per cubic centimeter (about 17 grams per cubic feet), which would make it less than half the density of Saturn (the lowest-density planet in the Solar System), about one quarter the density of water (meaning it would float if placed in a giant bathtub filled with water), or in fact, similar in density to a marshmallow.
“Potential future observations of the atmosphere of this planet using NASA’s new James Webb Space Telescope could help shed light on its puffy nature,” says Jessica Libby-Roberts, a postdoctoral researcher at Pennsylvania State University and the second author on this paper.
“Finding more such systems with giant planets — which were once theorized to be extremely rare around red dwarfs — is part of our goal to understand how planets form,” says Kanodia.
The discovery highlights the importance of NEID in its ability to confirm some of the candidate exoplanets currently being discovered by NASA’s TESS mission, providing important targets for the new James Webb Space Telescope (JWST) to follow up on and begin characterizing their atmospheres. This will in turn inform astronomers what the planets are made of and how they formed and, for potentially habitable rocky worlds, whether they might be able to support life.
Reference: “TOI-3757 b: A low-density gas giant orbiting a solar-metallicity M dwarf” by Shubham Kanodia, Jessica Libby-Roberts, Caleb I. Cañas, Joe P. Ninan, Suvrath Mahadevan, Gudmundur Stefansson, Andrea S. J. Lin, Sinclaire Jones, Andrew Monson, Brock A. Parker, Henry A. Kobulnicky, Tera N. Swaby, Luke Powers, Corey Beard, Chad F. Bender, Cullen H. Blake, William D. Cochran, Jiayin Dong, Scott A. Diddams, Connor Fredrick, Arvind F. Gupta, Samuel Halverson, Fred Hearty, Sarah E. Logsdon, Andrew J. Metcalf, Michael W. McElwain, Caroline Morley, Jayadev Rajagopal, Lawrence W. Ramsey, Paul Robertson, Arpita Roy, Christian Schwab, Ryan C. Terrien, John Wisniewski and Jason T. Wright, 5 August 2022, The Astronomical Journal.
DOI: 10.3847/1538-3881/ac7c20