Un planeta gigante y esponjoso que orbita una fría estrella enana roja

El telescopio Kitt Peak del Observatorio Nacional ayuda a determinar esto[{» 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, investigador del Carnegie Institution for Science’s Earth and Planetary Laboratory y primer autor de un artículo publicado en Diario astrológicoa. Hasta ahora, esto solo se ha visto en pequeñas muestras de estudios Doppler, que generalmente han encontrado planetas gigantes lejos de estas estrellas enanas rojas. Hasta ahora no hemos tenido una muestra lo suficientemente grande de planetas para encontrar planetas gaseosos cercanos de una manera robusta».

Todavía hay misterios sin explicación en torno a TOI-3757 b, el principal de los cuales es cómo se pudo formar un planeta gigante gaseoso alrededor de una estrella enana roja, especialmente un planeta de baja densidad. Sin embargo, el equipo de Kanodia cree que pueden tener una solución a este misterio.

Desde los terrenos del Observatorio Nacional Kit Peak (KPNO), un programa de NSF NOIRLab, el telescopio Wisconsin-Indiana-Yale-NOIRLab (WIYN) de 3,5 metros parece estar observando la Vía Láctea a medida que se derrama desde el horizonte. El resplandor atmosférico rojizo, un fenómeno natural, también tiñe el horizonte. KPNO está ubicado en el desierto de Arizona Sonoran en la Nación Tohono O’odham y esta vista clara de parte del plano de la Vía Láctea muestra las condiciones favorables en este entorno necesario para ver cuerpos celestes tenues. Estas condiciones, que incluyen bajos niveles de contaminación lumínica, cielos 20° más oscuros y condiciones atmosféricas secas, permitieron a los investigadores del consorcio WIYN seguir las observaciones de galaxias, nebulosas y exoplanetas, así como muchos otros objetivos astronómicos utilizando el WIYN de 3,5 metros. telescopio y su hermano, el telescopio WIYN de 0,9 metros. Crédito: KPNO/NOIRLab/NSF/AURA/R.Chispas

Sugieren que la densidad extremadamente baja de TOI-3757 b podría ser el resultado de dos factores. El primero se relaciona con el núcleo rocoso del planeta; Se cree que los gigantes gaseosos comenzaron como núcleos rocosos masivos con una masa de unas diez veces la masa de la Tierra, momento en el cual atraen rápidamente grandes cantidades de gas cercano para formar los gigantes gaseosos que vemos hoy. TOI-3757b tiene una menor abundancia de elementos pesados ​​que otras enanas M con gigantes gaseosos, y esto puede haber resultado en la formación del núcleo rocoso más lentamente, lo que retrasó el inicio de la acumulación de gas y, por lo tanto, afectó la densidad general del planeta.

Un segundo factor puede ser la órbita del planeta, que tentativamente se cree que es ligeramente elíptica. Hay momentos en los que se acerca más a su estrella que otros, lo que da como resultado un exceso de calor significativo que puede hacer que la atmósfera del planeta se hinche.

Satélite en tránsito de la NASA para la encuesta de exoplanetas ([{» 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