Los astrónomos descubren un sistema multiplanetario cercano con dos planetas del tamaño de la Tierra

Los astrónomos del MIT han descubierto un nuevo sistema multiplanetario ubicado a 10 parsecs, o unos 33 años luz, de la Tierra, lo que lo convierte en uno de los sistemas multiplanetarios más cercanos a nuestro sistema. La estrella en el centro del sistema probablemente alberga al menos dos planetas terrestres del tamaño de la Tierra. Crédito: MIT News, con el personaje de TESS Satellite cortesía de la NASA

Ubicado a solo 33 años luz de la Tierra, el sistema parece albergar dos planetas rocosos del tamaño de la Tierra.

Un nuevo sistema multiplanetario ha sido descubierto dentro de nuestra galaxia vecina por astrónomos en[{» attribute=»»>MIT and elsewhere. It lies just 10 parsecs, or about 33 light-years, from Earth, making it one of the closest known multiplanet systems to our own.

At the heart of the system lies a small and cool M-dwarf star, named HD 260655, and astronomers have found that it hosts at least two terrestrial, Earth-sized planets. The rocky worlds have relatively tight orbits, exposing the planets to temperatures that are too high to sustain liquid surface water. Therefore, they are unlikely to be habitable.

Nevertheless, scientists are excited about this system because the proximity and brightness of its star will give them a closer look at the properties of the planets and signs of any atmosphere they might hold.

“Both planets in this system are each considered among the best targets for atmospheric study because of the brightness of their star,” says Michelle Kunimoto, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research and one of the discovery’s lead scientists. “Is there a volatile-rich atmosphere around these planets? And are there signs of water or carbon-based species? These planets are fantastic test beds for those explorations.”

The team will present its discovery on June 15, 2022, at the meeting of the American Astronomical Society in Pasadena, California. Team members at MIT include Katharine Hesse, George Ricker, Sara Seager, Avi Shporer, Roland Vanderspek, and Joel Villaseñor, along with collaborators from institutions around the world.

Illustration of NASA’s Transiting Exoplanet Survey Satellite (TESS) at work. Credit: NASA’s Goddard Space Flight Center

Data power

The new planetary system was initially identified by NASA’s Transiting Exoplanet Survey Satellite (TESS), an MIT-led mission that is designed to observe the nearest and brightest stars, and detect periodic dips in light that could signal a passing planet.

In October 2021, Kunimoto, a member of MIT’s TESS science team, was monitoring the satellite’s incoming data when she noticed a pair of periodic dips in starlight, or transits, from the star HD 260655.

She ran the detections through the mission’s science inspection pipeline, and the signals were soon classified as two TESS Objects of Interest, or TOIs — objects that are flagged as potential planets. The same signals were also found independently by the Science Processing Operations Center (SPOC), the official TESS planet search pipeline based at NASA Ames. Scientists typically plan to follow up with other telescopes to confirm that the objects are indeed planets.

The process of classifying and subsequently confirming new planets can often take several years. For HD 260655, that process was shortened significantly with the help of archival data.

The Keck observatory domes atop Mauna Kea. Credit: T. Wynne / JPL

Soon after Kunimoto identified the two potential planets around HD 260655, Shporer looked to see whether the star was observed previously by other telescopes. As luck would have it, HD 260655 was listed in a survey of stars taken by the High Resolution Echelle Spectrometer (HIRES), an instrument that operates as part of the Keck Observatory in Hawaii. HIRES had been monitoring the star, along with a host of other stars, since 1998, and the researchers were able to access the survey’s publicly available data.

HD 260655 was also listed as part of another independent survey by CARMENES, an instrument that operates as part of the Calar Alto Observatory in Spain. As these data were private, the team reached out to members of both HIRES and CARMENES with the goal of combining their data power.

“These negotiations are sometimes quite delicate,” Shporer notes. “Luckily, the teams agreed to work together. This human interaction is almost as important in getting the data [as the actual observations]. «

tirón planetario

Finalmente, este esfuerzo colaborativo confirmó rápidamente la presencia de dos planetas alrededor de HD 260655 en unos seis meses.

Para confirmar que las señales de TESS eran de hecho de dos planetas en órbita, los investigadores observaron los datos de los HIRES y CARMENES de la estrella. Ambos sondeos miden la oscilación gravitatoria de una estrella, también conocida como su velocidad radial.

«Cada planeta que orbita alrededor de una estrella tendrá una pequeña fuerza gravitacional sobre su estrella», explica Kunimoto. «Lo que estamos buscando es cualquier ligero movimiento de esa estrella que pueda indicar un objeto de masa planetaria atrayéndola».

De ambos conjuntos de datos de archivo, los investigadores encontraron señales estadísticamente significativas de que las señales detectadas por TESS eran de hecho dos planetas en órbita.

«Entonces supimos que teníamos algo muy emocionante», dice Sporer.

Luego, el equipo observó de cerca los datos de TESS para determinar las características de ambos planetas, incluido su período orbital y tamaño. Determinaron que el planeta interior, apodado HD 260655b, orbita la estrella cada 2,8 días y tiene aproximadamente 1,2 veces el tamaño de la Tierra. El segundo exoplaneta, HD 260655c, rota cada 5,7 días y es 1,5 veces más masivo que la Tierra.

A partir de los datos de velocidad radial de HIRES y CARMENES, los investigadores pudieron calcular la masa de los planetas, que está directamente relacionada con la amplitud con la que cada planeta arrastra a su estrella. Descubrieron que el planeta interior tiene una masa dos veces la masa de la Tierra, mientras que el planeta exterior tiene una masa de aproximadamente tres masas terrestres. A partir de su tamaño y masa, el equipo estimó la densidad de cada planeta. El planeta interior más pequeño es un poco más denso que la Tierra, mientras que el planeta exterior más grande es un poco menos denso. Es probable que ambos planetas, dependiendo de su densidad, sean de composición terrestre o rocosa.

Los investigadores también estiman, en base a sus órbitas cortas, que la superficie interna del planeta es un tostado de 710 K (818 grados).[{» attribute=»»>Fahrenheit), while the outer planet is around 560 °K (548 °F).

“We consider that range outside the habitable zone, too hot for liquid water to exist on the surface,” Kunimoto says.

“But there might be more planets in the system,” Shporer adds. “There are many multiplanet systems hosting five or six planets, especially around small stars like this one. Hopefully, we will find more, and one might be in the habitable zone. That’s optimistic thinking.”

This research was supported, in part, by NASA, the Max-Planck-Gesellschaft, the Consejo Superior de Investigaciones Científicas, the Ministerio de Economía y Competitividad, and the European Regional Development Fund.