Situated simply 33 light-years from Earth, the system seems to host two rocky Earth-sized planets.

A brand new multiplanetary system inside our galactic neighborhood has been found by astronomers in[{” 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.

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.

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].”

planetary pull

In the long run, this collaborative effort rapidly confirmed the presence of two planets round HD 260655 in about six months.

To substantiate that the TESS alerts have been certainly coming from two orbiting planets, the researchers analyzed HIRES and CARMENES information from the star. Each surveys measure a star’s gravitational wobble, also referred to as its radial velocity.

“Every planet orbiting a star can have a small gravitational pull on its star,” explains Kunimoto. “What we’re on the lookout for is any slight motion of that star that may point out a planetary-mass object is pulling on it.”

From each units of archival information, the researchers discovered statistically important indicators that the alerts detected by TESS have been actually two orbiting planets.

“Then we knew we had one thing very thrilling,” says Shporer.

The workforce then took a more in-depth take a look at the TESS information to pin down the properties of each planets, together with their orbital interval and measurement. They decided that the internal planet, named HD 260655b, orbits the star each 2.8 days and is about 1.2 occasions bigger than Earth. The second outer planet, HD 260655c, orbits each 5.7 days and is 1.5 occasions bigger than Earth.

From the radial velocity information from HIRES and CARMENES, the researchers have been capable of calculate the mass of the planets, which is straight associated to how far every planet tugs on its star. They discovered that the internal planet is about twice as large as Earth, whereas the outer planet is about three Earth lots. From their measurement and mass, the workforce estimated the density of every planet. The smaller internal planet is barely extra dense than Earth, whereas the bigger outer planet is barely much less dense. Each planets, relying on their density, are most likely terrestrial or rocky in composition.

The researchers additionally estimate, based mostly on their brief orbits, that the internal planet’s floor is about 710 kelvins (818 levels Celsius).[{” 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.