MIT astronomers have discovered a new multiplanet system that lies just 10 parsecs, or about 33 light-years, from Earth, making it one of the closest known multiplanet systems to our own. The star at the heart of the system likely hosts at least two terrestrial, Earth-sized planets. Credit: MIT News, with TESS Satellite figure courtesy of NASA
Located just 33 light years from Earth, the system appears to host two rocky, Earth-sized planets.
A new multiplanet system within our galactic neighborhood has been discovered by astronomers at
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
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].”
Planetary pull
In the end, this collaborative effort quickly confirmed the presence of two planets around HD 260655 in about six months.
To confirm that the signals from TESS were indeed from two orbiting planets, the researchers looked through both HIRES and CARMENES data of the star. Both surveys measure a star’s gravitational wobble, also known as its radial velocity.
“Every planet orbiting a star is going to have a little gravitational pull on its star,” Kunimoto explains. “What we’re looking for is any slight movement of that star that could indicate a planetary-mass object is tugging on it.”
From both sets of archival data, the researchers found statistically significant signs that the signals detected by TESS were indeed two orbiting planets.
“Then we knew we had something very exciting,” Shporer says.
The team then looked more closely at TESS data to pin down properties of both planets, including their orbital period and size. They determined that the inner planet, dubbed HD 260655b, orbits the star every 2.8 days and is about 1.2 times as big as the Earth. The second outer planet, HD 260655c, orbits every 5.7 days and is 1.5 times as big as the Earth.
From the radial-velocity data from HIRES and CARMENES, the researchers were able to calculate the planets’ mass, which is directly related to the amplitude by which each planet tugs on its star. They found the inner planet is about twice as massive as the Earth, while the outer planet is about three Earth masses. From their size and mass, the team estimated each planet’s density. The inner, smaller planet is slightly denser than the Earth, while the outer, larger planet is a bit less dense. Both planets, based on their density, are likely terrestrial, or rocky in composition.
The researchers also estimate, based on their short orbits, that the surface of the inner planet is a roasting 710 kelvins (818 degrees
