(ORDO NEWS) — Astronomers have discovered a new multi-planet system in our galaxy, which is 33 light-years from Earth, making it one of the closest known multi-planet systems.
At its center is the small, cold M-dwarf star HD 260655, and astronomers have found that it hosts at least two Earth-sized planets. Rocky worlds are most likely uninhabitable because their orbits are relatively tight, meaning planets are exposed to temperatures that are too high to sustain liquid water on the surface.
In October 2021, Michelle Kunimoto, a member of the MIT TESS science team, was monitoring incoming satellite data when she noticed a pair of periodic dips in the light of the star HD 260655.
She ran the detected signals through the satellite’s scientific verification system, and they were soon classified as potential planets.
The process of classifying and then confirming new planets can often take several years. In the case of HD 260655, this process has been significantly reduced thanks to archival data.
The scientists checked to see if this star had been previously observed by other telescopes. Luckily, HD 260655 was included in the list of stars taken by the HIRES high-resolution scale spectrometer, an instrument operated by the Keck Observatory in Hawaii.
HD 260655 was also included in another independent survey, CARMENES, an instrument operated by the Calar Alto Observatory in Spain. Since this information has been kept private, the team has reached out to members of HIRES and CARMENES in order to merge their data.
Working together on two sets of archival material, over about six months, the researchers established statistically significant indications that the signals detected by TESS were indeed two orbiting planets.
The team then took a closer look at the TESS data to determine the properties of both planets, including their orbital period and size.
The inner planet, dubbed HD 260655b, orbits the star every 2.8 days and is about 1.2 times the size of Earth. The second outer planet, HD 260655c, orbits every 5.7 days and is 1.5 times the size of Earth.
Based on the radial velocity data obtained with HIRES and CARMENES, the researchers were able to calculate the mass of the planets, which is directly related to the amplitude with which each planet pulls its star.
Astronomers have found that the inner planet is about twice as massive as the Earth, while the outer one is about three Earth masses.
Based on their size and mass, it was found that the density of the inner, smaller planet is slightly larger than the Earth, and the outer, larger planet is less dense. Both of them, based on their density, are most likely terrestrial or rocky in composition.
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