The discovery of at least two rocky “super-Earths” orbiting a nearby dwarf star could provide important clues in the search for aliens, astronomers say.
While the worlds as we know them are unlikely to be habitable for life, the star and its exoplanets are among the closest multi-world systems to Earth, a mere 33 light-years away.
This makes the system an excellent target for further study, in part because it could contain more planets, including the potential for one in the habitable zone.
“There are many multi-planet systems that host five or six planets, especially around small stars like this one,” said astrophysicist Avi Shporer of MIT’s Kavli Institute for Astrophysics and Space Research.
“Hopefully we’ll find more, and maybe one is in the habitable zone. That is optimistic thinking.”
The discovery of at least two rocky “super-Earths” (shown in an artist’s rendering) orbiting a nearby dwarf star could provide important clues in the search for aliens, astronomers say
IMPORTANT FACTS ABOUT THE NEWLY DISCOVERED “SUPER EARTHS”
HD260655b
Average temperature: 816 degrees Fahrenheit
Orbital Period: Orbits the star every 2.8 days
Size: About 1.2 times the size of Earth
Mass: Twice as massive and slightly denser than Earth
Composition: Terrestrial/Rocky
HD260655c
Average temperature: 543 degrees Fahrenheit
Orbital Period: Orbits the star every 5.7 days
Size: About 1.5 times the size of Earth
Mass: About three Earth masses, but slightly less dense
Composition: Terrestrial/Rocky
Although the star HD 260655 is cooler and dimmer than our Sun, the planets’ proximity to the red dwarf means the worlds would be far too hot for life.
HD 260655b has an average temperature of 816 degrees Fahrenheit (435 degrees Celsius), while HD 260655c is a milder but still fiery 543 degrees Fahrenheit (284 degrees Celsius).
“We think this area outside the habitable zone is too hot for liquid water to exist on the surface,” said astronomer Michelle Kunimoto of MIT’s Kavli Institute for Astrophysics and Space Research.
Still, scientists are excited about this system, as its star’s proximity and brightness will give them a closer look at the planets’ properties and signs of an atmosphere they may contain.
“Both planets in this system are considered one of the best targets for atmospheric studies because of the brightness of their star,” Kunimoto said.
“Is there an atmosphere around these planets that is rich in volatile matter? And are there any signs of water- or carbon-based species? These planets are fantastic testbeds for this exploration.’
The new planetary system was originally identified by NASA’s Transiting Exoplanet Survey Satellite (TESS), an MIT-led mission 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 starlight dips, or transits, from the star HD 260655.
She ran the detections through the mission’s scientific inspection pipeline, and the signals were soon classified as two TESS Objects of Interest, or TOIs — objects flagged as potential planets.
The process of classifying and then confirming new planets can often take several years, but for HD 260655, this process has been significantly shortened using archival data.
The fully integrated Transiting Exoplanet Survey Satellite (TESS), launched in 2018 to find thousands of new planets orbiting other stars
Shortly after Kunimoto identified the two potential planets around HD 260655, Shporer checked to see if the star had previously been observed by other telescopes.
Fortunately, HD 260655 was included in a star survey performed by the High Resolution Echelle Spectrometer (HIRES), an instrument operated as part of the Keck Observatory in Hawaii.
HIRES has been monitoring the star, along with a variety of other stars, since 1998, and the researchers were able to access publicly available data from the survey.
In the end, this joint effort quickly confirmed the presence of two planets around HD 260655 in about six months.
The team then looked more closely at the TESS data to determine the properties of both planets, including their orbital periods and sizes.
They found that the inner planet, designated 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.
From the archive data, the researchers were then able to calculate the mass and density of the planets.
They found that the inner planet is about twice as massive and slightly denser than Earth, while the outer planet is about three Earth masses but slightly less dense. Both planets are likely terrestrial or rocky in composition given their density, the astronomers said.
So far, more than 5,000 exoplanets have been confirmed in our Milky Way, with experts particularly interested in finding terrestrial or rocky worlds like Earth, Venus and Mars.
The researchers presented their findings at the 240th meeting of the American Astronomical Society.
WHAT IS THE TESS SPACECRAFT?
NASA’s “Planet Hunter” spacecraft is equipped with four cameras, allowing it to survey 85 percent of the entire sky while searching for exoplanets orbiting stars less than 300 light-years away.
By studying objects much brighter than Kepler’s targets, it is hoped TESS could find new clues about the possibility of life elsewhere in the universe.
Its four wide-field cameras will view the sky in 26 segments, each of which will be observed individually.
In its first year of operation it mapped the 13 sectors that make up the southern sky and combed the northern sectors the following year.
Since launch in 2018, TESS has found over 170 confirmed exoplanets and has a catalog of over 4,700 yet to be verified.
It has also discovered other strange phenomena, including supernova and triple star systems, since it was launched.
Tess is 1.5 meters wide and smaller than most adults.
The observatory is 1.2 meters in diameter (not counting the solar panels, which fold for launch) and weighs just 362 kilograms (800 pounds).
NASA says it’s somewhere between the size of a refrigerator and a stacked washer and dryer.