An Exoplanet 22.5 light-year away with triple-star system discovered by astronomers. The new planet only clocks approximately 1.35 times Earth’s physical size and weighs up to 8.4 times the mass of Earth in that size.
Stars are often locked in a dance with others out there in the wider universe, orbiting a mutual centre of gravity. Astronomers have just discovered an exoplanet in such a triple-star system.
It has the rather catchy name LTT 1445Ab as it orbits the main star of three red dwarfs that create the LTT 1445 system, situated about 22.5 light-years away.
Astronomer Jennifer Winters of the Harvard-Smithsonian Center for Astrophysics told New Scientist, “If you’re standing on the surface of that planet, there are three suns in the sky, but two of them are pretty far away and small-looking. They are like two red, forbidding eyes in the sky.”
TESS, NASA’s planet-hunting space telescope built to discover exoplanets passing between us and their home star, found the planet by detecting the telltale dimming as the planet blocks a small proportion of star’s light.
The dimming depth and the star’s small movements as it is pulled very slightly by the gravity of the planet (detected with other telescopes) enable researchers to place constraints on the planet’s size and mass.
LTT 1445Ab is very different from HD 131399Ab, another three-sun exoplanet, discovered in 2016. The latter is a giant in triple system 340 light-years away with a 550-year orbit around one of the stars.
The new planet only clocks approximately 1.35 times Earth’s physical size. It weighs up to 8.4 times the mass of Earth in that size, so it is much denser than our home planet.
Although this size and mass place it strongly in the rocky category — like Earth, Venus, and Mars, as opposed to gas or ice giants — and although it would be home to a lot of really amazing skies, habitability opportunities are likely to be quite low.
Only once every 5.36 Earth days the exoplanet whips around its star. It’s surface temperature would be a scorching 428 Kelvin (155 ° C; 311 ° F) at such proximity.
Nevertheless, astronomers are excited to take a closer look. This is because LTT 1445Ab may have an atmosphere-and rocky planet with atmospheres orbiting in front of their stars are good places for us to test the detection tools we use to search for gasses like methane and carbon dioxide.
A planet with an atmosphere would not only dim the light of the star but would also alter it depending on the chemical composition of the environment. Specifically, researchers can analyze modifications in the light spectrum of the star to piece the composition together.
Our presently active technology is not very suitable for this, but Hubble’s successor, the James Webb Space Telescope, has high expectations. It is due to be started in 2021, and astronomers are eager to identify and pick targets they would like to study.
LTT 1445Ab could be a perfect candidate. There will be plenty of possibilities for observations because it transits so frequently. It is only 22.5 light-years away -comparatively close in cosmic scales. Its red dwarf star is bright enough to bring the atmosphere back to the light, but not so big as to make the planet outshone.
And, even if it has no atmosphere, or if there are no biosignatures in its atmosphere, rocky planets are comparatively prevalent in close orbit around red dwarf stars. So having a closer look at LTT 1445Ab could inform us more about what on such planets we can expect to discover.
The document was presented to The Astronomical Journal and can be found on arXiv.