(ORDO NEWS) — A red dwarf star just 105 light-years away may host at least one habitable world.
In close orbit around a cool, dim star, scientists have discovered and confirmed the presence of two rocky exoplanets – one of them conveniently located at a distance from the star, known as the habitable zone.
Further observations will be needed to further determine its nature, but the discovery is exciting and suggests that even more such worlds could be discovered in the vicinity of the Sun.
Even if the exoplanet is not habitable, worlds in the habitable zone are relatively rare, especially rocky ones.
Thus, in any case, the discovery is an important benchmark for characterizing the population of these exoplanets.
These two exoplanets were discovered as a result of observations by NASA’s TESS telescope, which searches for exoplanets.
Observing the small red dwarf star LP 890-9 (aka TOI-4306), the telescope captured faint, regular dips in starlight that are characteristic of exoplanets orbiting between us and the star – passages known as transits, with a period of 2, 7 days.
Transit data can tell us quite a lot about an exoplanet. First, it is the fact of its existence. Then there is the orbital period. And, based on how much the star’s light dims, scientists can also determine the exoplanet’s diameter.
But to confirm the discovery and get more data on exoplanets, more observations need to be made using different instruments.
“These follow-up observations,” explains astronomer Laetitia Delreze from the University of Liège in Belgium, “are especially important for relatively cool stars like TOI-4306, which emit most of their light in the near infrared, and for which TESS has a rather limited sensitivity. “.
She and her team used telescopes from the SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) consortium that are sensitive to the near-infrared wavelength emitted by TOI-4306. The transit data obtained from these observations confirmed the existence of an exoplanet named LP 890-9b.
The team then looked for exoplanets that might have been missed by TESS and discovered a second world slightly further from the star than LP 890-9b. This exoplanet, named LP 890-9c, has an orbital period of 8.4 days.
Other data, including radial velocity measurements that determine the exoplanet’s gravitational pull on the star and thus determine its mass, allowed the team to characterize the two exoplanets in detail.
Although the masses of both exoplanets have not been measured, the radial velocity data have given scientists an upper limit on the mass for both exoplanets.
The diameter of LP 890-9b is approximately 1.32 times the diameter of the Earth, and the mass is 13 times greater.
The diameter of LP 890-9c is about 1.37 times the diameter of the Earth, and the mass is 25 times greater.
These measurements correspond to the density of rocky worlds such as Earth, Mars and Venus, not gaseous or icy worlds such as Jupiter or Neptune.
This means that exoplanets can be classified as super-Earths – rocky worlds that are larger than Earth and smaller than Neptune.
It becomes interesting where they orbit the star – in particular, the outer exoplanet LP 890-9c.
It’s one of the first things scientists look at when assessing the potential habitability of an alien world. An exoplanet that is too close or too far from its star will be either too hot or too cold, respectively, for life as we know it.
But near the orbit of each star, there is a temperate, or habitable, zone in which liquid water can comfortably exist on the planet’s surface.
LP 890-9c may be in close orbit to its star compared to Earth, but that star is much, much colder and dimmer than the Sun.
At its orbital position, the exoplanet is in the conservative habitable zone of its star, receiving stellar radiation levels similar to those on Earth.
After the TRAPPIST system, this is the second most promising potentially habitable world discovered so far, the researchers say.
“But we shouldn’t get ahead of ourselves. Being in the right place doesn’t guarantee a palm beach,” says astronomer Robert Wells of the University of Bern in Germany.
“Our neighbor Venus, which is, so to speak, a pressure cooker with a high carbon dioxide content and a temperature of about 500 degrees Celsius, is also not far from this so-called habitable zone around the Sun.”
LP 890-9c is very close to the point where a young planet could be engulfed in a runaway greenhouse effect like Venus, but we don’t know for sure what’s going on there.
A second group of scientists, including some of the authors of LP 890-9, have already submitted a preprint dedicated to this mystery, but we will most likely not know until we get observational data on the exoplanet’s atmosphere, if it has one.
The James Webb Space Telescope has already proven that it can do this. The telescope, as you can imagine, is in high demand, so we may have to wait a while to get the results of the observations.
On the other hand, a promising target like the LP 890-9c might be worth the hassle, because whatever the outcome, we have a lot to learn.
“It’s important,” says astronomer Amaury Triaud of the University of Birmingham in the UK, “to find as many temperate terrestrial worlds as possible in order to study the diversity of exoplanet climates and ultimately be able to measure the frequency of occurrences of biology in space.”
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