A new list of stars tells us where to look for planets similar to Earth


The artistic concept of TESS in search of exoplanets.
Illustration: NASA / Cornell University

Astronomers have created a catalog of 1,822 nearby stars around which the Transiting Exoplanet Survey Satellite (TESS) mission could spot planets receiving a level of starry light similar to that of the Earth. This is a crucial step in humanity's search for an Earth-like and potentially livable exoplanet.

The question of whether life exists elsewhere and what it looks like, and whether there are other habitable planets more generally, is a matter of lasting importance for humanity. It will take a long time to answer this question. But an important first step is to determine where to look. That's what this new document does.

"We have identified the stars where TESS can search for Earth-like planets," Lisa Kaltenegger, an associate professor of astronomy at Cornell University, told Gizmodo.

For these 1,822 stars, the TESS is sensitive enough to detect planets as small as twice the radius of the Earth, receiving radiation levels similar to those of the Earth. According to these authors, the TESS could detect planets as small as 1.6 Earth's radius for 1,690 of them and an Earth's radius for 408, according to the article published in The Astrophysical Journal. And for 227 of these stars, TESS can search for planets throughout their habitable zone – what humans regard as the Goldilocks area, where water can stably exist on the surface of the planet. A rocky planet.

The NASA TESS was launched less than a year ago with a bold mission: to inspect the neighboring galactic neighborhood in search of stars possessing their own planet. He has already found his first exoplanet. TESS is looking for the light of stars that is gradually attenuated, suggesting a planet in orbit. An important subset of these planets are the Earth's exoplanets in habitable areas. Kaltenegger and her teammates combined TESS data with Gaia satellite, a huge catalog of nearby stars, to produce the most recent list. They calculated the habitable areas of these stars according to the amount of star radiations that the candidate planets would receive at increasing distances from their host stars.

This is an important inventory. "Since TESS will observe almost all of the sky, there will be literally millions of stars that we will have to explore to detect planetary signals," Jessie Christiansen, researcher at NASA's Exoplanet Science Institute, told Gizmodo. was not involved in the study. "Having a way to prioritize the stars to look at first, or closer, is extremely helpful. This list is a first glimpse of which of these stars could host potentially habitable planets that would also be detectable in TESS data. So it's a very interesting list to have. "

There are limits: many of these stars show only one planetary transit during the observation period, which leaves plenty of room for error and requires additional follow-up. Moreover, they are not sun-like stars. According to the document, "almost all of our selected sample is indeed made of fresh dwarf stars", such as TRAPPIST-1 or Proxima Centauri. "It's easier to find rocky planets around smaller stars, and most of the stars in this catalog are fresh and red stars (Dwarfs M)," Christiansen said. "In terms of habitability, it remains to be seen whether the high-energy radiation (UV) emitted by the dwarves during their many sterilizing eruptions would sterilize the rocky planets that orbit them."

Astronomers should certainly always watch, of course. Ultimately, it will be monitoring missions such as the James Webb Space Telescope and future missions such as HabEx or LUVOIR to confirm whether these planets can truly accommodate life. But if you're looking for earth-like exoplanets, it's crucial to understand what your telescope can really do and catalog the stars that might host these planets.

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