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[EN VIDÉO] In video: The Tess satellite has just completed its main mission NASA’s Tess satellite has just completed its main objective at the end of…
On April 17, 2023, the now famous Encyclopedia of Extrasolar Planets mentions that 5,363 exoplanets are known from the noosphere. Several thousand of them were discovered thanks to NASA’s Kepler space telescope. The method used by Kepler is that of planetary transit, that is, it consisted in emphasizing a periodic drop in the luminous intensity of a star due to the passage between it and Kepler’s instruments of an exoplanet.
Kepler is no longer working and although we continue to discover exoplanets in the list of candidates in their observation archives, NASA launched a telescope to adopt it almost 5 years ago: Tess (Transiting Exoplanet Survey Satellite). The agency has also just posted several videos online to celebrate the fifth anniversary of the start of observations of Tess, and in a press release, incidentally reminds that they were not limited to discovering potential exoterres in the habitability zone.
With her four cameras, Tess monitors large areas of the sky, called sectors, for about a month. Each sector measures 24 by 96 degrees – about the width of a person’s hand at arm’s length, and stretches from horizon to zenith. CCD cameras capture a total of 192 million pixels in each image. During her main mission, Tess took one of these images every 30 minutes, but this data overload grew over time. Cameras now record each sector every 200 seconds. For a fairly accurate French translation, click the white rectangle at the bottom right. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose French. © Goddard Space Flight Center/NASA Scientific Visualization Studio
Exoterres, but also eruptions from supermassive black holes
In fact, from the more than 93% of the sky observed by Tess, with 329 exoplanets already discovered and thousands more awaiting confirmation (e.g. from amateur astronomers on Earth with Unistellar eVscopes), it is also possible to surprise and study transient phenomena such as supernovae and eruptions of supermassive black holes.
We can cite in this context the case of the active galaxy ESO 253-3 (see video below), which is known to contain a supermassive black hole that erupts every 114 days. This periodicity is thought to reflect the passage of a giant star to periapsis, which at the time produced a mass transfer from the star due to tidal forces, suddenly feeding the accretion disk surrounding the compact star, which already contains about 78 million solar masses — that of the Milky Way contains only just over 4 million.
ESO 253-3 is a dual-active region spiral galaxy located about 570 million light-years from the Milky Way toward the constellation of Painters (Latin Pictor, -is, abbreviated as Pic), a constellation of the faintly luminous southern hemisphere. For a fairly accurate French translation, click the white rectangle at the bottom right. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose French. © Nassa’s Goddard Space Flight Center/Scientific Visualization Studio
Among the significant exoplanet discoveries that can be attributed to Tess, the telescope’s primary purpose was to search for rocky exoplanets, possibly real potential exoterres, located within a radius of just 300 light-years from the Sun, within range of James-Webb telescopes in an attempt to characterize possible atmospheres), we can cite the case of the planetary system discovered around an M-type red dwarf, located 100 light-years from the solar system and therefore observable in the constellation Dorade.
This red dwarf, whose mass and size is about 40% that of the Sun and whose surface temperature is half that of the sun, is called TOI 700 and the next exoplanet is called TOI 700 b, the others in alphabetical order. TOI is an English abbreviation for Tess Objects of Interest, which can be translated as “Tess’s Interesting Object”. TOI 700 d and TOI 700 e have attracted the attention of astrophysicists in particular because they are potentially exoterres. Futura also wrote several articles about it, from which we partially reproduce the content.
A presentation of the discovery of TOI 700 d by Tess using the planetary transit method. For a fairly accurate French translation, click the white rectangle at the bottom right. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose French. © NASA Goddard
With a potentially habitable exoplanet, caution is advised
Because TOI 700 d is in the habitable zone, that means it’s in an area where its star’s heat could create liquid water. But there is still a long way to go, as the astrophysicist Franck Selsis, member of the CNRS and the Bordeaux Astrophysics Laboratory (LAB), explained to Futura and on several occasions.
The atmosphere of such an exoplanet could make it as inhospitable as Venus; one can also wonder at its initial water content and the fact that it was able to retain enough to be truly habitable. We also know that red dwarfs are particularly angry in the early stages of their existence, and that the radiation they then emit is not only lethal, but will erode any atmosphere.
TOI 700 d, like its sisters TOI 700 b and TOI 700 c, is in synchronous rotation, which means that these planets always show the same face to their star as the moon. The climate models of such exoplanets show that in certain regions it is still possible for liquid water to exist because if they have atmospheres, currents can transport and distribute heat between the constantly diurnal and nocturnal surfaces. So life could exist on such planets.
It is of course too early to speculate about the exobiology that might exist on TOI 700 d. But it is sure to be a target of choice for the next generation of instruments like the James Webb Space Telescope. They will be able to detect and analyze the composition of the potential atmospheres of Tess TOIs in hopes of discovering compelling biosignatures that have yet to be defined. And it will not be an easy task, as Franck Selsis always explained to Futura in the case of the discovery of the Trappist 1 system.
A presentation of the discovery of TOI 700 e by Tess. For a fairly accurate French translation, click the white rectangle at the bottom right. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose French. © Goddard Space Flight Center/NASA Scientific Visualization Studio