TOI 700e was the first rocky exoplanet of 2023. Which will be the first in 2024?


TOI 700e
Artist’s impression of the exoplanet TOI 700 e. Source: NASA Exoplanets
Sergio Messina Sergio Messina 6 minutes

TOI 700 e It is exoplanet rocky type with a mass slightly less than that of Earth (8/10 that of Earth) and a radius nearly equal to that of Earth (though only 5 cents less).

The acronym TOI stands for Target Of Interest, which is one of many stars observed by the TESS space telescope that has been shown to be of particular interest because it could host exoplanets.

In a chronological list of the rocky planets TOI 700 and ranks 199 and is the first discovered in 2023.

Frankly, the discovery and subsequent confirmation of an exoplanet takes time, even years. Therefore, the date an exoplanet discovery is reported (as with any other discovery) is the date the scientific paper was accepted and published in an international scientific journal. However, all this can happen even months after the actual date of discovery.

How it was discovered

Space telescope TESS is a photometric telescope built not to acquire high-resolution images of stars or celestial objects in general (such as the Hubble and James Webb telescopes), but the brightness of stars, more precisely light curves.

A star’s light curves are measurements of the electromagnetic flux at fixed time intervals (in the case of TESS, every 2 minutes for bright stars and every 30 minutes for faint ones).

TOI 700 transits
Light curves of the TOI 700 star with the presence of an eclipse (decrease in radiant flux) produced by the transit of each planet. Credit. Gilbert et al. ApJ, 944L, 35 (2023)

The goal of TESS photometric observations is to search for possible eclipses caused by the passage of an exoplanet in front of the star’s disk.

The star is observed continuously in the hope that at some point a transition will occur in front of its disk, which will be detected as a small decrease in brightness.

The TESS telescope makes it possible to search for exoplanets using the transit method.

After the Kepler telescope, TESS is the one to discover the largest number of exoplanets with the transit technique.

Who discovered TOI 700 e

The first three planets b, c, d TOI 700 stars were discovered in 2020 by an international team led by a young astronomer Emily Gilbert from the Jet Propulsion Laboratory. fourth planet TOI 700 e, it was also discovered by the same team in 2023 and published in Astrophysical Journal Letters by Gilbert as the first author and 31 other co-authors various institutions, including 3 Italians from the Campo Catino Astronomical Observatory.

The star TOI 700 was already known as of 2020 to have been discovered to host three planets.

Among the four planets, TOI 700 d is the first Earth-like planet in the habitable zone of its star discovered by TESS, thanks to Gilbert’s own analyses. So it is a star that has already been studied and there is considerable interest in it.

The habitable zone is defined as the range of distances from the star at which the temperature would allow the presence of liquid water.

After identifying the transits of planets b, c, d, the team also managed to detect transits planet e. As shown in the previous image, the eclipse produced by the latter planet is barely detectable, making it particularly difficult to discover.

But that is not all. In fact, Gilbert’s team gained additional telescope time with TESS to continue studying the system to better characterize and discover possible additional planets.

Planetary architecture of the star TOI 700

The TOI 700 star is a red dwarf with a surface temperature of around 3000 degrees Kelvin. This is home to a planetary system of 4 planets, but there may be even more, as yet undiscovered.

Three of these planets are classified as terrestrial planets, while one is mini-Neptunian. In addition, two of the terrestrial planets are located in the habitable zone.

TOI 700
Illustration of the distribution of the orbits of planets b,c,d,e around the central star TOI 700. Credit: Gilber et al. ApJ 944L, 35 (2023)

The following figure shows the configuration of these planets. Especially the planet TOI 700 e orbits within the so-called optimistic habitability zone.

4 planets orbit the star with period from 9 to 37 daysshorter for closer planets and longer for more distant ones. Exactly TOI 700 and is the most distant and the last to be discovered.

Given the frequency with which new exoplanets are being discovered, we expect it won’t be long before we know what the first newborn will be in 2024!


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