The threshold of 5000 exoplanets discovered has been exceeded

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The status of 8707 other planets is currently awaiting confirmation.

Over 5000 exoplanets have been discovered since the 1990s.

5005. That's the number of planets orbiting a star other than the Sun that NASA has confirmed to exist since the very first was detected nearly 30 years ago.

It's not just a number, Jessie Christiansen of NASA's Institute for Exoplanet Science at Caltech in Pasadena said in a statement. Each of them represents a new world that we don't know much about, enthuses the one responsible for keeping the account up to date for the US space agency.

The official NASA records only include exoplanet discoveries that are the subject of peer-reviewed scientific papers and whose existence has been confirmed by multiple detection methods or analytical techniques .

The detection of the very first exoplanet was officially announced on October 6, 1995.

An artistic impression of exoplanet 51 Pegasi b

The hot Jupiter 51 Pegasi b orbits the star 51 Pegasi, located about 40 light-years from Earth. Its discoverers, Michel Mayor and Didier Queloz from the Geneva Observatory, were awarded the Nobel Prize in Physics in 2019 (jointly with James Peebles) for highlighting this astronomical breakthrough.

Astrophysicists classify exoplanets according to several categories. Gas giants, similar to Jupiter and Saturn, are mostly hydrogen and helium. No less than 1578 of the exoplanets discovered so far fall into this category.

The Neptunians, composed mainly of methane and water, are also giants, but icy. 1756 exoplanets discovered to date fall into this category.

There are also so-called telluric, i.e. rocky, planets which are certainly the most likely to support life as we know it. There are two types:

  • Earth type, which is equivalent to a dimension equivalent to one time that of the Earth. We found 185 of them.
  • Super-Earth type, rocky planets more than twice the size of Earth. The census is currently at 1568.

According to the most recent estimates, there are up to 700 million billion rocky planets in the Earth. Observable universe.

Nearly two-thirds of all exoplanets known to date, Earths and super-Earths, are located in the habitable zone of their stars. Despite this abundance, it has until now been extremely difficult to probe the atmospheric conditions and properties of these potentially habitable planets. The entry into service in the coming months of the James Webb Space Telescope promises to revolutionize human knowledge on this subject.

There are several ways to detect planets around stars:< /p>

  • The transit technique is by far the one that has confirmed the presence of the majority of them (76.8%) to date. It consists of detecting a drop in the luminosity of a star when an object passes in front of it;
  • The radial velocity method made it possible to discover 18.3% of them, of which the whole first, 51 Pegasi b. She uses the Doppler-Fizeau effect to achieve this. The movement of a planet around a star induces a slight backward movement of the latter, which is detectable by this effect;
  • The gravitational microlensing technique accounts for 2.6% of discoveries. This effect occurs when a star's gravitational field distorts spacetime, which deflects light from a distant star behind it, like a lens; /li>
  • Direct observation, extremely difficult, allowed 1.2% of sightings. Because they are small and dim, planets are easily lost in the glare of the bright giant stars around which they orbit. However, thanks to current telescopes, there are special circumstances in which a planet can be observed directly. Three Quebecers also participated in the creation of the first direct image of exoplanets. They had received the title of Scientist of the Year 2008 from Radio-Canada for their achievement.

Several terrestrial telescopes (from the European Southern Observatory (ESO), NASA, European Space Agency (ESA), etc.) and space observatories (Kepler, Hubble, CoRot, Spitzer) scan the sky in search of 'other worlds.

In addition to James Webb this year, other telescopes will be added to the list in the coming years. The Nancy Grace Roman space telescope in 2027 and ESA's ARIEL mission in 2029 will join their instruments to find new planets, but also to analyze their atmospheres in search of favorable conditions for the presence of life.

In my humble opinion, it is inevitable that we will find some form of life somewhere – most likely of a primitive type, claims Polish astrophysicist Aleksander Wolszczan. The close connection between the chemistry of life on Earth and that found in the Universe as well as the detection of widespread organic molecules suggests that the detection of life itself is not ;is only a matter of time.

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