A planetary hunting satellite has discovered its smallest planet to date – and its size is identical to that of the Earth.

A new Earth-size exoplanet, dubbed HD 21749c, has been identified by scientists, according to an article in the journal Astrophysical Journal Letters.

This discovery is particularly new given the difficulty of finding planets the size of the Earth; generally, when it comes to looking for exoplanets, the largest are the easiest to find, and most of the exoplanets discovered are either gaseous giants or "super-Earth", rocky planets much more gravitational than our Earth and probably much less uninhabitable.

The discovery of HD 21749c is exciting in that it is comparable to Earth – but not at surface temperature or other conditions. With surface temperatures approaching 800 degrees, HD 21749c is unlikely to be habitable by life as we know it. The planet gravitates around the HD 21749 star and bypasses it every 7.8 days. Located just 53 light-years from Earth – in galactic terms, just a few houses away – it's the smallest outside world to our solar system that was discovered by the Transiting Satellite Exoplanet Satellite Survey (TESS) from NASA, although it is not the smallest exoplanet ever created. discovered. (This distinction belongs to Kepler 37b, a world the size of Mercury discovered by the Kepler Space Telescope, which has now disappeared).

The discovery suggests that TESS is capable of fulfilling its mission to create a catalog of thousands of planets that can be the size of the Earth, the host life or both.

TESS works by trying to observe the shadows of the planets passing in front of the stars. The partial eclipses created by these exoplanets as they pass between their host stars and we create a temporary and predictable hollow in the amount of light emitted by their parent stars, that TESS can detect. Careful observation of the reduction of the light produced by the star and the duration of the gradation can reveal many details about the mass, the orbital period and the size of these exoplanets.

Earlier in the month, as reported by Salon, a team of astronomers from Cornell, Lehigh University and Vanderbilt University published an article in the journal Astrophysical Journal Letters on creating a detailed catalog titled " TESS Habitable Zone Star Catalog ", consisting of 1,822 stars where planets could exist and that TESS could theoretically detect. Scientists believe that almost all stars in the sky are surrounded by planets.

Padi Boyd, scientist of NASA's TESS project, told Salon that this catalog is important because it has synthesized the data to a point where it can be hand-picked by scientists. This allows them to search for signals in a way that computer automation could not.

"This catalog is a little different, it looks at all the stars that TESS can see and looks for a subset of stars around which the TESS telescopes themselves – the instruments themselves – could detect the transit of 39 a small planet, one or two small passages, and this planet would be in the habitable zone of its star, "Boyd said. "This is the catalog we already have and the selection of what some people would consider to be the most interesting stars around which to search for planets."

The recently discovered exoplanet shows that the filtering system listed candidates for the solar system works.

Until 1995, we did not know if there were planets in other solar systems, because this sensitive sensing technology did not exist yet. Since then, 4,000 exoplanets have been discovered and there are nearly 3,000 possible candidate exoplanets based on existing data. NASA estimates that since the discovery of the first exoplanet in 1995, the number of known exoplanets has doubled every 27 months.