Finding an Earth-like planet in our cosmic neighborhood would be a momentous discovery, likely humankind’s greatest. Precisely for this reason, astronomers focus their attention on the star systems closest to us in search of extrasolar planets that meet these characteristics. The news that the astronomers of the European Southern Observatory (ESO) they discovered a rocky exoplanethaving a mass equal to half that of Venus, around the Barnard’s starthe closest single star to Earth, about 6 light years. The planet, called Barnard bis twenty times closer to Barnard’s star than Mercury is to the Sun, which is why its surface temperature is 125°Ctoo high to allow liquid water on its surface. The discovery, made through the Very Large Telescope (VLT) at Cerro Paranal, in Chile, shows us how astronomical technology has made giant strides in the search for extra-solar planets, even reaching detect objects smaller than Earthlight years away from us.
Barnard b’s discovery: details of the study
Despite a promising detection in 2018, no planets orbiting Barnard’s Star had been confirmed until now. The new study published in the journal Astronomy and Astrophysics by ESO astronomers finally reports the discovery of this exoplanetrenamed Barnard b.
Barnard b makes aalmost circular orbit around the parent star to one distance which is about 20 times less than that of Mercury from the Sun (58 million km), employing suns 3.15 Earth days per orbit. The proximity to the star, just inside the habitability range which indicates the possibility of liquid water on the surface, causes the surface temperature of the exoplanet is approximately 125°Ctoo hot therefore to ensure liquid water on the surface. The planet has a mass which is about the half that of Venusor equivalently three times that of Marsand therefore represents one of the smallest mass exoplanets ever discovered.
The data analyzed by astronomers also suggests the presence of others three exoplanet candidates around Barnard’s star, but further observations with the ESPRESSO spectrograph will be necessary to confirm this second result. The discovery of this exoplanet, together with those of similar exoplanets around Proxima Centauri, demonstrate that the Our cosmic backyard is full of low-mass rocky planets.
Where is Barnard’s star located
The importance of Barnard’s star resides in its position. In fact it is the single star closest to the Sunapproximately distant 6 light years. It is the second closest star system to us after the triple system of Alpha Centauri A&B and Proxima Centauri about 4 light-years. Thanks to its proximity, it represents a primary target in the search for Earth-like exoplanets.

Barnard’s star is one red dwarf in the constellation of Ophiuchus, with one mass of only the 15% of that of the Sun and one temperature superficial of approx 3200 degrees Kelvinwhich gives it its typical character red color of dwarf stars. Its mass and lower surface temperature mean that the habitable rangethe area where there can be liquid water on a planet, is much closer to the star than it is to the Sun. This is why much of the search for Earth-like planets focuses on red dwarfs: potentially habitable planets are closer to the star and consequently generate a radial motion of the star larger than the planets on stars similar to the Sun, thus making their detection easier.
How the exoplanet was discovered
The exoplanet Barnard b was discovered thanks to the tool EXPRESSEDone spectrograph mounted on the telescope Very Large Telescope (VLT) from 8.2 meters on Cerro Paranal, in Chile, the best sky in the world for astronomical observations. In order to discover the exoplanet, ESPRESSO uses the radial velocity method. The animation below briefly shows how this method works.
ESPRESSO breaks down the light coming from Barnard’s star into its constituent wavelengths obtaining what in jargon is called a spectrum. Each chemical element emits in a specific wavelength, so the emission or absorption lines in a spectrum they tell us which chemical elements are present in a star. However, if the star is subject to the gravitational attraction of a second body, in this case Barnard b, it it moves back and forth relative to the observer. This little one radial movement shifts the emission and absorption lines of the star’s spectrum by a small amount due toDoppler effect. By knowing which chemical elements produce the lines and measuring the displacements, astronomers can infer details about an exoplanet’s mass and orbit.