New discovery: 26 light-years from Earth, a rocky planet 2.8 times the size of Earth has been discovered

On March 5, 2012, scientists from the Max Planck Institute for Astronomy published a study in the scientific journal in which they took full advantage of the radial velocity method and lunar observations to discover a new Earth-like planet about 26 light-years away from Earth, one with a radius about 1.3 times that of Earth and a mass about 2.81 times that of Earth. It revolves around its host star every 1.5 days. Its host star is a red dwarf smaller than the Sun.

This discovery of an Earth-like planet was made using the radial velocity method and the sunset observation method, which are the two main methods used to find exoplanets. The radial velocity method is based on observing the redshift and blueshift in the star's spectrum. According to scientists, if there is a larger planet around the star, its gravity will disturb the star and make the star oscillate, and the oscillation will make the star's spectrum undergo the Doppler effect, that is, the absorption and emission lines in the spectrum will appear periodic redshift and blueshift.

So, based on this redshift and blueshift, we can infer the presence of planets around the star and determine the center of motion of the planets. Then, in combination with the mass of the star, the mass of the planet can be inferred. This is the radial velocity method to find exoplanets, but the radial velocity method has the disadvantage that the planets found are gas giants like Jupiter. Rocky planets like Earth are so small that they do not have enough mass to make the star wobble, so it is difficult to use this method to find rocky planets like Earth.

In this study, the researchers focused on a class of stars smaller than the Sun, namely red dwarfs, which have a smaller mass, so smaller planets would have a greater chance of making them wobble. Since 2016, scientists from the Max Planck Institute for Astronomy in Germany have been systematically observing red dwarfs around our solar system, and in their observations, they have also made a very interesting statistic.

There are 357 main sequence stars in the solar system within 32.6 light years, and 283 of these 357 main sequence stars are considered red dwarfs. So from this data, red dwarfs are indeed a class of stars that exist more in the universe. Among these 283 nearby red dwarfs, one of them is about 26 light-years away from Earth, and it is labeled as Gliese 486, and the radial velocity phenomenon is found in the spectrum of this red dwarf. So this suggests that there are likely planets in the vicinity of this red dwarf, and thankfully, in addition to radial velocity, it also has a sunburst.

As we mentioned earlier, in addition to the radial velocity method for finding exoplanets, there is also the sunset observation method. Sunburst observations are based on observing changes in the brightness of a star to find exoplanets. When there is a planet around the star, and its orbit is approximately the same as our line of sight. Then when it moves in front of the star, it blocks part of the star's light, making it less bright. This is the lensing observation, and when the radial velocity is observed, then the lensing observation can be used to further verify it, so this study, after observing the radial velocity, and then based on the verification of the lensing observation, the researcher finally determined the existence of this planet, which is named Gliese B.

Based on the mass of the star and the redshift and blueshift of the spectrum, as well as the brightness variation of the transiting phenomenon, the researchers deduced the existence of this planet. The researchers have calculated the mass-radius and the center of rotation of the planet, which is 2.81 times the mass of the Earth and about 1.3 times the radius of the Earth. So based on this volume and mass, we can know that its density is similar to that of the Earth, indicating that it is also a rocky planet like the Earth, but based on its orbital radius, its surface environment should be closer to that of Venus, and based on its orbital radius, its distance from its host star is only 2.6 million kilometers. So at such a distance, its surface temperature may have reached a high temperature of more than 430 degrees Celsius, and its surface may be littered with flowing lava.

The chances of life on its surface in such an environment should be almost zero, but such conditions also have an advantage in that they create conditions for researchers to study the atmospheres of exoplanets. While we determine the physical parameters of planets, i.e., mass, volume, and orbital radius, based on the radial velocity method and the lunar observation method, it is difficult to speculate on the composition of planetary atmospheres and atmospheric elements. But this newly discovered planet provides the conditions, because its surface is very hot, and then it heats some elements of the atmosphere, and the heated elements appear as bright streaks opposite to the absorption lines, i.e. emission spectra. So by detecting the emission spectrum, researchers can speculate on the composition of the planet's atmosphere, and then we can learn whether the planet contains the elements needed for life, and thus determine whether it has a chance of harboring life.