Chemical Composition of a host star reveals a lot about the orbiting planets and Ross 128 is no exception.

Ross 128b is an Earth-sized exoplanet which was detected on 15th November 2017 by Xavier Bonfils. It created quite a lot of hype among the scientific community as it is the second closest known exoplanet to our solar system. It is 11 billion light years away from the Earth and is considered one of the best candidates for habitability outside our world due to a number of reasons. It receives 38% more sunlight than our planet which means that the temperature on this exoplanet is suitable for existence of liquid water on its surface. It is only 35% bigger than the Earth and astronomers expect it to be rocky in nature because all the previously detected exoplanets that have fewer than 4 Earth masses have been rocky.

The High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph of the European Southern Observatory was used to locate this heavenly body. It orbits a Red Dwarf Star known as Ross 128 and the detailed chemical abundances of this star came forward recently as Diogo Souto of Brazil’s Observatório Nacional led a team of researchers to this discovery. This is an incredibly important information for scientists as they can determine the composition of the exoplanets revolving around it. This, in turn, helps them to predict their similarity with the Earth. Souto tailored a convenient technique for measuring the quantity of different chemicals and mentioned about the significance of his work by saying,

“Until recently, it was difficult to obtain detailed chemical abundances for this kind of star.”

Red Dwarfs are quite common in our galaxy (Milky Way) and an extensive research from astronomers have revealed that a lot of them host at least one exoplanet. The host star of Proxima b, Proxima Centauri, is also a red dwarf. It is the nearest star to our sun. Similarly, TRAPPIST-1 is another famous red dwarf. An interesting thing is that it is only as big as Jupiter but it hosts 7 exoplanets.

The researching team measured the near-infrared light of the Ross 128 to derive abundances of different chemical elements including Carbon, Oxygen, Potassium, Calcium, and Iron. The APOGEE spectroscopic instrument of the Sloan Digital Sky Survey was used for this purpose. Johanna Teske of Carnegie, who was also a part of the researching team, praised this tool in the following words:

“The ability of APOGEE to measure near-infrared light, where Ross 128 is brightest, was key for this study. It allowed us to address some fundamental questions about Ross 128 b’s `Earth-like-ness’.”

In the early phases of a star’s life, it is surrounded by a rotating disk of gas and dust. Planets accrete from that and the chemistry of the star has a role to play in their formation. In case of Ross 128, it was observed that its iron levels are comparable with our sun. Similarly, the ratio of Iron to Magnesium suggested that the core of Ross 128b should be larger than the Earth. Prior information about the minimum mass of the exoplanet proved extremely beneficial for the researchers as they figured out a range for its radius. Due to the oriented orbit of the planet around the star, deducing it directly was simply impossible.

Bulk Density of a planet is a critical calculation which can be used to analyze its composition. What adds to the worth of this study is that mass and radius are important measurements for making this evaluation and scientists now have both of them. Practical experience led astronomers to a conclusion that those exoplanets who have a radii less than 1.7 times Earth’s are likely to be rocky. Contrary to that, the ones who are bigger than that have a gassy layer around them, like what we observe in case of Neptune. The measurement of the temperature of the Ross 128b also showed positive signs to support life. Souto elaborated all that as he said,

“It’s exciting what we can learn about another planet by determining what the light from its host star tells us about the system’s chemistry. Although Ross 128 b is not Earth’s twin, and there is still much we don’t know about its potential geologic activity, we were able to strengthen the argument that it’s a temperate planet that could potentially have liquid water on its surface.”