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Artist concept of Ross 128B, orbiting a red dwarf star just 11 light-years away. Image via ESO / M. Kornmesser.
Of all the exoplanets discovered today, some of the most exciting – if not the most important – are the ones that could be Similar to the earth. Astronomers find a growing number of rocky worlds, the size of the Earth or a little larger. Some orbit in the "habitable zones" of their stars, where temperatures (among other factors) could allow liquid water to penetrate their surface.
One of the most fascinating is a planet called Ross 128B, orbiting a red dwarf star located just 11 light-years away. It is currently the second rocky planet closest to our solar system. A peer-reviewed study published in The astrophysical journal Last summer (June 13, 2018) shows how much such a world may look like the Earth in some ways, but not really to Earth double.
By studying Ross 128b – an exoplanet so close and so similar to the Earth – scientists hope to better understand how many of these planets are in our galaxy and how many could support their lives.
The new work comes from a team led by astronomers Diogo Souto from the Observatório Nacional in Brazil and Johanna Teske from Carnegie Observatories in California. They studied the chemical abundances in the star host of this exoplanet, star Ross 128. In doing so, they said that they could have a better idea of the elements present in the orbiting planets of the star (or planets around other stars). This knowledge came easily, as Souto briefly noted:
Until recently, it was difficult to obtain detailed chemical abundances for this type of star.
How many earth-like worlds do they exist? We do not know it yet, but scientists are getting closer to the first ones. Image via ESO / L. Calçada / wikimedia, CC BY-ND.
The research team used the APOGEE spectroscopic instrument of the Sloan Digital Sky Survey to measure infrared light from Ross 128, which provided data on the abundance of carbon, oxygen, magnesium, aluminum, potassium, calcium, titanium and iron in the star. As Teske explained:
APOGEE's ability to measure near-infrared light, where Ross 128 is the brightest, was essential for this study. This allowed us to address some fundamental questions about the nature similar to that of Ross 128 b.
It turns out that Ross 128 has iron levels similar to those of our own sun, even though Ross 128 is a red dwarf star. In addition, the ratio of iron to magnesium in the star indicates that the nucleus of the planet is probably larger than that of the Earth.
In terms of size, although it is not possible to directly measure the radius of the planet, because of the orientation of the planet's orbit as seen from Earth, researchers have been able to determine range for the radius, using the known minimum mass of the planet and (now) the stellar chemical abundances.
They found that the radius's estimated reach supported the likelihood of the planet being rocky, like Earth, with a mixture of rock and iron.
Ross 128b was discovered in 2017 by astronomers using ESO's High Precision Radial Velocity Planes (HARPS) search engine. Image via ESO.
Planets with a radius greater than 1.7 times that of the Earth are probably more like Uranus or Neptune – the ice giants of our solar system – with deep atmospheres surrounding a smaller nucleus. Planets whose radius is less than this one are most likely to be rocky, like the Earth. This includes many super-lands, a kind of rocky planet larger than Earth but smaller than Uranus or Neptune, many of which have been discovered so far.
The researchers were able to determine the mass, the radius of action and the probable chemical composition of Ross 128 b. What about the temperature? The team measured the temperature of the star and combined this data with the estimated radius. This told them how much light the star had to reflect on the surface of Ross 128 b – the results showed them that the planet probably had a mild climate, like on Earth. Souto commented:
It is interesting to know what we can learn on another planet by determining what the light of its host star tells us about the chemistry of the system. Although Ross 128b is not the twin of the Earth and we do not yet know much about its potential geological activity, we have been able to reinforce the argument that it is a temperate planet that could have liquid water on its surface.
The Ross 128b also orbits within the habitable zone of its star, so if other conditions are suitable, as well as the temperate temperature, the planet could then have liquid water on its surface. We do not know enough yet to make this kind of determination.
Whatever the case may be, finding another rocky planet with at least some similarities to the Earth is an exciting discovery, showing that there are probably many planets of this type.
The Global Habitability Lab currently lists 55 exoplanets known to be potentially habitable, including the best candidates, and Ross 128b. Image via PHL @ UPR Arecibo (phl.upr.edu) July 2, 2018.
Ross 128b was first discovered in 2017 with the ESO (HARPS) High Speed Radial Speed Search System. It is the second temperate rocky world closest to our solar system (so far), with only Proxima b known to be closer.
Ross 128b is intriguing in many ways, but it's just one of many worlds that are growing. The catalog of habitable exoplanets currently lists 55 potentially habitable exoplanets, including Ross 128 b. They are rocky worlds and similar in size to the Earth. Although many details are still not known about them, the information we To have up to here indicates that they are potentially habitable, by terrestrial standards.
Astronomers are convinced that many more will be found in the months and years to come, including the new mission of the TESS Space Telescope, which has just reached the first light. Ross 128b provides valuable clues about what some of these worlds may be.
Bottom line: Ross 128B may not be the exact twin of the Earth, but it seems to share similarities with our own world. And it is nearby, only 11 light-years away. In the student and in other similar rocky worlds, scientists hope to understand how many of these planets may be in our galaxy and how many may be able to support life.
Source: Star and Planetary Characterization of the Exoplanetary System Ross 128 by APOGEE Spectra
Via Eurekalert
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