Announcements about exoplanets, those found outside our solar system, seem almost commonplace in this golden age of discovery for astronomers. So why is Ross 128 b unique — apart from its rather human-sounding name?
The planet is about the same size as Earth, and it may have a similar surface temperature, making it a temperate world that could support life.
Every 9.9 days, it completes an orbit around its host star, Ross 128, which is what’s known as a red dwarf star: They’re the coolest, faintest and most common stars found in the universe.
Because of their plentiful nature and the fact that other exoplanets have been found around these types of stars, red dwarfs are being studied and observed with increasing frequency in the hopes of finding more exoplanets.
Astronomers found Ross 128 and its planet using the European Southern Observatory’s planet-hunting instrument, called HARPS. The High Accuracy Radial velocity Planet Searcher is based at La Silla Observatory in Chile. The astronomers detail their discovery in a new study, published Wednesday in the journal Astronomy and Astrophysics
“To be involved in such a discovery is very rewarding, and it helps to realize that so much effort is worth it,” Nicola Astudillo-Defru, one of the study’s co-authors at the University of Geneva’s observatory, wrote in an email. “The special properties of this system means that we are contributing our bit on the search of a Earth 2.0.”
Other notable discoveries of Earth-size exoplanets in recent years, like the TRAPPIST planets
and Proxima b
, were also found around these types of stars. They are also considered to be among the best hopes for supporting life on planets outside our solar system because they exist within the “habitable zones” of their stars, where liquid water could pool on the surface of the planet and potentially support life as we know it.
The astronomers don’t yet know whether Ross 128 b is in the habitable zone of its star, but it’s likely, given what they understand about red dwarfs and the planets that orbit them.
Ross 128 b is 20 times closer to its star than Earth is to the sun, but because the star is small, dim and cool, the planet would still be at a potentially comfortable temperature. The nature of the star is also why the planet is subjected to only 1.38 times the radiation that Earth receives from the sun, even though the planet and star are close together.
But the reason astronomers are excited about Ross 128 b is because the star is “quiet.” Other red dwarfs, like Proxima Centauri — the star that Proxima b orbits — have a tendency to lash out at their planets with deadly flares of ultraviolet and X-ray radiation.
But Ross 128 doesn’t seem to be doing this, so it’s considered “quieter,” which means the planet is a more comfortable place for life to form without being subjected to such violent episodes from time to time.
Proxima b is currently the closest exoplanet to our solar system ever discovered, at a distance of 4.2 light-years. Ross 128 b could change this, because the planet and its star are moving toward us.
“A detailed study
investigated the movement of our stellar neighbor by combining data from the Hipparcos satellite and ground-bases velocimeters,” Astudillo-Defru said. “They list all the close encounters with other stars, and because of the relative movements of stars and the Sun, it results that Ross 128 will be our closest star.”
Astronomers estimate that in 79,000 years, Ross 128 b will be our exoplanet neighbor, even closer than Proxima b. That may sound like a long time, but in a universe that is billions of years old, it’s merely a cosmic moment.
The astronomers believe that Ross 128 b is a good candidate for further study when the European Southern Observatory’s Extremely Large Telescope can begin searching the atmospheres of exoplanets for biomarkers in 2025.
“I plan to continue searching for new worlds, specially around Ross 128 because it is likely that there are more planets,” Astudillo-Defru said.