Ross 128 b: Nearby Exoplanet Lies In 'Goldilocks Zone' and Could Support Life

At the end of 2017, researchers announced an exciting discovery: An exoplanet named Ross 128 b located "just" 11 light-years from Earth which could potentially be habitable.

Now, research published in the Astrophysical Journal Letters has revealed several characteristics of Ross 128 b—the second closest exoplanet to Earth—which strengthen the case that the planet is capable of supporting life.

For the study, a team of scientists led by Diogo Souto from Brazil’s Observatório Nacional analyzed the planet’s host star—Ross 128—to work out the quantities of different chemicals inside it for the first time.

This type of analysis can help researchers to estimate the makeup of planets that surround stars, enabling them to determine how Earth-like they are.

Ross 128, like 70% of all stars in the Milky Way, is a red dwarf—a class of relatively cool, small stars. Astronomers think that many of these red dwarfs host at least one exoplanet.

In fact, several of the planets that have been discovered around these stars—including Proxima b, the closest exoplanet to Earth, and the TRAPPIST-1 planets—are some of the most promising candidates for scientists searching for signs of life outside the Solar System.

“Until recently, it was difficult to obtain detailed chemical abundances for this kind of star,” Souto said in a statement.

However, a new technique Souto developed himself enabled the scientists to measure the chemical abundances of carbon, oxygen, magnesium, aluminum, potassium, calcium, titanium, and iron in the star using the Sloan Digital Sky Survey’s APOGEE instrument, which can measure near-infrared light—the spectrum in which Ross 128 is brightest.

But how does analyzing the chemical makeup of a star help to reveal details about the planets surrounding it?

When stars are in the early stages of their lives, they are encircled by a disk of rotating gas and dust in which rocky planets form.

The chemistry of the star dictates the contents of the disk, as well as the resulting mineral composition and interior structure of any planets that form within it. For example, the quantities of magnesium, iron and silicon in a planet will influence the ratio of its internal core and mantle layers.

The researcher’s analysis showed that Ross 128 has similar levels of iron to our Sun, while the ratios of iron to magnesium in the star indicate that the core of planet Ross 128 b is likely larger than Earth’s.

Using this new data, the scientists were able to estimate a range for the planet’s radius—something which can’t be measured directly because of the way the planet is oriented around the star. These estimates indicate that the planet should be rocky like Earth and not composed of gas, like Neptune or Jupiter.

eso1736a-800x800 This artist’s impression shows the temperate planet Ross 128 b, with its red dwarf parent star in the background. ESO/M. Kornmesser.

Lastly, knowing the radius of Ross 128 b enabled the team to work out how much light and heat from its host star is reaching the planet. Their findings showed that it is likely a temperate planet that lies within the "Goldilocks Zone"—the habitable region around a star where the temperature is just right for liquid water to exist on the surface, a condition essential to life as we know it.

“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,” Souto said.

“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.”

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