Earth finds potential celestial sister

Laura Zhang

Scientists may have just found Earth’s long-lost twin.

After years of data collection, astronomers recently discovered Proxima b, the closest planet to the Milky Way located in the habitable zone, a temperature where liquid water could exist.

According to Michael Endl, co-discoverer of Proxima b and research scientist in the UT Department of Astronomy, Proxima b’s proximity to Earth facilitated its discovery. 

“The excitement comes now, for the general public and for us astronomers, with all these questions about how this planet really looks and what the conditions are and whether it has life or not,” Endl said. “These are now questions that can possibly be answered in the next ten to twenty years.”

So far, scientists only know Proxima b’s minimal mass, as well as its orbital velocity. The minimal mass is a highly accurate estimation of a planet’s mass that includes a margin of error based on unpredictable factors such as angles of measurement.

Though merely speculative right now, Proxima b is most likely to have a rocky, Earth-like terrain, although not much else is known about its atmosphere, said Endl. 

The researchers, who collaborated as part of the international Pale Red Dot Campaign, detected the planet indirectly by looking at the wobble, or oscillation, of the mother star, Proxima Centauri. 

All bodies in the solar system revolve around its center of mass, which is most often found directly in the center of the star. However, a planet can shift the center of mass out from the exact center of the star to the surface, causing a wobble.  

“The more massive the planet, the more the center of gravity will move from the center of the star and the easier it is to measure,” Andrew Mann, Hubble Fellow in the Department of Astronomy, said. 

However, the discovery of a planet does not necessarily indicate the presence of life forms, Mann added.

David Hoffman, associate professor in the Department of Molecular Biosciences, said several problems stand in the way of habitability.

Proxima b orbits Proxima Centauri, the nearest star to the Sun. Proxima Centauri is classified as a red dwarf, which means it is lower in energy than the Sun, a yellow dwarf. 

According to Hoffman, Proxima b is closer to Proxima Centauri than Earth is to the Sun. This means that the surface of Proxima b is more prone to spontaneous solar flares, or brief eruptions of high-energy radiation from the sun’s surface.

“It’s a property of red dwarfs, like Proxima Centauri, that they don’t have constant energy output,” Hoffman said. “Unlike our sun, which is almost uniform in its energy output, things can get fried.” 

Another issue is that Proxima b may be tidally locked, meaning the same side of Proxima b faces the star at all times.

“Instead of having a uniform temperature, the planet probably has a really hot side and a really cold side,” Hoffman said. 

According to Endl, further research of this planet will focus on understanding orbit paths of the planet in front of the host star and developing the next generation of instruments. 

One such instrument, the Giant Magellan Telescope, is a cutting-edge $1 billion telescope located in the Chilean desert that will help with further research on the planet once it is finished in the mid-2020s. UT serves as one of its international partners. 

After establishing Proxima b’s characteristics, researchers might be able to identify its potential life forms, said Endl.

“‘If biology could answer the question of how to make life, then once that starts, life will find a way to survive.’ I think that’s a quote from Jurassic Park,” Endl said.

Certain forms of life may exist on Proxima b, such as microbes that can survive extreme conditions, many of which have been found to exist on Earth, said Hoffman.

“The extraterrestrial life I’m most interested in is microbes because that’s what I think we’re most likely to find in my lifetime. So that’s what I’m rooting for,” Hoffman said. “If you want to understand the chances of life on Proxima b, you have to look at ourselves.”