‘Nearby’ Multiplanet System Offers Astronomers Big Study Opportunities

Artist’s impression of a planet with two exo-moons orbiting a red dwarf star. (NASA / Harvard-Smithsonian Center for Astrophysics / D. Aguilar – http://www.nasa.gov/sites/default/files/reddwarfplanet_cfa_full_1.jpg, Public Domain, Link

(CN) — Astronomers have discovered a red dwarf star — approximately half the size of the sun that lies 11 light years away from us — exists within a multiplanet system, making it the closest to our solar system ever seen, according to research revealed Thursday.

According to a paper by Sandra Jeffers, a lecturer at the Institute for Astrophysics at Goettingen University in Germany, the system surrounding the red dwarf GJ 887 contains two or three super-sized exoplanets similar in size to Earth.

The authors hope that with this discovery, the opportunity will be greater than ever for studying exoplanet atmospheres. This is further made possible with the James Webb Space Telescope, an orbiting infrared observatory built by NASA to extend the Hubble telescope’s research and observe dust clouds where stars and planets form.

GJ 887 is host to the nearby system and is one of the larger ones found thus far. It belongs to the most common family of stars that makes up most of the star population and has a life expectancy of trillions of years — making it the longest lived type, likely due to its relatively low surface temperatures.

Also thanks to their sustainable temperatures compared to other stars, they burn through their hydrogen supply at a much slower rate, which further extends their lifetimes until they collapse and superheat into a white star.

Scientists have found several red dwarfs surrounded by a host of exoplanets, or planets that sit outside the solar system, and their dim appearance makes it easier for experts to find nearby planets. This makes red dwarfs popular with NASA, and targets that allow them to hunt for more Earth-like planets and create projects with this goal, like the Transiting Exoplanet Survey Satellite (TESS).

“Red dwarfs are plentiful (about three-quarters of all the stars out there) and the planets orbiting them are easier to observe because the stars are so small compared to our sun and so an Earth-sized planet blocks a greater fraction of starlight,” said journalist Marc Kaufman in a Many Worlds column on red dwarfs. “Because planets orbiting red dwarfs are much closer in to their host stars, the observing geometry favors detecting more transits.”

One notable potentially habitable planet orbiting a red dwarf was found in 2016, when astronomers found an Earth-sized planet orbiting Proxima Centauri, our closest star. More have been discovered since then, including a recent find in January of an exoplanet confirmed to be in its star’s habitable zone.

“TESS was designed and launched specifically to find Earth-sized planets orbiting nearby stars,” said Paul Hertz, astrophysics division director at NASA Headquarters in Washington in a January statement. “Planets around nearby stars are easiest to follow-up with larger telescopes in space and on Earth.”

In this study, Jeffers used a popular technique for discovering exoplanets, in which they use Doppler measurements to track a star’s motion in order to detect any gravitational pull from planets orbiting around it.

The team observed GJ 887 for three months, studying its movements and gathering pertinent data. By combining their results with previous measurements of the star taken over the span of 20 years, they discovered two super-Earth sized exoplanets and possibly a third.

These exoplanets circle the red dwarf in a tight formation and orbit every 9.3 days and every 21.8 days respectively. The suspected third planet is farther out, and likely has an orbital period of about 50 days.

The authors believe that the first two exoplanets are too hot to sustain liquid water on the surface, similar to the planet Venus. The possible third exoplanet, however, sits much farther out and holds promise as it may exist within the red dwarf’s habitable zone, or the designated region outside a star where liquid water can form.

GJ 887 has shown far less activity than other known red dwarfs, which suggests that these newly discovered planets may not experience the damaging solar flares as seen with other similar stars. Normally, red dwarfs emit smaller but still significant solar flares that can strip away at a planet’s atmosphere, and the UV rays that accompany a flare can impede life from thriving on the surface.

“If someone had to live around a red dwarf, they would want to choose a quieter star like GJ 887,” writes Melvyn Davies, professor of astronomy at Lund University, in a related perspective. “If further observations confirm the presence of the third planet in the habitable zone, then GJ 887 could become one of the most studied planetary systems in the solar neighborhood.”

Getting to GJ 887 for hands-on studying will prove difficult, however. With current technology, it would take well over 1,000 years to get there — and probably much, much longer.

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