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Red Dwarf Star Proxima Centauri Has Regular Starspots Cycle, More Sun-Like Than Earlier Thought

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Defying long-held assumptions that Proxima Centauri — the nearest star to our Sun — has no Sun-like features, new research shows that the red dwarf star actually has Sun-like stellar activity cycles known as starspots cycles.

The European Southern Observatory had announced in August that Proxima Centauri hosts an exoplanet by the name Proxima b, which is more like the planet Earth. 

Earlier, the assumptions say that Proxima Centauri had no Sun-like properties as it was small, cool, has low mass and of low luminosity.

The astronomers were caught by surprise after they detected a stellar activity cycle in Proxima Centauri despite its interior being different from that of the Sun.

The research paper Optical, UV, and X-Ray Evidence for a 7-Year Stellar Cycle in Proxima Centauri, published in the journal Monthly Notices of the Royal Astronomical Society, explains the observations that lasted several years through optical, UV, and X-ray examinations of the star.

They detected the activity cycles from ground-based observations of the All Sky Automated Survey. The Harvard-Smithsonian team studied Proxima Centauri over several years to know if it had a cycle.

"The optical/ASAS data showed a nice 7-year cycle, as well as an 83-day rotation period. When we broke down that data by year we saw the period vary from around 77 to 90 days," lead researcher Brad Wargelin told Universe Today.

According to experts, more studies will be required to understand Proxima Centauri and whether planets orbiting it could actually support life.

What Makes A Starspot?

Starspots are developed as dark blotches on a star's surface. Sunspots have milder temperature than surrounding areas and are led by magnetic fields.

Stars made of ionized gasses called plasma face a constriction in the flow when magnetic fields are created and they lead to changes in radiation emissions.

Proxima Centauri's activity cycle lasts seven years, unlike Sun's 11-year cycle. The Solar Cycle has been explained as an 11-year period where the Sun experiences changes in the levels of radiation it emits.

Proxima's star spots are too dramatic as one-fifth of the star's surface gets covered with spots, which are relatively bigger compared to the star's size.

"The existence of a cycle in Proxima Centauri shows that we don't understand how stars' magnetic fields are generated as well as we thought we did," noted Jeremy Drake, Smithsonian co-author.

Habitability Factor

However, the study has few details on the potential habitability factor of the planet Proxima b and the impact from Proxima Centauri's activity cycle.

It is surmised that flares or stellar winds caused by magnetic fields can rock the planet and wipe out the atmosphere. In that case, Proxima b may look like the Moon, which, despite staying in the habitable zone has not been able to support life.

"Direct observations of Proxima b won't happen for a long time. Until then, our best bet is to study the star and then plug that information into theories about star-planet interactions," said co-author Steve Saar.

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