A SECOND planet could be orbiting the closest star to our Solar System

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Scientists have discovered what they believe is a second planet orbiting the star closest to our Solar System, Proxima Centauri.

Observations of light readings from Proxima Centauri by an international team revealed a low-mass candidate planet orbiting around it, approximately half the size of Neptune.

Data suggests this planet candidate – provisionally named ‘Proxima c’ – completes an orbit of Proxima Centauri every 5.2 years.

It may be a ‘super Earth’ with a mass higher than our home planet but lower than ice giants Uranus and Neptune.

The research team are hopeful that the relative proximity of the planet makes it one of the best candidates for study to understand planets planet outside the Solar System – known as exoplanets.

The discovery is another exciting step closer to finding alien life in other solar systems. 

‘The proximity of the planet and its orbit at a relatively great distance from its star, means it is one of the best possible chances for direct observations that will enable detailed understanding of another planet,’ said Hugh Jones, Professor of Astrophysics at the University of Hertfordshire.

The new discovery is in Alpha Centauri, our neighbouring planetary system.

Alpha Centauri is a triple star system, consisting of three stars – Rigil Kentaurus, Toliman and Proxima Centauri.

Of these, Proxima Centauri is the nearest star to the Solar System, at a distance of 4.2 light years.

A previous study of Proxima Centauri using the Atacama Large Millimeter Array – an astronomical observatory in northern Chile – reported an unknown source of light spectrum signals that could belong to a second planet, or alternatively just the product of a neighbouring galaxy or an unrelated phenomenon.

To better understand if the signal originated from another planet orbiting the star, Mario Damasso at the INAF-Astrophysical Observatory of Torino and his colleagues analysed a 17.5-year-long time series of high-precision radial velocities using an exoplanet detection method that tracks a star’s light spectrum.

They found the signal occurs over a 1,900-day period, suggesting it’s likely unrelated to cyclical shifts in the star’s magnetic field.

While analysis of cyclical changes in the light spectrum of Proxima Centauri has suggested evidence of a second planet, Proxima c’s status as a planet is yet to be confirmed. 

If it is, Proxima c may provide insight into how low-mass planets form around low mass stars. 

Proxima Centauri, which has a diameter about one-seventh of the Sun, became famous in 2016 with the discovery of its orbiting planet, Proxima b, by the European Southern Observatory.

Proxima b is the closest known exoplanet to our Solar System and was the first confirmed planet to orbit Proxima Centauri.

Professor Jones was also part of the discovery of the ‘Earth-like’ Proxima b, which was discovered from the University of Hertfordshire’s Bayfordbury Observatory.  

‘We first submitted a paper presenting Proxima b’s existence back in February 2013 though it was not until 2016 that we had enough evidence to conclusively support such a major discovery,’ Professor Jones said.

‘Our continuing observations and improved data processing has allowed us to discern the signal of Proxima c.

‘We look forward to confirming the signal with new facilities and finding out how similar or different from our Solar System planets Proxima c really is.’

This new planet is estimated to orbit Proxima Centauri at a distance that is around 1.5 times further than Earth is from our sun.

Proxima c might become a possible target for more direct study by the Breakthrough StarShot project, which is set to be humankind’s first attempt to travel to another star system.

Breakthrough StarShot was founded by Stephen Hawking, Facebook CEO Mark Zuckerberg and Yuri Milner, co-founder of Russian internet company Mail.Ru.

The project aims to demonstrate proof of concept for ultra-fast light-driven ‘nanocrafts’ – tiny spacecrafts – and lay the foundations for a first launch to Alpha Centauri within the next generation 

The international team have detailed their observations of ‘Proxima c’ in the Science Advances.

The authors include researchers from the INAF Astrophysical Observatory of Turin, the University of Crete, Queen Mary University of London and the University of Hertfordshire.

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