Astronomers discover frozen planet orbiting the fastest star in the sky

14 November 2018

Astronomers from the University of Hertfordshire have identified the presence of a new planet orbiting Barnard’s star - a red-dwarf star smaller and older than our sun - and its existence has been proven by an international team of researchers, as reported today (Wednesday 14 November) in the journal Nature.

The new planet, named Barnard’s star b is a super-Earth, with a minimum of 3.2 Earth masses. It orbits Bernard’s star every 233 days near the snow-line, a distance where water would be frozen.

Professor Hugh Jones, from the University of Hertfordshire and a co-author on the paper, said: 'The announcement of the planet has been a long time in the making; initial observations of the planet were made by Dr Paul Butler at the Carnegie Institution of Washington in June 1997. My colleague Dr Mikko Tuomi had discovered the planet's fingerprints in archival data in 2015 and we first submitted a scientific paper presenting the planet’s existence back in March 2017. However, we didn’t have enough evidence to conclusively support such a major discovery.'

The Red Dots collaboration

Since the planet’s initial detection, an international effort called the Red Dots collaboration – led by Guillem Anglada-Escude at Queen Mary University of London and formerly based at the University of Hertfordshire – has been monitoring Barnard’s star with high precision instruments to investigate the signal. This used the Doppler effect* to measure the changes to the star’s light that are caused by the proximity of a planet. A clear signal at a period of 233 days arose again in the re-analysis of all the measurements combined. This signal implies that Barnard’s star is approaching and moving away from us at about 1.2 m/s — approximately the walking speed of a person — and it is best explained by a planet orbiting it.

'These major observing campaigns gave us enough observations to confirm the planetary signal with several independent datasets and with the variety of different signal analysis tools that we had built at the University of Hertfordshire,' said co-author Dr Fabo Feng.

Barnard's star

Barnard’s star was discovered in 1916, is six light years away from the Sun and is the second closest star system to the Sun after the Alpha Centauri system. It has long captured the attention of astronomers, science fiction authors, filmmakers and game developers as a promising location for an orbiting planet. It is the fastest moving star on our sky traversing the full moon in 174 years. This might not seem like much and explains why for most of human history it was thought that the positions of the stars were fixed but – to modern astronomers – Barnard’s Star is virtually zipping across the sky. Additionally, because it is among the least active red dwarfs known it is an ideal target search for exoplanets with various methods.

As this planet is outside the ‘habitable zone’ and in the ‘snow-line’ of Barnard’s Star (akin to the location of the asteroid belt in our own solar system) it is far away enough from its star to be directly imaged, by using instruments on space missions planned to launch in the next few year and also with observations from the current European Space Agency mission Gaia.

Dr Mikko Tuomi, who originally discovered the planet, said: 'The ability to directly image a planet greatly increases our ability to understand its characteristics and increase the potential for possible exploration in future, helping astronomers discover more about the planets that lie beyond our solar system.'

The project was funded by a grant titled PANDORA (PAN-Disciplinary algORithms for data Analysis) to Professor Hugh Jones from the Leverhulme Trust and by the Science and Technology Facilities Council through its support for the European Southern Observatory and a consolidated grant for astrophysics research to the University of Hertfordshire.

Main image: This image shows an artist’s impression of the planet’s surface. Credit: ESO - M. Kornmesser. Licence: Creative Commons with Attribution, https://creativecommons.org/licenses/by/4.0/

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