This is not the first time that Barnard's star has been the focus of attention for exoplanet-hunting astronomers.
It circles a cool red-dwarf star, smaller and older than the sun, completing one orbit every 233 days. But the methods we've used to detect a lot of them are biased toward finding large planets that orbit close to their host stars. Light from Barnard's Star provides its planet with only 2% of the energy the Earth receives from the Sun.
There is hope the planet could have a thick atmosphere trapping some heat, but astronomers say it's located beyond the "snow line" where any water on the surface is probably frozen. However, other teams were unable to confirm, and by the 1970s we knew the discovery was merely a product of defective instruments.
This is the first time that this technique has been used to detect a planet this small so far away from its host star. Though it is extremely close, Barnard's star is too faint to be seen with the naked eye'. Alpha Centauri's triple-star system (including Alpha Centauri A and B, plus Proxima Centauri) are the only stars nearer. With the Doppler effect, as a planet orbits a star, the planet's gravitational pull causes its star to wobble a little bit.
This image shows an artists's impression of the surface of Barnard's star b, a cold Super-Earth discovered orbiting Barnard's star 6 light-years away. While the star itself is ancient - probably twice the age of our Sun - and relatively inactive, it also has the fastest apparent motion of any star in the night sky. That's hard to do because, viewed from Earth, the planet is close to the star and swamped by its glare. As the star moves towards the Earth its spectrum appears slightly shifted towards the blue and, as it moves away, it is shifted towards the red. The timing of the signal indicates that the planet orbits at about the same distance as Mercury orbits our Sun.
To find this cold Super-Earth, the team-which included Carnegie's Paul Butler, Johanna Teske, Jeff Crane, Steve Shectman, and Sharon Wang-combined 20 years of data from seven different instruments, all of which were "stitched" together to form one of the largest and most-extensive datasets ever used for this method of planet detection.
In 1997 the team started scanning Barnard's star using the Keck Observatory's HIRES instrument, which was designed by Vogt himself. The study found that at its distance from its star, any water on the planet would be frozen.
"It is the most common type of star in the galaxy-over 70 percent of Milky Way stars are like this dim, M dwarf star", Vogt said. Their analysis suggested there might be a signal of something orbiting with a 230 day period, but the data suffered from what the researchers term "very poor sampling".
"It´s important because it´s really our nextdoor neighbour and we like to meet our neighbours in general", Ignasi Ribas, from the Institute of Space Studies of Catalonia and Spain´s Institute of Space Sciences, told AFP. "This is the result of a large collaboration organized in the context of the Red Dots project, which is why it has contributions from teams all over the world including semi-professional astronomers coordinated by the American Association of Variable Star Observers".
"Difficult detections such as this one warrant confirmation by independent methods and research groups", Rodrigo Diaz, an astronomer at the University of Buenos Aires who was not involved in the research, wrote in a commentary for Nature.
Back in the 1960s Peter van de Kamp, a Dutch astronomer based in the United States, reported the discovery of two planets roughly the size of Jupiter orbiting the red dwarf.
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