Second-closest 'super-Earth' found orbiting sun's stellar twin

Pablo Tucker
November 16, 2018

Even if the other potential planets turn out to be busts, the one that does appear to be there would be close enough to us, and far enough from Barnard's star, that we could image it directly using hardware that should come online within the next decade.

It circles a cool red-dwarf star, smaller and older than the sun, completing one orbit every 233 days.

By crunching a wealth of data gathered by many different observational efforts, the scientists believe that the planet orbiting the dim star is a big ball of rock much like Earth, only significantly larger. This method takes advantage of that fact that not only does a star's gravity obviously influence the planet orbiting it, but the planet's gravity also affects the star in turn.

The team, led by Ignasi Ribas of the Institute of Space Studies of Catalonia (IEEC) and Institute of Space Sciences (IEEC-CSIC), dubbed the planet candidate "Barnard's star b", or GJ 699 b.

The planet actually orbits much closer to Barnard's star than Earth does to the sun, but because the red dwarf puts out much less energy than our star, conditions are likely cold and shadowy on the surface at all times.

The planet, Barnard's Star b, is about as far away from its star as Mercury is from the Sun. "Barnard's star is the "great white whale" of planet hunting".

"We knew we would have to be patient".


That seemed to be the case when a team of researchers started checking archival data for Barnard's star images.

"We used observations from seven different instruments, spanning 20 years of measurements, making this one of the largest and most extensive datasets ever used for precise radial velocity studies." explained Ribas. Alpha Centauri's triple-star system (including Alpha Centauri A and B, plus Proxima Centauri) are the only stars nearer.

This technique sees scientists look for a "wobble" in the light frequency coming from the star as the planet transitions across the face of it.

The planet, designated Barnard's Star b, now steps in as the second-closest known exoplanet to Earth.

This chart shows the location of Barnard's Star within the constellation of Ophiuchus, straddling the celestial equator, and marks most of the stars visible to the unaided eye on a clear dark night.

A recent almost-discovery of so-called "super Earth" could change that. When the star moves away from the Earth, its spectrum redshifts; that is, it moves towards longer wavelengths. This is because it's moving quickly in relation to the sun, and it's the nearest single star in the sky to us, Butler said.

It is, however, closer to its parent star at a distance only 0.4 times of that between Earth and the Sun. Worse, the method used to find the exoplanet means taking spectra of the star, spreading its light out into thousands of individual colors.


The final push came when Ribas's team made a decision to launch an intensive observing campaign from 2016 to 2017 aimed at confirming the suspected planet using CARMENES, a new planet-hunter spectrograph at Calar Alto Observatory in Spain.

It's unlikely that there is life on this probable planet, given the distance from its star.

Vogt said, '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.

"We all have worked very hard on this result", said co-leader Guillem Anglada-Escude at Queen Mary University of London.

The star is named after the American astronomer E E Barnard, who measured properties of its motion in 1916.

"The new planet is impossible for Peter van de Kamp to have detected". It is worth noting, however, that the measurements place the planet at a similar period to van de Kamp's claims in the 1960s.

Given how close the exoplanet is to our solar systems, future missions and telescopes should be able to provide more insight into the composition of the surface, and the atmosphere of the planet.


These methods haven't always been available to astronomers searching for exoplanets.

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