Astronomers have found that Barnard’s star — a very close, fast-moving, and long studied red dwarf — has a super-Earth sized planet orbiting just beyond its habitable zone.
The discovery relied on data collected over many years using the tried-and-true radial velocity method, which searches for wobbles in the movement of the host star.
But this detection was something big for radial velocity astronomers because Barnard-b was among the smallest planet ever found using the technique, and it was the furthest out from its host star as well — orbiting its star every 233 days.
For more than a century, astronomers have studied Barnard’s star as the most likely place to find an extrasolar planet.
Ultimately, said Ignasi Rablis of Spain’s Institute of Space Studies of Catalonia, lead author of the paper in journal Nature, the discovery was the result of 771 observations, an extremely high number.
And now, he said, “after a very careful analysis, we are over 99 percent confident the planet is there.”
The planet is at least 3.2 times the size of Earth and orbits near the snowline of the system, where water cannot be expected to ever be liquid. That means is it a frozen world (an estimated -150 degrees Celsius) and highly unlikely to support life.
But Rablis and others on the large team say it also an extremely good candidate for future direct imaging and next-generation observing.
Thousands of exoplanets have been identified by now, and hundreds using the radial velocity method. But this one is different.
“Barnard’s star is the ‘great white whale’ of planet hunting,” said Paul Butler, senior scientist at the Carnegie Institution, a radial velocity pioneer, and one of the numerous authors of the paper.
Because the star is so close (but 6 light-years away) and as a result so tempting, it has been the subject of exoplanet searches for 100 years, Butler said. But until the radial velocity breakthroughs of the mid 1990s, the techniques used could not find a planet.… Read more