Astronomers have discovered evidence of a strange world that can help them better understand the nature of worlds closest to ours.
The proposed new planet is unlike anything in our own solar system, scientists say – bigger than the Earth but less than the Neptune, and far enough from its weak red sun as some water on its surface is locked in ice.
But this frozen "superhero", the second closest exoplanet known for science, is an exciting lead to what might otherwise be out there. And in the not so distant future when telescopes become capable of photographing planets around other stars, it may well be the first new world we see.
"We move from science fiction to science reality," said Carnegie astronomer Johanna Teske, contributing to a study of the new planet published in the magazine Nature. "There is so much opportunity there."
Exoplanet's sun, a small body called Barnard's Star, is one of our closest neighbors. The only stars nearer are the Alpha Centauri system triplet stars. One of these stars, Proxima Centauri, is circulated by a small planet, but the star's tendency to sputter stains of deadly radiation means that the planet is likely not to be habitable.
Barnard's Star has long been "the big white choice" of exoplanet hunting, says Carnegie astronomer Paul Butler, co-author of Nature Paper. It is only six light years from our sun and possibly twice as old.
One of the chief architects of exoplanet research, astronomer Peter van de Kamp, suggested more than 50 years ago that this star could host a planet. In the 1970s, British astronomers studied the possibility of sending an unmarried spacecraft to search for the immigration system – even though there was no evidence that a planet was available to explore.
But it was not until the first exoplanet discovery was confirmed in 1995 that the search for a world around Barnard Star began seriously.
This red dwarf is a 10th mass of our sun and too weak to be seen with the naked eye. But the low mass makes it ideal for analysis using the radial velocity technique for exoplanet detection, which utilizes the way in which a plane's gravity hits a star floor when it revolves around it.
A series of telescopes on three continents have made their views on Barnard's Star so that researchers accumulate about 800 observations for 20 years. The writers also collected data collected by amateur stars.
It took the total effort of more than 50 researchers at a few dozen institutions, but "slowly signaled our data out of all the noise," said Ignasi Ribas, the head of the Institute of Space Research in Catalonia, Spain, and the author of nature of the paper.
Barnards Star's periodic wobble suggests that it is circled by a large planet once every 233 days. Very few exoplanets have been found so far from their stars – planets with short circulation periods generate frequent signals, making them easier to detect.
Because Barnard's Star is so dark, the planet places its long orbit on the "snow line", where the sunlight is so weak that its surface is always frozen. The average surface temperature is possibly a fast -150C.
This sets the planet beyond the traditional "habitable zone", where conditions are considered mature for life. But Teske pointed out that microbes are resilient creatures – if there is water on the planet and if other necessary ingredients are present, it is possible that organisms may fool in an ocean under the ice.
But much about the planet around Barnard's Star is still uncertain. Astronomers are not sure if it is rocky like the earth or built of gas and ice, like Neptune. They know it must be at least three times as massive as the Earth, but it may be even bigger.
They are not even 100 percent some planet is there, noted Ribas.
"Difficult discoveries like this confirm confirmation of independent methods and research groups," wrote Rodrigo Diaz, an astronomer at the University of Buenos Aires who was not involved in research, commenting on nature. But if it is confirmed, the "remarkable planet" would give "a key piece in puzzles about planet formation and evolution," he wrote.