Astronomers today announced that an ancient tiny star within 12 light-years could accommodate two temperate and rocky planets. If they are confirmed, the two newly located worlds have a mass almost identical to that of the Earth, and the two planets are in orbit, which could allow liquid water to flow out. and puddles on their surface.
Scientists estimate that the stellar host, called the Teegarden star, is at least eight billion years old, almost double the age of the sun. This means that all the planets in orbit are probably as old, so that life as we know it has had ample time to evolve. And for now, the star is remarkably silent, with little indication of tumultuous stellar tremors and eruptions that tend to spring from such objects.
These factors, as well as the relative proximity of the system, make this system an intriguing target for astronomers seeking to form new generation telescopes on other worlds and look for signs of life beyond the Earth.
"The two planets of Teegarden are potentially habitable," says Ignasi Ribas of the Institute of Space Studies of Catalonia, a member of the team reporting the planets today in the newspaper. Astronomy and astrophysics. "We will eventually see if they are habitable and maybe even inhabited."
The two worlds revolve around a star so weak that it was not seen until 2003, when NASA astronaut Bonnard Teegarden was exploiting astronomical datasets and searching for dull, close dwarf stars that had escaped detection.
The star of Teegarden is a stellar star that represents barely 9% of the mass of the sun. This is called an ultra-cool dwarf, and most of its light is infrared, just like the star TRAPPIST-1, which houses seven known rocky planets. But Teegarden's star is only one-third of the Earth's TRAPPIST-1 system, making it ideal for further characterization.
Ribas and his colleagues are currently searching for planets in orbit around 342 small stars. So they targeted the CARMENES instrument, located in the Spanish observatory of Calar Alto, on the mini-star.
CARMENES observed the Teegarden star for three years, watching the ripples and tugs produced by the planets in orbit. In the end, more than 200 measurements suggest that two small worlds are jostling each other, each weighing about 1.1 times the mass of the Earth. The team calculated that one of the planets, called Teegarden's star b, had completed its orbit in just 4.9 Earth days; The other world, C-star Teegarden, has an orbit of only 11.4 days.
Before being able to announce the probable existence of these planets, the team had to remove the intrinsic stellar phenomena, such as stars and lighting, that could pass for worlds in orbit. Sometimes it can be quite delicate for red dwarf stars, notoriously stormy and prone to massive eruptions. But Teegarden's star is almost strangely silent, making it much easier than usual to unplug the planetary signals.
"The number of measurements is so high and the star is so well driven that there is very little room for an alternative explanation," says Ribas. "So, for me, it's a clear case of detection of the planet. I'll bet my two fingers that they're here.
"These are candidates for the planet that seem very plausible," says Lauren Weiss, from the University of Hawaii. "I am impressed by the quality of the data."
However, Weiss notes, some points make her hesitate. First of all, scientists do not know the exact time it takes for the Teegarden star to rotate it, and this type of movement could pose as one of the signals of the planet.
Nevertheless, "a stellar rotation would probably reproduce only the orbit of a planet, and not two planets, so that at least one of the planets is probably real," she says.
Secondly, she says, it is possible for planets to spin faster around the star than expected, which could reduce their potential habitability.
"This technical concern is, however, minor," says Weiss. "If there are really planets around the star and the authors were wrong in their orbital periods, the planets are still planets."