A tiny, old star just 12 light-years away could host two temperate, rocky planets, astronomers announced today. If they are confirmed, both of the newly spotted worlds are nearly identical to Earth in mass, and both planets are in orbit that would allow liquid water to trickle and puddle on their surfaces.
Scientists estimate that the star stellar host as Teegarden's star, is at least eight billion years old, or nearly twice the sun's age. That means any planet orbiting it is presumably as ancient, so life as we know it has had more than enough time to evolve. And for now, the star is remarkably quiet, with few indications of the tumultuous stellar quakes and flares that tend to erupt from such objects.
These two factors, plus the system's relative proximity, make the system an intriguing target for astronomers seeking to train next-generation telescopes on other worlds and scan for signs of life beyond Earth
"Both Teegarden's planets are potentially habitable, "Says Ignasi Ribas of the Institute of Space Studies of Catalonia, and a member of the team reporting the planets today in the journal Astronomy & Astrophysics . "We will eventually see if they are actually habitable and perhaps even inhabited."
The two worlds orbit and star so faint that it was not even spotted until 2003, when NASA astrophysicist Bonnard Teegarden
Teegarden's star is a stellar runt that's barely 9 percent of the sun's mass. It is known as an ultra-cool M dwarf, and it emits much of its light in the infrared – just like the star TRAPPIST-1, which hosts seven well-known rocky planets. But Teegarden's star is just a third as far away as the TRAPPIST-1 system, making it ideal for further characterization.
Ribas and his colleagues are currently searching for planets orbiting, which is about 12 light-years away from the red dwarf system. 342 small stars, so they targeted the CARMENES instrument, located at the Spanish Calar Alto Observatory, at the mini-star
CARMENES observed Teegarden's star over three years watching the wiggles and tugs produced by any orbiting planets. In the end, more than 200 measurements suggested that two small worlds jostling the star, each weighing in at approximately 1.1 times Earth's mass. The team calculates that one of the planets, called Teegarden's star b, completed an orbit in a mere 4.9 Earth-days; the other world, Teegarden's star c, has an orbit of just 11.4 days
Before they could report that those planets probably existed, the team had to rule out intrinsic stellar phenomena like star spots and flares, that can masquerade as orbit worlds. Sometimes, this can be quite tricky for red dwarf stars, which are notoriously tempestuous and prone to erupting in massive flares. But the Teegarden's star is almost eerily quiet, making it much easier than usual to tease out the planet's signals
"The number of measurements is so high and the star is so well-behaved that there is very little room for an alternative explanation, "Ribas says. "So, this is me, and a clear case of planet detection. I would bet both my little fingers that they are there. "
" These are very plausible-looking planet candidates, "agrees Lauren Weiss of the University of Hawaii. "I am impressed by the quality of the data."
However, Weiss notes, and few points cause her to hesitate. First, scientists do not know the exact time it takes for Teegarden's star to rotate on its axis, and that type of motion could be masquerading as one of the planet's signals.
Still, "stellar rotation would probably only mimic the orbit of a planet, not two planets, so that at least one of the planets is probably real," she says. "
" This technical concern is minor though, "Weiss says. "If there are really planets around the star, and the authors have their orbital periods wrong, the planets are still planets."