Astronomers have found an Earth-size (but not at all Earth-like) planet around an ancient star that has a nice high view of our galaxy.
Astronomers have discovered three planets orbiting a star about 10 billion years old — one of them rocky. The star, TOI 561 (meaning it was the 561st object of interest from the Transiting Exoplanet Survey Satellite), is in our galaxy’s older thick disk, which means its planets have a nice view from on high of the Milky Way’s spiral.
The star has three planets, with diameters 1.45, 2.9, and 2.3 times Earth’s. The innermost one is rocky, with three times Earth’s mass, but on a period of 0.44 days, it’s anything but Earth-like. Its dayside surface temperature is around 2500K (4,000°F). That’s at least twice as hot as Earth’s magma, and it’s surely molten. What it actually looks like is uncertain, because as lead scientist Lauren Weiss (University of Hawaii, Manoa) notes, “It exceed temperatures where geophysicists have made lava in the lab.”
Astronomers have found planets around old stars before, and even around chemically poor stars that have a paucity of heavy elements. Yet the mere fact that this planet came to be is of interest to astronomers. “We now have evidence that the universe has been forming rocky planets for the last 10 billion years, more than double the age of our own solar system, and nearly since the origin of the universe itself,” Weiss says.