One of the Oldest Stars in the Galaxy has a Planet. Rocky Planets Were Forming at Nearly the Beginning of the Universe - Universe Today

It’s one of the stars in what’s called the galactic thick disk.

The galactic thick disk is composed almost entirely of ancient stars, whose chemistry and motion are different from the thin disk.

Thick disk stars, including TOI 561, have much lower metallicity than stars in the thin disk.

So finding a rocky planet orbiting it is surprising.

“The rocky planet orbiting TOI-561 is one of the oldest rocky planets yet discovered.

The origin of the old stars in the galactic thick disk is unclear.

As a planet orbiting an ancient, 10 billion-year-old star, it’s been through a lot.

The wandering motion of stars in the disk sometimes takes them above the galactic plane.

It’s likely an indication that there’s a whole population of ancient, rocky planets orbiting ancient stars.

In fact, TOI 561b isn’t the first planet detected around a galactic thick disk star.

It’s orbiting an M dwarf star in the thick disk and was discovered in early 2020.

Not so much over the planet itself, but the thick disk.

There’s disagreement and uncertainty on the nature of the galactic thick disk itself.

In 2012 a group of astronomers published a paper in the Astrophysical Journal titled “The Milky Way Has No Distinct Thick Disk.” They argued that there is no distinct thick disk and say their data showed that “…the Milky Way has a continuous and monotonic distribution of disk thicknesses: there is no “thick disk” sensibly characterized as a distinct component.”?

Nobody’s denying the existence of the ancient stars themselves or the ancient rocky planets orbiting them.

Since stars and galaxies formed earlier than we initially believed, it seems consistent with a silicous rocky planet among gas giants at this early stage.

“They argued that there is no distinct thick disk and say their data showed that “…the Milky Way has a continuous and monotonic distribution of disk thicknesses: there is no “thick disk” sensibly characterized as a distinct component.””.

“The large-scale survey, called SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic Interstellar Medium), has revealed a wide range of structures within the Milky Way, from individual star-forming clumps to giant molecular clouds and complexes, that will allow astronomers to start pushing the boundaries of what we know about the structure of our galaxy.”.