A planet for Fomalhaut? And three ancient stars from another galaxy orbit our own

Four stars star in today’s issue: One maybe with planets, and three that formed at the same time our galaxy did

May 20, 2024 Issue #723

Astro Tidbit

A brief synopsis of some interesting astronomy/science news

Fomalhaut is a pretty interesting star. It’s in the constellation of Pisces Austrinus at a magnitude of about 1 (making it the 18th brightest in the night sky), and can be seen from northern locations. It’s very young, probably only a couple of hundred million years old, and about twice the mass of the Sun.


Its youth plus it’s proximity (about 25 light-years form Earth) make it a prime target for study. It’s been known to have a dusty disk (called a debris disk) around it for a long time, and high-resolution images show the disk to be broken up into rings. That’s a decent sign that at least one planet is forming there; the gravity from the planet(s) can sculpt gaps into the disk and make rings. So it’s been a very interesting target in recent years indeed.

Concentric fuzzy orange rings circle the blacked-out spot where Fomalhaut sits, and are labeled along with gaps between the rings, and the Great Dust Cloud which may or may not actually be a dust cloud.

An annotated image of the Fomalhaut dust ring system. Credit: NASA, ESA, CSA, A. Pagan (STScI), A. Gáspár (University of Arizona)

But… is it? A cloud, I mean. Analysis of new JWST images, together with images from Keck and ALMA, indicate it’s actually a background galaxy coincidentally superposed on the ring [link to journal paper]. That’s disappointing; structures in rings are pretty cool and could be clues to more planets forming. In fact, many objects seen apparently in the disk are actually background objects. One, however, doesn’t seem to have any counterpart in Keck images, so it may not be a background object, and is intriguingly very close to the inner ring seen in earlier JWST images. Could this be Fomalhaut’s first detected planet? Maybe! More observations are planned with JWST; if the object has moved in between images and the motion is consistent with that of a planet, well, that’ll be interesting, won’t it?

Another thing found in earlier images was a blob that was at first thought to be a planet, but faded over time, making astronomers wonder if it were a dust cloud from two planetesimals colliding (these are planet building blocks in the 1-km size range). The new images don’t show it at all, so it could be a dispersed cloud. All they can say right now is that if it’s an actual planet it has to be less than the mass of Jupiter, or else it would be bright enough to be seen more clearly.

I love all this; we knew almost nothing about how stars and planets form when I was first starting out as an astronomer, and now we have images good enough to simply see what’s going on in nearby systems. Maybe the news we get isn’t what we want — a planet forming in a nearby star system! — but it’s still amazing that we can figure this out at all, and there’re still enough cool things going on at Fomalhaut to make it worthy of far more study.

Astro Tidbit

Yes, a second one

This is a fun news story, with a twist that made me smile.

A team of astronomers — more on them in a sec — have found three of the oldest stars in the galaxy. They orbit out in the halo of the Milky Way, the flattened spherical cloud of stars that surrounds the disk of the galaxy. They very likely were born in a small galaxy long ago, which then collided with and was subsumed by our much bigger one. 

The team was led by Anna Frebel, an astronomer at MIT. She looks for ancient stars in the galaxy as a way to determine conditions when the Milky Way was young, and has data on quite a few. As part of a class she teaches (Observational Stellar Archaeology) some of her students pored through the data looking for stars that were particularly old. When the Universe was young, there were very few heavy elements like iron, so by searching for stars with very low abundances of such elements you can find ancient examples.

The three stars found are very deficient in these elements — one has 1/10,000th the relative abundance of iron as the Sun — and so they’re incredibly old, dating back 12 – 13 billion years, meaning they formed when the cosmos was young indeed. Super cool. You can read more about this in the MIT press release, and here’s a link to their journal paper.

But there’s more. The team led by Frebel consisted of three women undergraduates, which is terrific. I’m all for supporting more women in astronomy, and making sure historically marginalized groups get their fair shot at being scientists.

That made me happy, but what really broadened my grin was the caption to the press image showing three of the women together. 

Three women smiling, holding up a binder with data from the observations in them.

Anna Frebel (right) and two of her undergrad team members, Ananda Santos (left) and Casey Fienberg. Credit: Frebel et al.

Frebel had graphs of the stellar spectra (plots of the brightness of a star versus color, which can reveal elemental abundances) she had observed printed out and stored in a three ring binders. The caption to the photo given is, “Researchers hold a binder full of data about stars that they have collected over the years, including star brightness over time.” [Emphasis mine]

“A binder full of data”, with a photo of three women holding it. Hmmmmm. Sounds like a direct (and well-deserved) dig against the sexism of Mitt Romney. I laughed when I saw the caption; I’m all for mocking chuckleheads when they perform their chuckleheadedry.

It takes on a deeper meaning, too, when you learn that stellar classification like this was at first done mostly by women, such as Annie Jump Cannon (and, in my own undergraduate era, Nancy Houk)… and it was the brilliant astronomer Cecilia Payne-Gaposchkin who first understood the critical relationship between a star’s temperature and the spectrum we saw. 

Anyone who thinks women should be relegated to the kitchen instead of wherever they damn well want to be needs to be kicked to the curb.

Et alia

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