M104 is large galaxy about 30 million light-years from us, about halfway to the vast Virgo Cluster of galaxies that has well over a thousand galaxies in it. M104 is in a smaller group of galaxies that’s like a suburb to the bigger cluster.

Because it’s large and close by, it’s relatively bright, making it a favorite target for amateur astronomers, who take amazing shots of it. But when you point a big space telescope at it with incredible resolution, it becomes a thing of utter beauty.

You can also really see why it’s nicknamed the Sombrero Galaxy:

[Click here to agrandarenate for a giant 14,000 x 8,500 version!]

This image uses new processing techniques on older images to create a higher resolution version than what was released over 20 years ago. It was done to celebrate Hubble’s 35^th year in orbit.

The Sombrero is an oddball. It looks lie a disk galaxy with very weak arms; such galaxies are classified as S0 galaxies, which typically lack dust. Yet there’s that obvious ring of dark dust all along the edge! What gives? Likely the galaxy collided and merged with a smaller dust-rich galaxy sometime in the recent past, which got torn apart by the gravity of the bigger galaxy and is still in the process of coalescing.

I noticed an interesting thing, though. To my eye the inner disk looks extremely flat, which it actually is. But the dust along the edge looks puffed up, more like a cylinder surrounding the flat disk. I can think of ways that could physically happen, but it is real?

I don’t think so; I think it’s an illusion. The dust is flat, but extended, like a ring around the disk, and pretty much just as flat. When you look down the center of the dust perspective foreshortens it, but along the edge to the right and left you see its true extent. The illusion (if it is an illusion) is reinforced by the dust blocking some of the disk, especially on the left, making the disk itself look like it’s puffing up.

I may be wrong, and it actually might be vertically extended above and below the disk. But I’d need to see good evidence of it.

Anyway, Hubble launch on April 24^th, 1990, so expect to see even more spectacular images coming in the next week. This is always a fun time of year.

[You can also check out this amazing shot of the Sombrero with JWST that highlights that dust! Not how flat the ring looks in the infrared, supporting my claim.]

Well, this is fun: I get to post a follow-up to something I wrote a while back with good news.

In BAN Issue 593 (July 20, 2023) I wrote an article about a two-faced white dwarf, which appeared to have one hemisphere covered in hydrogen and the other in helium. This was unexpected, to say the least!

White dwarfs are the ultra-compressed cores of stars much like the Sun after they die. The process is complicated (and I go over it in Crash Course Astronomy: Low Mass Stars), but when they run out of fuel in their cores to fuse the outer layers swell up and the star becomes a red giant. Those outer layers eventually blow off, leaving behind the core of the star exposed to space. That core is now super-dense, in a state of quantum weirdness called degeneracy (which I also cover in the Crash Course episode, as well as in the chapter on the Sun in my book Death from the Skies!). It’s hot and small, so we call it a white dwarf.

Due to their intense gravity, heavy elements tend to sink below the surface very rapidly, leaving only hydrogen and/or helium behind. This gets complicated fast, but whether the top layer is hydrogen or helium depends on a lot of different factors, including temperature. White dwarfs have intensely hot interiors but cooler (though still hot) surfaces, which means they can have convection, where hot material rises and cooler stuff sinks (just like warm/cool air in our atmosphere). They tend to have a lot more helium than hydrogen in their interiors, so if there’s a surface layer of hydrogen that’s thin, convecting helium can rise up and break through. If the hydrogen layer is thicker it acts like a lid and the helium can’t make it to the surface. So, in general, we expect to see either all hydrogen, all helium, or possibly a mixture everywhere of the two.

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