BAN #297: The Southern Pinwheel Galaxy, Brain melting illusion

15 February 2021   Issue #297

[The planetary nebula M 2-9, winds from a dying star. Credit: NASA / ESA / Hubble Legacy Archive / Judy Schmidt]

Subscribers are visible and glorious from all latitudes.

Pic o’ the Letter

A cool or lovely or mind-bending astronomical image/video with a short description so you can grok it

Oh my, there is just something drop-dead gorgeous about grand design spiral galaxies… like the spectacular M 83:

[The fabulous spiral galaxy M83. Credit: CTIO/NOIRLab/DOE/NSF/AURA
Acknowledgment: M. Soraisam (University of Illinois). Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin
]

This image (click that to get much, much higher resolution versions of this) was taken by the Dark Energy Camera, a 520-megapixel instrument mounted on a 4-meter telescope in Chile. It’s an 11-hour exposure, and shows incredible detail in the galaxy. At 15 million light years away, M 83 is actually one of the closer big galaxies to us. It’s at the center of a small group of galaxies, which is possibly part of a second galaxy group anchored by the also amazing Centaurus A.

The spiral arms are just blazingly obvious, massive young hot blue stars creating a blue glow punctuated by the pink-red of warm hydrogen gas still busily churning out stars. The glow in the center is from older stars, which tend to be redder (blue stars are massive and don’t live long), and is shaped like a Tic-Tac or lozenge, what we call a bar. I imagine this is very much what the Milky Way would look like if we cold journey a few hundred thousand light years away from the Sun straight up out of the galactic disk.

I always love seeing background galaxies in images like this, too, ones very much farther away. Those ones to the upper left are likely about the same size as M 83 physically, but at 1/20th its apparent size they must be 300 million light years away or so.

M 83 is bright enough to see using binoculars, but it’s unlikely I’ll ever see it that way. It’s at the border of the constellations Hydra and Centaurus, and at my latitude of 40° north it never gets more than 20° or so above the horizon (hence its nickname, the Southern Pinwheel). Maybe if I ever visit Hawaii again or — and this would be a dream come true — if I ever travel to Chile at the right time of the year it’ll be easy enough to spot.

I haven’t seen too many spirals with my own eyes through a telescope; in general they’re faint and difficult to see any detail unless the telescope is big. But even so, the thrill of knowing those photons left that galaxy millions of years ago, traveling across intergalactic space to finally come to my very own retinae… that is something I love to feel.

It’s also a reminder that things are real, not just pretty pictures we see on the ‘net. The connection is a physical thing, and an experience I cannot get enough of.

Blog Jam

What I’ve recently written on the blog, ICYMI

[Artwork based on a real Hubble observation of NGC 6397 showing black holes swarming in its core. From Friday’s article. Credit: ESA/Hubble, N. Bartmann]

Monday 8 February, 2021: A billion galaxies lurk in a 10 trillion pixel map of the sky

Tuesday 9 February, 2021: Eclipsing binary white dwarfs, weird mergers, and peculiar supernovae

Wednesday 10 February, 2021: Here are the best places to find ice on Mars

Thursday 11 February, 2021: Have astronomers finally found a planet around Alpha Centauri? Maaaaaaaaaybe.

Friday 12 February, 2021: Black holes swarm in the core of a globular cluster

Blast from the Past

A quick link to an old post or article because it’s relevant, or came up in conversation, or just because it deserves a second look.

Every now and again I’ll notice an old blog post is getting some traffic, usually because the SYFYWire content software throws a link to it into a newer, related post. Sometimes it’s just because someone found it and linked to it, or because Google recommended it.

Whatever; it’s fun to see something from a while ago getting attention again. In this case it was even more fun for me because it was one of my better articles about an optical illusion. The illusion itself is fantastic, but I really got into explaining it and going into some detail:

Another Brain-Frying Optical Illusion: What Color Are These Spheres?

I’ll just tease you with the illusion itself, and let you click the link to find out what’s going on:

[A color contrast optical illusion makes it look like the balls are different colors. In reality they are all the same color and shading. Credit: David Novick]

It was created by David Novick, who graciously gave me permission to use it. <tl;dr> Those spheres are all the same color. Seriously. I know they look different, but our brains are astonishingly easy to fool. Enjoy.

Et alia

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