BAN #205: Free funny books!, The edge of flocculence
30 March 2020 Issue #205
|Phil Plait||Mar 30, 2020||4||1|
[Spiral Galaxy M81 image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona]
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Where I’ll be doing things you can watch and listen to or read about
If you’re looking for some clever and fun books to read while in self-isolation, but don’t want to spend any more money, then you’re in luck: My friend Zach Weinersmith has made a lot of his books free to download as PDFs!
He’s written some very smart and very funny short books, like The Holy Bible: Abridged Beyond the Point of Usefulness, Science: Abridged Beyond the Point of Usefulness, Shakespeare’s Sonnets: Abridged Beyond the Point of Usefulness, and my favorite of his, Science: Ruining Everything Since 1543 (note: In a special section in at the end of that last one he asked for contributions by various scientists, and I am honored to be a part of that).
He also included a book he and I wrote together, illustrated by Jess Fink, called 2^7th Nerd Disses: A Significant Quantity of Disrespect. It’s essentially “yo mama” jokes but without the fat shaming. It was extremely fun to write, especially when we realized we needed an appendix that explained the jokes, which can be, um, a bit nerdishly intellectual (basically, he kept sending me jokes I didn’t understand so I had to keep looing them up, and realized readers might want them explained, too — so we wrote the explanations to (mostly and IMO) be funny, too).
So grab these for free and enjoy!
Pic o’ the Letter
A cool or lovely or mind-bending astronomical image/video with a short description so you can grok it
Every now and again, I see an image of an edge-on spiral galaxy and I think, what would that look like if we could see it more face-on?
Sadly, intergalactic travel is somewhat time consuming (even at the speed of light it would take millennia to travel up high above our own galaxy, and the nearest big galaxies to us are over 2 million light years away). Sometimes, though, nature provides.
For example, in my email I got a note from image processing master Robert Gendler, whose work I’ve written about many times in the past both on the blog and here in the newsletter. This time it was about NGC 253, a bright and well known galaxy that is very nearly edge-on. He used images of it from the massive Subaru telescope, Hubble, the VLT, and the Danish 1.5-meter, to create a spectacular image of this object:
Wow! Mind you, this is a small version; the big one is jaw-dropping.
NGC 253 is a spiral galaxy we see at a very shallow angle, so it looks nearly flat. The spiral structure is a little difficult to follow, but that’s not just because it’s so tilted. It’s also a flocculent galaxy, literally from the word meaning “patchy like cotton or tufts of wool”. Instead of obvious connected spiral arms, they’re broken up into clumps or tufts. The reason for this isn’t perfectly understood, though in a post about a similar galaxy, M63, I wrote this:
The patchwork nature may be due to a process called (and I love this)stochastic self-propagating star formation. If a gas cloud is forming stars, then the big, hot stars born there can trigger star formation in nearby gas clouds, and then the stars born there trigger stars in other nearby clouds, and so on. As the galaxy rotates those clouds are sheared away from each other, creating the blotchy spiral pattern. It's not certain this is the process, but it does explain a lot of what we see.
Still, as I looked at the shot of NGC 253, I wondered (remember this from the start of this article?) what it would look like if we could see it better.
And then not a day later this image of the spiral NGC 4237 popped up when I was looking into something else:
[NGC 4237. Credit: ESA/Hubble & NASA, P. Erwin et al.]
Wow! This is from Hubble, and is not “natural” color; what you see as blue is actually from a blue-green filter, orange is from near-infrared, and red is from true infrared (a wavelength of 1.6 microns, about twice the reddest wavelength our eyes can see). Still, clumpy, flocculent nature of the galaxy is obvious.
It does look a lot like what I suspect NGC 253 would look like from a higher angle. Gendler’s image emphasizes gas clouds (the red splotches all through the arms of NGC 253) while the Hubble image doesn’t, but still, the resemblance is strong.
We can’t leave our galaxy to see others at different perspectives, but the good news is that with thousands of galaxies close enough to us to see in detail, we’re bound to see ones with similar structure but at different angles to us. That helps us understand their features, and compare them with each other to see what other features may be similar, and which ones may be very different. Why do some spiral galaxies have tightly wound arms, and others more loosely outflung? Why do some have large central bulges and others barely have one at all? Why do some produce prodigious amounts of stars and others seem moribund?
The more galaxies we observe, and the more ways we observe them, allow us to catalog them, categorize them, learn why they behave the way they do. And since we live in a galaxy, one we still don’t fully understand, this seems like a pretty good thing to do.
What I’ve recently written on the blog, ICYMI
[Did you finish watching all of Star Trek: Picard? It turns out that eight-star system can actually exist! From Thursday article. Credit: CBS]
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