BAN #117: U Ant and Goose

May 27, 2019 Issue #117

[Saturn image credit: NASA / JPL / Space Science Institute / Gordan Ugarkovic]

Subscribers take my breath away.

Pic o’ the Letter

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

If you’re like me, you procrastinate. That is to say, if you’re a human, you procrastinate.

So if you’ve been blowing off getting a 2019 calendar, do I have what you need… well, the European Southern Observatory’s ALMA Observatory has what you need. They sent me their 2019 calendar, and it’s gorgeous.

It’s in Spanish, but for those of us who don’t speak it it’s still pretty easy to figure out which month is which. The calendar features 12 images of the observatory itself or objects it’s observed. The one shown is a weird star called U Antlia. It’s a carbon star, a star a bit more massive than the Sun which has turned into a red giant and has generated a lot of carbon which now pollutes its atmosphere. Carbon stars are extremely red to the eye, and tend to blow off shells of material that surround them.

This image of U Ant is interesting. ALMA observes in the millimeter wavelength region of the EM spectrum, and can very sensitively measure this flavor of light, including how much it is shifted due to velocity toward or away from Earth. In that image of U Ant, it shows the velocity of the gas in the expanding shell relative to Earth… but only gas on the hemisphere facing Earth. So all this gas is moving toward us as the shell expands, and color represents the velocity.

If you look right down the center, toward the star, the gas in the shell at that point is expanding directly toward us, and so has the biggest blue (Doppler) shift. As you move toward the edges the gas is moving more toward the sides, and the blue shift drops to zero at the edge (that gas is colored red, which confused me for a moment; in velocity plots red usually means moving away, and I couldn’t figure out why gas at the edge (with zero relative velocity toward or away from Earth) would be colored red. It’s just an artistic choice they made). I know, it’s a little confusing, but it’s pretty!

The really good news here is you can download the calendar as a PDF for yourself for free! So thanks to the good folks at ALMA for sending it to me, and I hope y’all grab a copy for yourself.

And oh, hey, follow them on Twitter! They always have interesting stuff going on that they’re looking at.


Because my home state is pretty

Eject! Eject! Eject!

[Credit: Phil Plait]

Blog Jam

What I’ve recently written on the blog, ICYMI

[The weird star R Aquarii is a symbiotic binary where one star is blowing off shells of gas and the other one sometimes explodes. The really weird part is how this ties in with The Monkees. See Friday’s post. Credit: X-ray: NASA/CXC/SAO/R. Montez et al.; Optical: Adam Block/Mt. Lemmon SkyCenter/U. Arizona]

Monday May 20, 2019: What astronomers mean by “rubble pile asteroids”

Tuesday May 21, 2019: Eerie glowing clouds light up the Martian twilight

Wednesday May 22, 2019: When the Earth Hulks out: Our planet sparkles in gamma-rays

Thursday May 23, 2019: Two billion years ago, our galaxy had a burst of star birth

Friday May 24, 2019: The recurrent exploding nova R Aquarii: Unlucky Stars

Et alia

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