10:19:06	 From Richard Moore : DAV means what?
10:19:20	 From JJ Hermes (Boston University) : DAV = pulsating hydrogen-atmosphere white dwarf
10:22:32	 From Richard Moore : what does the D in DAV mean?
10:25:25	 From JJ Hermes (Boston University) : All white dwarf spectral types start with D. If you’re a masochist for naming conventions there’s a nice history here: http://adsabs.harvard.edu/full/1994ASPC...60...64L
10:27:09	 From Mark Zagaeski : lol
10:27:57	 From Richard Moore : I'm not a masochist, I just want to know how you start with a D
10:28:02	 From Matteo Cantiello : D = Dwarf
10:28:43	 From Pradip Misra : Interesting.
10:28:52	 From Matteo Cantiello : (interestingly they didn’t start with a D… but then realized that the spectra corresponded to a small star. So D it was)
10:29:31	 From Richard Moore : wow, that wasn't hard now was it. D stands for Dwarf.
10:30:38	 From Lisa CaseyOBrien : How do you distinguish between changes that would be due to pulsations versus something due to the white dwarf rotating (could a fixed temp spot seem to pulsate due to rotation)?
10:31:02	 From Matteo Cantiello : So DAV: D( white dwarf ) A (with only Hydrogen absorption lines in spectrum) V (Variable star)
10:31:19	 From Michael Montgomery (UT-Austin) : If the star is multi-periodic, i.e., shows several modes, then it is more likely to be a pulsator...
10:31:33	 From JJ Hermes (Boston University) : Sorry, Richard, no offense intended — I was being cheeky. The history of these names was set in a time when astronomers didn’t have a great physical picture of the objects.
10:32:01	 From woody maxwell : cheeky is good
10:33:38	 From Matteo Cantiello : Yes. Naming conventions in astronomy are sometimes not obvious, and often tell the history of how we went from just classifying objects to understanding them. So it’s interesting to read about it :)
10:35:01	 From Michael Montgomery (UT-Austin) : The center of the star is on the left and the surface is on the right..
10:37:28	 From Marc Afifi Pacific Grove HS : Is the core actually diamond? Or is it crystallized carbon nuclei (+6 ions)?
10:38:54	 From Matteo Cantiello : Note the frequency of these pulsations: ~1000-2000 microHz. So these stars pulsate with periods of hundreds to thousand of seconds (minutes to hours). Compare to the guitar string at 400 Hz
10:39:20	 From Mark Zagaeski : @Marc good question - How much like “diamond” is the core?
10:41:53	 From Michael Montgomery (UT-Austin) : I got the same question on a short BBC radio interview…it’s not *exactly* the same, since diamonds are held together by electronic bonds, i.e., sharing electrons. But in the WD there aren’t any bound electrons and it’s just the nuclei getting as far from each other as possible. But, it’s the “stellar interior equivalent” of a diamond, because it *is* crystallized carbon! :-)
10:42:32	 From Matteo Cantiello : it’s a very hot diamond
10:42:42	 From Mark Zagaeski : Ahh, Thanks that makes sense
10:42:46	 From Marc Afifi Pacific Grove HS : Thanks.
10:43:05	 From Marc Afifi Pacific Grove HS : So it’s like a metal conductor?
10:43:47	 From Michael Montgomery (UT-Austin) : Yep, the interiors are highly conductive, both electrically *and* for heat.
10:44:12	 From Marc Afifi Pacific Grove HS : Neat
10:44:53	 From Richard Moore : is that optical clock adjusted for the doppler effect? If its moving away the frequency would naturally get longer
10:47:37	 From Mark Zagaeski : Blown apart because it is so hot?
10:48:36	 From Matteo Cantiello : Hot and high pressure. It’s kept together by gravity, not molecular bonds
10:49:37	 From Mark Zagaeski : right - so it contains so much KE that it just flies apart
10:51:31	 From Michael Montgomery (UT-Austin) : Yes, but it’s also the nuclei repelling each other. In the star, there is gravity to keep everything compressed, but if you remove the material it would just push itself apart and expand…
10:51:55	 From Eric Bullock : Diamond is 2 intersecting face-centered cubic lattices.
10:52:18	 From Mark Zagaeski : Ahhh yes - hard to think of the Pauli exclusion principal applied to nuclei
10:53:10	 From JJ Hermes (Boston University) : There are a few binaries where you can see lensing from a white dwarf, here’s a great animation of the first: https://phys.org/news/2014-04-astronomers-self-lensing-binary-star.html
10:53:53	 From JJ Hermes (Boston University) : The white dwarf has so much gravity and is so compact that instead of a transit when it passes in front of the other star, it causes a brightening!
10:54:08	 From Sean Kelly 🌟 : @JJ That's awesome!
10:55:24	 From Sean Kelly 🌟 : @Thank you Barbara!
10:55:59	 From David Wittenberg : thank you Barbara.
10:56:03	 From Gabriel Garcia : thank you Barbara