Green Valley: The Town Too Good To Die

Galaxies of different colors

I swear we are consistently trying to keep our live hangouts to about 15 minutes. We have so far failed at keeping to time, but hopefully also succeeded in the sense that we only run over because there’s so much to discuss.

We had a number of good questions from Twitter, Facebook and the blog about various types of galaxies — from red spirals to green peas and blue ellipticals — and I rather arbitrarily decided this was an indication that our hangout should have a color theme. That is, what exactly does “color” mean in the context of astronomy? What is going on physically when a galaxy is one color versus another, or has multiple colors? Is color information always telling us the same thing? We tried to address all those questions, as well as show some examples of different galaxies in the above queried categories. As a bonus, we learned how galaxy colors are related to the town my grandparents retired to. (This post’s title is a quote from the Green Valley Chamber of Commerce’s official website.) That was as much a surprise to me as it was to the viewers!

We also talked about what’s currently going on in Galaxy Zoo behind the scenes. Earlier today, Kyle sent around a really nice draft of the Galaxy Zoo 2 data paper for the team to read and comment on (you’ll have to watch the video to get a sneak peek at some of the figures).

And it’s that time again: Hubble Space Telescope proposals are due in about a week. We talked about the proposal process from concept to submission to review, discussing both specifics of certain telescopes and the general practices that (we hope) help lead to a successful proposal. Here’s a hint: it may not be what you think!

We covered all this and some other questions, too. No wonder we ran a little over…

And here’s the podcast version:

Download MP3 file

GZ4 merger or overlap set

Is it a triple merger? A double overlap? A hybrid?

Spiral Colors

A blue(ish) and red spiral.

Elliptical colors

A red and blue elliptical.

Green pea

A tiny green pea galaxy, and zoomed-in at right.

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3 responses to “Green Valley: The Town Too Good To Die”

  1. Bill Keel says :

    For more on how Hubble proposals are evaluated – I got permission from the Powers that Be to blog the experience of being on a Hubble allocation panel some years ago (slightly sanitized so no proposals were identifiable):
    (formatting slightly weird on replies due to archiving steps).

  2. Jean Tate says :

    Re passive red spirals (and dust): hot off the arXiv pre-press: “GAMA/H-ATLAS: Linking The Properties of Sub-mm Detected and Undetected Early-Type Galaxies: I. z$\le$0.06 Sample” ( – a star cast of authors!) It would seem that quite many ETGs (ellipticals, lenticulars) do have on-going star-formation (and not just blue ellipticals). Many also have – surprisingly? – large quantities of dust; maybe dust lasts longer than had previously been assumed?

    Although they excluded ETGs with AGNs, the authors seem to have made no attempt to judge whether any of the remaining ETGs have now-quiet-but-recently-active AGNs (the GZ-based Voorwerp/voorwerje work doesn’t seem to have sunk in, yet).

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  1. Next Galaxy Zoo Hangout: 22 Feb, 15:30 GMT | Galaxy Zoo - February 24, 2013

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