JPL: Cool, New Views of Andromeda Galaxy

[bystander]

Andromeda's Colorful Rings
Credit: ESA/NASA/JPL-Caltech/NHSC

Cool Andromeda
Credit: ESA/Herschel/PACS & SPIRE Consortium, O. Krause, NHSC, H. Linz

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Cool, New Views of Andromeda Galaxy
NASA | JPL-Caltech | 2013 Jan 28

Two new eye-catching views from the Herschel space observatory are fit for a princess. They show the elegant spiral galaxy Andromeda, named after the mythical Greek princess known for her beauty.

The Andromeda galaxy, also known as Messier 31, lies 2 million light-years away, and is the closest large galaxy to our own Milky Way. It is estimated to have up to one trillion stars, whereas the Milky Way contains hundreds of billions. Recent evidence suggests Andromeda's overall mass may in fact be less than the mass of the Milky Way, when dark matter is included.

Herschel, a European Space Agency mission with important NASA contributions, sees the longer-wavelength infrared light from the galaxy, revealing its rings of cool dust. Some of this dust is the very coldest in the galaxy -- only a few tens of degrees above absolute zero.

In both views, warmer dust is highlighted in the central regions by different colors. New stars are being born in this central, crowded hub, and throughout the galaxy's rings in dusty knots. Spokes of dust can also be seen between the rings.

One view, seen at Cool Andromeda, is a mosaic of data from Herschel's Photodetecting Array Camera and Spectrometer (PACS) and spectral and photometric imaging receiver (SPIRE).

The second view, seen at Andromeda's Colorful Rings, shows data from only the SPIRE instrument, which captures the longest of wavelengths detectable by Herschel.

See the Andromeda Galaxy in a Cool New Light
Discovery News | Ian O'Neill | 2013 Jan 29

Lighting Up Andromeda’s Coldest Rings
Universe Today | Jason Major | 2013 Jan 30

The Cold, Dusty Arms of Andromeda
Slate Blogs | Bad Astronomy | 2013 Jan 30

[Ann]

http://www.jpl.nasa.gov/news/news.php?release=2013-035 wrote:
In both views, warmer dust is highlighted in the central regions by different colors. New stars are being born in this central, crowded hub, and throughout the galaxy's rings in dusty knots.

I feel seriously talked down to here. The images, which look very good, are necessarily false color images, since the pictures trace invisible infrared light. Shouldn't it be a reasonable service to the public to inform them what the different false colors mean, then? The images highlight the dust in Andromeda, and personally I might guess that the coolest dust of Andromeda looks reddest here, while the warmest dust looks bluest.

The bluest and presumably warmest dust is found in Andromeda's most central parts. Reading the caption from NASA, one might guess that most of the star formation in Andromeda is taking place near the center of the galaxy. That, however, is probably not the case. In traditional visible-light images, Andromeda's central hub is yellow, with few signs of star formation. The outer parts of our great neighbour galaxy are predominantly blue in optical light and contain pink emission nebulae, so new stars are obviously being born here.

I suspect that fewer stars are being born in the dust lanes that look blue in the new Herschel images, because these dust lanes are probably too warm for vigorous star formation. Cool dust clouds are much better than warm dust when it comes to giving birth to new stars.

Not that you would understand that from reading NASA's caption here.

Ann