Saturday, March 30, 2013

Hubble Observes The Hidden Depths Of Messier 77

The NASA/ESA Hubble Space Telescope has captured this vivid image of spiral galaxy Messier 77, one of the most famous and well-studied galaxies in the sky. The patches of red across this image highlight pockets of star formation along the pinwheeling arms, with dark dust lanes stretching across the galaxy’s energetic centre.




Messier 77 is a galaxy in the constellation of Cetus, some 45 million light-years away from us. Also known as NGC 1068, it is one of the most famous and well-studied galaxies. It is a real star among galaxies, with more papers written about it than many other galaxies put together!

Despite its current fame and striking swirling appearance, the galaxy has been a victim of mistaken identity a couple of times; when it was initially discovered in 1780, the distinction between gas clouds and galaxies was not known, causing finder Pierre M├ęchain to miss its true nature and label it as a nebula. It was misclassified again when it was subsequently listed in the Messier Catalogue as a star cluster.

This video pans across the sky near to spiral galaxy Messier 77 in the constellation of Cetus, ending on a view of the famous object itself. M 77 is a highly-studied galaxy, with an active black hole at its centre and regions of bright star formation dotted along its loosely-wound arms.

Credit: NASA, ESA, Digitized Sky Survey 2. Acknowledgement: A. van der Hoeven

Now, however, it is firmly categorised as a barred spiral galaxy, with loosely wound arms and a relatively small central bulge. It is the closest and brightest example of a particular class of galaxies known as Seyfert galaxies — galaxies that are full of hot, highly ionised gas that glows brightly, emitting intense radiation.

Strong radiation like this is known to come from the heart of Messier 77 — caused by a very active black hole that is around 15 million times the mass of our Sun. Material is dragged towards this black hole and circles around it, heating up and glowing strongly. This region of a galaxy alone, although comparatively small, can be tens of thousands of times brighter than a typical galaxy.

This video zooms in on spiral galaxy Messier 77. The sequence begins with a view of the night sky near the constellation of Cetus. It then zooms through observations from the Digitized Sky Survey 2, and ends with a view of the galaxy obtained by Hubble.
Credit:  NASA, ESA, Digitized Sky Survey 2. Acknowledgement: A. van der Hoeven

Although no competition for the intense centre, Messier 77’s spiral arms are also very bright regions. Dotted along each arm are knotty red clumps — a signal that new stars are forming. These baby stars shine strongly, ionising nearby gas which then glows a deep red colour as seen in the image above. The dust lanes stretching across this image appear as a rusty, brown-red colour due to a phenomenon known as reddening; the dust absorbs more blue light than red light, enhancing its apparent redness.

This image from the Digitized Sky Survey shows spiral galaxy Messier 77 and its surroundings.
Wide-field image of Messier 77 (ground-based image)
Credit: NASA, ESA, Digitized Sky Survey 2

A version of this image won second place in the Hubble’s Hidden Treasures Image Processing Competition, entered by contestant Andre van der Hoeven [1].


Contacts and sources:
Nicky Guttridge
Hubble/ESA

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