HEIC: NGC 4452: An Extraordinarily Slender Galaxy

[bystander]

NGC 4452: An Extraordinarily Slender Galaxy
Hubble European Picture of the Week | potw1029a | 08 Nov 2010

Click to view full size image

The NASA/ESA Hubble Space Telescope has imaged a striking galaxy called NGC 4452, which appears to lie exactly edge-on as seen from Earth. The result is an extraordinary picture of billions of stars observed from an unusual angle. The bright nucleus can be seen at the centre, along with the very thin disc that looks like a straight line from our unusual viewing position. To complete the picture, a hazy halo of stars on the periphery of the galaxy makes it seem to glow.

NGC 4452 was first seen by William Herschel in 1784 with his 47 cm telescope in England. He described the object as a bright nebula, small and very much elongated. The new Hubble image shows just how elongated this unusual object really is.

Galaxies are like star cities, and typically contain many billions of stars. The American astronomer Edwin Hubble, after whom the Hubble Space Telescope is named, was the first person to prove that there are other galaxies beyond our own by measuring their distances. This work, done in the 1920s, forever changed our view of the Universe.

Galaxies also belong to collections that are called galaxy clusters. NGC 4452 is part of the Virgo Cluster, so-called because many of its members appear in the constellation of Virgo (the Maiden). This enormous grouping is approximately 60 million light-years distant and contains around 2000 galaxies.

It is thought that the Local Group of galaxies, to which our own Milky Way belongs, is on the fringes of the Virgo Cluster, and at some point in the far future the Local Group may be pulled slowly into the Virgo Cluster by the force of gravity. Large numbers of much more remote, faint galaxies, far beyond NGC 4452 and the Virgo Cluster, appear in the background of this image.

This picture of NGC 4452 was created from images taken using the Wide Field Channel on Hubble’s Advanced Camera for Surveys. This picture was made from images through blue (F475W, coloured blue) and near-infrared (F850LP, coloured red) filters. The exposures times were 750 s and 1210 s respectively. The field of view extends over 2.6 arcminutes.

Credit: NASA/ESA/Hubble

[owlice]

Oh, that's very cool!! Thanks for posting it!

[bystander]

Galaxy on Edge
Bad Astronomy | 08 Nov 2010

Spiral galaxies are among the most magnificent objects in space. Grand and sprawling, they are icons of the night sky.

Like a snapshot of coins tossed in the air, we see them at all angles, from face-on disks to nearly edge-on lines. And sometimes we catch them so precisely to the side that what we see is hard to believe is real. But then we get pictures like this one from Hubble of the galaxy NGC 4452: (see above)

Holy perpendicularity!

There are lots of edge-on galaxies in the sky, like NGC 253 and NGC 4710, but this one is extraordinary. The alignment is perfect, and the disk is incredibly thin. Our Milky Way is 100,000 light years across and 2500 or so light years thick (a ratio of 40:1), but NGC 4452 looks even thinner than that; measuring off the picture I get a width-to-thickness ratio of 100:1.

Amazing.

[url=http://www.eso.org/public/images/eso0525a/][b]Spiral Galaxy NGC 4565[/b][/url] [i](Credit: ESO)[/i]

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Other things are obvious, too, and honestly a bit weird. For one thing, the central bulge of the galaxy is very small; in most edge-on galaxies it pokes above and below the disk like in NGC 4565, shown here. In that picture you can also see lots of dark dust; that’s actually complex organic molecules that are very efficient at absorbing visible light. They’re created when stars are born and when they die, and dust clouds tend to huddle close to the center of the disk.

But NGC 4452 appears denuded of dust! I’ve never seen a galaxy quite so clean. I think it would actually pass the white glove test. As it happens, this galaxy is part of a nearby cluster called the Virgo Cluster, a collection of hundreds of galaxies about 60 million light years away. In between the galaxies is a thin fog of gas, and as the galaxies orbit each other they plow through this gas. The high speeds at which they travel can actually strip them of their own gas and dust, like when you open your car window while driving to get rid of, um, say, an obnoxious smell. Perhaps this is what happened to NGC 4452.

The disk is surrounded by a fuzzy glow, which would be the collected light from billions of stars above and below the disk. Note that if you look to the extreme edges of the disk, the fuzzy glow appears to subtly bend down on the left and up on the right. The galaxy is warped! This is common in disk galaxies (the Milky Way and nearby Andromeda galaxies are warped, and you can also see it in NGC 5866). It’s usually caused by a gravitational torque, an off-center tug, from a nearby galaxy. Since NGC 4522 is in a cluster, it’s not too surprising there might be some galaxy that could do this.

And finally, one more thing. Look at all the distant background galaxies in the picture! There are dozens of them scattered about, most much, much farther away. Mind you, this picture of NGC 4452 is a short exposure; just a combination of 12.5 minutes using a blue filter and 20 using an infrared one. This means the sky is filled with galaxies!

And each one is an island Universe, made of billions of stars along with massive gas and dust clouds, and each as spectacular and amazing as this one seen up close.