Different Views of our Closest Neighbor

“The distance is nothing; it is only the first step that is difficult.” –Madame Marie du Deffand

If you’ve got some solidly dark skies, you might notice — in addition to the great field of thousands of stars — a few faint, fuzzy objects.

Visible with the naked eye (and captured with only a digital camera), this is the Andromeda Galaxy, as seen from Earth.

At a “mere” 2.4 million light years from us, it is the closest large galaxy to us, by far. As far as our best telescopes can show us, Andromeda looks like this.

Image credit: Mosaic by astropix.nl.

And you don’t want to use something like the Hubble Space Telescope! Andromeda is too close and too large to image with a narrow-angle camera like Hubble. In fact, in sheer terms of angular size, Andromeda embarrasses even the Moon.

Image credit: Adam Block and Tim Puckett.

But why limit yourself to what your eyes can see? After all, we know that there are a great many more wavelengths of light that exist, and we have telescopes specialized to see those wavelengths, highlighting different parts of the galaxy.

Let’s start in the Ultraviolet.

Thanks to the Swift Satellite, we get a view of more than 20,000 ultraviolet sources in the Andromeda Galaxy. Most of these objects are hot, young, bright stars, along with dense star clusters. The galaxy’s core, of course, is also very bright in the ultraviolet. (This image, itself, is a composite of more than 300 separate Swift images!)

But what about the cooler regions?

The Spitzer Space Telescope, looking in the far infrared, picks up stars (in blue) and great, cool dust lanes, in orange.

Those dust lanes are great, of course, and the pictures even farther to the cool end — in the radio — are far less exciting.

But what if we head all the way to the high end of the energy spectrum, and look in the X-ray?

Image credit: European Space Agency.

Shown in combination with Herschel’s infrared data (in orange), the XMM-Newton satellite grabs the X-rays, shown in blue, above. It’s only the dying stars — white dwarfs, neutron stars, black holes, and catastrophic events — that give off X-rays. But if we look at the X-rays alone…

There are hundreds of them, clustered around the center, with X-rays that head straight for us! So keep in mind, whether you’re looking out into space or at the world around you, there’s only a tiny fraction of the light that you can actually see. But as our ability to look improves, so does our understanding of our closest galactic neighbor, which in turn helps us understand our own!