A slightly warped edge-on spiral galaxy

NGC 4634 as seen by the Hubble Space Telescope – click for 1280×1093 version, or for full-on warpage, get the 23796×2388 version

Hot on the heels of another beautiful Hubble image of an edge-on spiral galaxy is a Hubble image of NGC 4634. What makes this image so interesting is the slight warp in the disk. If you look closely, you’ll see that the  disk is tilted upright on the right hand side of the image and slightly downward on the left hand side. This is because NG 4634 is not alone in the cosmos, but has a nearby companion tugging on it, just outside of Hubble’s field of view. The companion – NGC 4633 is clearly visible in this wide-field image from the Digital Sky Survey:

Digital Sky Survey image of NGC 4634 & NGC 4633, rotated to match the Hubble image. Get the full field of view or the full resolution version

Even though they’re not interacting yet the Hubble image clearly shows that NGC 4634 is already feeling the gravitational effects of it’s neighbor, NGC 4633. As the two galaxies tug on each other, their shapes begin to distort, as clearly seen by the warp in NGC 4634’s disk. But something else is going on as well – as gas clouds are tugged about the disk of NGC 4634, they collide with slower-moving material. When clouds collide, gravity takes over and stars eventually form within them.

But don’t take my word for it, just look at the Hubble image and you’ll see pink cloud formations that are billowing from the radiation of hot, newly formed stars within. And then there’s all of these jewel-like clusters of very hot, massive stars that have formed all along the length of the galaxy’s disk!

Over the next billion years (or so), these two galaxies will merge, first by passing through one another, and eventually coalesce to form one large elliptical-shaped galaxy. All of the while, new stars will be bursting into life as more and more of the clouds come together and gravity starts working its magic. Should be a very cool show indeed!

Hubble’s view of an edge-on starburst galaxy

Hubble image of NGC 7090
NGC 7090, as seen by the Hubble Space Telescope. Click for full-resolution awesomeness!

Holy Wow, what a beauty! This is NGC 7090, a spiral galaxy seen nearly edge-on, which means we cannot directly see the arrangement of its spiral arms. When we look at spiral galaxies, we typically see these hot blue stars in the spiral arms.

But NGC 7090 is really actively hatching new stars, and we can see them clearly in the pink patches that dot the galaxy. Those pink regions are cooler clouds of hydrogen gas, inside of which stars are forming. Also, those pink clouds are … pink which means they’re warm enough to be illuminated by recently formed hot stars within.

There is a lot of dust seen in silhouette against the bright core of the galaxy way behind in the distance. It’s not unlike looking at the center of our own Milky Way – the best we can do is look towards the center because of all of the intervening gas and dust that absorbs visible light. To see any beter we must turn to infrared and radio.

Of course, Hubble has a rather narrow field of view compared to other telescopes. With a decent ground-based image, you can get the entire galaxy in the field of view, and that’s what amateur astronomer Steve Crouch did in his magnificent image of NGC 7090. Below is Steve’s image, rotated to roughly line up with the Hubble image:

Wide field view of NGC 7090
Steve Crouch’s image of NGC 7090.

BTW, NGC 7090 is located about thirty million light-years from the Sun in the southern constellation of Indus.

See NASA’s writeup of NGC 7090 for more info.