A bubble in the WIYNe

When  you want to study something really big in the sky, it helps to have a wide field of view. The Full Moon occupies about 1/2 of a degree in the nighttime sky, and that’s quite a nice chunk. But the folks over at the National Optical Astronomy Observatory (NOAO) are hoping to go wider with the new One Degree Imager (ODI) currently under development. As part of its commissioning, the camera was mounted to the 3.5-meter WIYN telescope and made this:

NGC 7635: The Bubble Nebula captured by the new ODI camera on WIYN. Image Credit: T.A. Rector (University of Alaska Anchorage), WIYN ODI team & WIYN / NOAO / AURA / NSF. More image sizes can be found here.

Talk about a bubble floating in the WIYNe (see what I did there? I’ll be here all week!)! This is NGC 7635, also known as the Bubble Nebula, a star forming region about 7,800 light-years away in the constellation Cassiopeia. The nebula itself is about 10 light-years across. At its center is a great bubble which is being blown by fast stellar winds coming from the bright star toward the top of the bubble. This star, known as BD+602522, is a relatively young giant star believed to be somewhere between 10 and 20 times the mass of our own Sun.

And it’s a hot star too – at 34,320K it’s more than six times hotter than our Sun*, gusting out winds of over 2,000 kilometers per second – that’s 4 million miles per hour (or 7 million kilometers per hour)! That wind is responsible for “inflating” the bubble, which itself is 2-4 light years across.

But take another look at the star and you’ll notice that it’s off center from the bubble. That’s because the “surface” of the bubble is slamming into cooler, denser gas in the walls of the nebula. But the density of the gas and dust in the nebula isn’t uniform so the outflow slams into cooler gas toward the top of the image and heats up, causing the gas to glow. Meanwhile, outflow from the star is free to pass through less-dense gas toward the bottom. The result is a squashed bubble with one edge closer to the star than the other.

The ODI is still under development. As its name implies, it is designed to take a full one-degree by one-degree high resolution image of the sky. The full image of NGC 7635 covers 25 by 25 arc minutes, just a little smaller than the full moon. But when completed, ODI is going to be one heck of a sky-grabbing machine.

According to Moore, et al (2002), it’s actually a bit cooler than expected for a star this massive.

Sugar found around a star. Sweet!

Rho Ophiuchi star-forming region in infrared, imaged by NASAs WISE spacecraft. The little red dot in the box is IRAS 16293-2422, a young binary star with a mass similar to our Sun. An artist’s impression of glycolaldehyde (C2H4O2) is shown in the disk surrounding the star.

As stars form, a swirling disc of material surrounds the young star. These dics are mostly composed of simple molecular compounds such as molecular hydrogen (H2) and carbon monoxide (CO) but there’s also some relatively complex stuff there too, including sugar!

Ok, it’s not exactly the same kind of sugar that we add to our coffee, but it’s really not that much different, either. It’s glycolaldehyde (C2H4O2) which is a fairly simple form of sugar. Sweet!

The sugar was detected by Jes Jørgensen and his team using the Atacama Large Millimeter/submillimeter Array (ALMA)  in the disc surrounding a young Sun-like star called IRAS 16293-242. The  molecular compounds in this disc are cold so they therefore they emit radiation at long wavelengths – longer than infrared, but shorter than radio. It’s here that you can start to detect complex molecules and sure enough, Jørgensen and his team found a lovin’ spoonful of glycolaldehyde!

Why is this so deliciously awesome? It turns out that glycolaldehyde is one of the ingredients found in RNA. You might remember from high school biology that RNA is similar to DNA except for the type of sugars present. (There are some other differences between RNA and DNA as well, which are worth reading up on.)

So there you have it – discs surrounding stars can have the building blocks of life in them, and it’s in these discs where planets form. It seems that the building blocks of life are fairly common and seed the formation of new planets. Sweet!

A High Energy X-Ray Superbubble

A long, long time ago in a galaxy not that far away at all as a matter of fact, a cluster of stars formed inside a great cloud of gas and dust. Among them were giant stars whose masses may have been between 10-30 times the mass of our Sun. These behemoth stars lived fast, fusing their once hydrogen cores into heavier and heavier elements until one day they could no longer sustain themselves and they explodeed as supernovae.

Like TNT exploding in a mine, the supernovae sent out powerful shock waves that blew a giant bubble in the cloud 1,200 light-years across. Behold:

Massive stars exploded as supernovae, creating superbubbles in the surrounding gas. X-Ray (blue), Optical (yellow/green), Infrared (red) composite of N44 in the Large Magellanic Cloud. Click for the 864×690 version, or get the ridiculously  cool 3600×2874 version Credit: X-ray: NASA/CXC/U.Mich./S.Oey, IR: NASA/JPL, Optical: ESO/WFI/2.2-m

Holy Cosmic Cauldrons! This region is known as N44 and resides in the Large Magellanic Cloud, a satellite galaxy to our own Milky Way. It’s actually a composite of an image of N44 taken by the Chandra X-Ray Observatory, an optical image taken by the 2.2-meter Max-Planck-ESO telescope in Chile, and the Spitzer Space Telescope.

The colors correspond to different wavelengths imaged by the different observatories. Red stands in for infrared emission captured by Spitzer. This is cooler gas and dust and is relatively “intact” surrounding the bubble.

Yellow corresponds to imagery from the Max-Planck-ESO telescope and shows hot ionized gas. This gas is glowing from the ultraviolet radiation from hot, young stars, in much the same way that gas glows in a florescent light bulb.

Finally, we have the really high-energy stuff, the x-ray emission (shown here in blue), taken by the Chandra X-Ray Observatory. In fact, let’s take a look at just the Chandra X-Ray image:

Chandra X-Ray image of star cluster NGC 1929 inside N44.

Here’s where the story gets really interesting. For a long time, it was assumed that the bubbles were created by winds from the hot stars that eventually went supernova. That makes sense. After all, the more massive and hotter they are, the more mass they lose as stellar winds.

Well, the winds from these stars certainly did “blow” out the bubbles. However, it turns out there is a lot more x-ray radiation coming from inside the bubbles than was expected from just the winds alone.

So where is this extra x-ray radiation coming from? Dr. Anne  Jaskot from the University of Michigan and her team used Chandra to find out. It turns out that there are two extra sources of x-ray radiation: the supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls. In fact, if you compare the two images above, you can actually see the X-ray radiation coming off the walls of the bubbles. Cool!

In other words, the supernova explosions themselves generated a lot of high-energy x-ray radiation by slamming into the walls of the bubble making the walls so hot they give off x-rays as the shock waves passed through.

Moreover, these shockwaves, created in the supernovae of these massive stars, compressed the surrounding gas. This in turn triggered the formation of even more stars.

And there it is, the cycle of stellar life: the ashes of stars are blown along the expanding wave of a cosmic bubble, and seed the next generation of stars.

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.