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All posts for the month October, 2009

As the Stars in the Night Sky

The gorgeous southern skies cluster NGC 4755, as seen by ESOs Wide Field Imager (WFI) on the MPG/ESO 2.2-meter telescope at ESOs La Silla Observatory.

The gorgeous southern skies cluster NGC 4755, as seen by ESO's Wide Field Imager (WFI) on the MPG/ESO 2.2-meter telescope at ESO's La Silla Observatory.

Wow.

That’s all I can say about one of the latest images from the European Southern Observatory in Chile. This is the “Jewel Box” cluster, one of the loveliest open clusters in the sky.  It’s not one of the brightest things to see — you can just barely make it out with the naked eye. But, if you look at it through binoculars or  a smal telescope, you can start to see the jewel-like stars that give this cluster its name.  There are some amazing color contrasts between the brightest stars in the cluster — ranging from pale blue to golden orange stars.

Open clusters like this one can have anywhere from a few stars to thousands of them. They travel together through space, held together by their mutual gravitational attraction. They form together and stay together for a long time as they move through space.  Because the stars all formed together from the same cloud of gas and dust their ages and chemical makeup are similar, which makes them ideal laboratories for studying how stars evolve.

A closeup view of the Jewel Box cluster taken with the ESOs VLT observatory in Chile.

A closeup view of the heart of the Jewel Box cluster taken with the ESO's VLT observatory in Chile.

Okay, this is gorgeous to look at in a wide field of view, but what if you looked at the heart of the Jewel Box?  You’d use a  telescope such as the FORS1 instrument on the ESO Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile, and you’d get a very sharp closeup view of the heart of the cluster. You can start to distinguish stars from each other and their colors are really quite strikingly different, glittering like diamonds on a fancy brooch.

You start to notice how the brightnesses of the different stars contrast with each other. That huge variety in brightness is because the brighter stars are 15 to 20 times the mass of the Sun, while the dimmest stars are less than half the mass of the Sun. More massive stars shine much more brilliantly. They also age faster and make the transition to giant stars much more quickly than their faint, less-massive siblings.  This is another reason why astronomers like to study stars in clusters — their masses, ages, and sizes give them a range of stellar evolution to study.

Okay, so what if you wanted to really zero in on the stars in the Jewel Box?  You’d aim the Hubble Space Telescope at the cluster and use the  multi-wavelength capability of the telescope to give you optical, infrared, and ultraviolet views of those stars. And the view would be just as exhilirating as the images from Chile.

HSTs view of the central region of the Jewel Box Cluster.

HST's view of the central region of the Jewel Box Cluster.

This new Hubble image of the core of the Jewel Box cluster is the first comprehensive far ultraviolet to near-infrared image of an open galactic cluster.  HST imaged it using seven filters, which permit details of the stars at different wavelengths to shine through.

The image was taken near the end of the long life of the Wide Field Planetary Camera 2 — Hubble’s workhorse camera. You can see several very bright, pale blue supergiant stars, a solitary ruby-red supergiant and a variety of other brilliantly colored stars in HST’s view. There are also many very faint stars, showing just how populous this cluster and its environment are. The intriguing colors of many of the stars result from their differing intensities at different ultraviolet wavelengths, which tell astronomers a great deal about the temperatures and chemical compositions of those stars and their gaseous atmospheres. So, as you can see, there’s value in the wide-field view and the zoom-in — and each view tells astronomers a great deal about this starry jewel box. Enjoy!

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The Factor That Keeps Us Looking Up

The N44 superbubble complex as seen by the Gemini Telescope (courtesy Gemini Observatory and T.A. Rector).
Use slider to zoom in on the image.  (Courtesy John Williams at Terrazoom.)

Astronomy and space science have this serious “Wow!” factor that really engage people’s attention. If nothing else, the “pretty pictures” grab your attention and keep it riveted for quite some time. Take this image of a star-forming nebula in the Large Magellanic Cloud (a neighboring galaxy to the Milky Way Galaxy). It was taken using the Gemini Observatory and the image just draws your eye. Before you know it, you’re taking in the shape of the cloud and the stars in the field.

The evidence before your eyes speaks to the incredible processes that take place in the universe.  Of course, the first time you look at an image like this, you probably aren’t sure what you’re seeing beyond some fluffy stuff and a bunch of gorgeous stars. Don’t feel bad about not knowing what you’re seeing. Astronomers have that experience, too.  But, once they get over their awe at what they see, they get right down to work, using all the tools and knowledge they have at their disposal to figure out the what, when, where, why, and how of the processes that form what they see.

If you know an astronomer or an astronomy buff, this may give you some insight into what makes them tick — what makes them keep looking up, night after night. It’s the beauty, the awe-inspiring views, the “Wow!” factor that keeps them (and all of us who love the night skies) coming back for more!