Slideshow: Classic Hubble Hits

The pawprint of a cosmic cat comes into sharper focus in this week's featured picture from the European Southern Observatory. This image of the Cat's Paw Nebula, released on Monday, combines data from the 2.2-meter MPG/ESO telescope at ESO's La Silla Observatory in Chile with 60 hours of exposures from a 400mm telescope manned by expert amateur astronomers Robert Gendler and Ryan M. Hannahoe.

ESO says the additional color information from the amateurs brings out the faint blue nebulosity at the center of the "paw," while the ESO imagery fleshes the picture out with more detail. "The result is an image that is much more than the sum of its parts," the ESO team says in an image advisory. The nebula lies in the constellation Scorpius, 5,500 light-years from Earth. The Cat's Paw is considered one of the most active star formation regions in our galaxy. Let's just hope some astronomical image enhancement engineer doesn't try to airbrush out the cat.

Where in the Cosmos
The Cat's Paw Nebula served as today's "Where in the Cosmos" picture puzzle on the Cosmic Log Facebook page. Every week, I've been posting a picture to the page and asking Cosmic Log followers to guess the cosmic location. This week, the first folks to identify the nebula were Bob Conway, Dave Smith and Neal Patel. To reward their sharp eyes, quick minds and fast typing fingers, all three are eligible to receive a pair of 3-D glasses, provided courtesy of Microsoft Research. Hit the "like" button on the Cosmic Log Facebook page and get ready for next week's "Where in the Cosmos" contest.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

The sparkles of hidden stars are revealed in a picture of the Orion Nebula that shows off the colors of the infrared rainbow.

Do you see those twinkling lights, strung along a line that starts at the top right corner of the image? Those are stars in the earliest stages of their evolution, swathed in clouds of gas and dust. Astronomers focused on those protostars with the infrared-sensitive cameras of NASA's Spitzer Space Telescope and the European Space Agency's Herschel space telescope.

This color-coded image shows the scene as observed by Spitzer in one set of infrared wavelengths (8.0 and 24 microns, shown here in shades of blue), and by Herschel in somewhat longer wavelengths (70 and 160 microns, shown in green and red, respectively). Herschel monitored the emissions from cold dust particles once a week for six weeks, while Spitzer kept track of the emissions from the warmer dust, filling out the infrared rainbow.

Astronomers found that the stars' brightness in infrared wavelengths varied by more than 20 percent during the observational time frame. That's surprising, because the astronomers expected variations in brightness to play out over a time frame measured in years or even centuries rather than weeks.

What could cause the short-term twinkling? The astronomers theorized that lumpy filaments of gas might be streaming inward from a star's outer environs, temporarily warming up the dusty disk of material surrounding the star. An alternative hypothesis would be that material occasionally piles up on the inner edge of the disk, casting 'shadows" that temporarily darken the outer disk. In any case, the observations from Herschel and Spitzer show that the birth process for baby stars is a rough-and-tumble affair, with significant ups and downs.

Members of the Herschel science team, led by Nicolas Billot, an astronomer at the Institut de Radioastronomie Millimetrique in Grenada, Spain, are preparing a paper about their findings.

"Herschel's exquisite sensitivity opens up new possibilities for astronomers to study star formation, and we are very excited to have witnessed short-term variability in Orion protostars," Billot said today in a photo advisory. "Follow-up observations with Herschel will help us identify the physical processes responsible for the variability."

More infrared wonders:

• VISTA takes a fresh look at Helix Nebula's golden eye
• 'Pillars of Creation' reloaded in infrared and X-rays
• Our galaxy's mysterious twist
• Greatest hits from Herschel

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

This beautiful Necklace Nebula, situated 15,000 light-years away in the constellation Sagitta and sighted by the Hubble Space Telescope, is the result of a stellar smash-up that happened long ago.

When stars the size of our sun near the ends of their lives, they're prone to puff away their outer layers, creating glowing shells of gas and dust. These shells can take on the appearance of rings, or globes, or even complex butterfly shapes. Centuries ago, when astronomers looked at these phenomena through their telescopes, they looked like fuzzy, blobby planets — and they've been known as "planetary nebulae" ever since.

In today's image advisory, the Hubble team says this particular planetary nebula came about when an agingi giant star whirled too close to its sun-sized companion, setting off a huge explosion. Because the stars were spinning around each other, most of the blast debris was ejected in a ringlike pattern, like water shooting out from a sprinkler. The jewels in the "necklace" are dense knots of hydrogen and oxygen gas thrown out by the blast. Scientists speculate that the gas clumped up because it was following magnetic field lines, or because of density fluctuations in the stars themselves.

Hubble took this picture of the scene on July 2, using the Wide Field Camera 3. The image is color-coded to reflect emissions in wavelengths associated with different elements: hydrogen (blue), oxygen (green) and nitrogen (red).

We're seeing the nebula today as it was 15,000 years ago, and astronomers surmise that the necklace ring was created about 5,000 years before that — which is just the blink of an eye in cosmic terms. The clumps are glowing in this picture because the gas is lit up by the ultraviolet radiation coming from the shattered stars. You can see the stars as a single bright dot at the ring's center. They're too close to each other to be made out separately, but based on repeated observations, astronomers surmise that the beat-up stars are still spinning around each other every 1.2 Earth days.

From this far away, the nebula looks like a wearable piece of jewelry — but the ring is actually 12 trillion miles wide, which is wider than our own planetary system. You couldn't wear this necklace, even if your head was as big as Pluto's orbit.

More about planetary nebulae:

• Astronomers aim to score cosmic goal
• New clues to amazing space shapes
• Student 'hoots' for Owl Nebula in contest
• Dying star belches up a toxic brew
• Slideshow: Hubble's greatest hits