Cat's Paw Clutches Baby Stars

Most skygazers recognize the Orion Nebula, one of the closest stellar nurseries to Earth. Although it makes for great views in backyard telescopes, the Orion Nebula is far from the most prolific star-forming region in our galaxy. That distinction may go to one of the more dramatic stellar nurseries like the Cat's Paw Nebula, otherwise known as NGC 6334, which is experiencing a "baby boom."

"NGC 6334 is forming stars at a more rapid pace than Orion - so rapidly that it appears to be undergoing what might be called a burst of star formation," said lead author Sarah Willis of the Harvard-Smithsonian Center for Astrophysics (CfA) and Iowa State University. "It might resemble a 'mini-starburst,' similar to a scaled-down version of the spectacular bursts sometimes seen in other galaxies."

NGC 6334 is a realm of extremes. The nebula contains about 200,000 suns' worth of material that is coalescing to form new stars, some with up to 30 to 40 times as much mass as our Sun. It houses tens of thousands of recently formed stars, more than 2,000 of which are extremely young and still trapped inside their dusty cocoons. Most of these stars are forming in clusters where the stars are spaced up to a thousand times closer than the stars in the Sun's neighborhood. The cause of the baby boom in NGC 6334 isn't clear. Two processes often suggested to trigger bursts of star formation are blast waves from a nearby supernova explosion, or molecular cloud collisions when galaxies smash together. Neither is the case here.

That mystery is one reason why astronomers are interested in NGC 6334. Rapid star formation is often seen in luminous starburst galaxies (like the Antennae galaxies for example). Because NGC 6334 is nearby, astronomers can probe it in much greater detail, even down to counting the numbers of individual stars of various types and ages. Starbursts also light up galaxies in the early universe, making them bright enough to study. The processes that produce these distant bursts are equally puzzling and even harder to study in detail because the objects appear so small and faint.

"Young galaxies in the early universe are small smudges of light in our telescopes, and we can only study the collective processes over the whole galaxy. Here in NGC 6334, we can count the individual stars," explained co-author Howard Smith of the CfA.

The region was observed with the Spitzer Space Telescope and the Blanco telescope at the Cerro-Tololo Inter-American Observatory. "Both space and groundbased observations were needed to identify the young stars," said Lori Allen (National Optical Astronomy Observatory), the principle investigator of the observations. The starburst in NGC 6334 began relatively recently and will last for only a few million years - a blink of the eye on cosmic timescales.

"We're lucky, not only because it's nearby but also because we're catching it while the starburst is happening," said Willis.

In the future, NGC 6334 will resemble multiple Pleiades star clusters, each filled with up to several thousand stars. Unfortunately, it won't look as impressive as the Pleiades to Earthbound telescopes because it is more than ten times farther away, at a distance of 5,500 light-years, and its location in the galactic plane obscures the region behind a lot of dust. NGC 6334, in the constellation Scorpius, spans a distance of about 50 light-years and covers an area on the sky slightly larger than the full Moon.

Image: S. Willis (CfA); ESA/Herschel ; NASA/JPL-Caltech/SSC; CTIO/NOAO/AURA/NSF [high-resolution]

Caption: Harvard-Smithsonian Center for Astrophysics

Balaur

Living 70 million years ago in what is now Romania, Balaur was originally thought to be a close relative of velociraptors, but is now considered to be an early flightless bird. Martyniuk is fascinated with its double-sickle-clawed feet, which seem to have been one of the original bird traits, he said.

Dapingfangornis

"That's one of my favorites," said Martyniuk. "I didn't know much about this bird before I did the research for my book. It almost got cut from the book because the paper describing it is so hard to get. It's only published in Chinese so far. I'm surprised that I haven't seen more depictions, because it had these long tail feathers."

Many dinosaur bird species had long tail feathers, Martyniuk said, but they're only found in about half the fossils. That ratio suggests they were a sex-linked trait, perhaps found only among males, like the fantastic tails of modern birds of paradise.

Hongshanornis

Though dinosaur species are often known from a bone or two, Hongshanornis remains are complete enough to know that it had a crest on its head and long, spindly legs perhaps suited to wading.

"It seems to be analogous to a sandpiper," said Martyniuk. "It shows that a lot of these birds we have around today had some kind of parallel in the Mesozoic. It's not just pterodactyls flying around."

Ichthyornis

"There's a conception that different birds emerged from different dinosaurs, that there are, say, ostrich dinosaurs, and that's where ostriches evolved from," Martyniuk said. "But when you get down into the nitty-gritty anatomy, all modern birds probably evolved from something like Ichthyornis, a generalist seabird that managed to make it through the big extinction at the end of the Cretaceous."

Has any paleontological discovery of the 21st century been so transformative as the fact that dinosaurs were feathered?

Sure, biologists still have academically foundational arguments over the proper positions of various protoplasmic goos at the tree of life's trunk, but what shakes the trunk doesn't always sway the branches. Not like dinosaurs — the charismatic megafauna of our collective childhood imaginations, now with feathers.

The dinosaur history books have literally been redrawn, and among the artists is Matthew Martyniuk, author and illustrator of the Field Guide to Mesozoic Birds and Other Winged Dinosaurs. Inside, using the field guide format that's introduced so many people to nature, he introduces readers to dozens of dinosaurs that would, over millions of years, evolve into modern-day birds.

"I've always been interested in bird evolution. It seemed there were so many books illustrating prehistoric animals, but none focusing on bird origins," said Martyniuk. "A lot of their characteristics go pretty deep into what were traditionally considered dinosaurs, and are really making us rethink how they would have looked in real life."

On the following pages, Martyniuk takes Wired on a tour of his dino-bird world.

Jinfengopteryx elegans

After its discovery in 2005, Jinfengopteryx was thought by some paleontologists to be the oldest bird of all, a forerunner of Archaeopteryx, the original first-bird title-holder. New studies suggest that's not the case, but it's still a fantastic creature.

The name translates to "elegant golden phoenix feather," and rightly so: Jinfengopteryx is among the most beautiful fossils in existence, and so well-preserved that the remains of its last meal can be seen in its stomach.

Coloration is a matter of some conjecture, but patterns in the fossil impressions do suggest an alternation between light and dark hues, Martyniuk said.

Boluochia

Gracing the cover of Mesozoic Birds are a pair of squabbling Boluochia, which lived 120 million years ago in what is now northeastern China. The region is home to fantastically preserved fossil deposits that have yielded most of the feathered specimens to date. Boluochia was among the first of these.

Martyniuk picked it for the cover because it occupies the intersection of dinosaur and avian that he finds so fascinating. "It's approaching modern birds, but has these weird, big teeth," he said.

The field guide premise is intended to de-mystify those early creatures, which people often "look at as fantastic, dragon-like things that are hyper-real. By presenting them this way, it highlights the fact that these were, once upon a time, real animals that looked and behaved similarly to the way animals do today," Martyniuk said.

Microraptor

Pigments decay over time — but if a fossil preserves the microscopic physical structures that generate iridescent color, its hues can be inferred after millions of years. Such was the case with Microraptor, which appears to have possessed dark, iridescent plumage. "I went with dark blue, like a grackle," said Martyniuk.

Microraptor's feathers also appear to have been adapted to flight, though its skeleton was not. "Feathers seem to be more malleable in terms of evolutionary selection," he said. "It's a creature that was just starting to adapt to living in trees or flying. The skeleton has yet to catch up with the feathers."

Ningyuansaurus

Scheduled to be published in the upcoming second edition of Mesozoic Birds, Ningyuansaurus was an early oviraptor, or egg-stealing dinosaur. One lineage of its own descendants would eventually become birds.

Wulatelong

Wulatelong, depicted here with lizard prey, was described for the first time in May in the little-known journal Vertebrata PalAsiatica.

Many new dinosaur species, especially those from China, are reported in this fashion, with no fanfare and little public attention. Martyniuk and other enthusiasts scan the journals, sifting for discoveries like paleontologists hunt for bones.

Aurornis

As with many early bird fossils, scientists know that Aurornis -- which was announced late in May, and may be the earliest known bird -- had feathers, but their exact shape and distribution is a matter of inference.

Martyniuk takes a naturalistic approach. Too many dino-bird artist representations "look like people just took our traditional ideas of dinosaurs and stuck feathers on, without thinking of how feathers fit and move, of how they change the profiles of modern animals," Martyniuk said. "They're traditional dinosaurs dressed up in a furry overcoat -- which is absolutely not how it is with modern birds."

Black Hole Bonanza

Data from NASA's Chandra X-ray Observatory have been used to discover 26 black hole candidates in the Milky Way's galactic neighbor, Andromeda, as described in our latest press release. This is the largest number of possible black holes found in a galaxy outside of our own.

A team of researchers, led by Robin Barnard of the Harvard-Smithsonian Center for Astrophysics, used 152 observations of Chandra spanning over 13 years to find the 26 new black hole candidates. Nine were known from earlier work. These black holes belong to the stellar-mass black hole category, which means they were created when a massive star collapsed and are about 5 to 10 times the mass of the Sun.

This wide-field view of Andromeda contains optical data from the Burrell Schmidt telescope of the Warner and Swansey Observatory on Kitt Peak in Arizona. Additional detail of the core and dust in the spiral arms comes from an image taken by astrophotographer Vicent Peris using data from two of his personal telescopes. In this combined optical image, red, green, and blue show different bands from the visible light portion of the electromagnetic spectrum.

The inset contains X-ray data from multiple Chandra observations of the central region of Andromeda. This Chandra image shows 28 of the 35 black hole candidates in this view, visible by mousing over the image. The other seven candidates can be seen in this Chandra image with a larger field of view.

Seven of the 35 black hole candidates are within only 1,000 light years of the Andromeda Galaxy's center (mouse over the image for the dotted circle enclosing these sources). This is more than the number of black hole candidates with similar properties located near the center of our own Galaxy. This, however, does not take astronomers by surprise, since the bulge of stars in the middle of Andromeda is bigger, allowing more black holes to form.

Eight of the nine black hole candidates that were previously identified are associated with globular clusters, the ancient concentrations of stars distributed in a spherical pattern about the center of the galaxy. This also differentiates Andromeda from the Milky Way as astronomers have yet to find a similar black hole in one of the Milky Way's globular clusters. Andromeda, also known as Messier 31 (M31), is a spiral galaxy located about 2.5 million light years away. It is thought that the Milky Way and Andromeda will collide several billion years from now. The black holes located in both galaxies will then reside in the large, elliptical galaxy that results from this merger. These results are available online and will be published in the June 20th issue of The Astrophysical Journal. Many of the Andromeda observations were made within Chandra's Guaranteed Time Observer program.

Image: X-ray (NASA/CXC/SAO/R.Barnard, Z.Lee et al.), Optical (NOAO/AURA/NSF/REU Prog./B.Schoening, V.Harvey; Descubre Fndn./CAHA/OAUV/DSA/V.Peris) [high-resolution]

Caption: Chandra X-ray Telescope

Changing Neptune Seasons

NASA Hubble Space Telescope observations in August 2002 show that Neptune's brightness has increased significantly since 1996. The rise is due to an increase in the amount of clouds observed in the planet's southern hemisphere. These increases may be due to seasonal changes caused by a variation in solar heating. Because Neptune's rotation axis is inclined 29 degrees to its orbital plane, it is subject to seasonal solar heating during its 164.8-year orbit of the Sun. This seasonal variation is 900 times smaller than experienced by Earth because Neptune is much farther from the Sun. The rate of seasonal change also is much slower because Neptune takes 165 years to orbit the Sun. So, springtime in the southern hemisphere will last for several decades! Remarkably, this is evidence that Neptune is responding to the weak radiation from the Sun. These images were taken in visible and near-infrared light by Hubble's Wide Field and Planetary Camera 2.

Image: NASA, L. Sromovsky, and P. Fry (University of Wisconsin-Madison) [high-resolution]

Caption: Hubble Heritage Team

Guts of a Dead Star

Suspended in time and space, the aftermath of a massive star’s dramatic ending in a supernova explosion is captured by ESA’s XMM-Newton space observatory. Nested knots of hot gas glowing green at X-ray wavelengths – equivalent to millions of degrees celsius – fill the structured central region of this expanding supernova remnant.

Supernova remnants are the glowing fireballs created after a massive star – greater than eight of our Suns – has exhausted its fuel supply and collapses in on itself, ejecting its remaining layers of gas in a blinding explosion. A neutron star or black hole may remain at the heart of the explosion, obscured by the expanding shell of ejected material that also contains material swept up from the interstellar medium – the space between stars.

In this image, two bright spots at the right edge of the shell are lit up by the interaction of shock waves with the surrounding medium. This supernova remnant is only a few thousand years old – the expansion of the shock will take hundreds of thousands of years to slow down. By studying supernova remnants at X-ray wavelengths, astronomers can identify the abundance and distribution of different elements forged during the last stages of the star’s life.

This information can provide clues about the mass of the progenitor star and the dynamics of the explosion. Blue and white specks in and around the remnant are foreground and background stellar objects.

Image: XMM-Newton/ESA [high-resolution]

Caption: ESA

Warm Venus Volcano

This figure shows the volcanic peak Idunn Mons (at 46 degrees south latitude, 214.5 degrees east longitude) in the Imdr Regio area of Venus. The topographic backbone derives from data obtained by NASA's Magellan spacecraft, with a vertical exaggeration of 30 times. Radar data (in brown) from Magellan has been draped on top of the topographic data. Bright areas are rough or have steep slopes. Dark areas are smooth.

The colored overlay in Figure 1 shows the heat patterns derived from surface brightness data collected by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS), aboard the European Space Agency's Venus Express spacecraft. Temperature variations due to topography were removed. The brightness signals the composition of the minerals that were changed due to lava flow. Red-orange is the warmest area and purple is the coolest. The warmest area is centered on the summit, which stands about 2.5 kilometers (1.6 miles) above the plains, and the bright flows that originate there. Idunn Mons has a diameter of about 200 kilometers (120 miles).

The spectrometer data was collected from May 2006 to the end of 2007. A movie featuring 360-degree views of the volcano is based on the same data and can be viewed at JPL's Multimedia.

Image: NASA/JPL-Caltech/ESA [high-resolution]

Caption: NASA/JPL

Cloud in Serpens

As the realm of galaxies slowly slides past it prime, the dim and dusty clouds that float above the plane of our galaxy harbingers the rise of galactic center. Here then is one of those clouds in Serpens that is punctuated by the dazzle of embedded and breakout stars.

The *only* thing that came to my mind while working on this data was the Electric Company (or Sesame Street) animated short that begins with the name of this object (e.g. 123...) This is most certainly an American (me) generational thing. Be forewarned, it might stick in your mind for a while.

Image: Adam Block/Mount Lemmon SkyCenter/University of Arizona [high-resolution]

Caption: Adam Block