Breaking Waves in the Stellar Lagoon

A spectacular new NASA/ESA Hubble Space Telescope image reveals the heart of the Lagoon Nebula. Seen as a massive cloud of glowing dust and gas, bombarded by the energetic radiation of new stars, this placid name hides a dramatic reality.

The Advanced Camera for Surveys (ACS) on the NASA/ESA Hubble Space Telescope has captured a dramatic view of gas and dust sculpted by intense radiation from hot young stars deep in the heart of the Lagoon Nebula (Messier 8). This spectacular object is named after the wide, lagoon-shaped dust lane that crosses the glowing gas of the nebula.

This structure is prominent in wide-field images, but cannot be seen in this close-up. However the strange billowing shapes and sandy texture visible in this image make the Lagoon Nebula’s watery name eerily appropriate from this viewpoint too.

Located four to five thousand light-years away, in the constellation of Sagittarius (the Archer), Messier 8 is a huge region of star birth that stretches across one hundred light-years. Clouds of hydrogen gas are slowly collapsing to form new stars, whose bright ultraviolet rays then light up the surrounding gas in a distinctive shade of red.

The wispy tendrils and beach-like features of the nebula are not caused by the ebb and flow of tides, but rather by ultraviolet radiation’s ability to erode and disperse the gas and dust into the distinctive shapes that we see.

In recent years astronomers probing the secrets of the Lagoon Nebula have found the first unambiguous proof that star formation by accretion of matter from the gas cloud is ongoing in this region.

Young stars that are still surrounded by an accretion disc occasionally shoot out long tendrils of matter from their poles. Several examples of these jets, known as Herbig-Haro objects, have been found in this nebula in the last five years, providing strong support for astronomers’ theories about star formation in such hydrogen-rich regions.

The Lagoon Nebula is faintly visible to the naked eye on dark nights as a small patch of grey in the heart of the Milky Way. Without a telescope, the nebula looks underwhelming because human eyes are unable to distinguish clearly between colours at low light levels.

Charles Messier, the 18th century French astronomer, observed the nebula and included it in his famous astronomical catalogue, from which the nebula’s alternative name comes. But his relatively small refracting telescope would only have hinted at the dramatic structures and colours now visible thanks to Hubble.

Cosmic Ice Sculptures: Dust Pillars in the Carina Nebula

Click on picture for Zoom View.

Enjoying a frozen treat on a hot summer day can leave a sticky mess as it melts in the Sun and deforms. In the cold vacuum of space, there is no edible ice cream, but there is radiation from massive stars that is carving away at cold molecular clouds, creating bizarre, fantasy-like structures. These one-light-year-tall pillars of cold hydrogen and dust, imaged by the Hubble Space Telescope, are located in the Carina Nebula.

This image is a composite of Hubble observations taken of the Carina Nebula region in 2005 in hydrogen light (light emitted by hydrogen atoms) along with observations taken in oxygen light (light emitted by oxygen atoms) in 2010, both times with Hubble's Advanced Camera for Surveys. The immense Carina Nebula is an estimated 7,500 light-years away in the southern constellation Carina.

A Ghostly Cosmic Pinwheel

After looking at 20 years' worth of fabulous pictures from the Hubble Space Telescope, you might get the feeling that each new release is a variation on a theme you've seen before: a supernova remnant, interacting galaxies, new stars cocooned in their placental nebulas, and so on.

But this is something different!

The dim spiral in this image is almost spooky in its perfect symmetry. The view was captured several years ago by HST's Advanced Camera for Surveys, but a few days ago it came to light (ouch! pun alert!) on a European website devoted to Hubble's discoveries.

"So what is it?" you ask.

First, I can tell you that it's real (not an artifact), it's about 3,000 light-years away in Pegasus, and it's not associated with the bright foreground star to its right.

Second, the feature itself is designated IRAS 23166+1655, which signifies that it was spotted by the Infrared Astronomical Satellite in 1983.

"So what is it?"

It's not a spiral galaxy but rather what astronomers call a pre-planetary nebula, created when an aging, swollen star starts to shed its outer layers into space — the beginning of its death throes. In this case the shedder is an extreme carbon star, one fortified with so much carbon that there's a sooty deposit in its photosphere thick enough to block the visible light trying escape from underneath. Astronomers only know a star is there because it's still hot and thus glowing brightly in the infrared.

"But why the spiral shape?"

This isn't just any old spiral; it's a perfect fit to an Archimedean spiral, something like a jet of water coming from a spinning lawn sprinkler.

The source of this pinwheel turns out to be part of a binary system, as revealed by near-infrared images taken with the Keck II telescope. As it spews matter into space, the dying star is also slowly twirling around an unseen companion.

Observers estimate that the ejected jet is moving outward at roughly 30,000 miles (50,000 km) per hour. Knowing that, and the angular spacing between successive rings (about 4½ arcseconds), observers conclude that they're spaced about 800 years apart. That is, if you took up a stationary position near the star, one of the outward-moving spiral's arms would sweep past you every 800 years.

As it turns out, the orbital period of the binary is also about 800 years. Consistent results!

Interestingly, the pinwheel is glowing faintly, but not from the stars hidden inside it. When Mark Morris (University of California, Los Angeles) and others took stock of this remarkable image in 2006, they concluded that the illumination source isn't the 12th-magnitude foreground star at the right — more likely we're seeing this ghostly pinwheel thanks to the combined glow of stars in the galactic plane.

If you want to explore the science behind this cosmic curiosity, here is the analysis by Morris's team, and here is a link to some work by Nicolas Mauron (CNRS, France) and Patrick Huggins (New York University).

Or you can skip the science and just be a little patient. "We have a much deeper HST observation with the new Wide Field Camera 3 now scheduled for this object in early October," Morris mentioned in an email, "so we're very excited about that."

Pulverized Planet Dust Might Lie Around Double Stars

Cambridge, MA - Tight double-star systems might not be the best places for life to spring up, according to a new study using data from NASA's Spitzer Space Telescope. The infrared observatory spotted a surprisingly large amount of dust around three mature, close-orbiting star pairs. Where did the dust come from? Astronomers say it might be the aftermath of tremendous planetary collisions.

"This is real-life science fiction," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. "Our data tell us that planets in these systems might not be so lucky -- collisions could be common. It's theoretically possible that habitable planets could exist around these types of stars, so if there happened to be any life there, it could be doomed."

Drake is the principal investigator of the research, published in the Aug. 19 issue of the Astrophysical Journal Letters.

The particular class of binary, or double, stars in the study are about as snug as stars get. Named RS Canum Venaticorums, or RS CVns for short, they are separated by only about two million miles (3.2 million kilometers), or one-fiftieth the distance between Earth and our sun. The stellar pairs orbit around each other every few days, with one face on each star perpetually locked and pointed toward the other.

The close-knit stars are similar to the sun in size and are probably about a billion to a few billion years old. But these stars spin much faster, and, as a result, have powerful magnetic fields and giant, dark spots. The magnetic activity drives strong stellar winds -- gale-force versions of the solar wind -- that slow the stars down, pulling the twirling duos closer over time. And this is where the planetary chaos might begin.

As the stars cozy up to each other, their gravitational influences change, and this could cause disturbances to planetary bodies orbiting around both stars. Comets and any planets that might exist in the systems would start jostling about and banging into each other, sometimes in powerful collisions. This includes planets that could theoretically be circling in the double stars' habitable zone -- a region where temperatures would allow liquid water to exist. Though no habitable planets have been discovered around any stars beyond our sun at this point in time, tight double-star systems are known to host planets; for example, one system not in the study, called HW Vir, has two gas-giant planets.

"These kinds of systems paint a picture of the late stages in the lives of planetary systems," said Marc Kuchner, a co-author from NASA Goddard Space Flight Center in Greenbelt, Md. "And it's a future that's messy and violent."

Spitzer spotted the infrared glow of hot dusty disks, about the temperature of molten lava, around three such tight binary systems. One of the systems was originally flagged as having a suspicious excess of infrared light in 1983 by the Infrared Astronomical Satellite. In addition, researchers using Spitzer recently found a warm disk of debris around another star that turned out to be a tight binary system.

The team says that dust normally would have dissipated and blown away from the stars by this mature stage in their lives. They conclude that something -- most likely planetary collisions -- must therefore be kicking up the fresh dust. In addition, because dusty disks now have been found around four, older binary systems, the scientists know that the observations are not a fluke. Something chaotic is very likely going on.

If any life forms did exist in these star systems, and they could look up at the sky, they would have quite a view. Marco Matranga, first author of the paper, from the Harvard-Smithsonian Center for Astrophysics and now a visiting astronomer at the Palermo Astronomical Observatory in Sicily, said, "The skies there would have two huge suns, like the ones above the planet Tatooine in 'Star Wars.'"

Other authors include V.L. Kashyap of the Harvard-Smithsonian Center for Astrophysics; and Massimo Marengo of Iowa State University, Ames.

The Spitzer observations were made before it ran out of its liquid coolant in May 2009, officially beginning its warm mission.