Today’s nebula news is brought to you by the letter “O.”
—Picture courtesy NASA/JPL-Caltech
In a new infrared picture from NASA’s Spitzer Space Telescope, a nebula known as RCW 120 makes a brilliant green “O” against a starry patch of sky.
It may look like a portal to Hell ripped through the fabric of spacetime, but this nebula is actually a bubble of gas and dust that’s formed around an “O” type star, the most massive stellar giants known to exist.
O stars appear blue in visible light and are very hot: Surface temperatures can be higher than 73,340 degrees Fahrenheit (40,727 degrees Celsius).
Because they are so bulky, O stars live fast and die young. Their intense radiation lights up their stellar nurseries shortly after they’re born, and they blow themselves apart as supernovae just a few million years later.
Bubbles like this one are found encircling O stars across the galaxy. In fact, the smaller objects near the bottom right of this frame may be similar rings deeper in space.
RCW 120 has been known and photographed before. But the nebula, about 4,300 light-years away near the constellation Scorpius, can take on different features depending of the wavelengths of light captured to make an image.
In 2008 the European Southern Observatory used a combination of visible and submillimeter light to take this snap of RCW 120:
—Picture courtesy ESO/APEX/DSS2/ SuperCosmos/ Deharveng(LAM)/ Zavagno(LAM)
The image shows the bright O star glowing with all its might near the center of the ring.
The powerful star is emitting huge amounts of ultraviolet radiation, which is very visibly pushing surrounding material so violently that it’s stripping the electrons from hydrogen atoms.
The freshly charged—or ionized—hydrogen gas glows deep red inside the bubble, as seen by ESO’s LABOCA camera in Chile’s Atacama Desert.
As the gas expands, it creates a shock wave that’s sweeping up interstellar gas and dust. This colder material, seen in hazy blue, is collapsing into dense clumps that are in turn becoming the seeds for new stars.
Since the youngest of these cloud clumps are relatively cold, around -418 degrees Fahrenheit (-250 degrees Celsius), it takes ESO’s submillimeter vision to make them out.
More recently, in May 2010 the European Space Agency used its Herschel infrared space observatory to examine RCW 120.
Nestled in the star-forming shock wave, Herschel found an embryonic star that’s shaping up to be one of the biggest and brightest in our galaxy.
—Picture courtesy ESA/PACS/SPIRE/HOBYS Consortia
Seen as a brighter patch near the base of the blue ring, this stellar monster is already eight to ten times as massive as our sun—and it’s still growing.
The big baby star is surrounded by an additional 2,000 solar masses of material, which means it has enough “food” to eventually get as big as stars can be: 150 solar masses.
As with the Herschel image, the new Spitzer view is in infrared, albeit in slightly different parts of the infrared spectrum. That means the blue-colored O star doesn’t shine as bright, but the surrounding ring of material shows up like a green beacon.
Because of this effect, rings like this are pretty common in Spitzer observations—so common that NASA scientists haven’t been able to catalog them all.