The Omega Nebula (Messier 17), also known as the Swan Nebula because of its distinct appearance, is one of the most well-known nebulas in our galaxy. Located about 5,500 light-years from Earth in the constellation Sagittarius, this nebula is also one of the brightest and most massive star-forming regions in the Milky Way. Unfortunately, nebulas are very difficult to study because of the way their clouds of dust and gas obscure their interiors.
For this reason, astronomers are forced to examine nebulas in the non-visible wavelength to get a better idea of their makeup. Using the Stratospheric Observatory for Infrared Astronomy (SOFIA), a team of NASA scientists recently observed the Swan Nebula in the infrared wavelength. What they found has revealed a great deal about how this nebula and stellar nursery evolved over time.
(DING!) “The captain has turned off the safety lights – you are now free to explore the infrared Universe.”
Mounted inside the fuselage of a Boeing 747SP aircraft, NASA’s Stratospheric Observatory for Infrared Astronomy, or SOFIA, is capable of searching the sky in infrared light with a sensitivity impossible from ground-based instruments. Cruising at 39,000 to 45,000 feet, its 100-inch telescope operates above 99% of the atmospheric water vapor that would otherwise interfere with such observations, and thus is able to pierce through vast interstellar clouds of gas and dust to find what lies within.
Its latest discovery has uncovered a cluster of newborn stars within a giant cloud of gas and dust 6,400 light-years from Earth.
The massive stars are still enshrouded in the gas cloud from which they formed, a region located in the direction of Perseus called W3. The Faint Object Infrared Camera for the SOFIA Telescope (FORCAST) instrument was able to peer through the cloud and locate up to 15 massive young stars clustered together in a compact region, designated W3A.
W3A’s stars are seen in various stages of formation, and their effects on nearby clouds of gas and dust are evident in the FORCAST inset image above. A dark bubble, which the arrow is pointing to, is a hole created by emissions from the largest of the young stars, and the greenish coloration surrounding it designates regions where the dust and large molecules have been destroyed by powerful radiation.
Without SOFIA’s infrared imaging capabilities newborn stars like those seen in W3A would be much harder to observe, since their visible and ultraviolet light typically can’t escape the cool, opaque dust clouds where they are located.
The radiation emitted by these massive young stars may eventually spur more star formation within the surrounding clouds. Our own Sun likely formed in this same way, 5 billion years ago, within a cluster of its own stellar siblings which have all long since drifted apart. By observing clusters like W3A astronomers hope to better understand the process of star birth and ultimately the formation of our own solar system.
The observation team’s research principal investigator is Terry Herter of Cornell University. The data were analyzed and interpreted by the FORCAST team with Francisco Salgado and Alexander Tielens of the Leiden Observatory in the Netherlands plus SOFIA staff scientist James De Buizer. These papers have been submitted for publication in The Astrophysical Journal.
Around 1957 light years away, a dense molecular cloud resides beside an OB star cluster locked in a massive HII region. The hydrogen envelope is slowly beginning to billow out and separate itself from the molecular gas, but we’re not able to get a clear picture of the situation thanks to interfering dust. However, by engaging NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA), we’re now able to take one of the highest resolution mid-infrared looks into the heart of an incredible star-forming region known as W40 so far known to science.
Onboard a modified 747SP airliner, the Faint Object infraRed Camera for the SOFIA Telescope (FORCAST) has been hard at work utilizing its 2.5 meter (100″) reflecting telescope to capture data. The composite image shown above was taken at wavelengths of 5.4, 24.2 and 34.8 microns. Why this range? Thanks to the high flying SOFIA telescope, we’re able to clear Earth’s atmosphere and “get above” the ambient water vapor which blocks the view. Not even the highest based terrestrial telescope can escape it – but FORCAST can!
With about 1/10 the UV flux of the Orion Nebula, region W40 has long been of scientific interest because it is one of the nearest massive star-forming regions known. While some of its OB stars have been well observed at a variety of wavelengths, a great deal of the lower mass stars remain to be explored. But there’s just one problem… the dust hides their information. Thanks to FORCAST, astronomers are able to peer through the obscuration at W40’s center to examine the luminous nebula, scores of neophyte stars and at least six giants which tip the scales at six to twenty times more massive than the Sun.
Why is studying a region like W40 important to science? Because at least half of the Milky Way’s stellar population formed in similar massive clusters, it is possible the Solar System also “developed in such a cluster almost 5 billion years ago”. The stars FORCAST measures aren’t very bright and intervening dust makes them even more dim. But no worries, because this type of study cuts them out of dust that’s only carrying a temperature of a few hundred degrees. All that from a flying observatory!