RCW 38 is a dense star cluster about 5500 light years away in the direction of the constellation Vela (the Sails). Like the Orion Nebula Cluster, RCW 38 is an embedded cluster, in that clouds of dust and gas still envelop its stars.
Inside RCW 38, young stars bombard fledgling suns and planets with powerful winds and blazing light and some short-lived, massive stars explode as supernovae, whick sometimes cooks away the matter that would otherwise form new solar systems.
Did our own solar system form in that sort of hellish environment?
Astronomers have determined that most stars, including the low mass, reddish ones that outnumber all others in the Universe, originate in these matter-rich locations. Accordingly, embedded clusters provide scientists with a living laboratory in which to explore the mechanisms of star and planetary formation.
The RCW 38 massive cluster of stars, beginning with a wide angle view made with an amateur telescope, then using an image from Digitized Sky Survey 2, an image made with the MPG/ESO 2.2-metre telescope at La Silla and concluding with an image made with the NACO adaptive optics instrument attached to ESO’s Very Large Telescope. Credit: ESO, Digitized Sky Survey 2, A. Fujii. Music by John Dyson from the CD Darklight
“By looking at star clusters like RCW 38, we can learn a great deal about the origins of our Solar System and others, as well as those stars and planets that have yet to come”, says Kim DeRose, first author of the new study that appears in the Astronomical Journal. DeRose did her work on RCW 38 as an undergraduate student at the Harvard-Smithsonian Center for Astrophysics, USA.
Using the NACO adaptive optics instrument on ESO’s Very Large Telescope , astronomers have obtained the sharpest image yet of RCW 38. They focused on a small area in the centre of the cluster that surrounds the massive star IRS2, which glows in the searing, white-blue range, the hottest surface colour and temperatures possible for stars. These dramatic observations revealed that IRS2 is actually not one, but two stars — a binary system consisting of twin scorching stars, separated by about 500 times the Earth–Sun distance.
In the NACO image, the astronomers found a handful of protostars — the faintly luminous precursors to fully realised stars — and dozens of other candidate stars that have eked out an existence here despite the powerful ultraviolet light radiated by IRS2. Some of these gestating stars may, however, not get past the protostar stage. IRS2’s strong radiation energises and disperses the material that might otherwise collapse into new stars, or that has settled into so-called protoplanetary discs around developing stars. In the course of several million years, the surviving discs may give rise to the planets, moons and comets that make up planetary systems like our own.
As if intense ultraviolet rays were not enough, crowded stellar nurseries like RCW 38 also subject their brood to frequent supernovae when giant stars explode at the ends of their lives. These explosions scatter material throughout nearby space, including rare isotopes — exotic forms of chemical elements that are created in these dying stars. This ejected material ends up in the next generation of stars that form nearby. Because these isotopes have been detected in our Sun, scientists have concluded that the Sun formed in a cluster like RCW 38, rather than in a more rural portion of the Milky Way.
Wider region surrounding the star cluster RCW 38, located about 5500 light years away in the direction of the constellation Vela (the Sails). RCW 38 is an "embedded" cluster, in that the nascent cloud of dust and gas still envelops its stars. There, young, titanic stars bombard fledgling suns and planets with powerful winds and large amount of light, helped in their devastating task by short- lived, massive stars that explode as supernovae. In some cases, this energetic onslaught cooks away the matter that may eventually form new planetary systems. Scientists think that our own Solar System emerged from such a dramatic environment. Image was obtained with the Wide Field Imager instrument on the MPG/ESO 2.2-metre telescope at La Silla, using data collected through four filters (B, V, R and H-alpha). The field of view is 30 arcminutes. Credit: ESO
“Overall, the details of astronomical objects that adaptive optics reveals are critical in understanding how new stars and planets form in complex, chaotic regions like RCW 38”, says co-author Dieter Nürnberger.
The name “NACO” is a combination of the Nasmyth Adaptive Optics System (NAOS) and the Near-Infrared Imager and Spectrograph (CONICA). Adaptive optics cancels out most of the image-distorting turbulence in Earth’s atmosphere caused by temperature variations and wind.
The team is composed of K.L. DeRose, T.L. Bourke, R.A. Gutermuth and S.J. Wolk (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA), S.T. Megeath (Department of Physics and Astronomy, The University of Toledo, USA), J. Alves (Centro Astronómico Hispano Alemán, Almeria, Spain), and D. Nürnberger (ESO).
Article: Astronomical Journal: A Very Large Telescope / NACO study of star formation in the massive embedded cluster RCW 38, by DeRose et al. (2009, AJ, 138, 33-45). doi: 10.1088/0004-6256/138/1/33
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