NASA JPL-Caltech | Spitzer | 2012 Feb 29
Orion's Rainbow of Infrared Light
This new view of the Orion nebula highlights fledging stars hidden in the gas and clouds. It shows infrared observations taken by NASA's Spitzer Space Telescope and the European Space Agency's Herschel mission, in which NASA plays an important role.
A star forms as a clump of this gas and dust collapses, creating a warm glob of material fed by an encircling disk. These dusty envelopes glow brightest at longer wavelengths, appearing as red dots in this image. In several hundred thousand years, some of the forming stars will accrete enough material to trigger nuclear fusion at their cores and then blaze into stardom.
The nebula is found below the three belt stars in the famous constellation of Orion the Hunter, which appears at night in northern latitudes during fall and then throughout winter. At a distance of around 1,500 light-years away from Earth, the nebula cannot quite be seen with the naked eye. Binoculars or a small telescope, however, are all it takes to get a good look in visible light at this stellar factory.
Spitzer is designed to see shorter infrared wavelengths than Herschel. By combining their observations, astronomers get a more complete picture of star formation. The colors in this image relate to the different wavelengths of light, and to the temperature of material, mostly dust, in this region of Orion. Data from Spitzer show warmer objects in blue, with progressively cooler dust appearing green and red in the Herschel datasets. The more evolved, hotter embryonic stars thus appear in blue.
The combined data traces the interplay of the bright, young stars with the cold and dusty surrounding clouds. A red garland of cool gas also notably runs through the Trapezium, the intensely bright region that is home to four humungous blue-white stars, and up into the rich star field.
Infrared data at wavelengths of 8.0 and 24 microns from Spitzer are rendered in blue. Herschel data with wavelengths of 70 and 160 microns are represented in green and red, respectively.
Credit: ESA/NASA/JPL-Caltech/N. Billot (IRAM)
Astronomers have spotted young stars in the Orion nebula changing right before their eyes, thanks to the European Space Agency's Herschel Space Observatory and NASA's Spitzer Space Telescope. The colorful specks -- developing stars strung across this image -- are rapidly heating up and cooling down, speaking to the turbulent, rough-and-tumble process of reaching full stellar adulthood.
The rainbow of colors represents different wavelengths of infrared light captured by both Spitzer and Herschel. Spitzer is designed to see shorter infrared wavelengths than Herschel. By combining their observations, astronomers get a more complete picture of star formation. NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the Spitzer mission for NASA, and also plays an important role in the European Space Agency-led Herschel mission.
In the portion of the Orion nebula pictured here, the telescopes' infrared vision reveals a host of embryonic stars hidden in gas and dust clouds. These stars are at the very earliest stages of evolution.
A star forms as a clump of this gas and dust collapses, creating a warm glob of material fed by an encircling disk. In several hundred thousand years, some of the forming stars will accrete enough material to trigger nuclear fusion at their cores, and then blaze into stardom.
Herschel mapped this region of the sky once a week for six weeks in the late winter and spring of 2011. To monitor for activity in protostars, Herschel's Photodetector Array Camera and Spectrometer probed long infrared wavelengths of light that trace cold dust particles, while Spitzer gauged the warmer dust emitting shorter infrared wavelengths. In this data, astronomers noticed that several of the young stars varied in their brightness by more than 20 percent over just a few weeks. As this twinkling comes from cool material emitting infrared light, the material must be far from the hot center of the young star, likely in the outer disk or surrounding gas envelope. At that distance, it should take years or centuries for material to spiral closer in to the growing starlet, rather than mere weeks.
A couple of scenarios under investigation could account for this short span. One possibility is that lumpy filaments of gas funnel from the outer to the central regions of the star, temporarily warming the object as the clumps hit its inner disk. Or, it could be that material occasionally piles up at the inner edge of the disk and casts a shadow on the outer disk.
"Herschel's exquisite sensitivity opens up new possibilities for astronomers to study star formation, and we are very excited to have witnessed short-term variability in Orion protostars," said Nicolas Billot, an astronomer at the Institut de Radioastronomie Millimétrique (IRAM) in Grenada, Spain who is preparing a paper on the findings along with his colleagues. "Follow-up observations with Herschel will help us identify the physical processes responsible for the variability."
Fledgling stars flicker in the heart of Orion
ESA Space Science | 2012 Feb 29
Astronomers using ESA’s Herschel and NASA’s Spitzer space telescopes have detected surprisingly rapid changes in the brightness of embryonic stars within the well-known Orion Nebula.
Images from Herschel’s far-infrared instrument and two of Spitzer’s instruments working at shorter wavelengths give us a more detailed picture of stars growing in the heart of one of the most famous objects in the night sky.
The Orion Nebula is 1350 light years from Earth, and appears prominently in the winter skies for European observers.
Sometimes referred to as the Sword of Orion, the nebula lies below the three stars that form the belt of Orion the Hunter, one of the most easily recognised constellations.
It is one of the few nebulas visible to the naked eye and is a popular target for amateur astronomers.
The nebula contains the nearest site of massive star formation, with intense ultraviolet light from hot young stars causing gas and dust in the region to glow.
Inside that dust – hidden at visible wavelengths – is a host of even younger stars, still growing in their earliest phase of evolution.
This new combined far- and mid-infrared image cuts through the obscuring dust and reveals these embryonic stars.
A star forms when a dense cloud of gas and dust coalesces and then collapses under its own gravity, creating a central warm protostar surrounded by a swirling disc and a larger envelope.
Much of this material will spiral in and collect on to the star over hundreds of thousands of years, before nuclear fusion is triggered at the core and it becomes a fully-fledged star.
Some of the remnant gas and dust in the disc may go on to form a planetary system – as happened with our Solar System.
A team of astronomers led by Nicolas Billot of the Institut de Radioastronomie Millimétrique, in Granada, Spain used Herschel to image the Orion Nebula region once a week for six weeks in the late winter and spring last year.
Herchel’s PACS Photodetector Array Camera and Spectrometer detected cold dust particles in discs around the youngest protostars at far-infrared wavelengths.
This was combined with archival Spitzer images taken at shorter, mid-infrared wavelengths, which show older, hotter objects.
Astronomers were surprised to see the brightness of the young objects varying by more than 20% over just these few weeks, since the accretion process should take years or even centuries. They now have to explain why this is happening.
One possibility is that lumpy filaments of gas are funnelling from the outer disc towards central regions near the star, temporarily warming the inner disc and leading it to brighten.
Another scenario is that cold material is piling up at the inner edge and casting shadows on the outer disc, causing it to darken temporarily.
In either case, it is clear that the gestation of baby stars is anything but a smooth, uniform process.
“Yet again, Herschel observations surprise us and provide more interesting insights in to what happens during the very earliest phases of stars and planet formation,” comments Göran Pilbratt, ESA’s Herschel Project Scientist.
It is only through the unprecedented far-infrared sensitivity and resolution of the Herschel space observatory, combined with the shorter-wavelength data from Spitzer, that astronomers are able to witness and fully discover the physical processes of star birth.
Astronomers See Stars Changing Right Before Their Eyes in Orion Nebula
Universe Today | Nancy Atkinson | 2012 Feb 29