|
|
HH46/47
| Title |
HH46/47 |
| Description |
This image from NASA's Spitzer Space Telescope transforms a dark cloud into a silky translucent veil, revealing the molecular outflow from an otherwise hidden newborn star. Using near-infrared light, Spitzer pierces through the dark cloud to detect the embedded outflow in an object called HH 46/47. Herbig-Haro (HH) objects are bright, nebulous regions of gas and dust that are usually buried within dark clouds. They are formed when supersonic gas ejected from a forming protostar, or embryonic star, interacts with the surrounding interstellar medium. These young stars are often detected only in the infrared. The Spitzer image was obtained with the infrared array camera. Emission at 3.6 microns is shown as blue, emission from 4.5 and 5.8 microns has been combined as green, and 8.0 micron emission is depicted as red. HH 46/47 is a striking example of a low mass protostar ejecting a jet and creating a bipolar, or two-sided, outflow. The central protostar lies inside a dark cloud (known as a 'Bok globule') which is illuminated by the nearby Gum Nebula. Located at a distance of 1140 light-years and found in the constellation Vela, the protostar is hidden from view in the visible-light image (inset). With Spitzer, the star and its dazzling jets of molecular gas appear with clarity. The 8-micron channel of the infrared array camera is sensitive to emission from polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by the surrounding radiation field and become luminescent, accounting for the reddish cloud. Note that the boundary layer of the 8-micron emission corresponds to the lower right edge of the dark cloud in the visible-light picture. Outflows are fascinating objects, since they characterize one of the most energetic phases of the formation of low-mass stars (like our Sun). The jets arising from these protostars can reach sizes of trillions of miles and velocities of hundreds of thousands miles per hour. Outflows are clear evidence of the presence of a process that creates supersonic beams of gas. This mechanism is tightly bound to the presence of circumstellar discs which surround the young stars. Such discs are likely to contain the materials from which planetary systems form. Our Sun probably underwent a similar process some 4.5 billion years ago. Hence the interest in understanding how quickly and efficiently this mass accretion and loss process takes place in protostars. |
|
HH46/47
| Title |
HH46/47 |
| Description |
This image from NASA's Spitzer Space Telescope transforms a dark cloud into a silky translucent veil, revealing the molecular outflow from an otherwise hidden newborn star. Using near-infrared light, Spitzer pierces through the dark cloud to detect the embedded outflow in an object called HH 46/47. Herbig-Haro (HH) objects are bright, nebulous regions of gas and dust that are usually buried within dark clouds. They are formed when supersonic gas ejected from a forming protostar, or embryonic star, interacts with the surrounding interstellar medium. These young stars are often detected only in the infrared. The Spitzer image was obtained with the infrared array camera. Emission at 3.6 microns is shown as blue, emission from 4.5 and 5.8 microns has been combined as green, and 8.0 micron emission is depicted as red. HH 46/47 is a striking example of a low mass protostar ejecting a jet and creating a bipolar, or two-sided, outflow. The central protostar lies inside a dark cloud (known as a 'Bok globule') which is illuminated by the nearby Gum Nebula. Located at a distance of 1140 light-years and found in the constellation Vela, the protostar is hidden from view in the visible-light image (inset). With Spitzer, the star and its dazzling jets of molecular gas appear with clarity. The 8-micron channel of the infrared array camera is sensitive to emission from polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by the surrounding radiation field and become luminescent, accounting for the reddish cloud. Note that the boundary layer of the 8-micron emission corresponds to the lower right edge of the dark cloud in the visible-light picture. Outflows are fascinating objects, since they characterize one of the most energetic phases of the formation of low-mass stars (like our Sun). The jets arising from these protostars can reach sizes of trillions of miles and velocities of hundreds of thousands miles per hour. Outflows are clear evidence of the presence of a process that creates supersonic beams of gas. This mechanism is tightly bound to the presence of circumstellar discs which surround the young stars. Such discs are likely to contain the materials from which planetary systems form. Our Sun probably underwent a similar process some 4.5 billion years ago. Hence the interest in understanding how quickly and efficiently this mass accretion and loss process takes place in protostars. |
|
HH46/47
| Title |
HH46/47 |
| Description |
This image from NASA's Spitzer Space Telescope transforms a dark cloud into a silky translucent veil, revealing the molecular outflow from an otherwise hidden newborn star. Using near-infrared light, Spitzer pierces through the dark cloud to detect the embedded outflow in an object called HH 46/47. Herbig-Haro (HH) objects are bright, nebulous regions of gas and dust that are usually buried within dark clouds. They are formed when supersonic gas ejected from a forming protostar, or embryonic star, interacts with the surrounding interstellar medium. These young stars are often detected only in the infrared. The Spitzer image was obtained with the infrared array camera. Emission at 3.6 microns is shown as blue, emission from 4.5 and 5.8 microns has been combined as green, and 8.0 micron emission is depicted as red. HH 46/47 is a striking example of a low mass protostar ejecting a jet and creating a bipolar, or two-sided, outflow. The central protostar lies inside a dark cloud (known as a 'Bok globule') which is illuminated by the nearby Gum Nebula. Located at a distance of 1140 light-years and found in the constellation Vela, the protostar is hidden from view in the visible-light image (inset). With Spitzer, the star and its dazzling jets of molecular gas appear with clarity. The 8-micron channel of the infrared array camera is sensitive to emission from polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by the surrounding radiation field and become luminescent, accounting for the reddish cloud. Note that the boundary layer of the 8-micron emission corresponds to the lower right edge of the dark cloud in the visible-light picture. Outflows are fascinating objects, since they characterize one of the most energetic phases of the formation of low-mass stars (like our Sun). The jets arising from these protostars can reach sizes of trillions of miles and velocities of hundreds of thousands miles per hour. Outflows are clear evidence of the presence of a process that creates supersonic beams of gas. This mechanism is tightly bound to the presence of circumstellar discs which surround the young stars. Such discs are likely to contain the materials from which planetary systems form. Our Sun probably underwent a similar process some 4.5 billion years ago. Hence the interest in understanding how quickly and efficiently this mass accretion and loss process takes place in protostars. |
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Vela Pulsar: Neutron Star-Ri
…
| Title |
Vela Pulsar: Neutron Star-Ring-Jet |
| Explanation |
This stunning image [ http://chandra.harvard.edu/photo/cycle1/vela/ ] from the orbiting Chandra X-ray Observatory [ http://chandra.harvard.edu/index.html ] is centered on the Vela pulsar -- the collapsed stellar core within the Vela supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/ap960612.html ] some 800 light-years distant. The Vela pulsar is a neutron star [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/ pulsars.html ]. More massive than the Sun, it has the density of an atomic nucleus. About 12 miles in diameter it spins 10 times a second as it hurtles through the supernova debris cloud [ http://antwrp.gsfc.nasa.gov/apod/ap980425.html ]. The pulsar's [ http://www.jb.man.ac.uk/~pulsar/Education/Sounds/ sounds.html ] electric and magnetic fields accelerate particles to nearly the speed of light, powering the compact x-ray [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/ history1_xray.html ] emission nebula revealed in the Chandra picture. The cosmic crossbow shape is over 0.2 light-years across, composed of an arrow-like jet emanating from the polar region of the neutron star [ http://astro.uchicago.edu/home/web/miller/nstar.html ] and bow-like inner and outer arcs believed to be the edges of tilted rings of x-ray emitting high energy particles. Impressively, the swept back compact nebula indicates the neutron star is moving up and to the right in this picture, exactly along the direction of the x-ray jet. The Vela pulsar (and associated supernova remnant [ http://www.seds.org/billa/twn/velax.html ]) was created by a massive star which exploded over 10,000 years ago. Its awesome x-ray rings and jet are reminiscent of another well-known pulsar powered system, the Crab Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap990929.html ]. |
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Pulsar Wind in the Vela Nebu
…
| Title |
Pulsar Wind in the Vela Nebula |
| Explanation |
The Vela pulsar was born [ http://antwrp.gsfc.nasa.gov/apod/ap980425.html ] 10,000 years ago at the center of a supernova -- an exploding star [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/ supernovae.html ]. In this Chandra Observatory x-ray image [ http://chandra.harvard.edu/photo/cycle1/velawv/ index.html ], the pulsar still produces a glowing nebula at the heart of the expanding cloud of stellar debris. The pulsar [ http://www.jb.man.ac.uk/~pulsar/Education/Sounds/ sounds.html ] itself is a neutron star [ http://heasarc.gsfc.nasa.gov/docs/objects/binaries/ neutron_star_structure.html ], formed as the stellar core was compacted [ http://observe.ivv.nasa.gov/nasa/space/stellardeath/ stellardeath_3a.html ] to nuclear densities. With a strong magnetic field, approximately the mass of the Sun, and a diameter of about 20 kilometers, the Vela pulsar rotates 11 times "a second". The sharp Chandra image aids astronomers [ http://xxx.lanl.gov/abs/astro-ph/0105128 ] in understanding such extreme systems as efficient high-voltage generators [ http://chandra.harvard.edu/chronicle/0201/vela.html ] which drive structured winds [ http://antwrp.gsfc.nasa.gov/apod/ap000609.html ] of electrically charged particles. An x-ray bright nebula is created as the pulsar winds slam into the surrounding material. This view spans about 6 light-years across the central region of the much larger Vela supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/ap960612.html ]. |
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The Local Bubble and the Gal
…
| Title |
The Local Bubble and the Galactic Neighborhood |
| Explanation |
What surrounds the Sun in this neck of the Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ]? Our current best guess is depicted in the above map [ http://www.sigmaxi.org/amsci/articles/00articles/Frischcap3.html ] of the surrounding 1500 light year [ http://chandra.harvard.edu/photo/cosmic_distance.html ]s constructed from various observations and deductions [ http://www.sigmaxi.org/amsci/articles/00articles/Frisch.html ]. Currently, the Sun is passing through a Local Interstellar Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap020210.html ] (LIC), shown in violet, which is flowing away from the Scorpius-Centaurus Association [ http://www.mpifr-bonn.mpg.de/staff/tpreibis/scocen.html ] of young stars. The LIC resides in a low-density hole in the interstellar medium [ http://spacsun.rice.edu/~twg/lism.html ] (ISM) called the Local Bubble [ http://spacsun.rice.edu/~twg/pc120.html ], shown in black. Nearby, high-density molecular clouds [ http://antwrp.gsfc.nasa.gov/apod/ap010923.html ] including the Aquila Rift [ http://www.a.phys.nagoya-u.ac.jp/~ohnishi/aquila/aquila.html ] surround star forming regions, each shown in orange. The Gum Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap001107.html ], shown in green, is a region of hot ionized [ http://csep10.phys.utk.edu/astr162/lect/light/ionization.html ] hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] gas. Inside the Gum Nebula [ http://www.edpsciences.org/articles/astro/abs/1997/07/ads1235/ads1235.html ] is the Vela Supernova Remnant [ http://antwrp.gsfc.nasa.gov/apod/ap960612.html ], shown in pink, which is expanding to create fragmented shells of material like the LIC [ http://antwrp.gsfc.nasa.gov/apod/ap020217.html http://www-ssg.sr.unh.edu/tof/Outreach/Interstellar/index.html ]. Future observations should help astronomers discern more about the local Galactic Neighborhood [ http://www.sigmaxi.org/amsci/articles/00articles/frischmaterial.html#environment ] and how it might have affected Earth's past climate [ http://whyfiles.news.wisc.edu/017planet/gas_cloud2.html ]. |
|
Simulated Galaxy Cluster Vie
…
| Title |
Simulated Galaxy Cluster View |
| Explanation |
Stunningly detailed, this picture is a computer simulated view [ http://oposite.stsci.edu/pubinfo/pr/2002/06/ index.html ] of a cluster of galaxies [ http://antwrp.gsfc.nasa.gov/apod/ clusters_of_galaxies.html ] in the distant cosmos [ http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/ HierarchUni.html ]. A large, elliptical galaxy dominates this hypothetical cluster's central region surrounded by a swarm of member galaxies. Other galaxies which lie far behind the cluster are seen as numerous visible concentric arcs [ http://antwrp.gsfc.nasa.gov/apod/ap011007.html ] - lensed by [ http://www.iam.ubc.ca/~newbury/lenses/ research.html ] the enormous gravitational [ http://vela.astro.ulg.ac.be/themes/extragal/gravlens/ bibdat/ ] field dominated by dark matter [ http://antwrp.gsfc.nasa.gov/apod/ap011024.html ] within the cluster itself. Such magnificent images are expected to be achieved by the Advanced Camera for Surveys [ http://www.ball.com/aerospace/acs.html ] (ACS), one of the upgrades [ http://sm3b.gsfc.nasa.gov/mission-critical/ objectives-part1.html ] being installed on the Hubble Space Telescope during the ongoing servicing mission [ http://spaceflight.nasa.gov/shuttle/crew/grunsfeldreports/ grunsfeldreports.html ]. Compared to Hubble's workhorse Wide Field Planetary Camera 2 [ http://hubble.stsci.edu/sci.d.tech/behind_the_pictures/ wacky_shape/constructing.shtml ] (WFPC2), whose achievements include the current deep field views [ http://www.stsci.edu/ftp/science/hdf/hdf.html ] of the Universe, the new technology ACS will be twice as sharp an imager with twice the field of view and five times the sensitivity. Along with extended views of the distant cosmos, enthusiastic astronomers also plan to use the ACS to monitor our own Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap020214.html ] and to search for planets orbiting stars [ http://www.generation.net/~mariob/astro/exoplan/ intro-e.htm ] beyond the Sun. |
|
Composite Crab
| Title |
Composite Crab |
| Explanation |
The Crab Pulsar, a city-sized, magnetized neutron star [ http://antwrp.gsfc.nasa.gov/apod/ap030201.html ] spinning 30 times a second, lies at the center of this composite image of the inner region of the well-known Crab Nebula [ http://www.seds.org/messier/m/m001.html ]. The spectacular picture combines optical data (red) from the Hubble Space Telescope [ http://hubblesite.org/gallery/ ] and x-ray images (blue) from the Chandra Observatory [ http://chandra.harvard.edu/chronicle/0303/top_ten/ ], also used in the popular Crab Pulsar movies [ http://chandra.harvard.edu/photo/2002/0052/movies.html ]. Like a cosmic dynamo [ http://chandra.harvard.edu/chronicle/0201/vela.html ] the pulsar powers [ http://antwrp.gsfc.nasa.gov/apod/ap010602.html ] the x-ray and optical emission from the nebula, accelerating charged particles and producing the eerie, glowing x-ray jets. Ring-like structures are x-ray emitting regions where the high energy particles slam into the nebular material. The innermost ring is about a light-year across. With more mass than the Sun [ http://www.sunblock99.org.uk/sb99/fact/heavy.html ] and the density of an atomic nucleus [ http://hyperphysics.phy-astr.gsu.edu/hbase/ nuclear/nucuni.html#c2 ], the spinning pulsar is the collapsed core of a massive star that exploded, while the nebula is the expanding remnant of the star's outer layers. The supernova explosion was witnessed in the year 1054 [ http://www.seds.org/messier/more/m001_sn.html ]. |
|
Young Star, Dark Cloud
| Title |
Young Star, Dark Cloud |
| Explanation |
High-speed outflows of molecular gas from a young stellar object glow in infrared light, revealing themselves in this recent false-color image from the Spitzer Space Telescope [ http://www.spitzer.caltech.edu/Media/releases/ssc2003-06/ ssc2003-06f.shtml ]. Cataloged as [ http://www-astro.phast.umass.edu/catalogs/HHcat/ HHintro.html ] HH (Herbig-Haro) 46/47 the infrared source [ http://coolcosmos.ipac.caltech.edu/image_galleries/ ir_zoo/horse.html ] is lodged within a dark nebula or Bok globule - near the lower right corner of the dark nebula in the optical inset - that is largely opaque when viewed [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ multiwavelength_astronomy/multiwavelength_astronomy/ index.html ] in visible light. The energetic outflow [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/1995/24/image/a ] features extend for nearly a light-year, burrowing into the dark interstellar material, and are attributed to [ http://photojournal.jpl.nasa.gov/catalog/PIA04940 ] early stages in the life of a sun-like star. They may well represent a phase of our own Sun's evolution [ http://www.columbia.edu/~ah297/unesa/sun/ sun-chapter5.html ] which took place some 4.5 billion years ago, along with the formation of our solar system from a circumstellar disk [ http://antwrp.gsfc.nasa.gov/apod/ap030208.html ]. A tantalizing [ http://planetquest.jpl.nasa.gov/ ] object to explore with Spitzer's infrared [ http://www.spitzer.caltech.edu/science/whyir/ index.shtml ] capabilities, this young star system [ http://arxiv.org/abs/astro-ph/0304258 ] is relatively nearby, located only some 1,140 light-years distant in the nautical constellation Vela [ http://www.hawastsoc.org/deepsky/vel/index.html ]. |
|
Composite Crab
| Title |
Composite Crab |
| Explanation |
The Crab Pulsar, a city-sized, magnetized neutron star [ http://antwrp.gsfc.nasa.gov/apod/ap030201.html ] spinning 30 times a second, lies at the center of this composite image of the inner region of the well-known Crab Nebula [ http://www.seds.org/messier/m/m001.html ]. The spectacular picture combines optical data (red) from the Hubble Space Telescope [ http://hubblesite.org/gallery/ ] and x-ray images (blue) from the Chandra Observatory [ http://chandra.harvard.edu/fifth/ ], also used in the popular Crab Pulsar movies [ http://chandra.harvard.edu/photo/2002/0052/movies.html ]. Like a cosmic dynamo [ http://chandra.harvard.edu/chronicle/0201/vela.html ] the pulsar powers [ http://antwrp.gsfc.nasa.gov/apod/ap010602.html ] the x-ray and optical emission from the nebula, accelerating charged particles and producing the eerie, glowing x-ray jets. Ring-like structures are x-ray emitting regions where the high energy particles slam into the nebular material. The innermost ring is about a light-year across. With more mass than the Sun [ http://www.sunblock99.org.uk/sb99/fact/heavy.html ] and the density of an atomic nucleus [ http://hyperphysics.phy-astr.gsu.edu/hbase/ nuclear/nucuni.html#c2 ], the spinning pulsar is the collapsed core of a massive star that exploded, while the nebula is the expanding remnant of the star's outer layers. The supernova explosion was witnessed in the year 1054 [ http://www.seds.org/messier/more/m001_sn.html ]. |
|
Embedded Outflows from Herbi
…
PIA04939
Infrared Array Camera (IRAC)
| Title |
Embedded Outflows from Herbig-Haro 46/47 |
| Original Caption Released with Image |
Click on image for larger view of insert This image from NASA's Spitzer Space Telescope transforms a dark cloud into a silky translucent veil, revealing the molecular outflow from an otherwise hidden newborn star. Using near-infrared light, Spitzer pierces through the dark cloud to detect the embedded outflow in an object called HH 46/47. Herbig-Haro (HH) objects are bright, nebulous regions of gas and dust that are usually buried within dark clouds. They are formed when supersonic gas ejected from a forming protostar, or embryonic stars, interacts with the surrounding interstellar medium. These young stars are often detected only in the infrared. The Spitzer image was obtained with the infrared array camera and is a three-color mosaic. Emission at 3.6 microns is shown as blue, emission from 4.5 and 5.8 microns has been combined as green, and 8.0 micron emission is depicted as red. HH 46/47 is a striking example of a low mass protostar ejecting a jet and creating a bipolar, or two-sided, outflow. The central protostar lies inside a dark cloud (known as a 'Bok globule') which is illuminated by the nearby Gum Nebula. Located at a distance of 1,140 light-years and found in the constellation Vela, the protostar is hidden from view in the visible-light image (inset). With Spitzer, the star and its dazzling jets of molecular gas appear with clarity. The 8-micron channel of the infrared array camera is sensitive to emission from polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by the surrounding radiation field and become luminescent, accounting for the reddish cloud. Note that the boundary layer of the 8-micron emission corresponds to the lower right edge of the dark cloud in the visible-light picture. Outflows are fascinating objects, since they characterize one of the most energetic phases of the formation of low-mass stars (like our Sun). The jets arising from these protostars can reach sizes of trillions of miles and velocities of hundreds of thousands miles per hour. Outflows are clear evidence of the presence of a process that creates supersonic beams of gas. This mechanism is tightly bound to the presence of circumstellar discs which surround the young stars. Such discs are likely to contain the materials from which planetary systems form. Our Sun probably underwent a similar process some 4.5 billion years ago. Hence the interest in understanding how quickly and efficiently this mass accretion and loss process takes place in protostars. |
|
Embedded Outflows from Herbi
…
PIA04939
Infrared Array Camera (IRAC)
| Title |
Embedded Outflows from Herbig-Haro 46/47 |
| Original Caption Released with Image |
Click on image for larger view of insert This image from NASA's Spitzer Space Telescope transforms a dark cloud into a silky translucent veil, revealing the molecular outflow from an otherwise hidden newborn star. Using near-infrared light, Spitzer pierces through the dark cloud to detect the embedded outflow in an object called HH 46/47. Herbig-Haro (HH) objects are bright, nebulous regions of gas and dust that are usually buried within dark clouds. They are formed when supersonic gas ejected from a forming protostar, or embryonic stars, interacts with the surrounding interstellar medium. These young stars are often detected only in the infrared. The Spitzer image was obtained with the infrared array camera and is a three-color mosaic. Emission at 3.6 microns is shown as blue, emission from 4.5 and 5.8 microns has been combined as green, and 8.0 micron emission is depicted as red. HH 46/47 is a striking example of a low mass protostar ejecting a jet and creating a bipolar, or two-sided, outflow. The central protostar lies inside a dark cloud (known as a 'Bok globule') which is illuminated by the nearby Gum Nebula. Located at a distance of 1,140 light-years and found in the constellation Vela, the protostar is hidden from view in the visible-light image (inset). With Spitzer, the star and its dazzling jets of molecular gas appear with clarity. The 8-micron channel of the infrared array camera is sensitive to emission from polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by the surrounding radiation field and become luminescent, accounting for the reddish cloud. Note that the boundary layer of the 8-micron emission corresponds to the lower right edge of the dark cloud in the visible-light picture. Outflows are fascinating objects, since they characterize one of the most energetic phases of the formation of low-mass stars (like our Sun). The jets arising from these protostars can reach sizes of trillions of miles and velocities of hundreds of thousands miles per hour. Outflows are clear evidence of the presence of a process that creates supersonic beams of gas. This mechanism is tightly bound to the presence of circumstellar discs which surround the young stars. Such discs are likely to contain the materials from which planetary systems form. Our Sun probably underwent a similar process some 4.5 billion years ago. Hence the interest in understanding how quickly and efficiently this mass accretion and loss process takes place in protostars. |
|
Embedded Outflows from Herbi
…
PIA04939
Infrared Array Camera (IRAC)
| Title |
Embedded Outflows from Herbig-Haro 46/47 |
| Original Caption Released with Image |
Click on image for larger view of insert This image from NASA's Spitzer Space Telescope transforms a dark cloud into a silky translucent veil, revealing the molecular outflow from an otherwise hidden newborn star. Using near-infrared light, Spitzer pierces through the dark cloud to detect the embedded outflow in an object called HH 46/47. Herbig-Haro (HH) objects are bright, nebulous regions of gas and dust that are usually buried within dark clouds. They are formed when supersonic gas ejected from a forming protostar, or embryonic stars, interacts with the surrounding interstellar medium. These young stars are often detected only in the infrared. The Spitzer image was obtained with the infrared array camera and is a three-color mosaic. Emission at 3.6 microns is shown as blue, emission from 4.5 and 5.8 microns has been combined as green, and 8.0 micron emission is depicted as red. HH 46/47 is a striking example of a low mass protostar ejecting a jet and creating a bipolar, or two-sided, outflow. The central protostar lies inside a dark cloud (known as a 'Bok globule') which is illuminated by the nearby Gum Nebula. Located at a distance of 1,140 light-years and found in the constellation Vela, the protostar is hidden from view in the visible-light image (inset). With Spitzer, the star and its dazzling jets of molecular gas appear with clarity. The 8-micron channel of the infrared array camera is sensitive to emission from polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by the surrounding radiation field and become luminescent, accounting for the reddish cloud. Note that the boundary layer of the 8-micron emission corresponds to the lower right edge of the dark cloud in the visible-light picture. Outflows are fascinating objects, since they characterize one of the most energetic phases of the formation of low-mass stars (like our Sun). The jets arising from these protostars can reach sizes of trillions of miles and velocities of hundreds of thousands miles per hour. Outflows are clear evidence of the presence of a process that creates supersonic beams of gas. This mechanism is tightly bound to the presence of circumstellar discs which surround the young stars. Such discs are likely to contain the materials from which planetary systems form. Our Sun probably underwent a similar process some 4.5 billion years ago. Hence the interest in understanding how quickly and efficiently this mass accretion and loss process takes place in protostars. |
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