The Spitzer Space Telescope

Launched on August 25, 2003, and operating in the infra-red part of the spectrum, the Spitzer Space Telescope is the fourth of NASA's Great Observatories, a program that also includes the Hubble Space Telescope, the Chandra X-ray Observatory and the Compton Gamma Ray Observatory.  Spitzer is also part of NASA's Origins Program, which seeks to answer the questions: Where did we come from and are we alone?  The images below are a selection of the treasures being sent back by this new telescope, allowing us to see them clearly in infra-red.

Additional information about the Spitzer Space Telescope is available at http://www.spitzer.caltech.edu

Omega Centauri

Millions of stars glisten like an iridescent opal in this image from NASA's Spitzer Space Telescope.  Called Omega Centauri, this sparkling orb of stars is the biggest and brightest of more than 150 globular clusters that orbit around the outside of our Milky Way galaxy.  The object is visible in the constellation Centaurus with the naked eye to observers at southern latitudes.

Globular clusters are some of the oldest objects in our universe. Their stars are more than 12 billion years old, and, in most cases, formed all at once when the universe was very young.  Omega Centauri is unusual in that its stars are of different ages and possess varying levels of metals, or elements heavier than boron.  Astronomers say this points to a different origin for Omega Centauri than other globular clusters.  They think it might be the core of a dwarf galaxy that was ripped apart and absorbed by our Milky Way long ago.

In this new picture of Omega Centauri the red and yellow-coloured dots represent the stars revealed by Spitzer.  These are the more evolved, larger, dustier red giant stars.  The stars coloured blue are less evolved, like our own sun, and were captured by both Spitzer's infrared eyes and in visible light by the National Science Foundation's Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile .  Some of the red spots in the picture are distant galaxies beyond our own.  There is a higher resolution image (0.8Mb) here.

The Rho Ophiuchi Dark Cloud

Newborn stars peek out from beneath their natal blanket of dust in this dynamic image of the Rho Ophiuchi dark cloud.  This area is one of the closest star-forming regions to our own solar system, located near the constellations Scorpius and Ophiuchus and about 407 light years from Earth.

The area comprises a large main cloud of molecular hydrogen, a key molecule allowing new stars to form out of cold cosmic gas, with two long streamers trailing off in different directions.  Recent studies using the latest X-ray and infrared observations reveal more than 300 young stellar objects within the large central cloud. Their median age is only 300,000 years, very young compared to some of the universe's oldest stars, which are more than 12 billion years old.  

The youngest stars are surrounded by dusty disks of gas from which they and their potential planetary systems are forming.  These young disk systems show up as red in this image. Some of these young stellar objects are surrounded by their own compact nebulae. More evolved stars, which have shed their natal material, are blue.  The extended white nebula in the centre right of the image is a region of the cloud glowing in infrared light due to the heating of dust by bright young stars near the cloud's right edge.  There is a Higher Resolution Image (3Mb) here.

The Coronet Cluster

While perhaps not quite as well known as the star forming region in Orion, the Corona Australis region (containing, at its heart, the Coronet cluster) is one of the nearest and most active regions of ongoing star formation.  At only about 420 light-years away, the Coronet is over three times closer than the Orion nebula is to Earth.  It contains a loose cluster of a few dozen young stars with a wide range of masses and at various stages of evolution, giving astronomers an opportunity to observe embryonic stars simultaneously in several wavelengths.

This composite image shows the Coronet in X-rays from Chandra (purple) and infrared from Spitzer (orange, green, and cyan). The Spitzer data show young stars plus diffuse emission from dust. Due to the host of young stars in different life stages in the Coronet, astronomers can use these data to pinpoint details of how the youngest stars evolve.

The Helix Nebula (NG7293)

The nebula, located about 700 light-years away in the constellation Aquarius, is a planetary nebula which we have imaged.  They are the remains of stars that once looked a lot like our sun. When sun-like stars die, they puff out their outer gaseous layers and these layers are heated by the hot core of the dead star, called a white dwarf.  They then shine with infrared and visible colours.  Our own sun will blossom into a planetary nebula when it dies in about five billion years.  In Spitzer's infrared view the white dwarf is visible as a tiny white dot in the center of the picture. The red colour in the middle of the eye denotes the final layers of gas blown out when the star died.  The brighter red circle in the very center is the glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved). This dust, discovered by Spitzer's infrared heat-seeking vision, was most likely kicked up by comets that survived the death of their star.  Before the star died, its comets and possibly planets would have orbited the star in an orderly fashion, but when the star blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, resulting in an ongoing cosmic dust storm.  Any inner planets in the system would have burned up or been swallowed as their dying star expanded.  There is a full resolution image (6.2Mb) here.  So far, the Helix nebula is one of only a few dead-star systems in which evidence for comet survivors has been found.

And this is a newly expanded image of the Helix nebula, released for the fourth anniversary of the launch of the telescope.  Spitzer has mapped the expansive outer structure of the six-light-year-wide nebula, and probed the inner region around the central dead star to reveal what appears to be a planetary system that survived the star's chaotic death throes.  There is a higher resolution image (1.4Mb) here.

Messier 42

Images from the Spitzer and Hubble Space Telescopes have been combined to expose the chaos that baby stars are creating 1,500 light-years away in the cosmic cloud we know as the Orion Nebula (M42).  This infrared and visible-light composite indicates that four monstrously massive stars at the centre of the cloud may be the main culprits in the familiar Orion constellation.  The stars are collectively known as the "Trapezium" and the area they inhabit can be identified as the yellow smudge near the centre of the image.

Swirls of green in Hubble's ultraviolet and visible-light view reveal hydrogen and sulphur gas that have been heated and ionized by intense ultraviolet radiation from the Trapezium's stars.  Meanwhile, Spitzer's infrared view exposes carbon-rich molecules called polycyclic aromatic hydrocarbons in the cloud.  These organic molecules have been illuminated by the Trapezium's stars, and are shown in the composite as wisps of red and orange.  On Earth, polycyclic aromatic hydrocarbons are found on burnt toast and in car exhausts.  Orange-yellow dots revealed by Spitzer are actually infant stars deeply embedded in a cocoon of dust and gas.  Hubble showed less embedded stars as specks of green, and foreground stars as blue spots.

Stellar winds from clusters of newborn stars scattered throughout the cloud etched all of the well-defined ridges and cavities in Orion.  The large cavity near the right of the image was probably carved by winds from the Trapezium's stars.  Located 1,500 light-years away from Earth, the Orion Nebula is the brightest spot in the sword of the Orion, or the "Hunter" constellation.  The cosmic cloud is also our closest massive star-formation factory, and astronomers believe it contains more than 1,000 young stars.  The Orion constellation is a familiar sight in the autumn and winter night sky in the northern hemisphere.  The nebula is invisible to the unaided eye, but can be resolved with binoculars or small telescopes.  There is a full resolution image (2.6Mb) here.

And this infrared image from Spitzer was taken after Spitzer ran out of its coolant in May 2009, beginning its extended "warm" mission.  The coolant was needed to chill the instruments, but the two shortest-wavelength infrared channels still work normally at the new, warmer temperature of 30 Kelvin (minus 406 Fahrenheit).  In this new phase of the mission, Spitzer is able to spend more time on projects that cover a lot of sky and require longer observation times.  One such project is the "Young Stellar Object Variability" program, in which Spitzer looks repeatedly at the same patch of the Orion nebula, monitoring the same set of about 1,500 variable stars over time.  It has already taken about 80 pictures of the region over 40 days.  A second set of observations will be made in autumn 2010.  The region's stars are about one million years old, compared to our Sun which is 4.6 billion years old.

Young stars are fickle, with brightness levels that change more than those of adult, sun-like stars.  They also spin around faster.  One reason for the variations in brightness is the existence of cold spots on their surfaces.  Cold spots are the opposite of "age spots" - the younger the star, the more it has.  The cold spots come and go as a star whips around, changing the amount of light that reaches our telescopes.  Stellar brightness can also change due to hot spots, which are caused by gas accreting onto a young star from the material out of which it formed.  There is a Full Resolution Image (2.5Mb) here.

The Larger Magellanic Cloud

This mosaic of 300,000 individual tiles, offers astronomers a unique chance to study the lifecycle of stars and dust in a single galaxy. Nearly one million objects are revealed for the first time in this Spitzer view, which represents about a 1,000-fold improvement in sensitivity over previous space-based missions.  Most of the new objects are dusty stars of various ages populating the Large Magellanic Cloud; the rest are thought to be background galaxies.  The blue colour in the picture, seen most prominently in the central bar, represents starlight from older stars.  The chaotic, bright regions outside this bar are filled with hot, massive stars buried in thick blankets of dust. The red colour around these bright regions is from dust heated by stars, while the red dots scattered throughout the picture are either dusty, old stars or more distant galaxies. The greenish clouds contain cooler interstellar gas and molecular-sized dust grains illuminated by ambient starlight.  Astronomers say this image allows them to quantify the process by which space dust -- the same stuff that makes up planets and even people -- is recycled in a galaxy. The picture shows dust around the young stars, where it is being consumed (red-tinted, bright clouds); scattered about in the space between stars (greenish clouds); and in expelled shells of material from old stars (randomly-spaced red dots).

The Large Magellanic Cloud, located 160,000 light-years from Earth, is one of a handful of dwarf galaxies that orbit our own Milky Way. It is approximately one-third as wide as the Milky Way, and, if it could be seen in its entirety, would cover the same amount of sky as a grid of about 480 full moons.  About one-third of the entire galaxy can be seen in the Spitzer image.  There is a Full resolution image (6Mb) here

NGC 2207 and IC 2163

This combined Spitzer and Hubble image shows two interacting galaxies which have taken on the form of a giant mask.  The icy blue eyes are actually the cores of two merging galaxies, called NGC 2207 and IC 2163, and the mask is their spiral arms.  The false-coloured image consists of infrared data from NASA's Spitzer Space Telescope (red) and visible data from NASA's Hubble Space Telescope (blue/green).

NGC 2207 and IC 2163 met and began a sort of gravitational tango about 40 million years ago.  The two galaxies are tugging at each other, stimulating new stars to form.  Eventually, this cosmic ball will come to an end, when the galaxies meld into one.  The dancing duo is located 140 million light-years away in the Canis Major constellation.  The infrared data from Spitzer highlight the galaxies' dusty regions, while the visible data from Hubble indicates starlight. In the Hubble-only image (not pictured here), the dusty regions appear as dark lanes.  The Hubble data correspond to light with wavelengths of .44 and .55 microns (blue and green, respectively). The Spitzer data represent light of 8 microns.  There is full resolution image (4.5Mb) here.

Messier 82

This image composite compares a visible-light view (left) of the "Cigar galaxy" to an infrared view from NASA's Spitzer Space Telescope of the same galaxy.  While the visible image shows a serene galaxy looking cool as a cucumber, the infrared image reveals a smoking hot "cigar."  The visible-light image shows only a bar of light against a dark patch of space.  Longer exposures of the galaxy (not pictured here) have revealed cone-shaped clouds of hot gas above and below the galaxy's plane.  It took Spitzer's three sensitive instruments to show that the galaxy is also surrounded by a huge, hidden halo of smoky dust (red in infrared image).

The infrared image above was taken by Spitzer's infrared array camera. The dust particles (red) are being blown out into space by the galaxy's hot stars (blue).  Spitzer's infrared spectrograph showed the dust contains polycyclic aromatic hydrocarbons. This smelly molecule can be found on Earth in tailpipes, barbecue pits and other places where combustion reactions have occurred.

Messier 82 is located about 12 million light-years away in the constellation of Ursa Major.  It is viewed edge on, and so appears as a thin, cigar-shaped bar.  The galaxy is termed a 'starburst' because its core is a fiery hotbed of stellar birth.  The larger nearby galaxy, Messier 81, is gravitationally interacting with Messier 82, prodding it into producing the new stars.

The infrared picture was taken as a part of the Spitzer Infrared Nearby Galaxy Survey.  Blue indicates infrared light of 3.6 microns, green corresponds to 4.5 microns, and red to 5.8 and 8.0 microns.  The contribution from starlight (measured at 3.6 microns) has been subtracted from the 5.8- and 8-micron images to enhance the visibility of the dust features.  The visible-light picture is from the National Optical Astronomy Observatory, Tucson, Ariz.  There is a full resolution image here (3.8MB)

Stefan's Quintet

This false-colour composite image of the Stephan's Quintet galaxy cluster clearly shows one of the largest shock waves ever seen (green arc), produced by one galaxy falling toward another at over a million miles per hour.  It is made up of data from NASA's Spitzer Space Telescope and a ground-based telescope in Spain.  Four of the five galaxies in this image are involved in a violent collision, which has already stripped most of the hydrogen gas from the interiors of the galaxies. The centres of the galaxies appear as bright yellow-pink knots inside a blue haze of stars, and the galaxy producing all the turmoil, NGC7318b, is the left of two small bright regions in the middle right of the image.  One galaxy, the large spiral at the bottom left of the image, is a foreground object and is not associated with the cluster.

The titanic shock wave, larger than our own Milky Way galaxy, was detected by the ground-based telescope using visible-light wavelengths.  It consists of hot hydrogen gas.  As NGC7318b collides with gas spread throughout the cluster, atoms of hydrogen are heated in the shock wave, producing the green glow.  Spitzer pointed its infrared spectrograph at the peak of this shock wave (middle of green glow) to learn more about its inner workings.  The Spitzer spectrum showed a strong infrared signature for incredibly turbulent gas made up of hydrogen molecules.  This gas is caused when atoms of hydrogen rapidly pair-up to form molecules in the wake of the shock wave.  Molecular hydrogen, unlike atomic hydrogen, gives off most of its energy through vibrations that emit in the infrared.  This highly disturbed gas is the most turbulent molecular hydrogen ever seen.  Astronomers were surprised not only by the turbulence of the gas, but by the incredible strength of the emission.  The reason the molecular hydrogen emission is so powerful is not yet completely understood.

Stephan's Quintet is located 300 million light-years away in the constellation of Pegasus.  This image is composed of three data sets: visible red light (blue) and H-alpha (green) from the Calar Alto Observatory in Spain, operated by the Max Planck Institute in Germany; and 8-micron infrared light (red) from Spitzer's infrared array camera.  There is a full resolution image here (2.0MB)

Herbig-Haro Object 49/50

This "tornado," designated Herbig-Haro 49/50, is shaped by a cosmic jet packing a powerful punch as it ploughs through clouds of interstellar gas and dust.  The tornado-like feature is actually a shock front created by a jet of material flowing downward through the field of view.  A still-forming star located off the upper edge of the image generates this outflow. The jet slams into neighbouring dust clouds at a speed of more than 100 miles per second, heating the dust to incandescence and causing it to glow with infrared light detectable by Spitzer.  The triangular shape results from the wake created by the jet's motion, similar to the wake behind a speeding boat.

Scientists can only speculate about the source of the spiral appearance.  Magnetic fields throughout the region might have shaped the object.  Alternatively, the shock might have developed instabilities as it ploughed into surrounding material, creating eddies that give the "tornado" its distinctive appearance.  Astronomers believe that the blue colour at the tornado's tip results from high molecular excitation at the head of the shock.  Those high excitation levels generate more short-wavelength emission, shown as blue in this colour-coded image. Molecular excitation levels decrease away from the head of the bow shock; therefore the emission is at longer wavelengths, coloured red here.  The star at the tip of the tornado, which appears to be surrounded by a faint halo, might be a chance superposition along our line of sight.  However, the star instead might be physically associated with the tornado, in which case, the halo likely is due to the outflow running into circum-stellar material.

HH 49/50 is located in the Chameleon I star-forming complex, a region containing more than 100 young stars. Most of the new stars are smaller than the sun, although some are more massive.  Visible-light observations have found a number of outflows in the region, however most of those outflows have no infrared counterpart.  There is a full resolution image here (1.5MB)

Milky Way Galaxy Centre

In this false-colour picture, old and cool stars are blue, while dust features lit up by blazing hot, massive stars are shown in a reddish hue. Both bright and dark filamentary clouds can be seen, many of which harbour stellar nurseries. The plane of the Milky Way's flat disk is apparent as the main, horizontal band of clouds. The brightest white spot in the middle is the very center of the galaxy, which also marks the site of a super-massive black hole.  The region pictured here is immense, with a horizontal span of 890 light-years and a vertical span of 640 light-years. Earth is located 26,000 light-years away, out in one of the Milky Way's spiral arms. Though most of the objects seen in this image are located at the galactic centre, the features above and below the galactic plane tend to lie closer to Earth

This image is a mosaic of thousands of short exposures taken by Spitzer's Infrared Array Camera (IRAC), showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange), and 8.0 microns (red). The entire region was imaged in less than 16 hours.  Click here for a FULL RESOLUTION IMAGE (4MB)

Reflection Nebula NGC 1333 in Perseus

Located 1,000 light-years from Earth in the constellation Perseus, a reflection nebula called NGC 1333 epitomizes the beautiful chaos of a dense group of stars being born.  Most of the visible light from the young stars in this region is obscured by the dense, dusty cloud in which they formed.  With the Spitzer Space Telescope, scientists can detect the infrared light from these objects which allows a look through the dust to gain a more detailed understanding of how stars like our sun begin their lives.  The young stars in NGC 1333 do not form a single cluster, but are split between two sub-groups.  One group is to the north near the nebula shown as red in the image. The other group is south, where the features shown in yellow and green abound in the densest part of the gas cloud.

The knotty yellow-green features located in the lower portion of the image are glowing shock fronts where jets of material, spewed from extremely young embryonic stars, are ploughing into the cold, dense gas nearby. The sheer number of separate jets that appear in this region is unprecedented. This leads scientists to believe that by stirring up the cold gas, the jets may contribute to the eventual dispersal of the gas cloud, preventing more stars from forming in NGC 1333.  Click here for a FULL RESOLUTION IMAGE (4.0Mb)

W5 Star Forming Region in Cassiopeia

This image shows the "mountains" where stars are born.  Dubbed "Mountains of Creation" by Spitzer scientists, these towering pillars of cool gas and dust are illuminated at their tips with light from warm, embryonic stars.  This infrared picture is reminiscent of Hubble's iconic visible-light image of the Eagle Nebula (inset), which also features a star-forming region, or nebula, that is being sculpted into pillars by radiation and winds from hot, massive stars. The pillars in the Spitzer image are part of a region called W5, in the Cassiopeia constellation 7,000 light-years away and 50 light-years across. They are more than 10 times in the size of those in the Eagle Nebula (shown to scale here).  The Spitzer's view differs from Hubble's because infrared light penetrates dust, whereas visible light is blocked by it. In the Spitzer image, hundreds of forming stars (white/yellow) can seen for the first time inside the central pillar, and dozens inside the tall pillar to the left. Scientists believe these star clusters were triggered into existence by radiation and winds from an "initiator" star more than 10 times the mass of our Sun. This star is not pictured, but the finger-like pillars "point" toward its location above the image frame.

The Spitzer picture also reveals stars (blue) a bit older than the ones in the pillar tips in the evacuated areas between the clouds. Scientists believe these stars were born around the same time as the massive initiator star not pictured. A third group of young stars occupies the bright area below the central pillar. It is not known whether these stars formed in a related or separate event. Some of the blue dots are foreground stars that are not members of this nebula.  The red colour in the Spitzer image represents organic molecules known as polycyclic aromatic hydrocarbons. These building blocks of life are often found in star-forming clouds of gas and dust. Like small dust grains, they are heated by the light from the young stars, then emit energy in infrared wavelengths.  
Click here for a FULL RESOLUTION IMAGE (4.0Mb)

Messier 31

This 24-micron mosaic (top panel) is the sharpest image ever taken of the dust in another spiral galaxy. This is possible because Andromeda is a close neighbour to the Milky Way at a mere 2.5 million light-years away.  The Spitzer multiband imaging photometer's 24-micron detector recorded 11,000 separate snapshots to create this new comprehensive picture.  Asymmetrical features are seen in the prominent ring of star formation.  The ring appears to be split into two pieces, forming the hole to the lower right. These features may have been caused by interactions with satellite galaxies around Andromeda as they plunge through its disk.  The image also reveals delicate tracings of spiral arms within this ring that reach into the very centre of the galaxy.  One sees a scattering of stars within Andromeda, but only select stars that are wrapped in envelopes of dust light up at infrared wavelengths.  This is in dramatic contrast to the traditional view at visible wavelengths (lower left panel), which shows the starlight instead of the dust.  The centre of the galaxy in this view is dominated by a large bulge that overwhelms the inner spirals seen in dust. The dust lanes are faintly visible in places, but only where they can be seen in silhouette against background stars.

The multi-wavelength view of Andromeda (lower right panel) combines images taken at 24 microns (blue), 70 microns (green), and 160 microns (red). Using all three bands from the multiband imaging photometer allows astronomers to measure the temperature of the dust by its colour. The warmest dust is brightest at 24 microns while the coolest is most evident at 160 microns.  The blue/white areas have the hottest dust, as seen in the bulge and in the star-forming areas along the arms. The cooler dust floating further out in the ring and arms are in the redder regions.   The data were taken on August 25, 2004, the one-year anniversary of the launch of the space telescope.  Click here for a FULL RESOLUTION IMAGE (4.0Mb)

Messier 51

The image on the right below shows the "Whirlpool Galaxy" revealing strange structures bridging the gaps between the dust-rich spiral arms, and tracing the dust, gas and stellar populations in both the bright spiral galaxy and its companion.  The image is a four-color composite of invisible light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8.0 microns (red). These wavelengths are roughly 10 times longer than those seen by the human eye.

The visible light image to the left comes from the Kitt Peak National Observatory 2.1m telescope, and has the same orientation and size as the Spitzer infrared image, measuring 9.9 by 13.7 arcminutes (north up). Also a four-color composite, the visible light image shows emissions from 0.4 to 0.7 microns, including the H-alpha nebular feature (red in the image).

The light seen in the images originates from very different sources. At shorter wavelengths (in the visible bands, and in the infrared from 3.6 to 4.5 microns), the light comes mainly from stars. This starlight fades at longer wavelengths (5.8 to 8.0 microns), where we see the glow from clouds of interstellar dust. This dust consists mainly of a variety of carbon-based organic molecules known collectively as polycyclic aromatic hydrocarbons. Wherever these compounds are found, there will also be dust granules and gas, which provide a reservoir of raw materials for future star formation.

Particularly puzzling are the large number of thin filaments of red emission seen in the infrared data between the arms of the large spiral galaxy. In contrast to the beady nature of the dust emission seen in the arms themselves, these spoke-like features are thin and regular, and prevalent in the gaps all over the face of the galaxy.

Also of interest is the contrast in the distributions of dust and stars between the spiral and its faint companion. While the spiral is rich in dust, bright in the longer infrared wavebands, and actively forming new stars, its blue companion shows little infrared emission and hosts an older stellar population. The spectacular whirlpool structure and star formation in M51 are thought to be triggered by an ongoing collision with its companion. Understanding the impact on star formation by the interaction of galaxies is one of the goals of these observations.

The Whirlpool galaxy is a favourite target for amateur and professional astronomers, alike, and was the first light target for the Infrared Space Observatory. Found in the constellation Canes Venatici, M51 is 37 million light-years away.  Click here for a FULL RESOLUTION IMAGE (3.5Mb)

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