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Herschel telescope reveals invisible cosmos

HERSHEL, A CUTTING-EDGE SPACE OBSERVATORY, carries the largest, most powerful infrared telescope ever launched.

A pioneering mission of the European Space Agency, it is studying the origin and evolution of stars and galaxies to help understand how the Universe came to be the way it is today.

For this purpose Herschel is looking, at far-infrared and submillimetre wavelengths, at objects that are among the coldest in space.

Launched in May 2009 it has already given great results to the scientific community by revealing invisible parts of the universe.

More information:

ESA Herschel mission

Adapted from information issued by ESA.

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Journey to the Centre of the Galaxy

HIDING BEHIND DUST in the direction of the constellations Sagittarius and Scorpius is the centre of our own Milky Way galaxy, over 25,000 light years away. The infrared vision of NASA’s Spitzer Space Telescope and the European Space Agency’s Herschel Space Observatory sees through the dust showing us this strange and tumultuous region.

Adapted from information issued by NASA / JPL-Caltech / ESA.

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Hidden star groups uncovered

Star clusters discovered using VISTA

Using data from the VISTA infrared survey telescope, astronomers have discovered 96 new 'open' star clusters hidden behind dust in the Milky Way, 30 of which are shown in this mosaic.

  • Almost 100 star clusters found hiding behind dust in the Milky Way
  • Uncovered using the dust-penetrating power of infrared
  • There could be 30,000 more clusters still waiting to be found

NINETY-SIX PREVIOUSLY UNKNOWN ‘open star clusters’ have been found hiding behind dust in the Milky Way.

These tiny and faint groupings were invisible to previous surveys, but they could not escape the sensitive infrared detectors VISTA—an infrared survey telescope at the European Southern Observatory’s (ESO) Paranal Observatory in Chile—which can peer through the dust.

This result comes just one year after the start of the VISTA Variables in the Via Lactea programme (VVV), one of the six surveys running on the new telescope. (‘Via Lactea’ is the Latin name for the Milky Way.)

Invisible to most telescopes

Most stars that weigh more than half as much as our Sun form in groups, called open star clusters. These clusters are the building blocks of galaxies and vital for the formation and evolution of galaxies such as our own.

However, stellar clusters form in very dusty regions that absorb most of the visible light that the young stars emit, making them invisible to most telescopes, but not to VISTA.

In order to spot the youngest star clusters, the astronomers concentrated their search towards known star-forming areas. They found that regions that looked empty in previous visible-light surveys, actually held lots of clusters.

VISTA telescope

VISTA is an infrared survey telescope at the European Southern Observatory in Chile.

No wonder they were hidden

By using carefully tuned computer software, the team was able to remove the foreground stars appearing in front of each cluster in order to count the genuine cluster members.

Afterwards, they made visual inspections of the images to measure the cluster sizes, and for the more populous clusters they made other measurements such as distance, and the age of the stars.

“We found that … the dust in front of these clusters makes them appear 10,000 to 100 million times fainter in visible light,” explains Radostin Kurtev, another member of the team. “It’s no wonder they were hidden.”

Tip of the iceberg

Only 2,500 open clusters are known so far in the Milky Way, but astronomers think there might be as many as 30,000 still hiding behind the dust and gas.

These new 96 open clusters might be only the tip of the iceberg.

“We’ve just started to use more sophisticated automatic software to search for less concentrated and older clusters,” adds Jura Borissova, lead author of the study. “I am confident that many more are coming soon.”

Adapted from information issued by ESO. Images courtesy ESO / J. Borissova / Steven Beard (UKATC).

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Celestial treasure trove

WISE image of the Andromeda galaxy

WISE's infrared view of the Andromeda galaxy ignores most of the stars, and instead brings out detail in dust clouds heated by the energy of stars.

  • WISE space telescope studied the cosmos at infrared wavelengths
  • It took 2.7 million images during its mission
  • Huge archive of images and data has now been released

ASTRONOMERS ARE SIFTING through hundreds of millions of galaxies, stars and asteroids collected in the first bundle of data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission.

WISE launched into space on December 14, 2009, on a mission to map the entire sky in infrared light with greatly improved sensitivity and resolution over its predecessors.

From its orbit, it scanned the skies about one-and-a-half times while collecting images taken at four infrared wavelengths of light. It took more than 2.7 million images over the course of its mission, capturing objects ranging from faraway galaxies to asteroids relatively close to Earth.

Like other infrared telescopes, WISE required coolant to chill its heat-sensitive detectors. When this frozen hydrogen coolant ran out, as expected, in early October, 2010, two of its four infrared channels were still operational.

The survey was then extended for four more months, with the goal of finishing its sweep for asteroids and comets in the main asteroid belt of our Solar System.

The satellite went into hibernation in early February of this year.

WISE image of IC 342

Spiral galaxy IC 342 is normally hard to see through the stars of the Milky Way, but WISE's infrared eyes can see it spectacular detail.

WISE image Rho Ophiuchi

The Rho Ophiuchi cloud complex is one of the nearest star-forming regions to Earth. WISE's infrared capabilities enable astronomers to see normally hidden details.

The mission’s nearby discoveries included 20 comets, more than 33,000 asteroids between Mars and Jupiter, and 133 near-Earth objects, which are those asteroids and comets with orbits that come close to Earth’s path around the Sun.

Data from the first 57 percent of the sky surveyed is now accessible through an online public archive. The complete survey, with improved data processing, will be made available in the spring of 2012.

A predecessor to WISE, the Infrared Astronomical Satellite, served a similar role about 25 years ago, and those data are still valuable to astronomers today. Likewise, the WISE legacy is expected to endure for decades.

Astronomers will use WISE’s infrared data to hunt for hidden oddities, and to study trends in large populations of known objects. Survey missions often result in the unexpected discoveries too, because they are looking everywhere in the sky rather than at known targets.

The whole collection can be seen at: http://wise.ssl.berkeley.edu/gallery_images.html

Adapted from information issued by JPL.

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Star spangled nebula

Spitzer image of the North American Nebula

This new Spitzer Space Telescope infrared image of the North American Nebula reveals a multitude of young stars, ordinarily hidden in visible wavelength images by veils of dust.

  • Nebula shaped like the North American continent
  • Infrared view pierces the veil of dust, revealing stars
  • Thousands of young stars seen in Spitzer telescope image

STARS AT ALL STAGES of development, from dusty little tots to young adults, are on display in a new image from NASA’s Spitzer Space Telescope.

This cosmic community is called the North American Nebula. At visible light wavelength pictures, the region resembles the North American continent, with the most striking resemblance being the Gulf of Mexico.

But in Spitzer’s infrared view, the continent disappears. Instead, a swirling landscape of dust and young stars comes into view.

“One of the things that makes me so excited about this image is how different it is from the visible image, and how much more we can see in the infrared than in the visible,” said Luisa Rebull of NASA’s Spitzer Science Centre at the California Institute of Technology.

Rebull is lead author of a paper about the observations, accepted for publication in the Astrophysical Journal Supplement Series.

“The Spitzer image reveals a wealth of detail about the dust and the young stars here.”

Dusty environment

Rebull and her team have identified more than 2,000 new, candidate young stars in the region. There were only about 200 known before.

Because young stars grow up surrounded by blankets of dust, they are hidden in visible-light images. Spitzer’s infrared detectors pick up the glow of the dusty, buried stars.

Visible and infrared views of the North American Nebula

Spot the difference. Visible light (left) and infrared wavelength (right) views of the North American Nebula, taken by the Digitised Sky Survey and NASA's Spitzer Space Telescope, respectively. Infrared can see through the dust and gas.

A star is born inside a collapsing ball of gas and dust. As the material collapses inward, it flattens out into a disc that spins around together with the forming star like a spinning top. Jets of gas shoot perpendicularly away from the disc, above and below it.

As the star ages, planets are thought to form out of the disc—material clumps together, ultimately growing into mature planets. Eventually, most of the dust dissipates, aside from a tenuous ring similar to the one in our Solar System, referred to as Zodiacal dust.

Family portrait

The new Spitzer image reveals all the stages of a star’s young life, from the early years when it is swaddled in dust to early adulthood, when it has become a young parent to a family of developing planets. Sprightly “toddler” stars with jets can also be identified in Spitzer’s view.

“This is a really busy area to image, with stars everywhere, from the North American complex itself, as well as in front of and behind the region,” said Rebull.

Young stars in the "Gulf of Mexico" part of the North American Nebula

A cluster of young stars in the "Gulf of Mexico," part of the North American Nebula.

“We refer to the stars that are not associated with the region as contamination,” Rebull added. “With Spitzer, we can easily sort this contamination out and clearly distinguish between the young stars in the complex and the older ones that are unrelated.”

See the full-size image here.

More mysteries to solve

The North American Nebula still has a mystery surrounding it, involving its power source. Nobody has been able to identify the group of massive stars that is thought to be dominating and illuminating the nebula.

The Spitzer image, like images from other telescopes, hints that the missing stars are lurking behind the Gulf of Mexico portion of the nebula. This is evident from the illumination pattern of the nebula, especially when viewed with the detector on Spitzer that picks up 24-micron infrared light. That light appears to be coming from behind the Gulf of Mexico’s dark tangle of clouds, in the same way that sunlight creeps out from behind a rain cloud.

The nebula’s distance from Earth is also a mystery. Current estimates put it at about 1,800 light-years from Earth.

Adapted from information issued by NASA / JPL-Caltech. Images courtesy NASA / JPL-Caltech / L. Rebull (SSC / Caltech).

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Birth and death in Andromeda

M31 Andromeda galaxy

The Andromeda Galaxy, seen at several wavelengths to reveal different stages of the stellar life cycle. Infrared shows reservoirs of gas in which stars are forming. Optical shows adult stars. X-rays show the violent endpoints of stellar evolution, in which individual stars explode or pairs of stars pull each other to pieces.

  • Andromeda Galaxy is the nearest large spiral galaxy
  • Contains a strange dust ring 75,000 light-years wide
  • Infrared and X-ray views show stars forming and dying

TWO SPACE TELESCOPES have combined forces to show the Andromeda Galaxy in a new light.

Using data from the European Space Agency’s (ESA) Herschel and XMM-Newton telescopes, the image shows the light of newborn stars and X-ray emission from dying stars.

Andromeda, also known as M31, is the nearest large spiral galaxy and is similar to our own Milky Way. Both contain several hundred billion stars.

Herschel was used to produce the most detailed far-infrared image of Andromeda ever taken, showing clearly that more stars are being added to the galaxy.

Sensitive to far-infrared light, Herschel sees the clouds of cool dust and gas where stars can form. Inside these clouds are many dusty cocoons containing still-forming stars, each one pulling itself together in a slow gravitational process that can last for hundreds of millions of years.

Once a star reaches a high enough density, it will begin to shine at optical wavelengths, whereupon it will become visible to normal telescopes.

Andromeda is interesting because it shows a large ring of dust about 75,000 light-years wide encircling the centre of the galaxy. Some astronomers speculate that this ring might be a “scar” that formed after a recent collision with another galaxy.

Herschel space telescope

Artist's impression of the Herschel space telescope

The new Herschel image reveals yet more intricate details, with at least five concentric rings of star-forming dust apparent.

X-rays of stellar corpses

Superimposed on the infrared image is an X-ray view taken almost simultaneously by XMM-Newton. Whereas infrared shows the beginnings of star formation, X-rays usually show the endpoints of stellar evolution.

XMM-Newton highlights hundreds of X-ray sources within Andromeda, many of them clustered around the centre, where stars are more crowded together.

Some of the X-ray sources reveal shockwaves rolling through space from exploded stars. Others indicate pairs of stars locked in a gravitational fight to the death.

In the latter case, one star has already died and is pulling gas from its still-living companion. As the gas falls through space, it heats up and gives off X-rays.

The living star will eventually be greatly depleted, having had much of its mass torn from it by the stronger gravity of its denser partner. As the stellar corpse wraps itself in this stolen gas, it could explode.

Both the infrared and X-ray images show information that is impossible to collect from the ground because these wavelengths are absorbed by Earth’s atmosphere.

Adapted from information issued by ESA. Image credits: Infrared, ESA / Herschel / PACS / SPIRE /J. Fritz, U. Gent; X-rays, ESA / XMM-Newton / EPIC / W. Pietsch, MPE; optical, R. Gendler.

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Spiral galaxy M83

Image of the nearby galaxy Messier 83

This image of the nearby galaxy Messier 83 was taken in the infrared part of the spectrum with the HAWK-I instrument on ESO’s Very Large Telescope, revealing vast numbers of stars within the galaxy.

  • 15 million light-years away
  • 40 percent the size of the Milky Way
  • Home to 6 recently spotted exploding stars

The European Southern Observatory (ESO) has released a beautiful image of the nearby galaxy Messier 83 taken by the HAWK-I instrument on ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile.

The picture shows the galaxy in infrared light and demonstrates the impressive power of the camera to create one of the sharpest and most detailed pictures of Messier 83 ever taken from the ground.

Messier 83 is about 15 million light-years away. It is over 40,000 light-years wide, only 40 percent the size of the Milky Way, but in many ways is quite similar to our home galaxy, both in its spiral shape and the presence of a bar of stars across its centre.

The galaxy is famous among astronomers for its many supernovae: vast explosions that end the lives of some stars. Over the last century, six supernovae have been spotted in Messier 83 — a record number that is matched by only one other galaxy.

Comparison of the view of the galaxy Messier 83 in infrared and visible light.

Comparison of the view of the galaxy Messier 83 at infrared light wavelengths (left) and at visible light wavelengths (right). In the infrared, the dust that obscures many stars becomes nearly transparent, making the spiral arms seem less dramatic, but revealing a whole host of new stars that are otherwise invisible.

Even without supernovae, Messier 83 is one of the brightest nearby galaxies, visible using just binoculars.

When viewed in infrared light by HAWK-I, most of the obscuring dust that hides much of Messier 83 becomes transparent. The brightly lit gas around hot young stars in the spiral arms is also less prominent in infrared pictures. As a result much more of the structure of the galaxy and the vast hordes of its constituent stars can be seen.

This clear view is important for astronomers looking for clusters of young stars, especially those hidden in dusty regions of the galaxy. Studying such star clusters was one of the main scientific goals of these observations. The acute vision of HAWK-I reveals far more stars within the galaxy.

Adapted from information issued by ESO / M. Gieles / Mischa Schirmer.