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First WISE Images - 26th February 2010

First WISE Images icon

The first images from NASA's Wide-field Infrared Survey Explorer (WISE) probe have been released. The striking images, taken in infrared light, include Andromeda, a stellar nursery  NGC 3603 within the Milky Way and a comet in our own solar system. WISE was launched on 14 December 2009 and returned its first image to Earth in early January 2010.

The mission will last until October 2010 when its coolant supply runs out. The probe requires a solid hydrogen coolant to maintain a temperature of 17 degrees Kelvin (-256 Celsius). If the instrument was warmer it would emit it's own infrared and blind itself. It will image nearly the entire sky, taking images in four wavelength bands. Just over a month into its operation, WISE has already imaged two previously undiscovered objects: a near-Earth asteroid and a comet. Many more previously undetected asteroids and comets are predicted to be found. Observations of these objects are vital for understanding the formation of the solar system.

In addition to its detection of many near-Earth objects and asteroids, cool stars known as brown dwarfs are also observable in the infrared and are one of WISE's science goals. Further afield in the Milky Way, the emissions of dust in star forming regions can be detected as stars form surrounded by dusty disks. The most distant objects WISE will detetct are ultra-luminous infrared galaxies (ULIRGs) which are thought to result from the merging of two smaller galaxies. During galaxy mergers, clouds of interstellar gas collide and many stars are born. These young stars heat the remaining gas, which in turn emits infrared light.

Observing at infrared wavelengths has the advantage that objects for which optical wavelengths are obscured by dust can be studied. Light is easily scattered by particles that are smaller than it's wavelength in a process known as Rayleigh scattering, this is the same process by which Earth's atmosphere scatters blue light from the sun but transmits the red light straight through. Dust particles range in size and efficiently scatter visible light. By observing at infrared wavelengths we can see right through dust clouds to the concealed objects.  Active galactic nuclei and protostars are commonly obscured in such a way, and instruments such as WISE can be used to study them.

WISE is partially intended as a replacement for the ill-fated Wide Field Infrared Explorer (WIRE) which was damaged several hours after entering orbit due to a technical fault. WISE will fulfill the original science objectives with the added advantage of increased sensitivity and in addition contributes to the NASA near Earth object survey.

 

                  
Comet Siding Spring: The long red trail is ice and dust that is blown off by the sun and is much cooler than the blue background stars.  Nebula NGC3603: At the centre of this image is a cluster of hot massive stars that is heating and destroying the surrounding gas cloud.
  
   

Andromeda as observed in optical (left) and infrared (right) bands. Infrared can penetrate the dust that obscures star forming regions and highlights the high density spiral arms of Andromeda.

C. Gareth Few



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