Herschel Space Telescope uncovers the sources of the Cosmic Infrared Background

December 16, 2009
Herschel-PACS images of the ‘GOODS-N’ field in the constellation of Ursa Major at far-infrared wavelengths of 100 and 160m. Galaxies at high redshift (i.e. larger cosmological distance) or with colder dust are displayed in red, while nearby galaxies appear in blue. Image: ESA

(PhysOrg.com) -- Using first observations with the PACS Instrument on board ESA’s Herschel Space Telescope, scientists from the Max Planck Institute for Extraterrestrial Physics and other institutions have for the first time resolved more than half of this radiation into its constituting sources. Observations with Herschel open the road towards understanding the properties of these galaxies, and trace the dusty side of galaxy evolution.

In the mid 1990’s, scientists analyzing data from NASA’s COBE spacecraft discovered faint in the far-infrared part of the electromagnetic spectrum that reaches earth with the same intensity from all directions in space. Immediately, they suspected it to be the aggregate emission of many distant galaxies in the , releasing the same amount of energy in the far-infrared as reaches us in visible light from similarly distant galaxies. Whereas visible light tells us about the stars in galaxies, the far-infrared is emitted by cold dust that is hiding the newly formed stars.

Identifying these surprisingly numerous dusty galaxies has proven difficult, though. Space telescopes are needed to detect far-infrared emission, because it is absorbed by the Earth’s atmosphere. Previous infrared space telescopes have detected far-infrared light from only the brightest of the galaxies forming this cosmic background. To glean any information about the fainter objects, astronomers had to rely on indirect evidence based on shorter radiation.

ESA’s Herschel , launched in May 2009, is the largest ever built with a mirror diameter of 3.5m. Its PACS instrument is designed to take high-resolution images of the sky at far-infrared wavelengths of 70 to 160m, exactly where most of the cosmic infrared background emission is received. "After the check-out of our instrument, we were yearning to obtain the first deep far-infrared observations of the sky," says Albrecht Poglitsch, principal investigator of PACS.

For a total of 30 hours in October, PACS has observed a small patch of sky in the constellation of Ursa Major, about a quarter of the size of the full moon. "Already in these first observations, we have resolved about 60% of the cosmic infrared background from this region of sky into individual well-detected sources," says Dieter Lutz from the consortium of scientists from five European institutes that have obtained the data. "And this is just the beginning. Yet more sensitive observations will follow soon, and we will be able to understand in detail the epoch of activity and the properties of the galaxies that produce the cosmic infrared background, now that we have pinned them down."

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not rated yet Dec 16, 2009
It would be nice if some distances or identifications were given to some of these point sources.
not rated yet Dec 17, 2009
OK... it seems (to me) that popular (layman's) science literature and recent science has once again developed some rather large gaps.

I have been under the misguided impression that the CMB was the remnents or echoes of the big bang itself. Was that not the theory based on the premise that the radiation originates from every direction we can observe from Earth? I remember scientists claimed in was responsible for, (or at least similar to), the static received on radios and TVs when they are not tuned to a station.

The same idea was given in literature and documentaries, but I will have to check which.

Now, however, the CMB is being attributed to an 'infinite' number of ancient/distant galatic sources?

Wow. 8-/

"Stars" really "are but pinholes in the curtain of night" ???
5 / 5 (3) Dec 17, 2009

The PR and article should have stated that this was a detection of point sources that contribute to the cosmic infrared background (CIB) as opposed to the separate cosmic microwave background (CMB). COBE and WMAP made observations of both the CMB and the CIB, but of course, the CMB observations got most of the headlines. See Wikipedia for a good summary of the CIB: http://en.wikiped...ckground . Your confusion is understandable.
not rated yet Dec 18, 2009
yyz: Thank you.

Wish more people took the time to explain things so well, and in such a civilised manner.

May I take this opportunity to wish you a Merry, and Happy, Christmas ... and I look forward to your contributions in the new year.

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