Why Infrared Astronomy Is A Hot Topic

ESA News
http://www.esa.int

11 September 2003

Why infrared astronomy is a hot topic

ESA's Herschel spacecraft will collect infrared radiation from some of the
coldest and most distant objects in the Universe. But why are observations of
infrared light so special?

The Universe is full of radiation of all types but most of this does not reach
us here on Earth because our atmosphere blocks out many wavelengths of
radiation, but lets others through.

Fortunately for life on Earth, the atmosphere blocks out harmful, high-energy
radiation like X-rays, gamma rays and most ultraviolet rays. It also blocks out
most infrared radiation, except for a few narrow wavelength ranges that make it
through to ground-based infrared telescopes.

Our atmosphere causes another problem -- it radiates strongly in the infrared
itself, often putting out more infrared radiation than the object in space being
observed. This is why ground-based infrared observatories are usually placed
near the summits of high mountains to get above as much of the atmosphere as
possible.

This is why it is so important to put observatories into space, to get above our
atmosphere which prevents so much of this valuable information from reaching us.

So why is it so important to see in infrared?

Many of the things scientists want to observe in space are far too cold to
radiate at optical or shorter wavelengths, but radiate strongly in infrared, for
example, the cold atoms and molecules that drift in interstellar space. We need
to study these raw materials to understand how stars form and evolve.

"By observing in the infrared we can study how things get formed, the very early
steps, because formation processes very often happen in cool and dusty places,"
explains Göran Pilbratt, ESA's Herschel Project Scientist.

In our own Solar System, cold objects such as comets and asteroids reveal most
of their characteristics to us in infrared light.

Other things of great interest to astronomy are hidden within or behind vast
clouds of gas and dust. These clouds hide stars and planets in early stages of
formation and the powerful cores of active galaxies.

Our view is blocked because the dust grains are very effective at scattering or
absorbing visible light. Longer infrared wavelengths can get through the dust.

The future is extremely bright for infrared astronomy and, in the next decade,
you will hear a lot about ESA discoveries in infrared astronomy!

More about ...

* Herschel factsheet
http://www.esa.int/esaSC/SEMA539YFDD_index_0.html
* ISO overview
http://www.esa.int/esaSC/120396_index_0_m.html
* Planck overview
http://www.esa.int/esaSC/120398_index_0_m.html

Related articles

* Seeing the Universe in infrared
http://www.esa.int/esaSC/SEMS72T1VED_index_0.html
* L2, the second Lagrangian Point
http://www.esa.int/esaSC/SEMO4QS1VED_index_0.html
* The infrared explorers
http://www.esa.int/esaSC/SEM56TZO4HD_exploring_0.html

IMAGE CAPTIONS:

[Image 1:
http://www.esa.int/export/esaSC/SEMX...loring_1.html]
This is such an unusual view of the impressive M16 nebula, also known as 'The
Eagle', that even the most devoted sky-lovers will be surprised. It shows
exactly what in the best known pictures of this famous nebula remains invisible:
huge amounts of the cold dust that enshrouds newborn stars.

Credits: Photo: ESA/ISOGAL team

[Image 2:
http://www.esa.int/export/esaSC/SEMX...html#subhead2]
ISO unveils the hidden rings of Andromeda.

[Image 3:
http://www.esa.int/export/esaSC/SEMX...html#subhead3]
Rho Iophiuchi dark cloud

Credits: ESA/ISO/CEA Saclay/ISOCAM consortium