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Transcript of Colour
(as used by firemen to see through smoke, for example)
=> hot, young stars which don't live long
=> galaxy is actively “Star-forming”
=> only cool, old stars
=> galaxy is
away an object is in the distant Universe, the
its light appears
Eventually, the light from a distant object shifts
, because of its
Hubble Space Telescope
- mainly works at
James Webb Space Telescope
- Will mainly work in the
, allowing it to study much more distant objects
Blocked by the Earth's atmosphere
Must be studied from space (with
Credit: McGraw-Hill Observatory, Kitt Peak, Arizona, provided by Greg Bothum, Univ. of Oregon.
traces the hottest (shortest-lived, newest) stars and shows that new
is clearly concentrated
along the spiral arms
The Cosmic Microwave Background (CMB)
from the WMAP satellite
heat left over from the Big Bang
The radiation from the initial fireball has now been redshifted (stretched) so that it appears only
3 degrees above absolute zero
It appears as a glow over the whole sky at
The Square Kilometre Array (SKA)
not related to the temperature
of the object
(It is due to charged particles being accelerated in a magnetic field)
In this case, a
supermassive black hole
at the centre of the galaxy is
blowing out jets
Galaxy Centaurus A
Optical + radio image
The Southern African Large Telescope (SALT) in Sutherland
Not all UV is blocked
by the Earth's atmosphere.
The weakest (longest wavelength) UV still makes it through.
is an optical telescope, but it is optimised to observe in this
See: http://ska.ac.za for more info
Chandra X-ray Observatory
gamma ray burst telescope
Gamma ray bursts
are the most distant and powerful
Gamma Ray Bursts
Another way to study gamma rays -- from the ground!
-- High Energy Stereoscopic System
The HESS 1 array in Namibia
Large (12m) but relatively poor quality optical telescopes study the
gamma rays interact with the Earth's atmosphere
A larger HESS 2 array is being developed at the moment and Namibia is one of the countries bidding to host it.
The Orion Nebula, M42
Cloud of gas and dust in which new stars are being born
of) light from an object, in most cases, tells us about its
Optical/visible light is a tiny, tiny portion of the EM spectrum
Only by adopting a
approach can we hope to put together a complete picture of astrophysics.
Many of the state-of-the-art facilities which will allow this will be based in
Dr David Gilbank (SAAO)
Galaxies are "
cities of stars
Galaxy clusters contain a "dense" atmosphere of hot (~1 -10 million C) gas which emits strongly in X-rays
~12 000 C
(~30 C) radiate mostly in the IR
The Universe seen ~380 000 years after the Big Bang
3 distant galaxy clusters
of a star gives its
a star, the
faster it burns
its fuel, and so the shorter its lifetime
size of wavelength
roughly 1/1000 mm
The Electromagnetic Spectrum
Our Sun is ~6000 C
and emits most of its light here
wavelength (millionths of a metre)