Transcript The Electromagnetic Spectrum: Astronomy 1

Image courtesy VSA
Microwave: The Cosmic Microwave Background (CMB). Shortly
after the Big Bang, the Universe cooled enough to allow atoms to
form. After this point in time, radiation was able to travel freely
through the Universe. Initially, the radiation (known as the CMB)
from this epoch had a short wavelength, however as the Universe
expanded the wavelength increased. Today, the finger print of the
Big Bang is best seen at microwave wavelengths. Below is an
image of the CMB made by the Very Small Array. It is effectively a
view of the universe at a minute fraction of its current age
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Image courtesy Chandra
Short wavelength
High frequency
10-6m 10-7m 10-8m 10-9m 10-10m 10-11m 10-12m <10-13m
infrared
ultraviolet
visible
Infrared: The Constellation Orion. Vast regions of dust and
gas are warmed by stars and glow brightly in the infrared
region of the spectrum. The bright area in the lower right of
the image below is Orion’s sword, containing the Great
Orion Nebula. Can you spot the star Betelgeuse, which
shows up as a blue/white dot in the upper centre? The ring
to the right of Betelgeuse is the remnant of a supernova
(the dying explosion of a giant star).
X-ray
Ultraviolet: The galaxy M94. Here clusters of
bright, young stars have formed a ring
nearly 7,000 light years across. The stars
are very hot and show up in the ultraviolet
region of the spectrum. The image was
made with a telescope carried aboard a
space shuttle.
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Lord’s Bridge
gamma ray
The Gamma Ray Universe. The highest energy
objects in the sky emit gamma rays. Our galaxy, the
Milky Way, is the bright band across the image
below. The bright spots within it are pulsars (rapidly
rotating dead stars; see X-rays above). Other bright
points are distant quasars (old galaxies containing
massive black holes). Many of the faint sources
have an unknown origin.
Image courtesy NASA/CGRO
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radio microwave sub-mm
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X-rays: The Crab Pulsar. At the centre of the Crab Nebula
is a pulsar – a rapidly rotating neutron star (the compact
remains of a dead, massive star) that emits a beam of
radio waves. The beam is detected as a pulse of radiation
as it sweeps past an observer – similar to a flashing
lighthouse. The strong magnetic field around the pulsar
propels material in the nebula at speeds close to the
speed of light. Heated up, this material emits X-rays.
Image courtesy NASA/UIT
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Image courtesy IRAS
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Visible: The Eskimo Nebula. The end of the
life of a low mass star, like our sun, is marked
by the formation of a planetary nebula. When
this star ran out of fuel, it threw off its outer
layers of gas. This image was taken by the
Hubble space telescope, tracing emission
from nitrogen (red), hydrogen (green), oxygen
(blue) and helium (violet).
The Electromagnetic Spectrum:
Astronomy
Long wavelength
Low frequency
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Image courtesy NASA/HST
Image courtesy JCMT/SCUBA
Image courtesy NRAO/AUI
Sub-millimetre: Cassiopeia A. At the end of
their lives, massive stars explode as
supernovae, ejecting large amounts of dust
and gas. This image was made with the
James Clerk Maxwell Telescope at submillimetre wavelengths. It shows the position
of cold dust (18K) that was thrown out from a
supernova witnessed 300 years ago.
Radio waves: The Whirlpool Galaxy. A
spiral galaxy to be found in the
constellation of Canes Venatici. This image
was made at radio wavelengths and shows
the location of cold gas within the galaxy.
The bright red patch on the left of the
image is a distant quasar, a type of early
galaxy containing a massive black hole.