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The Universe at different wavelengths
One way of extending our perceptions of the Universe is to look at many different wavelengths, seeking to capture the emissions of photons of differing frequencies. By associating these photons with different processes at work, a wider picture of the Universe emerges.
Three radio telescopes tuned to 408 MHz (close to a broadcast television channel). Near this frequency, cosmic radio waves are generated by high energy electrons spiralling along magnetic fields. In the resulting false colour image, the galactic plane runs horizontally through the centre, but no stars are visible. Instead, many of the bright sources near the plane are distant pulsars, star-forming regions and supernova remnants, while the grand looping structures are pieces of bubbles blown by local stellar activity
The image shows the temperature distribution of the cosmic microwave background radiation over the celestial sphere, as observed by the COBE satellite at a wavelength of 5.7 mm, once the effect of the Earth’s motion through the background radiation has been removed.
Three major sources contribute to the far-infrared sky: our Solar System, our Galaxy and our Universe. This image, in false colour, is the highest resolution projection yet created of the entire far-infrared sky (60 – 240 mm). Our Solar System shows itself most prominently by the S-shaped blue sash called zodiacal light, created by small pieces of rock and dust orbiting between the Sun and Jupiter. The thin band of light-emitting dust that crosses the middle of the image indicates the disc of our Galaxy.
This is composite image taken from Earth orbit, well inside our Milky Way Galaxy. In light just a little too red for human eyes to see – 'near infrared' electromagnetic radiation – the disc and centre of our Galaxy stand out, giving an appearance probably similar to seeing our Galaxy from the outside in visible light.
This panorama view of the sky is really a drawing. It was made in the 1940s under the supervision of astronomer Knut Lundmark at the Lund Observatory in Sweden. To create the picture, draftsmen used a mathematical distortion to map the entire sky onto an oval shaped image with the plane of our Milky Way Galaxy along the centre and the north galactic pole at the top. 7000 individual stars are shown as white dots, size indicating brightness.
UV whole sky map. The plot is in galactic coordinates (the plane of our Galaxy runs horizontally through the middle) and reveals the positions of distant quasars, galaxies, stars, star clusters, nebulae, novae and supernovae – testifying to IUE's broad range of capabilities. The ecliptic plane is also visible running diagonally through the centre, traced out by many observations of solar system objects.
X-rays are about 1000 times more energetic than visible light photons and are produced in violent and high temperature astrophysical environments. Instead of the familiar steady stars, the sky would seem to be filled with exotic binary star systems composed of white dwarfs, neutron stars and black holes, along with flare stars, x-ray bursters, pulsars, supernova remnants and active galaxies.
This processed image represents a map of the entire sky at photon energies above 100 MeV. These gamma-ray photons are more than 40 million times more energetic than visible light photons and are blocked from the Earth's surface by the atmosphere. In the early 1990s NASA's Compton Gamma Ray Observatory, in orbit around the Earth, scanned the entire sky to produce this picture. A diffuse gamma-ray glow from the plane of our Milky Way Galaxy is clearly seen across the middle. The nature and even distance to some of the fainter sources remain unknown
Diffuse gas clouds laced with radioactive aluminium atoms (Al 26) line the plane of our Milky Way Galaxy! Relying on the Compton Effect, the COMPTEL instrument onboard NASA's immense orbiting Compton Gamma Ray Observatory can 'see' the 1.8 MeV gamma rays emitted by the radioactive decay. The radioactive Al 26 clouds are seen to lie in clumps near the plane, with some slightly above and below it. The brightest feature looks like a mysterious inverted 'V', just to the left of centre.
Interstellar space is filled with extremely tenuous clouds of gas which are mostly hydrogen. The proton and electron in hydrogen spin like tops but can have only two orientations; spin axes parallel or antiparallel. It is a rare event for hydrogen atoms in the interstellar medium to switch from the parallel to the antiparallel configuration, but when they do they emit radio waves with a wavelength of 210 mm and a corresponding frequency of exactly 1420 MHz. Radio telescopes tuned to this frequency have mapped the neutral hydrogen in the sky.
Our Earth is not at rest. The Earth moves around the Sun. The Sun orbits the centre of the Milky Way Galaxy. The Milky Way Galaxy orbits in the Local Group. The Local Group falls toward the Virgo Cluster of galaxies. But these speeds are less than the speed that all of these objects together move relative to the microwave background. In this all-sky map, microwave radiation in the Earth's direction of motion appears blueshifted and hence hotter, while radiation on the opposite side of the sky is redshifted and colder