How to see Invisible Things: Multi-wavelength Astronomy

While my project will involve looking mainly at X-Ray data, in astronomy it is always important to keep the big picture in mind. Every different category of light is important and gives us individual information which should be considered. This is a summary of the different wavelengths of light astronomers use and the objcts they are particularly useful for.

(I first blogged this for the National Space Centre here)

Humans have been looking out into space for thousands of years and finding lots of weird and wonderful objects among the stars. Using only our eyes and various strengths of telescopes we can spot thousands of these astronomical features, but this is only a fraction of the fascinating and exotic phenomena out there.

The Electromagnetic Spectrum

The Electromagnetic Spectrum

The light our eyes recognise is a small selection of the whole electromagnetic spectrum; there are many different wavelengths of light and all of them tell us something about the objects they come from. To discover all we possibly can about astronomical phenomena, light of all these different wavelengths is gathered and analysed by specially designed telescopes.

Electromagnetic radiation and Earth's atmosphere

Electromagnetic radiation and Earth’s atmosphere

Different wavelengths are more important for different types of objects. This is mainly because the wavelength is inversely proportional to the energy of that light; the shorter the wavelength, the more energetic the light wave. Using this you can understand why the most energetic events in the cosmos emit mostly very short wavelengths of light.

Some wavelengths of light are blocked or absorbed by the Earth’s atmosphere. To study those that are we have to send telescopes above the atmosphere and into space.

Below are some examples of what each type of wavelength can be used for (starting with the longest wavelengths):

The Lovell Telescope at Jodrell Bank, Manchester, UK

The Lovell Telescope at Jodrell Bank, Manchester, UK

Radio waves

Wavelengths: 10,000 metres – 0.001 metres, which is 10km – 1mm (roughly)

Example telescopes: Lovell Telescope (Jodrell Bank, Manchester, UK), LOFAR (various sites around Europe, including Chilbolton, UK)

Primarily used to study: Radio galaxies (active galaxies with large amounts of radio emission), first observations of the Cosmic Microwave Background (CMB), interstellar molecules.

Artist impression of Mars Express over Mars. Credit: ESA

Artist impression of Mars Express over Mars. Credit: ESA

Microwaves (radar astronomy)

Wavelengths: 0.3 metres – 0.001 metres, which is 30cm – 1mm (yes I know this is part of the radio wavelengths above, but the difference is that radar astronomy actively reflects signals off objects whereas radio astronomy simply detects signals)

Example telescopes: Mars Express’ Marsis Subsurface Sounding Radar/Altimeter (Mars’ orbit), Magellan’s Radar System (Venus’ orbit)

Primarily used to study: Surface features of terrestrial planets and moons, asteroids and comets.

Rosette Nebula as seen by the Herschel Space Telescope. Credit: ESA

Rosette Nebula as seen by the Herschel Space Telescope. Credit: ESA

Infrared

Wavelengths: 0.003 metres – 0.0000007 metres, which is 0.3mm – 0.7 microns (roughly) (1 micron = astronomy shorthand for 1 micrometre)

Example telescopes: Herschel Space Observatory, Spitzer Space Telescope, James Clarke Maxwell Telescope (Hawaii, USA)

Future telescopes: James Webb Space Telescope, current launch date: 2018

Primarily used to study: Dusty regions in space, star formation, cool stars and distant ‘red-shifted’ galaxies.

The Pinwheel Galaxy (M101) as seen by Hubble. Credit: NASA/ESA

The Pinwheel Galaxy (M101) as seen by Hubble. Credit: NASA/ESA

Visible

Wavelengths: 0.0000007 metres – 0.0000004 metres, which is 0.7 microns – 0.4 microns (roughly)

Example telescopes: Hubble Space Telescope, Twin Keck Telescopes (Hawaii, USA)

Future Telescopes: European Extremely Large Telescope (E-ELT), current completion date: early 2020s

Primarily used to study: objects in our Solar System, nebulae and galaxies.

 

Our Sun in ultraviolet light, taken by SOHO. Credit: NASA

Our Sun in ultraviolet light, taken by SOHO. Credit: NASA

Ultraviolet

Wavelengths: 0.0000003 metres – 0.000000003 metres, which is 0.3 microns – 3nm (roughly) (1nm = 1 nanometre)

Example telescopes: Hubble Space Telescope, Solar and Heliospheric Observatory (orbiting the Sun)

Primarily used to study: very young massive stars, bright nebulae, white dwarf stars, active galaxies, our Sun.

 

X-Ray image of supernova remnant W49b, taken by Chandra. Credit: NASA

X-Ray image of supernova remnant W49b, taken by Chandra. Credit: NASA

 

X-Rays

Wavelengths: 0.000000003 metres – 0.0000000003 metres, which is 3nm – 0.3nm (roughly)

Example telescopes: XMM-Newton Space Observatory, Chandra X-Ray Observatory

Primarily used to study: Active galactic nuclei, our Sun, supernovae, white dwarfs.

 

A Gamma-Ray burst seen by INTEGRAL. Credit: ESA

A Gamma-Ray burst seen by INTEGRAL. Credit: ESA

Gamma Rays

Wavelengths: 0.0000000003 metres – 0.000000000003 metres, which is 0.3nm – 0.003nm (roughly)

Example telescopes: INTEGRAL Space Telescope, Fermi Gamma-Ray Space Telescope

Primarily used to study: Solar flares, neutron stars, active galaxies, supernovae and gamma-ray bursts.

 

 

All these wavelengths of light add to the information astronomers can get about the universe around us. They all have their own speciality areas, but multi-wavelength studies (looking at the same object in many different wavelengths) are becoming important more than ever before.

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2 thoughts on “How to see Invisible Things: Multi-wavelength Astronomy

  1. […] mentioned in my previous post, X-rays cannot penetrate the Earth’s atmosphere, so any observations of astronomical X-rays […]

  2. […] You can do exactly the same in all wavelengths of light, not just visible. (For more on multiwavelength astronomy see my previous post here). […]

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