“The Stars are Painted with Unnumber’d Sparks…”

Little did William Shakespeare know how true were those words he made Caesar utter. Our eyes can see only ‘visible light’ which is a small amount of the electromagnetic spectrum, there is so much more we can’t see without the help of technology.

The Electromagnetic spectrum is a term which scientists use to describe the entire range of light that exists: everything from radio waves to gamma rays, including x-rays and microwaves are all forms of light.

elctromagnetic-spectrum

Electromagnetic spectrum. (NASA)

As can be seen from the chart visible light covers just a fraction of what there is to see. It turns out that different objects in the universe radiate at different wavelengths, some we can see – like light – some we can’t. Some can be observed from Earth – for example radio waves – and some can’t, because the Earth’s atmosphere blocks them, like gamma rays.

For wavelengths absorbed by the atmosphere we have to build satellites and send them into space – often a good distance from Earth to allow them to be cool enough to do their work; the Herschel Space Observatory which observed the infrared orbits 1,500,000 kilometres (930,000 miles) from Earth (by comparison the International Space Station orbits just 400 kilometres from Earth.)

Objects can emit radiation at different wavelengths and that can give us additional insights into their nature. The hotter the object, the shorter the wavelength (the distance between two peaks or crests) and the more energetic it is.

shape-of-wavelength

The shape of an electromagnetic wave (radio, visible etc.)

The following images of the Sun were taken in ultraviolet and visible light on the same day. The difference in what you can see is remarkable;

 

sun-in-uv

UV light.

sun-in-visible

Visible light.

Astronomers at the Murchison Wide Field Array (MWA) radio telescope in Australia decided to observe the universe at radio wavelengths. The survey known as the GaLactic and Extragalactic All-sky MWA (GLEAM) shows what the Milky Way and 300,000 galaxies look like if we could see radio waves.

The human eye can only see three primary colours (red, blue and green), the Mantis shrimp can see in twelve primary colours, GLEAM ‘saw’ in twenty primary colours, beating every living thing and revealed the remnants of explosions from the most ancient stars in our galaxy, and the first and last gasps of supermassive black holes;

galaxy-visibleIn visible light.

 

galaxy-radioIn radio light.

And if you want to see what it all looks like in a variety of wavelengths try this;

http://gleamoscope.icrar.org/gleamoscope/trunk/src/

The MWA is soon to become part of the Square Kilometre Array (SKA) of radio telescopes working with radio observatories in South Africa and Jodrell Bank. Together they will be able to make even better maps of those unnumber’d sparks.

 

 

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