Wednesday, July 7, 2010

Portrait of the oldest light

Planck telescope reveals ancient cosmic light

BBC News: The picture is the first full-sky image from Europe's Planck telescope which was sent into space last year to survey the 'oldest light' in the cosmos... It shows what is visible beyond the Earth to instruments that are sensitive to light at very long wavelengths -- much longer than what we can sense with our eyes...

Dominating the foreground are large segments of our Milky Way Galaxy. The bright horizontal line running the full length of the image is the galaxy's main disc -- the plane in which the Sun and the Earth also reside. This is where most stars in the Milky Way form today; but because this picture only records light at long wavelengths (microwaves to the very far infrared) what we actually see are not stars at all.

Rather, what we see is the stuff that goes into making stars -- lots of dust and gas. Of particular note are the huge streamers of cold dust that reach thousands of light-years above and below the galactic plane...

But as beautiful as the Milky Way appears, its emission must be removed if scientists are to get an even better view of its mottled backdrop, coloured here in magenta and yellow. This is the famous cosmic microwave background (CMB) radiation... The CMB is the 'first light.' It is the the light that was finally allowed to move out across space once a post-Big-Bang Universe had cooled sufficiently to permit the formation of hydrogen atoms. Before that time, scientists say, the cosmos would have been so hot that matter and radiation would have been 'coupled' -- the Universe would have been opaque.

To see how the Planck sky differs from views obtained at other wavelengths, visit the Chromoscope website.
Image source here.