Figure 1: Spectrum Charts Light from a Faraway Galaxy
This graph, or spectrum, charts light from a faraway galaxy located 10
billion light years from Earth. It tracks mid-infrared light from an
extremely luminous galaxy when the universe was only 1/4 of its current
age.
Spectra are created when an instrument called a spectrograph spreads light
out into its basic parts, like a prism turning sunlight into a rainbow.
They reveal the signatures, or "fingerprints," of molecules that make up
a galaxy and contribute to its light.
Spitzer's infrared spectrometer identified characteristic fingerprints of
complex organic molecules called polycyclic aromatic hydrocarbons,
illustrated in the artist's concept in the inset. These large molecules
comprised of carbon and hydrogen, are considered among the building blocks
of life.
Scientists determined it took 10 billion years for photons from this
galaxy to reach Spitzer's infrared eyes. These complex carbon and
hydrogen molecules are from a young galaxy which is undergoing intense
star formation, at the time the universe was only 3.5 billion years old.
These distant galaxies with enormous amounts of gas being converted into
young stars are some of the most luminous objects in the sky. Enshrouded
by dust, they are only faint, inconspicuous little dots in optical images. They are as bright as 10 trillion suns put together and 10 times brighter than starburst galaxies seen in our local universe.
This prompts a fascinating question as to what physical process is
driving such enormous energy production in these galaxies when the
universe is so young.
These data were taken by Spitzer's infrared spectrograph in August and
September 2004.