The dust is generated by young stars, suggesting the newly observed galaxies could give us clues to the universe's most active star-formation period, NewsScientist.com reports.

Researchers at the Open University in Britain say the galaxies appear to observers on Earth as they were when the universe was 2 billion to 4 billion years old, less than a third its present age, a time when stars formed at roughly 100 times their current rate.

Young stars in the galaxies created dust that blocked visible light from escaping into space, but they also heated up the dust, causing it to radiate at far-infrared wavelengths detected by the European Space Agency's Herschel telescope.

Herschel was launched in May 2009.

Herschel can detect bands of far-infrared and sub-millimeter wavelength light that are blocked by Earth's atmosphere, but ground-based observatories can measure even longer millimeter wavelengths that may reveal objects at even greater distances, Tom Crawford of the University of Chicago says.

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