This is Scientific American 60-Second Science. I'm Christopher Antalyatta.

If you've ever looked up at the Milky Way, you've seen what's known as cosmic dust.

When you see this band right off the Milky Way, you can see these dark patches. And so

that's really just dust that is obscuring the stars behind it.

Pascal Ush is an associate professor at the University of Geneva. He points out that

cosmic dust isn't exactly the kind of dust you or I might be familiar with.

Cosmic dust is not quite the same as the dust we know from the apartment here, but it's

cosmic dust that's really just very small particles in the universe that are consisting

maybe just a few molecules, often containing carbon or silicate.

And as in that Milky Way example, the cosmic dust absorbs the light of stars behind

it, making it harder for us to see those stars, with instruments like the Hubble Space Telescope.

But there is one way around that. Astronomers can observe the sky with longer wavelengths,

using telescopes like the Attacama Large Millimeter Sub-Millimeter Array in Chile, or Alma.

With Alma, astronomers can see even the dust bunnies hiding up in the sky, because as

the dust absorbs photons from the stars behind it, it heats up.

And so then, with Alma, we can directly see the emission of this heated-up dust, even

in the very early universe.

Ocean and his team have now stumbled upon two previously obscured galaxies, using Alma

observations. The galaxies date back to the very earliest days of the universe, 13 billion

years ago.

So those are the first building blocks of the galaxies that we see around us in the universe

today. So these are the first kind of LEGO stones. And apparently we have been missing

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