Astronomers have long dreamed of observing the earliest stars in the universe: The ones built from the original matter spewed out of the Big Bang. These young stars have eluded astronomers and thus were considered to be a rare sighting in the sky. That is, until now.
Using ESO's Very Large Telescope (VLT), astronomers led by David Sobral have seen the first proof that these stars, called Population III stars, exist. Their research has been accepted for publication in The Astrophysical Journal.
Population III stars live hard, bright and fast, surviving for only around 2 million years before exploding in a supernova. For comparison, our sun has a predicted lifetime of 11 billion years before it explodes. Population III stars should be very pure, containing only hydrogen, helium, and maybe a smattering of lithium. They shouldn't contain any elements heavier than that. The team discovered some galaxies that match these criteria—including the galaxy CR7.
"CR7 is the first distant galaxy that matches all predictions for PopIII stars and where we find no traces at all of C (Carbon), O (Oxygen), N (Nitrogen) or any other heavy elements. This is the first time one sees such a unique source," Sobral told IFLScience.
The team's success in finding this rare galaxy might be due to their novel approach in surveying the universe. The convention in the community is to look at one, small patch of sky.
Sobral commented on their approach, "Instead of simply going deeper and deeper on small areas, we are undertaking very wide surveys (a few tens of full moons in the sky, compared with just a handful at best of full moons), to look for the most distant galaxies. One of the reasons why almost no-one was doing this is because people thought these bright galaxies should be so, so rare that it would be pointless to look for them."
Just goes to show you shouldn't be afraid of trying something new!
These stars were considered to be rare because of their short timespan; we might have been too late to see them. But, thanks to Sobral's novel approach, the team found that these early universe galaxies are "30 to 100 times or so more common than thought."
Sobral is determined to see CR7 in higher resolution. "We hope to use Hubble, to further understand the properties of CR7 in greater detail, but also to use ALMA for the same purposes." So we have some glistening pictures of the brightest galaxy in the universe to look forward to!
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