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Astronomers have spotted a galaxy so distant that we can observe it as it was near the dawn of time. But instead of looking like other infant systems they've seen, the galaxy is surprisingly far along in its star production.
This could mean that galaxies evolve more quickly than previously assumed -- and if other early galaxies churned out stars at the same rate as this one, astronomers may be more capable of observing them than we'd thought, too. The new findings were published Monday in Nature.
Galaxy A1689-zD1 is so distant that you can barely see it in the massive Hubble image above. But it sits behind a massive cluster of galaxies called Abell 1689, which is so big that it acts as a gravitational lens and magnifies the light of A1689-zD1 by over nine times.
Because A1689-zD1 is so distant, the traces of it that reach us today show the galaxy as it was just 700 million years after the birth of the universe; when the cosmos was a mere 5% of its current age.
But the galaxy has a ratio of something called cosmic dust that astronomers would only expect to see in a much older galaxy.
These particles, which are made up of elements like carbon, silicon, magnesium, iron, and oxygen, are absolutely essential to the formation of life. These elements are formed in the hearts of stars, then pushed out into clouds of dust and gas when the stars explode. These clouds seed new stars, and astronomers thought (based on previously observed ancient galaxies) that it would take generations of star birth and deaths to evolve the heavier elements that they see in A1689-zD1.
"Although the exact origin of galactic dust remains obscure," lead researcher Darach Watson of the University of Copenhagen said in a statement, "our findings indicate that its production occurs very rapidly, within only 500 million years of the beginning of star formation in the Universe -- a very short cosmological time frame, given that most stars live for billions of years."
Watson and his colleagues believe that previous galaxies of this cosmic age may have been too large to show typical evolution. The smaller A1689-zD1 is more of an average system, at least size-wise, so it may be more representative of the early universe as a whole.
If that's the case, we may have hopes of seeing many more of these early galaxies using the Atacama Large Millimeter/submillimeter Array (ALMA), which was used to study A1689-zD1. That's because active galaxies are easier to spot: When the ultraviolet light of young stars hits nearby cosmic dust, the result is the emission of far-infrared light. With more active stars and more dust, there's more far-infrared for ALMA to spot.
