Hubble Sneaks a Peek at Ancient Galaxy from The Dawn of the Cosmos

By James Maynard

An ancient galaxy seen as it was just 500 million years after the Big Bang, SPT0615-JD, could provide astronomers with new insights into the nature of the Universe in the distant past. This tiny cluster of stars – approximately just one percent of the size of our galaxy – may be among the oldest such formations in the Cosmos.

Hubble Space Telescope images were used to study the formation, along with an assist from nature in the form off gravitational lensing. This is a phenomenon where images from distant objects may be seen in greater detail than normally available, as light bends around a massive object, acting as a telescope. Without such a well-placed intermediary object, most targets seen at that distance are only seen as small red spots.

“Pretty much every galaxy at that distance is an unresolved dot… it’s kind of a matter of luck to get a galaxy that’s lensed in just the right way to stretch it out and get that much detail – it’s a pretty nice find,” Brett Salmon of the Space Telescope Science Institute told BBC News.

Astronomers typically measure the enormous distances to far-flung galaxies and quasars by measuring how light from the object differs compared to how it would appear if it were close. As the Universe expands, electromagnetic waves are lengthened, in much the same way as the pitch of a siren becomes deeper as the object moves away from the observer. This effect is known as the Doppler effect, and astronomers denote this measurement with the nomenclature Z.

The object which was the target of this study was seen at a distance of around  Z=10, or around 13 billion light years from Earth. at the limits of Hubble’s ability to image objects. Astronomers know of approximately 2,000 galaxies seen at distances between Z=9 and 12, although only a tiny fraction are seen with enough detail for intensive study. The James Webb Space Telescope, scheduled for launch in 2019, should resolve galaxies like SPT0615-JD in far greater detail.

Analysis of the study is available from the Cornell University Library.


Photo: Space Telescope Science Institute / NASA , ESA, and B. Salmon (STScI)



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