Hubble finds 'most distant' stars
A fuzzy cluster of stars 13.3 billion light years away is believed to be the most distant object ever observed.
Light from the tiny embryonic galaxy began its journey to Earth just 420 million years after the Big Bang that created the universe.
Scientists think the object, code-named MACSO647-JD, could be one of the building blocks of the early cosmos.
The galaxy dates back to when the universe was just 3% of its present age of 13.7 billion years.
It was imaged with the help of a natural “zoom lens” more powerful than any man-made telescope.
Gravity from a huge cluster of galaxies between the Earth and MACSO647-JD bent light rays from the object in a way that massively magnified its image.
The “gravitational lensing” effect allowed astronomers to photograph the galaxy using the Hubble Space Telescope.
Dr Marc Postman, from the Space Telescope Science Institute in the US, who led the Cluster Lensing And Supernova survey with Hubble (Clash) team, said: “The cluster does what no man-made telescope can do. Without the magnification, it would require a Herculean effort to observe this galaxy.”
It is the second time the record for the most distant object has been broken this year.
In April, Clash astronomers announced the discovery of a galaxy that existed when the universe was about 490 million years old, making it more remote than anything seen before. The new galaxy is 70 million years older than this object.
MACS0637-JD is less than 600 light years across, making it a galactic microbe. In comparison, the Milky Way is 150,000 light years wide. The baby galaxy has a mass roughly equivalent to between 0.1 and 1% that of all the stars in the Milky Way.
Dr Dan Coe, also from the Space Telescope Science Institute, said: “This object may be one of the many building blocks of a galaxy. Over the next 13 billion years, it may have dozens, hundreds or even thousands of merging events with other galaxies and galaxy fragments.”
The team spent months confirming that the object really was a distant galaxy. Some nearby objects such as red stars, brown dwarf stars and dusty star clusters can mimic the appearance of a very distant galaxy.
The Hubble telescope was used to observe three magnified images of MACS0637-JD produced by gravitational lensing.
To check the results, astronomers also studied images from the American space agency Nasa’s Spitzer Space Telescope.
Galaxy distances are measured by looking at their “red shift” – the extent to which their light waves are stretched and made redder as the expanding universe carries them away from the Earth. A similar Doppler effect causes the pitch of a police car siren to lower as the vehicle races away from a listener.
MACS0647-JD had a “redshift” of around 11, meaning that its light was so stretched it could only be seen through near-infrared filters.
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