A 14-hour exposure image cluster taken by the Hubble Space Telescope shows objects around a billion times fainter than can be seen with the naked eye.
The image of a galaxy cluster gives astronomers an amazing cross-section of the Universe, showing objects at various distances and stages in cosmic history.
The galaxies in this image lie mostly within around five billion light-years of Earth. The image field also includes objects that are both closer and more distant. This new Hubble image is a showcase for an incredible variety of objects at different distances from us, extending back over halfway to the edge of the observable Universe.
In order to snag distant and dim objects like these, Hubble needed a long exposure time. The image is made up of visible and infrared observations with a total exposure time of 14 hours.
Because of a process called gravitational lensing, the objects seen are sometimes distorted.
Gravitational lensing is a very valuable technique in astronomy for studying very distant objects. It is able to amplify the light coming from distant objects, allowing telescopes like Hubble to see objects that would otherwise be too faint and far away.
This effect will be used in the Frontier Fields observing campaign in the near future, which aims to combine the power of Hubble with the natural amplification caused by strong gravitational lensing of distant galaxy clusters, to study the past Universe.
Gravitational lensing is caused by the bending of the space-time continuum by massive galaxies lying close to our line of sight to distant objects.
CLASS B1608+656One of the systems that can be seen here is called CLASS B1608+656, which appears as a small loop in the centre of the image. It includes two foreground galaxies distorting and amplifying the light of a distant quasar.
The light from this bright disc of matter, which is currently falling into a black hole, has taken nine billion years to reach us, two thirds of the age of the Universe. In addition to CLASS B1608+656, astronomers have identified two other gravitational lenses within this image.
Two galaxies, nicknamed Fred and Ginger by the researchers who studied them, contain enough mass to visibly distort the light from objects behind them. Fred, also known more prosaically as [FMK2006] ACS J160919+6532, lies near the lens galaxies in CLASS B1608+656, while Ginger ([FMK2006] ACS J160910+6532) is markedly closer to us.
Despite their different distances from us, both can be seen near to CLASS B1608+656 in the central region of this Hubble image.
The image was found by Adam Kill in the 2012 Hubble’s Hidden Treasures competition. Hidden Treasures invited members of the public to search Hubble’s science for the best overlooked images that have never been seen by a general audience.
This image of CLASS B1608+656 has been well-studied by scientists over the years, but this was the first time it has been published in full online.
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