A window into the cosmic past

This image from the NASA/ESA Hubble Space Telescope shows the galaxy cluster PLCK G004.5-19.5. It was discovered by the ESA Planck satellite through the Sunyaev-Zel’dovich effect — the distortion of the cosmic microwave background radiation in the direction of the galaxy cluster, by high energy electrons in the intracluster gas. The large galaxy at the centre is the brightest galaxy in the cluster and the dominant object in this image, and above it a thin, curved gravitational lens arc is visible. This is caused by the gravitational forces of the cluster bending the light from stars and galaxies behind it, in a similar way to how a glass lens bends light.

Several stars are visible in front of the cluster — recognisable by their diffraction spikes — but aside from these, all other visible objects are distant galaxies. Their light has become redshifted by the expansion of space, making them appear redder than they actually are. By measuring the amount of redshift, we know that it took more than 5 billion years for the light from this galaxy cluster to reach us. The light of the galaxies in the background had to travel for even longer than that, making this image an extremely old window into the far reaches of the Universe.

This image was taken by Hubble’s Advanced Camera for Surveys (ACS) and Wide-Field Camera 3 (WFC3) as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.

Acknowledgement: D. Coe et al.

Credit:

ESA/Hubble & NASA, RELICS

About the Image

Id:potw1807a
Type:Observation
Release date:12 February 2018, 06:00
Size:4809 x 4121 px

About the Object

Name:PLCK G004.5-19.5
Type:Early Universe : Galaxy : Grouping : Cluster
Distance:z=0.54 (redshift)
Constellation:Sagittarius
Category:Galaxies

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9.6 MB
Screensize JPEG
262.2 KB

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Coordinates

Position (RA):19 17 4.62
Position (Dec):-33° 31' 25.70"
Field of view:2.40 x 2.06 arcminutes
Orientation:North is 50.0° left of vertical

Colours & filters

BandWavelengthTelescope
Optical
B
435 nm Hubble Space Telescope
ACS
Optical
V
606 nm Hubble Space Telescope
ACS
Optical
I
814 nm Hubble Space Telescope
ACS
Infrared
J
1.1 μm Hubble Space Telescope
WFC3
Infrared
J
1.25 μm Hubble Space Telescope
WFC3
Infrared
J/H
1.4 μm Hubble Space Telescope
WFC3
Infrared
H
1.6 μm Hubble Space Telescope
WFC3

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