Not-So-Close Encounter

The twin galaxies NGC 4496A and NGC 4496B dominate the frame in this image from the NASA/ESA Hubble Space Telescope. Both galaxies lie in the constellation Virgo, but despite appearing side-by-side in this image they are at vastly different distances from both Earth and one another. NGC 4496A is 47 million light-years from Earth while NGC 4496B is 212 million light-years away. The enormous distances between the two galaxies mean that the two cannot interact, and they only appear to overlap owing to a chance alignment. 

Chance galactic alignments such as this provide astronomers with the opportunity to delve into the distribution of dust in these galaxies. Galactic dust adds to the beauty of astronomical images — it can be seen in this image as the dark tendrils threading through both NGC 4496A and NGC 4496B — but it also complicates astronomers’ observations. Dust absorbs starlight, making stars seem dimmer and shifting their light towards longer wavelengths, a process that astronomers refer to as “reddening” (not the same thing as redshift). By carefully measuring how starlight from background galaxies is affected by dust in intervening galaxies, astronomers can map out where the dust is in the foreground galaxy’s spiral arms. The resulting “dust maps” help astronomers calibrate measurements of everything from cosmological distances to the types of stars populating galaxies.

Credit:

ESA/Hubble & NASA, T. Boeker, B. Holwerda, Dark Energy Survey, DOE, FNAL/DECam, CTIO/NOIRLab/NSF/AURA, SDSS 
Acknowledgement: R. Colombari

About the Image

Id:potw2209a
Type:Observation
Release date:28 February 2022, 06:00
Size:3944 x 3977 px

About the Object

Name:NGC 4496A, NGC 4496B
Constellation:Virgo
Category:Galaxies

Image Formats

Large JPEG
4.7 MB
Screensize JPEG
419.9 KB

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1024x768
297.5 KB
1280x1024
483.1 KB
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702.7 KB
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835.8 KB
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1.1 MB

Coordinates

Position (RA):12 31 39.34
Position (Dec):3° 55' 41.10"
Field of view:2.61 x 2.63 arcminutes
Orientation:North is 3.8° left of vertical


Colours & filters

BandWavelengthTelescope
Optical
u
354 nmSDSS
Optical
G
474 nmVíctor M. Blanco 4-meter Telescope
DECam
Optical
G
477 nmSDSS
Optical
R
623 nmSDSS
Optical
R
644 nmVíctor M. Blanco 4-meter Telescope
DECam
Optical
I
762 nmSDSS
Optical
Z
913 nmSDSS
Optical
Z
919 nmVíctor M. Blanco 4-meter Telescope
DECam
Optical
V
606 nm Hubble Space Telescope
WFC3

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