A Dangerous Dance

This Picture of the Week features two interacting galaxies that are so intertwined, they have a collective name — Arp 91. This delicate galactic dance is taking place over 100 million light-years from Earth, and was captured by the NASA/ESA Hubble Space Telescope. The two galaxies comprising Arp 91 do have their own names: the lower galaxy, which in this image looks like a bright spot, is known as NGC 5953; and the ovoid galaxy to the upper right is NGC 5954. In reality, both of these galaxies are spiral galaxies, but their shapes appear very different because they are orientated differently with respect to Earth.

Arp 91 provides a particularly vivid example of galactic interaction. NGC 5954 is clearly being tugged towards NGC 5953 — it looks like it is extending one spiral arm downwards. It is the immense gravitational attraction of the two galaxies that is causing them to interact. Such gravitational interactions between galaxies are common, and are an important part of galactic evolution. Most astronomers nowadays believe that collisions between spiral galaxies lead to the formation of another type of galaxy, known as elliptical galaxies. These immensely energetic and massive collisions, however, happen on timescales that dwarf a human lifetime — they  take place over hundreds of millions of years. So we should not expect Arp 91 to look any different over the course of our lifetimes!

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Credit:

ESA/Hubble & NASA, J. Dalcanton
Acknowledgement: J. Schmidt

About the Image

Id:potw2140a
Type:Observation
Release date:4 October 2021, 06:00
Size:3058 x 3425 px

About the Object

Name:Arp 91, NGC 5953
Constellation:Serpens Caput

Image Formats

Large JPEG
1.4 MB
Screensize JPEG
164.5 KB

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Wallpapers

1024x768
134.0 KB
1280x1024
209.8 KB
1600x1200
315.3 KB
1920x1200
397.7 KB
2048x1536
520.6 KB

Coordinates

Position (RA):15 34 33.16
Position (Dec):15° 11' 46.26"
Field of view:2.55 x 2.85 arcminutes
Orientation:North is 82.0° right of vertical


Colours & filters

BandWavelengthTelescope
Optical
G
477 nmSDSS
Optical
G
474 nmVíctor M. Blanco 4-meter Telescope
DECam
Optical
R
644 nmVíctor M. Blanco 4-meter Telescope
DECam
Optical
R
623 nmSDSS
Optical
I
785 nmVíctor M. Blanco 4-meter Telescope
DECam
Optical
I
762 nmSDSS
Optical
V
606 nm Hubble Space Telescope
ACS

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