This new image from NASA/ESA’s Hubble Space Telescope is one of the best views ever of Arp 4, a visible pair of galaxies in the Cetus constellation.
This Hubble image shows the pair of galaxies Arp 4. Image source: NASA / ESA / Hubble / J. Dalcanton, Dark Energy Survey / DOE / FNAL / DECam / CTIO / NOIRLab / NSF / AURA.
Arp 4 It consists of the small, bright spiral galaxy MCG-02-05-050a and the much larger spiral galaxy MCG-02-05-050.
This pair is located in the constellation Cetus, and was discovered by Dutch-Canadian astronomer Sidney van den Berg in 1959.
Arp 4 is the fourth object in the Halton Arp Atlas of Strange Galaxies, and one of six Arp objects in the “Low Surface Brightness Galaxies” section.
“The naming of Arp 4 comes from the Atlas of Strange Galaxies, compiled in the 1960s by astronomer Halton Arp,” Hubble astronomers explained in a statement.
“‘Unusual galaxies’ were selected and photographed to provide examples of strange and non-standard shapes, the best way to study how galaxies evolve into these shapes.”
Throughout its mission, Hubble has revolutionized the study of galaxies and shown us some fantastically extraordinary examples from the Arp Atlas.
In this catalogue, the first few galaxies like Arp 4 are low surface brightness galaxies, a type of galaxy that is unexpectedly faint and difficult to detect.
“The large galaxy here – also designated as MCG-02-05-050 – fits this description well, with its fragmented arms and faint disk,” the astronomers said.
“Its smaller companion, MCG-02-05-050a, is a much brighter and more active vortex.”
“The trick is that these galaxies are not actually very close,” they said.
“The large blue galaxy MCG-02-05-050 is located 65 million light-years from Earth.”
“Its smaller, brighter companion, MCG-02-05-050a, is located 675 million light-years away, more than ten times the distance!”
“For this reason, MCG-02-05-050a is likely the larger galaxy of the two galaxies, and MCG-02-05-050 is relatively small.”
“Their pairing in this photo is just an improbable visual coincidence,” they noted.
“Although there is no physical relationship between them, our perspective on Earth allows us to enjoy the sight of Arp 4 as a strange couple in the sky.”