NGC 646
Galaxy in the constellation Hydrus
NGC 646
An image of space made by the Euclid telescope shows a bright barred spiral galaxy with two sweeping arms glowing in shades of blue and white against a deep black background dotted with stars. Its core is luminous. Its spiral arms curve gracefully outward to the left and down to the right, resembling a cosmic garland draped across the scene. A smaller, faint and round galaxy appears to the left of the barred spiral galaxy.
NGC 646 (right) with PGC 6014 (left) imaged by the Euclid Space Telescope
Observation data (J2000 epoch)
ConstellationHydrus
Right ascension01h 37m 21.1730s[1]
Declination−64° 53′ 40.499″[1]
Redshift0.027452±0.0000600[1]
Heliocentric radial velocity8,230±18 km/s[1]
Distance391.8 ± 27.5 Mly (120.13 ± 8.42 Mpc)[1]
Apparent magnitude (B)15.65
Surface brightness22.53 mag/arcsec2
Characteristics
TypeSAB(s)c pec?[1]
Other designations
PGC 6010, VV 443[1]

NGC 646 is a large barred spiral galaxy located in the constellation Hydrus.[2] Its speed relative to the cosmic microwave background is 8,145 ± 19 km/s, which corresponds to a Hubble distance of 120.1 ± 8.4 Mpc (~392 million ly). NGC 646 was discovered by British astronomer John Herschel on 2 November 1834.[3] It forms an interacting galaxy pair.[4]

Luminosity

The luminosity class of NGC 646 is III.[1] It has surface brightness equal to 14.69 mag/am2.[5] NGC 646 is a low surface brightness galaxy (LSB).[5] LSB galaxies are diffuse (D) galaxies with a surface brightness less than one magnitude lower than that of the ambient night sky.

Distance

The Hubble distance of PGC 6014, the galaxy to the east of NGC 646, is 106.4 ± 7.5 Mpc (~347 million ly).[6] A distance of approximately 45 million light years therefore separates these two galaxies which appear to be neighbors in the image. Their gravitational interaction, if there is any interaction, should therefore be of short duration.[3]

See also

References

  1. ^ a b c d e f g h "Results for object NGC 0646 NED01". NASA/IPAC Extragalactic Database. NASA and Caltech. Retrieved 2024-04-18.
  2. ^ "NGC 646 NED02 - Elliptical/Spiral Galaxy in Hydrus | TheSkyLive.com". theskylive.com. Retrieved 2024-04-15.
  3. ^ a b "New General Catalog Objects: NGC 600 - 649". cseligman.com. Retrieved 2024-04-18.
  4. ^ Danziger, I. J.; Schuster, H. -E. (1974-08-01). "The interacting galaxy system NGC 646". Astronomy and Astrophysics. 34: 301–303. Bibcode:1974A&A....34..301D. ISSN 0004-6361.
  5. ^ a b "NGC 600-699". astrovalleyfield.ca. Archived from the original on 20 April 2024. Retrieved 2024-05-03.
  6. ^ "Results for object NGC 0646 NED02". NASA/IPAC Extragalactic Database. NASA and Caltech. Retrieved 2024-04-18.


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