NGC 4567 and NGC 4568

NGC 4567 and NGC 4568 (nicknamed the Butterfly Galaxies[4] or Siamese Twins[NB 1][5]) are a set of unbarred spiral galaxies about 60 million light-years away[1] in the constellation Virgo. They were both discovered by William Herschel in 1784. They are part of the Virgo Cluster of galaxies. Only one supernova (SN 2004cc) was observed in the Butterfly Galaxies until March 31, 2020, when the Zwicky Transient Facility detected the rapidly-rising supernova 2020fqv.[6]

NGC 4567 and NGC 4568
The Butterfly Galaxies with NGC 4567 (top) and NGC 4568 (bottom)
Observation data (J2000.0 epoch)
ConstellationVirgo
Right ascension12h 36m 34.3s
Declination+11° 14′ 17″
Distance59.4 Mly (18.2 Mpc)[1]
Apparent magnitude (V)+10.9
Absolute magnitude (V)-13.3
Characteristics
TypeSA(rs)bc / SA(rs)bc
Apparent size (V)4.6′ × 2.1′
Notable featurescolliding galaxies
Other designations
NGC 4567/8, UGC 7776/7, PGC 42064/9, VV 219,[2] KPG 347,[3] Butterfly Galaxies,[4] Siamese Twin Galaxies, Siamese Twins Galaxies, Siamese Twins[5][NB 1]

These galaxies are in the process of colliding and merging with each other, as studies of their distributions of neutral and molecular hydrogen show, with the highest star-formation activity in the part where they overlap. However, the system is still in an early phase of interaction.[7]

Naming controversy

They were nicknamed "Siamese Twins" because they appear to be connected. On August 5, 2020, NASA announced that they would not use that nickname in an effort to avoid systemic discrimination in their terminology.[8][9]

  • NGC 4567 and 4568 imaged by the Hubble Space Telescope
  • RGB image of the colliding galaxies NGC 4567 and NGC 4568. Data from the Liverpool Telescope on La Palma, processed by Göran Nilsson. Exposure: 20 × 90 s
  • Siamese Twins as imaged in the Liverpool Telescope on La Palma. Unrelated objects have been edited out.

See also

Notes
  1. NASA no longer uses the "Siamese Twins" terms due to perceived discriminatory naming

References
  1. "Distance Results for NGC 4568". NASA/IPAC Extragalactic Database. Retrieved 2010-05-01.
  2. "VV 219 -- Interacting Galaxies". SIMBAD.
  3. "KPG 347 -- Pair of Galaxies". SIMBAD.
  4. Cong Xu; Yu Gao; Joseph Mazzarella; Nanyao Lu; Jack W. Sulentic; Donovan L. Domingue (2000). "Mapping IR Enhancements in Closely Interacting Spiral-Spiral Pairs. I. IS0 CAM and IS0 SWS Observations". 10.1.1.317.8256. Cite journal requires |journal= (help)CS1 maint: uses authors parameter (link)
  5. Cudnik B. (2013). "The Nature of Galaxies and Galaxy Clusters". Faint Objects and How to Observe Them. Springer. doi:10.1007/978-1-4419-6757-2_4.
  6. "SN 2020fqv". Transient Name Server.
  7. Kaneko, H.; Kuno, N.; Iono, D.; Tosaki, T.; Sawada, T.; Nakanishi, H.; Hirota, A. (2010). "Molecular Gas in the Early Stage of Interacting Galaxies: The NGC 4567/8 Pair". Galaxy Wars: Stellar Populations and Star Formation in Interacting Galaxies. 423: 26. Bibcode:2010ASPC..423...26K.
  8. Jack Hobbs (2020-08-08). "NASA to remove offensive names from planets and other heavenly bodies". New York Post.
  9. Haworth, Jon (August 9, 2020), "NASA drops 'insensitive' celestial nicknames in effort to address systemic discrimination", ABC News, retrieved 2020-08-10


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