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.

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″
Distance62 Mly (19.1 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.[6]

Four supernovae have been observed in the Butterfly Galaxies: SN 1990B (type Ib, mag. 16),[7] SN 2004cc (type Ic, mag. 17.5),[8] SN 2020fqv (type IIb, mag. 19),[9] and SN 2023ijd (type II, mag. 16.8).[10]

SN 2023idj in NGC 4568 as seen on 2023-May-17.

Naming controversy

The two galaxies 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.[11]

See also
Wikimedia Commons has media related to NGC 4567.
Wikimedia Commons has media related to NGC 4568.

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}}: Cite journal requires |journal= (help)
  5. Cudnik B. (2013). "The Nature of Galaxies and Galaxy Clusters". Faint Objects and How to Observe Them. Astronomers' Observing Guides. Springer. pp. 71–91. doi:10.1007/978-1-4419-6757-2_4. ISBN 978-1-4419-6756-5.
  6. 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.
  7. Transient Name Server entry for SN 1990B. Retrieved 30 March 2023.
  8. Transient Name Server entry for SN 2004cc. Retrieved 30 March 2023.
  9. "SN 2020fqv". Transient Name Server.
  10. Transient Name Server entry for SN 2023ijd. Retrieved 14 May 2023.
  11. 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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