NGC 4567 and NGC 4568 (nicknamed the ''Butterfly Galaxies'' or ''Siamese Twins'') are a set of

unbarred spiral galaxies A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about two thirds of all spiral galaxies, and generally affect both the motions of stars and interstellar gas within spiral galaxies ...

about 60 million

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Virgo Virgo may refer to: *Virgo (astrology), the sixth astrological sign of the zodiac *Virgo (constellation), a constellation *Virgo Cluster, a cluster of galaxies in the constellation Virgo *Virgo Stellar Stream, remains of a dwarf galaxy *Virgo Supe ...

. They were both discovered by

William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline H ...

in 1784. They are part of the

Virgo Cluster The Virgo Cluster is a large cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo. Comprising approximately 1,300 (and possibly up to 2,000) member galaxies, the cluster forms the heart of the lar ...

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

. These galaxies are in the process of colliding and merging with each other, as studies of their distributions of

neutral Neutral or neutrality may refer to: Mathematics and natural science Biology * Neutral organisms, in ecology, those that obey the unified neutral theory of biodiversity Chemistry and physics * Neutralization (chemistry), a chemical reaction in ...

and molecular

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

show, with the highest star-formation activity in the part where they overlap. However, the system is still in an early phase of interaction. Four

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

e have been observed in the Butterfly Galaxies: SN 1990B ( type Ib, mag. 16), SN 2004cc (type Ic, mag. 17.5), SN 2020fqv (

type IIb In theoretical physics, type II string theory is a unified term that includes both type IIA strings and type IIB strings theories. Type II string theory accounts for two of the five consistent superstring theory, superstring theories in ten dimens ...

, mag. 19), and SN 2023ijd (type II, mag. 16.8).

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 Institutional discrimination is discriminatory treatment of an individual or group of individuals by society or institutions, through unequal consideration of members of subordinate groups. These unfair and indirect methods of discrimination are o ...

in their terminology.

Notes

References

External links

* Kopernik Space Images
Spiral Galaxies NGC 4568 and NGC 4567 aka "The Siamese Twins" : Supernova 2004cc
George Normandin (29 June 2004) * Skyhound

* SIMBAD
VCC 1673 : NGC 4567 -- Galaxy in Pair of Galaxies
* SIMBAD
VCC 1676 : NGC 4568 -- Galaxy in Pair of Galaxies
* NED
VV 219
* NED
NGC 4567
* NED
NGC 4568
Virgo (constellation) Virgo Cluster 4567 42064 Interacting galaxies Unbarred spiral galaxies Overlapping galaxies {{Spiral-galaxy-stub

Naming controversy

See also

Notes

References

External links