NGC 6365 is a pair of spiral galaxies in the constellation

Draco Draco is the Latin word for serpent or dragon. Draco or Drako may also refer to: People * Draco (lawgiver) (from Greek: Δράκων; 7th century BC), the first lawgiver of ancient Athens, Greece, from whom the term ''draconian'' is derived * D ...

. It consists of two galaxies, PGC 60174 to the south, and PGC 60171 to the north. These two galaxies are also designated respectively by the NASA/IPAC database as NGC 6365A and NGC 6365B. This pair of galaxies was discovered by German astronomer

Lewis Swift Lewis A. Swift (February 29, 1820 – January 5, 1913) was an American astronomer who discovered 13 comets and 1,248 previously uncatalogued nebulae. Only William Herschel discovered more nebulae visually. Discoveries Swift discovered or co-discov ...

in 1884.

NGC 6563A

NGC 6563A is the northern counterpart of NGC 6563, and is a

barred spiral galaxy 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 galaxi ...

. Its coordinates are 17h 22m 43.8s and 62° 09 57.9. Its speed relative to the

cosmic microwave background In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...

is 8,413 ± 4 km/s, which corresponds to a Hubble distance of 124.1 ± 8.7 Mpc (~405 million ly). The luminosity class of NGC 6365A is III-IV and it has a broad HI line. It is an

active galaxy An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not prod ...

(AGN) of type Seyfert 2. With a

surface brightness In astronomy, surface brightness (SB) quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background. An object's surface brightness depends on its ...

equal to 14.00 mag/am^2, we can qualify NGC 6365A as a

low surface brightness galaxy A low-surface-brightness galaxy, or LSB galaxy, is a diffuse galaxy with a surface brightness that, when viewed from Earth, is at least one magnitude lower than the ambient night sky. Most LSBs are dwarf galaxies, and most of their baryonic mat ...

(LSB). LSB galaxies are

diffuse Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...

(D) galaxies with a surface brightness less than one magnitude lower than that of the ambient night sky. To date, nearly fifteen measurements not based on redshift give a distance of 111.469 ± 31.088 Mpc (~364 million ly), which is within the values of the Hubble distance.

Supernova

The

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 ...

SN 2003U was discovered in NGC 6365A on January 27, 2003, by Scottish astronomer

Tom Boles Thomas Boles (born 1944 in Lennoxtown in Scotland) is a Scottish amateur astronomer, discoverer of astronomical objects, author, broadcaster and former communications and computer engineer, who observes from his private "Coddenham Observatory" ( ...

. This supernova was of type Ia.

NGC 6563B

NGC is the southern counterpart of NGC 6563, and is a spiral galaxy. However, the NASA/IPAC database indicates that it is Magellanic in type. Its coordinates are 17h 22m 43.5s and 62° 10 25.4. Its speed relative to the cosmic microwave background is 7,975 ± 4 km/s, which corresponds to a Hubble distance of 117.6 ± 8.2 Mpc (~384 million ly). The luminosity class of NGC 6365B is IV-V and it has a broad HI line. It also contains regions of ionized hydrogen.

Galaxy interaction

The pair of galaxies that make up NGC 6563 appear in

Halton Arp Halton Christian "Chip" Arp (March 21, 1927 – December 28, 2013) was an American astronomer. He was known for his 1966 ''Atlas of Peculiar Galaxies'', which (it was later theorized) catalogues many examples of interacting and merging galaxie ...

's ''Atlas of Peculiar Galaxies'' under the designation Arp 30. Arp describes NGC 6365 as a spiral galaxy with an overdeveloped arm, but this has been recently confirmed by astronomers to be false. In the image used by Arp, PGC 60171 (NGC 6365B) appears to be part of PGC 60174 and to be one galaxy. But, they are actually two separate galaxies. According to redshift-based measurements, NGC 6365A is the most distant galaxy. However, given the uncertainties in the measurements, NGC 6365B could be the most distant galaxy. The image taken by the telescope at the Mount Lemmon observatory does not allow us to decide. There is no publication that is only speculative about their position and also about their interaction.

External links

NGC 6563
at

SIMBAD SIMBAD (the Set of Identifications, Measurements and Bibliography for Astronomical Data) is an astronomical database of objects beyond the Solar System. It is maintained by the Centre de données astronomiques de Strasbourg (CDS), France. SIMBA ...

References