Pisces VII
| Pisces VII/Triangulum III | |
|---|---|
 Pisces VII/Triangulum III (circled in red), taken by the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Survey (LSI) | |
| Observation data (J2000 epoch) | |
| Constellation | Pisces |
| Right ascension | 01h 21m 40.5s[1] |
| Declination | +26° 23′ 24″[1] |
| Distance | 1,050 kpc (3.4 Mly)[1] |
| Apparent magnitude (V) | 13.6 ± 2[1] |
| Absolute magnitude (V) | -6.1 ± 2[1] |
| Surface brightness | 2.2+0.5 −0.7×104 L☉[1] |
| Characteristics | |
| Mass | (2.0±0.1)×104[2] M☉ |
| Half-light radius (physical) | 119 ± 48 parsecs |
Pisces VII (Psc VII), or Triangulum III (Tri III), is an ultra-faint dwarf galaxy and a possible satellite of the Triangulum Galaxy (Messier 33 or NGC 598). It is likely a small elliptical or irregular galaxy, and is one of the faintest objects within the Local Group, with an apparent magnitude of only 13.6. It was first reported in 2020 by amateur astronomer Giuseppe Donatiello during a review of an astronomical survey, and was later confirmed by the Italian Galileo National Telescope, therefore making it first galaxy within the Local Group to have been discovered by an amateur astronomer.[1]
Discovery
[edit]Giuseppe Donatiello discovered Pisces VII in 2020 while analyzing the Dark Energy Camera Legacy Survey (DECaLS), a public astronomy survey conducted by the Cerro Tololo Inter-American Observatory using the Blanco 4m telescope.[3][4] He reported it after identifying an unresolved over-density of stellar mass within the Pisces constellation;[1][2] it was later confirmed by the Galileo National Telescope, making it the first Local Group object to have been discovered by an amateur astronomer.[5][6]
Nomenclature
[edit]Pisces VII or Triangulum III received both names from its location in the night sky; Pisces VII is derived from the galaxy's namesake constellation, Pisces, and is abbreviated as "Psc VII";[1] and Triangulum III, from its status as a suspected, unconfirmed satellite galaxy of Triangulum.[2]
Characteristics
[edit]Pisces VII is a small elliptical or irregular galaxy which is primarily composed of smaller, old red-dwarf stars, with a small population of younger blue giants; this has contributed to Pisces VII's unusually high apparent magnitude of 13.6±2, in spite of its relatively close proximity to Earth, and makes it one of the faintest objects within the Local Group at a solar luminosity of only 2.2×104 L☉, and an absolute magnitude of −6.1±2.[1][2] It orbits 97 ± 6 kiloparsecs (316,372 ± 341.56 light years) away from Triangulum's galactic center, lying primarily within the galaxy's dark-matter halo.[1]
Due to the slightly warped structure of Triangulum, it is theorized that it made a close flyby with the Andromeda Galaxy within the past few billion years,[7] and thus it is likely that much of the matter of Pisces VII was tidally stripped and pulled into Andromeda, leaving a much dimmer, fainter structure.[3]
Observation
[edit]
Pisces VII is visible in the namesake constellation of Pisces at a right ascension of 20h 25m 8.4s and a declination of 26° 23′ 27.6″, in the J2000 epoch.[3] Due to its high magnitude, it cannot be seen with the naked human eye, and is extremely difficult to resolve and observe with amateur telescopes.[2]
See also
[edit]- Giuseppe Donatiello
- List of Triangulum's suspected satellite galaxies
- Magellanic Clouds, dwarf satellite galaxies of the Milky Way
- Pisces II, dwarf satellite galaxy of the Milky Way
References
[edit]- ^ a b c d e f g h i j k Collins, Michelle L. M.; Martinez-Delgado, David; Monelli, Matteo; Tollerud, Erik J.; Donatiello, Giuseppe; Navabi, Mahdieh; Charles, Emily; Boschin, Walter (18 January 2024). "Pisces VII/Triangulum III – M33's second dwarf satellite galaxy". Monthly Notices of the Royal Astronomical Society. 528 (2): 2614–2620. doi:10.1093/mnras/stae199 – via Oxford Academic.
- ^ a b c d e Martínez-Delgado, David; Karim, Noushin; Charles, Emily J.E.; Boschin, Walter; Monelli, Matteo; Collins, Michelle L.M.; Donatiello, Giuseppe; Alfaro, Emilio J. (5 October 2021). "Pisces VII: discovery of a possible satellite of Messier 33 in the DESI legacy imaging surveys". Monthly Notices of the Royal Astronomical Society. 509 (1): 16–24. doi:10.1093/mnras/stab2797 – via Oxford Academic.
- ^ a b c Luciani 0, Massimo (21 November 2021). "Pisces VII is an ultra-faint dwarf galaxy whose discovery could be important in cosmological studies". Retrieved 21 April 2026.
{{cite web}}: CS1 maint: numeric names: authors list (link) - ^ Survey, Legacy (8 November 2012). "The Dark Energy Camera Legacy Survey (DECaLS)". Legacy Survey. Retrieved 21 April 2026.
- ^ "Astronomical object found by amateur identified as new dwarf galaxy". University Of Surray. 17 November 2021. Retrieved 21 April 2026.
- ^ Lazaro, Enrico de (18 November 2021). "Amateur Astronomer Discovers New Dwarf Galaxy | Sci.News". Sci.News: Breaking Science News. Retrieved 21 April 2026.
- ^ Tepper-García, Thor; Bland-Hawthorn, Joss; Li, Di (21 April 2020). "The M31/M33 tidal interaction: a hydrodynamic simulation of the extended gas distribution". Monthly Notices of the Royal Astronomical Society. 493 (4): 5636–5647. arXiv:1911.11911. doi:10.1093/mnras/staa317. ISSN 0035-8711.
| Location | Triangulum Galaxy → Triangulum subgroup → Local Group → Local Sheet → Local Volume → Virgo Supercluster → Laniakea Supercluster → Pisces–Cetus Supercluster Complex → Local Hole → Observable universe → Universe Each arrow (→) may be read as "within" or "part of". |  |
|---|---|---|
| H II regions | ||
| Suspected satellite galaxies | ||
| Catalogued stars | ||
| Other | ||