Hoag's Object
Hoag's Object | |
---|---|
Serpens Caput | |
Right ascension | 15h 17m 14.4s[1] |
Declination | +21° 35′ 08″[1] |
Redshift | 12740±50 km/s[1][2] |
Distance | 612.8±9.4 Mly (187.9±2.9 Mpc)[2][a] |
Apparent magnitude (B) | 16.2[1] |
Characteristics | |
Type | (RP)E0 or (RP)SA0/a[3] |
Size | 121±4 kly in diameter[2] |
Apparent size (V) | 0.28′ × 0.28′[1] |
Notable features | Ring galaxy |
Other designations | |
PGC 54559,[1] PRC D-51[1] |
Hoag's Object is an unusual
Characteristics
A nearly perfect ring of young hot blue
The gap separating the two stellar populations may contain some star clusters that are almost too faint to see. Though ring galaxies are rare, another more distant ring galaxy (SDSS J151713.93+213516.8)[11] can be seen through Hoag's Object, between the nucleus and the outer ring of the galaxy, at roughly the one o'clock position in the image shown here.
Noah Brosch and colleagues showed that the luminous ring lies at the inner edge of a much larger neutral hydrogen ring.[7]
History and formation
Even though Hoag's Object was clearly shown on the
In the initial announcement of his discovery, Hoag proposed the hypothesis that the visible ring was a product of
Many of the galaxy's details remain mysterious, foremost of which is how it formed. So-called "classic" ring galaxies are generally formed by the collision of a small galaxy with a larger disk-shaped galaxy, producing a density wave in the disk that leads to a characteristic ring-like appearance. Such an event would have happened at least 2–3 billion years ago,[12] and may have resembled the processes that form polar-ring galaxies. However, there is no sign of any second galaxy that would have acted as the "bullet", and the likely older core of Hoag's Object has a very low velocity relative to the ring, making the typical formation hypothesis quite unlikely.[12] Observations with one of the most sensitive telescopes have also failed to uncover any faint galaxy fragments that should be observable in a collision scenario. However, a team of scientists that analyzes the galaxy admits that "if the carnage happened more than 3 billion years ago, there might not be any detritus left to see."[13]
Noah Brosch suggested that Hoag's Object might be a product of an extreme "bar instability" that occurred a few billion years ago in a
A few other galaxies share the primary characteristics of Hoag's Object, including a bright detached ring of stars, but their centers are elongated or barred, and they may exhibit some spiral structure. While none matches Hoag's Object in symmetry, these galaxies are known to some as Hoag-type galaxies.[15][16]
See also
Notes
References
- ^ a b c d e f g "NED results for Hoag's Object". NASA/IPAC Extragalactic Database. Retrieved 2016-06-28.
- ^ a b c d e f
R.W. O'Connell; J.D. Scargle; W.L.W. Sargent (1974). "The Nature of Hoag's Object". doi:10.1086/152940.
- .
- ^ Specktor, Brandon (3 December 2019). "Hoag's Object Is a Galaxy Within a Galaxy Within a Galaxy (and Nobody Knows Why)". Live Science. Retrieved 3 December 2019.
- doi:10.1086/106427.
- ^ "A galactic doughnut". Cosmos Magazine. Retrieved 2019-10-31.
- ^ a b N. Brosch; I. Finkelman; T. Oosterloo; G. Jozsa; A. Moiseev (2013). "HI in HO: Hoag's Object revisited". .
- doi:10.1086/165562.
- TheGuardian.com. 7 March 2019.
- ^ "What Does the Milky Way Weigh? Hubble and Gaia Investigate". 6 March 2019.
- ^ "SkyServer Object Explorer – SDSS J151713.93+213516.8".
- ^ a b c d
F. Schweizer; W.K. Ford Jr.; R. Jederzejewski; R. Giovanelli (1987). "The structure and evolution of Hoag's object". doi:10.1086/165562.
- ^ "Astrophile: Saturn-lookalike galaxy has a murky past". www.newscientist.com. Retrieved 2019-10-31.
- ^
N. Brosch (1985). "The nature of Hoag's object – The perfect ringed galaxy". Bibcode:1985A&A...153..199B.
- ^ at 10:26, Gavin Clarke (2017-01-04). "Astroboffins glimpse sighting of ultra-rare circular galaxy". www.theregister.co.uk. Retrieved 2019-10-31.
{{cite web}}
: CS1 maint: numeric names: authors list (link) - ^ Bob Berman (2015-11-13). "Weird Object: Hoags Object". Astronomy.com. Retrieved 2019-10-31.
External links
- Media related to Hoag's Object at Wikimedia Commons
- Hubble Space Telescope image of Hoag's Object.
- Accretion Rings Galactic Rings – Fund. Cosmic Physics, 1996. Vol. 17, pp. 95–281
- A Wheel within a Wheel (09/05/2002) News Release Number: STScI-2002-21 – HubbleSite
- ESA/Hubble image of Hoag's Object
- Hoag's Object on