deepskytraveler
November 21st, 2018, 04:31 AM
Object of the Week November 18, 2018 – NGC 1291 Snow Collar Galaxy
NGC 1291, NGC 1269, PGC 12209, MCG-7-7-8
Type: Barred Lenticular Galaxy (R)SB(s)0/a
Constellation: Eridanus
RA: 3h 17m 59s
Dec: -41° 02’ 50”
Size: 11.2’ x 59.9’
Mag(v): 8.45
A recent letter published on October 18, 2018 in the Monthly Notices of the Royal Astronomical Society caught my attention. It announced the discovery by researchers at the Instituto de Astrofìscia de Canarias of the first peanut-shaped structure detected in the inner bar of a double-barred galaxy. Structures of this type previously detected only in outer, or single, bars are useful tracers of the evolution of galaxies.
The galaxy where this discovery was made is NGC 1291, also known as NGC 1269. It is a ring galaxy with an unusual inner bar and outer ring structure located about 28 million light-years away in the constellation Eridanus. It was discovered by James Dunlop in 1826 and subsequently entered into the New General Catalogue as NGC 1291 by Johan Ludvig Emil Dreyer. John Herschel then observed the same object in 1836 and entered it into the catalog as NGC 1269 without realizing it was a duplicate.
Dunlop wrote this description of NGC 1291 as seen through a 9-inch reflector: “A pretty bright round nebula, about 1 ½‘ diameter, very bright and condensed to the centre, and very faint at the merging with a very [faint] star about 1’ north, but north, but not involved.” Interestingly, when John Herschel observed this object from the Cape of Good Hope he referred to it as a globular cluster. He wrote: “Globular cluster, very bright, pretty large with a much brighter middle (h2521 = h2518 = NGC 2169).”
In 1975 de Vacouleurs described a rarity in the center of NGC 1291. He detected, for the first time, an inner bar which follows the same lens-bar-nucleus pattern of the outer bar. Nowadays we know that bars within bars are not an oddity, with recent observations suggesting that ~30 percent of all barred galaxies host an inner bar. The importance of inner bars is not restricted to their high incidence. In particular, they are thought to be an efficient mechanism for transporting gas to the galaxy central regions, possibly fueling active galactic nuclei and affecting the formation of new stellar structures.
Today we know that NGC 1291 to be a special type of galaxy – one whose morphology is intermediate between a pure lenticular system, which does not show any spiral structure, and an early type spiral with a large central region. In long exposure photographs, the galaxy displays a fairly large nucleus on a weak bar that marks the major axis of a little, elongated, bright lens; a faint outer ring emerges from two very weak spiral arms or arcs. A more detailed view reveals it to have an outer ring, lens and bar, a secondary lens and bar, and a nucleus.
3258
Ultraviolet image (left) and visual image (right) of the barred ring galaxy NGC 1291. The visual image is dominated by the inner disk and bar. The ultraviolet image is dominated by the low surface brightness outer arms.
With a declination of -41°, NGC 1291 is not an easy target for those of us in the mid-northern latitudes. Here in the Chicago area the galaxy culminates at an altitude of only ~7° - so your best bet may be to head South!
Stephen James O’Meara describes NGC 1291 in a 4-inch as “[showing] a sharp inner core surrounded by a bright elliptical lens, which is itself wrapped in a circular halo of faint light.” When bumping the power up from 23x to 41x “NGC 1291 looks more like a planetary nebula than a galaxy, which is interesting if you consider that the NGC lists it as a globular cluster. But the reason for the NGC description becomes obvious when the galaxy is studied at high powers. That’s when several dim stars or knots can be seen superimposed on this globular glow. At 101x in the 4-inch, the star-like core sites inside a circular annulus of bright light, which is surrounded by a large diffuse lens. Both the inner ring and lens appear mottled.”
O’Meara nicknames NGC 1291 the Snow Collar Galaxy after a phenomenon described by Italian astronomer Angelo Secchi (1818-1878). While observing M57, the Ring Nebula in Lyra, Seechi believe he resolved the ring into minute stars “glittering like stardust.” In the case of NGC 1291, however, the phenomenon is most likely due to the fact that dim field stars pepper the face of the galaxy. It’s more like looking at snowflakes falling on a fur collar; as soon as one snowflake lands, it is quickly replaced with yet another snowflake.
Now it’s your turn to observe this fascinating galaxy.
Give it a go and let us know!
NGC 1291, NGC 1269, PGC 12209, MCG-7-7-8
Type: Barred Lenticular Galaxy (R)SB(s)0/a
Constellation: Eridanus
RA: 3h 17m 59s
Dec: -41° 02’ 50”
Size: 11.2’ x 59.9’
Mag(v): 8.45
A recent letter published on October 18, 2018 in the Monthly Notices of the Royal Astronomical Society caught my attention. It announced the discovery by researchers at the Instituto de Astrofìscia de Canarias of the first peanut-shaped structure detected in the inner bar of a double-barred galaxy. Structures of this type previously detected only in outer, or single, bars are useful tracers of the evolution of galaxies.
The galaxy where this discovery was made is NGC 1291, also known as NGC 1269. It is a ring galaxy with an unusual inner bar and outer ring structure located about 28 million light-years away in the constellation Eridanus. It was discovered by James Dunlop in 1826 and subsequently entered into the New General Catalogue as NGC 1291 by Johan Ludvig Emil Dreyer. John Herschel then observed the same object in 1836 and entered it into the catalog as NGC 1269 without realizing it was a duplicate.
Dunlop wrote this description of NGC 1291 as seen through a 9-inch reflector: “A pretty bright round nebula, about 1 ½‘ diameter, very bright and condensed to the centre, and very faint at the merging with a very [faint] star about 1’ north, but north, but not involved.” Interestingly, when John Herschel observed this object from the Cape of Good Hope he referred to it as a globular cluster. He wrote: “Globular cluster, very bright, pretty large with a much brighter middle (h2521 = h2518 = NGC 2169).”
In 1975 de Vacouleurs described a rarity in the center of NGC 1291. He detected, for the first time, an inner bar which follows the same lens-bar-nucleus pattern of the outer bar. Nowadays we know that bars within bars are not an oddity, with recent observations suggesting that ~30 percent of all barred galaxies host an inner bar. The importance of inner bars is not restricted to their high incidence. In particular, they are thought to be an efficient mechanism for transporting gas to the galaxy central regions, possibly fueling active galactic nuclei and affecting the formation of new stellar structures.
Today we know that NGC 1291 to be a special type of galaxy – one whose morphology is intermediate between a pure lenticular system, which does not show any spiral structure, and an early type spiral with a large central region. In long exposure photographs, the galaxy displays a fairly large nucleus on a weak bar that marks the major axis of a little, elongated, bright lens; a faint outer ring emerges from two very weak spiral arms or arcs. A more detailed view reveals it to have an outer ring, lens and bar, a secondary lens and bar, and a nucleus.
3258
Ultraviolet image (left) and visual image (right) of the barred ring galaxy NGC 1291. The visual image is dominated by the inner disk and bar. The ultraviolet image is dominated by the low surface brightness outer arms.
With a declination of -41°, NGC 1291 is not an easy target for those of us in the mid-northern latitudes. Here in the Chicago area the galaxy culminates at an altitude of only ~7° - so your best bet may be to head South!
Stephen James O’Meara describes NGC 1291 in a 4-inch as “[showing] a sharp inner core surrounded by a bright elliptical lens, which is itself wrapped in a circular halo of faint light.” When bumping the power up from 23x to 41x “NGC 1291 looks more like a planetary nebula than a galaxy, which is interesting if you consider that the NGC lists it as a globular cluster. But the reason for the NGC description becomes obvious when the galaxy is studied at high powers. That’s when several dim stars or knots can be seen superimposed on this globular glow. At 101x in the 4-inch, the star-like core sites inside a circular annulus of bright light, which is surrounded by a large diffuse lens. Both the inner ring and lens appear mottled.”
O’Meara nicknames NGC 1291 the Snow Collar Galaxy after a phenomenon described by Italian astronomer Angelo Secchi (1818-1878). While observing M57, the Ring Nebula in Lyra, Seechi believe he resolved the ring into minute stars “glittering like stardust.” In the case of NGC 1291, however, the phenomenon is most likely due to the fact that dim field stars pepper the face of the galaxy. It’s more like looking at snowflakes falling on a fur collar; as soon as one snowflake lands, it is quickly replaced with yet another snowflake.
Now it’s your turn to observe this fascinating galaxy.
Give it a go and let us know!