Unbarred lenticular galaxy

An unbarred lenticular galaxy is a lenticular version of an unbarred spiral galaxy. They have the Hubble type of SA0.

An example of this is the Galaxy AM 0644-741. For other examples see Category:Unbarred lenticular galaxies.

AM 0644-741
An example of this type, imaged by the Hubble Space Telescope

See also

AM 0644-741

AM 0644-741, also known as the Lindsay-Shapley Ring, is an unbarred lenticular galaxy, and a ring galaxy, which is 300 million light-years away in the southern constellation Volans. The yellowish nucleus was once the center of a normal spiral galaxy, and the ring which currently surrounds the center is 150,000 light years in diameter. The ring is theorized to have formed by a collision with another galaxy, which triggered a gravitational disruption that caused dust in the galaxy to condense and form stars, which forced it to then expand away from the galaxy and create a ring. The ring is a region of rampant star formation dominated by young, massive, hot blue stars. The pink regions along the ring are rarefied clouds of glowing hydrogen gas that is fluorescing as it is bombarded with strong ultraviolet light from the blue stars. Galactic simulation models suggest that the ring of AM 0644-741 will continue to expand for about another 300 million years, after which it will begin to disintegrate.

IC 4970

IC 4970 is an unbarred lenticular galaxy of type SA0^- pec: in the constellation Pavo. It is 212 million light-years (65 Mpc) from Earth and is interacting with the barred spiral galaxy NGC 6872. It was discovered on 21 September 1900 by American astronomer DeLisle Stewart.

NGC 5548

NGC 5548 is a Type I Seyfert galaxy with a bright, active nucleus. This activity is caused by matter flowing onto a 65 million solar mass (M☉) supermassive black hole at the core. Morphologically, this is an unbarred lenticular galaxy with tightly-wound spiral arms, while shell and tidal tail features suggest that it has undergone a cosmologically-recent merger or interaction event. NGC 5548 is approximately 245 million light years away and appears in the constellation Boötes. The apparent visual magnitude of NGC 5548 is approximately 13.3 in the V band.In 1943, this galaxy was one of twelve nebulae listed by American astronomer Carl Keenan Seyfert that showed broad emission lines in their nuclei. Members of this class of objects became known as Seyfert galaxies, and they were noted to have a higher than normal surface brightness in their nuclei. Observation of NGC 5548 during the 1960s with radio telescopes showed an enhanced level of radio emission. Spectrograms of the nucleus made in 1966 showed that the energized region was confined to a volume a few parsecs across, where temperature were around 14000 K and the plasma had a dispersion velocity of ±450 km/s.Among astronomers, the accepted explanation for the active nucleus in NGC 5548 is the accretion of matter onto a supermassive black hole (SMBH) at the core. This object is surrounded by an orbiting disk of accreted matter drawn in from the surroundings. As material is drawn into the outer parts of this disk, it becomes photoionized, producing broad emission lines in the optical and ultraviolet bands of the electromagnetic spectrum. A wind of ionized matter, organized in filamentary structures at distances of 1–14 light days from the center, is flowing outward in the direction perpendicular to the accretion disk plane.The mass of the central black hole can be estimated based on the properties of the emission lines in the core region. Combined measurements yield an estimated mass of 6.54+0.26−0.25×107 M☉. In other words, it is some 65 million times the mass of the Sun. This result is consistent with other methods of estimating the mass of the SMBH in the nucleus of NGC 5548. Matter is falling onto this black hole at the estimated rate of 0.03 M☉ per year, whereas mass is flowing outward from the core at or above the rate of 0.92 M☉ each year. The inner part of the accretion disk surrounding the SMBH forms a thick, hot corona spanning several light hours that is emitting X-rays. When this radiation reaches the optically thick part of the accretion disk at a radius of around 1–2 light days, the X-rays are converted into heat.

NGC 5890

NGC 5890 is an unbarred lenticular galaxy in the constellation Libra. It was discovered in April 1785 by Ormond Stone.

NGC 7499

NGC 7499 is an unbarred lenticular galaxy within the constellation Pisces.

NGC 966

NGC 966 is a unbarred lenticular galaxy approximately 440 million light-years away from Earth in the constellation of Cetus. It was discovered by American astronomer Francis Preserved Leavenworth in 1886.

Unbarred spiral galaxy

An unbarred spiral galaxy is a type of spiral galaxy without a central bar, or one that is not a barred spiral galaxy. It is designated with an SA in the galaxy morphological classification scheme.

The Sombrero Galaxy is an unbarred spiral galaxy.

Barless spiral galaxies are one of three general types of spiral galaxies under the de Vaucouleurs system classification system, the other two being intermediate spiral galaxy and barred spiral galaxy. Under the Hubble tuning fork, it is one of two general types of spiral galaxy, the other being barred spirals.

Active nuclei
Energetic galaxies
Low activity
See also

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