NGC 891 (also known as Caldwell 23, the Silver Sliver Galaxy, and the Outer Limits Galaxy) is an edge-on
unbarred spiral galaxy
An unbarred spiral galaxyAstronomy Pictures(accessed 18 April 2010) 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.
Ba ...
about 30
million
One million (1,000,000), or one thousand thousand, is the natural number following 999,999 and preceding 1,000,001. The word is derived from the early Italian ''millione'' (''milione'' in modern Italian), from ''mille'', "thousand", plus the au ...
light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s away in the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
Andromeda. It was discovered by
William Herschel
Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline H ...
on October 6, 1784.
The galaxy is a member of the
NGC 1023 group
The NGC 1023 group is a group of galaxies about 20.6 million light-years away from Earth. It is a group in the Local Supercluster along with the Local Group.
Members
* Probable (dwarfs): DDO 024, DDO 025.
* Possible members: NGC 672, IC 1 ...
of
galaxies
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...
in the
Local Supercluster
The Virgo Supercluster (Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which itself contains the Milky Way and Andromeda galaxies, as well as others. At leas ...
. It has an
H II
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundred ...
nucleus.
The object is visible in small to moderate size
telescope
A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...
s as a faint elongated smear of light with a
dust lane
A dust lane consists of a relatively dense, obscuring clouds of interstellar dust, observed as a dark swath against the background of a brighter object(s), especially a galaxy. These dust lanes can usually be seen in spiral galaxies, such as ...
visible in larger
aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane.
An opt ...
s.
In 1999, the
Hubble Space Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...
imaged NGC 891 in
infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
.
In 2005, due to its attractiveness and scientific interest, NGC 891 was selected to be the
first light image of the
Large Binocular Telescope
The Large Binocular Telescope (LBT) is an optical telescope for astronomy located on Mount Graham, in the Pinaleno Mountains of southeastern Arizona, United States. It is a part of the Mount Graham International Observatory.
When using both 8 ...
.
In 2012, it was again used as a first light image of the
Lowell Discovery Telescope
The Lowell Discovery Telescope (LDT), formerly the Discovery Channel Telescope (DCT), is a aperture telescope owned and operated by Lowell Observatory. The LDT was built at a dark sky site in the Coconino National Forest near Happy Jack, Arizo ...
with the Large Monolithic Imager.
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 1986J was discovered on August 21, 1986 at apparent magnitude 14.
Properties
NGC 891 looks as the
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
would look like when viewed edge-on (some astronomers have even noted how similar to NGC 891 our galaxy looks as seen from the
Southern Hemisphere[The Milky Way in relation to other galaxies](_blank)
/ref>) and, in fact, both galaxies are considered very similar in terms of luminosity and size; studies of the dynamics of its molecular hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
have also proven the likely presence of a central bar
Bar or BAR may refer to:
Food and drink
* Bar (establishment), selling alcoholic beverages
* Candy bar
* Chocolate bar
Science and technology
* Bar (river morphology), a deposit of sediment
* Bar (tropical cyclone), a layer of cloud
* Bar (u ...
.
Despite this, recent high-resolution images of its dusty disk show unusual filamentary patterns. These patterns are extending into the halo
Halo, halos or haloes usually refer to:
* Halo (optical phenomenon)
* Halo (religious iconography), a ring of light around the image of a head
HALO, halo, halos or haloes may also refer to:
Arts and entertainment Video games
* ''Halo'' (franch ...
of the galaxy, away from its galactic disk
A galactic disc (or galactic disk) is a component of disc galaxies, such as spiral galaxies and lenticular galaxies. Galactic discs consist of a stellar component (composed of most of the galaxy's stars) and a gaseous component (mostly composed ...
. Scientists presume that supernova explosions caused this interstellar dust to be thrown out of the galactic disk toward the halo.
It may also be possible that the light pressure from surrounding stars causes this phenomenon.
The galaxy is a member of a small group of galaxies, sometimes called the NGC 1023 Group
The NGC 1023 group is a group of galaxies about 20.6 million light-years away from Earth. It is a group in the Local Supercluster along with the Local Group.
Members
* Probable (dwarfs): DDO 024, DDO 025.
* Possible members: NGC 672, IC 1 ...
. Other galaxies in this group are the NGCs 925, 949
Year 949 ( CMXLIX) was a common year starting on Monday (link will display the full calendar) of the Julian calendar.
Events
By place
Byzantine Empire
* Arab-Byzantine War: Hamdanid forces under Sayf al-Dawla raid into the theme of Ly ...
, 959
Year 959 ( CMLIX) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar.
Events
By place
Byzantine Empire
* April - May – The Byzantines refuse to pay the yearly tribute. A Hungari ...
, 1003, 1023, and 1058, and the UGCs 1807, 1865 (DDO 19), 2014
File:2014 Events Collage.png, From top left, clockwise: Stocking up supplies and personal protective equipment (PPE) for the Western African Ebola virus epidemic; Citizens examining the ruins after the Chibok schoolgirls kidnapping; Bundles of wat ...
(DDO 22), 2023
Events
Predicted and scheduled events
* January 1
** In the United States, books, films, and other works published in 1927 will enter the public domain, assuming there are no changes made to copyright law.
** Croatia will adopt the eu ...
(DDO 25), 2034 (DDO 24), and 2259. Its outskirts are populated by multiple low-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 it ...
, coherent, and vast substructures, like giant streams that loop around the parent galaxy up to distances of approximately 50 kpc. The bulge and the disk are surrounded by a flat and thick cocoon-like stellar structure. These have vertical and radial distances of up to 15 kpc and 40 kpc, respectively, and are interpreted as the remnant of a satellite galaxy
A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy (also known as the primary galaxy). Satellite galaxies and their constituents are bound ...
disrupted and in the process of being absorbed by NGC 891.
In popular culture
NGC 891 appears alongside M67, the Sombrero Galaxy
The Sombrero Galaxy (also known as Messier Object 104, M104 or NGC 4594) is a peculiar galaxy of unclear classification in the constellation borders of Virgo and Corvus, being about from the Milky Way galaxy. It is a member of the Virgo II Grou ...
, the Pinwheel Galaxy
The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on spiral galaxy away from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who ...
, NGC 5128, NGC 1300
NGC 1300 is a barred spiral galaxy located about 61 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across. It is a member of the Eridanus Cluster, a cluster of 200 galaxies.
It was discovered b ...
, M81, and the Andromeda Galaxy
The Andromeda Galaxy (IPA: ), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about approximately from Earth and the nearest large galaxy to the Milky Way. The gala ...
in the end credits of the Outer Limits TV series, which is why it is occasionally called the Outer Limits Galaxy.
The soundtrack of the 1974 film ''Dark Star'' by John Carpenter
John Howard Carpenter (born January 16, 1948) is an American filmmaker, actor, and composer. Although he worked in various film genres, he is most commonly associated with horror, action, and science fiction films of the 1970s and 1980s. He ...
features a muzak
Muzak is an American brand of background music played in retail stores and other public establishments. The name has been in use since 1934, and has been owned by a division or subsidiary of one or another company ever since. In 1981, Westingho ...
-style instrumental piece called "When Twilight Falls on NGC 891".
The first solo album by Edgar Froese
Edgar Willmar Froese (; 6 June 1944 – 20 January 2015) was a German musical artist and electronic music pioneer, best known for founding the electronic music group Tangerine Dream in 1967. Froese was the only continuous member of the group ...
, ''Aqua
Aqua is the Latin word for water. It is used in many words which relate to water, such as aquatic life. In English, it may also refer to:
Arts
* Aqua (color), a greenish-blue color
Business
* Aqua (skyscraper), an 82-story residential skysc ...
'', also released in 1974, contained a track called "NGC 891". Side 2 of the album, which included this track, was unusual in having been a rare example of a commercially issued piece of music recorded using the '' artificial head'' system.
See also
*Messier 82
Messier 82 (also known as NGC 3034, Cigar Galaxy or M82) is a starburst galaxy approximately 12 million light-years away in the constellation Ursa Major. It is the second-largest member of the M81 Group, with the D25 isophotal diameter of . It ...
References
External links
*
*
APOD:
Interstellar Dust-Bunnies of NGC 891 (9/9/1999)
Information on NGC 891
on Astrophotography by Wolfgang Kloehr
{{DEFAULTSORT:NGC 0891
Unbarred spiral galaxies
Andromeda (constellation)
0891
01831
09031
023b
NGC 1023 Group