NGC 5585 is a
spiral galaxy
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''[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 from Earth in the constellation of
Ursa Major
Ursa Major (; also known as the Great Bear) is a constellation in the northern sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater (or larger) bear," referring to and contrasting it with nearby Ursa ...
; it is a member of the
M101 Group of galaxies. The galaxy has a diameter of about 35,000 light-years and has a very diffuse disc with almost no central bulge. Although its overall structure is quite complex, the galaxy does have a very faint
spiral arm
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''[galaxy morphological classification
Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance. There are several schemes in use by which galaxies can be classified according to their morphologies, the most fa ...]
of SAB(s)d.
Like other galaxies with a similar type, NGC 5585 exhibits a moderate level of
that is mostly concentrated in the central region. To date, 47 distinct regions of star formation have been identified. Despite this, the galaxy's visible components appear to form only a tiny fraction of the total mass present as the gravity of the visible portion of the disc does not explain the observed
rotation curve
The rotation curve of a disc galaxy (also called a velocity curve) is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre. It is typically rendered graphically as a plot, and ...
even extremely close to the center. This suggests that NGC 5585 has a very large
dark matter
Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...
component that is more reflective of what is normally seen in
dwarf galaxies
A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is s ...
than a galaxy of this size. Even the gravity of the galaxy's
H I region
An HI region or H I region (read ''H one'') is a cloud in the interstellar medium composed of neutral atomic hydrogen (HI), in addition to the local abundance of helium and other elements. (H is the chemical symbol for hydrogen, and "I" is the Ro ...
s appears to have more impact than the visible components of the galaxy.
A total of five
supernova remnant
A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar mat ...
s (SNRs) have been observed in NGC 5585. One of the SNRs is extremely large with dimensions of about 200 x 90
parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...
s (650 x 300 ly) and its
x-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
emissions are so powerful that it actually distorted the initial x-ray emission contour map for the entire galaxy that was obtained by the
Einstein Observatory
Einstein Observatory (HEAO-2) was the first fully imaging X-ray telescope put into space and the second of NASA's three High Energy Astrophysical Observatories. Named HEAO B before launch, the observatory's name was changed to honor Albert E ...
in the early 1980s. The SNR's large size and the fact that it is still expanding at an abnormally high rate of more than suggest that it is probably located in a low-density area of NGC 5585's
interstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
.
A 1997 paper estimated that the galaxy probably has about one
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 ...
every 1,000 years.
Gallery
File:NGC5585 - SDSS DR14 (panorama).jpg, NGC 5585 by the Sloan Digital Sky Survey
The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 a ...
File:Ngc5585-hst-814-606.jpg, 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 ...
image of NGC 5585
References
External links
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{{Ngc60
Intermediate spiral galaxies
M101 Group
Ursa Major (constellation)
5585
09179
51210
+10-20-094
14182+5657