NGC 4151
Encyclopedia
NGC 4151 is an intermediate spiral
Seyfert galaxy
located 43 million light years from Earth
in the constellation Canes Venatici
, discovered by Frederick William Herschel on March 17, 1787. It is one of the nearest galaxies to Earth to contain an actively-growing supermassive black hole
.
.
HEAO 1 detected an X-ray source of NGC 4151 at 1H 1210+393, which is outside the Uhuru
error box.
A BL Lac object
observed with the Einstein Observatory
(1E catalog) within NGC 4151 is at 1E 1207.9+3945. ROSAT
detected the bright X-ray source in the NGC 4151 (20 Mpc) field: 1E 1207.9+3945 at RA
(2000) Dec
(2000) .
NGC 4151 is an X-ray landmark of the celestial sphere
.
To explain the X-ray emission two different possibilities have been proposed:
Ursa Major
(UMa).
Intermediate spiral galaxy
An intermediate spiral galaxy is a galaxy that is in between the classifications of a barred spiral galaxy and an unbarred spiral galaxy. It is designated as SAB in the galaxy morphological classification scheme.-Grades:...
Seyfert galaxy
Seyfert galaxy
Seyfert galaxies are a class of galaxies with nuclei that produce spectral line emission from highly ionized gas, named after Carl Keenan Seyfert, the astronomer who first identified the class in 1943...
located 43 million light years from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
in the constellation Canes Venatici
Canes Venatici
Canes Venatici is one of the 88 official modern constellations. It is a small northern constellation that was created by Johannes Hevelius in the 17th century. Its name is Latin for "hunting dogs", and the constellation is often depicted in illustrations as representing the dogs of Boötes the...
, discovered by Frederick William Herschel on March 17, 1787. It is one of the nearest galaxies to Earth to contain an actively-growing supermassive black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
.
X-ray source
X-ray emission from NGC 4151 was apparently first detected on December 24, 1970, with the X-ray observatory satellite UhuruUhuru (satellite)
Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy. It was also known as the X-ray Explorer Satellite, SAS-A , SAS 1, or Explorer 42.The observatory was launched on 12 December 1970 into an initial orbit of about 560 km apogee, 520 km...
.
HEAO 1 detected an X-ray source of NGC 4151 at 1H 1210+393, which is outside the Uhuru
Uhuru (satellite)
Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy. It was also known as the X-ray Explorer Satellite, SAS-A , SAS 1, or Explorer 42.The observatory was launched on 12 December 1970 into an initial orbit of about 560 km apogee, 520 km...
error box.
A BL Lac object
BL Lac object
A BL Lacertae object or BL Lac object is a type of active galaxy with an active galactic nucleus and is named after its prototype, BL Lacertae. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical...
observed with the Einstein Observatory
Einstein Observatory
Einstein Observatory was the first fully imaging X-ray telescope put into space and the second of NASA's three High Energy Astrophysical Observatories...
(1E catalog) within NGC 4151 is at 1E 1207.9+3945. ROSAT
ROSAT
ROSAT was a German Aerospace Center-led satellite X-ray telescope, with instruments built by Germany, the UK and the US...
detected the bright X-ray source in the NGC 4151 (20 Mpc) field: 1E 1207.9+3945 at RA
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...
(2000) Dec
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
(2000) .
NGC 4151 is an X-ray landmark of the celestial sphere
Celestial sphere
In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with the Earth and rotating upon the same axis. All objects in the sky can be thought of as projected upon the celestial sphere. Projected upward from Earth's equator and poles are the...
.
To explain the X-ray emission two different possibilities have been proposed:
- radiation of material falling onto the central black hole (which was growing much more quickly about 25,000 years ago) was so bright that it stripped electronElectronThe electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s away from the atomAtomThe atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s in the gas in its path, and then electrons recombined with these ionized atoms - the energy released by material flowing into the black hole in an accretion disk created a vigorous outflow of gas from the surface of the disk, which directly heated gas in its path to X-ray emitting temperatures
X-ray intensity
The X-ray luminosity (Lx) of the initial detection of an X-ray source (2U 1207+39) was ~1.1 x 1042 ergs/s (at a distance of 13 Mpc).X-ray source location
The X-ray source parallelogram (error box) for 2U 1207+39 stretches from ~1136+392 to ~1212+396. Most of the error box is in the constellationConstellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Ursa Major
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...
(UMa).
See also
- X-ray astronomyX-ray astronomyX-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and...
- Searching for the first X-ray source per constellation
- List of the first X-ray source in a constellation
- X-1 X-ray source