NGC 4151 is an intermediate spiral

Seyfert galaxy Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars. They have quasar-like nuclei (very luminous, distant and bright sources of electromagnetic radiation) with very high surface brightnesses whose spectra ...

with weak inner ring structure located from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

in the constellation

Canes Venatici Canes Venatici () is one of the IAU designated constellations, 88 constellations designated by the International Astronomical Union (IAU). It is a small northern constellation that was created by Johannes Hevelius in the 17th century. Its name is ...

. The galaxy was first mentioned 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 March 17, 1787; it was one of the six Seyfert galaxies described in the paper which defined the term. It is one of the nearest galaxies to Earth to contain an actively growing supermassive

black hole A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...

. The black hole would have a mass on the order of 2.5 million to 30 million solar masses. It was speculated that the nucleus may host a binary black hole, with about 40 million and about 10 million solar masses respectively, orbiting with a 15.8-year period. This is, however, still a matter of active debate. Some astronomers nickname it the "

Eye of Sauron Sauron (pronounced ) is the title character and the primary antagonist, through the forging of the One Ring, of J. R. R. Tolkien's ''The Lord of the Rings'', where he rules the land of Mordor and has the ambition of ruling the whole of Middl ...

" from its appearance.

X-ray source

X-ray emission from NGC 4151 was apparently first detected on December 24, 1970, with the X-ray observatory satellite Uhuru, although the observation spanned an error-box of 0.56 square degrees and there is some controversy as to whether UHURU might not have detected the

BL Lac object A BL Lacertae object or BL Lac object is a type of active galactic nucleus (AGN) or a galaxy with such an AGN, named after its prototype, BL Lacertae. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and l ...

1E 1207.9 +3945, which is inside their error box - the later

HEAO 1 HEAO-1 was an X-ray telescope launched in 1977. HEAO-1 surveyed the sky in the X-ray portion of the electromagnetic spectrum (0.2 keV – 10 MeV), providing nearly constant monitoring of X-ray sources near the ecliptic poles and more detailed stu ...

detected an X-ray source of NGC 4151 at 1H 1210+393, coincident with the optical position of the nucleus and outside the error box of Uhuru. 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

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...

s away from the

atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, and ...

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 An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is typically a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other fo ...

created a vigorous outflow of gas from the surface of the disk, which directly heated gas in its path to X-ray emitting temperatures

References

External links

Hubble site news center: Fireworks Near a Black Hole in the Core of Seyfert Galaxy NGC 4151
{{DEFAULTSORT:NGC 4151 Galaxies discovered in 1787 Intermediate spiral galaxies Seyfert galaxies Canes Venatici 4151 07166 38739 X-ray astronomy Astronomical X-ray sources Articles containing video clips 17870317

X-ray source

See also

References

External links