Virgo A

(3C274) An intense radio source in the Virgo cluster that is associated with the galaxy M87. It is 16 megaparsecs distant and has a flux density of 198 jansky at a wavelength of 20 cm. M87 is a giant elliptical galaxy that is unusual in possessing an optical jet extending from its central regions. Jet and nucleus are both sources of nonthermal radio and X-ray radiation due to synchrotron emission from plasma as it is accelerated along the jet. M87 is the nearest active galaxy. Hubble Space Telescope observations of a disk of hot gas in the core of M87 show it to be rotating rapidly, a signature of a supermassive black hole at the center of the galaxy, with a mass more than three billion times greater than that of our Sun.

The thermal X-ray emission in the Virgo cluster is strongly concentrated to the region around M87, and to bind this gas gravitationally the galaxy must have a total mass of more than 10¹³ solar masses. A direct determination of the mass-to-luminosity ratio in this galaxy requires it to have a massive dark halo. The galaxy is surrounded by over a hundred thousand globular clusters.

Virgo A

[′vər·gō ′ā] (astronomy) A radio galaxy; it is associated with the galaxy M 87 (NGC 4486).

单词	virgo a
释义	Virgo A Virgo A (3C274) An intense radio source in the Virgo cluster that is associated with the galaxy M87. It is 16 megaparsecs distant and has a flux density of 198 jansky at a wavelength of 20 cm. M87 is a giant elliptical galaxy that is unusual in possessing an optical jet extending from its central regions. Jet and nucleus are both sources of nonthermal radio and X-ray radiation due to synchrotron emission from plasma as it is accelerated along the jet. M87 is the nearest active galaxy. Hubble Space Telescope observations of a disk of hot gas in the core of M87 show it to be rotating rapidly, a signature of a supermassive black hole at the center of the galaxy, with a mass more than three billion times greater than that of our Sun. The thermal X-ray emission in the Virgo cluster is strongly concentrated to the region around M87, and to bind this gas gravitationally the galaxy must have a total mass of more than 10¹³ solar masses. A direct determination of the mass-to-luminosity ratio in this galaxy requires it to have a massive dark halo. The galaxy is surrounded by over a hundred thousand globular clusters. Virgo A [′vər·gō ′ā] (astronomy) A radio galaxy; it is associated with the galaxy M 87 (NGC 4486).
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