Mrk 501
| Markarian 501 | |
|---|---|
2MASS image of Markarian 501
|
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| Observation data (J2000 epoch) | |
| Constellation | Hercules |
| Right ascension | 16h 53m 52.21s |
| Declination | 39° 45′ 37.6″ |
| Redshift | 9915±25 km/s or 0.033640 Z |
| Distance | 456 Mly (140 Mpc) 4.32x1024m |
| Group or cluster | zw1707.6+4045 |
| Characteristics | |
| Type | S0 |
| Apparent size (V) | 94.86" × 71.1" |
| Notable features | brightest object in very-high-energy gamma rays |
| Other designations | |
| 4C39.49 | |
Markarian 501 (or Mrk 501) is a galaxy with a spectrum extending to the highest energy gamma rays. It is a blazar or BL Lac object, which is an active galactic nucleus with a jet that is shooting towards the Earth.
In the very-high-energy gamma ray region of the spectrum, at energies above 1011 eV (0.1 TeV), it is the brightest object in the sky. The object has a redshift of z = 0.034.
The galaxy hosting the blazar was studied and catalogued by Benjamin Markarian in 1974. It was first determined to be a very high energy gamma ray emitter in 1996 by J. Quinn at the Whipple Observatory.
The elliptical galaxy is located in the constellation of Hercules at right ascension 16h 53.9m and declination +39° 45'. Its visible size appears to be 1.2 by 1 minute of arc.
The gamma rays from Mrk 501 are extremely variable, undergoing violent outbursts. The gamma ray spectrum of Mrk 501 shows two humps. One is below 1 keV and can be considered to be X rays and the other is above 1 Tev. During flares and outbursts the peaks increase in power and frequency. Flares lasting 20 minutes long with rise times of 1 minute have been measured by MAGIC. In these flares the higher energy gamma rays (of 1.2 Tev) were delayed 4 minutes over the 0.25 TeV gamma rays. This delay has led to various theories, including that space is bigger at small dimensions with a foamy quantum texture. The foam would create a variation in the speed of light for higher-energy light gamma-rays and the lower-energy radio waves and visible light. Such a variation would contradict Lorentz invariance, but could provide a clue for unification theory. Observations of Dr. Floyd Stecker of NASA's Goddard Space Flight Center of Mrk 501 and Mrk 421 demonstrated that there is no violation of Lorentz invariance. The galaxy is also variable in visible light between magnitude 14.5 and 13.6.
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