Markarian 501

---

title: "Markarian 501" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["discoveries-by-benjamin-markarian", "bl-lacertae-objects", "blazars", "principal-galaxies-catalogue-objects", "markarian-galaxies", "hercules-(constellation)", "radio-galaxies", "4c-objects", "ugc-objects"] description: "Galaxy in the constellation Hercules" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/Markarian_501" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Galaxy in the constellation Hercules ::

::data[format=table title="Infobox galaxy"]

Field	Value
name	Markarian 501
image	SDSS Mrk 501.jpg
caption	Sloan Digital Sky Survey image of Mrk 501
epoch	J2000
type	S0{{cite web
website	MARKARIAN2 – Markarian Galaxies Optical Database
title	Results for Mrk 501
url	http://heasarc.nasa.gov/w3browse/all/markarian2.html
archive-url	https://web.archive.org/web/20100623224554/http://heasarc.nasa.gov/W3Browse/all/markarian2.html
url-status	dead
archive-date	2010-06-23
access-date	2011-12-06 }} Data base query page is at https://web.archive.org/web/20111028222504/http://heasarc.nasa.gov/db-perl/W3Browse/w3table.pl?tablehead=name%3Dmarkarian2&Action=More+Options. Fill in Mrk 501 for name and click start search at bottom of page.
ra
dec
z
h_radial_v
gal_v
dist_ly	152.6 +/-
(Comoving)
{{cvt	465
(Light-travel)
appmag_v
appmag_b
mag_j
mag_h
mag_k
size_v
size	65.28 x
(diameter; 25.0 B-mag arcsec)
69.63 x
(diameter; "total" magnitude)
constellation name	Hercules
notes	Brightest object in very-high-energy gamma rays
group_cluster	zw1707.6+4045
names
::

| name = Markarian 501 | image = SDSS Mrk 501.jpg | caption = Sloan Digital Sky Survey image of Mrk 501 | epoch = J2000 | type = S0{{cite web | website=MARKARIAN2 – Markarian Galaxies Optical Database | title=Results for Mrk 501 | url=http://heasarc.nasa.gov/w3browse/all/markarian2.html | archive-url=https://web.archive.org/web/20100623224554/http://heasarc.nasa.gov/W3Browse/all/markarian2.html | url-status=dead | archive-date=2010-06-23 | access-date=2011-12-06 }} Data base query page is at https://web.archive.org/web/20111028222504/http://heasarc.nasa.gov/db-perl/W3Browse/w3table.pl?tablehead=name%3Dmarkarian2&Action=More+Options. Fill in Mrk 501 for name and click start search at bottom of page. | ra = | dec = | z = | h_radial_v = | gal_v = | dist_ly = 152.6 +/- (Comoving)

465 Gly (Light-travel) | appmag_v = | appmag_b = | mag_j = | mag_h = | mag_k = | size_v = | size = 65.28 x (diameter; 25.0 B-mag arcsec) 69.63 x (diameter; "total" magnitude) | constellation name = Hercules | notes = Brightest object in very-high-energy gamma rays | group_cluster = zw1707.6+4045 | names = Markarian 501 (or Mrk 501) is an elliptical 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. The object has a redshift of z = 0.033.

Mrk 501 is an extremely variable source of gamma rays, undergoing violent outbursts.

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 John Quinn at the Whipple Observatory.{{cite journal |vauthors=Quinn J, Akerlof CW, Biller S, Buckley J, Carter-Lewis DA, Cawley MF, Catanese M, Connaughton V, Fegan DJ, Finley JP, Gaidos J, Hillas AM, Lamb RC, Krennrich F, Lessard R, McEnery JE, Meyer DI, Mohanty G, Rodgers AJ, Rose HJ, Sembroski G, Schubnell MS, Weekes TC, Wilson C, Zweerink J |display-authors=8 |date=10 January 1996 |title=Detection of Gamma Rays with E 300 GeV from Markarian 501 |journal=The Astrophysical Journal Letters |volume=465 |issue=2 |pages=L83–L86 |doi=10.1086/309878 |bibcode = 1996ApJ...456L..83Q |doi-access=free }}

Galaxy

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b3/MRK_0501_2MASS.jpg" caption="Mrk 501 ([[2MASS]])"] ::

The elliptical galaxy is located in the constellation of Hercules at right ascension and declination . Its visible size appears to be 1.2 by 1 minute of arc.

Gamma rays

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. 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.

During the discovery observations flashes at the average rate of one in seven minutes were observed. Cosmic rays (that is, fermionic or massive cosmic rays, as opposed to photons) were ruled out by the shape and size of the flashes which are small and elliptical for gamma rays. The flux for photons over 300 GeV at this point in time in 1995 was 8.1±1.5 x 10−12 cm−2s−1

Black hole

Blazars are likely to originate from matter falling into a black hole and possibly a binary black hole. The velocity dispersion (which is the maximum difference in the velocity toward or away from Earth) observed in the galaxy is 372 km/s which predicts a black hole mass of (0.9 − 3.4) × 109 M⊙. However, dispersion of velocity was also measured as 291 and 270 km/s so the central mass may be less. A 23-day variability suggested that an object may be orbiting the central black hole with a 23-day period.

Jet

With very-long-baseline interferometry, the fine detail of radio waves can be seen down to milliarcsecond (mas) resolution. A central very bright single point called the core is observed. From the core an extremely high-speed blast of plasma emerges in a narrow cone shape as a one-sided jet.

After 30 milliarcseconds, the jet, which is 300 pc long, does a 90° turn and fans out. The inner jet before the kink shows bright edges or a limb-brightened structure less than 10 mas wide. This is probably due to a fast-moving central part to the jet, combined with slower edges.{{cite web |url = http://www.ira.cnr.it/Research/VLBI.html |title = Very Long Baseline Interferometry Research |last = Bondi |first = M. |author2 = L. Feretti |author3 = M. Giroletti |author4 = K.-H. Mack |author5 = F. Mantovani |author6 = C. Stanghellini |author7 = T. Venturi |author8 = D. Dallacasa |author9 = C. Fanti |author10 = R. Fanti |author11 = G. Giovannini |author12 = E. Liuzzo |author13 = M. Orienti |author14 = A. Rossetti |display-authors = 8 |publisher = Instituto di Radioastronomia |access-date = 6 December 2011 |url-status = dead |archive-url = https://web.archive.org/web/20100203210023/http://www.ira.cnr.it/Research/VLBI.html |archive-date = 3 February 2010

Normally, there would be jets of gas shooting out in opposite directions. The observed jet is the one that faces the earth and projects plasma towards Earth. There is also a jet heading away from Earth called a counter jet. Close into the core, this counter jet is so much dimmer than the main jet that it is invisible in radio waves.

The brightness of the counter jet is less than the main jet by a factor of 1250. This implies that the jet is relativistic with Γ about 15 (that is, the plasma is moving at 99.8% of the speed of light) and at an angle between 15° and 25° from the line of sight from the Earth. At 408 MHz, the power level is 1.81 Jy, although this is variable.{{cite web|url=http://cdsweb.cern.ch/record/641783/files/0309285.pdf|title=Parsec Scale Properties of Markarian 501 |last=Giroletti|first=M. |author2=G. Giovannini |author3=L. Feretti |author4=W.D. Cotton |author5=P.G. Edwards |author6=L. Lara |author7=A.P. Marscher |author8=J.R. Mattox |author9=B.G. Piner |author10=T. Venturi |display-authors=8 |date=11 September 2003|access-date=6 December 2011}}

Beyond 10 kpc from the core, the counter jet becomes visible, showing that the jets have become non-relativistic; that is, plasma is no longer moving close to the speed of light. The symmetrical radio emission extends to 70", which corresponds to 120 to 200 kpc.

Blazar research

In March 2022, scientists led by Ioannis Liodakis studied Markarian 501 during an average state while discerning how blazars make such a bright light using Imaging X-ray Polarimetry Explorer (IXPE). The researchers were "able to show that the particles in these jets are supercharged by shock fronts, resolving a longstanding 'unanswered question' about the dynamics of these brilliant objects."

Catalog entries

Early designations were 4C 39.49 and B2 1652+39. The Uppsala General Catalogue of Galaxies lists this as UGC 10599.

Other designations: B1652+39 or 1H1652+398 or TeV J1653+397.

Notes

References

References

1. (2020). "The third realization of the International Celestial Reference Frame by very long baseline interferometry". Astronomy and Astrophysics.
2. "7C 165211.80+395026.00".
3. {{NED link
4. (2010). "A catalogue of quasars and active nuclei: 13th edition". Astronomy and Astrophysics.
5. (2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal.
6. (2023). "Siena Galaxy Atlas 2020". The Astrophysical Journal Supplement Series.
7. Aharonian, F. A.. (1999). "The time averaged TeV energy spectrum of Mkn 501 of the extraordinary 1997 outburst as measured with the stereoscopic Cherenkov telescope system of HEGRA". Astronomy and Astrophysics.
8. (2015). "Hunting for Supermassive Black Holes in Nearby Galaxies with the Hobby-Eberly Telescope". The Astrophysical Journal Supplement Series.
9. Protheroe, Ray J.. (12 October 1997). ["Very high energy gamma rays from Markarian 501"](https://arxiv.org/PS_cache/astro-ph/pdf/9710/9710118v1.pdf -->).
10. Markaryan, B. E.. (1974). "Galaxies with ultraviolet continuum V". Astrophysics.
11. "Object: Galaxy UGC 10599 = Markarian 501".
12. Acciari, V. A.. (2011). "Spectral Energy Distribution of Markarian 501: Quiescent State vs. Extreme Outburst". Astrophysical Journal.
13. (2008). "Probing quantum gravity using photons from a flare of the active galactic nucleus Markarian 501 observed by the MAGIC telescope". Physics Letters B.
14. "Einstein Makes Extra Dimensions Toe The Line". [[NASA]].
15. Barbieri, G. (1977). "The optical variability of the galaxy Markarian 501". Acta Astronomica.
16. (2003). "On the central black hole mass in Mkn 501". Astronomy and Astrophysics.
17. (23 November 2022). "Scientists Solve Major Mystery of Powerful Energy Beams Pointed at Earth".
18. (2022-11-23). "Polarized blazar X-rays imply particle acceleration in shocks". Nature.
19. (1974). "The Formation and Dynamics of Galaxies". [[Kluwer Academic Publishers]].
20. "UGC 10599". VII/26D/catalog Uppsala General Catalogue of Galaxies (UGC) (Nilson 1973).
21. "Markarian 501". TeVCat.

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