3C 273

Observation

3C 273 is visible from March to July in both the northern and southern hemispheres. Situated in the Virgo constellation, it is bright enough to be observed by eye with a 6 inch amateur telescope. Due in part to its radio luminosity and its discovery as the first identified quasar, 3C 273's right ascension in the Fifth Fundamental Catalog (FK5) is used to standardize the positions of 23 extragalactic radio sources used to define the International Celestial Reference System (ICRS).

Given its distance from Earth and visual magnitude, 3C 273 is the most distant celestial object average amateur astronomers are likely to see through their telescopes.

Properties

This is the optically brightest quasar in the sky from Earth with an apparent visual magnitude of ~12.9, and one of the closest with a redshift, z, of 0.158. A luminosity distance of DL = 749 Mpc may be calculated from z. Using parallax methods with the Very Large Telescope interferometer yields an angular distance estimate of DA= (). The latter distance is relatted to the comoving distance as D_L=(1+z)^2D_A.

It is one of the most luminous quasars known, with an absolute magnitude of −26.7, meaning that if it were only as distant as Pollux (~10 parsecs) it would appear nearly as bright in the sky as the Sun. Since the Sun's absolute magnitude is 4.83, it means that the quasar is over 4 trillion times more luminous than the Sun at visible wavelengths.

The luminosity of 3C 273 is variable at nearly every wavelength from radio waves to gamma rays on timescales of a few days to decades. Polarization with coincident orientation has been observed with radio, infrared, and optical light being emitted from a large-scale jet; these emissions are therefore almost certainly synchrotron in nature. The radiation is created by a jet of charged particles moving at relativistic speeds. VLBI radio observations of 3C 273 have revealed proper motion of some of the radio emitting regions, further suggesting the presence of relativistic jets of material.

This is a prototype of an Active Galactic Nucleus, demonstrating that the energy is being produced through accretion by a supermassive black hole (SMBH). No other astrophysical source can produce the observed energy. The mass of its central SMBH has been measured to be million solar masses through broad emission-line reverberation mapping.

Large-scale jet

The quasar has a large-scale visible jet, which measures ~200000 ly long, having an apparent size of 23″. Such jets are believed to be created by the interaction of the central black hole and the accretion disk. In 1995, optical imaging of the jet using the Hubble Space Telescope revealed a structured morphology evidenced by repeated bright knots interlaced by areas of weak emission. The viewing angle of the jet is about 6° as seen from Earth. The jet was observed to abruptly change direction by an intrinsic angle of 2° in 2003, which is larger than the jet's intrinsic opening angle of 1.1°. An expanding cocoon of heated gas is being generated by the jet, which may be impacting an inclined disk of gas within the central .

Host galaxy

3C 273 lies at the center of a giant elliptical galaxy with an apparent magnitude of 16 and an apparent size of 29 arcseconds. The morphological classification of the host galaxy is E4, indicating a moderately flattened elliptical shape. The galaxy has an estimated mass of .

History

The name signifies that it was the 273rd object (ordered by right ascension) of the Third Cambridge Catalog of Radio Sources (3C), published in 1959. After accurate positions were obtained using lunar occultation by Cyril Hazard at the Parkes Radio Telescope, the radio source was quickly associated with an optical counterpart, an unresolved stellar object. In 1963, Maarten Schmidt and Bev Oke published a pair of papers in Nature reporting that 3C 273 has a substantial redshift of 0.158, placing it several billion light-years away.

Prior to the discovery of 3C 273, several other radio sources had been associated with optical counterparts, the first being 3C 48. Also, many active galaxies had been misidentified as variable stars, including the famous BL Lac, W Com and AU CVn. However, it was not understood what these objects were, since their spectra were unlike those of any known stars. Its spectrum did not resemble that of any normal stars with typical stellar elements. 3C 273 was the first object to be identified as a quasar—an extremely luminous object at an astronomical distance.

3C 273 is a radio-loud quasar, and was also one of the first extragalactic X-ray sources discovered in 1970. However, the process which gives rise to the X-ray emissions was still controversial as of 2006 when new observations were reported with the Spitzer Space Telescope.

References

References

1. "Best image of bright quasar 3C 273". ESA/Hubble Picture of the Week.
2. "NASA/IPAC Extragalactic Database". Results for 3C 273.
3. Talcott, Richard. (November 17, 2023). "Target acquired: Observe Quasar 3C 273". [[Astronomy (magazine).
4. International Earth Rotation & Reference Systems Service. "Definition of ICRS Axes".
5. Uchiyama, Yasunobu. (2006). "Shedding New Light on the 3C 273 Jet with the Spitzer Space Telescope". The Astrophysical Journal.
6. (1964). "The Quasi-Stellar Radio Sources 3C 48 and 3C 273". The Astrophysical Journal.
7. (November 18, 2013). "Best image of bright quasar 3C 273".
8. Per the formula for [[Magnitude_(astronomy)#Apparent_magnitude
9. (1981). "Superluminal expansion of quasar 3C273". Nature.
10. (1991). "Large-scale superluminal motion in the quasar 3C273". Nature.
11. (July 2019). "Jet-driven Galaxy-scale Gas Outflows in the Hyperluminous Quasar 3C 273". The Astrophysical Journal.
12. Peterson, B. M.. (2004). "Central Masses of AGNs. II.". The Astrophysical Journal.
13. (March 2021). "An Oversized Magnetic Sheath Wrapping around the Parsec-scale Jet in 3C 273". The Astrophysical Journal.
14. Bahcall, John N.. (1997). "Hubble Space Telescope Images of a Sample of 20 Nearby Luminous Quasars". The Astrophysical Journal.
15. (May 2019). "Kinematics of the Broad-line Region of 3C 273 from a 10 yr Reverberation Mapping Campaign". The Astrophysical Journal.
16. Hazard, C.. (1963). "Investigation of the Radio Source 3C273 by the method of Lunar Occultations". Nature.
17. Schmidt, M.. (1963). "3C 273 : A Star-Like Object with Large Red-Shift". Nature.
18. Oke, J. B.. (1963). "Absolute Energy Distribution in the Optical Spectrum of 3C 273". Nature.