Einstein Cross

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QSO 2237+0305
Einstein cross.jpg
Observation data (Epoch J2000)
Right ascension22h 40m 30.3s
Declination+3° 21′ 31″
Distance8,000,000,000 ly (2,500,000,000 pc)
Apparent dimensions (V)less than 2"
Apparent magnitude (V)16.78
Other designations
LEDA 69457, Z 378-15
See also: Quasar, List of quasars

The Einstein Cross (Q2237+030 or QSO 2237+0305) is a gravitationally lensed quasar that sits directly behind ZW 2237+030, Huchra's Lens. Four images of the same distant quasar (plus one in the centre, too dim to see) appear around a foreground galaxy due to strong gravitational lensing.[1][2] This system was discovered by John Huchra and coworkers in 1985.[3]

Another Einstein cross (J2211-3050) discovery was announced March 18, 2019.[4]

While gravitationally lensed light sources are often shaped into an Einstein ring, due to the elongated shape of the lensing galaxy and the quasar being off-centre, the images form a peculiar cross-shape instead.[5]


The quasar's redshift indicates that it is located about 8 billion light years from Earth, while the lensing galaxy is at a distance of 400 million light years. The apparent dimensions of the entire foreground galaxy are 0.87 × 0.34 arcminutes,[6] while the apparent dimension of the cross in its centre accounts for only 1.6 × 1.6 arcseconds.

The Einstein Cross can be found in Pegasus at 22h 40m 30.3s, +3° 21′ 31″.

Amateur astronomers are able to see some of the cross using telescopes; however, it requires extremely dark skies and telescope mirrors with diameters of 18 inches (46 cm) or greater.[7]

The individual images are labelled A through D (i.e. QSO 2237+0305 A), the lensing galaxy is sometimes referred to as QSO 2237+0305 G.


See also[edit]


  1. ^ NASA and ESA (September 13, 1990). "The Gravitational Lens G2237 + 0305". HubbleSite. Retrieved July 25, 2006.
  2. ^ Drakeford, Jason; Corum, Jonathan; Overbye, Dennis (March 5, 2015). "Einstein's Telescope - video (02:32)". The New York Times. Retrieved December 27, 2015.
  3. ^ Huchra, J.; et al. (1985). "2237 + 0305: A new and unusual gravitational lens". Astronomical Journal. 90: 691–696. Bibcode:1985AJ.....90..691H. doi:10.1086/113777.
  4. ^ "A new Einstein cross is discovered". phys.org. Retrieved 2019-11-13.
  5. ^ "How does gravitational lensing account for Einstein's Cross?". physics.stackexchange.com. Retrieved 2016-06-26.
  6. ^ "LEDA 69457". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 12 February 2017.
  7. ^ Crinklaw, Greg. "Focus on Einstein's Cross". Retrieved 2013-06-29.
  8. ^ "Cosmic lenses support finding on faster than expected expansion of the Universe". www.spacetelescope.org. Retrieved 27 January 2017.

External links[edit]

Coordinates: Sky map 22h 40m 31.0s, +03° 21′ 30.3″