Einstein Cross

QSO 2237+0305
Observation data (Epoch J2000)
Constellation Pegasus
Right ascension 22h 40m 30.3s
Declination +3° 21′ 31″
Redshift 1.695
Distance 8,000,000,000 ly (2,500,000,000 pc)
Type LeQ
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 (an additional image is present in the center, but it can't be seen with the naked eye) appear around a foreground galaxy due to strong gravitational lensing.[1][2]

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.[3]

Details

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,[4] 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.[5]

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

References

  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. ↑ "How does gravitational lensing account for Einstein's Cross?". physics.stackexchange.com. Retrieved 2016-06-26.
  4. ↑ "LEDA 69457". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 12 February 2017.
  5. ↑ Crinklaw, Greg. "Focus on Einstein's Cross". Retrieved 2013-06-29.
  6. ↑ "Cosmic lenses support finding on faster than expected expansion of the Universe". www.spacetelescope.org. Retrieved 27 January 2017.

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

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