Astronomy Picture of the Day ·

The Einstein Cross Gravitational Lens

The Astronomy Picture of the Day for October 17, 2021 is “The Einstein Cross Gravitational Lens,” an image. It is credited to Image Credit & License: J. Rhoads ( Arizona State U. ) et al. , WIYN , AURA , NOIRLab , NSF. The original explanation runs about 132 words.

The picture shows single distant quasar that appears four times due to the gravitational lens effect of an intervening galaxy. Please see the explanation for more detailed information.
Credit: Image Credit & License: J. Rhoads ( Arizona State U. ) et al. , WIYN , AURA , NOIRLab , NSF Shown from science.nasa.gov. Not hosted by OpenOrbit.

From the explanation

“Most galaxies have a single nucleus — does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image .”

— APOD editors, October 17, 2021

Read the full explanation on science.nasa.gov

At a glance

Date
October 17, 2021
Type
Image
Credit
Credit: Image Credit & License: J. Rhoads ( Arizona State U. ) et al. , WIYN , AURA , NOIRLab , NSF
Copyright
No copyright notice on the entry. Check the credited institution’s own usage rules before reusing it.
Explanation length
About 132 words

All of October 2021 → · 2021 by month → · Full archive since 1995 →

Topics in this entry

Galaxies

Topics are matched from words in the title and explanation.

On this day: October 17 in other years

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Source

Copy taken Oct 28, 2026, 2:39 AM EDT. The image and explanation belong to their creators. OpenOrbit is not affiliated with or endorsed by NASA.