Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

Weird Object: The Einstein Cross

No. 15: In Space, No One Can Hear You Photocopy.

CosmicCross
COSMIC CROSS.  A galaxy situated between Earth and a quasar 8 billion light-years away creates a “gravitational lens” that bends the quasar’s light, creating the four bright outer objects in this image. 
NASA/ESA/STScI

By now, everyone knows that space can warp. Albert Einstein’s 1916 general theory of relativity predicted this, and it was later affirmed when a star in Taurus next to the eclipsed Sun appeared slightly shifted, the path of that star’s light to Earth altered by solar gravity. But no one imagined a practical use for this phenomenon. 

Russian physicist Orest Chwolson gets credit for being the first, in 1924, to explain how the perfect alignment of a nearer massive object and a distant luminous one could create a ring surrounding the foreground entity, as its gravity influences the paths of the passing photons. It would, in effect, act like a lens and bend the light. Einstein more famously discussed this 12 years later, but said it would never be actually observed because he thought the chances were too slim of a star ever perfectly lining up with a background one. 

Astronomy magazine subscribers can read the full article for free. Just make sure you're registered with the website. 

Already a subscriber? Register now!

Registration is FREE and takes only a few seconds to complete. If you are already registered on Astronomy.com, please log in below.
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. View our Privacy Policy.

ADVERTISEMENT
ADVERTISEMENT
asy_LifeOnMars_rightrail

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook