Those two little dots are the same quasar, Q0957+561. A galaxy and its surrounding cluster sit between it and us. Their gravity bends the quasar’s light along two different routes, so we see it twice. The dots are only about six arcseconds apart on the sky.

A quasar is the dazzling centre of an active galaxy. Gas swirling towards a supermassive black hole gets very hot and bright. It’s the gas around the black hole that we see, rather than the black hole itself.

When astronomers found the Twin Quasar in 1979, it became the first confirmed gravitational lens. The two images are called A and B. Light takes a different amount of time to reach us along each route, so a change in the quasar’s brightness appears in B about 417 days after it appears in A. Amazing to think that one photo is showing a single object at two different times!

Eagle-eyed readers will note that the two quasar images don’t look identical in my image. Small differences in the dots’ shapes can come from atmospheric blurring, pixel sampling, noise and processing. Their brightnesses can differ too, because the lens can magnify each image differently and we’re seeing the quasar at two different moments.

There’s another object to spot in the frame: NGC 3079. This spiral galaxy is almost edge-on to us, so its disc looks long and thin, with dark dust running through it. At roughly 50 million light-years away, it’s much closer than the quasar.

Despite sharing the photograph, NGC 3079 isn’t the galaxy doing the lensing. The real lensing galaxy, YGKOW G1, is much farther away and isn’t separately resolved in my image. It lies only about one arcsecond from image B, so any light I’ve recorded from the galaxy is blended with that quasar image. I love the contrast here: one galaxy whose shape we can make out, and, nearby in the picture, two faint dots showing us one distant object.