NASA Shares Hubble’s Gravitationally Lensed Cosmic Smile

Galaxy cluster SDSS J1038+4849 had arranged itself into a smile. NASA's X account posted the image on October 11, 2026, two bright points set like eyes.

Judy Schmidt had already brought a version of those same Hubble frames into public view. She entered her processing of the image in the Hidden Treasures competition. Social-media users met it at once. Commenters called gravitational lensing one of the coolest things in astronomy. A few joked that even extraterrestrials might now trade in emojis.

The eyes resolved into two galaxies inside the 2015 Hubble frame of galaxy cluster SDSS J1038+4849. The cluster lies about 4.5 billion light-years from Earth. That distance places the structure inside the Big Dipper constellation, whose pattern of stars marks the region of sky that holds the face.

The two eyes are the galaxies SDSSCGB 8842.3 and SDSSCGB 8842.4. These massive galaxies appear as the orange points. Between them a compact white feature forms the button nose. Curved arcs of light complete the face.

NASA stated the fact in the social-media post that carried the image. "The smile lines are arcs caused by an effect known as gravitational lensing, where massive structures warp spacetime with their powerful gravitational forces and act as a cosmic lens."

Gravitational lensing is the bending of light from more distant objects as it travels past a mass dense enough to curve spacetime around it. Light that would otherwise continue in a straight line follows the warp instead, so the image of the background source reaches the observer stretched into long arcs rather than a single undistorted point. The galaxy cluster supplies that mass. Its gravity warps spacetime and acts as the cosmic lens that draws the distant light into those curves.

The arcs belong to the special case known as an Einstein ring. An Einstein ring forms when the distant source of the light, the lensing mass, and the observer fall into exact alignment. The bent light then closes into a ring around the lens. The entire phenomenon was predicted by Einstein's general theory of relativity.

Einstein set the ring into print in 1936 and dismissed any chance of seeing it. "Of course, there is no hope of observing this phenomenon directly. First, we shall scarcely ever approach closely enough to such a central line. Second, the angle β will defy the resolving power of our instruments."

He had worked the deflection in unpublished calculations as early as 1912. A letter from the Czech engineer R. W. Mandl brought him back to the numbers. The published paper gave the angle its measure and then shut the door. Alignments tight enough to form a full ring would almost never occur. Instruments of the day could never resolve so small a deflection. The effect stayed pure theory on the page.

Sixty-two years later the first complete Einstein ring was photographed. Astronomers at the University of Manchester, working with NASA's Hubble Space Telescope, found B1938+666 in 1998 through optical follow-up of a lens first imaged in radio. Light from a dark dwarf satellite galaxy had closed into a full ring around an ancient elliptical. Einstein had said there was no hope. The ring was there.

Hubble trained two of its cameras on the smiling cluster. The Wide Field and Planetary Camera 2 and the Wide Field Camera 3 recorded SDSS J1038+4849 as part of a dedicated survey of strong lenses, the class of gravitational deflection that stretches background light into the visible arcs and rings already on the frame.

Those warped paths become measuring tools. The precise shape of each arc traces the total mass that produced the bend, including the dark matter whose gravity contributes to the warp yet emits no light of its own. Astronomers map the dark-matter distribution inside the cluster by modeling how the light is distorted. At the same time the lens magnifies galaxies that would otherwise remain too faint or too distant for the telescope to register, turning the cluster into a natural amplifier that reaches farther into the early universe.

Each new lensing image joins a growing catalog of cosmic lenses essential for the work planned with the James Webb Space Telescope and the Nancy Grace Roman Space Telescope. Both instruments will draw on the recorded lenses when they turn to background galaxies too faint to reach without magnification. Hubble and other observatories continue to add frames of similar strong-lensing events across the sky, expanding the same list the newer telescopes will use to examine the early universe.

The 2015 Hubble exposure of the smiling cluster remains one entry in that archive. The arcs that complete the face stay frozen in place on the stored frame.