New images show an interstellar comet that will soon make its closest approach to Earth

The Hubble Space Telescope observed interstellar comet 3I/ATLAS for the second time on November 30. (ESA/Juice/NavCam via CNN Newsource)

The Hubble Space Telescope and the Jupiter Icy Moons Explorer have captured fresh images of an interstellar comet as the object nears its closest approach to Earth later this month.

Comet 3I/ATLAS has intrigued astronomers because it originated outside of our solar system yet was discovered traveling through our celestial neighborhood in July.

Given that it’s only the third interstellar object ever observed zipping through our solar system, astronomers have directed numerous missions to focus on the comet. Observations have been critical in helping scientists determine the object’s trajectory and have even provided clues about its composition — as a result of the gases that sublimated from the comet during its closest pass by the sun in October.

Hubble was one of the first to observe 3I/ATLAS in July shortly after it was discovered, providing the most detailed view of the comet’s teardrop shape at the time.

Astronomers spotted 3I/ATLAS with Hubble again on November 30, when it was 178 million miles (286 million kilometers) from Earth, and using the telescope’s Wide Field Camera 3 instrument, captured an even clearer shot.

Meanwhile, an image taken by the European Space Agency’s Jupiter Icy Moons Explorer, or Juice, mission en route to study Jupiter and its icy moons, shows intriguing activity around the comet.

Spotting two tails

The Juice mission will investigate the potential habitability of Jupiter’s three largest moons, Ganymede, Calliston and Europa. The moons likely host subsurface oceans beneath their icy crusts that could support life.

But first, Juice has to reach Jupiter. The mission launched in April 2023 and is expected to arrive at its destination in July 2031.

And at the beginning of November, Juice was in a prime position to observe 3I/ATLAS from about 41 million miles (66 million kilometers) away from the comet.

The spacecraft used five of its scientific instruments, as well as its onboard Navigation Camera, or NavCam, to glimpse the comet.

Most of Juice’s data won’t arrive on Earth until February because the spacecraft is using its main antenna as a heat shield to protect it from the sun during its long journey to Jupiter. A smaller antenna is sending back data at a fraction of the rate.

The Juice team didn’t want to wait that long, so they downloaded a quarter of a single image taken by NavCam. The image shows heat-driven activity on the comet during its close pass by the sun.

The newly released image shows a coma, or a glowing halo of gas surrounding the comet, as well as two tails: a plasma tail composed of electrically charged gas, as well as a faint dust tail of solid particles being released.

Comets that originate in our solar system typically have both of these tails, as well as a hazy coma surrounding a solid core made of rock, gas, dust and ice leftover from the formation of the sun, planets or other celestial bodies. As comets approach stars like our sun, they heat up, forming tails of sublimating material that streak behind them.

Comet 3I/ATLAS will come within 167 million miles (270 million kilometers) of Earth on December 19, but it will be on the other side of the sun and poses no risk to our planet. For reference, Earth is about 93 million miles (150 million kilometers) from the sun. The comet is expected to remain visible to telescopes and space missions for a few more months before exiting our solar system, according to NASA.

The rest of the Juice data from the comet’s flyby, expected between February 18 and 20, should include images from the spacecraft’s high-resolution optical camera, as well as composition and particle data that could provide more clues about where the interstellar object originated.

By Ashley Strickland