Two Iconic NASA Spacecraft Just Gazed At Uranus — Here’s What They Saw

Two of NASA'’s most famous spacecraft — one orbiting Earth and the other far away in the outer solar system — have simultaneously observed the seventh planet Uranus.

The Hubble Space Telescope orbits Earth, has a huge mirror measuring 7.8 feet (2.4 meters) to collect light, and imaged Uranus from 1.7 billion miles. Meanwhile, the New Horizons spacecraft has basic optics and is now about 6.5 billion miles distant (twice as far from the sun as Pluto). So they had drastically different viewpoints on the giant gas planet.

Dimmer Than Predicted

According to NASA, New Horizons sees a night sky 10 times darker than Hubble, but that wasn't decisive. "While we expected Uranus to appear differently in each filter of the observations, we found that Uranus was actually dimmer than predicted in the New Horizons data taken from a different viewpoint," said lead author Samantha Hasler of the Massachusetts Institute of Technology in Cambridge and New Horizons science team collaborator.

Twilight Crescent

New Horizons, on the far side of Uranus, was able to capture the twilight crescent of Uranus, something that is not possible from Earth. However, its image is just a few pixels wide in the distant spacecraft's color Multispectral Visible Imaging Camera. Hubble's higher-resolution images feature clouds and storms on the day side of Uranus. "Uranus appears as just a small dot on the New Horizons observations, similar to the dots seen of directly imaged exoplanets from observatories like Webb or ground-based observatories," added Hasler. "Hubble provides context for what the atmosphere was doing when it was observed with New Horizons."

Proxy For Exoplanets

The study was completed in October 2023 but only published last week during the 56th annual meeting of the American Astronomical Society Division for Planetary Sciences in Boise, Idaho. Its main purpose is to help astronomers know more about exoplanets, planets that orbit stars other than the sun. These distant star systems often have gas giant planets in orbit, making Uranus a valuable proxy. By comparing the high-resolution images from Hubble to the more distant view from New Horizons, astronomers will know what to expect when they image exoplanets with telescopes of the future. "Studying how known benchmarks like Uranus appear in distant imaging can help us have more robust expectations when preparing for these future missions," said Hasler.

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Fast-Mover

Launched in 2006, New Horizons is famous for its flyby of Pluto in 2015, the first time the dwarf planet had been imaged close-up. The fastest-moving spacecraft ever launched, it travels 300 million miles per year. According to NASA, on Oct. 1, 2024, New Horizons passed 60 times as far from the sun as Earth is.

In 2019, it conducted a flyby of Arrokoth, a double-lobed asteroid in the Kuiper Belt leftover from the solar system's formation.

New Mission

From next year, the spacecraft will focus on gathering unique heliophysics data. “The New Horizons mission has a unique position in our solar system to answer important questions about our heliosphere and provide extraordinary opportunities for multidisciplinary science for NASA and the scientific community,” said Nicola Fox, associate administrator for NASA’s Science Mission Directorate in Washington, in a press release last September announcing the decision.

New Horizons will exit the Kuiper Belt in 2028 or 2029 and approach the solar system's edge.

Wishing you clear skies and wide eyes.