Uranus is a prime target as a test for understanding future distant observations of exoplanets as it acts as a proxy to understand several distant, similarly sized exoplanets better.
Recently, NASA’s Hubble Space Telescope and New Horizons spacecraft simultaneously targeted Uranus, allowing scientists to compare the planet from two different viewpoints.
The Hubble telescope offered high-resolution images, while the New Horizons provided the most distant view of the planet.
Hubble, positioned 1.7 billion miles from Uranus in low-Earth orbit, achieved high-resolution observations, revealing atmospheric details like clouds and storms on the planet’s daylight side. New Horizons, located 6.5 billion miles from Uranus on its far side, provided a unique opportunity to study the planet’s twilight crescent—an observation impossible from Earth. At that distance, Uranus appeared as just a few pixels in the spacecraft’s Multispectral Visible Imaging Camera.
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Lead author Samantha Hasler of the Massachusetts Institute of Technology in Cambridge, a New Horizons science team collaborator, said, “While we expected Uranus to appear differently in each filter of the observations, we found that Uranus was dimmer than predicted in the New Horizons data taken from a different viewpoint.”
“Uranus appears as just a small dot on the New Horizons observations, similar to the dots of directly imaged exoplanets from observatories like Webb or ground-based observatories. Hubble provides context for what the atmosphere was doing when it was observed with New Horizons.”
Direct imaging of exoplanets offers insight into their habitability, origin, and formation of our solar system. Astronomers utilize direct imaging and spectroscopy to analyze the light from these planets, comparing their brightness across different wavelengths.
However, capturing images of exoplanets is challenging due to their great distances. This results in images that appear as tiny points rather than detailed views like those of our solar system’s planets. Additionally, scientists can only image exoplanets during “partial phases,” when only part of the planet is lit by its star as seen from Earth.
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By analyzing the cloud details observed by Hubble, scientists can confirm interpretations made from New Horizons data. For Uranus, both Hubble and New Horizons noted that the planet’s brightness remained consistent during its rotation, suggesting that the cloud features were stable and did not change as the planet spun.
New Horizons principal investigator Alan Stern of the Southwest Research Institute said, “These landmark New Horizons studies of Uranus from a vantage point unobservable by any other means add to the mission’s treasure trove of new scientific knowledge and have, like many other datasets obtained in the mission, yielded surprising new insights into the worlds of our solar system.”
The Uranus results will be presented this week at the 56th annual American Astronomical Society Division for Planetary Sciences meeting in Boise, Idaho.
