Evrim Yazgin
Cosmos science journalist
NASA’s Hubble Space Telescope and New Horizons spacecraft have given a unique view of Uranus as they simultaneously set their sights on the 7th planet from the Sun.
The results will help in future studies of similar gas giant planets around other stars.
Hubble is in a low-Earth orbit. It trained its high-resolution camera on Uranus from about 2.7 billion km. Meanwhile, New Horizons was on the far-side of the planet, snapping a pic of Uranus from about 10.5 billion km.
“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,” says MIT researcher and New Horizons science team collaborator Samantha Hasler.
Exoplanets (planets beyond our solar system) are tens of thousands or millions of times further away than Uranus. Even using the most advanced machinery of the James Webb Space Telescope or ground-based observatories, exoplanets appear as mere specks.
This is how Uranus appears in the New Horizons’ image.
“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,” Hasler adds. “Hubble provides context for what the atmosphere is doing when it was observed with New Horizons.”
One of the most important aspects of the simultaneous observation is to do with the planet’s phase. This refers to the how much of the planet is illuminated by its host star. Exoplanets can only be directly imaged at “partial phases” – when just a portion of the planet is illuminated.
The New Horizons image is at a different phase compared to Hubble or other Earth-based observatories. The results show that exoplanets – like Uranus – may be dimmer than predicted at partial phase angles. The atmosphere of the planet reflects light differently at partial phase.
Researchers are hopeful that such studies will inform planned missions to explore worlds beyond our solar system.
One such project is NASA’s Habitable Worlds Observatory. In early planning, this telescope will be the first designed specifically to look for signs of life in the atmospheres of small, rocky exoplanets.
“Studying how known benchmarks like Uranus appear in distant imaging can help us have more robust expectations when preparing for these future missions,” says Hasler. “And that will be critical to our success.”
The results from the New Horizons and Hubble simultaneous images of Uranus will be presented at the 56th annual meeting of the American Astronomical Society Division for Planetary Sciences in Idaho, US.
