NASA’s Hubble Space Telescope and the New Horizons spacecraft recently focused on Uranus, enabling scientists to compare the planet from two distinct perspectives. This collaboration enhances future research plans for observing similar planets around different stars.
NASA’s Hubble Space Telescope and New Horizons spacecraft recently focused on Uranus, enabling scientists to compare the planet from two distinct perspectives. This collaboration enhances future research plans for observing similar planets around different stars.
Astronomers viewed Uranus as a representative for exoplanets beyond our solar system, using high-resolution images from Hubble alongside the more distant perspective provided by New Horizons. This dual observation helps scientists prepare for future imaging of planets orbiting other stars using upcoming telescopes.
“While we anticipated variations in Uranus’s appearance across different filters, we discovered that it was dimmer than we expected based on New Horizons observations taken from a different angle,” said lead author Samantha Hasler from the Massachusetts Institute of Technology in Cambridge, who is also part of the New Horizons science team.
Direct imaging of exoplanets is vital for understanding their potential for supporting life, as it offers insights into the formation and origin of our own solar system. Astronomers utilize both direct imaging and spectroscopy to analyze light from the target planet and assess brightness across various wavelengths. However, capturing images of exoplanets presents significant challenges due to their vast distances, often resulting in just pinpoint images that lack the detail provided by closer solar system worlds. Researchers can typically only directly image exoplanets during “partial phases,” when only a segment of the planet is illuminated by its star as seen from Earth.
Uranus was an excellent target for this kind of investigation due to several factors. Many known exoplanets are gas giants, similar to Uranus. At the time of the observations, New Horizons was positioned 6.5 billion miles away on the far side of Uranus, allowing for the study of its twilight crescent—a perspective unobtainable from Earth. From that distance, New Horizons captured only a few pixels of the planet using its color camera, the Multispectral Visible Imaging Camera.
In contrast, Hubble, operating in a low-Earth orbit just 1.7 billion miles from Uranus, provided high-resolution images that revealed atmospheric details like clouds and storms on the planet’s day side.
“In the New Horizons observations, Uranus appears merely as a tiny dot, akin to the dots we see for directly-imaged exoplanets from observatories like Webb or those located on the ground,” Hasler noted. “Hubble gives context to the atmospheric conditions when New Horizons captured its data.”
The gas giants within our solar system have highly dynamic and variable atmospheres with shifting cloud patterns. How prevalent is this among exoplanets? By understanding the cloud structures on Uranus as observed by Hubble, researchers can validate their interpretations of the data from New Horizons. In Uranus’s case, both Hubble and New Horizons indicated that the brightness remained stable as the planet rotated, suggesting that the cloud features did not alter with the planet’s rotation.
However, the insights gained from New Horizons revolve around how the planet reflects light at different phases compared to what Hubble or terrestrial observatories can capture. New Horizons revealed that exoplanets might be dimmer than anticipated during partial and high phase angles, with variations in light reflection occurring at those times.
NASA has two major upcoming observatories aimed at enhancing studies of exoplanet atmospheres and their potential for habitability.
“These groundbreaking New Horizons studies of Uranus from an unrivaled perspective have contributed significantly to our scientific knowledge and, like many other datasets gathered during the mission, have provided unexpected insights into the worlds within our solar system,” said New Horizons principal investigator Alan Stern from the Southwest Research Institute.
Nasa’s future Nancy Grace Roman Space Telescope, scheduled to launch by 2027, will employ a coronagraph to block out starlight, enabling direct visibility of gas giant exoplanets. Meanwhile, the Habitable Worlds Observatory, currently in the planning stage, will be the first telescope specifically designed to detect atmospheric biosignatures on Earth-sized rocky planets orbiting other stars.
“Examining established benchmarks like Uranus through distant imaging can allow us to form stronger expectations as we prepare for these future missions,” Hasler concluded. “This will be crucial for achieving success.”
Launched in January 2006, New Horizons achieved a historic flyby of Pluto and its moons in July 2015, followed by its first close-up look at Kuiper Belt object Arrokoth in January 2019. New Horizons is now engaged in its second extended mission, exploring distant Kuiper Belt objects, studying the outer heliosphere of the Sun, and conducting significant astrophysical observations from its unique position in the far reaches of the solar system.
The findings regarding Uranus are being shared this week at the 56th annual meeting of the American Astronomical Society Division for Planetary Sciences in Boise, Idaho.
The Hubble Space Telescope has been operational for over thirty years, continuing to yield groundbreaking discoveries that enhance our understanding of the universe. Hubble is a collaborative project between NASA and the European Space Agency (ESA). The mission and its operations are managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with support from Lockheed Martin Space in Denver, Colorado. Hubble’s scientific operations for NASA are managed by the Space Telescope Science Institute in Baltimore, Maryland, operated by the Association of Universities for Research in Astronomy.
The Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, constructed and operates the New Horizons spacecraft while managing the mission for NASA’s Science Mission Directorate. The Southwest Research Institute, based in San Antonio and Boulder, Colorado, directs the mission led by Principal Investigator Alan Stern, overseeing scientific operations, payload management, and encounter science planning. New Horizons is part of NASA’s New Frontiers program, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama.
