A team of researchers were able to characterize the five main Uranian moons thanks to a coincidence and the observatory named after the astronomer who discovered the planet.
It was William Herschel who discovered Uranus in 1781 and years later discovered two of its largest moons, Oberon and Titania. According to NASA, Uranus was initially thought to be a comet but it was confirmed as a new planet two years later and it is now known to be the seventh planet in the solar system with 13 rings and 27 known moons.
But because of its distance, it has largely been through space probes such as Voyagers 1 and 2 that scientists were able to explore Uranus’ moons and other objects at the outer regions of the solar system. In fact, no other spacecraft apart from Voyager 2 has been able to orbit or fly by Uranus to study it.
What’s more, Uranus’s signature is so bright that the significantly fainter signatures from its moons just tend to merge with it.
However, in a new study published in Astronomy & Astrophysics, a team of researchers was able to characterize five of the Uranian moons through the observations captured by the Herschel Space Observatory. Using a new method, the researchers were able to make the moons more visible by essentially removing Uranus’s infrared signature from the data, thereby giving them a clearer, more detailed view of the moons.
The researchers found that the moons Titania, Oberon, Umbriel, Ariel and Miranda are actually much like the dwarf planets at the edge of the solar system and that they have icy and rough surfaces which tend to store heat well and cool down slowly.
They were also found to have « chaotic » orbits, suggesting that they were only captured by Uranus later on in its life.
Uranus is seen in this false-color view from NASA’s Hubble Space Telescope from August 2003. The brightness of the planet’s faint rings and dark moons has been enhanced for visibility. Photo: NASA/Erich Karkoschka (Univ. Arizona)
Interestingly, it was a coincidence that led to the researchers’ work as they had actually intended to measure something else.
« Actually, we carried out the observations to measure the influence of very bright infrared sources such as Uranus on the camera detector, » study co-author Ulrich Klaas of the Mas Planck Institute for Astronomy (MPIA) said in a news release from the research institution. « We discovered the moons only by chance as additional nodes in the planet’s extremely bright signal. »
Furthermore, the timing of their observations also provided an advantage. As the news release explains, because Uranus is unusually inclined in that it has a unique sideways rotation, it is only typically the northern or southern hemisphere that gets illuminated by the sun. In fact, even when Voyager 2 made its closest approach of Uranus in 1986, it only got to image Uranus and its moons’ south pole regions.
But the position when the researchers were conducting their observations allowed them to take measurements that were previously difficult to gather.
« The timing of the observation was also a stroke of luck, » study co-author Thomas Müller of Max Planck Institute for Extraterrestrial Physics (MPE) said in the news release. « During the observations, however, the position was so favorable that the equatorial regions benefited from the solar irradiation. This enabled us to measure how well the heat is retained in a surface as it moves to the night side due to the rotation of the moon. »
Apart from demonstrating a new technique, the researchers’ work shows how ingenuity can help in the exploration of the solar system.
« The result demonstrates that we don’t always need elaborate planetary space missions to gain new insights into the Solar System, » study co-author Hendrik Linz of MPIA said in the news release. « In addition, the new algorithm could be applied to further observations which have been collected in large numbers in the electronic data archive of the European Space Agency (ESA). Who knows what surprise is still waiting for us there? »
