According to Uranus’ infrared images of the five main moons, their composition is closer to dwarf planets such as Pluto and Humia – compact, rocky objects with an icy crust – than the more drunken creations of small cranian moons.
Uranus orbits the Sun at a distance of about 20 times the Earth’s average. We haven’t sent out many spacecraft yet – only NASA’s Vyzer 2 spacecraft had a close encounter with Uranus in 1986, on the way to the edge of the solar system and beyond.
In addition to those voyager 2 observations, our study of the planet and its satellites relied on telescopes close to home on Earth and in the Earth’s orbital region. Which makes it very challenging to see the moon; They are much smaller and reflect much less sunlight than Uranus, so they transcend the point of invisibility.
“The moons, which are obscured 500 and 7,400 times, are so short distances from Uranus that they merge with similar bright artifacts,” said astronomer Gabor Marten of the Konkoli Observatory in Hungary. “Only the brightest moons, Titania and Oberon, stand slightly out of the surrounding glare.”
Which accidentally detects five moons to study the galaxy in infrared radiation, in operation between 2009 and 2013 by the Herschel Space Observatory of the European Space Agency.
“In fact, we carried out observations to measure the effect of very bright infrared sources such as Uranus on the camera detector,” said Ulrich Klaar, an astronomer at the Max Planck Institute for Astronomy in Germany.
“We only discovered moons as additional nodes in the planet’s extremely bright signal.”
The five main moons of Uranus are in descending order of size, Titania, Oberon, Umbril, Ariel, and Miranda. Vyzer 2 reported that all five have a round shape indicating that they have attained hydrostatic equilibrium — namely, enough mass under their gravity to develop a symmetric, round shape. And they appear to be made of rock and ice.
This is not uncommon for objects far from the Sun. Even when heated by the Sun, Uranus and its moons have temperatures as high as only 60 and 80 Kelvin (-213 to -193 ° C, or -350 to -315 ° F) at the surface. Pluto is very rocky and icy.
But how is that rock and ice put together. Uranus’s eccentric orbits of small, irregular, asymmetric moons suggest that they have a composition similar to the rocky bodies in the Kuiper belt beyond Neptune, cross-Neptune objects. These are bound together only, and are quite small.
“It would also fit with speculation about the origin of irregular moons,” said Thomas Muller, an astronomer at the Max Planck Institute for Extraterritorial Physics in Germany. “Because of their chaotic orbits, it is believed that they were captured by the Uranian system only at a later date.”
Typically, the five main moons orbiting the equator of Uranus will be difficult to see. Uranus has a strange orientation, which is entangled on its own side with respect to its orbital plane around the Sun, so its equator is often in shadow.
During Uranus’ team observations between 2010 and 2012, however, the equator was under telescope and sunlight. And when the team deduced Uranus from the data using a specially developed algorithm, something surprising emerged.
“We were all surprised when four moons were clearly visible on the images, and we could also detect Miranda, the smallest and smallest of the largest Uranian moons,” astronomer H. of the Max Planet Institute of Astronomers. D. Deere said.
This enabled the team to measure how well the lunar surfaces retained heat from the sun as this surface rotated away at night. These surfaces, it turned out, retained heat quite well, cooling relatively slowly.
It had a familiar heat retention and cooling profile – the closest match being dwarf planets like Pluto and Humia, with dense rocky bodies and surfaces made of ice. This suggests that Titania, Oberon, Umbril, Ariel, and Miranda are formed in the same way – although the exact chemical composition of rock and ice has not yet been determined.
The discovery could mean that sending an investigation to ice giants could help us learn about more distant objects, even farther into the dim reaches of the Kuiper Belt. But it also shows the value of looking under our nose.
“The result shows that we don’t always need detailed space missions to get new insights into the solar system,” said Hendrik Linz, an astronomer at the Max Planck Institute for Astronomy.
“In addition, the new algorithm can be applied to further observations that have been collected in large numbers in the electronic data collection of the European Space Agency ESA. Who knows what surprises are still there for us?”
The research has been published in Astronomy and Astrophysics.