On the night of March 13, 1781, William Herschel was looking through his telescope at his back garden on New King Street, Bath, when he noticed an unusual faint object near the star Zeta Tauri. He watched him for several nights and watched him move slowly against the background stars. The astronomer first thought he had found a comet, but then correctly identified it as a distant planet. Later called Uranus, it was the first planet to be discovered since antiquity. Success made Herschel a member of the Royal Society, a knight and a lasting astronomical fame.
Since then, studies have shown that Uranus is a very strange world. While the rest of the planets in our solar system spin like peaks, Uranus is on its side. And while it is not the farthest planet from the sun, it is the coldest in the solar system.
Uranus also supports stations of extraordinary magnitude. Each pole spends decades bathed in non-stop sunlight, before experiencing decades of total darkness. A human who was born at dusk near the pole disappearing in the darkness of autumn, would have to wait 42 years to see his first spring sunrise. To a large extent, Uranus is the only planet named after a Greek god instead of a Roman god. (Uranus was the grandfather of Zeus.)
Despite these rarities and astronomical extremes, surprisingly little effort has been made to get closer to Uranus. Only one robotic probe has ever visited it, in 1986, when the American vessel Voyager 2 passed on its great journey through the solar system. It revealed a massive, shotless, pale blue world with an atmosphere of hydrogen, helium and methane, a rich family of moons and a powerful magnetic field. And that has been it.
However, this small consideration is about to change. Earlier this year, the U.S. National Academy of Sciences released a report urging NASA to launch a Uranus probe as a top-priority flagship mission for the next decade. The academy publishes a report on U.S. priorities in planetary exploration every 10 years and each decennial survey has a huge influence, meaning NASA is under enormous pressure to design and fund this mission.
The ice giant Uranus. Photography: Alamy
For their part, Uranus enthusiasts are delighted. “It’s tremendous news,” says planetary science professor Leigh Fletcher of the University of Leicester. “There are few places in the solar system of which we know less than Uranus. The inner planets have been visited many times by probes and also Jupiter and Saturn. Even the small and distant Pluto has been studied. Therefore, a mission of ‘Uranus will fill an obvious gap in our knowledge of the processes that shaped our solar system.
Astronomers divide the planets of the sun into three basic categories. There are Mercury, Venus, Earth and Mars, the rocky inner planets orbiting near the sun. Then, further afield, are the gas giants Jupiter and Saturn, huge worlds made mostly of hydrogen and helium. Finally, on the edge of the solar system are Uranus and its partner Neptune, respectively the second farthest planet and the farthest from the sun. These two are called ice giants because they are massive (though not as large as Jupiter and Saturn) and because they are formed from icy material. Crucially, they have a large abundance of methane, water, and other molecules that form ice in their atmospheres and interiors. (Beyond these worlds is Pluto, which was formally declassified as a planet and recategorized as a dwarf planet by the International Astronomical Union in 2006).
These features were always considered interesting, though not intriguing enough to deserve special attention, until astronomers began studying worlds around other stars and found ice giants like Uranus and Neptune everywhere. “It’s really intriguing: when we look at planets around other stars, we find that many of them are similar to Uranus and Neptune,” Fletcher adds. Or as Jonathan Fortney, a planetary scientist at the University of California Santa Cruz, says, “nature loves to make planets of this size.”
It is unclear why ice giants are widespread in our galaxy. “However, there is obviously something important about planets like Uranus and Neptune,” Fletcher says. “And crucially, we have two great examples of them, the most common planets in the galaxy, right here in our solar system. However, their composition, their nature, and their origins remain a relative mystery. “It ‘s time to put it right.”
Correcting this planetary omission, however, will not be easy. Uranus orbits the sun at an average distance of 1.8 billion miles (2.8 billion km); Neptune at 2.8 billion miles (4.5 billion km). Therefore, the relative proximity of the former to Earth makes it the preferred target. However, a mission from Uranus will still need help to achieve its goal, in the form of Jupiter’s gravity aid. This type of maneuver has been used in other missions of our solar system and involves a spacecraft sweeping low over a planet that is in its path. The capsule gains energy from this upcoming encounter and can therefore carry more instruments and fuel than would otherwise be possible. Therefore, an encounter with Jupiter would result in a Uranus probe that, with more fuel on board, could explore Uranus for longer with a more sophisticated set of instruments.
The launch of the rocket carrying the Voyager 2 spacecraft from Cape Canaveral, Florida, on August 20, 1977, 16 days before the launch of its twin, the Voyager 1. Photo: Nasa
But the timing is tight. Celestial mechanics dictates that a Uranus mission will have to be launched in 2031 or 2032 to reach Jupiter at the right time to exploit it for gravity aid. This leaves NASA with a decade to design the spacecraft, raise the $ 4 billion (£ 3.3 billion) or more that will be needed to build it, complete its construction and then launch it on its journey. 13 years. Given these pressures, and the widespread interest in exploring the ice giants, the project will almost certainly involve the participation of other organizations, such as the European Space Agency.
Most ideas for the mission envisage a main spacecraft that would orbit Uranus, inspect the planet as it occasionally moves near some of its moons and rings for close inspection. An accompanying probe could also be launched into the uranium atmosphere to study its composition.
Aside from finding evidence that could explain why ice giants are common around other stars, the mission would aim to solve many other mysteries about Uranus. Why the planet is so cold and why its axis of rotation is tilted sideways, almost toward the plane of its orbit around the sun, a phenomenon that means its north and south poles are where most of them are. do other planets have their equators?
“One theory is that a very large object, perhaps a huge asteroid, struck Uranus some time ago and knocked it down,” says physicist Patrick Irwin of Oxford University. “This event would also explain another strange feature of Uranus: it seems that it has almost no internal heat left from its formation, making it the coldest planet in the solar system.
“Jupiter, Saturn and even Neptune still have some internal heat and emit more energy into space than they collect from the sun. But not Uranus. All their internal heat seems to have disappeared, possibly because that huge impact “It turned upside down so that its hot internal contents ended up outside and its heat quickly radiated into space. We need research to solve problems like these.”
It remains to be seen whether NASA can act quickly enough to build and launch a mission as complex as the one needed to study Uranus. Many astronomers are nervous about the rigidity of the schedule, even though there is a ray of light. In 2011, the National Academy of Sciences published its latest decade-long survey and urged NASA to focus first on a mission to Mars for the next 10 years to begin collecting rocks to return to Earth, and second place in a probe that would be sent to Mars. Europe, the icy moon of Jupiter, to see if it could harbor life. A decade later, the American robot rover Perseverance has already begun the previous task, while NASA’s Europe Clipper will be launched in 2024. “This shows that these deadlines can be met and that gives us hope,” he says. Fletcher.
It remains to be seen how plans for the Uranus mission go, although there is an intriguing coda in the history of the selection of the planet as the main destination. As a secondary candidate for a flagship mission for the next 10 years, the National Academy of Sciences has recommended that a spacecraft be sent to Enceladus. This little moon of Saturn behaves in an amazing way. It throws organic-rich water plumes into space, making it an ideal sampling candidate for microbes or other primitive life forms that could exist on the small moon.
A mission to Enceladus shares many of the complexities that Bedevil plans for any mission to a distant ice or gas giant. However, it also binds remarkably to the proposed probe at Uranus. Enceladus was discovered in 1789, no more and no less than a figure than William Herschel.
The British astronomer of German descent William Herschel. Photography: Stock Photo / Getty Images
Herschel’s discovery was remembered
A memorial stone will be unveiled next month in the garden at 19 New King Street, Bath, to mark the exact spot where William Herschel rested his home telescope and first spotted Uranus. The event, on August 25, will be a key part of the celebrations, which began this weekend, to commemorate the 200th anniversary of the death of the German-born astronomer.
Herschel died on August 25, 1822, and the new exhibition in his home, now the Herschel Museum of Astronomy, will include his observation book in which he wrote notes of the night he first observed Uranus. time. There will also be a catalog of stars recorded by her sister Caroline, a professional astronomer in her own right, a prolific comet discoverer and …