Imagine a world where the sun is high in the sky for 21 years and then doesn’t appear at all for another 21 years, a planet lying on its side, so that sometimes it almost rolls forward in its orbit around the sun and sometimes it rotates in the direction opposite to its orbit – and on which, incidentally, it is impossible to orient, because the magnetic field is completely chaotic.
So it is on Uranus. The second outermost planet in the solar system differs in a number of areas from all others. For decades, astronomers have wished they could study it more closely.
Now it finally seems that their dream will come true. In a new one report The US National Research Council (NRC) recommends space travel to Uranus as NASA’s flagship expedition in the 1930s. The idea is to send a satellite and put it in orbit around the planet for several years, while a measuring probe is to dive deep into the dense atmosphere.
The findings should teach us more about our planetary system and solar systems elsewhere in the Milky Way, where Uranus-like planets have been shown to be common.
However, NASA technicians have a lot to do, because the spacecraft must be ready for departure in the early 1930s. If it fails, we are forced to wait decades for the next possibility.
Thirty-six years since the last visit
The journey to Uranus becomes one of the longest in the history of space travel. Namely, Uranus orbits 2.88 billion kilometers from the Sun, almost 20 times farther than Earth.
Therefore, Uranus is also an icy planet. Like Neptune, the outermost planet in the solar system, it is called an ice giant. Uranus weighs 14.5 times more than Earth and is four times larger in diameter.
Only once before has a spacecraft approached Uranus. It was when Voyager 2 crossed the planet at a distance of 81,500 kilometers in 1986.
Since then, astronomers have only been able to study the planet from a distance, and scientists have demanded better observations than the data provided by simple Voyager instruments.
The probe actually only determined the ice giant’s color, size, temperature, density, and magnetic field. More than that is needed before scientists can solve the planet’s many mysteries.
The decision on a new expedition to Uranus cannot wait any longer.
It will take seven to 10 years to build the spacecraft, which has been named Uranus Orbiter and Probe. This means that it will only be possible to eliminate it in the first half of the 1930s.
At that moment, Jupiter aligns with Uranus, which is crucial for the expedition. With his gravity, Jupiter can launch the spacecraft towards its distant target, so that the journey only lasts twelve years. The maneuver also saves a lot of fuel and offers additional space for tools.
The next opportunity will only come in the middle of the century, when the planets will line up again.
When the spacecraft arrives on Uranus, it will encounter a world that one could say shouldn’t really be there. The location of the ice giant so far away in the solar system is a mystery in itself.
Researchers believe it is highly unlikely that Uranus and Neptune they were born in their current orbits because there was not enough matter that far away in the young solar system.
The prevailing theory is that the ice giants formed closer to the Sun and were then ejected further out into the solar system when the gas giants Jupiter and Saturn positioned themselves in their current orbits.
An orbiting satellite could test this theory by measuring the elemental content of Uranus and comparing the results with Jupiter And Saturn.
Astronomers believe that Uranus is made up of a core of iron, nickel, and rock, and that on top is a thick mantle of ice, made up of water, ammonia and methane.
The atmosphere is made up mostly of hydrogen and helium, but it also contains a small percentage of methane, which gives the ice giant its blue color, as methane reflects blue sunlight back into space.
Uranus has two rings around the equator and 27 moons. The five largest probably formed at the same time as the planet, while the others may have been captured later by the gravitational field of Uranus.
The whole system would seem normal were it not for one thing: Uranus has ended up on its side, so that the axis of rotation is almost in the same plane as its orbit around the Sun.
It takes the planet 84 Earth years to complete one revolution around the sun, resulting in oddly long seasons. Seen from one point on the planet, the sun is up for 21 Earth years, which is a long day. For the next 21 years, a 17-hour day alternates between night and day, and for the next 21 years it is a long, dark night.
The collision may have toppled Uranus
How Uranus got its particular rotation is uncertain, but the main theory is that the ice giant was hit by a planet about twice the mass of Earth during the infancy of the solar system.
Such a collision would be powerful enough to bring down Uranus. The ice giant no longer shows traces of the collision, but perhaps the next expedition will find out if any moons contain material from the collision.
The collision could also provide answers to another of Uranus’ mysteries, namely that the planet is colder than Neptune. It shouldn’t be, since Neptune gets 40 percent less sunlight than Uranus.
The reason could be that the great collision nearly pierced Uranus, so that most of the heat from the core was released at once.
Another theory is that horizontal rotation makes the poles warmer than the equator, which may have increased the planet’s heat loss. A third hypothesis is that the core of the ice giant is still hot, but that an unknown layer between the mantle and the atmosphere prevents the release of heat.
Indeed, all three of these theories are pure speculation, but an orbiting satellite could likely solve the mystery.
The same goes for the biggest mystery that Uranus hides inside: the chaotic magnetic field.
In the main field, the magnetic poles have been shifted 59 degrees from the planet’s axis of rotation, which corresponds to the north pole of the Earth which is in Europe. At the same time, Uranus has several strong regional magnetic fields.
Both sides are in stark contrast to the magnetic fields of the four rocky planets of the solar system and the two gas giants, where the magnetic axis is close to the axis of rotation and where the fields resemble the well-ordered fields of a magnetic bar.
Packed with tools
To solve the many mysteries, Uranus Orbiter and Probe will bring with him a variety of scientific instruments. The details of the spacecraft may change in the coming years, but the overall design of the satellite and measurement probe is in place.
Among other things, the satellite has been equipped with four gyroscopes, which will be used to investigate the internal structure of Uranus. This is done with the help of gravity measurements, in which gyroscopes record how changes in the ice giant’s gravitational field affect the satellite’s orbit.
A magnetometer will map the ice giant’s chaotic magnetic field, while the satellite’s camera will photograph Uranus’s surface and cloud cover.
A dramatic highlight will be when, upon arrival, the satellite drops the measuring probe, which will plunge into the atmosphere.
The probe contains a package of sensors that measure temperature, pressure and density. At the same time, a mass spectrometer determines the exact content of hydrogen, helium and methane in the atmosphere.
The well-equipped expedition will undoubtedly provide a variety of data, which will teach us a lot about Uranus. Furthermore, we will also learn more about other solar systems.
Astronomers have now discovered over 5,000 planets around alien stars, and up to 40% of them are ice giants. Therefore, it is important to find out how they are formed and what function they play in the development of solar systems.
This way we can also find out how similar ours is solar system they are others and therefore how special our home in the universe is.
