Our Solar System You Are Now Leaving Earth
With eight planets, five dwarf planets, at least 146 moons, more than half a million known asteroids and about 4,000 comets, the solar system is more crowded than you might think. Come join us on our cosmic voyage. And don't forget to turn on the Sound.
"The solar system is an insignificant bunch of dust. It also happens to be where we live." (Gene Shoemaker)
Our solar system is four-and-a-half billion years old. Science is only gradually gaining insights into its endless expanse. NASA's New Horizons spacecraft recently paid a visit to Pluto. For the first time since its discovery 85 years ago, mankind now knows what the planet looks like. This tour through the solar system takes you to Pluto and beyond.
By Milky Way standards, the sun is a perfectly normal, average star. With surface temperatures of about 5,000 degrees Celsius (9,032 degrees Fahrenheit), and up to 15 million degrees Celsius at its core, the sun derives its energy from the process of nuclear fusion. Hydrogen atoms melt into helium, fueling the solar fire.
The good news is that this will continue for about another 5 to 6 billion years. The bad news is that at the end of this period, the sun could expand to the point that it will swallow Earth.
From the hottest place in the solar system, we now go to somewhat cooler realms. The first stop is a planet of extremes.
Mercury's surface, with its many craters, resembles the surface of Earth's moon. There is tons of water ice in craters on the planet's poles.
From Mercury, we continue to our cosmic neighbor, a true beauty, but one that packs a punch.
The planet's dense atmosphere wouldn't be much fun for human beings. It consists of 96 percent carbon dioxide, with air pressure that is 90 times as high as on Earth's surface. If you were hoping to travel in comfort here, we hope you brought a diving bell along. Your equipment should also be good enough to withstand the pressure.
The average ground temperature on Venus is 462 degrees Celsius. At those temperatures, metals like lead become liquid. Sulfuric acid rain and volcanic activity also help make Venus a pretty unpleasant place.
So-called Aten asteroids, of which more than 900 are known, can be found on the route toward Earth. In principle, some of them could even cross Earth's orbit and pose a threat to the planet. But there is currently no evidence that any specific asteroid is about to crash into Earth anytime soon.
Astronaut Thomas Reiter Peers at Earth from Space:
When it comes to land surface, human beings are of course deeply familiar with their home planet. This applies to the 7.2 billion people who explore their world on the ground every day, the three to six residents of the International Space Station and countless earth observation satellites, which keep a constant eye on all signs of life.
Thomas Reiter Looks Skyward to the Moon
More than three years later, in July 1969, two human beings landed on the moon for the first time, as part of NASA's Apollo 11 mission. A total of 12 people -- all men, and all Americans -- have set foot on the moon. But that happened more than 40 years ago. Johann-Dietrich Wörner, head of the European Space Agency (ESA), is currently campaigning for an international, manned moon base. Let's see where that leads.
"Don't tell me that man doesn't belong out there. Man belongs wherever he wants to go -- and he'll do plenty well when he gets there." (Wernher von Braun, the famous German-American aerospace engineer who designed the Saturn V launch vehicle that propelled the Apollo spacecraft to the moon.)
Better shake off that dust! The nearest dry cleaner is a long, long way away. On the way to Mars, our flight passes the so-called Apollo asteroids, of which more than 7,000 are known. Some of them could cross Earth's orbit, but there is currently no indication of an impending collision. Let's get a move on it. There's nothing to see here.
When Will Men be able to travel to Mars?
There is two-thirds less gravity on Mars than on Earth. Even with a bulky space suit on, you could still jump three times higher than you could at home. If your old gym teacher could only see!
The Olympus Mons on Mars is the tallest volcano in the solar system. The mountain, known as a shield volcano, is about 25 kilometers high, or almost three times as high as Earth's Mount Everest. The Red Planet also has the deepest canyons in the solar system. The Valles Marineris, for example, is steep and runs up to seven kilometers deep.
Mars is a popular destination for research spacecraft from Earth. The Soviet Union achieved the first flyby in June 1963, with Mars 1. In July 1965, the US' Mariner 4 spacecraft delivered the first images of Mars, from a distance of about 10,000 kilometers. The Soviets accomplished the first successful landing in December 1971, with their Mars 3 craft. In December 2003, the Europeans made a hard landing on Mars with the Beagle 2. Meanwhile, the Mars Express has been in orbit since December 2003, together with four other active spacecraft.
On the way to the edge of the solar system, our route now passes through the asteroid belt. It contains half a million known asteroids, and more are constantly being added to the list. These rocks of various sizes are remnants from the early days of the solar system. Rapidly growing Jupiter once ensured that they could not come together to form a planet. This is one reason asteroids are so interesting to scientists -- as a sort of cosmic time capsule.
Asteroids are constantly colliding with each other or -- if they are thrown out of their orbits -- with planets. Asteroids have collided with Earth before, sometimes with dramatic consequences. We don't have to worry about an asteroid entering a collision course with Earth in the near future, but sooner or later it will happen again - an eventuality we are still poorly equipped to deal with. NASA is thinking about a manned asteroid mission. But so far only thinking about it.
There is a very special dwarf planet orbiting within the asteroid belt.
The goal of NASA's Dawn spacecraft is to unlock Ceres' secrets. It has been orbiting Ceres since March 2015 and has already sent back large numbers of images.
We are now about to enter the region of the so-called gas planets. The biggest one is the next station on our journey through the solar system.
In addition to the planet itself, Jupiter's moons, of which there are at least 50 (more than any other planet), are also of interest to scientists. For instance, they believe that there is an ocean of water under thick ice on giant Ganymede, which is larger than Mercury.
The Jupiter moon Europa, a veritable flying snowball, is also fascinating to scientists, who speculate that simple life forms may exist there as well. The conditions for life there are not bad, prompting repeated discussion about a possible Europa landing mission. In 2022, ESA plans to launch its spacecraft Juice, with which it hopes to at least conduct a flyby of the Jupiter moon.
"Can we actually "know" the universe? My God, it's hard enough to find your way around in Chinatown." (Woody Allen)
As on Jupiter, there are storms raging on Saturn of almost unimaginable dimensions. They spin through the atmosphere for months, generating giant bolts of lightning 10,000 times stronger than those found on Earth. And like Jupiter, Saturn appears to have a solid core.
Scientists are also interested in Saturn's moons, the biggest of which, Titan -- like Jupiter's moon Ganymede -- has a larger diameter than Mercury. In January 2005, ESA's Huygens lander managed to gather data for 70 minutes on the moon's surface, which is usually concealed by a thick atmosphere. Titan also has giant hydrocarbon seas. It's a fascinating but uncomfortable world.
No one has ever seen Uranus's small core beneath its atmosphere. The gas planet has a uniquely tilted rotational axis, probably the result of a collision long ago. It's also pretty cold there, so let's keep going!
There are seasons in Neptune's atmosphere, but they last 40 years.
Neptune's Triton moon is considered the coldest place in the solar system visited to date. Temperatures as low as minus 223.5 degrees Celsius have been measured on Triton, where ice geysers spew nitrogen.
Given Pluto's location far out in the solar system, light from the sun is very weak on the dwarf planet. It takes more than four-and-a-half hours to reach it, which is how long the trip would take if one were to fly there at the speed of light.
Astronomers know even less about a structure called the Oort Cloud. They believe it contains an unimaginably large number of objects made of rock and ice, left behind when the solar system was created. No one has actually observed the cloud, but many believe it exists, as a sort of garbage dump of the solar system. Gravitational effects occasionally propel objects from the Oort Cloud into the inner solar system, where they become long-period comets.
The edge of the Oort Cloud could be 1.6 light-years away from Earth, or almost half the distance to the nearest star, Proxima Centauri. It is significantly smaller than the sun and has only an eighth of its mass. Traveling at the speed of light, it would take more than four years to reach Proxima Centauri. Put differently, if the distance between the sun and Earth were only one meter, Proxima Centauri would be about 270 kilometers away. But we'll save this part of the trip for another journey.
"Today's science fiction is tomorrow's science fact." (Science fiction writer Arthur C. Clarke)
Author: Christoph Seidler. Videos: Anne Martin. Editor: Holger Dambeck. Research and fact-checking: Almut Cieschinger, Maximilian Schäfer. Copyediting: Sarah Omar. Design: Hanz Sayami. Coordination: Jule Lutteroth. Translation: Christopher Sultan.