As scary as an incoming asteroid may sound, it doesn’t have to mean the end of the world. It’s true space rocks sometimes collide with our planet, as happened with devastating effect 66 million years ago when a massive impact wiped out the dinosaurs. But such events are the exception rather than the rule. By astronomical standards, Earth is a very small target. Asteroids move on precisely determined orbits, so the vast majority of them simply whiz past the planet at a safe distance. Such encounters are a good thing for astronomers because they give them a chance to study asteroids at close range, and these small, rocky objects can tell us a lot about the origin and evolution of the Solar System. When the first asteroids were discovered, they were all found to lie in an ‘asteroid belt’ between the orbits of Mars and Jupiter. It’s still true today that most known asteroids are located in this region.
Asteroids can be thought of as miniature planets, a few metres to several thousand metres in size, which move on a range of orbits around the Sun in much the same way planets do. All these orbits have a similar basic shape: a kind of distorted circle called an ellipse. The point on the ellipse that’s furthest from the Sun is called aphelion, while the closest is perihelion. In the case of a planet like Earth, the difference between perihelion and aphelion is very small, which means that the orbit is almost circular. Asteroid orbits, on the other hand, can be much more eccentric than this, and some of them can actually have a perihelion inside Earth’s orbit and an aphelion outside it. In other words, their orbits around the Sun overlap with our own planet’s.
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Denne historien er fra Issue 178-utgaven av How It Works UK.
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RESCUE IN SPACE
Fortunately, space emergencies are a rare occurrence, but astronauts and space agencies need to be prepared for any eventuality that might arise
NEANDERTHAL LIVING
Why our prehistoric cousins were pioneers, not clueless apes
BUILDING ONE WORLD TRADE CENTER
One World Trade Center rose from the ashes of the Twin Towers. Now, as the tallest building in New York City, it looks to the skies and the future. Here's how this sustainable and secure record-breaker was built
BECOME A SMARTPHONE SCIENTIST
Amazing tips and tricks to transform your smartphone into a bug-finding, star-spotting, data-gathering device
LIFTING THE LID ON ANTARCTICA
What was the coldest continent like without ice?
URBAN WILDLIFE
How wild animals have evolved to thrive alongside humans in towns and cities
WHAT IS SUNBURN?
How solar rays can leave us red, sore and irritated
ALL ABOUT FAT
Fat is a complex, active organ. Here's how genetics, evolution, lifestyle and diet dictate how much we have beneath our skin
The Space Force is launching lasers into orbit
The Space Force aims to better pinpoint the location of Earth's true centre using lasers on GPS satellites, slated to launch in 2025. A set of Laser Retroreflector Arrays, or LRAS, will be installed onto two GPS III satellites, SV9 and SV10, as part of NASA's Space Geodesy Program. The lasers are designed to make precise sub-centimetre measurements using a technique called Satellite Laser Ranging, which will allow researchers to more accurately determine Earth's centre.
Eating too much sugar may accelerate cellular ageing
A nutrient-rich diet with few added sugars may slow the rate of biological ageing in women. Scientists found that middle-aged women who ate more foods packed with vitamins, minerals and antioxidants had 'younger looking' cells than those who consumed less nutrient-rich diets.