According to exoplanetary astronomer Paul Wilson , if disk instability dominates the formation of planets, it should produce a wide number of worlds at large orders. The four giant planets orbiting at significant distances around the star HD provides observational evidence for disk instability.
Fomalhaut b , an exoplanet with a 2,year orbit around its star, could also be an example of a world formed through disk instability, though the planet could also have been ejected due to interactions with its neighbors. The biggest challenge to core accretion is time — building massive gas giants fast enough to grab the lighter components of their atmosphere. Recent research on how smaller, pebble-sized objects fused together to build giant planets up to times faster than earlier studies.
In , researchers Michiel Lambrechts and Anders Johansen from Lund University in Sweden proposed that tiny pebbles, once written off, held the key to rapidly building giant planets. Levison and his team built on that research to model more precisely how the tiny pebbles could form planets seen in the galaxy today.
While previous simulations, both large and medium-sized objects consumed their pebble-sized cousins at a relatively constant rate, Levison's simulations suggest that the larger objects acted more like bullies, snatching away pebbles from the mid-sized masses to grow at a far faster rate. As scientists continue to study planets inside of the solar system, as well as around other stars, they will better understand how Earth and its siblings formed. Join our Space Forums to keep talking space on the latest missions, night sky and more!
And if you have a news tip, correction or comment, let us know at: community space. Nola Taylor Tillman is a contributing writer for Space. She loves all things space and astronomy-related, and enjoys the opportunity to learn more. The atmosphere also protects us from incoming meteoroids, most of which break up before they can hit the surface. Earth is composed of four main layers, starting with an inner core at the planet's center, enveloped by the outer core, mantle, and crust.
The inner core is a solid sphere made of iron and nickel metals about miles 1, kilometers in radius. There the temperature is as high as 9, degrees Fahrenheit 5, degrees Celsius. Surrounding the inner core is the outer core. This layer is about 1, miles 2, kilometers thick, made of iron and nickel fluids. In between the outer core and crust is the mantle, the thickest layer.
This hot, viscous mixture of molten rock is about 1, miles 2, kilometers thick and has the consistency of caramel. The outermost layer, Earth's crust, goes about 19 miles 30 kilometers deep on average on land. At the bottom of the ocean, the crust is thinner and extends about 3 miles 5 kilometers from the seafloor to the top of the mantle.
Like Mars and Venus, Earth has volcanoes, mountains, and valleys. Earth's lithosphere, which includes the crust both continental and oceanic and the upper mantle, is divided into huge plates that are constantly moving. For example, the North American plate moves west over the Pacific Ocean basin, roughly at a rate equal to the growth of our fingernails.
Earthquakes result when plates grind past one another, ride up over one another, collide to make mountains, or split and separate. Earth's global ocean, which covers nearly 70 percent of the planet's surface, has an average depth of about 2.
Almost all of Earth's volcanoes are hidden under these oceans. Hawaii's Mauna Kea volcano is taller from base to summit than Mount Everest, but most of it is underwater. Earth's longest mountain range is also underwater, at the bottom of the Arctic and Atlantic oceans. It is four times longer than the Andes, Rockies and Himalayas combined. Near the surface, Earth has an atmosphere that consists of 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases such as argon, carbon dioxide, and neon.
The atmosphere affects Earth's long-term climate and short-term local weather and shields us from much of the harmful radiation coming from the Sun.
It also protects us from meteoroids, most of which burn up in the atmosphere, seen as meteors in the night sky, before they can strike the surface as meteorites. Our planet's rapid rotation and molten nickel-iron core give rise to a magnetic field, which the solar wind distorts into a teardrop shape in space.
The solar wind is a stream of charged particles continuously ejected from the Sun. When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.
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This latest supercontinent broke apart million years ago, eventually settling on the configuration that we know today. See graphics from Geology. Since that time, a mere blip on the geological time scale , all the events that we consider to be "recent history" took place. The dinosaurs ruled and then died, mammals achieved ascendancy, hominids began to slowly evolve into the species we know as homo sapiens, and civilization emerged.
And it all began with a lot of dust, fire, and some serious impacts. From this, the Sun, Moon, Earth, and life as we know it were all created. Explore further. More from Astronomy and Astrophysics. Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page.
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