Planetary models are incredibly complex, requiring scientists to account for everything that happens to a growing planet on timescales spanning a few days to millions of years. In the past, astronomers would simplify their models of colliding objects by assuming that all of the material from both the impactor and its target perfectly merged into a single object — an unrealistic expectation, since at least some pieces would most likely be flung into space and lost. But because computers of the past were less powerful than those today, scientists were forced into the simplification.
In the past decade, however, improvements in computational power have allowed researchers to begin studying more-realistic collision scenarios. Now, scientists can model so-called hit-and-run collisions , where two bodies scraped each other in passing, or even the total annihilation that could occur when two planetary embryos slammed together. These imperfect "dirty collisions" not only affect how large planets grow to be but also help to explain their orbits.
Not to change the topic here:
What Makes a Planet and How Many Are There in Our Solar System?
What makes a space object a planet? How many are there actually in our solar system? Let's find out.
How many planets are there in our solar system? 9? 8? 12? More? The answer might actually surprise you.
Here we explore the answer to this apparently simple question and take a quick tour of the main primary planets of our home solar system.
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What is a planet? An enormous chunk of stuff (rock or gas), roughly spheroidal in shape that orbits a star and may or may not have a moon, right?
While this is in part true, there are some issues with such a simple definition. What about asteroids? When does an object become large enough to be considered a planet?
Why are Venus and Mercury planets (according to current classifications) but not Pluto? As it turns out, the reasons are pretty straight forward.
It's an asteroid! No, it's the new smallest dwarf planet in our solar system - CNN
(CNN) A large asteroid could be reclassified as a dwarf planet -- which could make it the smallest in the solar system -- after new research revealed its shape, astronomers said on Monday.
Lessons from scorching hot weirdo-planets
Illustration of a hot Jupiter planet in the Messier 67 star cluster. Hot Jupiters are so named because of their close proximity — usually just a few million miles — to their star, which drives up temperatures and can puff out the planets.
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Hot Jupiters were the first kind of exoplanet found. A quarter-century later, they still perplex and captivate — and their origins hold lessons about planet formation in general.
In 1995, after years of effort, astronomers made an announcement: They'd found the first planet circling a sun-like star outside our solar system. But that planet, 51 Pegasi b, was in a quite unexpected place — it appeared to be just around 4.8 million miles away from its home star and able to dash around the star in just over four Earth-days. Our innermost planet, Mercury, by comparison, is 28.6 million miles away from the sun at its closest approach and orbits it every 88 days.
Were you following this:
Spot six planets in the sky this week: Mercury, Mars, Uranus and more | New Scientist
THE coming week is a great time to look for planets. A new moon on 28 October means no moonlight and, with the exception of Neptune , every planet is visible at some point in the coming days. Even distant Uranus, which at 8 pm GMT on 27 October will be a mere 2.8 billion kilometres away.
Venus is the easiest to find, with an apparent magnitude of -4.6. In the magnitude scale, objects with lower numbers are brighter. It is close to the sun, …
A Churning 'Molten Blob' of Planet May Be Easier to Find. Here's Why. | Space
The smaller a planet , the more difficult it is to spot — which is frustrating for scientists hoping to find Earth-like worlds.
That's why a team of researchers set out to determine what planetary traits would make a world a little easier to identify. Their analysis suggests that molten worlds with atmospheres full of water or carbon dioxide will be more easily observed by instruments that will be available to scientists soon.
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And that's a boon for observers: If two planets have the same mass but one has a magma ocean and the other doesn't, it could be about 5% larger across, making it easier to spot. And a molten world is more likely to be leaking water and carbon dioxide from that liquid rock out into a developing atmosphere.
Those two molecules are easily released by molten rock, but they are also the sort of thing that future telescopes like NASA's James Webb Space Telescope are being designed to detect. Webb won't be able to study Earth-size planets around stars like our sun, but it should be able to analyze those around smaller M dwarf stars.
A NASA report finds planetary contamination rules may be too strict | Science News
Some policies for protecting the moon, Mars and other places in the solar system from contamination by visiting missions may be too strict.
At least one astrobiologist cautioned, however, against relaxing current guidelines too much. Spacecraft landing in areas deemed sterile could still contaminate areas that are potentially interesting for astrobiology, says John Rummel of the SETI Institute in Mountain View, Calif. If a lunar probe crashes on the moon's surface, "you end up with material that's taken into the lunar atmosphere and deposited in the cold traps at the south and north anyway," he says. "You don't even have to land at the south pole to affect [it]."
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Astrobiologist Alberto Fairén of Cornell University welcomes the possibility of adding nuance to the "extremely restrictive" protection guidelines for Mars. He and colleagues recommended a few high-priority astrobiology zones in Advances in Space Research in March, including lakes of liquid water possibly hidden under ice sheets ( SN: 12/17/18 ).
A tour of the solar system: I.F.
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