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Yes. Two bodies in orbit around each other will inevitably collide. The reason for this is that the system will give off energy in the form of gravitational waves. This effect is commonly cited in binary neutron star systems, where the two stars are isolated and close together. One of the most famous of these systems is the Hulse-Taylor binary. The time it ...


5

There are many planets known which have orbits longer than the longest exoplanet orbital periods found by Kepler. These planets were discovered using the "doppler wobble" or radial velocity technique. The plot below (a few months out of date now) shows many planets orbiting with similar periods to Mars and Jupiter. The red points we discovered by transits ...


4

Is it possible to create the proposed system of satellites? Yes (in theorey). Hierarchical multiple systems (like the one proposed in the OP) tend to be stable if the periods differ by $\sim 5$ or more and the orbits are near-circular. So, such a system could be stable. A slight problem may be the commensurability of the periods (the fact that their ratios ...


3

For bodies small enough to be non-spherical, the mass is relatively low (as an example, Rosetta's bounces took a long time - it touched the surface at 15:34, 17:25 and 17:32 GMT comet time) but the centre of mass is still the point the lander will orbit. So a chaotic orbit is not a problem here What will be problems are: trying to arrange for the ...


2

Even 100 meter NEOs could cause significant damage, and there are far more of them. LSST will be able to detect objects as faint as 24.5 in magnitude in a 30s visit, enabling it to detect 140m NEOs as far away as the Main Belt asteroids. [...] During its survey of the sky, LSST can find 90% of the PHAs over 140 meters in diameter. Earth is 1 ...


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A simple argument why the gas cloud orbiting the Protosun formed a disc is as follows. There are two characteristic properties of this gas cloud: its total energy and its total angular momentum. While the angular momentum is conserved, the energy it not: radiation reduces the fluid temperature and hence the energy. So eventually, the cloud settles to a ...



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