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6

Consider a planet with effective temperature $T$ radiating as a blackbody, emitting a total luminosity $L=4 \pi \sigma R^2 T^4$. At distance $a$ the power per square meter will be $$P = \frac{L}{4\pi a^2} = \sigma \left(\frac{R}{a}\right)^2 T^4.$$ If we demand a sun-like energy flow of $P_{required}$, we get a necessary temperature $$T=\left[\frac{P_{...


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Partial problem with Anders' answer: 730K is a "hot Jupiter", which I think are usually kept hot by stellar insolation, which would also heat the proposed moon. Removing that heat-source: Shortly after Jupiter formed, assuming it orbited at its present distance from the Sun, at some point it might have had a surface radiation temperature of 730K, ...


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It seems like there are two questions here: 1: How could a moonless planet capture a single asteroid into a closed orbit around the planet? In a 2-body orbital system, a moonless planet couldn't capture an asteroid. The asteroid would leave the planet's gravity well with the same relative speed that it entered. However, a sun/planet/asteroid system is a 3-...


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At zeros order such assumption might be made, but a powerlaw relation is more common and accepted. Also a protoplanetary disk is more complex as is the planet formation process which may include radial migration of the protoplanets. So the mass $m(r)$ available at a distance $r$ might not be exactly representative for the planetary mass found at that ...


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For those who wanted a complete mathematical answer and were also dissatisfied with the previous answers, see answers to How high can a mountain possibly get? in Earth Science SE. I adjusted a few numbers in the linked equation to more accurately reflect compression strength and density of granite ($2.5 \times 10^8$ and $2.75 \times 10^3$ respectively). A ...


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For inner planets (Venus and Mercury) the best time for observation is west or east elongation. During east elongation (planet can be seen in the evening) the planet is located "in front" of the Sun in the sky. The planet is seen the best in winter and spring because the Sun's declination is increasing and the planet gets to be before Sun, in place ...


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