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Planets are usually rotating, and so you can't time two passes over a single geographical feature to time an orbit. But you can time successive sunrises to get a good approximation of the orbital period, or some other astronomical coordination between the planet's limb and the celestial sphere. From this answer: Starting with $$T = 2\pi\sqrt{\frac{a^...


8

So the main thing of interest in this post seems to be angular resolution. You're after objects that are relatively bright and small. Angular resolution increases linearly with aperture size. However, you don't necessarily need a giant light-bucket of a telescope to achieve high resolution. You can achieve some impressive resolution through use of ...


5

I got curious and read this, it makes plenty of sense to me. http://www.jamesoberg.com/sts88_and-black-knight.pdf The suggestion is that many of the photos are really of a bit of space debris from STS-88. The author explains that the hype is just that, hype. The intense passion to want to believe so badly that this is something alien, clouds any type of ...


5

To disprove a hypothesis, you need only one counter-example. The solar system is already one. Planetary semi-major distances do not follow a simple power-law rule. A fraction of exoplanetary systems possesses resonant chains of planetary orbits (similar to the Laplace resonance for the Galileian satellites), which then give semi-major axes that follow a ...


4

I massaged some raw numbers from https://nssdc.gsfc.nasa.gov/planetary/factsheet/ For each body-Sun pair the velocity of the Sun is the velocity of the planet times the ratio of the masses since they orbit around their center of mass. Eclipse depth is just the ratio of diameters. Jupiter results in the largest velocity by far, thought the amplitude of the ...


3

Wikipedia has a list of directly imaged exoplanets. There are 22 of them and the latest one listed is HIP 65426, in 2017. It's image can be found here. Another example is GU Piscium b, imaged in 2014: NASA's Exoplanet Archive has a list of 46 directly imaged planets. To show them, enter "imaging" in the box at the top of the Discovery Method column. I ...


3

I don’t know about this mission’s planning, but there are some common considerations: To maximize the observing time, you’d like an orbital plane that’s perpendicular to where you’re looking. That way you can keep looking one way, without Earth getting in the way. Not only do you lose observing time if Earth is in the way, you also (usually) have to either ...


1

A small planet may hold gas only if it is a very cold planet far away from its sun. But the gas would be a liquid or frozen, too cold to sustain life. But an atmosphere should be gaseous, not liquid or solid. The thermal movement of the gas atoms should be so slow that they could not escape the planet's gravity.


1

We do not have to look very far from Earth to find evidence for alternative UV absorbers. Something seems to be present in the atmosphere of Venus. While the UV absorber is not yet known and requires more study of the Venusian atmosphere to find out, a couple of ideas published in journals suggest possible alternatives on Venus or elsewhere. Ferric ...


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