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1

Yes, I believe this is the internal lens reflection. Lens reflections have hexagonal shape, and if you look closely, it somewhat resembles this shape. Also, see other answers in the comments. Internal lens reflection happens because the lenses don't have 100% transmission. This often happens when taking bright objects, like Sun in your example.


8

The Sun doesn't substantially impact radio observations during the day, because radio telescopes operate at long wavelengths. In general, light at longer wavelengths scatters less than light at shorter wavelengths, and so visible light from the Sun scatters much more than radio waves from the Sun.$^{\dagger}$ The former effectively fills the daytime sky, ...


0

ProfRob gives a more detailed explanation of what a solar flare is in his answer to "What triggers a solar flare?" It helps a lot in distinguishing between CME's, eruptions, prominences and solar flares. There is a lot of confusion, even among space enthusiasts, between these phenomena. This is largely because images of prominences and CMEs always ...


2

I don't have an exact answer, too many factors are involved. If we consider Newtonian orbits, you can have a stable orbit as long as the perihelion is outside the Sun. But by getting closer to the Sun, two other effects start playing a role: tidal interactions and general relativity. I'm not an expert in general relativity, but I know that Mercury is already ...


3

Part One: Moons of other planets. The discovery of the Galilean moons of Jupiter in 1609-1610 proved that not everything had to orbit directly around one signel object. The discovery of the Galilean moons showed that objects could revolve around an object which revolved around another object. There was no way for all known objects to revolve directly around ...


1

Ancient Greeks already had measured the size of the Earth, the size and distance of the Moon, and the size and distance of the Sun. They got the wrong values, but their reasoning was sound—it’s only because their measurements were not that great that they were off in their results. But eventually, someone would have gotten the right measurements, and ...


1

I always think the strongest demonstration that the earth moves is using a Foucault Pendulum at different latitudes. If you combine this with Eratosthenes measurement of the circumference of the earth, you at least have a solid argument that the earth is round and spinning. It's not all the way to Heliocentric, but starts getting things close and doesn't ...


3

Stand on dune in a desert. Take a handfull of sand, all crushed from the same rock. Now close your eyes, Hold your hand up to the wind, let the wind blow all but one of the grains of sand, somewhere. Wait 2 years. Now go and find the other grains of sand that you dropped. It should be easy, right? They have identical composition as the sample you have. They ...


1

Disclaimer This not (yet) a full answer, since I only focus on approaching part 1 of the question, namely the calculation of the dielectric constant of the corona. Dielectric constant of the corona The Sun's corona ... extends millions of kilometres into outer space and is most easily seen during a total solar eclipse [...] measurements indicate strong ...


31

Here are the problems/issues: Most stars are born in clusters/associations but a cursory investigation of cluster demographics with age reveals that the vast majority of clusters do not survive to old age. The majority either are never gravitationally bound to begin with or become unbound in the first 10 Myr. The Sun was likely born in a cluster of $10^3-10^...


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It could be anywhere in the Galaxy or even (unlikely) have left the Galaxy. The kinematics of freely orbiting objects in the Galaxy are heated - that is, the velocity dispersion of objects increases with time. For objects of age of 4 billion years we might expect a dispersion of about 10 -15 km/s in each velocity coordinate. That's about 10-15 pc/Myr. So in ...


2

The further the moon is from the sun the easier it is to see. There are two reasons. Firstly, when it is close to the sun it gets lost in the glare from the sun. The sky close to the sun is very bright, and there isn't enough contrast to see the moon against the bright sky. Secondly, as the moon gets further from the sun, more of the illuminated side of ...


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