# Tag Info

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An astronaut on the moon could only be seen by reflecting the Sun's light towards Earth. Stars on the other hand emit their own light. To first order, the amount of flux incident upon the Moon from the Sun is the same as that at the Earth - about 1.4 kW/m$^{2}$. Let us assume that an astronaut is perfectly reflective and that the relevant reflective area ...

5

The Sun's luminosity is stable to 0.1% - it varies slightly in response to, or associated with, levels of solar magnetic activity. This variation would not be perceptible and is completely outweighed by the $\pm 3.4$% variation caused by the non-circular orbit of the Earth (the Sun is closest in January). Obviously, if you live in the northern hemisphere, ...

4

Short answer: The Sun will lose about half of its mass on the way to becoming a white dwarf. Most of this mass loss will occur in the last few million years of its life, during the Asymptotic Giant Branch (AGB) phase. At the same time the orbital radius of the Earth around the Sun will grow by a factor of two (as will the outer planets). Unfortunately for ...

3

The resolved stars (those that can be seen as individuals) are all part of the Milky Way Galaxy (unless there are any interlopers that have been captured!). The distances to the next nearest galaxies of any size are more than 100,000 light years. Andromeda is 2 million light years away. Unless one goes supernova, there basically aren't any types of star ...

2

It would depend on what time the Earth started to spin around Michigan. There is no way to answer this without saying what time, time of year, and which century (or at least millennium) it happens. Edit: Hi Dayna. Thanks for the the time of year the Keweenaw Peninsula becomes the North Pole. One could be omniscient except for that and not know this. But we ...

2

Iron is mainly made or is the product of decays from nuclear processed material inside supernovae. As the Earth (and solar system) is around 4.5 billion years old, then the stars that manufactured the iron that is currently in the Earth's core died more than 4.5 billion years ago. Note that the solar system formed out of the gases that had been enriched by ...

2

A black hole (BH) never sucks anything in. 'Sucking' requires gas pressure, but a black hole only acts via its gravity. A non-rotating (=Schwarzschild) black hole attracts all massive objects, very much like the Sun attracts the planets. Yet, the planets are not falling into the Sun. This is because the planets move on near-circular orbits when the ...

1

I think it's a fun question, if impossible. The only way to turn Jupiter into a star that's even remotely practical is to add to it's mass. Ignoring brown dwarfs that are very limited in energy output, to get a red dwarf going, you'd need to add at least 75-80 or so Jupiter masses. (a bit more than 24,000 earth masses). You'd want to add a fair ...

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