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6

In short, you can't make a galaxy-mass ball of iron because there's no way to support the ball against the inward crush of its own gravity. First, it would collapse into a neutron star, but even neutron stars can't hold themselves up beyond about 2-3 solar masses. Your galaxy-sized object would collapse into a black hole. But we do see these! All massive ...


5

There are two possible reasons why a star would not be visible (even with the most powerful telescopes not yet invented), apart from the trivial (too far away, hidden behind screens of dust). It has too low a temperature. To not emit much in the visible part of the spectrum, a star has to be very cold indeed, at most a few 100K, when radiation is mostly in ...


4

All matter radiates (except if it's at absolute zero temperature), regardless of its composition (you got that of Mercury badly wrong). The most important form of radiation is the black-body radiation which only depends on the temperature of the material, but line emission and absorption may also be important (but depends on the composition and ionisation ...


3

When stars transition from the main sequence core Hydrogen burning to core Helium burning they can experience Hydrogen shell burning. However, when you burn the Hydrogen in the shell to Helium, it will fall on the core creating a hotter core where the radiation pressure from the Helium burning core will push the Hydrogen further out into the outer ...


3

Stars actually do this on their own, to an extent. The material inside a star (in some layers) does convect, and at certain points in the star's life, the material in the core can actually rise up and mix with the rest of the star. This might replenish some H and He in the core, but the main effect that can be observed is that the fusion products become ...


3

Sun-Earth distance: 1AU Earth-Jupiter distance (at the conjunction): 4AU So Lucifer will be four times farther than Sun when it is nearer (six times when it is farthest), and at the same time it is a thousand times smaller. This is approx 40 times more light than full moon concentrated in a tiny point on sky.


3

"White" stars are typically much brighter than Red stars, as both the "color & brightness" of a star are directly proportional to the temperature. The only reason there are "bright" red stars is that their radius is incredibly large. Note that the "color" of a star is directly linked to the temperature. The equation that best demonstrates this is the ...


3

White dwarfs start hotter when they are created (up to billions degrees Kelvin), but in the end, they end as black dwarfs, which only happens after a few billion years. As per the age of the universe, it is currently the assumption that there are no black dwarfs yet. Red giants are (on the surface) typically below 5000 K. Their core is up to a billion ...


3

First Weight and Mass are 2 different things. In everyday usage, the mass of an object is often referred to as its weight though these are in fact different concepts and quantities. Mass refers to the amount of "matter"(or in lay word stuff) in an object, whereas weight refers to the force experienced by an object due to gravity. We can calculate the Mass ...


3

Apart from the good reasons given in the other answers as to why a ball of iron in excess of about $1.4$M$_\odot$ cannot be stable, there is another reason. Namely, there is no way to form that much pure iron. Iron is produced in supernovae, but only a fraction of the matter expelled by a supernova is actually iron and there is no natural way to select is. ...


2

If you had a galaxy sized ball of iron the gravitational force emitted would be immense, and without any force pushing out from it the ball would collapse into itself to form a black hole. In stars such as the sun (main-sequence stars) the outward force of nuclear reactions taking place in its core keep it from collapsing into itself. However, with a ball of ...


2

Our sun will eventually become a white dwarf. A star 10 times it mass will become a neutron star. A star 100 times the mass of the sun will become a black hole. So if 100 stars came together into one mass, it would collapse into a black hole. It is currently believed that a super massive black hole (at least 1000 times the mass of our sun) is at the center ...


2

The star reaches a critical mass and ignites, blowing away the surrounding material. (OP emphasis) I think the misunderstanding is that it's not that explosive when the star "lights up". The process is in some sense continuous, so the nuclear reactions start slowly and gradually increase in strength as the star continues to contract, grow, and heat up ...


2

I'm going to start by going over the Pauli Exclusion Principle. Basically, it says that two fermions (in this case, electrons) can't be in the same quantum state. To expand: No two electrons in an atom can share the same numbers for their four quantum numbers. What are quantum numbers? Well, I'll admit that Wikipedia describes them a lot better than I can, ...


2

In reality, Jupiter doesn't have nearly enough mass to initiate stellar ignition or sustain it if we could somehow start it going. Even the smallest star would require on the order of some 80 to 90 times the mass of Jupiter just to put out a faint red glow. Even to become a brown dwarf proto-star, Jupiter would require a mass increase on the order of at ...


2

Ignoring the impossibility of Jupiter going solar: Assume that Jupiter turns into duplicate of the Sun in terms of energy output. Energy transmitted to the earth follows an inverse-square law. Since Jupiter is, at best, 4 times farther from the Earth than the Sun, Jupiter will supply the Earth with, at most, 1/16 the energy that the Sun supplies, for an ...


1

Before I start, I'll admit that I've criticized the question based on its improbability; however, I've been persuaded otherwise. I'm going to try to do the calculations based on completely different formulas than I think have been used; I hope you'll stay with me as I work it out. Let's imagine that Lucifer becomes a main-sequence star - in fact, let's call ...


1

One way to figure out if one (or both) of the objects is a black hole, neutron star, white dwarf, or other compact object would be to try to measure its mass. For example, a neutron star and a white dwarf are both compact stellar remnants. However, there is one decisive factor that determines which type of stellar remnant a progenitor star will become: the ...


1

If something crashed into it rearranging its content a bit, could its life be extended? Yes! This is precisely what we think causes the creation of blue stragglers. When we look at a cluster of stars, we expect them to all be of roughly the same age. This is usually borne out by observations. Because larger stars evolve faster, the age of a cluster ...



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