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Stellar systems are born from clouds of turbulent gas. Although "turbulence" means that different parcels of gas move in different directions, the cloud have some overall, net angular momentum. Usually a cloud gives birth to multiple stellar systems, but even the subregion forming a given system has a net, and non-vanishing (i.e. $\ne0$), angular momentum. ...


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Stars do not get hot because of nuclear fusion, they become hot enough to sustain nuclear fusion and this process maintains their temperatures. Nuclear fusion actually stops a star getting hotter. Protostars (before nuclear fusion) get hot because of a well known statistical relationship between the gravitational potential energy of a gas and the internal ...


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The collision of another star with our sun would be a very effective way of ending all life on Earth. Fortunately stars are so far apart that the the chance of it happening in the life of the sun is very close to zero. However in the densely packed cores of globular clusters the rate of collision is much higher, and there may be a collision somewhere in the ...


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The effective temperature $T_\mathrm{eff}$ of a star, which is presumably what's been plotted, is defined through its relationship with the star's radius $R$ and luminosity $L$ by $$L=4\pi R^2\sigma T_\mathrm{eff}^4$$ This comes from the assumption that the star radiates like a black body at the photosphere. While this isn't strictly true, it's quite ...


2

Well the spin of the accretion disc is relative. We consider the top of anything as North. What if the the top was to be the South. It depends on perspective. Something rotating clockwise when seen from north would rotate counter clockwise when seen from south.


2

Thorne and Żytkow's original paper on TŻOs actually opens with a comparison of TŻOs and the type of object you mention, with a white dwarf degenerate core instead of a neutron star degenerate core. They note that the equilibrium states - essentially, stable configurations - of such combinations lie near the Hayashi track (actually acting a bit like AGB ...


2

If you slam a white dwarf into a main-sequence star or red giant such that the white dwarf becomes the core you'd get... a red giant (or supergiant). Perhaps that sounds odd but basically the cores of low-mass red giants are electron degenerate. They roughly consist of deep convective envelopes sitting on top of (helium) white dwarfs separated by a thin ...


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One thing that seems to be clear is that HgMn stars have only an extremely weak net longitudinal magnetic field component, if any. Shorlin et al. (2002) did an early survey of HgMn, Am, and Ap stars, and detected no longitudinal magnetic fields in the former, with a median 1$\sigma$ uncertainty of 39 Gauss. Makaganiuk et al. (2010) also found $B_z$ values of ...


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In terms of mean angular velocity, the distribution of rotation rates among main sequence stars is well known. Allen (1963) compiled data on mass, radius, and equatorial velocity, which was then expanded upon by McNally (1965), who focused on angular velocity and angular momentum. It became clear that angular velocity increases from low rates for spectral ...


1

Short answer: The star's density and nuclear fusion. Long answer: Stars originate from nebulae. As a nebula gains more gas, it increases in mass. This increases its gravity, causing it to compress. As it compresses and becomes denser, it raises in temperature. Compression will continue until the atoms cannot be compressed anymore; the electrons fly off, ...


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Before the nuclear fusion in the core starts, the heat of the star comes from the contraction of the original nebula. When the matter comes closer together, the potential energy of it decreases, just like when you drop a rock. Energy is however constant, so it has to go somewhere. That "somewhere" is the heat in the newborn star.


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The usual recipe used in the population synthesis literature is that triple stars comprise ~10% of all stellar systems and the mutual inclination is uniform in the cosine. Most of these systems have a large enough semi-major axis ratio that the inner binary is dynamically decoupled from the outer binary, so retrograde orbits will be just as likely as ...


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This is a more recent review http://arxiv.org/abs/1209.4688 from someone hoping to understand population III by observing their supernovae Since CR7 was discovered, there's been a bunch of papers on whether it could be pop III - http://arxiv.org/abs/1506.07173 for example. Try searching for "CR7 population III".


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The outer layers of the star will fall onto the white dwarf, forming an accretion disk as the star stuff spirals in. Like this image shows. When the white dwarf steals enough material to get bigger than 1.4 solar masses, the dwarf will become a Type Ia supernova. This is probably why we never (rarely?) see Thorne–Żytkow objects made from a white dwarf ...


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Yes you can. You just need a partly clear sky (to see the stars) and part cloud (to produce the rain). For an example of suitable conditions, look for pictures of a moonbow. (I've only seen one once, personally.)



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