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2

Exoplanet means those planets that arent in our solar system, and solar system planets are in our solar system . The two (blue)triangles must be earth and mars i suppose and purple points are exoplanets and yes most of the exoplanets are made of Hydrogen and helium and revolve around other stars from the graph given .


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Firstly, your idea does make on important prediction, which is that the universe originated at a point in space (the location of a black hole) and we should be sucked towards that point, eventually being sucked in and the cycle happening all over again. There is plenty of observational evidence that your theory can not be correct. Firstly, the universe did ...


2

The division between He flash and no He flash is more like $2M_{\odot}$. The core of a low-mass star doesn't come out of degeneracy until the He flash is underway; until then, the partial degeneracy increases as more He ash is dumped onto the core and both density and temperature continue to increase (because the number of mass units per particle ...


3

The purpose of computational physics is not to perfectly replicate reality. This is an important point that is missed by many, indeed even some people who work in the field. Suppose you had a full and complete description of all the physical laws governing your system, be it a fusion reactor or a star or a galaxy or the whole universe. Now suppose you ...


0

If we put in a computer program the right laws of nature and we scan all the possible initial conditions, then we can get the right answer, with some numerical errors. The problem is simply that in many areas we don't know exactly what is the underlying physics. To name some (big) open problems: dark matter, dark energy, CP violation and Matter-Antimatter ...


3

As the photosphere expands it eventually becomes cool enough to form dust. The dust formation is enhanced by shocks driven by pulsational instabilities. This dust is opaque to visible radiation and even though the radiation field from the star is weak, the surface gravity is so low that the radiation pressure is able to accelerate the material away. Typical ...


4

Both elliptical and spiral galaxies have a stellar mass profile which have a well-defined maximum. In addition, both types of galaxy have symmetries - axial in the case of spirals and either axial or triaxial in the case of ellipticals. Since, in general terms, the luminosity tends to follow the stellar mass, this means that their projected brightness on the ...


8

I think the colloquial term for that type of plot is "spaghetti diagram" because you have a bunch of lines running across it. It's really the mass fraction as a function of interior mass. From our stellar structure equations, we have that $$ \frac{dm}{dr}=4\pi r^2\rho, $$ which is derived from the mass-continuity equation, so you can relate the radius, $r$ ...


4

Annihilation lines are spectral lines caused by the collision of particle-antiparticle pairs. In the case of $e^-e^+$, the emission is at 511 keV. (source (arXiv link)) However, because it is caused by a collision of particles, rather than an absorption-emission of a photon, the peak is Doppler broadened. This means that the peak is spread out over a few ...


0

There are two scenarios that come to mind. 1) the universe as it exists now, with only the propagation speed of photons instantly becoming infinite. 2) The speed being infinite at the start of the Big Bang. For the first scenario, since light that we don't see now would become visible, the sky would become at least as bright as our daylight sky. Since all ...


3

I think the following image, which comes from Tomczak et al. (2014) and the so-called ZFOURGE/CANDELS galaxy survey should do the trick. It shows how the galaxy stellar mass function (i.e. the number of galaxies per unit mass per cubic megaparsec that have a certain stellar mass) evolves as a function of redshift. As you might imagine this is not just a ...


6

White dwarfs with strong magnetic fields ($>$1MG) make up only about 10 per cent of the white dwarf population. A further few per cent have fields in the 10-1000 kG range (e.g.Liebert et al. 2003). So it is not clear that the Sun will end up as a "magnetic white dwarf" at all. The production of magnetic white dwarfs is thought to arise via at least two ...


1

Firstly, it is important to note that the old Big Bang cosmology is no longer the most widely accepted theory. We include inflation into the mix in current theories. That said, there is an ambiguity in the definition of the Big Bang (you can find information on that in my question here). If we take the definition of the Big Bang as coming before inflation, ...


1

This is not a very sensible question unless you limit it to a dimensionless number of discrete things. You certainly cannot talk about anything with units, because you can pick whatever units you like to make something a very large number, though a ratio of two temperatures, densities etc. measured in the same units could be permissible. Eddington's number ...


1

Estimated number rather than maximum number of combinations , from what i found is $$ 5* 10^{96}$$ ,Planck density, the density (in kg/metre3) of the universe at one unit of Planck time after the Big Bang. Reference here. According to Don Page, physicist at the University of Alberta, Canada, the longest finite time that has so far been explicitly ...


0

This is a nonsensical question because we can pick ANY scale we like for our basic units and the numerical values that pop out of calculations will, as a result, be all over the place. Some folks like to argue that there has to be some highest energy/lowest spatial and temporal scale, but that's only correct for our particular era of the universe. Scales ...


2

The number of protons in the universe is estimated to be $10^{80}$ and is called Eddington's Number, $N_{Edd}$, named after the British astronomer Arthur Eddington. This falls short of the family Googol, which is $10^{100}$ which in turn falls way short of a Googolplex, $10^{Googol}$. Apparently a physicist at the University of Alberta, Canada, Don Page, ...


1

As soon as the universe came out of its dark age if light speed was infinite then it would be able to keep up with the expansion of the universe. It would be very much brighter all around, perhaps intolerably to us. The universe would appear very active since event far far away would appear to us instantly. We might be blind as our light sensory organs might ...


2

according to the astrophysical observations which shows for example: much more bending expected in lights directions due to the gravity of the stars and galaxies we know. it means we know there are four example 2 galaxies which can bend the light which come from a third and farther galaxy. and the bending to the light due to these 2 galaxies should be X. but ...


1

It is a matter of the standpoint of the observer. Because time comes to a standstill at the speed of light, to the photon, no time passes, whatever the distance traveled and its speed is therefore infinite.


3

The answer is that 41% of the stars have masses below 0.25$M_{\odot}$. To check this I integrated the Kroupa initial mass function. This is that $N(m)$ the number of stars per unit mass is proportional to $m^{-1.3}$ for $0.08<m/M_{\odot}<0.5$ and proportional to $m^{-2.3}$ for higher masses. If I integrate this I find that the ratio of stars with ...


6

The stellar mass distribution is the distribution of numbers of stars within a range of masses in a galaxy (or cluster or what have you), not the mass of the stars. So if you looked at the $\sim10^{11}$ stars in the galaxy, you would observe that about $4\times10^{10}$ of them will have a mass less than 0.25 $M_\odot$, and so on with the rest of the masses. ...


3

According to this source, 100% is the number of stars, not the total mass. Same from another source. The reason is that they usually calculate these pies straight from the H-R diagram. The H-R diagram plots individual stars and shows how stellar mass varies along the main sequence. Actually the mass distribution tends to reverse. Even if larger stars are ...


3

Yes the energy $u$ stored in a field $B$ in a region with permiability $\mu$ is given by: $$u = \frac{1}{2}\frac{B^2}{\mu}$$ So if you double $B$ then $u$ gets quadrupled and if you increase $B$ by a factor of $10^{10}$ then $u$ increases by $10^{2\times 10} = 10^{20}$. I'm not quite sure about the assumptions that go into the above formula however (I'll ...


0

Changing the value of $c$ would change our physics behind recognition, but if we ignore that pesky detail: let's assume that our fictional universe is of infinite size, contains infinite many stars, and has $c=\infty$. Does that mean that every line of sight would end in a star, and the sky would be brighter than the sun (assuming that in this universe, the ...


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Terrific question. You had it right in your first sentence: “the same amount of energy must have been released during the Earth's history,” but then it gets a little mixed up when you look at various energies, some of which aren’t related to the question at hand (for example, the current internal energy contributes positive mass-energy to the Earth, rather ...


3

The rest of the energy went into space. Without that energy loss the planet would not even have condensed and the gas/dust cloud would have stayed a cloud. Having said that, the details of these condensation processes in planetary clouds seem to be non-trivial and, from what I have read, are not fully understood, as of yet.


5

Changing c to infinite changes some important things. The actual effect depends on how you want to propose magnetic forces work (they're normally fictitious forces induced by relativity). If we assume the coupling constant (this constant doesn't appear in the equation as it's value is normally 1) goes to infinity as c goes to infinity so that magnetostatics ...


15

In vacuum $$ \nabla \times \vec{B} = \frac{1}{c^2} \frac{\partial \vec{E}}{\partial t} = 0$$ so a changing E-field does not beget a changing B-field. Larmors formula for radiation from accelerating charges also has $c$ in the denominator. Therefore no (star)light at all ? [Or at least no electromagnetic waves].


-2

In case of infinite c, electromagnetism reduces to just electrostatics. So, light would not exist. To clarify, the role c plays in physics is that of a scaling parameter, there are only 3 different physically distinct cases: c = 0, c = finite, and c = infinite. In the latter case, the laws of physics are non-local, the there is no good notion of locality, ...


40

In a Newtonian/Galilean world, where $c$ is infinite, you could not escape Olbers' paradox with an infinite universe. Any line of sight would eventually intersect the surface of a star, and so the whole sky would be as bright as the Sun. This is true whenever two hypotheses are satisfied: The universe is spatially infinite (or rather, the distribution of ...


3

For an object close to you, the speed of light is effectively infinite - i.e. the time taken for the light bulb 10m away from you to get to you is so close to zero that it can be considered immediate, and thus the speed of light is assumed to be infinite. With this in mind, this would mean that the sky would be brighter. In reality, the speed of light is a ...


0

Observations are not made with a single photograph frame, they're made over longer periods of time (for example, a friend takes observations of Herbig stars over 2 minute periods in the J-band with Gemini North). The emissions from stars range from UV to IR (depending on your opinion, it could also range from IR to UV ;) ), these emissions are continuous ...


1

The formula $$ L = \epsilon A \sigma T^4,$$ where $L$ is the luminosity in Watts, can be used for a "grey body" i.e. one that has a constant emissivity with frequency. Here you were told to "assume the Sun to be a perfect blackbody". This means that its emissivity is 1 because a blackbody absorbs everthing incident upon it and because it is in thermal ...


0

Astronomy is mostly concerned with observing the night sky, calculating the positions and movements of the heavenly bodies and identifying objects. Astrophysics is concerned with figuring out how stars form, studying the chemical reactions within the stars, calculating what elements the stars contain and so on.


4

The Einstein equation says: $$ {\bf G} = {\bf T} $$ where $\bf G$ is the Einstein tensor that describes the curvature, i.e. the gravity, while $\bf T$ is the stress-energy tensor. So the origin of gravity is the stress-energy tensor. This is typically dominated by mass, but includes less obvious contributions like pressure and momentum. Actually solving ...


2

I can't really say what the significance of the result is that you show without some more details on what exactly is being shown in the picture and where it is from. Here though is a counter-example from the well-cited study of Fich, Blitz & Stark (1989) for our own Galaxy, which appears to show excellent agreement where the two techniques overlap ...


0

The basic model for a solar flare starts with the magnetic field in the corona. You can think of the topology of the magnetic field to consist of loops that poke up out of the photosphere and extend into the corona. However, the photosphere of the Sun is turbulent and constantly in motion due to convection and differential rotation. Whilst a loop may be ...


5

The CMB (cosmic microwave background) is a snapshot of the oldest light in our Universe, imprinted on the sky when the Universe was just 380,000 years old. It shows tiny temperature fluctuations that correspond to regions of slightly different densities, representing the seeds of all future structure: the stars and galaxies of today. The anisotropies ...


1

The CMB is a snapshot of the state of the universe at the moment when the universe cooled enough to allow protons to capture electrons to form atoms, thereby allowing light to travel unimpeded for the first time - prior to this the universe was a remarkably uniform distribution of plasma. But there -were- minute variations, which appear to be a Gaussian ...


1

If we take neutron star material at say a density of $\sim 10^{17}$ kg/m$^{3}$ the neutrons have an internal kinetic energy density of $3 \times 10^{32}$ J/m$^{3}$. So even in a teaspoonful (say 5ml), there is $1.5\times10^{27}$ J of kinetic energy (more than the Sun emits in a second, or a billion or so atom bombs) and this will be released instantaneously. ...


1

If you assume that there are 200 billion stars - that is objects with mass between say $0.075 M_{\odot}$ and $100 M_{\odot}$ you can use this to normalise a mass function - the number of stars per unit mass - and then integrate stellar mass, weighted by this mass function, to estimate the total mass in stars. If you do that then what you find is (1) high ...


0

Does the photon add to the mass of the black hole an amount of mass m = e/c^2, where e is photon energy? Yes. If so, is it the energy the photon had at the beginning, or the energy the blue shifted photon has as it crosses the horizon? The energy the photon had in the beginning. As such, it will reach the horizon with no energy at all. He will ...


0

The answer to this is really very close to Ted Bunn's answer to this question, but I think there may be one additional point .... a disk the most stable configuration Maybe it could be thought of as the 'most stable configuration', but I think it should rather be thought of as the natural state that accreting matter will form for the following ...


2

In another closely related question (According to the initial mass function, should there be more brown dwarfs than red dwarfs? ), I showed that the number of brown dwarfs (with $M<0.075M_{\odot}$) is a factor of five smaller than the number of red dwarf stars (stars with $0.075<M/M_{odot}<0.5$), using the widely adopted Chabrier (2005) lognormal ...


3

There are several commonly used analytic approximations for the initial (birth) mass function (IMF) that cover both stars and brown dwarfs. It is not yet absolutely certain which of these is more correct at the low-mass end, whether there is a lower mass cut-off as one approaches planetary masses, or whether the fraction of brown dwarfs (BDs) to stars varies ...


2

The correct comparison for a neutron star is with a cinder spat out of the fire. The cinder will glow brightly for a short period of time and then fade rapidly. Such is the fate of neutron stars, because although born at $10^{11}$ K in the heart of a supernova, they have an extremely low heat capacity. Contrary to common belief - neutron stars are not ...


15

In an "ordinary" gas of protons and electrons, nothing would happen - we call that ionized hydrogen! However, when you squeeze, lots of interesting things happen. The first is that the electrons become "degenerate". The Pauli exclusion principle forbids more than two electrons (one spin up the other spin down) from occupying the same momentum eigenstate ...


3

This is difficult to answer in an unarguable way because the old bimodal classification of population I and II is more nuanced these days - e.g. thin disk, thick disk, bulge population etc. However, if you define population II as meaning those stars that were born in the first billion years of our Galaxy's evolution, then the following rough calculation ...


0

Note that the way a transformer would fail is not directly due to the induced current. Rather what happens is that these induced currents magnetize the core of the transformer (the currents are, of course not constant DC currents but the frequency is so extremely low that over a period of many minutes they can be considered to be effectively DC currents). ...



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