37 votes

Can a magnetic field of an object be stronger than its gravity?

It depends on what object it's acting on. There are many objects, including stars, that have magnetic fields where Lorentz forces on charged particles like electrons and protons are stronger than the ...
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29 votes
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Do the axes of rotation of most stars in the Milky Way align reasonably closely with the axis of galactic rotation?

There is very likely to be a random scatter. Unlike planets orbiting the Sun in the Solar System, most of the stars in the Galaxy did not form at the same time as the Galaxy itself. There is therefore ...
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17 votes
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Can a magnetic field of an object be stronger than its gravity?

Let's look at the proper magnetic force (as opposed to the Lorentz force on a moving, charged object described in @KenG's answer) on a specimen $S$ of magnetized material with mass $M_S$ as a way to ...
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14 votes
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Is any 3 body system known?

Answering in the spirit of the question, I think he's asking if there is ever a chaotic 3 body system that's long term stable, or, to put it another way, a 3 body system without a standard hierarchy ...
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12 votes
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Why do stars born in a cluster finally disperse?

The boundedness or otherwise of clusters remains to be established in most cases. The vast majority of clusters become unbound and disperse at a much younger age than the Pleiades. Or they may be born ...
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12 votes

What does this tweeted Astronomy Plot of the Week mean? What does it represent?

TLDR; Its a diagram showing all the physics and modeling choices that go into different models (the colored boxes in the middle) to compute an SED. Longer answer: First a SED is a spectral energy ...
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  • 1,271
9 votes

Can a magnetic field of an object be stronger than its gravity?

It isn't impossible, but the short answer is "no". A gravitational field will accelerate all matter and energy equally while a magnetic field will only accelerate moving electric charges (other ...
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8 votes

Is any 3 body system known?

The three body problem is a theoretical problem in Newtonian mechanics. It is possible to solve, exactly, the two body problem: Both bodies move in conic sections, typically ellipses, relative to ...
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8 votes
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Are the stars outside of the galactic plane in the galactic halo?

The galactic disk, as Riley Jacob wrote, has a definite thickness. It's actually composed of a thin disk $\sim0.3\text{ kpc}$ thick and a thick disk $\sim1\text{ kpc}$ thick, at least (McMillan (2011) ...
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7 votes

Are the stars outside of the galactic plane in the galactic halo?

I'll turn this around for you. The brightest star that is classed as a "halo" or metal-poor population II star is HD 140283, with a visual magnitude of 7.2 and not even visible to the naked eye. Even ...
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6 votes
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What is convection overturn?

The convective overturn time is the typical timescale for a convective cell to rise in a gas. Imagine a "lava lamp" - it's the time for one of the blobs to rise from its lowest to highest point. I am ...
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6 votes
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Is the three-body system "unique"?

What you're really asking about is less to do with Astronomy and more to do with mathematics. You're basically asking if, given a system of differential equations, will a unique solution exist for all ...
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6 votes

List of Moving stars on the northern hemisphere? [Stellar kinematics]

What you're looking for is stars with "High Proper Motion". A Google search of "High proper motion stars" will provide a number of such lists. A quick look at Wikipedia gives this link: https://en....
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6 votes
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What does this tweeted Astronomy Plot of the Week mean? What does it represent?

SED fitting SED fitting is the practice of inferring physical properties of a stellar population (a galaxy, a cluster...) from measures of the Spectral Energy Distribution. The spectrum of a stellar ...
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5 votes
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how far away can close stars diverge with time?

Only one force counts on galactic scales: gravity. Stars like Alpha Centauri are orbiting in the galaxy, as is the sun. Both stars are moving in a similar direction and at roughly the same speed, ...
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5 votes
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Pulsation Modes of Cepheids

Cepheid pulsations The basic description of the mechanism behind Cepheid pulsations is given here: The accepted explanation for the pulsation of Cepheids is called the Eddington valve,[38] or κ-...
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  • 2,692
5 votes
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Why aren't stars like Eternally Collapsing Objects?

We know that stellar radiation pressure balances the gravitational compressive forced of a star. We do not know that. Degeneracy pressure, thermal pressure, and radiation pressure are what ...
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5 votes
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Why is the Sun's brightness and radius increasing, but not its temperature?

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 ...
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5 votes
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If a white dwarf collides with a giant star, could it create a TZO?

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. ...
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5 votes
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How do star densities work?

The mean density of the star is really only defined by the formula $\bar\rho=M/V=3M/4\pi R^3$. The radius of a star is a generally a very complicated function of a star's other properties. When we ...
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4 votes
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Does the Sun orbit the Milky way in a (kind of) flat or inclined orbit or more of a sine wave?

It is correct that the sun bobs "up and down" (relative to the plane of the galaxy as it orbits the galaxy, and it takes about 64 million years to complete a full cycle, so it does pass through the ...
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4 votes
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Examples of astrophysical objects NOT in virial equilibrium?

Not clear what the initial part of your question means. Objects can be in virial equilibrium without being in thermal equilibrium. A clear exception to the virial theorem would be any system that is ...
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4 votes

List of Moving stars on the northern hemisphere? [Stellar kinematics]

SIMBAD allows you to search for stars given various criteria. I searched for: Dec > -20 (easily visible from most locations in the Northern hemisphere) Vmag < 4 (easy naked eye objects) pm > ...
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4 votes

Is any 3 body system known?

There are many systems with 3 and more bodies, but more or less universally they are highly hierarchical systems that behave approximately like a bunch of two-body systems. For example: The solar ...
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  • 112
4 votes
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Is it possible for stars not to rotate?

No, this is not possible. During the stellar formation, some angular momentum will always be present. And any "braking" effects (magnetic, relativistic, tidal etc.) will become weaker as the rotation ...
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  • 580
3 votes

Is any 3 body system known?

Yes, there are triple star systems, bound by gravity, that seem stable. See a list here: https://en.wikipedia.org/wiki/Category:Triple_star_systems There are also systems with 4 stars or more, ...
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3 votes

Ellipticals supported by random motions

The same way rotation does. If you look at each star, it is following some kind of orbit, so it has a motion. The only difference between a spiral and an elliptical is that the motions in a spiral ...
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  • 5,170
3 votes

If a white dwarf collides with a giant star, could it create a TZO?

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 ...
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  • 2,692
3 votes
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Dynamical modelling of galaxies with counter-rotating components using the Schwarzschild method

Convert the 3D luminosity distribution to mass using a bunch of mass particles. Well, you probably could do that, but I suspect it would be inaccurate and extremely time-consuming. Most Schwarzschild ...
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