# Tag Info

## New answers tagged astrophysics

5

This is a big, unsolved issue in astrophysics. What we know is that it's always associated with accretion: that can be during the formation of a star (a 'protostellar jet'), gas accreting around a supermassive black hole (e.g. a 'radio-loud quasar'), or the formation of a stellar-mass black-hole (e.g. during a 'Gamma Ray Burst'). It seems that cases like ...

-1

This (preprint of a) Science paper from late last year gets into a lot of the physics around the alignment of a black hole jet. Some of the most relevant content: One mechanism known to possibly affect the orientation of a disk or jet is the “Bardeen- Petterson” (BP) effect (15-18), where Lense-Thirring (LT) forces induced by the BH frame- dragging ...

0

Essentially, a chemical and mineralogical comparison is made between the meteorite and samples taken from the Martian surface and atmosphere - particularly from the article The SNC meteorites are from Mars (Treiman et al. 2000, Planetary and Space Science, vol. 48, pp. 1213-1230), that states: Most telling is that the SNC meteorites contain traces of ...

2

First, calling $\ell(\nu)$ a luminosity is a bit misleading since the quantity you've shown has dimensions of power/area (usually called flux, at least in astronomy), while a luminosity has dimensions of power. To answer your actual question, consider first the total power emitted by the star (should involve $R$) and the spatial distribution of that power ...

5

We know that matter in White Dwarfs and Neutron stars become hugely dense, ten or fifteen orders of magnitude more dense than ordinary matter. What we don't know is, if such matter stays stable away from the deep gravity well of the star corpses where they form. We certainly haven't found a single grain of such matter in nature after a couple of centuries ...

1

What does $\kappa$ mean in a context of continuous energy loss In reference to energy $E$ (reaching "[normalized] column depth" $X$) opacity $\kappa_E$ may simply be defined as $\kappa_E := \frac{1}{E} \frac{dE}{dX}$. (If the so defined "opacity" is constant wrt. "[normalized] column depth $X$" this describes "exponential loss" (as a function of $X$) ...

5

A quick, inadequately researched answer, which I post because the question is already at -5, and so probably doomed... A white dwarf is a bit like a blob of white-hot burning liquid metal, spinning in space; the size of a planet but the mass of a star, so if you landed there you would be crushed to a smear of atoms less than a millimeter high, in an ...

2

This is equivalent to the statement that the variations occur slower than the frequency produced by light that oscillates between the opposite points of the celestial object. But that's true because of special relativity simply because no signal can propagate faster than light. The variations of the celestial object occur because of a signal – e.g. some ...

5

Here is the actual announcement of the redshift from Andrew Levan. For those unfamiliar with astronomy practices, circulars are generally where simple things like discoveries, first spectra, redshifts, etc. are announced just as soon as the data is gathered and a preliminary reduction is performed, usually issued the morning after the observation. In this ...

0

Gamma Ray Bursts are a special case of Supernovas. Supernovas mostly happen in areas of heavy star formation, which means that they happen inside a galaxy and are enveloped in or obscured by clouds of hydrogen (both neutral and ionized) and various amounts of other elements inside the host galaxy. These clouds leave absorption lines in the light spectrum of ...

5

Yes, as this link (suggested by Will) shows. They're expected to basically always be stars that used to be in galaxies (they formed there), but have gotten kicked out somehow. You won't really see many stars forming between galaxies because there just isn't enough matter there to collect into stars. Even the ones you do find will be in messy regions ...

1

The crucial concept behind the formation of planar orbital systems like spiral galaxies and our solar system is that the transition from a vague cloud with some orbital motion to a planar system dissipates some of the kinetic energy in the orbital motion (which it can, by turning it into heat) but cannot get rid of the angular momentum. As a cloud of gas ...

0

It is not entirely clear from you question which scale you want to translate it to. An angular diameter corresponds to different spatial distances depending on the distance to the object or surface of projection, so you have to make a choice regarding this before you can get any further. Once you have done this, if your "ball" is small compared to the ...

2

This is not an answer, but merely some information to put you on the right track, too long to be in a comment. I am curious too, to see what other users with more information about the question may answer. Cold plasma models (where the analysis is not complicated by thermal motions) consist essentially in electrons that are nearly free to move among heavier ...

5

It is certainly possible. The human eye will be able to resolve objects in starlight sky and modern sensors are more sensitive than the human eye (permitting single photon detection even). The illuminance will be dominated by a phenomenon known as airglow, an atmospheric illumination that exists even in the absence of light pollution If you have a ...

2

The apparent magnitude of the sun is -26.75, so 2.512^26.75 = 50,000,000,000 times brighter than the brightest star. There are around 50 stars with a brightness within 1 magnitude (ie 50%) of the brightest star so roughly 1/billion-th the light from the sun for starlight.

1

I recently wrote a tutorial for my astronomy club which seems to address your question. It includes numerical examples that specifically covers planetary temperatures and greenhouse effects.

-1

The big bang is completely centerless. The right way to picture where the CMB is coming "from" is to imagine that, long ago, the universe was as hot as the surface of the sun. This means that the universe was filled with a super-hot plasma that looked much like the surface of the sun today. Then, after enough expansion, the gas cooled off, and the ...

3

The CMB doesn't come from one place; it comes from everywhere. It also doesn't go in one direction; it goes in every direction. And it didn't happen all at once, but it happened at roughly the same time everywhere. In particular, it's not the light of the Big Bang, but the light of a time roughly 378,000 years after the Big Bang. The idea is that the ...

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