Astronomy and Cosmology

I understand that the expansion of the universe has caused CMB radiation to redshift into the microwave range. What I am wondering is how long ago was the background radiation in the visible light range, before it redshifted into the infrared? Also, when it was in the visible range, did it have enough intensity to be visible with the naked eye? Was the universe habitable at this time? What I am getting at, in general, is was there a time in the universe, when life forms similar to humans could have observed background radiation with the naked eye?

Astrophysical jets are cosmologically common, occurring in systems as diverse, as forming proto-stars (in Bok Globules): to post-stellar remnants, in X-ray Binaries: Now, jets are 'anti-symmetric', since they travel in opposite directions, both being out-bound. Thus, reversing the rotation of the disk-and-central-object, would not affect the jets. Such an 'anti-symmetry' is characteristic of dipoloidal magnetic fields, whose 'looping' field lines converge down into the disk, from one pole; and diverge up away from the disk, towards the other pole. That 'odd symmetry' of the magnetic field, implies that ions above the disk would be accelerat…

I just read about the discovery of a young black hole. It sems that in 1979 an amateur astronomy buff noticed a super nova and subsequent observations seem to show that a black hole was created there. I was wondering what observations would be seen from this point on. I understand that the environment of the black hole will dictate the specifics, but is there a model for what to look for in the future from this object?

If Jupiter rotates in one direction why do we see bands of clouds rotating in the opposite direction to which the planet rotates? Wouldn't the direction of rotation of the Jupiter (or any other planet for that matter) dictate the direction that any gases/winds rotated? Thanks

Assumptions: Inside a black hole's event horizon light cones do not intersect the world lines of external objects. Gravity propagates as an event. So a black hole's internal gravity doesn't affect external objects? What did I do wrong?

This is a model of the Herschel Space Telescope that was launched in 2009 and is still operating. I'm working in that project.

Ok, I'm going to ask a stupid question, get the flame throwers ready... I have read recently, some place, that not only could our universe have formed from a black hole in another universe warping space time so much it tore out and the singularity expanded out into another dimension or reality or something and made our universe and that black holes in our universe could be doing the same thing and creating other universes. Not only that but universes that form black holes are likely to create more universes than universes that due to having laws of nature different from ours cannot form or form less numbers of black holes or less massive black holes that do not have t…

According to reference, Does that mean, that some WDs, are composed of He (as the spent cores of low mass stars), not CNO ??

The magnetization, of a uniformly magnetized sphere, is derivable from [math]\vec{B} = \frac{2}{3} \mu_0 \vec{M}[/math] and [math]\vec{m} = \frac{4 \pi}{3} R^3 \vec{M}[/math]. Now, a NS exists, at the nuclear density of nn = 1.4 x 1044 m-3; and, is composed of neutrons, whose magnetic moments are mn = (-)0.97 x 10-26 J T-1. Thus, the quantum maximum volume magnetization density, of a NS, is M = mn nn. And so, from observed surface magnetic fields, we can define a 'magnetization fraction': [math]B_{obs} \equiv f \left( \frac{2}{3} \mu_0 \right) m_n n_n \approx f \times 90 \; GT[/math] Thus, the 'quantum critical' magnetic field, for NS, is ~1015 G. All observe…

In standard cosmology, the Hubble redshift in the light from distant galaxies is interpreted as due to an expansion of space. However, it is also said that within "gravitationally bound systems" up to the size of clusters and superclusters of galaxies, there is no such expansion. This means that the expansion occurs only within the voids between these. Now, I have two questions: First, how this is meant to be understood within the standard Big Bang cosmology. If we assume that only 0.1% of the volume of the Universe is filled with gravitationally bound systems, while the remaining 99.9% are voids, there was no space for voids when the age of the Universe wa…

Core-Contraction powers GB luminosities ? "Gravitational Luminosity", the power provided by core contraction, could account, for observed post-MS luminosities, with modest core-contraction infall velocities: [math]U_g \approx -\frac{3}{5} \frac{G M_c^2}{R_c}[/math] [math]L_g \equiv \frac{dU_g}{dt} \approx \frac{3}{5} \frac{G M_c^2}{R_c^2} \dot{R_c} \approx \left( 10^8 L_{\odot} \right) \left( \frac{M_c}{M_{\odot}} \right)^2 \left( \frac{R_c}{0.1 R_{\odot}} \right)^{-2} \dot{R_c}[/math] Thus, as a sun-like star evolves off the MS, core-contraction infall velocities of ~10 nm / s could account, for observed proto-RGB luminosities. And, even the peak RGB l…

Exoplanets are not Brown Dwarfs 1. Star Formation Stars form within Giant Molecular Clouds (GMCs). These dark clouds block the light from background stars, thereby becoming black patches in the night sky*. Now, Dark clouds spin slowly. Molecules of gas & dust inside the clouds bump around, just as they do in Earth's atmosphere. Deep inside these clouds, regions called Cores form. Cores spin, just like the dark clouds that surround them. A Core is the densest part of a cloud, but still far less dense than air**. And, it is within these Cores, or "Star Factories", that "most stars are born, within groups of hundreds or thousands of stars"***. * Ray…

Recently, I came upon some statement like this: "Stephen Hakwing pulls back the Black Hole theory for the Universe" How much is it true? Please elaborate, anyone! Thank You!

Is there a scientific explanation for the dark ages after the inflatioinary period after the BB ?

I made a small webpage with what we know. My dad bought it on ebay and we've been researching for a while. Please check out the page and give us some info if you can. Thanks!

Dark energy is responsible for the expansion of the universe, working against gravity. Negative energy was created at the same time as positive energy was, making the creation of positive energy possible. Since negative energy is the opposite of positive energy, there must be a force the opposite of gravity pushing negative energy apart. This force is pushing the universe apart, concluding that negative energy and dark energy are the same thing. Please voice your opinion on this issue.

Dividing the Planck Density (5e96), by the current Cosmic Critical Density (1e-26), and taking the cube-root, yields ~e41. Thus, at a red-shift of z ~ 1041, our Observable Universe would have been compacted to Planck Density. Is that when/where current physical theory breaks down?

At a given pressure, inside stars, for a given inward gravity, electrons, being less massive, experience less inward pull, despite their similar thermal energies, and higher velocities. I read in a book, that this means stars shed a few electrons, until their slight positive charge affords electrons a balancing EM attraction. The following equations attempt to mathematically model said effect. First, from the Virial Theorem [math]<U> = -2 <K>[/math], applied separately to the electronic, and ionic, components, of the stellar plasma, w.h.t. [math]-\frac{G M m_e}{R} - \frac{Q e}{4 \pi \epsilon_0 \, R} = -2 \left( \frac{3}{2} k_B T_e \right)[/math] …

The Weizsaecker Formula, for the total nuclear binding-energy [math]E_B[/math], of a nucleus, of mass number [math]A[/math], and proton number [math]Z[/math], is (roughly): Now, viewing a NS, as a "single super-sized nucleus", amounts to taking the limit, as [math]A \rightarrow \infty[/math], with [math]Z \approx 0[/math]. Accordingly, the binding-energy-per-nucleon, [math]\frac{E_B}{A} \rightarrow 16 \, MeV \; - \; 24 MeV \approx -8 \, MeV[/math] where only the "volume" & "Pauli" terms have survived. That's a repulsion, of roughly 1% of the rest-mass-energy of the matter making up the NS. By way of comparison, the gravitational binding-energy, f…

According to this lecture, pp.39-41, when two MS stars merge, they make a single, new, MS star, of the combined mass; and, an anomalous star, in eta+chi Persei, is ~60 Msol, even when the MS turn-off, of those ~14 Myr old star-clusters, is ~30 Msol -- which would make the same a 'Blue Straggler' (BS). Perhaps the merger "mixes up" the stellar materials, thereby (partially) "refreshing" the fusion processes, in the combined composite resultant star? (Otherwise, why would mixing two old, H-depleted, and He-polluted, stars, which were evolving off the MS, with the rest of their stellar siblings, manage to make an effectively "rejuvinated" more massive star?) Edit -- Wi…

So im watching The Universe on Netflix and they were talking about how the universe started from a single atom that was indescribably dense and exploded, creating the universe. They also talk about how the universe is infinitely expanding (Dark Matter and Dark Energy i believe). But is there any possible way the the universe didn't start as one small atom? Instead what if the point where that atom was, was actually a clogged hole from another universe that was a different dimension. Then it finally exploded, expanding the universe infinitely but is still being fed though this hole from another universe. Also couldn't it make sense that the hole couldn't be seen because th…

Do you think dark matter and/or dark energy are expanding like the universe, or is their size more of a definite nature like the atom?

The Vector Potential, generated by an individual charge, is [math]\vec{A_{q}} \approx \frac{q}{r} \times \vec{v}[/math]. And, the Dirac expression, for the Vector Potential [math]\vec{A}[/math], of a magnetic monopole, in spherical coordinates, is: [math]\vec{A_{m}} \approx \frac{1}{r} \times tan \left( \frac{\theta}{2} \right) \hat{\phi}[/math] (Jackson. Classical Electro-Dynamics, p. 290) Thus, qualitatively, a spherical distribution of charged plasma, rotating differentially, with "slowly spinning poles" and a "fast rotating equator", would have an azimuthal plasma velocity profile, comparable to [math]\vec{v} \approx tan \left( \frac{\theta}{2} \right) \hat{…

A question inspired by another thread on the same subject sprang to mind that has puzzled me for about 10 years. Round about late December of 2000 there was an occultation of Venus by the Moon. The atmospheric conditions that evening were crisp and clear with Venus in sharp view which I knew from the news somewhere was due to pass behind the Moon through its exact centre. The Moon was in fine crescent phase (might have been a New Moon.). Venus passed behind the Moon into the lit side and passed out the the unlit side such that the Moon and Venus looked like the Islamic symbol. The size and intensity of Venus was pretty good before it passed behind but as it came…

Planetary Nebula (PNe) consist of an increasingly exposed "pre-WD" star core, surrounded by the increasingly distant, diffuse, and (often) ionized shed outer layers, of said star. After the failure of He fusion, the post-fusion, "pre-WD" star core remnant quickly cools down, from ~100k K, to ~30k K, in ~10 kyr: [math]L = 4 \pi R^2 \times \sigma T^4 = -\frac{dE}{dt}[/math] [math]E \approx N k_B T \approx \frac{M}{m_H} k_B T[/math] [math]\therefore \frac{dT}{dt} \approx -\frac{4 \pi R^2 \, \sigma}{N k_B}T^4[/math] [math]\therefore \frac{1}{T_i^3} - \frac{1}{T_f^3} \approx \frac{4 \pi R^2 \, \sigma}{3 N k_B} \times t[/math] Plugging in characteristic va…