Does all of time exist and if so where is it?

Your question is difficult to answer exactly, because it touches the question of consciousness, which is problematic in general. But the answer is basically this:

Theory of relativity describes the space-time as four-dimensional space that exists as a whole. You are described by a world-line, which contains all states you go through from birth to death. There is many slices, which describe "you" in different times. What you can see is given by what information reached your sensory inputs (your senses) and how they are processed by your brain. The brain creates a model of reality based on your sensory inputs, which is stored in space-like slice of your world-line in the space-time, which we call present. This is what "you" can see. So the reason basically is in how the brain processes the data it is getting.

Along you world-line, there is many versions of you at different ages and each version feels its own present and the versions more in the future also have memories of the past (because the brain stores the past sensory inputs). There is no single "present time" in the theory of relativity, only the space-time as a whole.

But you should't forget that the theory of relativity is still only a very well working model. Even within the theory of relativity, the question whether space-time exists as a whole, or whether there is "present state", which evolves in time, is rather philosophical than scientific, because there is no observable difference between the two.

How is it that all planets (and moons) in our solar system are in equilibrium orbits?

I think at our current stage of solar system evolution, because of the fact that we have been able to evolve to our current level of sophistication, it could be considered to be very stable and in a very calm period in its evolutionary history. Unstable objects usually will be flung out very early on in the formation of such a system, hence why we do not see them today. However, just look at the Earth-Moon evolutionary history. It is theorised that our current Moon was captured due to a collision between Earth and perhaps a Mars (or similar size) object. This is anything but stable.

The reason why, is of course, related to gravity. Or more correctly, the gravitational potential of the system. All systems want to thermalise (in the same sense that a room of air molecules want to reach a thermal equilbirium). Although our solar system is anything but thermalised, it is constantly working to achieve this. Hence, why, at our present state of the solar system's evolution, we seem like we are in a fairly calm state. At this state, to go into more depth, we can employ Bertrand's theorem which tells us that for a central potential with an $r^{-1}$ dependance on radial distance the orbits will be stable. The stability of orbits in three spatial dimensions is due to the fact that the gravitational potential decreases with distance $r$ as $r^{-1}$.

galaxy - Are galaxies moving away from us faster than before?

The recessional velocity $v$ of an object depends on two things: firstly it depends on how faraway an object is in terms of proper distance $D$ and secondly on the rate of the Universes expansion as a function of cosmological time $t$, which is best expressed as the Hubble parameter $H(t)$. Specifically:

$v = D times H(t)$.

It's worth noting this equation is slightly vacuous as it is merely the definition of recessional velocity, which is not something that can be directly measured.

As recessional velocity depends not just on a function of $t$, but also on $D$, the question as to whether objects are receding from us faster than ever before could be answered in several ways. Before I look at the different ways we could answer your question, I will note a few things. Firstly the definition of the Hubble parameter is:

$H^2(t) = bigg( frac{dot{a}(t)}{a(t)}bigg)^2$

where $a(t)$ is the scale factor which describes how the scale of the Universe changes with $t$ and $dot{a}(t)$ is the first derivative of the scale factor with respect to $t$. Due to cosmological observations the Universe is said to contain dark energy which causes the Universe's expansion to accelerate. What is meant by this is that at the current time $ddot{a}(t) > 0$ where $ddot{a}(t)$ is the second derivative of the scale factor with respect to time.

The first way we could look at your question is we could ask whether galaxies currently at at a distance $D_0$ are receding faster than galaxies that were previously at the same distance were in the past when they were at that distance. From the definition of accelerating expansion and the Hubble parameter we can see that accelerating expansion does not imply that the answer to this question is "yes" and in fact if we assume dark energy takes the form of a cosmological constant, ignoring cosmic inflation and we delve into the dynamics of the Universe with find that galaxies currently at $D_0$ must be receding from us slower than the galaxies that were previously at $D_0$ were receding when they were at $D_0$. So in this particular sense the Universe's expansion is slowing down, even though we usually describe it as accelerated.

The second way we could answer your question is to ask whether the recessional velocity of any given galaxy is larger now than it has ever been in the past. The answer to this question is more difficult as accelerated expansion does imply that the recessional velocity of a given galaxy increase with time, but the Universe's rate of expansion in previous epochs was decelerating. However, again taking dark energy as taking the form of a cosmological constant, we see that the answer is that galaxies achieve their highest recessional velocities twice: firstly at the big bang and secondly in the infinite future. So the answer to this question is that galaxies are not currently receding from us faster than they have been at all previous times.

Recession velocity is different from peculiar velocity (i.e. the local velocity wrt to the CMB). We could add the two to find the 'real velocity', but as I've noted recession velocity doesn't have a direct physical meaning so what this 'real velocity' actually means is not straightforward.

Expansion is homogeneous, whereas the vacuum around a black hole is not homogeneous, so in this sense the 'sucking' of a black hole is not the opposite of expansion.

space - Is the universe like the earth?

A Universe with (hyper)spherical spatial geometry is realistic, though we don't see any evidence for it but it can't be ruled out either. As a point of interest, hyperspherical geometry doesn't necessarily mean hyperspherical topology, though it does mean the Universe must be compact i.e. of finite volume.

Now to address more thoroughly though whether it is possible to circumnavigate a spherical (in both geometric and topological senses) Universe:

Nothing can travel faster than light, so in order to find out if it is possible to circumnavigate the Universe we need to know if light travelling radially outward from some point in space will arrive at the same point in space at some later time. If $R(t_1)$ is the radius of curvature of the Universe at time $t_1$, then to circumnavigate the Universe by that time, the light must have traveled at least a proper distance of $2pi R(t_1)$ from its starting point. Or in other words the radius of the observable Universe must be at least $2pi R(t_1)$ by time $t_1$ in order for anything to circumnavigate the Universe.

The radius of the observable Universe is given by:

$r_{obs}(t_1) = R(t_1) {LARGE{int}}^{t_1}_{ t_ {int}} frac{cdt}{R(t)}$

Where $t_{int}$ is when the Universe begin (e.g. the big bang)

Therefore the condition for it to be possible to circumnavigate a spherical Universe in a rocket ship is:

${LARGE{int}}^{t_{fin}}_{ t_ {int}} frac{cdt}{R(t)} > 2pi$

Where $t_{fin}$ is the time when the Universe ends (note in a Universe without beginning $t_{int} = -infty$ and in a Universe without end $t_{fin} = infty$).

For simple models with spherical spatial geometry the value of this integral is easy to calculate:

$begin{array} {|l|l|}
hline mathbf{MODEL}&mathbf{VALUE}\
hline
mbox{Matter-dominated closed R-W}&2pi \
hline
mbox{Radiation-dominated closed R-W}&pi \
hline
mbox{De Sitter closed-slicing}&pi\
hline
mbox{Einstein static}&infty\
hline
mbox{Eddington-Lemaitre}&infty\
hline
end{array}$

This means that in the case of a Robertson-Walker closed Universe light can just circumnavigate the Universe once from the big bang to the big crunch as long as the pressure is zero. In the de Sitter closed slicing it can only make it half-way around the circumference, even though there is no big bang or big crunch. In the Einstein static Universe you can go round as many times as you like as you have an infinite amount of time to travel the circumference of fixed length. In the Eddington-Lemaitre model the expansion in early times is so slow you can circumnavigate the Universe as many times as you like.

history - Naming of the planets of the solar system

Despite of the explanation of your question, it is a valid question to ask why planets all have Roman names. First of all, the Romans could, like the Greeks and Sumerians, could only see Mercury, Venus, Mars, Jupiter and Saturn. These planets can be seen with the naked eye. However, the fact that the Romans could see these planets, didn't give all the planets latin names.

If the Names of the planets were given by the ones that discovered them first, the planets would have Sumerian names. The answer to the question why the planets have latin names is because they don't. The first western scientist took over the Roman names, because latin was they scientific language of the middle ages and the renaissance. After the discovery of Uranus and Neptune these planets were not given these names by their discoverers. Only after longer controversy western astronomers have standardized the names of planets and moons according to Greek and Roman mytholohy, but this was only around the second half of the 19th century.

Since the beginning of the 20th century the IAU is setting the standards for naming celestial bodies including planets. However, the IAU doesn't set the names, it only sets the standards. Newly discovered objects are now named according to these rules by their discoverers. Older planets are still living with their old names and for western astronomers those are still the names from Greek and Roman mythological figures. However, the IAU allows you to consistently name the planets by their Arabic or Chinese names. So, the question is valid, the text around your question is unfortunately not true, since the planets don't necessarily have Roman names. If you are An Asian person and correctly think the planets should have their Chinese names, because they were earlier in discovering these objects than the Romans (although not earlier than the Sumerians), you are allowed by the IAU (sic) to call them by their Chinese names.

How many stars are in the Sculptor Dwarf Galaxy?

Estimates of star numbers are difficult to obtain. Red dwarfs are too dim to be seen as individual points so star counts cannot be obtained. The best guesses come from obtaining the mass of the galaxy and then guessing how much of that mass is made of stars. It is usually a low proportion, between 1 and 3%. You then guess how big the stars are on average to obtain a rough estimated of the star count.

Sources

Dwarf galaxies tend to have a high mass to light ratio meaning that more of their mass is in the form of dust, gas and "dark matter". Sculptor has particularly high ratio, of about 160$Upsilon_odot$, and a mass of about about 200 million times the sun.

If 1% of that mass is in the form of stars, but the stars are on average half the mass of the sun then Sculptor would have about 4 million stars. The error bars on that number are very large: The mass could be as much as 320 million suns, and the other values are guessed by me (about 3% of the milky way is in stars, but the milky way has a much lower mass to light ratio)

Perhaps the final reason that this number is not easily available is that it is of relatively little use. While the size of a galaxy can be measured spatially or by mass, and the nature of the stars is of interest, the number of them is of less use.

star formation - Simulation packages or theory to work with gravitational collapse of massive molecular clouds?

This sounds very ambitious! I think your way in to this topic might be to have a look at the works of two authors - Matthew Bate and Mark Krumholz.

The reason I suggest these two names is that they are representative of the two basic approaches to simulating the collapse of molecular clouds (which has little to do with n-body simulations). These approaches are known as Smoothed-Particle Hydrodynamics (SPH) and Adaptive Mesh Refinement (AMR).

Crudely put, SPH treats the fluid as discrete particles whose properties are smoothed over the size of a kernel - the resolution is controlled by the number of particles in the simulation and the smoothing length. AMR is a more "traditional" grid-based approach where the size of the grid is varied adaptively with time and space to get the requisite resolution.

A quick google reveals a number of public codes -e.g. for SPH there is SPHYSICS or GRLAB; for AMR there is ENZO or PARAMESH.

One of the main activities in model simulations these days is trying to incorporate "feedback" into star formation. i.e. the winds and radiation from newly born high-mass stars and the outflows from protostars. Such things do not form part of standard codes.

space probe - How long New Horizons will remain operational?

The answer is in the other section:

New Horizons Mission Info

What I can say off the top of my head is that the mission has been extended and they have identified another object that the spacecraft can reach. However, after the next rendezvous it will be out of fuel and will not be able to maneuver.
BUT -- the probe is powered by a Plutonium-238 radioisotope thermal generator (RTG), and will likely to continue functioning for the foreseeable future. The relevant question is: how long will the government fund the NASA operations team that is 'talking' to the probe. That is anyone's guess.

New Horizons Spacecraft Components

PS - I'll update this answer later once I talk with some colleagues. I started, and worked for the company (KinetX, Inc) that did the navigation for New Horizons. I no nothing of the science, but my friends did the navigation and know the near-term details for the mission.

cosmology - Physical laws in other universes

First of all it has to be stated that it is difficult to have a scientific discussion about multiple universes. The problem with multiple universes is that it can be logically deducted from assumptions and hypotheses, but not tested nor empirically verified. This makes discussions around this topic, like string theory, highly "religious".

There are different multiverse theories coming from cosmology, physics and philosophy. One of the theories comes from the cosmological theory of cosmic inflation. Cosmic inflation states that there are always fluctuations on the microscopic level and this results in energy waves that can form into matter and anti-matter pairs. The cosmic inflation now states that at the beginning of our universe there was a cosmological constant or a big vacuum that is by nature unstable and caused the microscopic fluctuations to happen on a cosmic size and thus resulted in a rapid expansion of the early universe. This cosmic inflation is a variation of the (hot) big bang theory, that explains a number of observations in the universe that are not explained by the (hot) big bang theory. What it doesn't explain is that if I have an energy fluctuation at microscopic level, it can happen that this energy wave splits into two matter pairs or an anti-matter/matter pair. Later these pairs annihilate each other and what has happened at microscopic level evens out on macroscopic level. However, when particles appear at microscopic level, what needs to happen to let these particles exist for a longer time to have stars evolve from this matter.

Now back to the multiple universes. The going theory now is that if such a thing can happen to our universe, such a thing can happen in the endless vastness that contains our universe and multiple universes can start and exists next to each other. These multiple universes might also explain that when I have a cosmic fluctuation, I have two universes that come into existence. One with the matter and one with the nati-matter. Bear in mind!!!! These are all philosophical hypotheses and none of it can be verified, falsified or empirically tested.

If I now have made it logically possible to have multiple universes coming from different cosmic fluctuations, I can now have different universes. For instance, I can have for each matter universe a corresponding anti-matter universe to get the energy balance evened out. Now if I have several universes with each different compositions, I can also have universes where, at least, the laws of nature apply differently. In a universe without dark matter, laws of physics apply differently. Whether the "laws of nature" are totally different in other universes, is difficult to scientifically proof. Especially with theories that are build on our laws of nature.

When you think we're already on thin ice here, philosophers can make it even more unreal. If I have cosmic fluctuations that can happen under different circumstances, which result in universes with different compositions that then have a different application of the laws of nature, I can equally well argue that there will be universes where certain laws of nature don't exists, while there are some particles that don't exist in that universe.

So, to answer your question briefly, there are theories that say there are other universes that have different laws of nature. However, multiverse theories are highly speculative and are difficult to proof. So, whether these theories are right, we'll probably will never know.

elemental abundances - Why are certain elements so common?

This is a very broad question: its answer involves the full details of stellar evolution, Galactic chemical evolution and nuclear physics.

I'll limit myself to the following observations:

1. The elements you mention (actually are all "islands of nuclear stability". Whilst their binding energy per nucleon is not as high as that of iron, it is a little higher than elements immediately around them in the periodic table.




2. Nuclear fusion reactions are exothermic (up to iron), but they require energy to initiate them (in a similar way that you need to get coal hot before it will burn). This ignition becomes more difficult the higher the atomic number (the number of protons) in a nucleus. This means that it is not a given that nuclear reactions will simply proceed to the element with the highest binding energy. If there is a way to prevent the material in a star reaching this ignition temperature, then the reactions will not proceed through to iron.




3. This means that even in a very massive star, it is only the core where burning runs to completion in the iron peak elements. The majority of the star is still hydrogen and helium, with the layers outside the core containing the remnants of burning of lighter elements. It is these products that get blown into space in a supernova and mostly consists of products of helium burning (C/O) and alpha capture onto these elements (Ne, Mg, Si, S, Ar, Ca), with each being slightly harder to produce than the last and accounting basically for their relative abundances. Most iron would end up trapped in the neutron star or black hole remnant.




4. Iron is mostly produced following thermonuclear detonation of C/O white dwarfs - a completely different production path. Hence the abundance of Fe is decoupled from things like Oxygen, and more dependent on the rate of type Ia supernovae, governed by binary interactions and statistics than the details of nuclear physics.




5. Carbon and Nitrogen are mainly produced in lower mass stars that never become supernovae and where conditions never reach ignition temperatures to produce heavier elements by fusion. There are many more of these than stars which end as supernovae.

So, the relative abundances of the elements is a very complicated issue that has no simple answer, but where the broad details are well understood in terms of the processes I mention above.

cosmology - Were magnetic monopoles created before, during or after inflation?

Before. The point is that there were too many predicted, and no concept of inflation yet. Here is a reference that doesn't just gloss over it.

Here is the original paper by Guth, and physics.SE has a nice drawing of the same timeline shown on that page. (Original here)

You ought to try that physics.SE thread and continue there for more details.

life - Notable differences if all stars would disappear except the Sun

There are two main things we should look at here, because there are two main ways these distant stars can affect us: light and gravity.

Light

If all the stars in the universe disappeared (besides the Sun), the most of the luminous objects in the universe would simply vanish. There would still be objects emitting radiation - stellar remnants, accretion disks, etc. - but the notable sources of light would be gone.

Would this be an issue? I can't give you any numbers, but I would assume that there wouldn't be much of a difference. Night/day cycles would continue as normal, because the rotation of the Earth also would not be affected. The behavior of stoma in plants should remain the same, as should all the other natural rituals of life.

Gravity

This is where I'm slightly more concerned. Stars have mass, and so they influence other objects with gravity. There are varying estimates of how much of the Milky Way is made up of stars. For example, McMillan (2011) estimated the stellar mass of the Milky Way to be about 6.43$times$10¹⁰ solar masses, while the virial (total) mass was estimated to be about 1.26$times$10¹² solar masses.

The extra matter consists of gas, dust, planets, stellar remnants, and, of course, dark matter (a lot of it). The mass of the Milky Way would be reduced by about 5% - not a terrible amount, but certainly non-negligible. I don't know how this would impact the motion of the Solar System; detailed simulations based on density models would be needed.

However, any effects from stars wouldn't reach us any time soon. Light and gravity both travel at the speed of light, so we'd have at least four years before we started seeing the effects (4 light-years is the distance to the nearest star, Proxima Centauri). We wouldn't feel the effects from the rest of the galaxy for many more years.

What is the cost and benefit of building two identical telescopes?

I suppose that (especially space) telescope costs is dominated by design and development, not by material and manufacturing. So once a telescope has been developed and designed, how much extra would it cost to build a second copy of it? It seems as if spy satellites are built in batches of similar designs.

Would the science value of a second similar telescope be modest, compared to a unique instrument, or improvements on the single telescope, for the same cost?

I suppose that using two telescopes as an interferometer would be quite a different instrument design to begin with than just two of the same.

cosmology - Can the Universe be spatially closed and expand forever?

Yes, if the Universe is matter-dominated and spatially closed, then a cosmological constant:

$Lambda > frac{4pi G rho}{c^2}$

Where $rho$ is the critical energy density (of matter) of the Universe, will cause it to expand forever.

NB Where $Lambda$ is equal to this value you get the (unstable) Einstein static Universe.

orbit - Average amount of annual daylight at any place on earth

Wikipedia strikes again:

The naive expectation is that, for every place on Earth, the Sun will
appear to be above the horizon for exactly half the time. Thus, for a
standard year consisting of 8760 hours, apparent maximal daytime
duration would be 4380 hours. However, there are physical and
astronomical effects which change that picture. Namely, atmospheric
refraction allows the Sun to be still visible even when it physically
sets below the horizon line. For that reason, average daytime
(disregarding cloud effects) is longest in polar areas, where the
apparent Sun spends the most time around the horizon. Places on the
Arctic Circle have the longest total annual daytime of 4647 hours,
while the North Pole receives 4575. Because of elliptic nature of the
Earth's orbit, the Southern Hemisphere is not symmetrical: Antarctic
Circle at 4530 hours receives 5 days less of sunshine than its
antipodes. The Equator has the total daytime of 4422 hours per
year.

Further details here on astronomical causes of average daytime variation, and here on Insolation, the solar radiation received at the top of the atmosphere and its effects on the energy received at ground level.

star - Epsilon Eridani and Sadira

All star names are unofficial. A few stars have ancient names (such as Sirius) all other stars are referred to by their position in a catalogue or star atlas.

As well as I can tell, Al Sadira means "the ostrich", or perhaps in context "The (riverbank) ostrich" indicating a type of tree that grows by rivers (baby name sites offer "lotus tree").

There may be a list of Arabic star names that lists this star as Al Sadira(h) but the name is not in common use and won't be recognised by most people.

The IAU name, Ran, from that of a Norse river goddess, is a recent innovation, and doesn't seem to be much used. The Bayer Designation "Epsilon Eridani" is by far the most well known.

humans - How would we thrive on a planet whose rotational period is different than Earth's?

Here, atmospheric pressure/composition, temperature, and gravity won't be considered; let's assume that all of those are the same as on Earth.

Would we "rest/stay awake" however long or short it takes to rotate? Would we schedule business depending on that? Will our bodies adapt to that or will we break down because of too much or too little work or rest?

Would we stipulate a 24-hour period even if it's very out-of-sync with the rotation of that planet? This becomes very tricky if you've got multiple "sunrises" and/or "sunsets" within that 24-hour period, and those could happen on dramatically different points from one 24-our period to the next. It would be easier, though, if the rotation of that planet is very slow.

Telescope collimation issue - Astronomy

First off - good job for paying attention to collimation. For a newtonian telescope, it is as important as changing the oil on your car.

It would help to know a little bit more about the telescope. What make and model? What is the focal length?

---

EDIT:

Saw your comment below. It's an f/4 parabolic mirror, you're always going to have coma at the outer edge. But the center should be aberration-free if the scope is collimated.

Beware - it's an inexpensive scope, so depending on your luck some residual aberrations may remain even after perfect collimation. But that doesn't mean you should stop trying to collimate it. On the contrary, the better the collimation the better the performance, always.

---

I observe Venus and Jupiter with several eyepieces but I got some "coma like" effect all the time with this telescope.

If the image in the center is fairly good, but you get "coma like" effects at the edge, then that is indeed coma (perhaps mixed with other aberrations). It is normal at focal ratios of f/5 ... f/4 or faster. If the focal ratio is around f/6 ... f/8 or slower, coma is not so easily visible, or not visible at all.

But when I test this setup with laser collimator it show vast miss-alignment in both primary and secondary mirrors.

It is a very common issue with cheap laser "collimators" that the collimator itself is miscollimated. The laser only helps if it is very precisely centered, otherwise it is misleading. Unfortunately, many, many commercial lasers are woefully off-axis.

Plug the laser into the focuser. Tighten the screw only a little bit, so that the laser is sitting there semi-snugly, but you can still turn it around its own axis (rotate it in place in the focuser). Fire up the laser. Now gently turn the laser around, while watching the laser spot on the primary. What does the spot do?

If the laser is centered, the spot should never move as you rotate the laser in place. If the spot moves even a little bit (try to avoid rocking the laser tube sideways, as that would falsify the test), if the spot describes a circle on the primary as you rotate the laser in place, throw that laser in the garbage can.

(Ok, some lasers can be adjusted, provided they have the 2 or 3 adjustment screws on the collar, on the lateral part of the laser tube. Sometimes the screws are hidden under a plastic or metal ring. If that's the case, try and rescue the laser by carefully adjusting those screws. Otherwise dispose of the laser, or destroy it, since it's misleading.)

---

Other things to try

See if you can get better results with the Cheshire only.

Try and make a very simple collimation cap. It's basically a plastic cap with a tiny hole in the exact center, that's all. The procedure for using it is explained here:

https://www.youtube.com/watch?v=YAVGcGEBmCE

A more detailed procedure is explained here:

http://www.garyseronik.com/?q=node/169

If you're patient, you could collimate by the stars. It's complex and time-consuming, but it's guaranteed to be 100% accurate. It is always a good idea to use a quick star test at the end of whatever other collimation procedure you use - think of it as a reality check. The laser may or may not work properly, but the stars never lie.

http://www.astrophoto.fr/collim.html

Laser collimators can be very good and very quick - provided they are centered very precisely from factory. I use Howie Glatter's collimators, but they are not cheap. If you could borrow a Glatter collimator it would show you what's really going on.

http://collimator.com/

Is your primary center-dotted with good precision? In many cases, mass-produced telescopes come from factory with an off-center dot on the primary, which is as misleading as a bad laser. Even the best laser will not work properly if the primary is not precisely center-dotted. But you can always re-center the dot with good precision. See here:

http://www.garyseronik.com/?q=node/168

(Always use a donut shape to center the primary, instead of a solid dot. The donut allows you to use laser collimators, unlike the solid dot markers.)

More thoughts on collimation below. These articles are written by very experienced amateur astronomers and telescope makers. Highly recommended to read these before you begin.

http://www.garyseronik.com/?q=node/165

http://web.telia.com/~u41105032/myths/myths.htm

Try something simple (like the collimation cap) before you open up the scope and do "major surgery" on it. Then do a star test. Does it look pretty good on the stars? Then you're probably doing something right. The stars are looking pretty bad no matter what? Then perhaps you need to open up the scope, re-center the primary, check if the mirrors are sitting properly in their cells, etc.

---

Final comments

If you use too much magnification, the image will not look very sharp, no matter what. Stay within 100x ... 200x while testing. It is pretty rare that atmospheric conditions and/or the quality of mass-produced optics allow good performance above 250x.

Always check the results in the center of the image. With most mass-produced optics, performance degrades at the edge, and there's not much you can do about it (other than replacing them with better optics).

Before you do anything, take the scope outside and let it "breathe" for 30 ... 60 minutes. After it reaches ambient temperature, its performance might get better. More details here:

http://www.garyseronik.com/?q=node/55

orbit - How to get the longitude of the perihelion to find the Heliocentric Equatorial coordinates of a planet

I'm writing a program to randomly generate star systems and I have been having a difficult time figuring this out. I've found the equations I need to get the heliocentric equatorial coordinates, but I haven't been able to figure out how to determine the longitude of perihelion. Is it just the opposite of the longitude of the ascending node or is it a completely different variable?

It might just me, but the names for this stuff is definitely making it more confusing than it should be.

Here is all my notes:

** = power

P = planet's period

a = semi-major axis

b = semi-minor axis

M = mean anomaly

E = Eccentric anomaly

e = eccentricity of orbit

v = true anomaly

r = radial distance

A = longitude of asending node

w = longitude of perihelion

i = inclination

t = time

(r, v) = polar coordinates

(x, y, z) = Heliocentric Ecliptic coordinates

(X, Y, Z) = Heliocentric Equalorial coordinates

eccentricity

e = sqrt(1 - (b ** 2 / a ** 2))

Period

P = sqrt(a ** 3)

Kepler's Equation

M = E - e * sin(E)

Mean Anomaly
use as starting point for eccentric anomaly

M = (2 * pi * t) / P

True Anomaly

v = 2 * atan(sqrt((1 + e) / (1 - e)) * tan(E / 2))

Radial Distance

r = (a(1 - e ** 2)) / (1 + e * cos(v))

Heliocentric Ecliptic coordinates

x = r(cos(A) * cos(w + v) - sin(A) * sin(w + v) * cos(i)

y = r(sin(A) * cos(w + v) + cos(A) * sin(w + v) * cos(i)

z = r * sin(w + v) * sin(i)

Heliocentric Equalorial coordinates

X = x

Y = y * cos(i) - z * sin(i)

Z = y * sin(i) + z * cos(i)

universe - Locations of farthest matter

It's not possible to see photons from "beyond" the cosmic microwave background (CMB), because (assuming our cosmology is generally correct) the CMB is the result of recombination of electrons with protons in the early universe. Photons from before that era were absorbed in the plasma.

Essentially then, the earliest matter we can see (in photonic terms) is this glowing hot hydrogen, but massively red-shifted so it looks like hydrogen at 3K.

We see the CMB in every direction.

meteorite - Do massive bolide entries coincide with meteor showers?

Meteor showers are associated with dust trails left by comets, There are larger clumps, but most cometary dust is pretty small.

Most large impactors are small asteroids: This was certainly the case in Chelyabinsk, and is the likely the case with Tunguska. Asteroids are not associated with cometary orbits and the impacts are sporadic, not concentrated in showers. Each year there are 10s of significant bolides They don't correlate with meteor showers.

(Tunguska did occur during a regular shower, the Beta Taurids, and some have hypothesised that it may have be an fragment of Comet Encke, but analysis of the impact site suggests that this was a coincidence.)

star - How much mass will the Sun have when it becomes a white dwarf?

Short answer:

The Sun will lose about half of its mass on the way to becoming a white dwarf. Most of this mass loss will occur in the last few million years of its life, during the Asymptotic Giant Branch (AGB) phase. At the same time the orbital radius of the Earth around the Sun will grow by a factor of two (as will the outer planets). Unfortunately for the Earth, the radius of the Sun will also reach to about 2 au, so it will be toasted.

There is the possibility that the decreased binding energy and increased eccentricity of the Earth and the outer planets will lead to dynamical instabilities that could lead to planetary ejection. This is highly dependent on the exact time dependence of the late, heavy mass loss and the alignment or otherwise of the planets at the time.

Long answer:

Stars with mass less than about 8 solar masses will end their lives as white dwarfs on a timescale which increases as their main sequence initial mass decreases. The white dwarfs that are formed are of lower mass than their progenitor main sequence stars, because much of the initial mass of a star is lost through stellar winds (particularly during the thermally pulsating asymptotic giant branch phase) and final ejection of a planetary nebula. Thus, the current distribution of white dwarf masses, that peaks between $0.6$ and $0.7 M_{odot}$ and with a dispersion of $sim 0.2 M_{odot}$, reflects the final states of all main sequence stars with $0.9 <M/M_{odot}<8 M_{odot}$, that have had time to evolve and die during our Galaxy's lifetime.

The most reliable information we have about the relationship between the initial main sequence mass and final white dwarf mass (the initial-final mass relation or IFMR) comes from measuring the properties of white dwarfs in star clusters of known age. Spectroscopy leads to a mass estimate for the white dwarf. The initial mass is estimated by calculating a main sequence plus giant branch lifetime from the difference between the age of the star cluster and the cooling age of the white dwarf. Stellar models then tell us the relationship between main sequence plus giant lifetime and the initial main sequence mass, hence leading to an IFMR.

A recent compilation from Kalirai (2013) is shown below. This shows that a star like the Sun, born with an initial mass of $1M_{odot}$ (or maybe a per cent or two more), ends its life as a white dwarf with $M = 0.53 pm 0.03
M_{odot}$. i.e. The Sun should lose approximately 50% of its initial mass in stellar winds and (possibly) planetary nebula ejection.

A comprehensive treatment of what happens to solar systems when the central star loses mass in a time-dependent way is given in Adams et al. (2013). The simplest cases are initially circular orbits where the mass loss takes place on much longer timescales than the orbital period. As mass loss proceeds, the gravitational potential energy increases (becomes less negative) and thus the total orbital energy increases and the orbit gets wider. Roughly speaking, $aM$ is a constant, where $a$ is the orbital radius: so the Sun would end up in a 2 au orbit.

However, in the presence of a non-zero eccentricity in the initial orbit, or in the case of rapid mass loss, such as that which occurs towards the end of the AGB phase, then things become altogether more unpredictable, with the eccentricity also growing as mass loss proceeds. This has a knock-on effect when considering the dynamical stability of the whole (evolved) solar system and may result in planetary ejection. The faster the mass loss, the more unpredictable things get.

The radius of an AGB star can be calculated using $ L = 4pi R^2 sigma T_{eff}^{4}$. Stars at the tip of the AGB branch have luminosities of $sim 10^{4} L_{odot}$ and $T_{eff} simeq 2500 K$, leading to likely radii of $sim 2$ au. So it is quite likely that unless the Earth is ejected or has its orbit significantly modified by some dynamical instability that, like the inner planets, it will end up engulfed in the outer enevelope of the AGB star and spiral inwards...

planet - Why does the Solar System have no (natural) satellites of satellites?

This is due to the mechanics of capture.

For one object (moon) to be captured by a another (planet), some energy has to be removed from the system. If the incoming moon has an existing satellite then it would be ejected, carrying a lot of kinetic energy.

If a small body were to be captured by the planet/moon combination, it would usually be captured by the larger object. Again some energy has to removed from the incoming object by being transferred to one the objects already present. One way that could occur is for the existing moon to be accelerated into a higher orbit.

In summary, it could happen, but with a very low probability.

For much more information, see this answer to the question How do moons get captured?.