What's the significance of finding neon on lunar atmospehere? new explanation of moon light?

The moon's "atmosphere" isn't much of an atmosphere, and is sometimes called an exosphere. The particle density in the moon's atmosphere is low enough to be considered a very good vacuum for Earth experiments.

The discovery is mentioned in this article on phys.org, which specifically says

There's not enough neon to make the moon visibly glow because the moon's atmosphere is extremely tenuous, about 100 trillion times less dense than Earth's atmosphere at sea level.

...

The behavior of a dense atmosphere is driven by collisions between its atoms and molecules. However, the moon's atmosphere is technically referred to as an exosphere because it's so thin, its atoms rarely collide.

As far as the question "what's the importance" in your title, it seems mainly to be a confirmation of something that has been predicted for a while, as well as providing more data concerning exospheres: the most common type of "atmosphere" in the solar system.

amateur observing - How do you determine which star, between two, is more luminous?

One way to determine the luminosity of a star is to first determine its distance, d. Then one can use the formula, Luminosity = Flux * 4 * Pi * d$^2$. Flux is related to the apparent brightness that is measured with a telescope (and CCD or photometer). mag = -2.5 * Log(Flux) + c.

If the star is relatively nearby, one can use parallax to get the distance. If the star is in a binary system, one can solve for the distance from the period, orbital velocities and apparent size of the orbit. If you know the velocities throughout one orbit, then one knows how far it has physically traveled. Comparing this with the apparent size gives an approximate distance. However, since one usually does not know the inclination, this causes uncertainty. If it is an eclipsing binary, then you know that it is not very inclined and this works well. On the other hand, if it is eclipsing, one can usually determine the radii of the binary pair and then get distances from Stefan Boltzmann Law.

Another method for estimating luminosity is to locate the star in the HR Diagram (Luminosity vs Color). The color (difference between the magnitudes in two different filters) locates it horizontally, and stellar class locates it vertically in the diagram. One needs a spectrum of the star to determine the class.

And we have one more trick up our sleeves. If the star is a periodic variable such as a Cepheid or an RR Lyra, then there are relations between period of variability and luminosity.

planet - The colour of saturn as it appears to the naked eye

Planets do scintillate, just much less often - it takes much greater turbulence to make them twinkle. I've seen Venus twinkle quite a few times, especially when it was close to horizon.

Light pollution makes no difference when observing the planets in the Solar System. They are far too bright to be affected by it.

Saturn should be an off-white when observed with the naked eye. That being said however, if the planet is close to horizon and atmosphere is turbulent, it can cause some weird color effects. But then the color would appear to change rapidly.

In any case, as someone else said in comments, no planet looks like a "ball" to the naked eye. They are all points of light just like the stars.

Check this guide, it should tell you the best method to locate Saturn these days (use the image at the top of the article):

http://www.skyandtelescope.com/observing/sky-at-a-glance/this-weeks-sky-at-a-glance-september-4-12/

If the object you're looking at is in the right place with regard to Antares and the other things in Scorpio, then it's probably Saturn, no matter what color it seems to be. Color is very subjective and can be modified by the atmosphere in some cases. Position is not subjective.

Don't worry too much about color. For comparison, Jupiter is a more pronounced shade of butter-yellow than Saturn, so that's less controversial, you don't see people argue about the color of Jupiter. But a lot of people see Saturn as plain white; I see it as off-white, the color of old PC cases.

If you can borrow some good binoculars, you should see the ring. Lean the instrument (or your elbows) against something solid (like a table or wall), try and keep the binoculars very steady, and watch the object. Be patient and hold steady. You should see the ring as a tiny streak across the planet, kind of like the letter phi: Φ. Just regular binoculars should be enough to make this observation, and it's pretty awesome when you see it for the first time.

In a bigger instrument the real shape of the ring becomes evident.

Is Polar Lights observation possible at the latitude of 56° N?

Yes. The Aurora form in a ring, roughly centred on the Magnetic pole. The pole does wander slowly, but it has been located in the Canadian Arctic for some time.

As the pole is on the American side of the Arctic ocean, aurora are seen at lower latitudes in America than in Russia, nevertheless, when a powerful solar storm occurs, aurora can be seen at surprisingly low latitudes, even into the subtropics, as Wayfaring stranger notes in her comment.

Aurora in Moscow is a notable, but not exceptional occurrence, as this news report indicates http://www.themoscowtimes.com/article/507096.html

solar system - How can a planet have a 90° inclination?

As Wikipedia notes,

Since the word 'inclination' is used in exoplanet studies for this line-of-sight inclination then the angle between the planet's orbit and the star's rotation must use a different word and is termed the spin-orbit angle or spin-orbit alignment. In most cases the orientation of the star's rotational axis is unknown.

As of now (7/26/2015), no other planets, smaller objects, or debris disks have been found around Kepler-452. This means that the situation is not as unusual as might be thought. If there were other planets in the system with orbital inclinations near 0°, then things would appear exceedingly odd. Why would this one planet be different than the others?

One possible scenario is that the star's rotation axis has been changed. Think about how Uranus's axial tilt is skewed. Nobody knows for sure what happened, though one popular theory is that it was hit at some point in time by another object. Granted, it would take a rather large object to have any effect whatsoever on the axial tilt of Kepler-452, but it is still possible.

The point of this idea is that perhaps it is the star, not the planet, which is unusual.

Several papers have been written by those much more knowledgeable than I, notably Crida & Batygin (2014) and Xue et al. (2014). Both refer to Hot Jupiter models, but the ideas behind them are still possible for other planets.

The former suggest

Contemporary observational surveys suggest that a considerable fraction of solar-type stars are born as binary or multiple systems (Ghez et al. 1993; Kraus et al. 2011). Moreover, most stars form in embedded cluster environments (Lada & Lada 2003) where dynamical evolution can lead to the acquisition of transient companions (Malmberg et al. 2007). Recently, Batygin (2012) showed that the presence of a companion to a young star can force the proto-planetary disk to precess around the binary’s axis, so that the plane in which planets eventually form and the equatorial plane of the central star can differ.

They also suggest that encounters with other planets could be responsible for some cases of this (although an angle of 90° makes this seem rather improbable); a related idea that has been applied to Kuiper Belt Objects is the Kozai mechanism. The companion to this theory is that the star was perturbed by an encounter, possibly with a companion (as I discussed earlier).

Xue et al. discuss similar scenarios, focusing in part on "dynamic" interactions between planets. Direct tidal interactions between the star and the planet are also a possible scenario.

big bang theory - Is any consensus forming on the solution to the "Lithium Problem"?

No. There is no consensus.

The discrepancy between the predicted big bang nucleosynthetic abundance of Lithium 7 and the measured value can be summarised as follows.

If we take what we know about the the baryonic mass density of the universe and the Hubble constant, we get a self-consistent picture between the cosmic microwave background, observations of galaxy recession etc. and the estimated primordial abundances of Helium and Deuterium.

The problem arises because these same cosmological parameters predict a primordial lithium abundance of $3times10^{-10}$, when expressed as a ratio to the hydrogen abundance.

On the other hand, measurements of the Li abundance present in the photospheres of the oldest stars (a.k.a. "halo stars") in our Galaxy suggest that the primordial abundance was about $1.2times10^{-10}$.

The factor of 2-3 difference between these numbers is about 4-5 times the measurement precision. This is the so-called "Lithium problem".

The potential solutions are reviewed by Fields (2012). They fall into the following categories.

1. Astrophysical solutions - that we don't understand our measurements of the Li abundances because of an imperfect understanding of the atmospheres of low metallicity stars; or that we don't understand interior mixing mechanisms that mean at the photosphere, we see material that has been mixed upwards from the interior where the Li has been depleted in nuclear reactions.




2. Nuclear physics - maybe the details of the reaction rates and cross-sections in the big bang model are awry? There are still some sizeable uncertainties here which remain to be nailed down, but are seen as rather unlikely solutions.




3. Additions to the standard big bang model. This includes things like inhomogeneous nucleosynthesis in the early universe - i.e. that it was clumpy even at this early stage. Other possibilities include the possibility that various "constants" were actually different in the early universe or that the equilibrium reactions in big bang nucleosynthesis were upset by the decay of massive dark matter particles.

Thus there are lots of ideas to solve this problem, and other ideas which suggest it is not so much a problem, but that we can't do the measurements properly.

cosmology - Does the universe prefer a velocity?

As I understand it, the distribution of matter is roughly homogeneous across space -- anywhere I stand in the universe, there will about the same amount of matter in every direction around me.

Is the distribution of matter across velocities roughly homogeneous? If I flew away from the center of the Milky Way at .999c, would all directions look roughly the same, or would I notice a wind of galaxies and neutrinos traveling at a preferred velocity?

Tags I cannot add: cosmological principle, homogeneity, isotropy