24387 Powerful aurora sometimes extends into a redlike colour at higher altitudes, and at your latitude this might often be the aurora you see because the it's quite far away. I can't think of anything that would turn a red spectral color into purple or violet over distance, though, except by addin...

It looks very similar to what I've seen described as a  Proton Arc  by the astronomers on APOD and SpaceWeather.  A proton arc is basically the same thing as aurora, but caused by the protons of the solar wind hitting the atmosphere, rather than electrons. Edit:   Oh, I'm out of date!   The proton a...

Those are very impressive!

That sounds like a very good night, indeed, Stellarator!  :) I also just found a thread on the  cloudy nights  forum about whether the Milky Way can cast visible shadows, and was surprised to see people report that they have seen it cast several  shadows, from different parts of the galaxy that are ...

24272 I guess I have no idea what those words mean. Cosmic expansion is awful.  It messes up a lot of our intuitions about relationships between distance, light travel time, angular size, etc... and as a result there are all these different ways to define distances in cosmology to account for those...

I certainly did not mean to imply that your model or artist's rendition were incorrect!  The source is a starburst galaxy that was fired up as the result of a merger, but we don't know what that unlensed galaxy looks like exactly.  It almost certainly has a warped structure with tidal streams of sta...

24187 A new method of determining this probability came to the conclusion we are alone in our galaxy, and perhaps even in our observable universe (53%–99.6% and 39%–85% respectively). New Model Predicts That We’re Probably the Only Advanced Civilization in the Observable Universe What the authors d...

This is a very nice addon!  :)  And yes, it is a single galaxy whose image appears double, due to strong gravitational lensing by the foreground cluster.  Here is a broader optical image to give some context, where the "Eyelash" is labelled  SMMJ2135. https://i.imgur.com/bOfmU6l.jpg This ...

24216 maybe the fact that it was a Bortle 4 location must have added to the illumination for the effects I describe. Yes, that would explain it. :)   Bortle 4 is still a light polluted sky.  Even though it is dim enough to see the Milky Way clearly, there is still a surprising difference in sky bri...

My interest in astronomy began when I was very young.  I remember seeing the images of the outer planets taken from Voyager and being captivated.  It was amazing to me that there were other worlds out there, so different from our Earth, and each other.  I think I got to know all the solar system pla...

Oops, yes I mixed up with the later study.  So the initial discovery was with telescopes in the roughly 1m range.  With some further searching I found an example of an astrophotographer capturing it.  I wonder though if anyone could spot it visually in a modest scope.  I'd be pretty surprised.

The closest real comparison of a Moon illuminated by Venus that I can find:  The dwarf galaxy Leo II .  It is magnitude 12.6 and about 1/3 the angular size of the Moon, so its surface brightness is about 27mag/arcsec 2 .  It was discovered in 2007 using an 8.2 meter telescope and 90 minute total exp...

24119 So what are we to believe about claims that venuslight creates visible shadows? They are definitely true!  I have seen the effect once under a truly dark sky in South America.  I hadn't expected it, so when I saw shadows cast on the ground I thought "where is this light coming from?"...

Sure thing!  It was interesting to compute.

24111 For the magnitude of the Moon eclipsed by an airless Earth, I need mathematics I am unfamiliar with. We can use some geometry along with the magnitude-flux formula from astronomy: https://i.imgur.com/cOXsp5v.gif Where we'll call m 1  the apparent magnitude of the Moon and F 1  its flux (light...