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Glancing at a partial solar eclipse is about as dangerous as glancing at the Sun on any other day. If you look at the Sun a few minutes after sunrise or a few minutes before sunset, when the Sun's altitude is low, the light is filtered through a lot of air, and most of the ultraviolet is scattered, so it's a lot less dangerous than looking at the Sun in the ...


29

No, it cannot. Far from it. The closest approach between both planets is roughly 16 AU due to the 3:2 orbit resonance. Pluto will even then be a tiny dot among many with a brightness around 14 mag. You can try that with Stellarium yourself, placing the observer on Neptune and looking for Pluto. You just have to find the right time. One such time is approx. ...


14

According to the NASA Pluto fact sheet, the brightest that Pluto gets is an apparent visual magnitude of 13.65 when it is 28.6 au from the Earth and (presumably) about 29.6 au from the Sun. To work out how bright that would be from Neptune we could work out how close Neptune can be to Pluto when Pluto is at perihelion. This is complicated by the fact that ...


13

This webpage gives a lot of background information. Key points: It does seem to be the overall dimness of near-total eclipses that allows the pupil to widen enough to allow damaging levels of UV in. There are cases of eye damage from staring at the full sun, and also cases of staring at the noonday sun without apparent damage (not recommended). Perhaps ...


4

That's great question! ... I'm just thinking that just for comparison, Pluto is roughly 70% the diameter of our Moon and Pluto would be far away from Neptune than the Moon is from Earth. Moon is also sort of "fixed" to Earth, but Pluto is in a different orbit than Neptune. I think that Pluto will not be visible with the naked eye given its size ...


4

Light will travel in a straight line through the 4D Space-time continuum. It does not wiggle around and is only deflected by gravity. Light from distant stars reaches us more or less parallel due to the great distance involved. But depending on how accurately you wish to make the measurement, there is scope for some light from that star to reach us very ...


3

I have at least a partial answer to your question: I'm doubtful that 2C 1406 corresponds to IC 4606, given the listed flux density. IC 4606 is an HII region, rather than a supernova remnant, and knowing the Antares system I feel confident saying it also doesn't correspond to Needham's claimed supernova. I don't know what 2C 1406 actually is, although my bet ...


3

Edit 1: @JohnHoltz correctly pointed out two errors - geosats are on the equator, not ecliptic. My brain was thinking "equator" but my fingers had other plans. I read about geosat flares quite some time ago and thought it was solstices when they could be seen but it's around equinoxes, not solstices. I've changed my mind and think planes are the ...


2

Disclaimer I have no medical knowledge and do NOT recommend following what I describe below. Any children that read this should not copy it. I was stupid and it was pointless. Especially do NOT look at the sun with a telescope. It will burn the back of your eyes and cause blindness. When I was about 11, I was told not to look at the sun but not told why. ...


2

The human eye has a resolution of roughly 2 arc minutes, or about 0.5 milliradians (15 pixels across a full moon). The distance to Betelgeuse is a bit uncertain, but lets say 600 light years, which is near enough. So to show a disk simply because of the size of the source, it would need to be about 0.3 light years across. The source can't grow faster than ...


2

The light rays will certainly be very close to being parallel because the star is so far away and because gravitational distortions are so small in our neighborhood. First, rays from opposite edges of the star will arrive at angles that differ by the diameter of the star divided by the distance to the star (~10^-8 radians). Second, the effect of ...


2

The further the moon is from the sun the easier it is to see. There are two reasons. Firstly, when it is close to the sun it gets lost in the glare from the sun. The sky close to the sun is very bright, and there isn't enough contrast to see the moon against the bright sky. Secondly, as the moon gets further from the sun, more of the illuminated side of ...


1

To look at an eclipse is never more dangerous than to look at the normal sun. Sun has uv radiation that can damage the light receptors of the retina. During the noon the sun is directly above our head; sunlight has to travel a short distance through our atmosphere and hence more UV photons that enter our eyes. During sunrise or sunset, sunrays have to travel ...


1

Being by no means an expert of light pollution, I still find my intermediate results worth sharing. On the one hand, there is the Bortle Scale, and I find the flow chart from darksky.org the most accesible way (and probably it is also a reliable source): This flow chart refers to the original publication by Bortle from 2001 which was mentioned in the ...


1

I think James K is right, it might have been airplanes. It happened to me a few times that I saw one very bright yellowish and even brighter getting dot kind of in front of me, and as it came close enough I recognized it's blinking and an airplane. When airplanes are far enough and about in front of you, there is no blinking and they look like big yellowish ...


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