Science and Astronomy Questions
Posted: 04 Nov 2018 05:06
Stellarator wrote:An'shur wrote:Source of the post If the atmosphere of Venus was completely cloud-free, would we even be able to see anything from the surface, like Sun, planets, and stars?
This is a very interesting question! I assume you mean if the atmosphere was STILL CO2 rich and capping at a pressure of 93 bar, with its characteristic temperature of 740 K (467 °C, 872 °F)? There is an excellent write up about this here, that you might find enlightening. The relevant passage is at the bottom of the chapter's page, but if you'd rather read here, this is the part I'm referencing:
No doubt this will raise even more questions, but hopefully that'll answer your initial one.
Indeed. So the Sun would be observable at all times, but I do not think anything else would (maybe besides Earth, if you knew where to look, but just maybe), since the Sun would be always visible, at least slithering around the horizon and illuminating the sky, making it too bright for stars to be observable. But it is just my assumption. Even though the Sun is dimmer during sunsets or sunrises even on Earth, it is the Sun we are talking about and there may not ever be a true dark night on planets with absurd atmospheric pressure and temperature.
On Earth, the red distorted Sun is still visible for a brief period of time even when the Sun itself is already below the horizon. Could the same effects as on Venus be happening on planet with a breathable atmosphere? My idea is, a planet with an atmosphere with the right amount of oxygen for us to breathe, maybe some nitrogen and another inert gas to dramatically increase the pressure, for example neon or helium. (I am getting this idea from breathing mixtures used for diving). How much helium could I pile up into the atmosphere for it to still be breathable and survivable on the long run?
Stellarator wrote:Source of the post Did you try auto-exposure?
Yes, to no avail.
Most of my original questions have been answered, except:
An'shur wrote:Source of the post I know the Moon is about a million times (or 15 magnitudes) dimmer during a Lunar eclipse. And it would receive no sunlight at all if was to be eclipsed by an alternate version of Earth, completely airless Earth. Nothing to refract or scatter the light, obviously. But would it be truly invisible? There may still be outer reaches of the Sun's corona and stars in all directions to illuminate the Moon, hell, even bright planets (Jupiter, Mars, and especially Venus). What would be the apparent magnitude of the Moon in such a scenario? If it was insufficient for the naked eye, how big of a telescope would I need?
How would it look if a comet entered the Earth's umbra? Would Earth's magnetosphere influence the shape of the tails?
For the magnitude of the Moon eclipsed by an airless Earth, I need mathematics I am unfamiliar with. Comet entering the Earth's umbra is more of a fun question.