All Questions
13 questions
21
votes
6
answers
5k
views
Why doesn't the IAU definition of "Planet" disqualify Mercury and Venus as planets?
Here's the IAU definition of a planet (source):
A celestial body that (a) is in orbit around the Sun, (b) has
sufficient mass for its self-gravity to overcome rigid body forces so
that it assumes a ...
- 511
3
votes
0
answers
88
views
Measured values of the solar irradiance at other values than 1 AU?
It is straight forward to estimate the total solar irradiance of a planet using the Earth's solar constant, and scaling it according to the (mean) distance of the planets. But for which planets have ...
- 5,657
7
votes
0
answers
262
views
Did simultaneous transits of Mercury and Venus actually last occur in 373,173 BC?
According to the Wikipedia article for Transit of Venus, the last time a transit of Mercury and a transit of Venus occurred at the same time was 22 September of 373,173 BC. This is a Featured Article ...
5
votes
1
answer
461
views
Does the axial tilt of Mercury and Venus vary?
The axial tilt of Mars varies greatly over time, with a tilt varying between 15 and 25° over the last million years, and varying even more over the last 5 million years. The Earth's tilt on the other ...
- 17.7k
4
votes
3
answers
2k
views
What could possibly save an atmosphere other than a magnetic field? Why can't a magnetic field save the atmosphere in certain cases?
Similar question here.
We know as a fact that the magnetic field protects planets from Solar Wind, a damaging, continuous, atmosphere-stripping wind of charged ions. Thus, a magnetic field protected ...
- 1,882
2
votes
1
answer
331
views
Historical Distance of Planets to Earth [duplicate]
I'm curious if there is a readily accessible tool available, or simply a reliable way to find out what the distance of the planets in the solar system were on a given date.
For example, if I am ...
- 123
1
vote
1
answer
2k
views
If Mercury and Venus where to collide would it make a habitable planet? [closed]
I have been wondering for a while now about a scenario of where if you combined Venus & Mercury would it be habitable if located in the goldy locks zone? I have found in my little research that ...
- 77
12
votes
1
answer
4k
views
Is it possible that Mercury was originally the moon of Venus after a giant impact?
Mercury looks like the Moon, and so it makes me think about a question: is it possible that Venus and Mercury were the a same planet originally, and a giant impact with that planet made it split into ...
- 2,249
7
votes
2
answers
3k
views
Can we find rocks from Venus or Mercury on Earth?
As we know, we can find rocks from Mars on Earth, how about Venus and Mercury? Is that not found yet? Or it is impossible to find them because they are closer to the Sun, and debris won't go far away ...
- 2,249
8
votes
2
answers
1k
views
Could Venus or Mercury have a moon that we haven't detected?
Let's consider Mars' two moons for a moment. They're small, not even spherical, and most likely are captured asteroids. They weren't discovered until the late 1800's. Telescopes are much more powerful ...
- 2,000
11
votes
2
answers
2k
views
Are there ever any simultaneous transits of both Mercury and Venus as seen from the Earth?
Transits of Mercury happen fairly frequently due to its short period, but transits of Venus are less frequent. I've looked over the data available to me and found that there have been transits of ...
- 901
1
vote
2
answers
387
views
Delta-v from Mercury surface to Venus surface
What it says on the tin: using the most efficient launch opportunity afforded by orbital mechanics, what delta-v would you have to impart to a payload to send it from the surface of Mercury to crash ...
user10233
6
votes
1
answer
229
views
When do Mercury/Venus reach greatest elevation at sunset/twilight for a given location?
On what day does Mercury reach its greatest elevation (in degrees from
the horizon) at sunset a given location?
The obvious answer is the day of Mercury's greatest elongation from
the Sun, but, ...
user21