7 votes

Orbital period of a planet orbiting Delta Pavonis in habitable zone

From the Keplerian-Newtonian two-body approximation (which is more than good enough for most fictional worldbuilding), eccentricity doesn't matter for orbital period. When the mass of the satellite is ...
notovny's user avatar
  • 4,696
5 votes

Calculating the parameters of binary systems?

You can't. There are an infinite number of stable orbits that are possible depending on the angular momentum and total energy of the system - which must be negative for a bound orbit. If you specify ...
ProfRob's user avatar
  • 146k
4 votes

Are the rotational axes of Earth and Mars parallel?

The polar axis of Mars is not parallel to the polar axis of Earth. The north celestial pole of Earth has a declination of 90°, but the north celestial pole of Mars has a declination of almost 53°. ...
PM 2Ring's user avatar
  • 13.1k
3 votes

Which star system has the highest multiplicity (# of stars), whose orbits are known for all stars?

As of writing this, 11 October 2023, I am reasonably certain that the star systems with the highest multiplicity, whose orbital periods of each of the stars are known, are those of the two septuple ...
Jimmy G.'s user avatar
  • 714
1 vote

Can there be multiple periapsides?

In the picture, and in any two-body orbit, the stars are closest together at a single periapse, and there is a single line of apsides. In the picture, the stars are closest together when they are ...
James K's user avatar
  • 116k
1 vote

What is the duration of a year on the Moon (Tropical/Sidereal period) for orbit about the Sun ? How/why does length of lunar days vary ? Soltices?

A day on the moon lasts 29.53 days (a synodic month), slowing down by 0.005 seconds every century. ref. The tilt of 1.54' relative to the Sun has an 18.5996 years periodicity. ref.
bandybabboon's user avatar
  • 4,188
1 vote

What are "non-Keplerian" orbits? What are some familiar examples in our solar system, and can some still be closed?

What exactly are "non-Keplerian" orbits? Let's first start with Keplerian orbits. A Keplerian orbit is the motion of one body relative to another body, and takes the form of an ellipse, ...
DialFrost's user avatar
  • 2,105

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