# Questions tagged [sidereal-period]

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### Birthday question

For X, this month in 2024, he has his 46th birthday on Earth, and, in the same day, it is his 191st birthday on Mercury. How often this happens? Reedit: what is the relation between the orbital ...
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### What causes the variation in the length of the synodic month, BESIDES the eccentricity of the Moon's orbit? And how much do they contribute?

When explaining the reason for the variation in the length of the synodic lunar month, usually the only explanation given is that the Moon's orbit is elliptical, and the portion of its elliptical ...
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1 vote
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### Doesn't Gregorian Calendar being started each year on 00:00 cause a huge error in the future?

While Gregorian calendar is a solar year it always start on 00:00 each year. But for sure the Earth completes each orbit around the Sun on different times each year. So if we put January 1 as the ...
1 vote
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### 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?

The inclination of the lunar equator to the ecliptic is 1.543°. Synodic period or Length of a day on the moon = 708.7344 hours Moon Fact Sheet 100 Lunar Days - Parts I and II
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### Sidereal time of rising and setting of the sun on the arctic circle

$$cos(h)= -tan(\delta)tan(\phi)$$ $$\Theta = h + \alpha$$ if these two equations are the correct equations to solve the following question why doesnt it yield the same answer for the sideral ...
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### Why I get slightly (but not acceptable) difference for my Local Sidereal time?

I am trying to convert my UTC into LST by using formula for my astrophysics simulation. The problem is that I get something like difference of 1~2 min when I use known formula and python library ...
• 127
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### How to convert GMST to GMST° (degrees) for calculating RA [duplicate]

For calculating the Right Ascension of the moon I need the GMST (Greenwich Mean Sidereal Time) in Degrees. I have found the formula GMST = 100.4606184 + 0.9856473662862 * D + H * 15, D = number of ...
1 vote
88 views

### How long before two sidereal months start on the same lunar phase?

I was reading about the difference between the sidereal and synodic month when I started to wonder how many sidereal months need to pass before you get two that start on the same part of the synodic ...
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### Are two definitions of a tropical year inequivalent?

Tropical, or solar year, which is 365.24219 days (a day being 86400 seconds) is defined in two ways (implying that they are equivalent): Amount of time from vernal equinox to vernal equinox. Amount ...
166 views

### The orbital period of Jupiter and Europa billions of years later

We know that the Sun gets so big billions of years later and the Earth will get destroyed. What will the orbital period of Jupiter (Sun-Jupiter system) and its moon Europa (Jupiter-Europa system) be ...
2k views

### Can we estimate the orbital period of the planet Phaeton (destroyed planet between Mars and Jupiter)?

Phaeton was a planet hypothesized to have existed between the orbits of Mars and Jupiter, the destruction of which supposedly led to the formation of the asteroid belt. Can we measure its orbital ...
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### What is precision of planet periods data?

Wikipedia gives $10759.22$ days for sidereal period of Saturn. I have calculated a period from de441_part-1.bsp and obtained $10736.247\bar{2}$ days. Why such a big difference? Which is more accurate? ...
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### defining the period of an year on earth

While it is much simpler to define the duration (time) of ONE complete day (for earth), by simply calling it to be the period between sunrise to next sunrise (which we have currently divided into 24 ...
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1 vote
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### Would a Jovian calendar be based on the Jovian sidereal year or tropical year? [closed]

According to many places online, Jupiter's tiny axial tilt makes it have no seasons, and its huge size eliminates any variance possible due to its orbital eccentricity. All these considered, what ...
• 161
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### How long is a mean Jovian tropical year in Jovian solar days?

Many sources say that Jupiter's year lasts 10,475.8 Jovian days. When I calculated to see if that's correct With the data NASA had published, I found out it's the measurement of a Jovian sidereal year....
• 161
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### How long was a lunar month in ancient times?

As the Moon is getting farther and farther from Earth, it's natural that the time it takes to circle around our planet is going to increase, thus the month will be longer. However, I read that the ...
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1 vote
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### Right ascension and sidereal time difference

I've read quite a few articles about this and watched visualisations but I still struggle to get a mental map of how this works I understand that on March 21/22 RA 0 is on my meridian at local noon. ...
487 views

### Is the difference in time between the sideral and synodyc month - constant?

According what I read, the sideral month isn't constant (here)1, as well as the synodic month that isn't constant (here)2. Now, as far as I understood, because the sideral month isn't constant ...
1 vote