10 votes

Why aren't there eclipses every month when the moon's orbit is aligned with the ecliptic as a result of lunar precession?

There are few things here I think might be worth to state: The tilt of Earth is of no importance here. As the comment says what is of importance how much the Moon orbit is inclined to the ecliptic. ...
  • 1,482
9 votes
Accepted

Why aren't there eclipses every month when the moon's orbit is aligned with the ecliptic as a result of lunar precession?

The precession of the moon's orbital plane does not align it with the ecliptic plane. The angle between those two planes is approximately 5.14° (it varies by ~±0.15°, mostly due to perturbation by the ...
  • 10.5k
8 votes
Accepted

Is Earth's climate significantly different when the one solstice occurs at aphelion rather than the other?

Seasons on the Earth are driven primarily by axial tilt. I'm writing this answer in late August, when the Earth is a bit past aphelion. That event currently occurs in early July, a couple of weeks ...
  • 28.7k
7 votes

Is the equinox Sun always at the same zodiac sign in the ecliptic belt?

As you said, the Sun takes a year to cycle the Zodiac, and it takes a year between two spring or autumn equinoxes. Both statements are true, but "year" in them means two different things. It takes a ...
  • 1,580
6 votes
Accepted

Winter in June in the future for North hemisphere

The book is incorrect. The calendar is designed to keep track of the seasons. What will happen in 13000 years is that the Northern Hemisphere summer solstice will still occur near the end of June, but ...
  • 28.7k
6 votes

Season cycle < Year?

Is it possible for a planet's axis to precess or wobble in such a way that its season cycle is of lesser duration than its year? For this, definitely yes, if you tweak some parameters. On the ...
  • 14.5k
6 votes
Accepted

Does precession flip the seasons?

Our Gregorian calendar is designed so that the seasons remained (almost) fixed. The Earth takes 365.256 days to orbit the sun. If the calendar was designed so that the average number of days in a year ...
  • 94.2k
6 votes
Accepted

When exactly was the last time that Earth's aphelion coincided (within 24 hours) with the northern winter (December) solstice?

Using JPL Horizons, I found that Earth's aphelion last occurred near the northern winter solstice some time around 9540 BC. There might be a clever way to get this info from Horizons, but I just used ...
  • 10.5k
5 votes

What effects does the motion of the Sun have on the perihelion precession of Mercury?

What effects does the motion of the Sun have on the perihelion precession of Mercury? A better way to phrase that question is "What effects do the planets have on the perihelion precession of ...
  • 28.7k
5 votes

Is Earth's climate significantly different when the one solstice occurs at aphelion rather than the other?

I'm not sure how much this will add that hasn't already been said, but maybe a few details. You're asking about one of the 3 Milankovich Cycles, called precession and it does play a role, usually ...
  • 22.9k
5 votes
Accepted

Relationship between precession and dating ancient alignments

The answer is fairly simple. It takes about 22,000 years for the Earth to perform 1 spin or move 360 degrees along it's axial precession. The 22,000 year cycle means that the temple was lined up ...
  • 22.9k
5 votes
Accepted

If an orbit is shifting due to orbital precession, is it still a Keplerian orbit?

No orbits are strictly Keplerian, unless you really monkey about with your coordinate systems. However, a precessing orbit is pretty darned Keplerian. The relationship between the various orbital ...
  • 14.1k
5 votes
Accepted

Is the claim that the star Sirius does not precess like other stars true?

Sirius precesses like the rest of the sky. Precession is caused by changes in the orientation of the Earth. Every star precesses as the Earth wobbles. Sirius also has a fairly high proper motion. But ...
  • 94.2k
5 votes

Calculate the general appearance of the night sky over +/-15,000 years

This is not a full answer but more a sketch how I would try to address the issue (but too long for a comment): If you use (or transform) all data you consider to the same datum, then you can consider ...
  • 12.8k
5 votes
Accepted

Is an extreme precession on a tidally locked planet possible?

Yes. Our own Moon is tidally locked to the Earth, but has an axial precession with a period of about 18.6 years. This precession is due to the 1.5 degree offset angle between the Moon's rotational ...
  • 14.1k
5 votes

Using Einsteinpy to plot the precession of a star orbiting a black hole?

This is an interesting development, thanks for bringing it to our (my) attention. Unfortunately, the documentation is lagging the code. The package is using natural, geometrised units, where $G=c=1$ ...
  • 120k
4 votes

If an orbit is shifting due to orbital precession, is it still a Keplerian orbit?

Strictly speaking, pure Keplerian orbits can only occur with two bodies obeying Newton's law of gravitation. If there are more than two bodies then the orbits will be perturbed, to some degree. Kepler ...
  • 10.5k
4 votes
Accepted

How fast do the poles of Jupiter and Saturn precess?

You’ll find the answers you want in the Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements 2015, published by Archinal et al in 2018. I found a copy at https://...
4 votes
Accepted

Does precession affect this measurement?

No special name. The problem that I see here is that the distance will vary over the year. At the moment of solstice, you can easily find the distance by basic trigonometry: If the center of the ...
  • 94.2k
4 votes

Why does the precession of the earth affect other planets?

Why would precession affect the motion of the other planets? First things first: That's an unreferenced portion of a wikipedia article. That said, a perfectly spherical body acts exactly like a ...
  • 28.7k
4 votes

Calculation of RA and DEC

Simon Littlefair of Sheffield University gives formulae for adjusting for precession $$ Δα = M + N \sinα \tanδ $$ $$ Δδ = N \cosα $$ where M and N are given by $$M = 1°.2812323 T + 0°.0003879 T^2 + ...
  • 94.2k
4 votes

Axial wobble or binary star system

There is absolutely no possibility that our Sun is part of a "binary star system". Even the least luminous star (with a mass of about 8% that of the Sun) would have an apparent brightness and proper ...
  • 120k
4 votes
Accepted

How to calculate the nodal precession range of the Moon with respect to the celestial equator?

You want to know the range of RA where the Moon's orbital plane crosses the celestial equator from south to north, so we need to find the line of intersection of those two planes. The vector ...
  • 10.5k
3 votes

Does the rotation of galaxies precess?

To expand a bit on FJC's answer: galactic disks are not rigid bodies, and so we should not expect them to rigidly precess. Most disk galaxies do show warps at large radii (including our own), in both ...
  • 14.9k
3 votes

Earth's precession and the position of the Sun in the sky

These 20-minutes will cause the calendar to "shift" one day every 72 years so if we don't do anything about it in a few centuries winter and summer will switch places. We don't care as much ...
  • 28.7k
3 votes

Earth's precession and the position of the Sun in the sky

Yes, the Gregorian calendar is based on a good approximation of the mean tropical year, so the dates of the equinoxes are stabilised. Geometrically, the equinoxes occur when the Sun's apparent path on ...
  • 10.5k
3 votes

App Stellarium and hourly wobbling motion of Neptune

This appears to me as just the consequence of having an altazimuthally mounted “camera” (the simulation). Objects are tilted towards the left when they rise, towards the right when they. set. You can ...
3 votes

How to calculate the nodal precession range of the Moon with respect to the celestial equator?

Interaction of the Planes The orbital plane of the Moon maintains a relatively constant inclination to the ecliptic, which currently is about $5^{\large\circ}09'$, and the nodes precess along the ...
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3 votes
Accepted

What is being said here about the strange precession of DI Herculis?

The quoted passage says explicitly only that the stars observed velocity amplitude changes over time (due to precession); that does not imply that precession itself changes, but merely that we can ...
  • 12.8k
3 votes

What are the time periods of precession of equinoxes of other planets?

The numbers are surprisingly difficult to find; the easiest-to-find overview in a somewhat funky paper though: ...
  • 12.8k

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