# Tag Info

29

The short answer is no; there is only one barycenter. Yes, you can count the Sun/Jupiter barycenter or the Sun/Saturn barycenter, or whichever barycenter you want, but the net effect of all Solar System bodies is to be considered when you calculate the actual barycenter of the Solar System. (And yes, that would include counting all the small asteroids and ...

15

The Sun's movement in the Solar System can be thought of as its movement around all the individual pairwise barycenters at once, or as a movement around the Solar System barycenter, which itself is constantly moving. Suppose Mercury was the only planet. The mutual barycenter of Mercury and the Sun is about 10km from the center of the Sun, which is inside the ...

14

Has the Earth's wobble around the Earth-Moon barycenter ever been observed by a spacecraft? Absolutely yes if you can count the wobbling motion of the spacecraft that tracks Earth's wobble about the Earth-Moon barycenter. DSCOVR sits in a heliocentric orbit which is in a 1:1 resonance with Earth, otherwise known as a "Lissajous orbit associated with ...

13

The moon's orbit is elliptical, and it moves faster when it is closest to the Earth. This is the case for all elliptical orbits, and was discovered by Kepler, who gave a neat rule for predicting how fast an orbiting body moves. (https://kids.britannica.com/students/assembly/view/90830) For the moon, this means that when it is largest, it is also moving ...

13

Where are Moon's Apogee and Perigee? Do they rotate too? Yes they do rotate! Apsidal precession is the rotation of the line of apses (line connecting apoapsis and periapsis and passing through the Earth). Lunar precession takes this line about nine years to rotate once around the Earth, referenced to the celestial sphere (the stars). Source

11

The full moon and the new moon occur when the moon is in line with the sun. Since the Earth is orbiting the sun, the position of new moon in the moon's orbit moves. The moon takes about 27.3 days to orbit the Earth (relative to distant stars) but a new moon occurs about every 29.5 days. So the direction of the perigee and apogee (relative to the sun) change ...

6

The motions of the Sun, the planets and their moons and everything else in the solar system are well described by Newton's laws of motion and gravity (with some minor relativistic corrections needed to fully account e.g. for the perihelion precession of Mercury). These laws make absolutely no reference to a "barycenter" in any form, so the whole ...

6

I think that the answer is no. Here is why: The image you gave was photographed when New Horizons was getting closer and closer from a large distance. (It wasn't stationary.) We can't easily get closer and closer to the Earth with some camera (expensive to sent something away and then closer), but we can get away from the Earth and photograph it. The problem ...

5

Does the earth spiral around the sun's path as it is shown in the video (exact time is 19:49) and screenshots? The Earth does spiral around the Sun's path, but not quite as it's shown in the video. It isn't clear if the video accounts for the 60 degree tilt of the Solar System with respect to the galactic plane. The sizes and distances are not to scale. ...

4

The following table gives the mass, radius, temperature, and luminosity of an average star of several selected spectral types: \begin{array} {d|c|c|} \text{Spectral Type} & \text{Mass} (\odot) & \text{Radius} (\odot) & \text{Temperature (K)} & \text{Luminosity} {(\odot)} \\ \hline \text{M8V} & \text{0.082} & \text{0.111} & \...

4

Ganymed's Mars approach in 2176 is only moderately close: 4.4 times Mars's Hill sphere radius or 11 times the average Earth-Moon distance. JPL HORIZONS predicts these heliocentric orbital elements (J2000) before and after the encounter: Date e a i Ω ω 2176-12-06 0.525078 2.65922 au 27.7778° 212.085° 136.031° 2176-12-26 0.525093 2.65922 au 27.7772° 212.085°...

3

The first few diagrams show the lunar nodes coinciding with the first and last quarter phases, which is only the case every 173 days or so. When the nodes are aligned with the new and full phases, eclipses can occur: In this diagram from timeanddate.com, our point of view is north of the ecliptic, the ascending node ☊ is in the 5 o'clock direction, and the ...

3

TL;DR: about 5 times current eccentricity for a deviation by 5 degrees from the mean... but the devil is in the celestial mechanics and climate model details. It would not quite work, because the length of seasons would be uneven. Currently Earth's north and south hemispheres get nearly exactly as much or little sunlight as the other. But on the eccentric ...

2

Tycho was concerned that the Earth must be too "heavy" and "sluggish" to move. So his system solves this problem. It turns out not to be a problem at all. The problem it solves is "we know that the Earth can't move, so how can we describe the motions of the planets". As the Earth can move, this isn't a problem. So the whole ...

2

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 elements can be a little complicated, and precession is traditionally thought of as the rotation of the periapsis of the orbit around the more massive body. If we ...

2

TL;DR: No, not always, but most of the time. Well, most planets are in either an equatorial orbit (~0° in relation to the star's rotation vector / equator). Some are in polar orbit (~90° and almost perpendicular to the star's equator/rotation vector), and even fewer are in retrograde or strange (highly eccentric or inclined) orbits. For example, all the ...

1

TL;DR: Virtually zero. The distances between stars are HUGE and stars are tiny compared to the astronomical scales of distance between neighboring stars. The sun, is about 0.0000001 or one ten-millionth of a light year. The probability of a star (to be generous, say a $10 R_\odot$ star) colliding with the Sun is tiny. Every star has a different velocity ...

1

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 orbits are a reasonable first approximation to the orbits of the planets in the Solar System because the Sun is so massive compared to the planets, and the ...

1

The orbital periods, and thus years, of planets in the habitable zones of stars of different types may vary a lot, depending on how wide or narrow a star's habitable zone is and which types of stars can have habitable planets. Thus it may be possible for some habitable planets to have years tens times as long as others, possibly even hundreds of times as ...

1

The main effect would be the radiation environment. A planet in the habitable zone of an M-dwarf would likely be subject to far more ultra-violet and X-ray observation for longer than a planet orbiting a G-dwarf of similar overall age. The reason for this lies in the physics of stellar dynamos that power the magnetism of cool stars. Fast rotating cool stars ...

1

Is the helical or spiral model shown in the video real or just a theory. It's sort-of real but not necessarily the way it's shown. The Earth orbits the Sun in roughly a circle, and the solar system is moving relative to the center of the galaxy in roughly a straight line (on the time scale of thousands of years and more) but those squiggles shown ...

1

Orbits aren't knife-point balances of speed, distance and direction. For two objects separated by distances much larger than their diameters, almost any combination of the three where the speed is below the local escape velocity results in a stable elliptical orbit whose specific parameters are determined by the combination. Ceres (and all the other objects ...

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