# Tag Info

16

No, although there are times when it can't be seen, it isn't true that it is visible for 183 days of the year. The general question could be "If I take an arbitrary location on the sky (say a randomly chosen star) will it be visible for half the year? The answer is "it depends on the star!" Polaris and many other stars are circumpolar for ...

13

The time of the orbit is not well known but the inclination can't change as much (small changes in velocity due to outgassing can significantly change the orbital period, but can't change the inclination much. So, while we have a good idea of it's orbital track close to perihelion, we just don't know when it will be there. We don't know where the Earth will ...

10

The first image is from a July article by TV meteorologist Brent Watts. Approximating that view in Stellarium: The yellow arc is the ecliptic, the plane of the Earth's orbit around the Sun. It looks curved due to the map projection. If the view is centered on it, the ecliptic looks straight: Unlike the Sun, which appears on the ecliptic at all times, the ...

9

It is important to appreciate the scale of the comet's orbit compared to the Earth's orbit. The Earth goes round the Sun in a nearly circular path. The average distance is one Astronomical Unit (AU). C/2020 F3 (Neowise) has an incredibly skinny elliptical orbit. It's closest approach to the Sun (perihelion) is at 0.3 AU, which is inside the orbit of Mercury. ...

9

Short answer Short answer is no, it can't prove or disprove the existence of Planet 9. The reason is because, even if there is a significant difference between the barycenter of the solar system with and without Planet 9 we wouldn't be able to tell without hundreds if not thousands of years of precise data. If we don't have Planet 9 as a reference and are ...

6

To simplify, I used Starry Night to generate a visualization. The yellow arc is a piece of the ecliptic. You can see (in faint gray) the center of the yellow arc is labeled 'Dec'. The Sun will be in this part of the sky in December. You can also see planets of the inner solar system and in the background, part of Sagittarius (and the Teapot asterism) is ...

6

Simply because we can see the sun. The comet will be swinging around the sun, getting closer to it than the Earth does by a large factor. This path cannot always be in-line with the sun or other body orbiting the Earth or the Sun, so there isn't a way for our view to be blocked. It is plausible that its approach could be mostly co-linear with the sun, or ...

5

Not really. The mass of Mercury and Venus together are just 0.0027 of Jupiter's mass. So the effect is really small. Now, in principle, there are resonances where the regular tug from planets affect the long-term evolution of the orbits of other planets. The exact details get very messy, but in some cases the presence of a planet stabilizes certain orbits - ...

4

Comet naming conventions limit "periodic comets" to those comets whose orbital period is less than 200 years. Comets in elliptical orbits with a period of greater than 200 years are classified as non-periodic. Comets in parabolic or hyperbolic trajectories are also classified as non-periodic (and they will never again approach the primary).

4

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 Mercury?" When calculating the perihelion precession of a planet, one is implicitly working in a heliocentric frame, one in which the Sun is viewed as fixed. ...

4

Planetary magnitudes vary not only according to the Sun’s luminosity, their own average albedo, and their distance from the Earth, but also from: Variations in their albedo across their surface. Their phase angle, for planets that we sometimes see as a crescent. Their inclination, for planets like Saturn and Uranus that have a different albedo at their ...

3

Supplementary answer: "Near-parabolic" means almost or nearly parabolic, but not quite. Another term would be "highly elliptical". Technically speaking, no realistic orbit can really be exactly parabolic since that means eccentricity is exactly 1.00000000000.... and most of Physics (solar photon pressure, relativity, gravitational ...

2

Mars (the planet with an axial tilt closest to that of the Earth) has an axial tilt that varies greatly over time. For instance, 4 million years ago, the mean obliquity was $∼35 ± 10°$. From the same article: Earth on the other hand has had its rotational features stabilized due to the effect of our large Moon. So it is only by chance if the axial tilt of ...

2

One of the possibilities for the inner Solar System becoming unstable over the next few billion years is a secular resonance between Mercury and Jupiter that increases the eccentricity of Mercury's orbit, which can result in some interesting consequences. From Batygin & Laughlin (2008): The experiments yielded one evolution in which Mercury falls onto ...

2

Not yet, as far as I can tell. The comet looks very different from Mars and while I haven't done the math, I don't think it has an apparent size from the rovers' perspectives to make it look like anything more than a dot. Since Neowise is moving away from the Sun, the length and brightness of its tail is diminishing rapidly.

1

A plane looks like a curve when viewed on large angular scales on the sky (how could it be otherwise, think about a plane that cuts the north and south poles). That plus the planets aren't in exactly the same plane.

1

I feel like this is getting into worldbuilding a little, but a Dyson sphere is problematic. Dyson ring or swarm is more possible. One change, regarding the removal and redistribution of mass of Venus would be a change in Earth's eccentricity cycle, as Venus is one of the key planets that effects Earth's eccentricity, along with Jupiter and Saturn. That ...

1

The cause of the motion of the Sun is the gravitational effects of primarily the outer, massive planets. These also perturb the orbit of Mercury. So rather than "orbiting around a barycentre" you might think of the motion of Mercury and the other inner planets and the Sun as moving in an irregular and constantly changing gravitational field. When ...

1

Mass extinctions have been linked with the Solar System's oscillations up and down through the galactic plane (the Galactic Cycle). You could also take a look at this question.

1

If you want correct values, you have to take into account the effects mentioned in Brandon Rhodes' answer. Nevertheless, here's how to do a quick-and-dirty calculation. The absolute magnitude of a planet is defined as the apparent magnitude if the Sun-planet and planet-observer distances are 1 au, at opposition. Assuming a diffuse disc reflector model, the ...

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