# Tag Info

21

What you could think at first, regarding the orientation of any planetary system, is that it should be roughly in the plane of the galaxy, simply by angular momentum conservation. But, when you take a look at observations, you see that protoplanetary disks orientation is not what you would expect, with no preferential orientation (protoplanetary disks are ...

18

The tilt of our solar system (or any star system) is determined by the net angular momentum of the gas cloud from which it formed. This might be a bit of a vague answer, but over time, the formation of stars and their respective planets is thought to look something like this: Other influences (net forces: maybe nearby massive objects, or other components of ...

16

Any telescope can be made to give you the information that you are looking for. The first thing that you will need to know is the location of the ecliptic which varies throughout the year. Or are you looking to find in relation to the the celestial equator? https://en.wikipedia.org/wiki/Celestial_equator Either way, you would start of the same by find ...

10

That's right. Unlike the Earth, which has a substantial inclination of 23.4 degrees to the ecliptic, the Moon is inclined by only 1.5 degrees. This means that there are no substantial seasons. The moon also spins much more slowly than the Earth. Each "day" lasts for one Earth month. It also means that at the poles there are craters that are completely shaded ...

9

You just need a telescope with a "wedge" mount, (ie one for polar coordinates,) and not one which is simply a pan-and-tilt mount like commonly used for cameras. (BUT, it might be more fun to do it with a sextant -- see below.) With a telescope that has a polar mount, you just need to set it up correctly. That means orienting the base of the mount in the ...

8

While the other answer here and the link provided by Jeremy give excellent explanations, I believe a bit more nuanced reasoning is required. Although the theory of planet formation is currently still incomplete, it is generally accepted that planets form in a so-called proto-planetary disk as a part of stellar formation process. This is backed up by several ...

6

I am assuming that the question you want answered is how to calculate the elevation of an orbit above a reference plane given the orbital inclination with this plane. If so, please update your question to reflect this, heeding the advice given in the comments. Kepler's first law tells us that planets move in elliptical orbits, which we can define as follows,...

6

From its RV graph alone, with no other information, you cannot calculate inclination. This is why RV velocity measurements are typically reported as "$v \sin{i}$", because what you're actually measuring is the orbital velocity projected along the line of sight. Without other information, you cannot disentangle the orbital velocity from the viewing angle. ...

5

Sirius is a binary system, composed of a main sequence star (Sirius A) and a white dwarf (Sirius B). The two orbit each other with a period of about 50 years, and the eccentricity given on Wikipedia is the eccentricity of the stars' orbits around one another. The inclination, according to Bond et al. 2017 - the paper Wikipedia references for both numbers - ...

5

I have managed to find two hypotheses for Uranus's tilt that explain why its moons are also orbiting on a tilted plane. The multiple impacts hypotheses lies on the fact that, if Uranus had become tilted by the force of a single large impact (as was commonly believed), then the moons should have stayed on their original plane. A corrected version of this ...

5

As Wikipedia notes, Since the word 'inclination' is used in exoplanet studies for this line-of-sight inclination then the angle between the planet's orbit and the star's rotation must use a different word and is termed the spin-orbit angle or spin-orbit alignment. In most cases the orientation of the star's rotational axis is unknown. As of now (7/26/...

4

Yes, the Tropics of Cancer and Capricorn are defined as the highest and lowest latitudes where the sun is directly overhead at least one day a year. The sun's highest position appears to move up and down on the sky over the year because of the Earth's tilt, so if the Earth's tilt were greater or lesser, so would be the extent of the Tropics. (Side note: I ...

4

So, basically you're trying to merge orbital inclination to Kepler's laws. The simplest way is to take the measured orbital inclination of the planet, which is constant, and apply the Pythagorean theorem to any given location and that gives you 3 dimensions of distance from the 2 dimensions defined in Kepler's laws. That's probably what Kepler did. (see ...

4

To answer your second question: Upsilon Andromedae c and d have mutual inclination of 30 degrees http://en.wikipedia.org/wiki/Upsilon_Andromedae Note that you cannot calculate mutual inclination by subtracting one inclination from another from exoplanet data catalogs because the "inclination" used in exoplanet studies is a 2D line-of-sight-to Earth ...

3

@NeutronStar's excellent answer sums up the situation nicely: From its RV (radial velocity) graph alone, with no other information, you cannot calculate inclination. This is why RV velocity measurements are typically reported as "𝑣sin𝑖", because what you're actually measuring is the orbital velocity projected along the line of sight. Without other ...

3

Just as tidal forces can push a moon outwards and over time, circularize the orbit, the planet's equatorial bulge has a similar force that draws the Moon into an orbit over the equator. This is true given sufficient time and enough rotation speed for the planet to have a sufficient equatorial bulge. For a formation moon, there should be some similarity ...

3

In a solar system model by Varadi Runnegar and Ghil Earth's inclination varies between 0 and about 0.05 radians (or about 3 degrees) The variation is rather chaotic, but you may note that there seems to have been a qualitative change in the pattern about 60-70 million years ago

3

If you tilt a circular object, then along one axis the length will appear to be shortened, while along a perpendicular axis the apparent size will be unchanged. So you can use that to determine the tilt angle (inclination). If we define $0^\circ$ to be face-on, then when tilted at an angle $i$ away from face-on, the shorter axis will appear to be decreased ...

2

It starts with the formation of the solar system. The solar system started off in a large cloud of gas, under gravity, this cloud started to collapse. Most of the mass was concentrated at the centre which eventually formed into the sun. Due to the conservation of angular momentum, as the cloud collapse it started to spin and form into a disk with a bulge ...

2

Imagine you are patching a plane with circles, instead of patching the sky sphere with circles (which is the same as filling the space with cones). Now, for every circle of diameter D define a square of diagonal D (D=2d). It is easier to patch the plane with squares, isn't it? So you have squares of side D/2*sqrt(2), and that is exactly your DEC_step, for ...

2

I think the best answer is that there is no particular reason. In any planetary system, most orbits tend to stay close to a common plane - close, but not exactly there. Even the big planets are slightly out-of-plane with each other, but the differences are tiny. As you move away from the bulk of the planetary system's mass, smaller bodies tend to be more ...

2

Yes, we can certainly learn things from edge-on galaxies. The easiest things to learn, as you suggest, have to to with the vertical structure of the stars (and gas). For example, our knowledge of how thick galaxy stellar and gas disks are -- and whether this thickness varies with distance from the galaxy center -- comes almost exclusively from studying edge-...

2

It is possible that you have not understood the definition of inclination angle. This is the angle between our line of sight and the orbital axis of the star-exoplanet pair. Maximum amplitude radial velocity variations are seen when the inclination angle is 90 degrees. No radial velocity variations are seen when it is zero. The answer to your question is ...

2

Radial velocity is a measurement in the change of speed of the star towards us, due to the planet's rotation around it. Speed variation change is detected thanks to the Doppler spectroscopy. If the planets rotation plan is orthogonal with our direction of view, then we cannot see the radial velocity change, because the star speed towards us is constant. ...

2

I think you are referring to the orbits of visual binaries, since you are asking about parameters measured from an ellipse. If the orbital plane were at right angles to the line of sight, then the focus of the ellipse defined by the motion of the secondary star would be coincident with the primary star. When you change the inclination, this is not the case, ...

1

I assume you are talking about the radial velocity method. Analysis of a radial velocity curve yields the minimum mass of a planet $M \sin i$, where $M$ is the true planetary mass and $i$ is its orbital inclination (90 degrees would mean the orbital plane is in our line of sight). In general, with no other information that's all you can say. In principle \$...

1

I just want 28.88 deg = 28 deg 53' confirmed. Yes, 0.88 degrees is equal to 53 arc minutes, so 28.88 deg = 28 deg 53'. But the Yahoo source is off in its value. According to this reference, the maximum declination is closer to 28° 44' (28.73°). Title: Extreme declinations of the moon. Authors: Können, G. P. & Meeus, J. Journal: Journal of the British ...

1

Our moon is special. Other planets have relatively much smaller moons. The other rocky planets either have very small moons (Phobos and Deimos are probably captured asteroids) or no moons at all. The giant planets have a central system of moons that orbit prograde around their equator, and a wider system of satellites that orbit in many different orbits, ...

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