# Tag Info

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This isn't exactly an answer to the question as asked, but it's close enough to one that you might find it interesting and hopefully helpful in some way. The gravitational force of the Sun on the Earth is given by $$F_{Grav} = \frac{GM_{Sun} M_{Earth}}{a^2}$$ where $a$ is the semimajor axis of Earth's orbit and is about 1.5E+11 meters and $GM_{Sun}$ is ...

0

You have a good idea. You mentioned 4 effects already (clock accuracy, latitude, time of year, and clear horizon), but there is another effect that is larger than those: atmospheric refraction. Refraction causes a rising object to appear to be half a degree higher than reality. Refraction depends on atmospheric pressure and temperature, so it may be harder ...

2

Humans don't have this capacity. The Earth has a kinetic energy of about $10^{33}$ joules, relative to the sun. Even if we put the total energy that humans use per year into the Earth's orbit (about 10^{24} joules) we still only have one-billionth of the kinetic energy of the Earth. Moreover, the annual changes in temperature have very little to do with ...

0

I'm going to answer this in a definition-based manner. Here is the definition of a Hill Sphere according to Wikipedia: The Hill sphere or Roche sphere of an astronomical body is the region in which it dominates the attraction of satellites. Here is the definition of a Lagrange point according to Wikipedia: In celestial mechanics, the Lagrangian ...

3

To really get exact times, you would have to take into account the opacity of the atmosphere, but I will be ignoring this here, and consider the light flux outside of the atmosphere of any planetary body. There is no [planet] time for planets closer to the Sun than Earth, or for exoplanets orbiting brighter stars than Earth at the same distance. This ...

3

Asteroids with an orbit of between 1.8 and 2 Au (So their closest approach is is about the same distance to the Earth as the Earth is to the sun) are called Hungaria group asteroids, named after 434 Hungaria. Hungaria itself has an orbit of 1.94 AU, so would be a good example of body. Such asteroids are rather rare. There is a gap in the asteroid belt ...

1

TL;DR: the main sequence lifespan of the sun can be increased by a factor of 12.2. Perhaps the most complete astrophysical analysis of stellar engineering for extending Earth habitability is Martin Beech's book Rejuvenating the Sun and Avoiding Other Global Catastrophes (2008). In order to maintain the biosphere the sun's interior need to be mixed (in ...

1

The wikipedia page says Obliquity 7.25°[2] (to the ecliptic) 67.23° (to the galactic plane) Interesting fact: the sun's layers rotate at different speeds, as well as different rates depending on latitude.

61

The asteroid belt is affected by Jupiter's gravity. There are stable orbits inside of Jupiter's orbit. Jupiter's Hill Sphere has a radius of 53 million km. If you are more than 53 million km from Jupiter, then the Sun's gravity dominates and you can orbit the sun. But Jupiter orbits 780 million km from the Sun, so there is plenty of space between Mars and ...

0

I naively thought that noon was midway between sunrise and sunset. I already used a binary solver on elevation to get sunrise and sunset (-0.833 degrees). I added a binary solver on azimuth to get noon (180 degrees). The difference between midway and actual noon was 11 seconds on this day and this location. YMMV.

9

Light flux decreases as one over distance squared. So if Eris is 100 times further away from the Sun than the Earth is, then the amount of light that reaches Eris is 10 000 less than that on Earth. Since a difference of five magnitudes is a factor of 100, The Sun would have an apparent magnitude -16.7 seen from Eris' aphelion, as opposed to -26.7 magnitude ...

2

The Sun is pretty much a blackbody for every purpouse except when looking at it with a rather precise spectrometer. Then again, it is not a constant temperature blackbody. The brightness of these images directly translates to some temperature in the corresponding region of the photosphere. The most bright of them are somewhere 6000K, the darkest pixels are, ...

22

Usernumber's explanation of the light and dark regions is correct, but there is more detail to be added about granulation on other stars. Granulation is expected on other stars with surface convection zones, but the properties and timescales of the granulation can be quite different. On the Sun, the granules appear and disappear in timescales of 10-30 ...

6

I'll add to @usernumber's answer some graphics. Unfortunately we can't yet "has YouTubes" for some reason so I'll just add the links. There are two videos of the Sun linked in Phil Plait's Bad Astronomy article DKIST first light high-resolution video of solar granules DKIST First light video of solar granulation (wide angle). Here are the same kind of ...

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The dark lines are colder areas at the edge of the convection cells, where the cooled down plasma sinks towards the inside of the Sun. The yellow parts are where the plasma rises to the surface. Each yellow spot (which is actually the size of a country) is called a granule, and this web-like appearance is called granulation. In the outer part of the Sun (...

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Models for the future behaviour of the Sun do vary, mainly as a result of uncertainty of mass loss during the red giant (H shell burning) and asymptotic red giant (H+He shell burning) phases. A highly cited paper by Schroeder & Smith 2008 claims that the Sun will reach its maximum size of about $256 R_{\odot}$ (1.18 au) at the very tip of the red giant ...

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Yes, observations of this kind are within the technical scope of amateur astronomers. Several groups succeeded in replicating the experiment during the 2017 eclipse that crossed the USA. For example Donald Bruns measured deflections of 2.8 arcseconds of multiple stars. Nasa published a "How To" page for anyone wanting to test GR themselves.

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Yes, you can see one tonight. Arctaurus is a red giant star with a mass of about 1.1 times the solar mass, so rather similar to the sun. It currently has a spectral type of K0 III. It is ascending the red giant branch, so it's luminosity and spectrum are not stable in the longer term. The sun will pass through this phase, and following a hydrogen flash ...

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Arcturus is a RGB star, probably fairly similar how the sun will look when it becomes a red giant. Arcturus is slightly more massive than the sun ($m_{\rm Arc}=1.08 m_{\odot}$), but the main difference is the lower metallicity of $[Fe/H]\approx-0.5$. This low metallicity reduces the opacity in the stellar radiative zone (which fills a significant portion of ...

5

The Moon does move monotonically eastward relative to the Sun. However, for observers at temperate latitudes, they rise and set at a slant, so any difference in declination affects the lengths of time they are above the horizon. From Boston on 2020-01-24, the Moon is about 3° south of the Sun, making the time between moonrise and moonset about 28 ...

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Right now, the moon is south of the ecliptic (for those of us in the northern hemisphere). This means it encounters the horizon before the sun.

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