# Tag Info

11

Not in any way, no. The December solstice is the moment when the Sun reaches its southernmost point in its daily path in the sky (the June solstice, when the Sun reaches its northernmost point). It only depends on the tilt of the Earth on its orbit and the Sun. On the other hand, Jupiter and Saturn being in conjunction is a phenomenon that doesn’t depend at ...

8

Strictly speaking, a conjunction is when two objects appear at the same right ascension or ecliptic longitude. These are not exactly the same but are usually close since the major planets remain near the ecliptic. When Venus or Mercury is in conjunction with the Sun, we distinguish between inferior (near side) and superior (far side) conjunction. The outer ...

7

@Glorfindel's explanation is very clear. I wondered about how big of an effect "everything else" would have, but I couldn't figure out how to add an image to a comment. Here is a graph from 2018 to 2023 of the distance between Mercury and Earth. You can see every 3rd minimum is a bit deeper than the others just like Glorfindel said. The details of ...

6

The text you quoted (is that from your textbook?) uses a simple approach; it counts every closest approach of Mercury to Earth, not just the ones which occur when Mercury is relatively far from the Sun (and hence closer to Earth). That means you don't need to account for the orbit of Mercury is noticeably elongated precession of the perihelion of the orbit ...

6

It depends how you define “conjunction.” For example, this year, Jupiter and Saturn will be at the same ecliptic longitude and the same right ascension within hours of each other on December 21, 2020. However, in 2000, they were at the same right ascension on May 30, but at the same ecliptic longitude on May 28, 2000. I have done calculations (using the ...

5

Precession of the equinox, caused by the cyclical change in the direction of the Earth's tilt, causes the position of the vernal equinox (the point where the path of the sun crosses the celestial equator) to move over time. When the constellations were first described, the vernal equinox was in Aries, and so it is still called "The First Point of Aries&...

5

Telescopes magnify, they don't bring you closer. So if from Earth Jupiter has an apparent radius of 0.01 degrees (measured as an angle because it is the apparent size) And if Saturn has an apparent angle of 0.005 degrees, then if you magnify 100x then Jupiter will have an apparent size of 1 degree, and Saturn would have a size of 0.5 degrees. Magnification ...

5

A conjunction is when two objects have the same Right Ascension (ie the same longitude in the sky) When planets have conjunctions they will be close to each other, since they follow the ecliptic. The time of conjunction might not be the time of closest alignment. A conjunction is a moment in time you can only have two planets in conjunction, not three or ...

3

As the phase angle of Venus changes, so does its distance to Earth. More about modeling the phase angle dependence of apparent magnitude can be found in this answer to Calculating the apparent magnitude of a satellite. For more on that subject, see What is the difference between albedo, absolute magnitude or apparent magnitude? and also these: 1, 2, 3. When ...

3

I found references which indicate that Venus usually goes dark. Check out the graphs in this paper for one example. The exceptions happen when Venus' orbit, which is slightly out of the ecliptic, brings it to inferior conjunction when projected onto our (Earth's) orbital plane, but Venus remains at a slight angle relative to our viewing lines. From ...

2

How often do Venus and Saturn come together in the sky like this? Sagittarius is between November 22 and December 22 (2019, UT1). The "List of conjunctions (astronomy)" (2015-2020) says that they have had conjunctions on: Date           Time UTC Planet Angle distance  Planet Elongation to Sun January 9, 2016 &...

2

On the evening of the 27th, Venus and the moon were not in conjunction. They didn't have the same right ascension. However, from Europe they did have about the same azimuth, so would have appeared with Venus above a crescent moon in the sky. This is, presumably, what the reporter meant by "vertical conjunction", but that is not a technical term. And while ...

2

Saturn has a diameter of about 116,000 km and is about 1.4 billion km from Earth. For Jupiter, the corresponding numbers are 140,000 and about 800 million km (the distances vary somewhat as the planets move around the Sun. The size of the images of the planets is determined by the ratios of these, so Saturn is about $$\frac{116000}{1400000000} = 0.00008$$ ...

1

Astronomers and astrologers use different boundaries. In this image: The blue lines mark the IAU constellations, standardized in the late 1920s along the equatorial coordinate grid of 1875 and now linked to the positions of several quasars. The red lines mark the tropical zodiac signs, equal 30° divisions of the ecliptic linked to the equinoxes and ...

1

Here is 13 hours 48 minutes. That's a mighty early sighying: https://www.universetoday.com/107700/ultra-thin-young-crescent-moon-sighted-from-u-s-southwest/ 11 hours 40 minutes was the world record as of 2014.

1

Wow, DE431 covers a wide range of dates. The main weakness of your approach is that you only check every month. The inner planets, in particular, move rapidly between constellations. If Mercury is in Aries one the first day of one month, and Venus the next, your search will not find a match, even though they might both have spent most of the month in the ...

Only top voted, non community-wiki answers of a minimum length are eligible