Questions tagged [terminology]

Questions regarding specific terms, names, or naming conventions.

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Is lithium considered a metal in astronomy?

My lecture notes are conflicting on this issue so I seek definitive clarification. In Astronomy, are metals either A: the elements which form within stars (i.e., not Big Bang nucleosynthesis, where ...
zabop's user avatar
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25 votes
1 answer
7k views

What's the reason that we have a different number of days each month?

It always was interesting for me to understand the answer for the question: What's the reason that we have a different number of days each month? If the month is fixed on the time that the moon ...
Reckless Glacier's user avatar
24 votes
3 answers
7k views

Is the Big Bang a theory or a model?

I ask this because someone mentioned ‘it isn't a theory, it's a model’ in the comments in an old question of mine: Is the expansion of the universe proof of the big bang? I guess defining terms is ...
Kilise's user avatar
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24 votes
3 answers
6k views

What (the heck) is a Super Worm Equinox Moon?

Google News feed shows me the following. What does the term "Super Worm Equinox Moon" mean and has it ever been used before this 2019 clickbait instance?
uhoh's user avatar
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22 votes
2 answers
3k views

What is the name of meteoroids which hit Moon, Mars, or pretty much anything that isn’t the Earth?

A meteorite according to the Oxford English Dictionary is A piece of rock or metal that has fallen to the earth's surface from outer space as a meteor. But, meteors impact other planets. Are they ...
EDL's user avatar
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22 votes
2 answers
4k views

So, what exactly is an 'ultra-cool' dwarf star?

The TRAPPIST-1 system is around an ultra-cool dwarf star. I went looking for more information on that kind of star, and found very little. The Wikipedia article on it lengthened from a minimal stub to ...
kim holder's user avatar
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19 votes
4 answers
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What are "non-Keplerian" orbits? What are some familiar examples in our solar system, and can some still be closed?

This excellent answer to Forms of stellar orbits around the galactic center invokes the following concepts: non-Keplerian orbits closed orbits I have a fairly good idea what these mean and so might ...
uhoh's user avatar
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17 votes
2 answers
3k views

Hydrogen burning vs Hydrogen fusing

Does the term "Hydrogen burning" mean the same as "Hydrogen fusing" in astronomy? If not, then what is the product of "Hydrogen burning"? Assume the product of "...
Jack the Ranger's user avatar
14 votes
4 answers
5k views

Milky Way vs Milky Way Galaxy

I saw this question on Quizlet which said: What is the difference between the Milky Way and the Milky Way Galaxy? And the answer was: The Milky Way is a fairly narrow band of faint diffuse light ...
Jack the Ranger's user avatar
13 votes
8 answers
14k views

Do our sun and moon have names?

We seem to have named every moon orbiting other planets. Why haven't we named our own moon? And for that matter, why doesn't our sun have a name since we name or number stars?
Bookaholic's user avatar
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12 votes
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What is the name of that which exists beyond the Universe?

"The Universe is commonly defined as the totality of existence" but that is more of a philosophical position. Empirically we know (or believe) that it is of finite size some believe it is expanding ...
James Jenkins's user avatar
12 votes
4 answers
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Usage of $\sim$, $\approx$, $\simeq$, and $\cong$ in observational astronomy?

My understanding is $\sim$ generally means "on the order of magnitude of" e.g. $T \sim 10^5$ K $\approx$ is obviously "approximately equal to" so for example one might write $d \approx 400$ pc rather ...
imanorc's user avatar
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12 votes
1 answer
2k views

Name of area close to Local Bubble?

The following image is a map of the area surrounding the Local Bubble. One side of the image is 1700 lightyears. From the Sun to the Hyades (immediately below the sun) it is 150 lightyears. The local ...
user avatar
11 votes
2 answers
2k views

14,000 square degrees

The DESI Legacy Imaging Surveys says it produces a model of “the 14,000 square degrees of extragalactic sky visible from the northern hemisphere”. But I thought the whole celestial sphere (like any ...
Charles's user avatar
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11 votes
3 answers
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What's the meaning of virial in Astronomy, and in particular the expression "a virialized cluster of galaxies"?

The virial theorem relates the kinetic energy of a system to the total potential energy of the system: $ \Delta K = -\frac{1}{2}\Delta V $ so it has lots of uses in mechanics, thermodynamics and ...
Jim421616's user avatar
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9 votes
2 answers
2k views

How do I say the luminosity class aloud?

I have need to say the spectral type of a star for a poster presentation I'm making, which includes the luminosity class. However, I've been unable to determine the standard way of doing so, and ...
mknote's user avatar
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1 answer
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What do the words "p-type" and "s-type" mean?

As explained in various sources (such as that answer), a planet in an s-type orbit orbits one of the stars of a binary star system, whereas a planet in a p-type orbit orbits both stars. A synonym for ...
O. R. Mapper's user avatar
9 votes
2 answers
579 views

Do astronomers generally agree that the distinction between comets and asteroids is not so clear?

edit: I just saw this tweet and find it incredibly relevant :) begin question: See this answer and then consider if there are known or likely solar system bodies that might be identified as both ...
uhoh's user avatar
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9 votes
2 answers
3k views

How does an eclipse differ from an occultation?

A comment in response to this question suggests that an eclipse differs from an occultation in that the former casts a shadow while the latter doesn't. This isn't particularly satisfactory since ...
CatchAsCatchCan's user avatar
8 votes
5 answers
487 views

Do astronomers have an established, systematic way for saying what does or doesn't orbit what? (e.g. "Mars orbits Earth")

A recent comment An object far enough away can certainly orbit the Moon and the Earth (and the Sun) -- Mars, for instance does this. An object in the Earth-Moon L2 is also orbiting both the Earth ...
uhoh's user avatar
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8 votes
2 answers
780 views

At what point are orbital resonances no longer "ordered" but "chaotic?"

Orbital resonances are typically in small valued integer ratios, like 2:1, 3:2, or 4:7. However, there are some resonances whose ratios have large reduced values, including the 73:69 Naiad:Thalassa ...
WarpPrime's user avatar
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8 votes
2 answers
484 views

What is the antonym of "closest approach"?

The distance from Earth to Mars, during their closest approach, is about 55 million kilometers. At their furthest apart, that distance would be about 401 million kilometers. Distance at closest ...
Quuxplusone's user avatar
8 votes
1 answer
431 views

Is there an established distinction between a geyser and a cryovolcano in solar system bodies?

Is there an established distinction between a geyser and a cryovolcano in the context of cold solar-system bodies such as the moons of Jupiter and Saturn, or Kuiper belt objects (e.g. Pluto)? Both can ...
uhoh's user avatar
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8 votes
1 answer
461 views

What is a radio "homology telescope" and is the 500m dish in China one?

This question is about design aspects of large radio telescope dishes which allow them to flex under the influence of gravity as they change elevation angle, and still maintain good optical ...
uhoh's user avatar
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7 votes
2 answers
3k views

Is there a word for an object orbiting a brown dwarf?

In my answer to this question someone posed somewhere: If an Earth-massed moon orbits a planet that has 74-83 times Jupiter’s mass, would the Earth massed moon still be a moon, or a planet? I wrote: ...
M. A. Golding's user avatar
7 votes
2 answers
472 views

What does "additive fringing from the (multiplicative) twilights" mean?

The question How can I make the fringing pattern visible in my flat (twilight) images for filter i? includes: I have a bunch of twilight flats that have been preprocessed (dark, bias, overscan etc.)...
uhoh's user avatar
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7 votes
2 answers
642 views

What's the name for [the other kind of planet] in a binary star system?

This XKCD what-if talks about rainbows on planets in a binary star system. It points out that there are two types: circumbinary planets, where the planet orbits far from and around both stars [the ...
ThePopMachine's user avatar
7 votes
1 answer
174 views

Time period in which a planet rotates

I notice that Wikipedia give two contradictory terms for the time period in which a planet rotates in relation to an infinitely-distant object. In one place this is called a "sidereal day" and in ...
dotancohen's user avatar
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6 votes
3 answers
1k views

"Periapsis" or "Periastron"?

I was taught from Bate Mueller and White, that the proper terms for the closest and furthest points and distances from a body in orbit around another unspecified body are "periapsis" and &...
Connor Garcia's user avatar
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6 votes
1 answer
188 views

Clarification of radio spectrum terminology

For a radio spectrum, when is it called thermal emission, synchrotron emission, self-absorbed synchrotron emission and inverted spectrum? They are all power-law and their difference is power-law index?...
questionhang's user avatar
  • 3,137
6 votes
2 answers
803 views

The defintion of star/planetary/solar system

In many science fiction stories, we hear the term star system that mostly refers to a star and its planets. This is often used interchangeably with the term solar system. But after some research I ...
N van Oosten's user avatar
6 votes
1 answer
223 views

What are other names for planetoids that aren't orbiting a solar system, but hurtling through space?

I'm trying to think of a good word for an asteroid/planetoid that has no stable orbit but has been ejected from a system and is passing close to a sun. Any help?
watercollider's user avatar
6 votes
3 answers
154 views

Does "spectral type" and "stellar classification" refer to the same thing?

Should the tags stellar-classification and spectral-type be merged? has been asked in meta two weeks ago. It requires some careful consideration but so far no response has been forthcoming, so I'm ...
uhoh's user avatar
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5 votes
1 answer
659 views

What is the mnemonic reason behind b being galactic latitude? (in the Galactic Coordinates frame)

I'm not sure if this is a question that has been posted before, and I'm also not sure if the answer is really mnemonic. If that's the case, I'd like to understand why we assigned $b$ to latitude ...
nuwe's user avatar
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5 votes
1 answer
1k views

Sorting out Julian Day, Julian Date, Julian Day number, Julian Day Calendar, and Julian Day Table

In this answer I mention day number which is 1 on the first day of each calendar year (January 1) and increments to 365 or 366 on December 31 of that year. There was an edit proposed, which included ...
uhoh's user avatar
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5 votes
1 answer
335 views

Is there a word or short phrase that denotes the apparently moving part of the lunar limb?

Between new moon and full moon, the moon's disc as viewed from the earth is bounded by a semicircular arc on its right and an arc on its left that moves to the right until at full moon it forms the ...
user avatar
5 votes
1 answer
243 views

Is there a distinction between NEOs and near-Earth asteroids? Is there a difference?

My "real question" is in Space Exploration Meta (neo (near-earth-object) and near-earth-asteroid tags, do we need both?), but I think that astronomers will be able to help understand the situation and ...
uhoh's user avatar
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5 votes
1 answer
436 views

If an earthquake happens on Mars, is it still an earthquake?

Or are seismic phenomenon named differently when they happen on other celestial bodies? If so, what are they called?
Etheryte's user avatar
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5 votes
2 answers
7k views

What is "emission measure"?

Many papers mention emission measure, and some of them give the expression of EM, BUT there is no clear definition of EM. My question is what EM is on earth? Its unit is supposed to be cm-3. How to ...
questionhang's user avatar
  • 3,137
5 votes
1 answer
345 views

When was Hubble tension first noticed? When was this term first used?

When was Hubble tension first noticed? When was this term first used? Who used this term for the first time?
Youngsub Yoon's user avatar
5 votes
1 answer
225 views

Movement of stars over long periods of time

When the Great Pyramid was built, one long sloping tunnel was aimed at a particular star, which could be seen by a person at the bottom of that tunnel on just one night of the year. Today that star is ...
Robert Daseler's user avatar
5 votes
2 answers
148 views

Terminology: Is there a name for the points on the surfaces of tidally locked parent/satellite bodies that always face each other?

This is purely a question about terminology, one that has eluded my googling efforts. When a satellite and its parent body are tidally locked to each other, there is (in an ideal case) a single ...
Brionius's user avatar
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5 votes
1 answer
138 views

What is "superficial gravity"

I have seen the term superficial gravity used and it seems to be equivalent to surface gravity seen, e.g., here http://arxiv.org/pdf/1701.02295 Is there any difference between superficial and ...
imanorc's user avatar
  • 185
5 votes
2 answers
427 views

What's the origin and culture of funny astronomical terminology?

I'm not in the industry myself, but as an interested member of the public the terminology of astronomy seems a bit funny. Astronomers who today talk publicly about the interstellar medium say that the ...
LocalFluff's user avatar
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5 votes
1 answer
316 views

Are meteors and meteorites considered "Small Solar System Bodies"?

The difference between meteorites, meteors, and meteoroids is one of altitude relative to a celestial surface: in space, it's a meteoroid; in the atmosphere, it's a meteor; and on the surface, it's a ...
SarahofGaia's user avatar
4 votes
4 answers
2k views

Is a planetary system star's referred to as their sun?

It's my understanding that the Sun (uppercase) is used to refer to our sun/star, because it is The Sun. Latin name is Sol, hence the Solar System. Even the tag (lowercase sun) on this post has the ...
Eric Warnke's user avatar
4 votes
2 answers
112 views

How are image credits expressed in Astronomy presentations?

Sorry if this is a stupid question. I'm preparing an astronomy presentation, and I want to make sure I give credits where credits are due. But I see credits appear in different formats, for example: ...
CMB's user avatar
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4 votes
2 answers
388 views

What is the term for a star swallowing another star?

A star A goes through the body of another star B, or is swallowed by B. There is no tidal disruption. It sounds like kerzan. Does anybody recognise this pronunciation?
questionhang's user avatar
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4 votes
1 answer
411 views

What exactly is "the rotating lighthouse model" in the context of a double pulsar?

The introduction to Testing the rotating lighthouse model with the double pulsar system PSR J0737-3039A/B (open access) says: The double pulsar system PSR J0737-3039A/B was discovered by Burgay et al....
uhoh's user avatar
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4 votes
1 answer
241 views

How many solar system objects that can really qualify as a KBO are likely to enter Pluto's Hill sphere each day?

A comment below Which celestial body is able to come closest to Pluto? says that Technically, many, many small Kuiper belt objects enter Pluto's Hill Sphere (or sphere of influence SOI) every day. ...
uhoh's user avatar
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