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Questions tagged [terminology]

Questions regarding specific terms, names, or naming conventions.

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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
-1 votes
1 answer
201 views

Is REDSHIFT one word or two?

I (myself) prefer one but an editor I use redlines it as a misspelling, so which one should we use here?
Curious Cat's user avatar
0 votes
2 answers
222 views

Why do we not call black holes black stars or dark stars?

I've never understood why the term black holes are widely used to describe what is actually a black star or dark star. I mean why name something just because of its extreme space curvature effects? In ...
eBookworm's user avatar
  • 145
2 votes
1 answer
120 views

What are the differences between different types of flux density in radio astronomy?

I am new to radio astronomy and have started to analyze some radio observational data of pulsars recently. I am wondering about the differences between "peak flux density", "integrated ...
tzu18's user avatar
  • 23
0 votes
1 answer
194 views

Following Meeus's Astronomical Algorithms for the Calculation of JD

For the Calculation of Julian Day (JD), I followed Chapter 7 of Meeus's Astronomical Algorithms. I could get the numbers mentioned in Example 7.a and 7.b. On the basis of these methodology, proceeded ...
Smarty's user avatar
  • 73
0 votes
2 answers
240 views

What exactly is an aerolite?

I have found definitions calling it a stony metiorite, calling it a meteor of silicate, a granite meteorite, or even calling it a metallic rock from space and more. What is the actual definition?
Starship - On Strike'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
  • 435
3 votes
1 answer
66 views

Is "monochromatic source" different than "monochromator" in astronomical instrumentation?

I got a comment to replace "monochromator" by "monochromatic source" for a paper on an astronomical instrument. The latter seems less specific for no reason. Is there an agreement ...
PaoloH's user avatar
  • 165
3 votes
2 answers
79 views

Is there a term for a Venus visibility period

Is there a term for the period of time when Venus is first visible in the evening to when it switches to being the "morning star", or vice versa? For example, as depicted in the image below,...
Greg Miller's user avatar
  • 5,922
1 vote
1 answer
101 views

A night caused by an eclipse

Is there a term or a name for the darkness caused when a planet eclipses its moon? For example; if people lived on Titan, a small portion of the near sides lunar day would be eclipsed or partially ...
Erik Strife's user avatar
5 votes
1 answer
228 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
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
2 votes
1 answer
181 views

Why is it called "The LOFAR 'superterp'"? What is a terp, and what's so super about this one?

Wikipedia's Low-Frequency Array (LOFAR) includes the image below with the caption: The LOFAR core ("superterp") near Exloo, Netherlands. The bridges give an idea of the scale. Question: ...
uhoh's user avatar
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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
  • 383
3 votes
1 answer
174 views

Is it still called an orbital resonance if the ratio is irrational?

Previously, I asked At what point are orbital resonances no longer "ordered" but "chaotic?", and received an answer from @CarlWitthoft: Perhaps if the calculated fraction had an ...
WarpPrime's user avatar
  • 6,673
8 votes
2 answers
785 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
  • 6,673
4 votes
3 answers
156 views

Orbital terminology for satellites relative to one another

Basic question, but I'm trying to describe a planetary system and coming up short on vocabulary. Do either of the following exist?: A word for the closest pass between two satellites orbiting the ...
the-baby-is-you's user avatar
1 vote
0 answers
61 views

How does one think about optical depth in the context of gravitational microlensing? Is it measured or deduced from observations? Used for planning?

This excellent answer to Which studies prior to 2018 "claimed to find evidence of extragalactic planets in the Andromeda galaxy"? Which instrument was used? introduces the technique of "...
uhoh's user avatar
  • 30.5k
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
  • 133
1 vote
1 answer
57 views

Envelope Enrichment?

While I was researching about planet formation, I repeatedly came across the term envelope enrichment. What does this mean? I searched it up and looked at many websites, but no helpful definitions ...
asterism's user avatar
3 votes
1 answer
167 views

Are the dispersion directions of the prism and the grating in Hubble WFC3 UVIS G280 perpendicular? Can we call this a "grism"? With cross-disparsion?

Prologue From Into the UV: A precise transmission spectrum of HAT-P-41b using Hubble's WFC3/UVIS G280 grism: The UVIS grism, however, comes with several quirks that make it difficult to observe with ...
uhoh's user avatar
  • 30.5k
3 votes
0 answers
211 views

Did a watch company really try to sue radio astronomers for using the word "pulsar"? If so, which astronomers?

After about 48:37 in the really wonderful video Jocelyn Bell Burnell Special Public Lecture: The Discovery of Pulsars (linked below) Dr. Bell Burnell describes the ...
uhoh's user avatar
  • 30.5k
11 votes
3 answers
2k views

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
  • 2,538
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
3 votes
1 answer
381 views

Why do some call the no-hair conjecture the no-hair theorem?

This excellent answer to Why would a black hole's magnetic hair being short-lived not violate the no-hair conjecture, but long-lived hair would? How long is “long-lived”? has got me thinking because ...
uhoh's user avatar
  • 30.5k
-2 votes
1 answer
91 views

Why are white dwarfs being classified as compact objects instead of black dwarfs?

Why are white dwarfs being classified as compact objects instead of black dwarfs? As a black dwarf is the end stage of a white dwarf.
Jack the Ranger's user avatar
4 votes
1 answer
597 views

What is the difference between the terms collision and merger? How are they used differently in Astronomy?

We often hear of mergers of two stellar objects but we also sometimes talk about these or much smaller objects like planets or asteroids colliding. What is the actual differences between Astronomy and ...
uhoh's user avatar
  • 30.5k
2 votes
4 answers
1k views

What are the differences between astronomy and cosmology?

Are astronomy and cosmology same? If not, what are the differences? And which one is greater in terms of subject area?
S. M. JAHANGIR's user avatar
3 votes
1 answer
230 views

The sun "burns" hydrogen and even has "campfires" on it, but has anyone calculated a rate of actual chemical burning on the Sun?

Answers to Hydrogen burning vs Hydrogen fusing explain that in astrophysics "burning" generally refers to nuclear fusion or at least nuclear reactions1, and information at Why didn't we ...
uhoh's user avatar
  • 30.5k
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
2 votes
0 answers
31 views

About the formation of ultra diffuse galaxies (UDGs), what are "failed L∗ galaxies"?

Recent studies show that ultra diffuse galaxies or UDGs were formed by tidally disturbed dwarf galaxies and failed L∗ galaxies. So I've been searching for the failed L∗ galaxies but can't find what it ...
INHYUK PARK's user avatar
3 votes
2 answers
452 views

How is phase defined in a binary orbit with eccentricity?

Are orbital phases of the black spot in the figure measured from some angle or time/period? Usually, how is phase=0 defined? It is relative to the line of apses perhaps with phase=0 at periastron? Any ...
questionhang's user avatar
  • 3,137
3 votes
2 answers
332 views

Is the difference between LIGO & Virgo and their "Advanced" versions really generational, or were these just planned incremental upgrades?

I just learned the term "third generation gravitational wave detector" in answers to What would a kHz gravitational wave detector look like? (mountains on millisecond magnetars) How would it ...
uhoh's user avatar
  • 30.5k
4 votes
1 answer
413 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
  • 30.5k
2 votes
1 answer
108 views

Is Sofia a radio telescope proper?

I usually think of SOFIA, the Stratospheric Observatory for Infrared Astronomy as an infrared optical telescope: SOFIA uses a 2.5 m (8.2 ft) reflector telescope, which has an oversized, 2.7 m (8.9 ft)...
uhoh's user avatar
  • 30.5k
2 votes
0 answers
157 views

How can the CMB have a "monopole anisotropy"?

Wikipedia's Cosmic Microwave Background (CMBR) radiation monopole anisotropy (ℓ = 0) says When ℓ = 0, the ${\displaystyle Y(\theta ,\varphi )}{\displaystyle Y(\theta ,\varphi )}$ term reduced to 1, ...
uhoh's user avatar
  • 30.5k
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
  • 771
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
  • 43
8 votes
2 answers
485 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
1 vote
1 answer
98 views

Defining a nautical mile

Astronomy is new to me so my question might be stupid: I read that a nautical mile is defined as one minute of latitude along any line of longitude. What if it was the other way round, i.e. one minute ...
Ambica Govind's user avatar
1 vote
1 answer
192 views

Are there actual asteroids in the Oort cloud?

This answer to At what annual rate are new exoplanets being recognized? How does it compare to new asteroids? shows that the rate of new asteroid discovery is roughly two orders of magnitude higher ...
uhoh's user avatar
  • 30.5k
3 votes
1 answer
33 views

Timing based on upper or lower part of sun/moon

When you time an astronomical event, such as the moon/sun rising above the horizon, do you note the time when the the first sliver breeches the horizon or when the bottom of the moon/sun just becomes ...
Bookaholic's user avatar
  • 1,559
4 votes
1 answer
242 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
  • 30.5k
2 votes
2 answers
215 views

How does one go about submitting a name for a newly-discovered lunar crater?

Suppose I discover an uncatalogued crater on the lunar surface, and decide to name it. How would I submit my proposed name to the IAU?
jw01's user avatar
  • 23
0 votes
0 answers
38 views

How does one go about naming a lunar crater? [duplicate]

Suppose I discover an uncatalogued crater on the lunar surface, and decide to name it. How would I submit my proposed name to the IAU?
user avatar
3 votes
1 answer
105 views

What happened to the 2017 proposal on redefining planethood? Is this information available?

In 2017, Alan Stern et al. submitted a geophysical planet definition to the IAU for review which states “A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has ...
Greenhorn's user avatar
  • 397
1 vote
1 answer
275 views

Launch windows for Venus transit; how to convert heliocentric longitudes to date?

Being a bit familiar with celestial mechanics, I know that the Hohmann transfer orbit is the quickest way to transfer between two circular orbits of different radii around a central body in the same ...
B--rian's user avatar
  • 5,616
6 votes
3 answers
161 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
  • 30.5k
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
  • 16.3k
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
  • 1,559