Questions tagged [terminology]

Questions regarding specific terms, names, or naming conventions.

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11
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2answers
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 ...
3
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1answer
114 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 ...
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2answers
709 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 ...
4
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1answer
50 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 ...
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0answers
14 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 "...
8
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2answers
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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 ...
1
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1answer
38 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 ...
2
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1answer
67 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 ...
3
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0answers
186 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 ...
10
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3answers
1k 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 ...
12
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4answers
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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 ...
3
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1answer
106 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 ...
-2
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1answer
73 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.
4
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1answer
247 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 ...
2
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4answers
405 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?
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1answer
183 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 ...
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2answers
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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 "...
2
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0answers
29 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 ...
3
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2answers
177 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 ...
2
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2answers
156 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 ...
3
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1answer
304 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....
2
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1answer
75 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)...
2
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0answers
57 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, ...
5
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1answer
638 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 ...
4
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2answers
104 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: ...
6
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2answers
236 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 ...
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1answer
89 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 ...
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1answer
126 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 ...
3
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1answer
27 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 ...
4
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1answer
206 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. ...
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2answers
138 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?
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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?
3
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1answer
91 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 ...
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1answer
121 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 ...
5
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1answer
76 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 ...
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3answers
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 &...
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8answers
11k 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?
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0answers
35 views

Are falling evaporating bodies (FEBs) and exocomets the same thing? How does one know they're falling and evaporating?

Looking for a (short) list of comets with heliocentric escape velocity I stumbled upon Wikipedia's exocoments which like exoplanets, are bound to other stars. I should have been looking for "...
1
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1answer
251 views

What exactly is a Hamiltonian telescope? Is this one?

This comment on the current answer to Why is this telescope so short? How hard is it to make such a fast primary? says In this forum topic Borisov appears to call it an f/1.5 Hamiltonian. Wikipedia'...
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1answer
85 views

Does the Honey moon have a precession problem?

In Steven Colbert's interview with Neil deGrasse Tyson after about 03:16 the following is explained: But wait, all the moons - all the full moons of the year have ...
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3answers
3k views

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 ...
1
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1answer
58 views

Is there an antonym for 'transit', i.e. the transit of a celestial body through the meridian

I'm writing software to calculate the rising, transit, and setting of a body on the celestial sphere for a specific location and date. It seems to me that the opposite of transit, at least in the case ...
4
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1answer
104 views

What exactly are "H30α and He30α images"? (ALMA)

I ran across this paper's title η Carinae: high angular resolution continuum, H30α and He30α ALMA images (arXiv) and see that the body of the paper also mentions "H40α, H30α and H29α". What ...
26
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1answer
4k views

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 ...
2
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2answers
119 views

Can a pulsar also be a magnetar?

I know this is a simplistic question, but I cannot find a straight answer... Also, is it possible most or all neutron stars are magnetars and/or pulsars? It's just hard to see all of their properties ...
9
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1answer
839 views

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 ...
6
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1answer
162 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?...
7
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2answers
373 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.)...
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0answers
102 views

Why is the Nancy Grace Roman Space Telescope (WFIRST) coronagraph considered "(beyond-)state-of-the-art"?

After about 01:30 in the NASA video NASA's Nancy Grace Roman Space Telescope: Broadening Our Cosmic Horizons the narrator says: To deepen its study of exoplanets ...
5
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1answer
152 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?