# Tag Info

42

In stellar astrophysics, "burning" means nuclear fusion, not chemical combustion. So a star burns hydrogen to helium. (Incidentally, normal chemical burning of hydrogen in air produces water). This might seem to be confusing terminology, but it's not an issue in practice because the regions in stars where fusion takes place (the core, and shells ...

22

I think that distinction is wrong, or at least not commonly accepted. We live in a disk-shaped galaxy, which is interchangeably called "the Milky Way", "the Milky Way Galaxy", or "the Galaxy" (capitalized to differentiate it from other galaxies). Viewed from inside, it looks to us as a narrow, diffuse band of light because we ...

22

Milky Way vs Milky Way Galaxy I recommend recognizing and honoring the distinction! The two words being interchangeable is a narrow view that only one well versed in Astronomy can have, and doesn't fit the reality of how ordinary people view it, being the circa 1010 people who have seen the Milky Way but never having been formally taught about galaxies. The ...

12

Länge und Breite are the German words for longitude and latitude. Thus 'b' seems like a natural choice for latitude and 'l' for longitude. A century ago when traditional choice of variable names were chosen by vote of feet, a reasonable amount of research papers were still published in German or people with some form of fluency in German. At the same time it'...

12

A slightly modified version of the virial theorem that you cite states that for a system of N bodyes (galaxies in a cluster) autogravotating $${1 \over 2} \ddot I = 2K + V$$ Where $K$ is the total kinetic energy, $V$ is the total potential energy and $I$ is the "scalar moment of inertia" of the system, defined as $$I = \sum_i^N m_i r_i^2.$$ When $\... 9 All the various answers are making the same correct point in different ways, but I still can't resist saying this: When you are talking about galaxies, and you want to specify our own, you can say either "the Milky Way" or "the Milky Way Galaxy." They are both fine for talking about the whole galaxy as one among many, and Quizlet is ... 9 According to the Wikipedia article on the Virial Theorem: The word virial for the right-hand side of the equation derives from vis, the Latin word for "force" or "energy", and was given its technical definition by Rudolf Clausius in 1870. Investigating this further, one can see from the original publication of Rudolf Clausius that ... 9 The luminosity classes are indicated by Roman numbers. So you pronounce them as numbers if you don't spell out the actual name of the luminosity class you are referring to. Pronouncing them as letters would sound wrong and - at least to me - incomprehensible. The preferred way is to actually use the luminosity class name like 'dwarf' for V etc. More ... 8 (Physical) cosmology analyzes the universe on its largest scale. Rather than studying individual objects in the universe, it focuses on the overall universe's properties (its shape, composition, age, etc.) and its evolution (how it originated, how it's changing, and how it will end). "Astronomy" is a less precisely defined term. In its broadest ... 8 Usually when spoken aloud, you say the actual description of the class, e.g. "main sequence", "giant", "sub-giant", and so on. In this case you would say "Em four main sequence." 7 Yes, it's the same thing. Usually the phases a star goes through (if big enough) are the hydrogen burning helium burning ... and the phase is named after the element which is being fused into a heavier element. Thus hydrogen burning is the phase where hydrogen is fused into helium. Helium burning is the phase where three helium are fused into carbon; ... 7 There is no conventional format, really. For publications purposes if one uses data from a telescope or image or code created by someone else or similar, the source usually requests being cited or acknowledged in a form specific to their own taste. Some examples include what you quoted or “This paper makes use of the following ALMA data: ADS/JAO.ALMA#******. ... 7 Why do some call the no-hair conjecture the no-hair theorem? Perhaps they mean something specific, or perhaps they don't know any better... you'd have to examine it on a case-by-case basis. Perhaps a better question is: are there reasons why someone would be motivated to say theorem instead of conjecture? Sometimes people call unproven mathematical ... 6 The Hill sphere radius of Pluto is about$r$= 6 million km. Most of the Kuiper belt is in prograde motion around the Sun (like Pluto). Pluto's average speed is under a lazy 5 km/s for an orbital period of about 248 years. If the difference in orbital speed between Pluto and an average KBO is just 1 km/s, then Pluto will "sweep out"$\pi r^2 *86,...

5

It seems that the authors are just referring to the accepted model of a pulsar, i.e. a neutron star spinning and emitting beams of radiation at its poles. In that sense, the term is used here no differently than it would be in the context of an isolated pulsar. It's just a very simple way of visualizing why an observer far away appears to see periodic pulses ...

5

Black dwarfs, if they existed now, would be classified as "compact objects". The only reason that you won't see them on the list is that the the universe hasn't existed long enough to produce them. The compact objects that exist in the universe now are white dwarfs, neutron stars and black holes. though see https://public.nrao.edu/news/cold-white-...

5

Saying a star is "fainting" is simply an error; the correct terminology is "dimming" or "fading". (I suspect it's a plausible mistake for non-native speakers if they know about the adjective "faint", which is common in astronomy -- why wouldn't "to faint" mean "to become fainter"? But it doesn't.) ...

5

The term "maximum separation" is often used, though maximum separation can also refer to the maximum angle between two bodies in the celestial sphere. Here is an example from Quintana and Lissaur of the usage referring to distance: close binary stars with maximum separations $Q_B≤0.2 AU$ and here is an example from Nouh of the usage referring to ...

5

A lot of people vaguely call The Milky Way Galaxy simply the Milky Way, but I don't approve of such vague speech which blurs the distinction between two separate things. The Milky Way is a faint band of light in the night sky, which can been seen where the background sky is dark enough. The Milky Way is thus an appearance, or a sighting, or an illusion. Just ...

4

I'll note that the only use of "/" in your list seems to be in "ESA/Hubble", and I suspect this is supposed to mean something like "the part of ESA [European Space Agency] devoted to Hubble". It shows up on the esahubble.org website a lot, for example. So the best way to think about this may be: "Only use '/' when it's part ...

4

You use this from https://planetarynames.wr.usgs.gov/FeatureNameRequest. You need to follow the rules as set out in https://planetarynames.wr.usgs.gov/Page/Rules as well as following the themes for naming Moon based features https://planetarynames.wr.usgs.gov/Page/Categories.

4

The precise definition of "homologous" seems to change based on who you talk to. A general umbrella definition is that a homologous radio telescope preserves a particular type of shape as it moves. Unless you can build an unfeasibly rigid dish, gravity will naturally shift the positions of different parts of the dish in different ways, changing the ...

3

In view of the various (and varying) answers above (3 at the current posting: Sir Cumference, Allure, User123), the relevance of this annoyingly challenging question is established. Nevertheless, the posted answers seem to contradict themselves, if not containing contradictions individually. Even if there seems to be agreement that Cosmology and Astronomy ...

3

Cosmology is a subfield of astronomy. Cosmology deals with very big things (even by astronomical standards). Astronomy on the other hand is an umbrella term that includes lots of smaller-scale stuff. Here are some topics in cosmology: Hubble expansion Big Bang nucleosynthesis Cosmic Inflation Quintessence Cosmic Microwave Background Here are some topics in ...

3

No, they are not the same. Astronomy basically represents the "old science" about the universe: predicting motion of the stars and planets, eclipses, and so on. Look on astronomy as something Greeks would do (but it is not equal to their astronomy; many other modern methods have evolved since then, like neutrino, X-ray or gravitational-wave ...

3

I think this is largely a matter of what you decide is incremental as opposed to a generational change. The basic location and overall size and detection principle of the interferometers did not change. An important change to the interferometer configuration was the addition of the signal recycling mirror that allows a certain amount of "tuning" of ...

3

Are the dispersion directions of the prism and the grating in Hubble WFC3 UVIS G280 perpendicular? No. Can we call this a "grism"? Sure. (Everyone who works with it does.) With cross-disparsion? Perhaps, though it's really not clear if there is meaningful cross-dispersion going on, and if there is, it doesn't serve any useful purpose. All the ...

2

To directly answer your question, the other answer is correct: The United States Geologic Survey's Astrobiology office handles ad hoc US submissions to the International Astronomical Union's nomenclature committee, so their form is what you would need to fill out. Nomenclature across the solar system has been set by the IAU to follow themes based on ...

2

In the linked article by A. Bouchard and another by J. Daley, the words "in the journal Lunar and Planetary Science" link not to a journal article but to a poster in a K-12 education session at the 2017 Lunar and Planetary Science Conference. First author Kirby Runyon told Universe Today in 2017 that he would not submit this geophysical definition ...

2

Tl;Dr: It is a matter of consideration if you want to call Kuiper belt bodies/Oort cloud bodies "asteroids" or not. Long answer: The Oort cloud defines the cosmographic boundary of the Solar System and the extent of the Sun's Hill sphere and hence it is loosely bound to the Solar System, and thus is easily affected by the gravitational pull both of ...

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