# Tag Info

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What is a name? A name is a word, that is reasonably unique, that is used to identify a person or thing. When a child is born there is no word that identifies it, and so its parents have to choose a "name". Similarly when a new astronomical object, such as an asteroid, is discovered, it has no word that identifies it and so it is assigned first a ...

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The latter. To astronomers, a metal is any element that is not hydrogen or helium, because these elements together constitute most of the elements in the Universe, by far. This means that, in many circumstances all other elements can be neglected, at least to first order. By mass, H and He account for some 74% and 24% in the present-day Universe, ...

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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 ...

29

You make a great point. The reason behind the discrepancy between the dates is due to a complicated history behind it. The calendar is based on the calendar created by ancient Romans, which is based on one Moon cycle. One lunar cycle is 29.53 days. www.universetoday.com/20620/lunar-year/ which does not evenly divide into the 365.25 days of ...

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Of course the Sun and the Moon have names. The names of those objects in English are "the Sun" and "the Moon". Note the use of a definite article ("the") and the capitalization of the names themselves to indicate a proper name. The Sun and the Moon have many names, at least one name for each for almost every language ever spoken....

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It is named 'Sol' and the moon was named 'Luna'. Hence the term Lunar explorer and 'Solar' System.. Other cultures have used different names for our Sun and Moon (for thousands of years) - So actually they have multiple names each. Most people refer to them simply as "The Sun" & "The Moon".

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Breaking the phrase down: Dwarf star - a term I will never understand - is used to describe relatively small, dim stars. Unfortunately, this encompasses most main-sequence stars, which are indeed dwarfs compared to large giants and supergiants. Ultra-cool, as called2voyage already discussed, means that the star has an effective temperatures of less than ...

22

All those adjectives being smooshed together signify an uncommon event. That's why you've never seen them together like that before. All 3 conditions have to hold true: It's a supermoon, which means the full moon coincides with the moons perigee or nearest approach. That can make it appear up to 30% brighter than one at apogee (farthest away). These happen ...

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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 ...

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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 ...

18

Oxford English Dictionary is an authoritative source, but it's aimed at the general public. I think no astronomer will frown upon you when you're using the terms meteoroid and meteorite to describe a small body impacting another body in the solar system. As an example, Wikipedia doesn't impose the limitation that it must hit Earth: A meteorite is a solid ...

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No. These words are English, not Greek. "Periapsis" means the point on the orbit when the two bodies are at their closest. It doesn't matter if this good Greek or bad Greek, it is correct English. Apsis actually derives from "arch" and indicates the two points where the orbital curve is most "arched": ie the points of greatest ...

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All the monthly Full Moons are named e.g. list at timeanddate.com, of which "Harvest Moon" is the one people are probably most familiar with. So the March Full Moon is indeed the "Worm Moon" although rarely referred to as such. The extra hyperbole ("Super", "Blood" etc) seems to be a recent (within the last few years) media phenomenon for unknown reasons...

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What exactly are "non-Keplerian" orbits? Strictly speaking, no orbits are in perfect accordance with Kepler’s laws. Kepler’s laws aren’t really “laws” in terms of physical laws, but are instead trends that Kepler noticed and calculated using astronomical observations of the planets. Kepler’s laws are very accurate for planetary orbits since he ...

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What exactly are "non-Keplerian" orbits? Orbits that don't follow Kepler's laws. Strictly speaking, all orbits are non-Keplerian. In practice, one can model some orbits as basically Keplerian, but with perturbations. Sun synchronous satellites are one example of orbits that are close to Keplerian, but not quite so. The Earth's equatorial bulge ...

14

By definition, the capitalized word Universe denotes everything there is, so even if we one day discovered we're just a part of a Multiverse, all the parallel universes of it would still be parts of the Universe as a whole, where Multiverse would just describe its nature. Or, if some yet undiscovered regions of it would defy our current understanding of its ...

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Wikipedia's entry for Heat Shield Rock says: Heat Shield Rock is a basketball-sized iron-nickel meteorite found on Mars by the Mars rover Opportunity in January 2005. The meteorite was formally named Meridiani Planum meteorite by the Meteoritical Society in October, 2005 (meteorites are always named after the place where they were found) The Meteorical ...

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$\simeq$ and $\approx$ both mean "approximately equal to". I don't think $\cong$ is used so often, but if I read it, I would interpret is as the same as the two others. $\sim$ in principle means "of the order of", i.e. correct to within an order of magnitude. However, astronomers tend to be rather slobby sometimes (we call all elements except H and He for "...

12

"Satellite type" and "Planet type". The terms seem to have been coined by Rudolf Dvorak in 1982 paper "Planetenbahnen in Doppelsternsystemen" Due to the fact that quasiperiodic orbits exist around stable orbits 3 different types of possible planetary orbits are found: S-types (satellite type orbit around one primary), P-types (...

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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'...

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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 $\... 11 If we're going to get technical, Asteroids are not really an official name anymore. In 2006, when the IAU redefined what a planet was (and thus demoted Pluto), they also decided to more formally define other terms to identify objects in our solar system. You can see a diagram of all the official terms and how they relate below. Notice the important factor ... 11 It is possible that there is nothing "official", there is just the technical use of language. For example Phil Plait notes that He incorrectly used the word "orbit" for the motion of the Hayabusa probe, which does not orbit the asteroid Ryugu. But hovers over the surface. So what does Phil mean when he talks about orbiting? I summarize the meaning thus: ... 9 I don't know about names for the planets, specifically, but the orbits are called S-type and P-type: S-type: The planet orbits around one star, and the host star has a binary companion (i.e., "the other kind" in the XKCD comic) P-type: The planet orbits around both stars of the binary 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 ... 9 Consider a child on a stationary swing. The fastest way to get them going is to push once every time they swing (a 1:1 resonance). If you push 581 times for every 137 swings, the pushes will mostly average out and the child won't get very high on the swing. Similarly, there are infinitely many orbital resonances possible, but when the integers in the ... 9 The whole sphere has approximately 41,253 square degrees of solid angle. $$4\pi\left(\frac{180}{\pi}\right)^{2}\approx 41,253$$ so for a hemisphere there should be half this number or about 20,627 deg2. I think you computation is missing the$4\pi\$ steradians in a sphere term. This doesn't solve the disparity however. Perhaps the key is the term "...

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