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 ...


22

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 ...


21

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 ...


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 ...


16

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...


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 ...


14

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 ...


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: ...


10

$\simeq$ 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 "...


8

It is far from empirically known that the universe is finite in size. The observable universe is certainly of finite size, but that is just a product of the constraints of our observation. We don't know for sure whether the universe is finite or infinite, bounded or unbounded. [Source] What we do know is that right now the universe looks very flat as far as ...


8

'Radial direction' typically means from the center, moving outwards. Typically, these kinds of studies will break a galaxy up into several annuli, or rings, and examine the star formation activity within each ring. (Imagine drawing a series of concentric circles, each one a little bigger than the last.) Then, if the star formation rate or star formation ...


8

According to Spectroscopic Properties of Ultra-cool Dwarfs and Brown Dwarf by J.D. Kirkpatrick, the working definition of ultra-cool dwarf is: dwarfs having classifications of M7 or later. That is referring to the stellar classification system which categorizes stars by their spectral characteristics. Class M stars have a surface temperature less than ...


8

A supermoon is when the full moon occurs at the time when the moon is at its closest point to us in its elliptical orbit. This means that the moon is slightly bigger (honestly, you wouldn't notice it unless you made careful comparisons) and a chunk brighter than normal full moons. Except that supermoons happen three or four times every year, so, actually, ...


8

No. (I'll note that this usage is arguably erroneous, since the nominal meaning of "intrastellar" is "within or inside a star".) First, I personally have never heard anyone use that term in my twenty-five-odd years as an astronomer. Second, a full-text search of the astronomical literature on the NASA Astrophysics Data System turns up a grand total of 51 ...


7

Since a full moon happens once every 29 days (and that's not exact, but close enough), the longest period of time where you can have 11 full moons but not 12 is 11 x 29 + 28, or 347 days, so in a normal year, it's not possible. There are slight variations in the time between full moons but not nearly enough to make up the extra 18 days needed. So you'd ...


7

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


7

As pointed out in the comments, some do prefer to use different terms for quakes on other bodies, and you can see here that "marsquake" does have scholarly usage. That said, there is also scholarly usage for "earthquake" in this context. If you think about it, this makes sense given that one definition of "earth" is "the substance of the land surface", i.e. ...


6

There are thirteen modern constellations in the Zodiac. In modern astronomy, a constellation is a specific area of the celestial sphere as defined by the International Astronomical Union. In total, there are 88 constellations. Astronomy and Astrology are not the same thing. Astronomy is a science while Astrology is not. As such, I'll restrict myself to the ...


6

I think the answer to this is that it doesn't have a name because such "ditches" don't occur for real meteor impacts. In movies and tv shows, these ditches are often shown as being caused by the meteor first hitting the ground at some angle, then sliding across the ground, digging out a ditch along the way, until they come to their final resting point where ...


6

However, due to the Law of Conservation of Energy, I suspect that energy will be all that is left, only in equilibrium meaning no ability for energy to form matter. The law of conservation of energy states that energy is conserved in a closed system. This means the Universe, which is likely an open system, does not necessarily have to obey that conservation ...


6

Yes, Near Earth Objects (NEOs) include asteroids (Near Earth Asteroids (NEAs)) and a few percent of comets (Near Earth Comets (NECs)). As shown by the Update to Determine the Feasibility of Enhancing the Search and Characterization of NEOs (NEO SDT Report) in Section 2.3, the risk from Near Earth Comets is about 1% that of asteroids. So "NEO" tends to be ...


5

The term you're searching for is probably accretion (I guess it might sound similar to a kerzan if the speaker had a cold or the listener couldn't hear it well enough for other reasons). This term is not limited to close binary stars (accreting binaries) cannibalizing each other because they orbit each other at such proximity that the L1 Lagrange point ...


5

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 ...


5

When one body has a much larger mass, so it's motion is negligable, it can be called the central body (even for eccentric orbits, where the central body is a the focus of the ellipse, and far from the centre) This is the terminology used by Wikipedia editors The central body in an orbital system can be defined as the one whose mass (M) is much larger ...


5

There are a number of terms for these things: conjunction: When two objects have either the same right ascension or the same ecliptic longitude (usually as observed from Earth). That is, they lie in (almost) a straight line from the point of view of the observer. In the case of the Solar System, such as when the Sun and Venus line up from the point of view ...


5

This is a neat question in that it made me think deeper about the word "orbit". The answer that mentions barycenters has a point, but in the end, it is a bit about references frames. Let's take a relatively uncontroversial statement and make it controversial. "The Moon orbits the Earth". I would have never challenged this statement, except that once I ...


5

Having some experience with the only logarithmic unit in regular use (the dB, for sound intensity), I have to say: please, no. A logarithmic representation can be handy in some cases. This chart is an excellent example of what can be done if you choose the scale on your image correctly. Note that this has been done without introducing a new unit for ...


5

The Julian Date (JD) is the real number of days since 12:00 UT, January 1, 4713 BCE (proleptic Julian calendar). The Julian Day Number (JDN) is floor(JD), the nearest integer ≤ JD. The Modified Julian Date (MJD) is JD - 2400000.5, or the real number of days since 1858-11-17 0:00 UT. The IAU officially approves either JD or MJD as long it's clear which ...


5

I don't work with black holes, but I've been in the field of astrophysics for several years now, and until I read this question, I had never heard of either the two terms. But a query on NASA/ADS, the primary database for "professional" astronomical papers (both refereed and non-refereed) yields 54 hits for "peribothron" vs. only 10 hits for "perinigricon". ...


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