The science dealing with objects and phenomena located beyond Earth. In particular, this applies to observations and data. At its core, astronomy is the physically informed cataloging and classifying of the contents of the universe in order to better understand what is out there.
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366 views
What accounts for the discrepancies in my calculations of year lengths?
A common exercise in many introductory astronomy texts is to use the lengths of various kinds days to calculate the approximate length of the corresponding year.
For example, ratio $k$ of the length ...
4
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1answer
68 views
Could a bipolar nebula be produced by a time gradient?
M2-9 is an example of a bipolar nebula that resembles two back-to-back rocket nozzles. Is it possible that this shape (somewhat unusual for an explosion) is the result of a time gradient? A rotating ...
4
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1answer
263 views
Is there a simple yet accurate formula for where on Earth the Sun and Moon are directly overhead?
I'm trying to improve a site that shows the region of the Earth currently under daylight, and I
need a formula that, given the current time, tells where
(latitude/longitude) the sun and moon are ...
3
votes
1answer
265 views
Magnitude of New Comet C/2012 S1 (ISON)
A new comet (magnitude 18.8) has been discovered beyond the orbit of Jupiter.
Comet ISON will get within 0.012 AU of the Sun by the end of November 2013 and ~0.4 AU from of Earth early in January ...
2
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1answer
44 views
What information about a meteor's trajectory, size, or height can be derived from a single location?
If one sees a meteor, is there any way to get even a rough approximation of its height, entry angle, size, or other characteristic without triangulation from another position?
If it appeared as a ...
2
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1answer
97 views
The validity of the Longitude of Perihelion
As I understand it from Astronomical Algorithms, by Jean Meeus, the Longitude of Perihelion is a very common numeric value associated with planets, even used as one of the planetary orbital elements. ...
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177 views
How accurate are Mayan astronomical “ephemerides”?
Because of the hype surrounding the "end" of the Mayan calendar (along with the usual cultural relativism and Western guilt) it is nearly impossible to find an objective quantitative assessment of the ...
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115 views
Optimal telescope size?
Consider a diffraction-limited telescope with unobstructed aperture $D$. Such a scope is capable of yielding an angular resolution $\alpha$ that scales as $\lambda/D$, with $\lambda$ denoting the ...
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209 views
Why is my approach to the equation of time off by a constant?
I'm trying to better understand the causes for the equation of time by deriving an approximation from first principles.
My naive approach, $EOT_{NAIVE}$, is to take the difference between the right ...
4
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151 views
Mirrors and light beam divergence technology limits
There are many applications for orbital space mirrors in astronomy (better telescopes) and space propulsion (solar power for deep space probes), but this is limited by the minimum beam divergence ...
3
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126 views
Determine date of birth from “astrological” signs?
Suppose someone tells me what constellation the Sun, Moon, Mercury,
Venus, Mars, Jupiter, and Saturn were in when they were born, and the
information is astronomically accurate (ie, not astrological ...
3
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0answers
176 views
Why are solar eclipses more common in the southern hemisphere?
I've seen the claim that solar eclipses are more common in the southern hemisphere than the northern hemisphere and would like to understand why and if that is the case? Does it relate more to the ...
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73 views
Parallax Cloud Displacement - Angular Distance from Geostationary Satellite
When observing clouds from a geostationary satellite, they appear displaced because of the parallax effect. The satellite looks at the clouds "at an angle" and it projects them on a point of the earth ...
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62 views
Elimination of the node
Recently I have been reading a lot of astronomy papers on reductions in models of the solar system. A reoccurring concept is the elimination of the node. However, they never explain what the node is ...
2
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0answers
123 views
Future space-based telescope array
Radio-telescopes (e.g. the Very Large Array (VLA)) can simulate one gigantic dish by using separate smaller dishes.
Q: Could such an array of optical telescopes potentially see an exoplanet at say 20 ...
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0answers
54 views
Could a Class A Stellar Engine Use A Brown Dwarf
Could a class A stellar engine (or maybe a class C one) be built using a brown dwarf (for argument's sake, a T-dwarf like Gliese 229B)? Would it be capable of enough thrust to move itself any ...
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0answers
66 views
Calculating distance to an asteroid on a given day
I'd like to calculate the distance between the Earth and an asteroid at a given date. Is this possible using the data from JPL's small-body database? Is there a better way?
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0answers
135 views
Angular Diameter, Parallax - Perceived size of Objects
I'm currently in the process of writing a 2.5D Application that should display the perceived size of an Object. For example, When I have a ball that has a diameter of 1meter, how big would it appear ...
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27 views
Information-theoretic limits in observational astronomy
It seems to me that with ever larger and better telescopes and powerful statistical methods, humans are gleaning surprising amounts of information from observations of distant stars. I am especially ...
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116 views
What is the angular distance between Ptolemaic perigees of Mercury?
In his excellent treatment of the history of the science of astronomical distances and sizes, Albert van Helden says (p.29) that
The complicated [Ptolemaic] model of Mercury has the curious ...
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216 views
Is the conclusion that the cosmic burst observed in the Draco constellation from gamma rays that are streaming towards a massive black hole correct?
Referencing this news article:
http://www.smh.com.au/technology/sci-tech/cosmic-burst-in-far-away-galaxy-puzzles-nasa-20110408-1d6kz.html
It also references an event id:
(GRB) 110328A
The article ...
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votes
0answers
20 views
Aligning images of starfields
I have two images taken within 30 minutes of each other in the same part of the sky. They are very similar but are slightly offset due to the Earth's rotation and other factors.
I know: the X, Y ...
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24 views
Saturn's angular position with respect to major axis?
Would someone please help me by giving me Saturn's angular position with respect to its orbit's major axis when the Earth is at Vernal Equinox Or at Perihelion?
If not possible please mention some ...
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81 views
Mass loss rate of planetary nebulae
The “interacting wind” model of planetary nebulae is based on the idea that the white dwarf phase of stellar evolution is preceded by a red giant phase. A fast wind from the hot white dwarf overtakes ...
