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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What is the origin and nature of the “hydrogen envelope” located on the sun side of a comet coma?

It is tempting to assume the origin of the hydrogen is water vapor from the comet, in which case, what process "breaks up" the water molecule (or perhaps ammonia molecule?)? Is the hydrogen actually ...
3
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2answers
23 views

When a star turns into a red giant what stops its core contracting

I recently asked this question When do stars become red giants? and am now wondering when the star's core is contracting after it has fused H to He what force stops the contraction just before it ...
2
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1answer
38 views

How to measure the effects of the rotation around the Sun?

It is well know that we can measure the spinning of the Earth with a Foucault pendulum. But, is there a similar experiment for the rotation of the Earth around the Sun? I would like to know if we ...
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3answers
3k views

How to ‘correct’ reflected image on my telescope?

When viewed using my reflector telescope, the image, for example the moon, is flipped over and upside down (reflected). Therefore I need to do the ‘opposite’ movements when I want to align something. ...
3
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1answer
24 views

Correlation between large-scale galaxy structure and CMB fluctuations?

During a relatively non-technical astronomy seminar the other day, the speaker displayed the famous WMAP full-sky image as an aid to describing what the CMB is, the scale of its fluctuations, etc. ...
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1answer
31 views

Is there a simple formula for calculating semimajor axis bounds of “habitable zone”?

I understand that an accurate determination of the bounds of the "habitable zone" for a given stellar system depends on a large number of factors, including many beyond characteristics of the parent ...
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0answers
43 views

What is the shape of the Sun's orbit around the Milky Way? [on hold]

Here is a question for you really bright folks. How does the motion of the sun along the midpoint of the plane of the galaxy look like? I suspect it to travel above and then below the plane but I ...
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1answer
51 views

Our universe the surface of a 4-dimensional sphere?

The cosmic microwave background that we observe uniformly around us is usually explained by assuming that our universe is the surface of a four dimensional sphere. That way the uniformity makes sense ...
2
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1answer
123 views

Analyse astronomical data

Recently I was told of a job offer to analyse astronomical data. The job offer states that they want somebody with knowledge of astronomical data analysis software and it will be a plus somebody who ...
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6answers
4k views

Why is the solar noon time different every day?

If you check the local time for solar noon is different every day. Why is it so? Is it because Earth doesn't make a complete rotation in exactly 24 hours?
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1answer
271 views

Calculate the latitude / longitude coordinates of the location where the Sun is at the zenith

There are plenty of resources showing how to calculate zenith and azimuth of the Sun when the time and the location are given. However, I need to calculate the location where the sun is at the ...
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1answer
266 views

How is the Plane of the Solar System oriented to the Sun's motion through space?

How is the Plane of the Solar System oriented to the Sun's motion through space: parallel, perpendicular, or some other angle?
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2answers
74 views

Stellar Power(Luminosity) Flux

So I was applying some mathematical techniques I learned to physics, and one thing that captured my interest, is the power or luminosity flux of a star. So modeling the situation, taking the scalar ...
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3answers
4k views

Do all the individual stars that we can see in the night sky belong to Milky Way?

I was wondering if all the stars that we can see with the unaided eye as distinct point sources are from our own galaxy? In other words, can we see stars from the Andromeda Galaxy or other galaxies ...
2
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0answers
26 views

Precession period matching solar year

Consider the case of a tidally locked planet: its axis of rotation must be perpendicular to the plane of its revolution around the parent star. Therefore, no precession. It is possible for a planets ...
3
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1answer
58 views

Where can I find the list of the planetary motion equations?

The planetary motion equations are written in the ellipse equation format, i.e. $x^2/a + y^2/b = 1$. Can anyone please tell me where I can find the list of all the planetary motion equations, ...
2
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1answer
81 views

How is UT1 being computed?

I've recently read up about time standards and now understand that UTC is a second-corrected version of international atomic time so that it is kept within 0.9s from UT1. And then UT1 is defined as ...
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2answers
23 views

Do Pulsar Stars produce sound?

Can I hear electromagnetic radiation coming from a pulsar star? Or can I hear it if I stand outside it?
2
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1answer
351 views

Ephemeris calculations: Light time correction of the moon

I am currently trying to calculate apparent positions from raw JPL data. I've got it pretty much figured out, but there is one thing that's bugging me: Has the light time correction of the moon to be ...
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1answer
34 views

Planetary Systems

How does one know the correct position of planets in relation to the sun when viewing the solar system from different angles makes the appearance of the planets different? I would think that it would ...
2
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1answer
30 views

How to practically find the RA-DEC coordinates of a star?

How are RA-DEC (Right Ascension & Declination) coordinates of a star measured i.e. if scientist spot a new star in the sky how do they accurately measure it's coordinates?
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1answer
54 views

Is sun revolving around certain mass in space with reference to some other galaxy?

Every planet and satellite revolves around their mother planet and about their own axis as we know. So they are compacted as a system. Then why not sun?
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2answers
83 views

Does the Sun produce audible sound?

Theoretically if I were able to build some sort of device that let me sit 1 foot away from the surface of the Sun (or any star for that matter) without being vaporized, would a star produce any sort ...
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2answers
2k views

How could scientists know how far a star or galaxy is from us?

How do astronomers measure how far a star (or galaxy) is away from the earth? How would they know that it has taken 13 million years for light to travel in space before it reaches us?
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3answers
772 views

EM waves: How do they travel for billions of km without damping

If a star is 1 billion light years away, it means that the light we see from the star is emmitted billions of years ago. How does this light not undergo a frequency change or get damped inspite of ...
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2answers
3k views

How many stars are in the Milky Way galaxy, and how can we determine this?

I have heard multiple estimates on the quantity of stars within our galaxy, anything from 100 to 400 billion of them. The estimates seem to be increasing for the time being. What are the main methods ...
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0answers
37 views

How do we decode the image formed by a gravitational lens?

Using our own sun as a gravitational lens, we can scrutinise planetary surfaces in distant solar systems with a good deal of accuracy: ...
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1answer
24 views

Does the rate of expansion of the universe exceed the rate at which the local group is being pulled toward the Great Attractor?

I understand that the expansion rate of the universe driven dark energy exceeds the rate at which the local group is being pulled toward The Great Attractor (Hydra-Centaurus Supercluster). Does this ...
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1answer
792 views

Do all known planets and moons have magnetic field?

In this Wikipedia article it is stated, that magnetic field of Earth is caused by currents in her core. The same origin is for Jupiter magnetic field. For Moon (article) there is a magnetic field, ...
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1answer
28 views

Import of Celestial Effects on Satellite Radio Interference

Some internet (among other) infrastructure comprises satellites, which beam communications in radio frequencies. These satellites, to ground observers, appear as very small solid angles in the sky. ...
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3answers
153 views

Can a planet form before the parent star ignites?

I'm unable to find an answer to my questions via my searches. This questions pertains to the timeline of a star system creation. My question: During the creation of a star system, can satellite ...
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2answers
22 views

astronomy & light pollution

If you were staring to the sky in a big city and electricity is turned off in a big area around you, would you be seeing the sky with little light pollution instantly?
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2answers
172 views

What are the demographics of stars visible to the naked eye?

Of the stars that can be seen with the naked eye, what are the distributions of each type? For example, how many are main sequence? how many are Super Red giants/white dwarfs/neutron stars...etc. ...
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4answers
344 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 ...
0
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1answer
48 views

Sun's Right Ascension appears to be wrong in my Stellarium

The Stellarium version 0.12.4 I have shows the RA of the sun at 22.5 Hour while Google says it is 19h 4m 31s. I am confused. Please help.
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1answer
197 views

Calculate exact time of Solar midnight

I want to calculate real time of midnight (Solar midnight), but I am unable to find any formula or algorithm for that. I have times of sunrises and sunsets for every day of year. How can I get Solar ...
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2answers
1k views

Amateur moon laser ranging

Questions first, then my rough estimations: 1) Is it possible to perform moon laser ranging with amateur motorized 114mm telescope? My calculations suggest that for 1mJ laser it should receive ~2 ...
0
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1answer
112 views

Meade DS 114 Telestar mount

I'm having some problems with my Meade DS-114 telescope's Telestar mount. The motor works fine automatically rotating vertically, but horizontal rotation doesn't work at all on the mount. It just ...
15
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1answer
354 views

How fast is the Earth-Sun distance changing

This is inspired by Evidence that the Solar System is expanding like the Universe?, which referenced an article by G. A. Krasinsky and V. A. Brumberg, "Secular Increase of Astronomical Unit from ...
3
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1answer
97 views

Which BICEP2 r value should be compared to Planck's r<0.11?

The BICEP2 paper reports a tensor/scalar ratio $r = 0.20_{-0.05}^{+0.07}$, but then says: Subtracting the various dust models and re-deriving the r constraint still results in high significance of ...
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2answers
42 views

Data for binary systems

I am looking for binary systems data that can be used in the context of Kepler's laws. Masses, distances, periods, etc.
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2answers
122 views

Size of a photon

When detecting radio waves in space, we use very large telescopes or arrays of telescopes. But according to QM, aren't photons point particles when measured? Does a photon with a large wavelength ...
6
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3answers
810 views

How long was a day at the creation of earth?

Since the earth is slowing its rotation, and as far as I know, each day is 1 second longer every about 1.5 years, how long was an earth day near the formation of earth (4.5 billion years ago)? I ...
3
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1answer
17 views

Could asteroseismology have a significant potential to unravel the mechanisms of solar cycles that last thousands of years?

Could asteroseismology have a significant potential to unravel the mechanisms of solar cycles that last thousands of years? And what about solar cycles 1 billion years ago and 2 billion years ago ...
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0answers
40 views

Radial and tangential velocities of a star

(source) Early in this piece it states that the radial and tangential velocities are: $$V_r = V_c \cos(\alpha) -V_{c,0} \sin (l)$$ $$V_t = V_c \sin(\alpha) -V_{c,0} \cos (l)$$ but I am struggling ...
5
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4answers
678 views

Optical explanation of images of stars?

Very often when viewing pictures of the cosmos taken by telescopes, one can observe that larger/brighter stars do not appear precisely as points/circles on the image. Indeed, the brighter the light ...
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0answers
26 views

How is the formula derived for finding the field of view given drift time and declination of a star?

How is the formula for field of view derived given the drift time of a star and its declination? $FOV = (drift\ time \cdot \cos(declination)\cdot360 ) / 86164$
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0answers
13 views

Velocity dispersion of galaxies

I couldn't find on web how can I get the velocity dispersion and velocity maps of galaxies from the 3D data cube I get from integral field spectrograph.
2
votes
1answer
115 views

Why do galaxies “dissappear?”

So, this is a dumb question but a bit of information confused me lately. Before, I figured galaxies were no longer visible by us because their luminosity decreased in an inverse square manner. ...
8
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2answers
293 views

Silicon-based life [closed]

My question may not be suitable here, because it's more of astrobiology. Life as we know it is carbon based. Is life based on silicon possible? What would the conditions for habitability for ...