# All Questions

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### Coordinate system for space

I am high school student, I have doubt if I have to locate a planet or any star in space, how do I locate it, because we have no perfect coordinate system, I have read in some books, that time is ...
48 views

### Calculating historical star maps from proper motion

I'm working on some software which needs to calculate the position of stars and galaxies visible to the naked eye at different periods of human history. The Yale Bright Star Catalogue gives the ...
55 views

### Why was Dawn's (the spacecraft) flight path circular?

In comparison to the twin Voyagers, Dawn's flight path circled the sun in an anti-clockwise manner. The map of its path shows its targets, Ceres and Vesta were in a trajectory that was close to a ...
3k views

### Which are stars and which are noise in this comet photo?

The Forbes news article NASA's Hubble Telescope Snaps Best Images Yet Of Our First Interstellar Comet shows the image below (which I have since annotated) of comet 2I/Borisov (C/2019 Q4) and links to ...
59 views

### Is intrastellar commonly used by astronomers to refer to objects within our solar system?

The CNET article Interstellar comet Borisov looks ordinary, making Oumuamua even weirder says: A paper published Monday in Nature Astronomy lays out the early data on Borisov, which is just the ...
45 views

How to plot Doppler profile corresponding to the spectral line? The spectral line was plotted from data: flux with respect to wavelenght and I know the temperature. These two function are Doppler ...
37 views

### Overhead (galactic North) view of the stars in and around the Vela Constellation with distance

I am working on a project and would like to have a star map--seen from "above" (Galactic North?) that calls out the stars in the Vela constellation and shows their distance from sol / earth. I ...
66 views

### Time dilation due to the expansion of the universe

This is not a homework question. I want some help in being able to clearly perceive the expansion of the universe and the consequences thereof. We know that the universe is expanding in an ...
58 views

### Seeing a star near zenith around sunset

I'm recalling while taking a university astronomy class the professor brought a few of us up to the observatory, around sunset. He showed us a star near zenith with the telescope. After we left the ...
39 views

### How to calculate the orbital velocity, the high-orbit (quasigeostationary) holding force and the shadow of the disk on Earth? [on hold]

[] The following data are given: • The circular orbit of the disk D (quasigeostationary orbit) parallel to the geostationary orbit. • Located 4,505 km to the north of the equatorial plane, above ...
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I am trying to perform wavelength calibration on an image but I am stuck by the identify task under the longslit package. So when I type :go on the command line after I set the parameters (see the ...
31 views

### How is Quantum Field Theory being applied in Astrophysics recently? [on hold]

I've recently taken up a project with my professor on quantising Real, Complex, Dirac and Maxwell's Field. We are currently planning to explore much deeper into Quantum Field theory and I was ...
57 views

### ra for sun vs stars

There is formula for stars sideral time: $$ra - \arccos(-\tan(dec)*\tan(lat)).$$ where $ra$ - is right of ascension at the vernal equinox. $lat$ = latitude $dec$ = declination Is it applicable ...
42 views

### Dark forces and galactic filaments

Could it be that dark energy = momentum of hydrogen in galactic filaments, and dark matter the mass of the galactic filaments?
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### Can fish and other sea creatures survive in watery planets like Neptune or any other planets that has water?

I'm a bit curious since Neptune does not have a land surface and it is covered with water, I mean water has oxygen right? What will happen if we put some sea creatures in these watery planets? Can ...
41 views

### Spectral Class Breakdown

Where can I get a more detailed breakdown of Spectral Classes. Wikipedia only has it at Letter level rather than sublevel. For example, https://en.wikipedia.org/wiki/Stellar_classification has B ...
74 views

### How was Cassini able to measure and use the Earth-Mars distance to get the Earth-Sun distance?

How was Cassini able to measure and use he distance between Earth and Mars to get the Earth-Sun distance? How were the ratios of Earth-Mars and Earth-Sun calculated then? Given Kepler's laws all we ...
67 views

### Is there a way to tell the difference between earth andesite from Mars

I'm curios if there is a way to test if this sample might be Martian andesite. What type of oxygen isotope (or other) test can be done to address this in some way? As background, any information ...
22 views

### How to calculate the radii of high orbits above the parallels of 45 and 80 degrees? [closed]

I asked this question in the ”Space Exploration” section but I didn't get an answer. I answer the question here: I am interested in calculating orbits above the parallels of 45 and 80 degrees. A ...
71 views

### How would a planet's gravity affect an object longer and wider than its equator? [on hold]

Imagine a flat object slightly wider than a planet's surface area whose mass is much lower than that of said planet. If it landed on this planet, would the curvature of gravity bend it, or possibly ...
61 views

### What is the history of the Milky Way's relationship with Andromeda?

From what I've read, the Milky Way will collide with Andromeda in about 4 - 5 billion years, and a billion or so years after that the two will merge and become a giant elliptical galaxy. What I'm ...
75 views

### How much damage would collision with a similar mass primordial black hole do to earth?

All this talk of Planet 9 perhaps being a primordial black hole (PBH) made me wonder how dangerous a PBH collision with earth would really be. Specifically, if earth collided with a PBH of 1 earth ...
47 views

### Estimating a star's radius, temperature, and luminosity based on its mass

(See updated figure and description below.) I've been trying to generate ballpark estimates for the radius, temperature and luminosity of stars in the main sequence based solely on their masses (...
36 views

### Find x,y,z velocity component of a star?

I am trying to find the initial x,y,z velocity components of the Epsilon Lyrae stars. How might I go about doing this? The radial velocities are available on Wikipedia, but I am not sure how to use ...
61 views

### Understanding The Fluctuations In The CMB Maps

If I'm understanding this correctly the fluctuations in CMB are a result of the "last scatter" of photons when electrons joined together with nuclei that before this formed plasma. CMB is among other ...
31 views

9k views

### Why is Mars cold?

The surface temperatures of Mars are about -87C to 5C, which is much colder than that of Earth's. If Mars has 95% carbon dioxide, which is a Greenhouse gas, why is the surface of Mars so cold? ...
100 views

### Given that Kepler's Third Law as stated on most websites doesn't include mass, how does it work for planets in other star systems? [duplicate]

Kepler's Third Law as stated on websites I found while searching for "how to convert between a planet's orbital period and semi major axis" is $P^2 = A^3$ where P is the orbital period in years and A ...
54 views

### Does it make more sense to upgrade our existing telescope or to buy a new one?

We're at a bit of a crossroads here, since we're faced with what appears to be a tough choice. We've got a Celestron 11" SCT tube with a Losmandy G11 equatorial mount, all bought in 1996. The mount ...
246 views

### Split telescope into two eyes

I am looking for an appendage to attach to the end of a telescope which splits the image into two eyes instead of one. Does such an appendage exist?
80 views

### Where can I find permissibly licensed database of stars and constellations?

I'm working on a game engine of sorts, and one thing I did for a previous game which was under the GPL was I had a night sky with the constellations visibly connected and I'd like to do that again. I ...
37 views

### Simulate earth, moon, sun constellation with dates

I would like to simulate the three object distance, specifically the distance of the moon to both, sun and earth for further investigation into tide prediction. What would be a good starting point ...
104 views

### Venus-Saturn conjunction in Sagittarius on Dec 11, 2019 - How often does this happen?

Venus and Saturn will be approximately two finger widths apart in the constellation Sagittarius on December 11, 2019. I was wondering: how often do Venus and Saturn come together in the sky like this? ...
39 views

### Reason for Orbital Reflector [closed]

We know that last year, space X rocket took orbital reflector with it into the space. But what might be the reason behind launching this weird object into the space? Does it do any work there?
2k views

### Who is Seyfert, and what is “the so-called Seyfert flare”?

The BBC's Milky Way's centre exploded 3.5 million years ago says: A cataclysmic energy flare ripped through our galaxy, the Milky Way, about 3.5 million years ago, a team of astronomers say. ...
47 views

### How to query a region on the sky when given only ecliptic coordinates?

I am new at using the Python packages astropy/astroquery and what I want to achieve is to use it to find stars that lay on the TESS continuous view zone (CVZ). I ...
52 views

### Difference between 3D real space and 3D redshift space?

With regards to cosmological simulations (e.g., N-body dark matter only simulations), I've seen people talk about the positions of objects (halos, galaxies) in the simulation in terms of 3D real space ...
131 views

### How do we know so many details about Big Bang, but we do not know if Universe is finite/infinite?

I understand that this question may be too vague, but I am confused about the following: On one hand we know a lot of "details" about Big Bang, like really precise details, evolution of universe, age ...
75 views

### Orbital speed is (vector) sum of tangential and normal speed?

Orbital speed definition in wiki does not state clearly - it is just tangential speed component or square root of squares of normal and tangential speed (full speed vector). When we say that moon ...
39 views

### Can we consider Indian Astrology as astronomy? [migrated]

Indian Astrology has mentioned about the basics of modern astrology. Apart from Varaha Samhita any other texts available on Indian Astrology/ Jyotish?
129 views

### A vertical stick's shadow at solar noon should be straight north/south, right?

At true solar noon, the subsolar point should be directly north or south of you, and therefore a vertical stick's shadow should point directly north or south, right? The Wikipedia page for Sun Path ...
69 views

### How is Earth's gravity modelled?

The Earth does not have a defined geometric shape. Then how do space scientists who want to put a satellite in orbit model the gravitational field of Earth? Do they assume a single object with minute ...
60 views

### What did i see go by saturn?

I was looking at saturn through a basic reflective telescope. I had it focused and could see the rings. To the left a small dim white dot came across my view passing in about 3 seconds from my north ...
61 views

### Where does Love's number come from in $\delta m = \frac{1}{2}k_2M_2\lbrace\frac{R_1}{r_\star}\rbrace^3$, the formula for the mass of a tidal bulge?

My question refers to page 165 of this paper. Specifically, how does one derive the equation $\delta m = \frac{1}{2}k_2M_2\lbrace\frac{R_1}{r_\star}\rbrace^3$ for the mass of a tidal bulge? A full ...
35 views

### How to calculate the moon phase angle?

I need to calculate the exact moon phase angle for each our of a day. I have my position in lat and long and a unix timestamp. At the end i would like to be able to caluculate the moon brightness with ...
40 views

I have an ASCII file (.con) with the coordinates of vertices of different contours. This file is obtained from Matlab. Now after every set of contour ends there needs to be a blank row in the contour ...
274 views
+100

### Characteristics of the first planets in the Universe?

What would have the very first planets looked like, based on their most likely chemical compositions? For example: Were they mostly grey gas giants with atmospheres of hydrogen and helium, ...
164 views

### How (the heck) does Astrometry.net work?

What magic is this? This answer to my question Astronomy detective question: what part of the sky are these photos of? What are a few of the stars? nails it, and the output (linked there) contains ...