# All Questions

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43 views

### Refinement to sun/wristwatch estimate of N/S direction

As discussed in a 2015 question here and shown in a 2013 illustration in Primer Magazine, it's possible to estimate the north/south direction on the ground using a correlation between the hour hand of ...
15 views

### Is the pulsar map on the Pioneer/Voyager probes only meaningful for earthlings?

The Pioneer probes brought plaques (and later the Voyagers two golden discs) with a "pulsar map" imprinted on them. The purpose of the map is to make the position of the Sun clear for an ...
5k views

### Circular orbits

First of all, I'm studying orbits for a hobby: world building. Unfortunately, my mathematical abilities approach a ridiculous low threshold, which means I am stuck with reading the simplest ...
15 views

### TASCO 49060700 60x700mm Spacestation Refractor

So, my grandfather so graciously gave me his TASCO 49060700 60x700mm Spacestation Refractor Telescope, which is extremely wondrous. Any way, I found this answer to my 3x barlow lens, which I believe ...
5 views

### Can massive stars end up as post-AGB?

Recently I've found that some post-AGB objects are spectrally classified as hot luminous stars. For example, in the Toruń catalog of post-AGB objects, the star LSE 63 is listed as both a post-AGB and ...
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### Gift for 16 year old Aspiring astrophysicist,,,,

I'm an outsider here, so please bear with me. I have a 16-year-old nephew interested in the field of astrophysics and am looking for a birthday gift. I had thought about a book on astronomy, but don'...
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### Question on the singularity theorem

I have just started studying Cosmology and we have been asked to prove that in an expanding FRW Universe which obeys the strong energy condition: $$\rho + 3P >0$$ Then there must exist a Big Bang ...
2k views

### What if the two Black Holes spiraling around each other are evaporating via their Hawking radiation?

A non-technical explanation In a Gravitational Wave event, the point is that in this event when Black Holes are spiraling around each other, they will cause the very fabric of Space-time to ripple and ...
9 views

### SDSS - getting separate u, g, r, i, z frames from SWARP tool and astropy

I am following this paper to extract the u,g,r,i,z image frames from the SDSS image fits files. I have the fits files downloaded (using the bulk data download option from SDSS) and tried to run the ...
36 views

### What is preventing cave formation on Mercury?

The answer to this question suggested cave formation on other planets in the solar system especially on terrestrial planets. There are suspected lava tubes on Mars, Venus and Moon where lava flows ...
128 views

### Why does east and west appear to be mirrored in the celestial sphere?

I'm wondering why East is left and West on the right of the celestial sphere if you look at images of it? Example below: (source)
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### How to calculate the point on the globe with maximum magnitude with given Besselian elements and given time for a partial solar eclipse?

I am currently working on improvement of an Android app that calculates solar eclipses. For many days now I have not been able to solve a mathematical problem concerning solar eclipses, so I decided ...
119 views

### Caves traced in nine planets of solar system

Are there chances of caves being found or traced on other planets of the solar system? What's the solution? Manufacturing special telescopes for viewing or observing caves on other planets? or ...
802 views

### Can lightning occur in stars like the Sun?

In the Wikipedia article about lightining, the following explanation is given about the electrification process in clouds: The details of the charging process are still being studied by scientists, ...
48 views

### How is the height of the Great Red Spot measured?

This answer states that the Great Red Spot is getting taller. This means that we are able the determine the spot's height. How do we do this?
8k views

### Why did the big bang not just produce a big black hole?

Questions I've often wondered about: If all the matter and energy were concentrated at a single point at the big bang, why wasn't that a black hole, or why didn't it form one? If the reason #1 above ...
51 views

### What shape do satellites trace as they wobble in orbit around another body?

What shape does the center of gravity of a satellite trace in 3-d space as it wobbles in orbit around another body? How is this shape modeled geometrically? Is it a topological torus? Is it feasible/...
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### Strange Sighting, Help Needed! [closed]

I live in Hyderabad. Around a week ago, I, with my mother went to observe the planets from my roof I had observed Jupiter and Saturn till they went down below the horizon and then I was ready to move ...
55 views

### Why does the Simbad page “A.A. Michelson's Jovian Galilean-satellite interferometer” show data for Betelgeuse?

When searching for things related to How did Michelson measure the diameters of jupiter's moons using optical interferometry? I came across the ui.adsabs.harvard.edu entry A. A. Michelson's Jovian ...
306 views

### Is gravitational lensing a good way to search for negative mass?

Is it possible to verify negative mass with gravitational lensing? The following video proposes an idea that galaxies are surrounded by negative mass: https://youtu.be/MZtS7cBMIc4 Could this be ...
26 views

### Updrafts on Gas Giants

Gas giants put out a fair amount of heat from gravitational collapse, so there's bound to be quite a bit of upward moving winds. If Carl Sagan's idea about aerial ecologies pans out, could larger ...
2k views

### Solar Analemma - but with a star instead

We (homeschool students and I) are trying to find the answer to this question. Does a star also create Solar Analemma figure 8 when photographed daily for a year? Has anyone published an experiment ...
31 views

### How to calculate geocentric transformation to heliocentric coordinates?

I have Sun data (lon+lat+distance) in geocentric coordinates: but I want to visualize in heliocentric way. How to calculate that?
34 views

### How bright would a magically created 13.7B years ago white dwarf be now?

I assumed that the initial brightness is $1$, and at death it is $10^{-20}$ (since I can't reach 0 with exponentiation, it will be close enough to 0), and it lived $10^{15}$ years. Then I solved an ...
969 views

### Black Hole Collision & Gravitational Waves

The Gravitational waves detected by LIGO on 14th September 2015 are attributed to a collision of two black holes, which had been rotating near the speed of light around each other just before the ...
3k views

### Does a planet's mass or gravity affect the height of it's mountains?

According to this Wikipedia page, the top five highest mountains on Mars (and the highest on Venus) are all taller than Mount Everest (and Mauna Kea as measured from the ocean floor). Does a planet's ...
120 views
+200

### What inaccuracies are in this Stellarium depiction of the sky?

I found this depiction on Stellarium of the sky as seen from near the Apollo 12 landing site on January 11, 2131. The earth is the black circle in the arm of the Milky Way. Here is a similar view ...
154 views

### Why is the great red spot shrinking?

The Great Red Spot is an anticyclonic storm on Jupiter that is bigger than the Earth. Based on the Wikipedia article, it has been shrinking in size for the last 400 years, going from 41 to 16 thousand ...
86 views

### Can a pulsar also be a magnetar?

I know this is a simplistic question, but I cannot find a straight answer... Also, is it possible most or all neutron stars are magnetars and/or pulsars? It's just hard to see all of their properties ...
57 views

### Luminosity of Neowise

So, I have been trying to figure out the bolometric luminosity of the comet C/2020 F3 (Neowise) on the 22nd of June, 2020. At that time, Neowise was $1.4$ AU away from Earth and had an apparent ...
28 views

### Photographing Mars, Jupiter and Saturn

I want to take pictures of planets, well at least Mars, Jupiter and Saturn with some surface details. I have a Canon EOS 7D Mark-II and a Tameron 150 - 600mm lens (very heavy), a 1.7X extender, and a.....
37 views

### Does lightning on Venus affect the chemical composition of the clouds?

It is established that lightning occurs on Venus due to the presence of sulfuric acid clouds. Does this constant electric discharges and possible electrolysis affects the composition of the clouds on ...
8k views

11k views

### Gallery of 'actual images' from space?

Where can a gallery of actual unaltered photographic images taken in (or of) space be found? Specifically ones that are untouched, not colorized (not necessarily black and white, but they usually are),...
101 views

### Do brown dwarfs have stripes?

Brown dwarfs (BD) are often depicted with stripes. brown dwarf Jupiter Pictures of BD resemble Jupiter but brown dwarfs ...
55 views

### Strange lights moving North [duplicate]

My fiancé and I took our youngest sons out to sky watch at the river near by. The older of the 2 was looking up and said - "look it's Santa's reindeers!" All of us looked up and saw a ...
31 views

### Why did the CM & LM have to be separated at Apollo launch? [closed]

I've just read a bit about Apollo 13, and 1 question that kept popping up in my mind when they talked about the docking between the Command module & the Lunar one is that why did they have to be ...
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### How to plot celestial equator in galactic coordinates? Why does my plot appear “backwards”? [duplicate]

I'm trying to plot celestial equator in galactic coordinates. Here is my code (based on this answer): ...
538 views

### Can someone in a deep well see the stars in daytime?

I am wondering whether it is possible for a guy in a deep well to see the stars in the daytime. Now the background is dark. So might the stars be visible?
105 views

### Why Trojans haven't merged into moons

Jupiter's trojans are located in the L4 and L5 Lagrange points. These two points are stable, so why don't all the trojans have already merged into small moons? And since it's not the case, what ...
49 views

### Light brightened dimmed disappeared reappeared

My son and I saw an unusual light sit in one spot for 15-20 minutes as it got very bright and dimmed, got bright, disappeared and reappeared repeatedly. It then slowly moved north-west then finally ...
17k views

### Why do the planets orbit in the same direction?

Theoretically, planets would have an approximately equal chance of going one way in their orbit or another but in reality, this is not the case (at least in our solar system). Why is this?
403 views

### If any object could become a black hole, could any object become a neutron star?

A black hole doesn't necessarily need to form from a star; theoretically, it could form from any extremely dense object. In fact, many astronomers differentiate certain black holes, like supermassive ...
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### What complementary observation campaigns have looked at Kepler's field of view?

It seems to be common practice to double up observations. For example, shortly before New Horizons flew by Pluto, several of its moons were discovered by telescopes as a concerted effort was put in ...
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+50

### How do you know that the remnants of the explosion of a Star are of a Hypernova?

Some Background? There are many types of Supernovae that can be classified into the following categories :- (This list is available here.) Type 1A supernovae • Their spectra show very little hydrogen ...
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### Could Earth be the only and last planet with life? [closed]

The other day I had a dream...I don't remember anything about it but I woke up with almost a crystal clear realization/moment of clarity: The reason why we can't find alien life and all other planets ...