All Questions

1
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1answer
10 views

Dynamical modelling of galaxies with counter-rotating components using the Schwarzschild method

I am currently trying to understand dynamical modelling using Schwarzschild's method. I have been doing some reading the past days, but I suspect that I am getting something really wrong. According to ...
3
votes
3answers
419 views

Why things float in space, though there is always gravity of our star is present

In the solar system, things float around. We are so certain that the gravity of our sun exists. Still, why does that gravity not influence satellites and other objects there. Our solar system is also ...
1
vote
1answer
42 views

How to find the source of the light

There are millions of galaxies out there in the entire universe. When a telescope is set to a direction to to identify the stellar objects, it can capture all lights from all the objects. How do we ...
12
votes
6answers
1k views

How “fast” do astronomical events occur?

I've seen quite a few news about astronomy but I'm not deep into knowing how it works or how people observe it. It got me thinking: if I want to watch a supernova for example, how long will I have to ...
5
votes
3answers
1k views

Can we find rocks from Venus or Mercury on Earth?

As we know, we can find rocks from Mars on Earth, how about Venus and Mercury? Is that not found yet? Or it is impossible to find them because they are closer to the Sun, and debris won't go far away ...
1
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2answers
333 views

Why do most meteors vanish just before hitting the ground?

Many times we see in the sky that most of the meteor shower trails vanish when they are about to strike the earth several feet above the ground. Why does this happen? They could strike the earth's ...
-5
votes
2answers
71 views

The Expansion Of The Universe [on hold]

I am informed that a volume of nothingness can expand many times over for no good reason,becoming filled as it does so by colossal numbers of virtual particles which appear ultra-briefly out of ...
-1
votes
0answers
57 views

Why do heavy objects bend space-time downwards? [on hold]

Einstein's general theory of relativity is famously demonstrated using stretched sheet and marbles. We all know the demonstration. But its GRAVITY itself which makes the stretching of the sheet ...
0
votes
2answers
392 views

How was the distance from the Earth to the Sun determined

How was the Earth to sun distance measured. How do we know how far from the Earth the Sun actually is.
1
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2answers
61 views

How to calculate solar coordinates. (Right Ascension, Declination, and ultimately the Altitude and Azimuth of the Sun)

As the title says I am trying to calculate solar coordinates of the sun for a given location and time. I have spent many 10's of hours on this without success so I will sincerely appreciate help on ...
5
votes
1answer
235 views

Collision with Andromeda Galaxy

According to Hubble's law, the universe is expanding and this expansion is proportional to distance between the two objects and thus objects are moving away at a very fast rate, then why is it ...
12
votes
2answers
282 views

What are some theories that explain the 11 year solar cycle?

The Sun exhibits a periodic cycle for solar activity as manifested by solar activity (e.g. sunspots, solar flares). This activity is related to magnetic fields which emerge from the interior of the ...
2
votes
1answer
52 views

If the space is expanding near the speed of light or the speed of light, why Andromeda is approaching or coming near to our galaxy (Milky way)? [duplicate]

Space with distance of 1megaparsec is expanding with rate of 70km/s, and if space with a distance of 4296 megaparsec is expanding at rate of 300,720km/s, then why Andromeda is coming to us? Even there ...
-1
votes
0answers
57 views

Black holes in galactic rotation [on hold]

I'm wondering whether the total mass of a galaxy's hypothetical black holes, that may have each been formed within the gravitational horizons of larger black holes (that are indirectly apparent, ...
3
votes
3answers
236 views

Is it possible to know if you are travelling close to the speed of light if you have nothing to compare your speed with?

This is a question that has been bugging me for some time. Let's see if I am able to make me understood! Imagine you are travelling in a spaceship at 99.9999999999% the speed of light and you are ...
3
votes
1answer
71 views

Is there an optimum orbit for a hipparcos/GAIA-like parallax observatory

The GAIA spacecraft is currently mapping the stars in the Milky Way by parallax. It orbits in the Earth-Sun L2 lagrange point. The parallax observed from the spacecraft orbiting around the sun allows ...
1
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0answers
21 views

If space is negative energy and matter is positive energy then does that mean the universe is finite?

I was reading a book by Stephen Hawking, it was written that universe is made up of 2 ingredients,i.e., space and energy and space was the negative energy, so they add up to 0. But since space is ...
0
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0answers
83 views

Stars readjusting themselves in the sky [duplicate]

I had a meeting in the evening and thought of grabbing a snack before that. I stepped out of the office along with a colleague. He was on his phone and I was simply staring at the sky wishing it would ...
1
vote
2answers
113 views

How do we know the radius of the universe is 47 billion light years?

Hubble deep field image at maximum resolution shows a few of the furthest galaxies very small & faint, only just visible, but suggests that there is more to see beyond if only the resolution were ...
0
votes
1answer
45 views

Computing the local orbital frame vector directions in a geocentric reference frame

In the context of the study of a cubesat (little satellite), I am asked to define the local orbital frame and compute the local orbital frame vector directions as a function of time : Here the ...
6
votes
1answer
805 views

How do CMB photons 'gain energy when they pass through normal regions of space with matter' and 'lose energy when they pass through voids'?

The Space.com article Huge Hole Found in the Universe says: The gargantuan hole was found by examining observations made using the Very Large Array (VLA) radio telescope, funded by the National ...
0
votes
3answers
150 views

Struggling to understand the phases of the moon

Source Typically this diagram is how the phases of the moon are explained but the issue is this, namely, the phases seen on the right half are not possible. All the phases should appear on the left ...
12
votes
2answers
431 views

The battle over Gliese 581 and Gliese 667C?

In 2014, Robertson et al. made a case that stellar activity is masquerading as planets (here and here) for these well-known systems. In both cases, they claim that the only real planets discovered so ...
0
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0answers
43 views

Black hole properties [duplicate]

Black holes are things with immense gravity.Inside black holes gravity is much stronger than any other fundamental forces.But is strong enough to overcome Pauli repulsion?
21
votes
4answers
10k views

Why can't we feel the Earth's revolution?

I googled it and checked a few Q&A and there's only things about "Earth's rotation". But why can't we feel the revolution? They say we can't feel the rotation because the Earth spins at a ...
13
votes
8answers
6k views

Determine the moons of Jupiter through a telescope

I was doing my own "space exploration" last night with a telescope. Being a space noob I can't visually determine stars or planets (I know the moon, though), but I focused on one particularly bright ...
1
vote
1answer
40 views

Exposure time for spectroscopy compared to photometry

For a report I'm writing, I'm interested in comparing the exposure time required for spectroscopy versus photometry for a given magnitude. I found the figures on pages 7 and 8 of this lecture ...
1
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1answer
103 views

What Is The Maximum Distance Our Finest Instruments Could See When They're Perfected?

Radius of the observable universe is 47.5 billion light years,which means we are seeing things which are about 48 billion light years away. At a rough estimate,at what distance would our finest ...
4
votes
0answers
33 views

Does the density in the core of a “higher mass” star stay generally constant while it evolves on the MS?

We know the CNO cycle produces the majority of energy production in a "higher mass star" of approx. over 2 solar masses and the core is convective due to the large temperature gradient. My professor ...
-1
votes
2answers
139 views

What does it mean for space to expand?

In this YT video Michelle Thaller says The Big Bang wasn’t an explosion but an expansion and as such there's no empty center where the explosion would've been. To explain expansion she uses the ...
1
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0answers
37 views

Hypothetical: Is the interstellar wormhole too close to the black hole? [on hold]

Most reasonings about hypothetical wormholes say, that you need an extreme amount of energy to keep them open. Given that, isn’t the worm hole too close to the black hole gargantua? The gravity ...
4
votes
3answers
133 views

What would you find within a void?

I'm aware that voids are relatively empty regions of the universe, but just how empty can they be? Wikipedia states that voids have 'few or no' galaxies, but I can't find much else. To make my ...
6
votes
3answers
3k views

Less stars in the night, compared to 15-20 years back

I am not sure if my question is true or not. But this is what I observe regularly. When I was young and when I look at the sky, there were too many many stars were there. But now, from few months I'm ...
1
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0answers
33 views

Causes of emission of accretion disk

As far as I can see, there are two main sources for the emission of energy from an accretion disk: release of gravitational potential energy of the infalling matter; friction from differential ...
2
votes
1answer
44 views

How can the oblateness of Earth impart torque to change the longitude of ascending node of a satellite?

I've read that you can change the longitude of ascending node of a satellite (i.e. changing the orbital plane without changing the inclination) to change its orbital plane by using the torque imparted ...
7
votes
1answer
1k views

Why didn't all the iron and heavier elements find their way to the center of the accretion disc in the early solar system?

I guess that's pretty much it. I just heard that that a meteor fragment was found to be solid iron and it just seems inexplicable that it was floating around.
1
vote
1answer
36 views

Plotting Galactic Longitude from 180 to -180

I made a scatter plot in Python that looks like this: However, I want galactic longitude, l, to be plotted from 180 to -180 like these graphs from Iorio and Belokurov (2019): Here is the ...
9
votes
1answer
1k views

How far into intergalactic space would you have to go to see the Milky Way?

If in the distant future a ship were somehow able to move beyond the galaxy and into intergalactic space, how far would it have to go before we could look out a window and see the Milky Way in its ...
3
votes
2answers
54 views

Draw the celestial sphere for latitude, showing the star Sirius, Estimate the approximate date when Sirius rises with the Sun

I'm having trouble understanding how to solve a certain problem. The problem is from the book Astronomy: Principles and Practice by Roy and Clarke. It is actually a solved example, but I am unable to ...
6
votes
2answers
159 views

What's the actual speed of electromagnetic radiation in space?

The speed of EM radiation is very slightly less than $c$, because space is not quite a vacuum. Say EM travels at $(1-\varepsilon)c$. For example, this results in a slight delay between receiving a ...
-6
votes
0answers
66 views

why do we keep using the term tidal locked? [closed]

So many astronomical terms are being used incorrectly. Tidal locked is not when a celestial body rotates at the same rate as the body it is tied to, only showing one side. If a celestial body has no ...
6
votes
1answer
63 views

Are any bow shocks seen in the visible spectrum?

Are any of the images of bow shocks created from visible light, or are they all from infrared light? While I'm including two of the better known images, my question is about any known bow shock. LL ...
2
votes
2answers
115 views

Using emission lines to determine redshift of a quasar

I am attempting this past paper question and am not sure how to tackle this, this is not homework! :) The spectrum of a distant quasar shows two broad emission lines with observed wavelengths of ...
11
votes
1answer
834 views

Recording Spectral Lines at Home

I was wondering if it would be possible to record the emission/absorption spectra of stars without expensive spectroscopy equipment. Would it be possible to somehow utilize diffraction grating? I own ...
2
votes
2answers
339 views

Quasar Redshifts

How can the gravitational redshift of a very distant quasar be distinguished from its cosmological redshift? Quasars are very massive objects,thought to be supermassive black holes,so therefore must ...
2
votes
1answer
69 views

Custom telescope

I am currently trying to make a Keplerian telescope from "scratch" with plano-convex lenses bought online. I have found my objective and eyepiece lenses. I'm just not sure if they will suffice to ...
2
votes
5answers
147 views

If fusion only happens near the center of the sun, what's with all the “fire” on the surface?

I understand that it isn't "fire" in the combustion of oxygen sense, but I can't find an answer online about what we're witnessing happening at the visible surface of the sun if all actual fusion ...
1
vote
1answer
62 views

Converting an RGB image to fits (astropy)

I am trying to save a NumPy RGB array (a 3d array with dimension 512x512x3), to a .fits file using astropy.io. Saving this array to a .png file works fine, but when ...
3
votes
1answer
58 views

Sorting out Julian Day, Julian Date, Julian Day number, Julian Day Calendar, and Julian Day Table

In this answer I mention day number which is 1 on the first day of each calendar year (January 1) and increments to 365 or 366 on December 31 of that year. There was an edit proposed, which included ...
-3
votes
1answer
75 views

In what form was dark energy stored 6 billion years ago?

Bearing in mind the provisions of the 1st Law of Thermodynamics, which decrees that energy can neither be created nor destroyed, all the energy in the Universe must have been there at the time of the ...

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