# All Questions

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### What did Hawking mean when he said “things can get out of a black hole”?

I was wondering about this quote I read the other day, by Stephen Hawking: "Black holes ain’t as black as they are painted. They are not the eternal prisons they were once thought. Things can ...
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### Axial tilt of exoplanets

Some directly imaged exoplanets have had their rotation measured but has the axial tilt of any exoplanet been measured? If not, when might we get the first measurement of axial tilt of an exoplanet?
30 views

### When will 2002 MS4 be named?

The trans-Neptunian planetoid 2002 MS4 is currently the largest known unnamed Sun-orbiting object. Is there any standard schedule on when this and similar objects might be named? Usually the ...
25 views

### Jupiter's effect on a hypothetical “warm” Europa's water

Imagine for a moment that Europa is not frozen solid (at least on the surface). Would the fact that it is tidally locked to Jupiter mean that the water would be stagnate? So there would be no tides ...
27 views

### Can the other side of the observable universe be seen as a black hole?

When looking at the objects near the horizon of the observable universe, the objects seem to emit radiation that is red-shifted. Time seems to advance at a slower rate than our own and at the horizon ...
83 views

### Order of shells formed in a massive star

In addition to the question with the picture here, why do shells don't form the same order as the alpha process? image credit: Gemini Observatory/NSF/C.Aspin
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### Do elements like magnesium and sulfur form an layer on massive stars?

For an evolved massive star, elements such as hydrogen, helium, carbon, oxygen, magnesium, ..., iron are involved, but from the picture below, there doesn't seem to have a layer of magnesium fusion ...
45 views

### Is Pluto's orbit more stable than Mercury's?

Mercury is believed to eventually possibly either collide with Venus or fall into the Sun. Pluto's resonant orbit with Neptune on the other hand seems more stable. Why isn't Mercury considered a "...
255 views

### At high temperatures, do planets glow like blackbodies?

I've been messing around in Universe Sandbox for a while and noticed that as a planet heats up, it glows like a blackbody starting at ~4000 K. Is the simulation here accurate, or do very hot planets ...
31 views

### How do the stars in the near-infrared (NIR) radiate?

Let's say we are studying the integrated near-infrared (NIR) light of a distant spiral galaxy. We would expect most of this light to be dominated by red giants stars and dwarfs. I assumed these stars ...
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### FLWR and curvature

The FLWR metric or model I believe results from Einstein's equations of general relativity if it is assumed the universe is 1. homogeneous and 2. able to expand (or contract). Solutions can have ...
968 views

### Can a small blackhole orbit a large star

I recently read about the discovery of a tiny black hole ( with only 3 times the mass of the sun ) nicknamed ‘The unicorn’ about 1500 light-years from earth. This got me thinking, can this blackhole ...
38 views

### Which version of Stellarium made you fly from one moon to another?

I recall a version of Stellarium (it was the very first time I had Stellarium) many years ago that made you fly between moons of the same system if you changed celestial bodies. E.g. if you were on ...
74 views

### How can there only be “11 phonons” in the mirrors of LIGO interferometers?

LIGO is an incredibly sensitive detector of small changes in space due to the passing of gravitational waves and uses some very high-level mathematics and physics and experimental techniques to drive ...
139 views

### Will we ever be able to see the surface of exoplanets directly?

When exoplanets are depicted, artist's impressions are used. The presence of exoplanets is observed by a dip in the emitted power of a star when a planet moves between us and the star (a kind of star ...
59 views

### What is the rate of change by day for a given right ascension?

I am writing a small Julia app to get my feet wet in that language. And I want to calculate "what's up tonight" based on a table of right ascension (RA)/Dec(lination) (table of stars), a ...
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### Role of power laws in astronomy?

I often see astronomers fitting data to power laws. What about power laws makes them so useful in astronomy? Why are so many astronomical observations well-fit by power laws? I know it's a relation ...
470 views

### How do astronomers calculate the period about the wave motion of the solar system in the Milky Way?

According to research, excluding the motion of the entire galaxy, astronomers found the motion of the solar system in the Milky Way. The solar system revolve around the galactic bulge of the Milky ...
64 views

### Aren't denser bodies more likely to collapse into hydrostatic equilibrium?

It is said that at small sizes, icy planets are more likely to be in hydrostatic equilibrium than terrestrial rocky ones. But why, as a matter of fact? Shouldn't denser bodies be more likely to ...
53 views

### How did the measured diameter of Ceres evolve over time?

Based on the Wikipedia page of Ceres, Herschel measured a diameter of 260 kilometers for Ceres, and Schröter measured 2613 kilometers. I do remember seeing at least a half-dozen estimates of the ...
55 views

### Does the ecliptic plane change relative to the galactic plane?

The equatorial plane moves over time with respect to the plane of the ecliptic (that's precession!). The ecliptic is at an angle with the galactic plane, but does this angle change over time? Does the ...
78 views

### Does Soter take into account Pluto's and Orcus' masses when determining Neptune's planetary discriminant µ?

Does Steven Soter's planetary discriminant µ1 for Neptune take into account the masses of Pluto, Orcus and other Kuiper belt objects crossing or coming very close to Neptune's orbit? If so, Neptune ...
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### Chaotic movement of Hydra and Nix

Hydra and Nix, two of the moons of Pluto, show chaotic movement due to the shifting gravitational field. How does knowing more about they chaotic behaviour help us advance in space exploration? ...
100 views

### Star brightness data to study exoplanets with the transit method?

Can someone tell me how I can find the star brightness data to study exoplanet using transit method? The file should be in comma separated value (CSV) format or any other formats that can be latter ...
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### Comoving Volume Calculation

Suppose I have data from an astronomical survey at redshifts in the range $z = [2,3]$. Suppose that, on average in this range, the data covers an area on the sky of $A=1$ $\mathrm{Mpc}^2$. How would I ...
32 views

### How did pressure evolve in the (early) universe?

I am trying to derive how the cosmological pressure $p(t)$ evolved over time in the universe, especially in the radiation and matter dominated epochs. There are some very nice explanations how $H(t)$ ...
50 views

### Question Anatomy growth phases [closed]

Need help with this what do you understand by the following Stationary phase isometric Allometric growth
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### Venera 13/14 Design specifications [migrated]

Does anyone know where I could find design specifications, plan sets, or other documentation for the Venera 13 or Venera 14 spacecraft? These are Russian spacecrafts from the 1980s. I suppose if ...
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### Is the transition between ice giants and Jupiter-like gas giants somewhat fluid?

The ice giants Uranus and Neptune are often being distinguished from Saturn and Jupiter who consist mostly of hydrogen and helium, while the ice giants have more of heavier elements than hydrogen and ...
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### Best Books on Spherical Astronomy

I am preparing for an astronomy olympiad and a good amount of questions in the olympiad come from Spherical astronomy, some of the books ive tried reading were too hard to understand as this topic ...
111 views

### Why is the Milky Way called like that? [closed]

From which language is the term milky way is derived and what is the largest star located in it?
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### Is it safe to look at an annular eclipse during sunrise using a medium

will looking at annular eclipse reflection through a bowl of water damage your sight? i already tried viewing it reflection through a bowl of water.
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### Why is the globe/compass symbol used more often than the globus cruciger for Earth? [closed]

Why is that symbol 🜨 used more often (or almost always) when portraying e.g. Earth mass or Earth radii than the globus cruciger ♁ ? From my point of view the globus cruciger fits much better as ...
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### Why does the solar analemma have a strange shape on Jupiter?

I'm trying to look at what the solar analemma looks like from different planets, using Stellarium. To plot the analemma, I go into the ephemeris tab of the astronomical calculations window. From there,...
67 views

### What is Newton's equation for gravitational repulsion? [closed]

If we consider that there is negative mass in the sense of repulsive gravity, will Newton's equation change only the vector
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### What would shadows look like on a planet with two suns?

On planet Tatooine which has two (main-sequence I guess) suns people still have one shadow only. Tatooine's suns seem quite close to each other, so it may actually be the case that the two shadows are ...
68 views

### Would it be a good idea to dockerize softwares in order to conduct hands-on tutorial sessions? [closed]

I am going to organize a tutorial in which I intend to train students on semi numerical simulations for reionization. Is it a good idea to supply use Docker to supply the codes? What do you think ...
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### Lightest object so far to function as gravitational lense?

Many amazing discovers are based on gravitational lensing and microlensing, but as non-expert it is not obvious to me: What is the (current) lower mass limit of the lensing object(s) for which ...
70 views

### Is the mass of antimatter negative or positive? [closed]

Is the mass of antimatter negative or positive For example, the mass of the electron 9.1×10^(-31), does this mean that the mass of the positron -9.1×10^(-31)?
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### Angular power spectrum - Could there be a version of matter contrast instead of temperature contrast?

I take over another post that is going to be deleted since I have none answer. Summary: $\quad$ I would like to go deeper in the relationship between Matter power spectrum and Angular power spectrum. ...
28 views

### Young galaxies VS. old galaxies spectra differences

What are the main (UV/optical) spectral differences between a young star-forming galaxy and an old galaxy with no ongoing star formation?
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### Looking for analytical expression of Cosmic Variance - Poisson distribution?

I have an expression of Matter Angular power spectrum which can be computed numerically by a simple rectangular integration method (see below). I make appear in this expression the spectroscopic ...
87 views

### Question regards to Kirchhoff’s Laws (of spectroscopy)

In the book "Horizons: exploring the universe-Cengage learning (2018)", page 210, it states that: Observational evidence can tell you how nova explosions occur. As the explosion begins, ...
4k views

### How are constellations intact if the stars are rotating around galactic nuclei?

From what I understood, the Milky Way (or stars in the Milky Way) doesn't rotate like a collection of points in a disc due to the presence of some invisible matter. In theory, the angular velocities ...
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### How much Dark Matter and Energy is needed for star birth and controlled nuclear fusion? [closed]

stars are born in a large scale cloud where matter and dark energy has a direct effect on star birth and controlled fusion. https://thumbs.gfycat.com/GoodnaturedWellgroomedInchworm-mobile.mp4 dark ...
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### Why aren't Russell Alan Hulse and Joseph Hooton Taylor credited as the discoverers of gravitational waves in 1974? [closed]

Why weren't Russell Alan Hulse and Joseph Hooton Taylor credited as the discoverers of gravitational waves in 1974? Currently LIGO is credited as the first discovery of Gravitational Waves, 40 after ...
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Is there a multiplication of relative velocities and if not, can you derive the equation for multiplying the relative velocities from the equation for adding the relative velocities
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Some Hot Jupiters have retrograde orbits. What causes this? Are there any other common factors amongst the planets with these orbits and have any other types of exoplanet been found with retrograde ...
I considered the motion of an asteroid around the sun, in a $2:1$ orbital resonance with Jupiter. Following the study of this resonance, it was observed that the angle between the major axis of the ...