# All Questions

7,530 questions
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### Are all satellites thought to be the result of collisions with the planets?

The leading hypothesis for how the Moon was formed was that another object collided with the Earth, throwing off a large lump of matter which formed into the moon. Is this thought to be the case with ...
50 views

### Can Eight Retrograde (seen from Earth) planets occur?

First of all, for the purposes of this question Pluto is a planet. So the eight planets being considered are Mercury, Venus, Mars, Jupter, Saturn, Uranus, Neptune and Pluto. My question is: can all ...
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### Gravitational waves: how can scientists derrive the sizes and spin and distance of two merging black holes?

After recording the ripples of passing gravity waves I would imagine that some high-power math would be required to derive information about the sizes, spin, and distance of the merging black holes. ...
42 views

### How long does it take for an asteroid to get to Earth?

How long does it take an asteroid to get from the asteroid belt, to Earth? I know the asteroids don't go directly from the asteroid belt to Earth, but I know it's not quick, either. The time probably ...
64 views

### Why is this Einstein ring pink?

I'm having a hard time understanding this image in the CNN News item This glowing ring of light is from a distant galaxy. The caption (from this version of the article) says: This image shows ...
7k views

### If two black hole event horizons overlap (touch) can they ever separate again?

Hypothetical question based on my understanding that two event horizons that overlap (touch) can't ever separate again: Imagine a 1 billion solar mass black hole (so the event horizon is massive and ...
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### Has the effect of other planets on Earth's orbit been ever measured?

Since other planets have their own gravitational pull, I'm wondering if their effect on Earth's orbit has ever been measured? I know that in comparison with the Sun's pull the effect might be rather ...
53 views

### Higgs Field inside a White Dwarf

White dwarfs rank among the hottest things in the universe.In the early years of the life of the universe ,universe was very hot and the Higgs field was deactivated causing all the particles generated ...
56 views

### Brown Dwarf Cloud Models

There has been research that suggests that the changing brightness of Brown Dwarves are due to bands of Iron/Silicate clouds. Several models have been made that supports that hypothesis. My question ...
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### Brown dwarf cloud models [duplicate]

There has been research that suggests that the changing brightness of Brown Dwarves are due to bands of Iron/Silicate clouds. Several models have been made that supports that hypothesis. My question ...
2k views

### Why did this meteor appear cyan?

A meteor recently flashed over Queenland. The meteor has been described by various people as appearing cyan or aqua, so the blueness of the image can't be due to a camera issue. The colour doesn't ...
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### Small orbital body detection [on hold]

What technology is required to detect a coconut-sized sphere in Earth orbit, at average altitude of communications satellites?
64 views

### What does cz mean?

Take DS Geminorum for example, it has a cz of -2.33 [2.96] My question is what does cz mean, what does is represent? and what does the value in the brackets mean? http://simbad.u-strasbg.fr/simbad/...
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### Where a database of different z values of redshift can be found?

I was working on reshift details for various galaxies but do not know any database to find the z values given to redshift galaxies. Can anyone help?
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+100

### Has Hubble ever been used to try to image a near Earth asteroid?

This answer points out that the near Earth asteroid Apophis will likely be close to 2 arcseconds in diameter as seen from Earth during its close approach in 2029. I speculate that if the Hubble Space ...
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### How to deal with data that's billions of years old?

We look at galaxies that are billions of light years distant and draw conclusions based on the red shift of the light. How is the age of the light accounted for. We see the reality of a galaxy perhaps ...
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### dull rock/potato-shaped object seen with naked eye, moving in straight line during night. What could it be and is size and speed estimation possible? [on hold]

Between years 2009-2011, I was located in Greece, watching the perfectly dark night sky around 21:00-23:00 during summer, when I suddenly noticed a very dull dark-brown object that looked like a solid ...
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### I simply want to ask a question about quantum tunneling as an origin of black holes [on hold]

I found this site after finding a search reference about quantum tunneling (QT). I simply wanted to pose a simple question about whether or not QT was ever considered as a source for black holes ...
24 views

### What is the radial dependence of the density of Jupiter or Saturn?

Can anyone point me to the reference where I can find the density of Jupiter or Saturn as a function of the distance from its center?
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### Is the universe older than 13.7 Billion years?

I came to know that the cosmic horizon is the part of universe beyond which we cannot see. So if the light from 13.7 billion years ago is what we can observe, does that mean the universe is older than ...
61 views

### Does space being at right angles to time imply that the expansion or contraction of each occurs in a direction opposite the other's?

The Minkowski diagrams that are employed to illustrate Special Relativity depict changes in the motion of objects through the dimensions of space as occurring within a field (that's otherwise divided ...
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### What kind of effects can maintain Uranus' rings' eccentricities?

The recent paper Thermal Emission from the Uranian Ring System has been in the news recently. The introduction mentions: The ε ring, the brightest and most massive of the narrow rings, was shown to ...
46 views

### Relation between phase and magnitude

Given the phase of a planet or satellite, I can find the area illuminated visible to us, if we consider a 2D surface. But how do I find the percentage of illuminated area visible considering it a 3D ...
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### What's the number density of Oumuamua like objects?

Recently, the fly-through the Solar system of the inter-stellar object (ISO) Oumuamua caused quite a stir in the astronomy community. I wonder whether there are reliable estimates for the (local) ...
80 views

### What if there was an asteroid belt with the mass of a planet?

In the past, the asteroid belt was thought to be the remains of a shattered planet. Of course, that was all pseudoscience, the mass of the asteroid belt being 4% of the moon. I've been wondering, what ...
59 views

### Is it possible for a star to teleport or just pop out of existence? [closed]

I was on reddit and reading the glitch in the matrix sub. a common type of story posted there is seeing objects or even people just blink out of existence without a sound, light, or any other trace. ...
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### How many stars and planets have been destroyed by black holes since the beginning of the Universe? [closed]

I would like to know what is the estimated/predicted number of stars and planets that have been destroyed by black holes since the beginning of the Universe, 13.7 billion years ago.
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### Saw moving stars in the sky [duplicate]

So I was out with my friends at a bonfire and we decided to sit down and star gaze, my other friend pointed out a star that looked to be moving and we all followed it with our eyes and t was smaller ...
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### Where can I find a database of galactic spectra?

I was wondering where spectra of galaxies at various redshifts are to be found. I'm looking for ones that can be used to find the recessional velocity of the galaxy and eventually the Hubble Constant. ...
77 views

### Is the longitude assigned to sunspots spherical or projected?

Sunspot maps are created from a projection of the sun, so the coordinates of sunspots (or active regions in general) are assigned according to it. Do these coordinates correspond to actual spherical ...
44 views

### Why the torque exerted by the moon upon the Earth makes the Moon to increase his orbit? [duplicate]

For what I know, this torque exists because of the misalignment of the tidal bulge with the apsidal line Earth-Moon a certain angle $\alpha$, which makes the earth rotation to slow down a bit. But, ...
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### Roche lobe - flow of mass

In which situation can smaller star in binary fill the Roche lobe? When flow mass of smaller star to larger star? Smaller star fill the Roche lobe in Algol paradox. Does the mass of smaller star ...
45 views

### Book recommendation

I'm looking for a modern astrophysics text. I've had Barbara Ryden's book Foundations of Astrophysics recommended to me and it sounds ok, but the only review of it I've seen slagged off the problem ...
52 views

### Undisturbed planetary alignment after galactic collision

How do planets still orbit around the empty space where a black hole was after a black hole absorbs the milky way's black hole and keeps moving through space without disturbing surrounding planets ...
41 views

### Molten salt seas on the future Earth [migrated]

As the sun gets brighter, the oceans are expected to evaporate by the next billion years or so (the vapor slowly gets stripped off into space). The salt, which is less dense than most rocks, will be ...
147 views

### Is the newly discovered exoplanet 'Teegarden b' habitable?

A new exoplanet has been just discovered around the star Teegarden, at only 12 light years away.
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### Question about expansion of space time

Was the expansion of space time during big bang uniform if so how come the stars and planets be formed because and matter as well as gravity would have been same everywhere
47 views

### Depth of primary and secondary minimum in a light curve

How can I explain approximately the same depth of primary and secondary minimum in light curve? I observe star HD 36486. I tried filters MOST and BRITE. Is it related with photometric filter? When ...
39 views

### Neutron star r-process nucleosynthesis

The $r$-process in supernovae happens when a high flux of neutrons irradiates the heaviest abundant nuclei (in the region of iron), resulting in endothermic nuclear reactions. To the extent that at ...
141 views

### Universe is expanding, why doesn't time expand with it?

Reading this response When the universe expands does it create new space, matter, or something else? I understand Universe is not expanding like if it is stretching its space, but it is actually ...
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### What is the magnitude of a star, if we halve the distance to a star of apparent magnitude + 4m?

I don't know how to solve this problem. I don't have the distance or the absolute magnitude of the star and the question is confusing.
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### How Essential is the Vacuum Energy to Our Present Model of the Expanding Universe? [closed]

How essential to modern cosmology is the vacuum energy concept, and what would happen to our model of the expanding universe if it were proved to be non-existent?
126 views

### Excluding a rectangular region from an image in FITS

I am a complete beginner in astronomy. While learning DS9, I came up with the following question. Say I want to exclude a boxed region from an image FITS. The corresponding parameters according to ...
59 views

### Telescope was working and now it's not

We have a Celestron 70AZ 70mm f/10 refractor that has been working perfectly. Our children knocked it over the other day, and now when we try to view the moon, it ...
73 views

### How to calculate the orientation of planets at current epoch

For an application I am working on I am creating a simulation of the solar system. In this simulation, a user needs to be able to 'move' to any position on any planet, and have the sky be accurately ...
58 views

### Climate consequences of very large asteroids striking the Deep Ocean [migrated]

For every asteroid or meteorite that hits dry land, two hit the sea. If a Manicouagan-sized asteroid struck the deep ocean (but not above a trench),how would the H2O vapour, chlorine, iodine bromine ...
68 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 ...
5k views

### Why do things float in space, though the gravity of our star is always present? [closed]

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 ...