# All Questions

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### How did Jupiter form where it is?

Since Jupiter is the biggest planet in our solar system and is made up of mostly hydrogen and helium, (the gases the Sun uses to create energy), how come it didn't form as far out as say Uranus or ...
163 views

### What is the bluest narrow band filter mounted on ground based telescopes?

If we want to check a QSO's lyman alpha narrow band image, could a ground based telescope do that? I mean under the circumstance that its lyman alpha shifts to 3300A.
107 views

### Moon's orbit around the Sun

The Earth revolves around the Sun and the Moon revolves around the Earth. Out of curiosity I started thinking about the orbit of the Moon around the Sun and expected (assumed) it to be as follows: ...
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### How do astronomers determine the texture of an exoplanet?

So I was wondering how astronomers are able to get the texture/detail of an exoplanet or how they know a planet has water or not. I know how they discover planets by using the light of a star and ...
46 views

### Is the Universe really expanding at an increasing rate?

Here's what I just read from Wikipedia's page on the Hubble Space Telescope: While Hubble helped to refine estimates of the age of the universe, it also cast doubt on theories about its future. ...
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### Is the Dwarf Planet class really necessary?

Another way of asking this is, what is the difference between dwarf planets and asteroids? Aren't they the same things? It's just that some asteroids are spherical and others aren't...or is there ...
261 views

### is there any theory or observational evidence that our universe is electrically neutral or not?

It seems our universe is neutral in large scale. There is CP violationwiki problem about matter and dark matter. Similarly is there any theory about whether our universe is electrically neutral? ...
124 views

### The tidal locking problem concerning Earth sized planets in habitable zone around Red Dwarfs

Would twin planets orbiting around each other present a solution to tidal locking of habitable planets in red dwarf systems? It's an awfully easy equation to set up. I'm fibbing; I can't do it. I was ...
47 views

### When is Gamma Draconis closest to the zenith in London on April 4th

I am reading Roobert Hooke's paper An attempt to prove the motion of the earth from observations (1674, faksimile). Hooke writes The principal dayes of doing which will be about the 4 of April, ...
38 views

### Is it accurate to compare comets to clouds and rain?

I'm trying to avoid an opinion-based question, so before I outline the comparison I'm proposing, I will qualify the specific facts that yield this comparison. By focusing answers on the relative ...
11 views

### The physical nature of Quantum Entanglement: Two Electrons linked? Or one Electron in two places at once? [migrated]

Graduate in Computer Science and Artificial Intelligence, currently studying various fields of science in order to establish a base knowledge for cross-field lab interactivity for future projects; so ...
100 views

### What would be the practical consequences (on earth) if the Moon was not tidally locked?

I was thinking about the fact that all the largest Solar System moons are tidally locked to its primary and this question arose.
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### Is there a mechanism that makes small moons more rounded than comets?

67P/Churyumov–Gerasimenko has a highly irregular dumbbell shape. But the sample of comet shapes observed is very small, so I wonder if irregular shape is the norm for comets and for small moons. Many ...
32 views

### Trouble understanding speed-dispersion in (elliptical) galaxies

I'm learning about LOSVDs (Line Of Sight Velocity Distributions) and I'm having a bit of trouble understanding the used terms. As I understand, the LOSVD of a given (elliptical) galaxy is the density ...
63 views

### I'm having trouble achieving sharp telescope focus

I've been having trouble getting really sharp focus on my telescope. Using Saturn as a reference, with a 20mm eye piece it is very sharp. But when I go to 10mm or 6mm, it gets bigger and blurrier. I ...
90 views

### Mars night sky - how many stars visible?

How would the night sky look like from the Martian surface? Would there be more stars visible or less (compared to Earth)? Would they appear brighter/dimmer/same?
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### Are there naturally radiation shielded areas on Mars? (shadowed by terrain formations)

Mars' thin atmosphere and lack of magnetosphere exposes its surface to lots of Solar UV radiation and cosmic radiation. But Mars also has some dramatic altitude gradients in for example Valles ...
159 views

### Lunar Soil: what are those “bumps” and how were they formed?

I was watching a video of the chinese lunar landing and saw numerous bumps in the soil. What are they? Is there any theory that explains how they came into existence?
34 views

### radial velocity fitting of a binary

I have two series of velocities (HJD, $v_{1}$ and $v_{2}$ ), how to fit in detail? There is any formula on the web? $sine$ curve is easy, but I need to consider an eccentric orbit. Suppose we can ...
32 views

### Photometer vs. CCD-camera

The Wikipedia article on photometry says that These have largely been replaced with CCD cameras that can simultaneously image multiple objects, although photoelectric photometers are still used ...
66 views

### Is the angular resolution of a telescope irrespective of used eye-piece?

Suppose a telescope has aperture $D = 20$ cm. The angular resolution of such telescope, according to the Rayleigh criterion (if I have understood it correctly), is given by \theta = ...
75 views

### Isn't the date of the Big Bang a bit bogus?

If I understand correctly, the date of the Big Bang is an extrapolation of acceleration of the universe's expansion through time based on the erroneous assumption that the universe is approximately 13 ...
16 views

### Calculating effective SSN (sunspot number)

I am doing research on SSN like parameters. As I can see effective SSN is a parameter that derived from SSN or may be using other parameters. Do anyone know how to calculate effective SSN. i.e ...
189 views

### Why doesn't the sun pull the moon away from earth?

If the suns gravitational pull is strong enough to hold much larger masses in place (all the planets) and at much greater distances (all planets further away from the sun then earth) why does it not ...
20 views

### Is it possible to get the distance to a star in the IPHAS DR2 catalog?

I'm looking at the IPHAS DR2 catalog. It has the Right Ascension and Declination but I'm not seeing any distance information (lightyears or parsecs). I'm wondering, given the columns in the dataset, ...
33 views

### How to calculate geocentric conjunction time and moon altitude at a given time

Umm al-Qura calendar of Saudi Arabia determine the new moon if these criteria meet at 29th day: The geocentric conjunction occurs before sunset. The moon sets after the sun. I've got the formula ...
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### How did WASP-18b exoplanet form?

I am new to this community and not quite sure if this is an appropriate question to be asked here. Anyways its just my curiosity. As far as I could know about WASP-18b is that, it orbits very close to ...
278 views

### How do we know Milky Way is a 'barred' spiral galaxy?

In reference to the question, "How can we tell that the milky way is a spiral galaxy?" The answers there clearly sum up the question asked. But Milky Way is not just a spiral galaxy. It is further ...
106 views

### Calculating area of visible sky

Can we calculate the area of sky visible to us from the point we are standing?I mean is there any idea or experiment to calculate it?
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### Why was this asteroid (4864 Nimoy) chosen to be named after Leonard Nimoy?

The asteroid 4864 Nimoy was recently named after Leonard Nimoy. It was discovered on September 2, 1988 so it went nearly 27 years without a name. Why was this asteroid chosen to be named after him? ...
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### Day Length on Double Planets

Assume two similarly sized bodies tide-locked to one another orbiting a barycenter between the two. That barycenter orbits a star. Since the two are tide-locked, their sidereal rotational period and ...
59 views

### Will Hubble's law always be accurate?

We have Hubble's law: v=Hd where H is the Hubble parameter, which is decreasing in value, but it will be constant in the distant future. So, assumming the Standard Model of Cosmology holds true, ...
54 views

### How can we tell how many exoplanets a star has?

Part of this answer (discussing the moving center of mass of our solar system) explains that this movement is one way we know a star has planets: Bonus: We use this phenomenon to find planets ...
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### Halpha velocity fields of spirals falling into a cluster

What kind of impact would you expect ram pressure stripping / tidal interactions / harassment / interactions with the cluster potential (etc!) to have on the h-alpha velocity fields of infalling ...
23 views

### Question about extreme space distortion and creation of a new dimension

In all the illustrations regarding space distortion, I find an extra dimension that depicts space distortion. Is there any mathematical equation that proves the creation of an extra dimension ? ...
57 views

### Is there a difference between the terms 'elliptical' and 'elongated' for galaxies?

While studying the Solar System, I found that some galaxies are either elliptical or elongated. What's the difference?
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### why are solar telescopes built on lakes? the site differnece between a solar and an optical telescope

According to the wikipedia page big bear, water can cool the observatory. Big bear is in the southern California. It is better to build it on a cold high mountain with stable and clear atmosphere? ...
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### why does not Australia/Russia have optical telescopes?

Their areas are large. However I only find a 2.3msliding telescope in Australia. As far as I know, there are lots of mountains in Australia and Russia. They may have different reasons because of ...
240 views

### Computing the Sérsic profile of a galaxy from jpg images

I am trying to calculate the Sérsic profile of various galaxies from the SDSS based on the images provided by the galaxy zoo site. I am doing this as part of a kaggle competition on using machine ...
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### Why is dark energy preferred to the cosmological constant?

Dark energy and the cosmological constant are often identified, but Peebles and Ratra explain that "Einstein did not consider the cosmological constant to be part of the stress-energy term... a ...
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### What's in the center of a Galaxy?

Ok, so it's supposed that there is a black hole in the center of any galaxy, that makes my head explode because: There is light in the center of the galaxy, but it is supposed that black holes, also ...
2k views

### Is Pluto still a dwarf planet?

Recent news seem to suggest that astronomers are arguing about whether Pluto should become a planet again. However, I cannot find an official source for this. Is this actually true?
158 views

### Do heavier elements breakdown during supernova?

Heavier elements like gold, uranium etc. are formed at the end of a star's life. As the star explodes into a supernova, it gives rise to nebula which is the birthplace of new stars. But as the star ...
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### How close are we to be able to detect and measure gravitational lensing inside the milky way?

Gravitational lensing takes advantage of statistically uniform distributions of background objects in order to infer a credible map of dark matter concentrations that isn't too noisy. If there are too ...
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### What more could be learned from a rare astronomical event if we knew precisely when it would occur?

This is actually related to a question I recently asked on Worldbuilding, but seemed more appropriately asked here. To keep this from being too broad in scope, let's assume that someone figured out ...
520 views

### Visibility of Apollo 11 module

I wasn't around when man landed on the moon in 1969. When I see the moon, I always wonder, were people able to see the rocket? Yesterday, I looked at the moon in daylight and wondered again. My ...
103 views

### What kind of things I could “see” with an amateur radio telescope?

There are apparently not many reasonably priced radio telescopes available for the amateur users. I only could find this one, which costs ~10 k€. Reading the page, I don't get a good overview what ...
115 views

### Is sundial time entirely dependent on solar azimuth?

I've visited several "how sundials work" sites and can't seem to get a clear answer to this: is "sundial time" just a linear function of solar azimuth? More specifically: When the sun is due ...