# All Questions

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### Galaxy centre X structure - could this reflect impact of black hole at galactic centre

As reported in this science article X Marks the spot Centre of Milky Way, a X shaped feature is confirmed centered on our galaxy's centre, when looking on from within the plane of the Milky Way. In ...
2k 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 ...
2k views

### Do far away planets reflect light in the same way our moon/earth reflects light?

Here’s a scenario: Say you’re up in space and you’re far enough way that you can see the planet earth. Whilst looking down, you can see blue sky, blue water and green land and white clouds and ...
440 views

### How often is a blue moon?

A blue moon is two full moons in the same month. How many times will a blue moon occur in the average lifetime of say 70 years?
262 views

### How many stars would it take to draw a line across the middle of the sky that appeared solid?

I was talking with a friend about how slowly the star field changes (based on the speed that we are moving through the galaxy) and I started to wonder about a star's visible size. They are basically ...
697 views

### Does Eddington's variable polytropic index better fit data from the Standard Solar Model?

I came across a 1938 paper by Arthur Eddington1 in which he discusses stellar polytropic models where the polytropic index $n$ varies inside the star, decreasing from a value $n_2$ at the surface to a ...
3k views

### How can a supermassive black hole cause so much energy to enlighten its matter when its massive gravity prevents light to escape?

To cite the German newpaper article Astronomen beobachten erwachendes Schwarzes Loch: Das Materie-Monster sitzt den Angaben zufolge im Herzen der 42 Millionen Lichtjahre entfernten Polarring-Galaxie ...
400 views

Is it true that stars start with a rocky core, then collect hydrogen by the gravity of that rocky core, just like planets collecting materials?
181 views

### Where are the Moon rocks from Apollo? [closed]

There were so many Apollo Missions, and they landed on the moon (so they say). When astronauts came back to Earth from the moon, they brought Moon rock samples. Where are these moon rocks/samples now, ...
127 views

### Which 16 antenna locations were used this MeerKAT radio image?

The final configuration of the MeerKAT radio array will be 64 dishes. In the press release of July 16, 2016 a radio image is shown using a completed sub-set of 16 dishes. Which 16 are these? I can ...
154 views

### Do far away stars that we observe today still exist?

I don't know much about the astronomy or the universe but enjoy reading articles from time to time as they pop up. Just finished reading an article on CNN that discussed how a South African telescope ...
49 views

### Could celestial coordinates be encoded into three-word combinations?

I came across this cool tool which encodes geographic coordinates into 3 dictionary words - table.lamp.chair - for example. You can see their map here https://map.what3words.com/. It divides the world ...
262 views

### A question about the distribution of mass among the planets in the Solar System

Is it coïncidence that the mass of a planet has about its maximum in the middle planets (Jupiter), while the mass of the closest and furthest planets has a minimum (Mercury and Pluto)?
309 views

### Energy carried by solar wind

What are the velocity, mass, and charge distribution of the solar wind. Near the earth within the magnetosphere in the ecliptic Near the earth but outside the magnetosphere in the ecliptic Outside ...
587 views

### Do primary mirrors in large observatories undergo regular removal and re-coating of the aluminum? Why?

Performance of astronomical mirrors that are exposed to the environment for long periods of time can experience a slow degradation of performance. They usually need to receive some kind of regular ...
117 views

### Why is the exoplanet HD 131399Ab so hot?

Recently, a fascinating triple-star system with an exoplanet has been discovered (arxiv). I'm very surprised about the temperature of the exoplanet: it is roughly 850 kelvin, even though its orbit ...
89 views

### Observed data: Why so many MPECs about TNOs lately?

The Minor Planet Electronic Circulars (MPECs) for July 15 through July 18 reported an unusually high number of re-observations of known trans-Neptunian objects (TNOs). These were found in the Pan-...
193 views

### Extraction of error spectrum in Sloan Digital Sky Survey

I need to know does SDSS spectrum contains error spectrum as well? http://www.sdss.org/dr12/spectro/spectro_basics/#AbouttheSpectra The above link says, further HDU's contain error spectrum and than ...
775 views

### Can stars be seen in the background when looking directly at our solar system?

Imagine viewing the solar system from the outside: Considering the sun is quite bright, would you still be able to see stars in the background, or does the sunlight disable us to do so? Consider ...
288 views

### Do constellations change?

Many stars are part of constellations. Due to dark matter the stars have velocities which are nearly the same unregardless their radius of orbit around the centre of the Milky Way. Also, it takes ...
107 views

### Do differentials in the Earth's density cause the flyby anomaly?

The flyby anomaly is an occasional, unpredictable, and as yet unexplained discrepancy in acceleration of satellites when they pass close by the Earth. It causes an increase of up to 13 mm/s during ...
556 views

### Why do astronomers not use past tense when discussing observations of the universe [closed]

Describing a galaxy 70 million light years away, I consider it incorrect to state for example "it has an active black-hole at its center". It did 70 million years ago, who knows what is out there now. ...
718 views

### When did “resilvering” large telescope mirrors actually refer to aluminization, and why was it necessary?

This answer nicely summarizes the general picture of historical use of silver for mid to large size telescope mirrors, and the shift to aluminum once good quality vacuum pumps and chambers suitable ...
154 views

### What would happen when the earth consumed all its fuel? [closed]

What would happen when a planet consumed all its fuel and its core extincts. Would anything change on the planet? Can this ever happen before its star did so? If not, why?
299 views

### Do planetary rings always follow rotational axis?

In solar system,most ring systems seem almost lies exactly on the equator of planet, is it possible that the plane of a ring system is not lie on the equator of the planet?
251 views

### Will Gaia detect inactive neutron stars?

Will the astrometric precision of the Gaia space telescope be able to detect the gravitational influence of cold old solitary neutron stars on the movements of stars? At least in a statistical sense ...
173 views

### Are 3D coordinate data from Sloan DSS-III available & easily accessible to non-pros?

Of course the newly announced SDSS-III data and maps from the Sloan Digital Sky Survey with 1.2 million objects, along with all previous data sets are openly available, and I'm sure there are many ...
170 views

### Where did the grand design spiral galaxy designation come from?

What is the history behind the name that we gave to that class of galaxies?
195 views

### How well supported are the theories of black-holes containing their own universes?

The thought crossed kidnapped my mind one night almost a year ago. I was laying down, but I was very interested in thinking about the secrets of a black-hole. Nat. Geo. - News article What does the ...
255 views

### If a hot Jupiter collides with the parent star, does it enhance or reduce the life of the star?

Suppose a hot Jupiter is collided into parent star due to tidal force, does the life of the star becomes longer due to extra hydrogen, or becomes shorter due to extra mass?
85 views

### Has anyone filmed a total lunar eclipse from the Moon's perspective?

With all of the footage we have of total lunar eclipses, has NASA, ESA, or any other space program ever taken a photo or video of it from the Moon itself?
127 views

### Can one calculate the size (i.e. the radius) of our universe? [closed]

If one can estimate the mass of our universe, might one also calculate its ultimate size, (after it fully expands), based on the Schwarzschild formula for the radius of a black hole? Please note that ...
103 views

### Are there any reliable optical measurements of the radius of a neutron star?

I know that there is plenty of theory to predict the size of a neutron star: my question is whether or not there are any reliable size estimates based on observation. Please note that, to be reliable,...
197 views

### Do planets form around lone stars, multiple stars, or both? Do we know this yet?

Since about 1990 astronomers been able to detect planets around other stars, using a couple different techniques, which is amazing. By this point, do we know whether planets form only around single ...
191 views

### How does 2015 RR245 compare to the other KBOs predicting “Planet 9”?

2015 RR245 was recently announced, in a highly eccentric orbit in the KBO. From what I understand, the so called "Planet 9" was predicted because these objects tended to be pointed in a particular ...
227 views

### Spherical Accretion (Bondi Model)

I have a question. I studied Bondi's model for spherical accretion. I know the assumptions made in the model are big and that they are rarely representative of what happens in astrophysics. What I ...
479 views

### Was the use of silver on 'optical' telescope mirrors more common in the past? Why?

In the past, weren't many astronomical telescope mirrors periodically removed and 'resilvered', and wasn't this actually done using silver? I'm guessing that this is much less common now - new ...
4k views

### Why are Saturn bands much fainter than Jupiter's?

The atmospheric composition of both planets are very similar. Then why are Jupiter's bands more visible (North and South equatorial belt, etc.): Whilst Saturn's are not: (except for the storm of ...
212 views

### Solar Eclipse: How it occurs

In relation to the image above, although the topic relates to math, how can I visualise the situation described in the final equation presented, i.e., the declinations, ascensions, solar and lunar ...
63 views

### Why aren't planetary bodies static? [duplicate]

Why are planets moving in the first place? Gravity causes them to orbit, but why move at all? note: this is not a question on why planets orbit each other, I know the reason for that is gravity. ...
4k views

### Could a cross-ringed planet exist?

My title doesn't do my question justice in explaining, but the kind of satellite system I'm thinking of is two rings on two separate axis, much like (if you've seen it) the film 'Treasure Planet' ...
3k views

### Why is there a supermassive black hole at the center of every galaxy?

According to https://en.wikipedia.org/wiki/Sphere_of_influence_(black_hole) the gravitational sphere of influence of a supermassive black hole is really limited compared to the size of its hosting ...
878 views

### Will Saturn's Moons be destroyed?

I heard that Saturn has 62 moons with confirmed orbits, 53 of which have names and only 13 of which have diameters larger than 50 kilometers. Some come within 1km of each other. How do these moons ...
6k views

### What are the small things, look like stars, moving in the sky? [duplicate]

I have always been observing something that looks like a star but not as bright as a star moving from south to north at the same time every night. What is it? It cannot be a star because I know ...
3k views

### Kepler's second law of motion

Planets sweeps out equal areas in equal times. Is the area being calculated here the area of a triangle? You draw a straight line from the center of the sun to the earth at point A. The Earth moves ...
1k views

### Data reduction and photometry without IRAF?

The IRAF package is old. I've been looking around for a more modern software to replace it in the processes of CCD data reduction and photometry, but haven't been able to find any. The closest I've ...
163 views

### How massive can a cold solid object be?

I understand that a neutron star is dense enough that adding more matter will increase the amount of degenerate matter directly, and the limit to its size is about 1.4 solar masses. But if an object ...
424 views

### Future redshifting and effect on the 'pitch' of CMB radiation

After discovering this question exploring the sound of a blackbody, I started wondering about the sound of the Cosmic Microwave Background radiation from the Big Bang, specifically what the current ...