# All Questions

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### From what distance can one object influence gravity of another object?

Each object in the universe has its own gravitational influence on all other objects in the universe. What distance do they have to be from each other to create only one gravitational influence? ...
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### Planetary gas giants

I've read that a gas giant, like Jupiter, doesn't have a rocky surface. But planets must start as a rocky conglomerate of flotsam. Is the interior so hot that all the material is molten and there ...
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### What is the relative time difference between us and a star system in outer layer of our galaxy?

Just curious to know what will be the time difference between someone living on the outer layer of our galaxy and us, considering the known facts that Time is relative to gravity Our sun goes around ...
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### How did Kepler determine the orbital period of Mars?

As I understand it, Kepler used the orbital period of Mars, along with observational data of Mars' and the sun's position in the sky to derive the orbits of Earth and Mars. (As described, here: ...
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### Is there a flaw with the newer purposes and correlations attributed to the HR diagram? (And would a third axis of mass correct the enclosed flaw?)

When I was younger, I was looking at HR diagrams, and began to experiment with the HR diagram. I was looking at plotting different groups of stars on the HR diagram when I found RV Tauri stars. ...
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### How many black holes exist?

How many black holes exist and what is their distrubtion over mass? There is a list of black holes, but I'm interested in an estimate of all black holes in the visible universe.
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### Is there a fundamental difference between a small galaxy, and a large star cluster?

For instance, If a large globular cluster were somehow ejected from its galaxy, and was observed by astronomers, would they call it a galaxy, or would there be characteristics of the star cluster that ...
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### Is the universe expanding faster than speed of light?

The celestial bodies like stars and galaxies are moving away from each other. How fast are they moving apart? Is that speed more than the speed of light?
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### Are black holes orbiting around each other?

Obviously, bodies with low gravity force orbit around another one with higher gravity force, if they are close enough to each other. Is it true also for objects like black holes? Are they even able ...
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### Do all moons orbit their planets on the ecliptic?

Do all moons orbit their planets on the ecliptic? Do they all follow this same process as the moon that orbits Earth, or is their some random distribution with some even having extreme polar orbits.
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### Generalised planets?

There is somewhat of an abstract way of generalising the notion of planets. Standard definition of planets is, obviously: "planets are the objects formed from the residual material surrounding a ...
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### How Soon Could a Waxing Crescent Moon Be Seen?

Question: Apart from a Solar Eclipse, How much time is needed until a Waxing Crescent Moon be seen following a New Moon? Would the time of year be significant? The Vernal Equinox + 1 Month. ...
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### Do massive bolide entries coincide with meteor showers?

Are exceptionally large, bright, meteors (such as Tunguska or Chelyabinsk) more common during common meteor showers like the Perseids, or the Leonids? If not, why is that? Do the meteor showers ...
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### Where is the flaw in this hypothetical concept of escaping event horizon using another's blackhole flyby?

imagine two black holes approaching each other in a way that they will perform just very close flyby. You have a spaceship just below the event horizon of one black hole in line between centers of ...
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### Why do pre-main sequence stars show lithium in absorption?

This paper and this paper state without discussion that the presence of lithium absorption in the stars they observe as strong evidence of these stars being pre-main sequence stars. Because they state ...
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### What type of planetary-mass object would Planet Nine be?

Given that Planet Nine is hypothesized to be 10-20 times the mass of the Earth orbiting the sun some 200-2500 AU out, what kind of planetary-mass object would it be? Even given that it has apparently ...
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### How could we detect planets orbiting black holes?

Detecting planets orbiting around stars can be made with several methods, transit photometry seems to be by far the most popular method nowadays. I wonder how we could detect planets orbiting black ...
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### The contents of potential “message” in the Wow! signal lost?

The Wow! signal is still an enigma. I understand the incredibly high signal strength it entails. This during some time-period because the sweep of the alignment (or rather the receiving station). ...
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### What is an “arc” spectrum ?

I sometimes hear about astronomers using an arc spectrum to calibrate observations. For example a "He-Ar arc spectrum". What is an "arc" in this context? I assume it's nothing got to do with angles ...
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### How many stars are in the Sculptor Dwarf Galaxy?

The Sculptor Dwarf Galaxy is a small satellite Galaxy of the Milky Way. There are many such satellites galaxies and I'm trying to compile basic data on them. However, I can't find an estimate for the ...
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### Venus transending behind the Earths moon December 7, 2015

Observing from Earth what are the odds thats Venus does not line up in conjunction with earths moon and does not transend behind the moon but slightly below or above with a complete visual of venus ...
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### How does the appearance of the analemma vary with latitude

How does the appearance of an analemma vary with latitude? This what I take to be a definition of an analemma: If the position of the sun is plotted or photographed at noon clock time (say UTC) every ...
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### What happens to oxygen produced on the Sun (or other stars)?

Through nuclear fusion, the Sun can (or at the very least, someday will) produce atoms of all elements up to and including oxygen. And in terrestrial chemistry at least, when you combine oxygen, ...
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### Why is metallicity important in the death of stars?

I always thought that mass was the sole determinant of a star's fate. Then I saw the table here. So why does metallicity influence a star's ability to become a black hole or neutron star? Does it have ...
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### If 50 tons or more of debris falls to earth everyday, is Earth getting heavier?

In turn, would that increase our gravitational pull?
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### Does the universe expand at the same rate everywhere in the universe?

Specifically, I am wondering if some areas of the universe expand faster than other areas and whether the faster expanding areas diffuse the expansion through the slower expanding areas or does the ...
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### Gravitational lensing in Newtonian physics

Famously, when Eddington attempted to measure gravitational lensing during the Eclipse, it was the measured magnitude of the lensing that gave gravity [pun, obviously, intended] to General Relativity ...
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### What types of signals is SETI (and other such efforts) looking for?

This seemed to be the closest group for this question. Every few months there are a few articles asking "Are we alone in the universe" which focus on the Fermi Paradox, the Drake Equation, and end by ...
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### Speed of blast from supernova

How fast does the blast front of a supernova expand at? Is it close to the speed of light or is it less than a quarter of the speed of light?
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### Stars in the sky

Are the stars we can see with the naked eye in the night sky only from our Milky Way galaxy or can we see stars from Andromeda? I am aware we can see other celestial objects like nebulas and the ...
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### Calculating RA/dec from JPL ephemeris data

I'm using JPL planetary ephemerides to calculate the position of planets. Using DE405 ephemeris (using a parser provided by Project Pluto with all tests passing). I am fetching the position of Mars ...
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### What kind of telescope do I need to see most of the Jupiter's moons?

I have a simple Newtonian reflector telescope. Using it, I am able to see the Galilean moons of Jupiter. However, Jupiter has much more moons than that (Wikipedia says 67 have been discovered this ...
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### Why are Hubble images “Cut”

Whenever you take a look at a photo that is taken by hubble, Lets say M87 or Eagle Nebula or maybe Ultra Deep space field, The Image is always "Cut" Like this : or this I want to know reason ...
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### Do all stars have the potential to have life supporting planets?

Regardless of how big or small, how hot or cold, do all stars have a goldilocks zone, and if so, could any given planet in this zone (with the right configuration) support life?
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### At what density does helium burning start in a star?

I have seen several references that say that helium burning begins in a star once the core temperature reaches $10^8$K (such as here) but nowhere that says what density that corresponds to. Does ...
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### Formation of Cosmic Microwave Background

It is said that the cosmic microwave radiation (CMB) was formed when the universe was 379,000 years old. How is this calculated?
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### What can a lunar-based telescope do?

What can a lunar-based telescope do? If the band is ultraviolet and it can do high time sampling exposure, maybe it can be used to get distance for a star with stable pulses. However, the star should ...
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### Does the universe have an edge?

I've heard the universe is just an empty cavity. Does the universe have any edge or stop or is it just an infinite empty cavity?
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### Accurate way to programmatically generate a main sequence star?

I am working on a (personal) programming project, part of which involves generating random stars and their parameters. In order to create a procedurally generated star, I want to randomly select as ...
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### Any cheap (less than 100 euro) telescope for observing Jupiter? [closed]

The moon is not challenging. I would like to observe the big planets and their rings.
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### Why do we think that there is no two-solar-mass black hole?

We think that the mass boundary between neutron stars and stellar mass black holes is around three solar masses. The maximum mass of the neutron stars now is two solar masses and we may find a 2.6 ...
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### Calculating Angular Distance

Given the horizontal coordinates of two objects in the sky, how does one go about calculating the angular separation between them?
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### Does Doppler shift affect apparent pulsar frequency?

We know that redshift and blueshift is the result of the frequency of light waves reflected or emitted by an object lengthening or shortening due to the relative velocity of the observer moving away ...
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### Collision of 2 black holes

There is a large number of visible Supernovas. Each week - about a 20 Supernovas Type 1a around the Universe. Is there collisions of Black Holes? What is this collision called? E.g. 2 black holes ...
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### Why does time get slow near a black hole? [closed]

Why exactly does time get slow around a black hole? And does it provide a way to go into the future?
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### What is the orientation of planetary orbits?

I'm working on a planetary motion simulator. I've been working through the equations anomaly, eccentricity, etc. The one thing I'm curious about is if all the ellipses are oriented the exact same way ...
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### Acronyms of catalogs in SIMBAD database

How to find acronym of specific catalog in SIMBAD database? For example, I want to select stellar names, object types and all binary stars from "Stellar effective magnetic fields. II." catalog ...
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### Pictures of large galaxies

The Andromeda Galaxy is tens of thousands of light years in diameter. That suggests that the most distant stars in the Andromeda galaxy is up to tens of thousands of years "behind" in their orbit ...