1
vote
1answer
75 views

How do we know that the Universe is still expanding now?

Yes, I know that most galaxies have a red shift and that means they are moving away from us. The problem is that the farthest galaxies are 13.8 billion light years away. That means that the info is ...
0
votes
1answer
75 views

Alignments of planets

I am going to ask an odd question, It is: In most of the images of our solar system we see that the planets are arranged in a straight line. As the paths of the planets are elliptical, could it be ...
4
votes
1answer
155 views

Why aren't new stars in Earth's relative proximity constantly discovered?

Okay, bear with me. In layman's terms: The estimates vary, but on a clear night, away from big cities, one can see up to 5000 stars in the sky. All those are in the Milky Way, but they're hardly ...
1
vote
0answers
31 views

Which is the most accurate stars catalogue for J2000 epoch?

I'm developing a planetarium software. I have no idea about how to obtain stars right ascension and declination. Searching on Internet I have found that Wikipedia has AR and DEC for a lot of stars. ...
1
vote
3answers
37 views

Is the duration of a sidereal year stable?

According to this essay by Phil Plait, the duration of Earth's sidereal year is 31,558,149 seconds. Is this figure stable? If I were to meaure Earth's orbit several million (or billions) of years in ...
4
votes
2answers
313 views

Camera reaching the event horizon

This question came to my mind after reading this. I think it is safe to assume that the supposedly thrown camera would not reach the event horizon in one piece. So my question is : If I dropped a ...
6
votes
2answers
171 views

Trying to understand the way Saturn's ring look in this famous Cassini image

You all probably know the famous The day the Earth Smiled image. For the life of me I can't understand what's going on with the rings there. Seems like the "bottom" half of the rings is the half that ...
3
votes
2answers
87 views

Why doesn't Jupiter increase the chances of an asteroid to strike the Earth?

I often hear the hypothesis that Jupiter decreases the chances of an asteroid strike on the Earth, but my question is, why does it only decrease the chances ? While Jupiter can deflect some ...
0
votes
0answers
14 views

What would the apparent size of the four stars in the Capella system be from the L1 point between the first pair?

Capella is a system with four stars in two binary pairs (source: Wikipedia). If an observer were located at the L1 LaGrange point between the larger pair, how many degrees of the sky would each of the ...
0
votes
2answers
73 views

humans leave earth forever?

my question is regarding space travel and also will some countries have colonies on mars etc cause the clear reason NASA etc are trying to send manned mars mission is to get raw materials etc or ...
1
vote
1answer
35 views

Can a tidally locked planet have their own habitable zone?

As we know, if a planet is near a star and is tidally locked, then at near side it is very hot and at far side it is very cold. But between 2 sides there should be a gradient of temperature change and ...
1
vote
1answer
81 views

What is the gravitational force felt on Earth from the other planets in our solar system?

How much gravitational force is felt on earth from the other planets in the solar system? The sun exerts the strongest g-force, holding us in it's orbit, followed by the moon which affects the tides ...
1
vote
1answer
39 views

Gyrochronology?

I recently became aware of the work of the Kepler Cluster Study. In January of this year it was announced that a long awaited method of finding ages of "cool" stars is now available. This is huge and ...
1
vote
2answers
131 views

A camera and time dilation?

If I travelled near a black hole, my time would progress slower relative to someone on Earth. This is clear enough. However, what if we sent a probe with a camera to a black hole? When we watch the ...
1
vote
1answer
74 views

Beginner telescope for my daughter [closed]

My husband and I are trying to figure out what type of telescope to get our young daughter. We would like to be able to see planets but nothing too extreme. Just something to get her started. She has ...
9
votes
1answer
69 views

Why do we believe that the super massive black holes at the centers of two merging galaxies would themselves merge?

When listening to podcasts or watching youtube videos of astronomers discussing galaxy mergers, I often hear talk about how the super massive black holes at their centers will themselves merge during ...
2
votes
1answer
69 views

Are there accurate equinox and solstice predictions for the distant past?

I am trying to find information on the equinox/solstice dates before 1600, more exactly referring up to 10,000 BCE so as to create a sort of calculator on an Excel spreadsheet. I have read about the ...
5
votes
3answers
141 views

Are black holes expanding?

We know that it is a commonly heard claim that in every black hole there is a universe. It is also believed that the universe is expanding. If we use both of these, can we conclude that every black ...
6
votes
0answers
31 views

How frequently does a comet drastically change its orbit in the Solar System (like 67P did in 1959)?

Comet 67P/Churyumov–Gerasimenko flew by Jupiter at only 0.05 AU distance in 1959. This encounter lowered its perihelion from 2.7 to 1.3 AU (almost becoming an Earth crossing comet). Since it happens ...
4
votes
2answers
113 views

Dating very old objects/events

After reading this space timeline, I have wondered how they managed to make these assumptions about various events like when the first black holes formed. This is obviously far beyond the good ol' ...
2
votes
1answer
35 views

How long time since a typical asteroid collided with another asteroid?

How pristine and ancient are asteroids really? I suppose they melt and reform when they collide with each other. How frequently do they collide with each other?
1
vote
2answers
63 views

Delta-v from Mercury surface to Venus surface

What it says on the tin: using the most efficient launch opportunity afforded by orbital mechanics, what delta-v would you have to impart to a payload to send it from the surface of Mercury to crash ...
4
votes
2answers
95 views

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 ...
1
vote
0answers
6 views

What instruments/science goals have the highest priorities for a combined orbiter and lander to Europa?

A NASA mission to Europa seems to have a friend in congress. What would be the most important instruments and science goals for such a mission? Seismometry, radar, surface chemistry, a drill/melter, ...
2
votes
0answers
45 views

Theoretically, can a solar system evolve around lagrange points

My question is, during the evolution of a solar system is it possible to end up with a massive planet around a star with two small planets around their $L_4$ and $L_5$. Since we know it is not ...
2
votes
1answer
45 views

Is there a way to estimate the age of M dwarf stars?

Wolf 1061 (only 13.8 ly away) was recently found to have three rocky planets one of which is in the habitable zone. It was stated on the english wikipedia site that it has a very stable light curve ...
1
vote
1answer
24 views

When did the Scutum constellation receive its current name?

While cleaning my desk, I found an out of date star map (puts the cleaning into perspective, huh?) where the Scutum constellation is still referred to as Scutum Sobiescianum). This is the original ...
3
votes
3answers
51 views

Has someone ever captured footage of the collision of a meteoroid and a meteoroid?

For a video game I'm looking for footage of a collision of meteoroids or maybe asteroids, not planets. Even though I have searched for a while I couldn't find anything. So has anyone ever captured ...
2
votes
1answer
47 views

Is this the Cancer constellation?

In this photo taken by SpaceX during one of their Falcon 9 launches, I noticed a familiar group of stars but I'm not sure of what it really is. I encircled it in red, is this group the Cancer ...
3
votes
3answers
79 views

Are moons geologically active?

Are there natural satellites in the Solar System that are geologically active? This includes volcanism, existence and motion of tectonic plates, et cetera. Is it a common or a rather rare feature ...
7
votes
4answers
192 views

Why does it make sense to say the universe has no centre?

If we suppose we and everything in the universe is perfectly flat. That is, we have width and depth, but no height. And we are situated on the surface of a balloon blowing up with air and expanding ...
2
votes
1answer
47 views

Is the sphere of influence of our milky way's center super massive black hole same as the Milky way's radius?

The sphere of influence is a region around a supermassive black hole in which the gravitational potential of the black hole dominates the gravitational potential of the host galaxy(found it in wiki). ...
6
votes
2answers
158 views

Why do black holes choke?

I read that a black hole can sometime "choke" on a star: "...the disrupted stellar matter was generating so much radiation that it pushed back on the infall. The black hole was choking on the ...
2
votes
1answer
47 views

A beginner project in plotting celestial bodies in 3D coordinate space

As a data visualization task, I'd like to plot some celestial bodies in 3D coordinate space. I assumed there would be a lot of databases where celestial bodies are recorded along with an XYZ ...
5
votes
4answers
180 views

22nd is shortest day in some places, but the 21st is shortest in other places. Can this be true?

The Winter Solstice in the Northern hemisphere in 2015 is December 22 at 04:49 UTC. Where I'm located in Nova Scotia, Canada, that's December 22, 00:49 AST. And so I would say the shortest day of ...
5
votes
1answer
167 views

Can a star have a ring system?

I often hear about planetary ring systems, and even some moons might have them, but how about stars? Can a star also have rings?
1
vote
2answers
95 views

Can planets have orbits other than elliptical or circular orbits?

Can planets have orbits other than elliptical or circular orbits? All of the planets in our solar system have either a circular orbit or an elliptical orbit (perhaps like Pluto).
2
votes
1answer
112 views

If the Sun got larger, but maintained its luminosity, would the Earth get hotter or colder?

A recent question If the Sun were bigger but colder, Earth would be hotter or colder? asked - if the Sun got bigger and cooler, would the Earth heat up or cool down. I think the answer to that is ...
2
votes
1answer
86 views

Is Darkness Faster Than Light?

I've been looking around, and can't find a solid answer. Many websites say darkness is the speed of light due to the fact it is the absence of light, but other sources say otherwise, that in some ...
2
votes
1answer
53 views

If the Sun were bigger but colder, Earth would be hotter or colder?

That is the question. I know the concepts of luminosity $(L=4\pi R^2F)$ and the flow $F=\sigma· T^4$, with $T$ the temperature in its surface. But how I use that to know if the Earth would get warmer ...
2
votes
2answers
76 views

Would all neutron stars inevitably collapse into black holes due to quantum tunneling?

The materials inside a neutron star are densely packed (extremely close to each other) and as time goes by say about an eon later, most of the neutrons would eventually tunnel into each other and ...
9
votes
1answer
121 views

How quickly does a supernova heat up/expand?

Suppose there's a star out there that's a lot more massive than the Sun. Suppose further that orbiting this star is a planet not unlike Earth. Water, oxygen, civilization, and all. Now the star ...
6
votes
4answers
111 views

Do all planets have a molten core?

As we know, according to Wikipedia on Earth's inner core: The Earth's inner core is the Earth's innermost part and according to seismological studies, it is primarily a solid ball with a radius of ...
4
votes
1answer
45 views

Do the magnetic fields of stars and/or other planets reverse?

I've heard of the magnetic field of the earth reversing poles over the course of thousands of years but do stars and other planets (specifically gas giants) also experience this? If so how does it ...
7
votes
4answers
202 views

Do asteroids have a gravitational field?

I know that asteroids are huge chunks of rock, orbiting a solar system. Do asteroids have a gravitational field and do they gravitationally attract each other to form planets?
5
votes
2answers
57 views

Temporal path through Hertzsprung-Russell diagram?

Is there graphic of typical temporal paths that stars take through the Hertzsprung-Russell diagram?
0
votes
1answer
60 views

What is the difference between a neutron star and a white dwarf?

What is the difference between a neutron star and a white dwarf? I know that both are very dense even if they go through different phases.
2
votes
1answer
40 views

Why is there no time in the distance equation using Hubble constant, red shift and speed of light?

So I had some problem and I think I solved it, then I began to dig out things around it and I found some equations using red shift etc. to get speed of the object in Universe relative to us and then I ...
5
votes
1answer
87 views

Are there real uses of abstract algebra in astrophysics?

It is known that a physicist must have, at least in general, a good level in mathematics in order to research and understand other people's works. Linear algebra is a good example, as ODEs and ...
1
vote
2answers
47 views

Get date and time by position of the sun and the observer position

I am working on an astrology project (don't panic, my question is about astronomy or math), where I need to figure out some values by the longnitude of the planets. I have a program for this, the ...

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