3
votes
1answer
42 views

The role of gravity during planetesimal accretion

As far as I understand, during the formation of a planetary disc, grains of dust stick together due to collisions and chemical bonding. Considering the size of the grain - say, 1 mm - and the speed - ...
0
votes
3answers
39 views

Why dont we have a browsable spacetime augmented virtual solar system?

Wouldnt it be nice to be able to render any viewpoint from all the data transformed into a point cloud, an augmented virtual reality of moving objects in our solar system. I would just like to be ...
3
votes
2answers
154 views

Which galaxy is receding from the Milky Way the fastest? What is known of the mechanism behind its recession?

Galaxies are always in motion relative to the Milky Way. My question is, which galaxy is receding the fastest from our viewpoint? What is the theorised mechanism that causes this?
2
votes
1answer
40 views

What is the Habitable zone all about?

I've a question on Habitable zone. Does Habitable zone represent the region where we humans or the living beings of earth can survive? Or is it a region where life can exist? If it is second I want ...
4
votes
4answers
245 views

What is the exact mass of the Sun?

I am having trouble finding data on this. So far, I have found at least seven values: ...
2
votes
3answers
138 views

What happens if you fail to reach escape velocity for the galaxy?

I was listening to Skeptics Guide to the Universe the other day, and Steve Novella mentioned that the escape velocity for the galaxy is 544 km/s. If an object fails to reach escape velocity on Earth, ...
2
votes
2answers
83 views

Limit of hotness!

We know that there is a limit to which an object can be cooled down that is absolute zero, and getting there is also not very easy we may have to wait infinite years to get to that point. But is there ...
8
votes
2answers
203 views

How old is our Sun in Galactic years?

A year is measured as the amount of time it takes Earth to orbit the Sun once, a Galactic year is the time it takes our sun to make one full orbit of the center of the Galaxy. In Galactic years, how ...
26
votes
6answers
735 views

How are black holes found?

Black holes have so much gravity that even light can't escape from them. If we can't see them, and the suck up all electromagnetic radiation, then how can we find them?
6
votes
0answers
161 views

Magnetic fields of peculiar HgMn A type stars

Do HgMn (peculiar A type) stars really possess global magnetic fields? See, for example, this paper by Hubrig et al. from 2012.
6
votes
4answers
384 views

Are the stars in constellation located in a plane or they are in different distances

Are the stars in constellation located in a plane or they are in different distances from each other and when we observe them from the Earth we think they are all in a plane?
4
votes
1answer
45 views

Is CMB Polarization simply the temperature gradient of the CMB?

Firstly, I have to admit that I don't fully comprehend the concept of "CMB Polarization". When I think of "Polarization", I normally think of the optical definition of polarization, as defined by the ...
3
votes
1answer
73 views

How bright is the full Earth during the lunar midnight?

At lunar midnight (i.e. the new moon as seen from Earth), the Earth is in its full phase with its entire disk in sunlight, and it is the brightest object in the lunar sky. How bright is it, and how ...
4
votes
2answers
122 views

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. ...
17
votes
2answers
3k views

Does the Earth have another moon?

I was just wondering what are the chances that there is a small object (say less than 1 km but more than few meters) that orbits the Earth but has remained undetected by us? Are we actually ...
3
votes
1answer
57 views

Smallest body that can be observed from Earth?

What is the minimum size of an object that can be observed from Earth with our most powerful telescope? I understand that the answer depends on how far the object is from Earth. For the sake of ...
1
vote
0answers
38 views

stellar evolution fortran code-runge kutta mass step from center to fitting point [closed]

I am trying to integrate the four stellar model equations from the core to a fitting point and from the surface to the fitting point ($x_f$). When I start the outward integration, however, I have to ...
1
vote
3answers
80 views

Stable polar solar orbit with the Earth continuously observable

Is there a stable polar solar orbit such that the Earth is always in view and not eclipsed by the Sun?
2
votes
2answers
113 views

Hamiltonian of general three body problem

i try to extend my analysis from planar restricted three body problem to the general one. Is there anyone that can help me to find out the Hamiltonian for this prolem in cartesian coordinates? I ...
6
votes
1answer
82 views

What determines the configuration of orbits in a binary system?

There are essentially two configurations of orbits a system with two bodies can have: A configuration where the paths do not cross: A configuation where the paths cross: Note: Size of the ...
11
votes
1answer
228 views

If the moon wasn't receding from Earth, what would be the impact on the weather and tides?

Moon is slowly receding from Earth, which means that after its formation it was much closer to the Earth than now. How would weather look like if it wasn't receding at it would be now as close as at ...
7
votes
5answers
255 views

How do you define the diameter of the Sun

That is, it's twice the radius where the radius is from the centre of the sun to some edge. But what is that edge?
12
votes
3answers
111 views

What practical considerations are there for amateur observations of transiting exoplanets?

Obviously, I am not referring to actual viewing of the exoplanets themselves, but detecting their effects on the brightness of the light emitted from the parent star (as in the diagram below from The ...
2
votes
1answer
70 views

Look up current positions and velocities of solar system objects

I am working on an orbital dynamics code and, for fun, I would like to model the Sun-Earth-Moon system with my code. I can look up the masses of each object just fine, as well as average distances ...
4
votes
2answers
62 views

Is there anywhere I can find some kind of database on all known stars and their properties (mass, surface temperature, radius, and luminosity)?

I have been looking for some kind of collection of all known stars and their individual respective mass/radius/temperature/and luminosity, can you link me to one if it exists? My goal is to write an ...
1
vote
2answers
78 views

What is the orbit of Earth around the Sun?

According to wikipedia and other sources, a planet and a star always move in a circular orbit around the common center of mass of the both bodies, in case of Earth and sun, this center of mass lies ...
11
votes
1answer
157 views

Why Jupiter's Great Red Spot is Reddish?

The Great Red Spot is a persistent anticyclonic storm, 22° south of Jupiter's equator, but why is it reddish? From Wikipedia: It is not known exactly what causes the Great Red Spot's reddish ...
0
votes
2answers
57 views

How would vehicles travel through the interstellar medium with its such low density?

I've heard from a number of different places that the density in the interstellar medium can have an average of 1 atom per centimeter cubed. Perhaps I have a wrong understanding of what 'nothing' is ...
14
votes
2answers
1k views

How does neutron star collapse into black hole?

We know the spectacular explosions of supernovae, that when heavy enough, form black holes. The explosive emission of both electromagnetic radiation and massive amounts of matter is clearly observable ...
0
votes
1answer
36 views

How often and over what period is Earth’s rotation averaged to compute UT1?

I understand that UT1 (and for that matter UT0, UT2, etc.) are based on averages of actual earth rotation, and serve as a form of mean solar time. However it’s not clear to me when these averages are ...
1
vote
0answers
40 views

Data for Sun's Orbit

The planets generally kindof orbit around the sun, but a more precise statement is that the planets and the sun all orbit around a common barycenter. Because the sun is so massive, this barycenter is ...
3
votes
1answer
88 views

Accretion disks - why are they disk-shaped, rather than spherical?

So, the theory (briefly) about accretion disks is that stuff falling into the black hole will most likely not fall straight into it but will miss it and go into orbit, perhaps for a long time, perhaps ...
10
votes
4answers
128 views

Are there ways other than the collapse of a star which have been observed to form black holes?

Every time I hear about a black hole, it's always in conjunction with the collapse of a star. Have any other processes been observed to create a black hole?
12
votes
4answers
3k views

Is Jupiter made entirely out of gas?

I heard that Jupiter is made out of gas. But in school I learned that Jupiter has gravity which is 2.5 times that of Earth (Gravity that can tear apart a comet) and gravity is proportional to mass. ...
20
votes
4answers
4k views

What would happen if an ice cube is left in space?

Recently I boarded a flight and noticed Outside air temperature as -53°C at an altitude of 36860ft(11.23km). I don't know what causes such a freezing temperature in that altitude but was wondering ...
0
votes
1answer
52 views

Can an observer on Earth only see half of the sky?

Is this the following statement true? An observer on earth only may see half of sky from the northern or southern hemisphere, and even if the observer stands on the equator on top of a very high ...
14
votes
3answers
711 views

Where does the solar system end?

This is a question I've heard many times in the past, and a quick search of the site says it hasn't been asked here, so I figured I might as well ask (and answer) it. I know that it is rare for ...
1
vote
1answer
38 views

Is it possible to steer the sight of a Liquid Mirror Telescope using a plain mirror scheme? If yes, why hasn't it been done?

I have read about Liquid Mirror Telescopes in a number of places, and according to these sources, a major disadvantage of these telescopes is that they can only "see" straight up. In a nutshell, the ...
1
vote
1answer
63 views

Solar System' formation, considering its and universe's age

It's been said that the sun has 4.6 billion years, and the complete solar system to have similar age. The star-class of the sun seems to be quite common. Stars of its class can have 8 or 9 billion ...
0
votes
1answer
90 views

Does planets repel

I know gravity is resultant of mass. Gravity is nothing but the attraction force on the body resulted due to its mass. I have a question may be silly but like in magnetism we have attraction and ...
10
votes
2answers
324 views

How often do stars pass close (~1ly) to the Sun?

Interstellar exchange of massive objects is difficult across several light years. But as the stars orbit the galaxy the distances between them change. I don't find data for neighbor star distances ...
4
votes
2answers
83 views

Does Tobler's First Law of Geography Apply to Star Composition?

There is a principle in Geography called Tobler's First Law of Geography which states that "Everything is related to everything else, but near things are more related than distant things." Does this ...
2
votes
5answers
231 views

Why are stars so far apart?

So, this is mere musing, but it seems that stars are quite extremely far apart. I tried to determine the mean distance between nearest neighbors for stars (in just our galaxy) but I'm not sure what it ...
9
votes
3answers
206 views

Calculate Distance To Stars

I was just watching a lecture from Carl Sagan. He talked about figuring out the distance to the stars; it got me interested in learning more about the subject. As far as I know, the Inverse square ...
1
vote
2answers
61 views

How would an exoplanet be found from earth if our view of its star system is “from the top”?

When we find an exoplanet by observing the dimming of its parent star, this means that the planet passes in front of the star from our view. What if our view of a star system is from its "top" or ...
3
votes
2answers
84 views

How many earth-like planets do we know at this moment?

Well, the title says everything... How many earth-like planets have we discovered out there? Discard too big (made of gas), too cold, too hot, etc. Consider earth-like sun distance, size, temperature, ...
0
votes
2answers
140 views

Why don't small stars end up as a black holes?

I've recently done some research about black holes, and I realized that big stars form black holes and small ones don't. Is it because the gravity isn't strong enough for it to fall in on itself, or ...
4
votes
2answers
136 views

What would happen if we put a small part of White Dwarf or Neutron Star on Earth?

I would know what would happen if we put a small part (let me assume 1 cm$^3$) of White Dwarf or Neutron Star on ...
0
votes
1answer
51 views

where is the boundary between dark night and grey night

Is there a clear cut between them? How long and how bright will the moon be for a dark night? I googled but could not find a definition for them. People just talk about them empirically?

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