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What is the definition of a “pole” of a celestial body?

What is the definition of a "pole" of a celestial body? Earth's pole is defined as it's rotational pole. The North and South Poles are the two points on Earth where its axis of rotation ...
18 views

Moving stars in the sky

Today at 7:24 pm, I saw to stars moving parallel to each other for a few seconds in the sky. Then, both suddenly vanished. What phenomenon is this?
12 views

Question about redshift and effective gravity at the rotating neutron star surface

For a rapidly rotating neutron star, if consider the star as a sphere, redshift at the equator surface will be larger than at the pole. But if consider the star as an obsolate sphereiod (the ellipsoid ...
7 views

Why is the solar wing is most powerful near the heliosphere?

I've read this article, titled, "Voyager Mission Finds a New Type of Electron Burst at The Edge of Our Solar System". They state that, Carried to the fringes of our Solar System by the ...
14 views

Would the electron cyclotron-maser emission mechanism affect Proxima b's ability to retain an atmosphere?

In a recent arXiv preprint, Pérez-Torres et al. "Monitoring the radio emission of Proxima Centauri" claim the detection of radio emissions synchronised with the orbit of the planet Proxima b....
24 views

Do stars made by universe getting smaller or larger?

Do stars made by universe getting smaller or larger compared to stars made 180 million years after the Big Bang? If they are getting smaller, is this due to the fact that the universe is expanding and ...
9 views

Is it possible to calculate a star's apparent magnitude in another photometric band knowing its visual magnitude?

Or, in other words, is it possible to know a star's luminosity in a certain photometric band? Proxima Centauri's Wikipedia page provides the apparent magntiude in each UBVRIJHK band (getting ...
13 views

Lighting in Jupiter's “string of pearls?”

Is there any reason to think there couldn't be lightning in the storms that make up Jupiter's "string of pearls?"
8 views

Do we have an accurate breakdown of star types in globular clusters?

I became interested in the breakdown of star types in globular clusters when trying to give a good answer in a Quora question. I had a difficult time finding an answer. What I did find out was that ...
74 views

For colonization purposes, what is so good about Titan? [closed]

I have read that Titan is the best candidate for humans to colonize in our Solar System. However it has no water, it's atmosphere is not breathable and it is -290° F on the surface. It doesn't sound ...
219 views

How do we know that 2MASS J0523-1403 is a red dwarf?

I was reading about red dwarfs, and stumbled upon this article about the least massive red dwarf, and noticed several peculiarities: The spectral type is L2.5 The luminosity class is V The mass is 67....
42 views

If rotation has nothing to do with gravity, why do astronomers always links swirling dust and gas to stellar evolution?

All my life I was taught in school that we have gravity because the earth spins. Now I know that is not true. Online academics were baffled why anyone thought it. I can only say that's what they ...
261 views

What if a primordial black hole went through the Sun?

How much mass would the Sun lose to a primordial black hole that (initially) has 10 Earth masses, passing through or close to the center of the Sun at solar escape velocity? How massive would the Sun ...
77 views

Source of red in earth's photographs

What is the red in this picture of earth? At first we thought it might be pollution, but Jupiter also has red. Picture source: https://education.seattlepi.com/primary-movements-motions-earth-4701....
27 views

Is there a luminosity class for brown dwarfs?

I've been reading about brown dwarfs, and checking their spectral types, and I noticed that they do not have a luminosity class (V, VI, etc). So I am wondering, do brown dwarfs have a luminosity class,...
36 views

redshift in astrophysical plots [closed]

Why do astrophysicists often use redshift in plots? Why it is important to know how an astrophysical object evolves in function of redshift? I was seeing an "cosmological time per redshift ...
90 views

How would Earth's magnetic field change if the outer core was solid?

A widely accepted theory for how the Earth's magnetic field is generated is the dynamo theory. Dynamo theory describes how molten magma convection currents containing metal are locally spun the same ...
25 views

Naming convention for multiple star systems

Okay, so I've seen different notations for the stars in β Capricorni. Some sources state that the stars are Aa, Ab1 and Ab2, Ba, and Bb, while others say that they are Aa, Aba and Abb, Ba, and Bb. So, ...
20 views

Does a gravitational lens around a body look 3-dimensional?

Suppose we approach a neutron star or a stellar black hole close enough, is the gravitational lens around it 3-dimensional (like a tunnel) or is it 2-dimensional? It's 3-dimensional as if you entered ...
50 views

How to improve the precision in a star's distance

When I use the Gaia star catalogue, the parallax values often have large uncertainties which, therefore, leads to a large uncertainty for the distances to the stars. If you were interested in the ...
16 views

Constants of three body problem(2 fixed centers)

I was solving two fixed centers problem and got answer in quadratures. After that i want to find constants of motion. First one is full energy - E. Second is $p_{\varphi}$. And third one comes from ...
79 views

Why are telescope mirrors nearly flat?

My understanding of telescope mirrors is that they are (generally speaking) a slice out of an imaginary sphere. The center of this sphere is the focal point of the telescope, where the detector is ...
855 views

“Periapsis” or “Periastron”?

I was taught from Bate Mueller and White, that the proper terms for the closest and furthest points and distances from a body in orbit around another unspecified body are "periapsis" and &...
67 views

What are the prime challenges in search for extraterrestrial intelligence? [closed]

What have we been able to accomplish so far and what are the prime obstacles that block our sight? My understanding is that Radio Telescopes are the prime tool for the search. I wonder what kind of ...
63 views

Accuracy of the Inflation theory

In the Inflation theory, it said that the Inflationary epoch has happened $10^{-32} \,\mathrm{s}$ after the Big Bang, and I cannot find anything related to how this number was calculated and how ...
50 views

If the Earth circled a red dwarf/giant or a brown dwarf, would its sky still look blue? [duplicate]

I have the impression that in brown dwarf and weak red dwarf systems, everything looks more reddish on a planet, including its atmosphere regardless of composition. Suppose there's a planet having an ...
84 views

Was there ever a meteorite with a measurable gravity?

Did we ever find a meteorite (a meteoroid that has fallen down to Earth) whose mass, density and gravity were high enough to demonstrate their gravity similar to the Cavendish experiment, so that ...
29 views

Hypothetical CMB space telescope design problem, received power from extended thermal source versus receiver front end NEP?

Consider the example of a large radio dish antenna in space equipped with a heat shield protecting it from the Sun. Let's say the amplifiers front-end effective temperature (for purposes of noise ...
35 views

What does the “a” at the end of a spectral type mean?

Looking at the chart for spectral type peculiarities (here), I noticed that the letter a was missing from the chart. This seems to be an error, as the star Vega has spectral type A0Va, with the a ...
46 views

Blackbody curve in RGB for objects less than 1500 K?

We know the colors of stars that have a temperature greater than 1000-1500 K, shown here. However, I am wondering about those stars/brown dwarfs with surface temperatures of less than 1500 K. Is there ...
457 views

When making an observation using a radio telescope, is it possible to filter out noise coming out from a known source by using another telescope that will focus on that noise source? By filtering, I ...
52 views

“LinAlgError: SVD did not converge in Linear Least Squares” with eleanor.py

I'm doing some tests with eleanor module (i'm a novice). I'm using the example code written on eleanor.py website ...
9k views

Do our sun and moon have names?

We seem to have named every moon orbiting other planets. Why haven't we named our own moon? And for that matter, why doesn't our sun have a name since we name or number stars?
42 views

What was there before the big bang [duplicate]

we know that our universe is expanding, but we must agree to the fact that it has a limit. It just cant expand till infinity. Eventually there will be a end to time. I thought alot about this and i ...
14 views

How to I calcuate observed position of the Sun and Moon using the SOFA C library?

There are a number of answers on here that skirt the topic, but no concrete answers. I currently have an implementation based on "Astronomical Algorithms by Jean Meeus" for stars, moon, and ...
42 views

Centre of the Universe [duplicate]

Why shouldn't the original singularity of the big bang happen to be the centre of the Universe? Assume that the universe is expanding isotropically with a constant speed.
55 views

How does a planet-sized robot standing on a planet affect its gravity?

I originally asked this at the sci-fi exchange but was told it was off-topic as it was about real-world science. Here is a picture of Unicron standing on top of the planet Cybertron, as written by ...
67 views

Callisto's orbit: circular vs JPL is periodic 4 degree error, why?

I am approximating the azimuthal angle of Callisto from Jupiter or the Jupiter+moons barycenter using a constant angular speed circular orbit. This differs from the JPL ephemerides by only about 4 ...
474 views

After what time interval do the closest approaches of Mercury to the Earth repeat?

The sidereal period of Mercury's revolution is 88 days and the synodic period — 116d. my solution, but in the question featured "the greatest rapprochement." And this is no longer so easy. ...
73 views

Could blackholes warping space-time create dark energy?

I think the effects of blackholes on the surrounding space is localised to a small area around the blackhole but I wondered if the largest blackholes at the centre of massive clusters could be a ...
24 views

Do Roche limits apply to Kerr ring black holes? [duplicate]

I was wondering if a smaller black hole orbiting a larger one could be torn apart by the Roche limit or tidal force or other, if the center of the blackhole was not a singularity but a Kerr ring of ...
81 views

Do neutron stars have an ergosphere?

Ergospheres are a property of black holes, and do neutron stars have it? If yes, why seldom article mentions that; if no, why can't neutron stars have this ergosphere component?
29 views

Formation mechanism of a non-barred 6-arm spiral galaxy

UGC 12588 has an unusual morphology of an old dwarf spheroidal with six very young spiral arms. None of the 24 Simbad references describe its morphology or recent history from the galactic assembly ...
72 views

Why does a right-handed circular polarized wave get lagged when going through ionized plasma?

I have a question related to Faraday rotation. In Abigail Polin's Faraday rotation video I have seen that a linearly polarized wave can be decomposed in a left-handed circular wave and a right-handed ...
30 views

Are Dwarf Galaxies a Subset of Galaxies?

The question is a rather obvious one. In normal English a word like "dwarf" used as an adjective is assumed to modify the following word. Thus a "dwarf galaxy" would be assumed to ...
101 views

What happens if the Moon moves twice as fast?

If the Moon would rotate around the Earth with double its current speed. What would happen then? Would it get further from the Earth or it would be possible to keep its distance from Earth?
61 views

Do planets have effect on velocity of Earth?

There is method for finding extrasolar planets called Transit-timing variation. If I understood correctly, exoplanets accelerate or decelerate each other (according on their position), so we can ...
19 views

Where can I find galaxy spectra (in the form of FITS files)?

I know there's SDSS and I tried searching for the spectra through the navigate and explore tool under CAS as well as by using RA/Dec coordinates under SAS, but every single time it comes out with 0 ...