Questions tagged [astronomy]

The science dealing with objects and phenomena located beyond Earth. In particular, this applies to observations and data. At its core, astronomy is the physically informed cataloging and classifying of the contents of the universe in order to better understand what is out there.

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Proving nearby planets are not antimatter [duplicate]

Observations of the universe make us think matter is much more common than antimatter, and I believe no "probably-antimatter planets" have been found. But, if Pluto, for example, somehow ...
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State of the art on relativistic perihelia precession in Solar System (other than Mercury)

The correct prediction of anomalous precession rate of Mercury perihelion is a classical test of General Relativity and one of its' big triumphs. How about other planets in the Solar System? ...
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Four Momentum in an Isotropic and Homogeneous Universe

We define the four-momentum of a particle by $p^\mu = (E, \mathbf{p})$, where $E$ is energy and $\mathbf{p}$ the three momentum of the particle. In cosmology, we conventionally use the Friedmann-...
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Is Earth’s rotation slowing down or speeding up?

Section ‘Slowing down of the Earth’ of the Wikipedia article Leap second has the following paragraphs: A mathematical model of the variations in the length of the solar day was developed by F. R. ...
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Is a pulsar EM-radiation affected by diffraction?

Is a pulsar EM-radiation affected by diffraction? As I understand gaussean beam theory there should exist different diffraction or if You want diffusion angles for different wavelengths, for example ...
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What is the meaning of grain opacity and why does it affect the formation time of gas giants?

While doing research for my presentation on the formation of gas giants, more specifically the "core-accretion model", I have been stumbling across the term "grain opacity" and don'...
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Uncertainty in data from star databases

I have students who are pulling data from various astronomical databases like SIMBAD or the Binary Star Database and then using that data to determine correlations between certain properties. My ...
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“Weak” and “strong” spectral lines

Can some one please explain what the following excerpt from Priest's MHD of the sun means: The lowest is an extremely thin layer of plasma only several hundred kilometers thick, called the ...
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Why sun rays are parallel not of stars?

I have studied that when a light enters from space into earth atmosphere it experience atmospheric refraction many time due to different atmospheric layer. Then why we take sun rays parallel? They ...
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Angular momentum orientation of the orbits of the two stars with respect to the Solar System

Happen to see this in Wiki... The astronomer Karl Schwarzschild observed the motion of pairs of stars orbiting each other. He found that the two orbits of the stars of such a system lie in a plane, ...
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In a 2-dimensional sense, how do the perihelions of the planets in our solar system line up?

A bit of background, I'm currently making a 2d graphical representation of the planets orbits around the sun with Python for a university project which currently looks like the picture below (not ...
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How can spectroscopy be used to find the composition of exoplanet atmospheres?

How can astronomers use light spectroscopy to measure the composition of different planets when they can't directly image the planet because the star that they are orbiting is so much bigger and ...
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Is our solar system really that odd?

I have been learning about the solar system from popular science shows. In these shows they suggest that, after having seeing around 2500 other solar systems, astronomers have concluded that our ...
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Number of stars in Ambartsumian's Knot NGC 3561 Galaxy

Is there any data on what kind of stars and how many are in Ambartsumian's Knot dwarf Galaxy? Is there a database to refer to? Thanks in advance
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Difference of sunset time per minute by altitude?

For what difference of altitude needed for the sunset time to differ by a minute? How to calculate that?
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Econometrics and Astrophysics: can you help me on light curve analysis here?

Well, I'm trying to find computational algorithms to analyse light curves of quasars. My advisor suggested things like, neural networks, ARIMA algorithm, genetic algorithms and so on. But the question ...
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How can I obtain the equation of state (EOS) of dense neutron star matter?

I am recently studying the equations of state of the neutron star. In the following paper,there are some tables and figs about energy density and pressure (I have attached tables 3 and fig 1 of the ...
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How are cosmology and astronomy fields of science? [closed]

If a scientific field is defined as one that follows the scientific method, then it needs to have reproducible experiments. But this is not possible in cosmology and astronomy, because how can one ...
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Equations of state for white dwarf stars

I am dealing with some model describing the given composition of a white dwarf made with photons, degenerate electrons, positrons and ions. From that, I can get tabulated values of densities ranging ...
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Did we adapt to Earth or Earth to us? [closed]

I often hear that Earth is a unique planet because it has life and it has its own inhabitance. We also see a proper balance between plants and humans and other animals. Why life is not possible on ...
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How bright are Earth's VHF transmissions compared to our sun?

The Sun is a black (ish) body, so it must be emitting all of the kinds of radiation below visible, right into the VHF. But how much VHF radiation is there, and how does it compare to the artificial ...
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Island of Stability in Astronomical Surveys

To the segment of nuclear physicists that predict that there is indeed an “Island of Stability” in super-heavy transuranic elements, where these atoms shouldn’t suffer the effects of radioactive ...
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How can the mass of the sun be determined without using Kepler's law or gravitational lensing?

Can the mass of the sun be determined using the abundance of elements or alternative methods? It would be better to ask the question like this if we assume that I have an object that contains baryonic ...
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How bright would the surface of each planet be?

At night when there is no moon in the sky, it is dark, you can not see your surroundings. If I were to stand on Pluto, could I see my surroundings? Would being on pluto at day be like night on earth ...
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If a very distant supernova has a high Doppler effect redshift do our eyes see its evolution picture like in 'slow motion'?

If a very distant supernova has a high Doppler effect redshift do our eyes see its evolution picture like in 'slow motion'? If a same type of supernova apparently lasts longer if it has more ...
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Extreme Redshift Detection

There is a new paper in arXiv postulating that black holes might actually let some let some light out. This of course is very theoretical, but it postulates that the light would be redshifted to 640 ...
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Steady state model prediction of number of radiogalaxies as a function of time

What does the Steady State model predict about the number of radiogalaxies per unit volume as a function of time? How to derive an expression for the differential number counts dN/dS and the integral ...
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How can cosmologists distinguish between CMB variations caused by dark matter and those created by baryonic matter?

Charlie Wood, "How Ancient Light Reveals the Universe's Contents", Abstractions Blog, Quanta Magazine, January 28, 2020, https://www.quantamagazine.org/how-the-cosmic-microwave-background-...
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Fermi Paradox and SETI statistics: are best candidate signals actually from ETI?

A possible answer to the Fermi Paradox is that SETI efforts have, in fact, intercepted radio transmissions from extraterrestrial civilizations, among the “strong candidate” signals: Suppose that, in ...
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Terminology: “3σ detection over the continuum”

I am reading a research paper and they use the expression: "This is a weak signal, i.e. 3-4σ detection over the continuum". I saw this sentence in a lot of papers, but I can not find what ...
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Where can I find the true anomaly of the planets on Jan 1st 2000?

I am trying to code a simulation of the solar system. At present, all the orbits seem correct but I'm placing the planets at their respective periapses at the start of the simulation so the relative ...
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How can I plot Rotation Curves of Spiral Galaxies $v$ (km/s) vs $r$ (kly)?

I have a formula about Rotation Curves of Spiral Galaxies that I have written below: $$v(r)=c [L/(2*r)+1/2\cdot c_3+ c_4\cdot\ln(r)]^{1/2}$$ that $c=3\cdot10^8m/s$ is the speed of light and $c_3=2.8\...
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Distance as a function of time in the case of an increasing Hubble value

I am trying to deduce the traveled distance of, e.g. a galaxy, as a function over time $D(t)$ in scenarios in which the Hubble value stays fixed or increases proportionally with time. For the fixed ...
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Temperature of Closed Universe in future

This is a question from "Introduction to Modern Cosmology" by Andrew Liddle: Suppose we live in a closed universe(k > 0), which will recollapse some time in the future. What will the ...
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Doubt regarding solving an integration for radial flow of matter around a star in Newtonian gravity

The spherically symmetric flow of matter around a star in Newtonian gravity is governed by the equation $$v\frac{dv}{dr}+\frac{1}{P+\rho}\frac{dp}{dr}+\frac{1}{r^2}=0$$ The equation of state is chosen ...
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How does a proper motion displacement of $x$ arcseconds/year mean a star is moving at $x$ AU/year?

I trying to understand the author's answer to this question: I don't understand the part underlined red. How does 3.6pc mean 3.6AU? It says a "distance of 3.6AU", but doesn't say what is ...
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Is the dark night sky paradox (Olber's paradox) really a paradox if we count with simple astronomical observations?

So, I came recently to watch this video, which explains Olber's paradox and how it was solved with the big bang theory, doppler shift etc. My question can be split into a more physical question and a ...
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Why a decaying dark matter?

I'm reading some papers (model, exp and model) that are dealing with decaying models of DM, why is it interesting? What are the signatures that this type of model can give to observe DM? I am ...
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Cosmological redshift due to recession speed or expansion of space?

I am somewhat confused regarding the factors that cause cosmological redshift. This wiki states that the amound of cosmological redshift coming from let’s say, a star, is calculated by $$z=\frac{H_0 D}...
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Infrared Telescopes and Surface Area

I have been reading a paper on about exoplanets, specifically measuring the temperature of exoplanets using infrared telescopes. The paper compares exoplanets with neutron stars (NS) remarking that ...
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How to track orbit of an exoplanet?

I was wondering if there is an established method to keep track of the orbit of an exoplanet assuming we know $a$ - the semi-major axis of the orbit, $e$ - the eccentricity of the orbit, and $i$ - the ...
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Expressions for emitted and incident flux of a star confusion

The physical flux is the total energy flowing across the unit area from all directions: We can write flux as a function of intensity as follows: $$F = \int_0^{2\pi}\!\!\! \int_0^{\pi} I \cos(\theta) \...
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Computational Astrophysics and Time Series analysis: I really do not know how to manage this problem

So, I have a table of data which contains information about time $t$ of observation $(x-axis)$ and energy flux in Jansky unity $\mathrm{Jy}$ $(y-axis)$. The table of data concerns on observations in $...
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Building a radio telescope!

So, I saw recently the idea of a radio telescope and thought how simple they are. So, like any other normal human being, I went on google and searched "how to make a radio telescope" and ...
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Ray Diagrams: Where is the eyepiece located in a reflector telescope?

I'm in the process of building my own reflector telescope; I have an 8" primary mirror with a focal length of 1200mm. Of course a telescope has a focuser that lets the eyepiece move up and down ...
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Why does Grand Solar Minimum occurs?

Recently I was reading about the Little Ice age that happened in 13th to 19th century that caused mild summer and bitter winters ( also known as Grand Solar Minimum (GSM ). How did this occured?
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Negative mass density in cosmology?

I came across a problem in Chapter 6 of An Introduction to Modern Cosmology by Andrew Liddle that reads: Identify a sufficient and necessary condition that must be satisfied by the equation of state ...
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Is there a modern accurate formula for the length of the sidereal year?

Newcomb (1898) gives the following formula for calculating the tropical year: $$365.24219879 - 0.00000614T$$ And the following for calculating the sidereal year: $$365.25636042 + 0.00000011T$$ Where T ...
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How do we know the distance between stars (without assuming flat spacetime)?

In this video, Nick Lucid (an astrophysicist) says we believe spacetime is globally flat because when we form a triangle between Earth and two distant stars, the angles of the triangle always add up ...
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What sort of observations constrain the QCD interactions of dark matter?

Within our current limits of observation, dark matter (DM) is nonluminous i.e., it neither absorbs nor gives off electromagnetic (EM) radiation. This tells that DM is electrically neutral having no EM ...

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