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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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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Equation of states for white dwarves

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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4answers
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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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What cause protostar to become optically thick?

So far I get that the cloud will contain CO and will reacts with photons which cools the core but at some point the clouds becomes optically thick and allows the core to heat up. What causes the core ...
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Constant Internal energy of universe and its original source [duplicate]

While I was studying thermodynamics I am confused about internal energy of universe. here a question confused me. "If the internal energy of the universe is constant then where did all energy ...
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Will a satellite orbiting the moon have a tidal locked orbit?

Suppose an artificial satellite is launched to orbit the moon. Ignore 3-body problem issues, just assume it follows a roughly titled elliptical orbit relative to the plane cutting through earth's ...
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How to calculate the brightness of an object in space dependent on its distance from earth?

If a comet appears increasingly brighter as it approaches the earth, how many times brighter will it appear as it moves from $25AU$ to $5AU$ from us?
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Why is astronomy intensity interferometry immune to atmospheric turbulence?

I have read there is renewed interest in intensity interferometry in astronomy. I read that intensity interferometry is immune to atmospheric turbulence, which plagues astronomy and regular (amplitude)...
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Should it be classified as intrinsic or extrinsic variable star if the brightness of the star changes due to the expansion of the universe?

The Wikipedia article on Variable stars says the following: Variable stars may be either intrinsic or extrinsic. Intrinsic variable stars: stars where the variability is being caused by changes in ...
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Dimensional analysis on absolute magnitude of a star

Absolute magnitude $M$ of a star is $$M = m-5\log \Big(\frac{d}{10}\Big)$$ where $d$ is measured in $parsec$ but this raises couple of problems. $M$ and $m$ are dimensionless quantities but $d$ is in $...
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Astrophysicists and Astronomers

What's the difference between an astrophysicist and an astronomer? Do these two disciplines intertwine or are they the same since they're so synonymous with one another?
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What is the theoretical limit for image sensors

Telescopes are principaly limited by a diffraction-limit. Does this limit affect the image sensor? The Rubin Observatory LSST Camera, the biggest camera in the world with 3.2 gigapixels is having a ...
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How are the locations of solar system planets expressed in their orbits?

and where can I find the data about the locations of the solar system planets during their entire year? I would like to find the data on the orbits of solar system plantes. Also I would like to know ...
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Deriving the first moment of Collisionless Boltzmann Equation in Spherical Polar Coordinates

I am following these notes: Dynamics and Astrophysics of Galaxies. After equation 6.37, we have: \begin{equation*} p_r\,\frac{\partial f}{\partial r} + \frac{p_\theta}{r^2}\,\frac{\partial f}{\...
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I don't understand why my graph of the variance of the Sun's true noon is so bumpy

I understand that the true noon, defined as the sun reaching its highest point in the sky, varies from the noon we have on our clocks. I understand the impact that the eliptic orbit has on the speed ...
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Research on exoplanets using available data from TESS

I am a high school student who is proposing research on exoplanets for my junior research project, I have several questions: I have seen studies where researchers survey star systems and then find ...
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How to not change the shape of the orbit of a planet while increasing or decreasing the size(perimeter) of the orbit?

I want to know if I can fast forward planetary movement by putting a planet closer to its star so that the planet can move faster but the shape of its orbit remains the same?
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Statistical argument for n/p ratio in relativistic neutrino environment?

Consider a system with high-energy neutrinos (higher than rest mass energies of protons & neutrons) where the energy of a neutrino is specified as $E = p + sB$, $p$ being the magnitude of the ...
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Proxima Centauri radio signal

I have recently seen an article about an unusual radio signal coming from Proxima Centauri region. I understand there is a debate around the nature of this signal. My question is related to this ...

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