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 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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Why can't dark matter lose energy by gravitational waves and collapse into itself?

Because of lack of electromagnetic induction, dark matter can't lose its gravitational potential energy. That is preventing it from collapsing like an ordinary matter cloud in space. But why can't ...
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How can we calculate solar and lunar longitude in java?

I want to develop panchangam logically. So, I want to find solar longitude and lunar longitude. Could you please help me to find the solar and lunar longitudes in java or any mathematical formula for ...
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Why is the Sun the centre if relativity is true? [duplicate]

I thought a bit about this, and got confused as to why we always claim the Sun is at the centre of the solar system since relativity tells us that there is no preferred frame of reference. A person ...
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What is the meaning of size in celestial bodies?

I read about a star collapsed to a size of 12 km. Does the size mean that the new radius is 12 km or the diameter of the star
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Apsidal precession

There is the formula: $$ \Delta\theta=-2\frac{\partial}{\partial p_{\theta}}\left[\int_{r_{min}}^{r_{max}}\sqrt{2\mu\left(E-V_{eff}\right)}dr\right] $$ That indicates the change in angle for the ...
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Lane-Emden. Quasi-linearization method

ow to prove this theorem? I have a doubt. Theroem: Suppose that $w(x,\alpha)$ solved $\ddot{w}+\frac{2}{x}\dot{w}+\alpha^{2}w=0$ with $w(0)=1$, $\dot{w}(0)=0$, $w(1)=0$. Then $v(x,\alpha) := \omega w(...
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Has any result of Hubble parameter been obtained by observing SN UDS10Wil?

I am simply asking the question after reading Wikipedia because I am confused about the historical change of the parameter during the cosmic inflation. Knowing that as far a supernova is the more in ...
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What light pollution levels are required to see the Milky Way?

I live in a Class-5 night sky on the Bortle Scale, and you cannot see the Milky Way with your naked eye here. I was wondering what Class night sky I would have to be in to see the Milky Way's gas and ...
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How can I know the source size using the spectrum variability?

When reading some astrophysical papers I saw things like this: "The sources are variable on very short timescales, implying a compact emission region" How can we conclude or measure the ...
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Displaced spectral lines of a star

Why do we see the lines in a star spectra displaced from the wavelength they belong to and so we need to calibrate the spectra ? Is it only because the relative motion of star and earth ?
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Interpretation of optical depth of photon travelling from stellar interior to surface of star

My lecture notes state: We define the optical depth as: $$\tau_{\lambda}=\int_0^s\kappa_{\lambda}\rho ds$$ In the case of a photon travelling from the stellar interior to the surface, $s = 0$ at the ...
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Expression for a Distance in Ptolemaic Epicycles

I'm studying the geocentric Ptolemaic model of an upper Planet. My goal is an expression of the (squared) distance of $h$ from the planet to Earth, depending on the angle $\beta$. Let me explain you ...
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To measure its absolute rotation, wheel rotation stopped while oriented North-South and then orientation just changed to East-West

If there is no influence of Earth rotation on a highly balanced wheel positioned freely to rotate with no friction on a firm construction and perpendicular to the ground and while changing its ...
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What is the meaning of “current” CMB rest frame or the CMB rest frame at redshift $z$?

As I know that the definition of the CMB rest frame is the comoving frame of the plasma emitting CMB. And the anisotropy of CMB is due to the velocity difference between the earth frame and the CMB ...
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Is the compass direction of a planet recorded by two different observers separated by some distance the same?

I have a basic doubt. Say I am viewing Mars from my window and I used the compass app to get an approximate 2D direction. If at the same instant another person also observes Mars from their window. ...
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Tilting of Earth rotational axis

In which way do the Earth's rotational axis tilted 23.5°. see in the image we have been told that the axis of rotation of Earth is tilted 23.5° from the perpendicular to path. But can anyone say in ...
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Tidal locking and heat dissipation

I need to know that how does one measure (approximate) the energy loss of a planet or satellite during the whole tidal locking process? Where do I find this topic to study?
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Is it possible to prove or disprove the Einstein Synchronization Convention with astronomy?

So, I just saw this Youtube video by Veritasium that discusses how it's impossible to measure the one-way speed of light from a light source to a detector, since it's impossible to synchronize clocks ...
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How to calculate Night Flight time during a flight? [closed]

I am currently working on a web app (Pilot Logbook) that requires a user to automatically calculate the period of flight spent in the night. Currently, I have Departure Lat and Long and Departure ...
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Why is it that Mercury is considered a planet, Pluto was once considered a planet, but Callisto is not considered a planet? [closed]

Mercury is 15 329 km in circumference. Pluto is 7 232 km in circumference. Callisto is 15 144 km in circumference. So why is it that Mercury is considered a planet and Pluto was once considered a ...
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Where can I find the live Earth-Sun-Mars angle*, assuming that both planets are in coplanar orbits?

*The angle between the line from the earth to the sun and the line from the mars to the sun RIGHT NOW. I only found the right ascention and declination of Mars, which is measured with respect to Earth....
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Textbooks on cosmology *after* recombination

I am a theoretical physicist and I have a reasonable understanding of the early universe, inflation, FLRW metric, leptogenesis, baryogenesis, perturbations, the works (mainly in the style of the ...
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If the Sun's temperature is around 5000K to 6000K which means it is a yellow star, why does it appear white in space? [duplicate]

If the thermal radiation of stars is close to the thermal radiation of a black body the sun should appear yellow but yet it appears white because of emitting all of visible wavelengths which combine ...
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Time and position accuracy requirements for the Event Horizon telescope

The black hole at the center of M87 imaged last year by the Event Horizon Telescope, using Very Long Baseline Interferometry, at Earth subtends an angle of about 20 microseconds of arc. This happens ...
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Is there a GR solution for the geocentric system?

It is possible to get the Schwartzschild metric assuming spherical symmetry, vacuum solution and Minkowski spacetime when $r \to \infty$. Is it possible an analytic solution for a geocentric system? I ...
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Which volatile ices are hardest below 100 K?

In the context of planetary science, some elements and compounds are informally called volatile instead of refractory, such as H2O, HCN, CO2, NH3, HCHO, CH4, CO, N2. At conditions found near planetary ...
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Calculating apparent density of stars in sky, given an area and distance away from my viewpoint

According to this source, there are $5077$ visible stars in the night sky, and a full sky area of $41253$ square degrees of sky. This makes for a density of $0.12$ stars per square degree of the sky. ...
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Measuring Sun and Moon distances to the Earth ratio just by observing angles of elevation if upper 50 percent of Moon's surface is bright?

When the next type of calculation was possibly used for the first time? If 50% i.e. upper half of Moon were bright would the Sun-Earth to Moon-Earth distances ratio be calculated from just ...
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Voyager distance

This very nice NASA page continuously updates Voyager 1 & 2 distance away. How is that distance calculated/determined?
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How can an object (meteroid, vehicle) bounce off the atmosphere?

Recently, a meteroid bounced off the Earth's atmosphere. IIRC vehicles such as the returning Apollo craft also had the risk of bouncing unless they came in at a precise angle. How is this possible? ...
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Why does the solar corona appear white?

Look at this photo taken in France during the 1999 solar eclipse which I found on Wikipedia. Why does the corona appear white? It has a temperature of about $10^6\,$K so you would think that it would ...
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Do bolometers measure all posible wavelengths of EM radiation? Is this even possible?

What is the closest thing we have to a 'black-body' bolometer? What are the best absorptive bolometers made of?
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Jupiter-sized planet orbiting a white dwarf?

I read this news about a Jupiter sized planet orbiting a white dwarf. It is still puzzling to the scientists that how it remained as a single piece. NOTE: I went through the Astro.SE link given in ...
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How far away were galaxies when they emitted the light we now see?

If we had a way to measure the apparent distance to 13billion light year galaxies (parallax or something) what would it be? The light left the source 13 billion years ago, so it would appear much ...
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Does the Hubble constant measured for huge distances mean it is not the actual Hubble constant but a very old one?

I am citing Wikipedia about Hubble constant.... "Hubble constant is most frequently quoted in (km/s)/Mpc, thus giving the speed in km/s of a galaxy 1 megaparsec (3.09×1019 km) away, and its value ...
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Just something I was thinking related to light travelling

Since we know that when we watch a star, we are watching it in a state it was before when the light started travelling from it. So suppose, I travel from Earth to a distance of 1 light year and than ...
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Derivation of Mattig's Formula

Mattig's formula for any k: How to derive this equation without using General Relativity?

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