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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1answer
69 views

Would a parallax measurement of distance to a star be affected by relativistic length contraction?

Let's say you had 2 ships launched 1 light year apart towards a star 10 ly away and they were equidistant from the star moving at .6c towards it. Would their velocity cause their parallax distance ...
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Why couldn’t dark matter be from advanced technologies? [closed]

(Coming from a layman) Why couldn’t dark matter be the consequence of advanced technology? For many reasons I can imagine that the game theory for intelligent life is to eventually hide/ camouflage ...
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Are night and day lengths over a year equal everywhere on earth?

(Question from math.stackexchange, because people told me to better ask here: Original link) As you all know, in winter the nights are longer and there is nearly no sun, but in the summer there are ...
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Time of explosion of progenitor from galxy expansion rate [closed]

An expanding supernova remnant (SNR) with angular size 120 arcmin (1 degree equal to 60 arcmin.) was discovered in our Galaxy. If the remnant is at 12000 ly (light year) from us with a constant ...
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Lunar surface brightness

If the Moon is visible against a clear blue sky with a lux value of around 30,000 does it stand to reason that the lunar surface must be brighter than that?
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What is spectral redshift resolution of observationally detected damped Lyman Alpha clouds?

What is the spectral resolution, $\Delta z,$ when detecting damped Lyman alpha systems at different epochs, $z \sim 0-3,$ through current and/or future observational instruments? And is this redshift ...
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Shadows cast by Venus

How and why would a shadow on earth cast by Venus differ from one cast by the Sun or Moon? My thinking is that the shadow would be much fainter because less light is being blocked. Also, I think it ...
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On the derivation of the north-south aberration angle

In A.P. French's Special relativity, page $39$, the author said the north-south aberration angle $\alpha$ below, in figure (b), is equal to $v\sin(\theta_{0})/{c}$, where $\theta_{0}$ is the angle ...
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What does. DM- nu, sigma = 10^-33 m_DM GeV^-1 cm^2. mean?

I tried posting a screenshot above...... On Ethan Siegel's blog over at Forbes, he has repeatedly posted a graphic showing possible 'new physics' that could explain why the Planck satellite ...
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A star or a galaxy?

When we look into the beautiful sky in the night, exclaiming how beautiful these shining stars are. My question is how could we tell, whether any of these shining "point" is a star or a galaxy? If ...
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HD 140283 and the age of universe

I am watching a video on a star that is supposedly older than the universe. HD140283 (Methuselah). According to the first 20 years of research on the star, scientists believed the star is just over ...
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Measuring lowest photon energy

If I wanted to buy a receiver that measures the energy of incoming photons, what is, not theoretically, nowadays the lowest energy that can be measured (in joule)?
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Why is the moon so bright when it is really dark

The moon is bright, and if you were 50 times closer it would be 25 degrees across with the same surface brightness, which would be pretty dazzling. Looking at the moon through a telescope (which ...
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Does the length of days change substantially during the year, from more than 24 hours to less?

I just read an article in the 'Science' journal online about Monarch butterfly migration. (Mysterious monarch migrations may be triggered by the angle of the Sun , by Elizabeth Pennisi , Dec. 18, ...
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Are there any patterns in the locations of pulsars in our universe?

Are there any particular places pulsars are distributed? If so, why? Any information to links and articles will also be appreciated. I just want to understand more about pulsars and if there are any ...
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What is the relationship between average pulsar amplitude and the frequency?

Hi my question is pretty much in the title when im referring to frequency im referring to the frequency of the pulses. I have plotted a graph frequency vs average pulse amplitude but i don't ...
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How to find the transverse component of a stars velocity given it's proper motion and distance from the observation point?

If $\mu$ is the proper motion of a star in arcseconds per year, and $d$ is the star’s distance from us, then the transverse speed, $v_t$ will be $$v_t=d\sin\mu$$ For small motions (assumed for ...
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Lisa Pathfinder Mission - interpretation of results (frequency)

In the results of the space mission Lisa Pathfinder is on the xx axis the frequency value. Where does this frequency come from? Does it come from satellite orbit frequency or mass vibration?
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How to explore astrophysical fluid dynamics?

I'm a second year aerospace engineering undergrad student. I'm currently part of a project dealing with boundary layer flows on supersonic flights, and I find it to be really interesting. I wish to ...
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Black Body radiation units in CGS

As all of us know the equation of black body is $$B_\nu = \frac{2 h v^3}{c^2} \times (\exp(h\nu/K_BT) - 1 ) ^{-1}$$ I know the following units $[h]$ = erg $\cdot$ sec, $[\nu]$ = Hz and $[c]$ = cm/s. ...
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Can we look further than the CMB?

As I understood it, the map of the cosmic microwave background (CMB) corresponds to the time when photons decoupled from matter, making the universe transparent. In this sense, we might expect the CMB ...
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How far can we look into space?

Ho distant can we look into space by using a telescope? With "telescope" I mean here any device able to detect photons of any wavelength. In terms of distance, is it correct to sat that observing the ...
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Interstellar Debris

Do radio astronomers not have solid data on just how dense and widely distributed solid interstellar debris is? I cannot seem to find any direct answer on this subject from any source. I am interested ...
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What is the relationship between a pulsars period and the frequency? [closed]

If I measured the period at several of frequencies for a pulsar using a radio telescope what relationship should i see?
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body vs electron spaghettification

What would cause an extended object (like a person) to be subjected to “spaghettification” when falling into a black hole, even though that would not happen to a point object (like an electron)?
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Gravothermal catastrophe, how to understand it?

I would like to study the phenomenon of gravothermal catastrophe. Could you suggest some papers or books about it and the books I should check for prerequisites (astrodynamics, statistical mechanics, ...
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Finding how much time it takes for a complete Earth revolution around the Sun

Long story short, my brother made a joke about how stupid it is to celebrate the Earth making one "trip" around the Sun: New Year's Eve. So I got curious and was wondering: how could the first ...
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Importance of high order separation in Echelle spectrometers?

I've been reading on the subject and constantly find that in astronomy Echelle spectrometers are used. I've also found that greater order separation favors long slit spectroscopy. Why is this?
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Solar panel and Equinox

At Equinox the number of hours of daylight and night is equal so 12 hours of each... is this from 6am to 6pm? how can we know which hours this daylight happens for. The question is: Over which ...
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Derivative of mean anomaly w.r.t true anomaly

I am trying to work through the workings in this paper. At one point (Eq. 10) the authors define the usual mean anomaly, $\beta$, the true anomaly, $\psi$, and the eccentric anomaly $u$ in the usual ...
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3answers
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Will August be always summer in the northern hemisphere?

Is the Earth orbit precessing, or are there other effects which will create a shift between our calendar (day counting), and the Earth's orbit? I imagine these effects to be small, but I'm asking for ...
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How does the speed of light affect our cosmic observations/detections?

-I learned that if you look at a star 10 million lightyears away, the light that you are looking at is 10 million years old since the photons have been traveling at the speed of light for 10 million ...
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How to measure the distance of an object using standard candles?

Standard Candle techniques can only be used to determine the exact distance from Earth to another standard candle, right? I mean, imagine I want to know the distance to a star A in galaxy $\alpha$. ...
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Nobel Prize in Physics 2019 on exoplanets and Hot Jupiters

The 51 Pegasi b, discovered by Didier Queloz and Michel Mayor is classified as a hot Jupiter and not considered to be a star. I had read a bit about the minimum mass necessary for being a brown dwarf ...
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If there is no gravity on the moon does the flag wave? [closed]

We are doing a debate in astronomy and I was wondering if there is any gravity on the moon that would cause the American flag on the moon to wave at all.
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Converting coordinates from celestial reference frame to terrestrial reference frame

I was working on how to transform celestial reference frame (Right Ascension and Declination) of a particular quasar at J2000.0 to terrestrial reference frame at the epoch of October 22 2019 (00:00 ...
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Solid angles in integral?

Could somebody explain why we have to integrate over the solid angle when calculating total luminosity in the following: The integral over the wavelength makes sense, that a=way we have a total power ...
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How scientists look for anti-matter?

If matter and anti-matter look exactly the same, then how can scientists look for anti matter from a distance (other galaxies)?
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Right Ascension for epoch 2000 - physical location?

I understand that Right Ascension is a longitude-like celestial coordinate that varies from 0-24hrs, taken from a reference point of the vernal equinox. More specifically, for star maps that are based ...
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How to get the Tycho Brahes Mars Declination data's equivalent modern calculation

I know quite little about physics, much less astronomy but I am very interested in the data in the red line in the below GIF : http://www.pafko.com/tycho/observe.html from this site. I tried ...
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Why is the sky near the Earth limb warm-colored, even far from the sun?

I've seen many sunset pictures with explanations. The sun is red, the areas adjacent to it is orange, then yellow... because redder lights bend less, and the air is thick at that angle. Far enough ...
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A thought experiment related to the age of the universe

Okay, So, this thought experiment starts with the movie, Interstellar. In which humans went through a wormhole to a system consisting of a Black Hole. They landed on a planet (I don't remember its ...
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Why does the shadow of Io on Jupiter look so big?

It has been reported this week[0] that the following image by Kevin Gill is the shadow of Io crossing Jupiter. Why is the shadow so large? My intuition is that Io is much smaller than Jupiter so ...
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AGN accretion disk double peak explained?

I have a question to the following lecture: https://ned.ipac.caltech.edu/level5/Fabian4/Fab2_2.html In Figure 3 it says that a narrow annuli of a Newtonian disk should alrdy show a double peak ...
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How do astronomers measure the mass of a planet using Doppler spectroscopy?

So, I am making an essay explaining planet-hunting techniques. And while I do get how astronomers measure the semi-major axis of a planetary orbit (using Kepler Laws), I don't get how they measure the ...
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Does the curvature of light around a “centre star” in gravitational lensing affect the age at which we view the object being “lensed”

It occurred to me that during gravitational lensing, the light curves around a given object, creating a curved path. Because the path of light is curved, and thus, longer than a straight path, would ...
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How to estimate the mass of an incoming asteroid?

A second galactic visitor has just been observed: see this link. For a mass which is small enough to have no noticable effect on other masses, is there any other way to infer the mass? Its own motion ...
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Dispersion: any software to work out the dispersed waveforms of EMW signals that propagate via interstellar medium for some distance?

I asked this question in the Astronomy site, but seems few people feel interested in, so I hope to have a try here in the Physics site...... Is there any software (toolbox, code, package, paid or ...
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How to interpret doppler curve images of Chandrayaan-2 lander?

The frequency transmission data for Vikram, lander of Chandrayaan-2, received by 25 meter Dwingeloo radio telescope is plotted and tweeted by Cees Bassa. Kinks in the Doppler curve are interpreted as ...
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Is there a Mass-Temperature relationship for main sequence stars?

When finding relationships between various properties of stars, I frequently find next to nothing on the Mass-Temperature relationship. I, of course, see the Mass-Luminosity and the Luminosity-...