Questions tagged [galaxy]
Questions regarding systems of large numbers of stars held together by gravity.
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How fast is Andromeda approaching in miles per hour
Apparently Andromeda is going to get here in 5 billion years and is 2.5 million light years away. I tried to work this out myself but I'm not sure I believe the answer..
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Spiral Galaxies
I only have a very, very, basic understanding of linear motion, much less so of circular motion. What I can recall is my book telling me if you spin a stone tied to the end of a string and the string ...
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Consistent values for density of galaxies between degree squared and steradian
I have a table of densities of galaxies :
Expected number density of galaxies for photometric survey per unit area and redshift intervals, $\mathrm{d} N / \mathrm{d} \Omega \mathrm{d} z\left[\mathrm{...
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What happens when two galaxies each with relativistic jets collide?
Would the relativistic jets create new particles where they meet and would all the gas from the two accretion discs be blown away leaving just two black holes?
user52681
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Why does the metallicity of stars decrease with increasing galactocentric radius and height above the galactic plane?
Metallicity decreases with the Galactocentric radius and height above the Galactic plane (Bergemann et al. 2014; Duong et al. 2018).
https://www.aanda.org/articles/aa/abs/2014/05/aa23456-14/aa23456-14....
user52681
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how to make postage stamps of galaxies
I am trying to follow the work in this paper, Reproducible k-means clustering in galaxy feature data from the GAMA survey, and I noticed that there are a few postage stamps of some galaxies. I am not ...
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How do Spiral Galaxies become flat?
Our galaxy has been described as roughly the shape of a pizza and the Andromeda galaxy, though I've never heard it described that way, appears similarly disk shaped. Spiral galaxies make up (roughly) ...
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Gas mass and velocity in galaxy
I was going through the SPARC data on galaxies (http://astroweb.cwru.edu/SPARC/)
The velocity of gas in the SPARC data is in http://astroweb.cwru.edu/SPARC/MassModels_Lelli2016c.mrt
The gas velocity ...
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Could a galaxy be the sun of a planet?
For the purpose of science fiction, could an entire galaxy essentially be a planet's equivalent to our Sun for Earth?
If a planet were far enough away from other objects in the galaxy but still ...
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Measuring magnitudes in ds9
I'm currently working on a project which involves measuring several Cepheids to determine the distance to a galaxy. I have been using 12 images from the Hubble telescope taken over a period of about a ...
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calculating mass of galaxy from luminosity
A very elementary question, just to make sure I got this thing right.
Suppose we are given that the mass to luminosity ratio of a galaxy is $2 \frac{M_{\odot}}{L_{\odot}}$.
Let us say, that the ...
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Are there any galaxies that spin "out of balance" as wet towels sometimes do in the washing machine spin cycle?
Can a spinning galaxy be "out of balance" like wet towels in the spin-cycle?
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Distribution of Galaxy sizes (star count)
First off, I realize how hard this is to even come close to estimating, but I'm trying to get a "general feel" for the distribution of galaxies by star count. I realize everything from rogue ...
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Orientation of the Dark Matter Halo in Andromeda Galaxy
In this paper: https://iopscience.iop.org/article/10.1088/0004-637X/789/1/62#apj496316t3
Refer to the Discussion and Concluding Remarks section. It says,
"This result also indicates that the ...
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SExtractor parameters for identifying Star Forming regions
I am using SExtractor (Source Extractor) to identify Star-Forming regions in a galaxy. The problem is I am unable to choose the parameters required for it. SExtractor is just a tool to identify the ...
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Why is the Milky Way today about the same diameter as the visible universe was when recombination happened 378000 years after the Big Bang?
Has the Milky Way undergone an expansion of space time independent of the universe as a whole or did the gas that created the Milky Way heat up and expand? Whatever the answer, why the current ...
user52290
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Has the "Big Bang" theory been disproven?
The Space telescope has detected some mature Galaxies close to the edge of the Universe. That means that they had formed more than 13.8 billion years ago . If the Big Bang occurred, then we would see ...
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Is it possible to detect lyman alpha blobs (LABs) with the lyman-break method?
LABs are luminous extended nebulae of hydrogen gas in the early universe (z ≥ 3) found in overdensities of LAEs (lyman-alpha emitters) and LBGs (lyman-break galaxies). I was wondering if LABs could be ...
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Is the object mass distribution different for galaxies of different diameter?
Let's say we compare two elliptic/spiral galaxies with the bigger having a diameter 100 times the smaller.
Now we count every separated object inside them and classify them into mass categories e.g. $...
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Sloan Digital Sky Survey - Obtaining Spectral and Photometric Datasets
I am working on a soft computing (fuzzy logic), genetic algorithm, explainable AI (XAI) classification system for astronomical objects from the Sloan Digital Sky Survey. The dataset I am currently ...
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Elliptical galaxy classification
The elliptical galaxy (Hubble) classification goes from E0 to E7, with E0 being spherical and E7 being the most flattened. I understand that the angle at which the elliptical is viewed affects this ...
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Galaxies contracting
How fast is our galaxy contracting? Could our "expanding universe" measure actually be a measure of how fast our galaxy is contracting from other contracting galaxies. Thank you .
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Do researchers create their own convolutional neural network models for their work or do they use existing ones (e.g. YOLO, detectron2, etc)
When a researcher first decides to use AI to solve a basic classification problem, such as training a neural network to determine the morphology of a galaxy, are they more likely to start by using ...
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How to get star position from the Gaia data set?
I’m trying to recreate the Milky Way as a particle system inside Houdini, and I wanted to explore using the Gaia data as a starting point.
I’ve downloaded an example source file from the data set but ...
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What do we know about properties of individual stars in the Andromeda Galaxy?
According to the answers to Visible Stars in Andromeda Galaxy, is it possible to distinguish between different stars in Andromeda galaxy. What I am curious about is how much information are we able to ...
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Where to find data about as many stars as possible?
I need computer-readable data about as many stars as possible, with their:
distance to the Earth (or Sun),
their masses,
and if possible:
coordinates,
age,
brightness
distance to the center (...
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What is the relation between column density and surface density of neutral hydrogen gas HI?
I know the column density distribution of neutral hydrogen gas (units: cm^-2). I want to calculate the corresponding surface density distribution of the neutral hydrogen gas (units: M_solar/pc^2). How ...
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Could macroscopic primordial black holes have created metals shortly after the big bang?
After seeing articles about the jwst like these two: https://news.cornell.edu/stories/2023/02/astronomers-discover-metal-rich-galaxies-early-universe
https://www.livescience.com/james-webb-space-...
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As redshift increases are there more large galaxies from mergers because there was less dark energy in the past?
Dark energy moves galaxies apart.Is this reflected in an increasing number of large galaxies as redshift increases and dark energy decreases?
user51226
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How to obtain the SDSS’s five-part imaging ID number for a list of galaxies whose Ra Dec is known?
I am trying to obtain the FITS file of a few hundreds galaxy from SDSS DR12 Survey. SDSS tries to download the FITS File with the link that contains the information about SDSS’s five-part imaging ID ...
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Finding Position angle and ellipticity to Deproject galaxy image using IRAF
I am trying to obtain position angle and ellipticity for a galaxy image by fitting elliptic isophotes using IRAF routine stsdas.isophote.ellipse package. After fitting the isophotes, I have a table ...
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Can the collapse of a gas cloud lead to an elliptical structure?
Is it likely, unlikely, or impossible for an elliptical structure to form when a gas cloud collapses?
Due to the conservation of angular momentum, one would expect that disk structures are much more ...
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Has the missing dark matter in some galaxies been explained yet? [duplicate]
There are galaxies that should have dark matter to explain their existence but they do not.
"Mystery of Galaxy's Missing Dark Matter Deepens | NASA" https://www.nasa.gov/feature/goddard/2021/...
user50918
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What is the unit of the correlation function between logarithmically rebinned galaxy spectrum and stellar template spectrum?
Assume I have a logarithmically rebinned galactic spectrum $G(x)$ and a stellar template spectrum $S(x)$, where $x = \ln{\lambda}$. When $[\lambda] = 1 Å$, then $[x] = 1 Np/Å$. The fourier transformed ...
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How does superfluid dark matter keep stars orbiting at high speeds in galaxies?
According to A paper on Ultra-Light Dark Matter, Superfluid dark matter is a kind of Bose-Einstein condensate. But how does it help stars keep their high or velocities in galaxies. Can somebody ...
user50918
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When two galaxies with dark matter halos merge do they provide evidence for fermionic or bosonic dark matter?
If dark matter is made from fermions these should collide and cause dark matter to become denser in some places than others Bosons wont collide in this way so there should a different effect .So is ...
user50918
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Can someone explain the strange case of NGC 4319 and Markarian 205 and its controversial redshifts and later convinced by reddening?
(source)
When they saw in neutral hydrogen wavelength they saw a neutral hydrogen bridge, while the Hubble Space Telescope concluded that the light from the quasar was redshifted. So if it's ...
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If a supernova explodes close to the centre of the milky way does its light get blueshifted by dark matter by the time it reaches the Earth?
Does the dark matter halo of the milky way cause most of the change in wavelength or is baryonic matter responsible?
user50918
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Creating a small data pipeline
I wanted to create a small data pipeline such that it consists of images of sky in the filters F125W, F160W, F606W and F850LP. The 4 images for a single object should be in a single FITS File which ...
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How to construct optimal Wiener Filter?
I am trying to construct a Wiener Filter, to filter the ratio of the peak from the cross-correlation function, between a galaxy spectra and a template spectra, with the peak of the auto-correlation ...
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Is the mass function of dark matter halos fundamental or an approximation based on experimental data?
Can the halo mass function be derived from existing physics or is it just a best fit of some data?
user50918
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What courses should one take for working towards Astronomy from an AI / Data Analysis perspective?
Note:- This is a suggestions seeking question
As a prospective student about to embark on pursuing the MEngg. in Applied AI program, I am eager to align my education with my passion for Astronomy. I ...
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What am I doing wrong in this ppxf application?
I am trying to derive the kinematics of a galaxy spectra. To test my results I want to implement the Penalized Pixel Fitting method. For the galaxy spectrum I use a central line with sufficient S/N. I ...
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Determining the rotation curve of a galaxy via given spectroscopic data
Here is the data analysis question from IOAA-2011,
1. Weighing a galaxy: The image 8.2 shows a photograph of the spiral
galaxy NGC 7083, which lies at a distance of 40 Mpc, and image 8.3 a
fragment of ...
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the sun - relationship between gravity and temperature
In the sun's core, we know it's very hot.
I was curious to research why it was exactly and I think 99% of answers are not fully correct. They say that it's because of nuclear fusions.
I'd not agree as ...
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sun - do gamma rays reach radiative zone
So in the sun's core, gamma rays are produced and right away, in the few milimetters, compton scattering happens.
As I understand the compton effect, gamma ray will first collide with free electron, ...
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sun's core - how much x-rays get emitted
We know from the sun, we receive x-rays, gamma-rays but at a very small number of photons.
Question 1: why not much ? is it because most of the x-rays are absorbed in a process of ionization of the ...
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Emitting light from the Sun [closed]
I might be asking too many questions here, but they all seem related to each other and knowing them simultaneously is the only way to understand this subject as I have tried my best googling already.
...
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Nearest spiral barred galaxy undergoing interaction
Which is the nearest spiral barred galaxy undergoing interaction, other than M31 (Andromeda) and our own Milky Way galaxy?
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do we observe emission spectrum? [duplicate]
When light generated by the fusion in the sun goes through the layers of the sun and finally reaches outer layers and in the end atmosphere of the sun, we know it goes through hydrogen for example. ...
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