Galaxy Definition and 510 Threads

Neeleman, M., Prochaska, J.X., Kanekar, N. et al. A cold, massive, rotating disk galaxy 1.5 billion years after the Big Bang. Nature 581, 269–272 (2020). https://doi.org/10.1038/s41586-020-2276-y Abstract Massive disk galaxies like the Milky Way are expected to form at late times in traditional...

To simulate the trayectories of solar systems around a black hole (i.e. a galaxy) I have 3 classes in C++: cSystem, cBlackHole and cGalaxy. cSystem assigns initial values of position, velocity, etc to a solar system. cBlackHole does the same but just for the black hole. And cGalaxy mixes...

In Sf, we can regularly see planets and other places that are very different from what we see on Earth, or even in the solar system. How plausible are the following ones? - Dense asteroid storm. Maybe a new planet is forming, or a giant comet recently shattered? Can such thing exist in a...

From, https://www.universetoday.com/143977/watch-a-simulation-of-a-galaxy-from-the-big-bang-until-the-present-day/ "This was made possible by the Hazel Hen supercomputer in Stuttgart, where 16,000 cores worked together for more than a year – the longest and most resource-intensive simulation to...

We do not currently have the ability to detect a Kardeshev 1.0 civilization at Alpha Centuari. Here is a paper showing Alpha Centuari has infrared emission close to a K1.5 civilization. Emissions from a K1.0 would be completely lost in the noise. There is some evidence that Kardeshev 2.0...

See the attached figure. I understand that we look for the apparent transverse velocity v , for example through v = d/t (d - distance, t - time). The distance to the galactic nucleus is known as D. Though I am not sure how to read off the time from this figure.

Hi, I recently learned that if you can travel at the speed of light, or nearly, you can reach the Andromeda Galaxy within 30 years, due to time dilation and bypassing 2.5 million years on Earth. Is this true?

I was looking at a photo of this galaxy, and noticed a bunch of red dots in it. Could it be that these dots are individual red supergiants? (I used the photo at the Wikipedia article for reference.)

Hi, and thanks for reading. I asked this question in another forum too. If we agree that Andromeda is 2.5 million light years away, and its diameter around 220,000 light years, I don't see how it just appears as a regular point of light like any other star in the unaided eye. Something that so...

The graph in Wikipedia, article Milky Way, section Galactic Rotation, shows the actual rotation speeds in blue and the calculated speeds due to observed mass in red. (The graph is to the right of the article.) At about 3 kpc the actual speed is about 205 km/s. To account for the decrease in...

I could never be an engineer here on Earth. I’m too dumb. My math skills and spatial intelligence suck. I wonder. If I lived in the Star Wars galaxy, would it even be harder to be an engineer since everything is so much more advanced? I imagine engineering schools in the Star Ward galaxy only...

As indicated in the title and summary, I'm wondering if there is any large scale astronomical effort to assess directly the universal spatial expansion assumed by the Doppler interpretation of the redshift/distance relationship, by measuring individual galaxy subtended angles over time. The...

What I’m looking for is some new avenue of physics for a scientist in the Star Wars galaxy to be studying. They probably know what dark matter and dark energy are since Starkiller Base is powered by it. I’m sure they know about how the universe began, why it’s expanding and what it’s fate is...

If you fill a sink with water and then let it drain, the water swirls due to the rotation of the Earth influencing it. During star formation, the primordial accredisk disk spins due to it's galaxy's rotation as I understand it. This being the case, what force made / makes the galaxy spin to...

So the universe is expanding, and galaxies are getting farther apart from one another on average. Does this motion count the same as ordinary motion, in that if a galaxy is being expanded away from us at 0.5c, that clocks in that galaxy would appear to tick slower at 0.866 the rate of clocks here?

I thought this article was interesting (and here). It made me think, if a transformation is sufficient to eliminate or create Dark Matter... Then the mystery of the existence of Dark Matter would become a mystery of why all of the other distance measurements are wrong in a universe without Dark...

Summary: I am assuming that there is a database somewhere listing all of the galaxies which astronomers have found. If that is correct, my question is: What fraction of these galaxies in the database have a distance from Earth value associated with it, other than a distance based only on the...

A previous thread outlined the problem with a correct answer, however I don't understand where they got the formulas from. Here are the steps I've taken so far: 1. Convert 2*10^8 years to seconds = 6.3072*10^15 seconds (period,T) 2. The previous thread then went on to say you plug period and...

I have found plenty of information about the radio source Hercules A. Its large radio jets are 1.5 million light years long from end to end, the supermassive black hole that produces Hercules A is 3 to 4 billion solar masses, and the black hole exists in the center of galaxy 3C 348. However, I...

Like what are the chances that dark matter can be described with electromagnetism instead?

Hello, I am using a code on EUCLID future mission. The original author of this code has set a value for the density of galaxy equal to : ng = 354543085.80106884 I think this is expressed in inverse steradian. I think that EUCLID mission has a 30 arcmin^-2 value for density of galaxies...

I need to calculate the recessional velocity of a galaxy 500 Mpc away. I need to express my answer in KM, distance in speed, age of the universe in seconds and years.

How would the acceleration of our sun relative to our galaxy be determined? A spaceship in orbit around our sun, with engines turned off, is in free fall. Accelerometers will read zero. Turning the engines on, the accelerometers will read the acceleration due to the thrust from the engines...

Homework Statement Assuming a Salpeter IMF with upper and lower mass limits of 0.1 and 20 M⊙ respectively, calculate: (i) the mass point at which half the mass formed in a stellar cluster lies in more massive systems and half in less massive systems. ii) the mass point at which half the...

There are galaxies that are so far away that metric expansion causes them to have a co-moving recessional velocity that exceeds the speed of light. However, those galaxies are also so far away that the time it took the light to reach us was itself billions of years in the passage of its journey...

Wikipedia describes the distribution of Dark Matter as a halo around our galaxy. Are there any laws or equations on the distribution of dark matter? From what I have read, dark matter does not clump into stars, since it cannot radiate energy. It cannot be seen or directly observed. Does it repel...

I'm learning about imaging techniques and projection/deprojection for images of galaxies at university. The big issue there is the fact that an image is a 2D representation of a 3D object (for example a galaxy), and to learn some properties of the object you need the 3D structure. What happens...

https://arxiv.org/abs/1901.05973 It seems like there is some thing unexplained here, what is going on?

Hello to everyone, I'm trying to find some data about the relation between galaxy age and rotational curve... until now without success. Are there any teams working on this? Are there any studies in this direction? Thanks!

Hi, this is just a question I've had for years and have not been able to figure out because of conflicting information. I have read that space is expanding and that it's speeding up, but also have heard that in about 5 billion years our galaxy and Andromeda will collide. How is this possible...

After much questioning and soul-searching I got my answers of why galaxies rotate, and for that I greatly thank the gurus in the forum (so I'll not forget: conservation of initial angular momentum, non-isotropic material scattering, slowdown of infalling materials and non-isotropic infalling of...

Hello, Suppose that all stars in this galaxy were born in a single major-merger burst event about 10 Gyr ago If the luminosity in the B band (absolute magnitude in B-band is equal to -21.22) is dominated by stars of in the RG branch, with masses ##m \sim 1\,\text{L}_{\odot}## (within ##\sim...

<Moderator's note: Moved from a technical forum and thus no template.> Suppose that all stars in this galaxy were born in a single major-merger burst event about 10 Gyr ago. From this original burst, I want to compute the fraction of stellar mass still surviving as stars in the main sequence ...

I am trying to estimate the distance of closest galaxy neighbor knowing the expression of number of neighbors into a volume ##\text{d}V##, the mean density ##n_\text{gal}## and the correlation function, i.e with this expression : ##\text{d}N=n_{\text{gal}}\,\text{d}V\,(1+\xi(r))## with...

I'm close to 60 years old now, and when I was a 12-14 years old kid my father had a small 50mm telescope -- I still remember how amazing the word "Tasco" looked back then! Back then I could watch the moon and Jupiter, although I was upset that Jupiter kept moving out of sight all the time. How I...

Is it possible to estimate the gravitational force of the center of a Galaxy (it could be Andromeda or the Milky way) to any point (such as a planet) of its Orbit? Furthermore is there such as Schwarzschild solution that calculates the time dilation of any point of an external Galaxy (e.g...

Last week I posted in General Physics some questions about what happens in a collapsing gas cloud, and I was advised that total angular momentum is conserved. I thought of asking for extra clarification here, as that seems really amazing -- I apologize for asking the same thing twice. I use a...

It seem incredulous to me that the Milky Way was formed just 13.775 million years after the start of the universe. If this is correct was it in the form that it is today?

I'm just wondering about time dilation in regards to both special and general relativity within our galaxy. Does time move slower or faster relative to us within the inner parts of the galaxy? I know at the horizon of the black hole time is effectively not moving. This implies that locations...

First of all, sorry for my naive question here which likely doesn't make sense. The universe is currently expanding with galaxies receding from each other at increasingly faster pace. Is it possible that the universe is a closed hypersphere system, where galaxies are actually not actively...

Homework Statement [/B] I have the following questions as homeworks and I would like to get help. Question 1) Give the formal expression of the total number density of galaxies. Why is this expressoin problematic in practice? Question 2) In practice one uses a numerical value for the number...

Into an extra-galactic physics course, I don't understand well the "Gunn - Peterson" effect on the spectrum of high redshift quasars (z greater than 3 or 4, up to the current limit of z = 6-7 I think) The observed fact is that there is an almost total absorption for the photons of the blue part...

If a wave function could be assigned to a whole galaxy, would its mass spread along the wave? Could this account for the anomalies in our calculations for galactic spin?

I was hoping someone knows of a model that can define a point on Earth at any given moment that is pointing in the direction of the Earth's path around the Milky Way. I realize that the point would always be changing.

https://amp.scroll.in/article/883720/how-we-proved-that-einsteins-theory-of-general-relativity-holds-true-even-beyond-the-solar-system Read the Section in this link: Cosmic alignment The galaxy we investigated has the catchy name ESO 325-G004 – let’s call it E325. Located some 450m light years...

I read that in 1900 astronomers thought that our own Milky Way Galaxy was the only galaxy in the whole universe. This puzzles me because I presume they knew about the pinwheel structure of our galaxy and there were telescopes back in 1900( Yerkes for instance)which were large enough that could...

Why is the density of matter greater near the galactic center?

Good Morning, I've got a doubt originated from a statement of Berkeley Physics Course, Vol.1 - Mechanics, pg. 107, where in a footnote we read, "The systems are called galaxies, that one which contains our own sun is known as the Galaxy. The Milky Way is part of our galaxy". I've always...

I have read somewhere that the parallax method can be used to measure the distance to stars up to 400 light years away. I did a quick calculation and estimated that it means that our telescopes can resolve an angular movement of 8.15x10-3 arc seconds. Taking the distance between the sun and the...

Just noticed this article. Wonder if anyone here has further info. Sounds very interesting. http://www.bbc.com/news/science-environment-43543195