Photograph via snooOG

The branch of astronomy concerned with the physical nature of stars and other celestial bodies, and the application of the laws and theories of physics to the interpretation of astronomical observations.

Welcome to /r/astrophysics!

This subreddit is for posts relating to Astrophysics and any branches of that study.

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How do we know the observable Universe isn't a Black Hole?

As I understand it, Astrophysicists view the red shift of distant galaxies to be explained by a mysterious "Dark Energy" which is some form of massive energy that is causing space to expand.

However, it seems like we would have the same observation if the observable Universe was actually a giant black hole, and we were orbiting inside it's event horizon, but still very distant from the singularity.

Those galaxies that are closer to the singularity would be "faster" and therefore red-shifted as they would be moving away from us. Those galaxies that are further away from the singularity than us would be red shifted because we are moving faster than they are.

In other words, how do we know the Universe is actually expanding rather than accelerating into a Universe-sized Black Hole in which we are unable to see past the event horizon?

13:15 UTC


Got recommended a flat-Earther conspiracy video on facebook


I really, really want to see someone more knowledgeable and experient in dealing with conspiracy stuff go through this and point out all the misinformation being told.

11:32 UTC


A quation regarding an earth sized planet, 6 moons, and lining up some orbit stuff.

Heya, ive got a weird question, so im doing world building for a fantasy book but i like to keep things having some physics, even if a little stretched, though ive ways of making it work regardless.

My question is, how could i get it so that each moon is visible to a place on the surface of the planet for exactly 1 day and only 1 day. The moons i get would need to be smaller than our moon, but would it be possible in physics for these moons to orbit at such a timing? While still being prominantly visible within the night sky?

Is the number making it difficult and making it so that more than 1 will be visible at a time?

As for like, reasoning behind things, theres 6 moons cause theres 6 general forces that power the magic of the world (physics manipulation stuff mostly hence how it could be brute forced if needed) and i was planning it so that each day of a 6 day week is named for the prominent moon, though it could be expanded to weeks, months, or even years if need be.

05:27 UTC


Astrophysics with Data Science

Hey Guys I hope you are having a good day I am 16M, studying in high school but hella stressed out for my career which changes every day. I love physics listening about it or talking about it gives me a dozens of dopamine but I also want to help my pay my father's home loan (btw he sacrificed his dreams for giving me privilege to study) and I researched that you cannot get paid good in the astrophysics careers. So I thought why not just do double majors of data science with astrophysics which are high paying jobs also I am going to learn some of computer science in high school. I love theories of relativity, solving math equations and also interested in AI. I see myself solving mysteries of space like dark matter or dark energy I really want to give humanity something. In my POV my financial situation also matter as my desires so my questions are:

  1. Is it worth it to do both of them?
  2. Is it hard to do both of them?
  3. Will I be able to make $100k a year?
  4. What steps can I take right now?
  5. What institute should I go in California?
12:52 UTC


What do YOU think is in a black hole?

If we’re thinking about mathematically, where the matter would lead to past the event horizon, it is essentially so disconnected and irrelevant to our physics. You could argue it has fallen out of our universe.

In that case, I believe it leads to another universe

04:28 UTC


Difference between concentration and specialization

Hello all! I have a dilemma. I’m a physics major and I want to try to get a concentration in computational physics or a specialization in astrophysics. But I want to know what is the difference between a specialization vs. a concentration. Also, is it even worth taking either and just get my degree in physics. Your input is greatly appreciated.

03:04 UTC


Creating a "Realism Based" FTL system - For Fictional Work.

Hello all – I am making this post in a few locations as I am eager to get opinions from those on the purely creative side of life – as well as from those firmly on the scientific end. In short, I am working on developing an FTL (warp-style-esk) system of propulsion for ships in a project I am working on, would very much appreciate some assistance in getting it to feel more “real”. I will be as direct as possible following this disclaimer below…

I am a lifelong star trek fan – but to me that’s science fantasy, and to a point, it delivers good messages on life but not much in the way of real science. I want to create an FTL system for this project that attempts to further real-world science above that of “hand waved space magic” as much as is possible and still tell a story. I think the commonly pointed to “standard” here is the Expanse, I strive to such a standard but not to copy.

My current thoughts, factors, and ideas – of which are greatly in need of your comments and input. 

1-      I grasp that the ability to control or manipulate gravity via some means would be needed for some sort of “warp drive” style system. I am not 100% how best this would be accomplished but my limited research on this topic points towards the possibility that dark energy could be considered “a counterbalance to gravity”? Please provide input, attack or dismantle this line of thinking if I am way off the mark here.

2-      The notions of “hyper-space” or “subspace” are off the table 100% (or anything like them).

3-      The notion that we could use particles or physics that pertain to the “4^(th) dimension” to help achieve FTL is something I would very much like to pursue, with the possibility that in the future, things like “dark matter/dark energy” will be far greater explored then they are now and could possibly (for dark matter anyways) have 4^(th) dimensional properties.

4-      The 4th dimension is not “time”, please google “tesseract” if that is your current understanding of the 4^(th) dimension and then come back here.

5-      One omission I will make, seeing how this story takes place far in the future from now, and actually in another galaxy – is that from a power source perspective, a new series of elements have been added to the Periodic table (well the successor chart to the Periodic table) and some of those are found to be incredible useful in generating huge, huge – amounts of usable energy (but its not unlimited power, nor is it god-like super-rocks, and it has to be mined/refined aka its not a renewable resource).

6-      With things like sub-space and hyper-space off the table – I think that some higher level future understanding of particle physics (aka the CERN facility but fast forward 500 years) would be critical for the creation of things like “shields” or “fields of energy” which would be fields of particles coming out of emitters that are then controlled/shaped/forced into place by various “antennas” and such. Some thoughts here which provide connective tissue are referencing to static fields we can make today – or how electronic warfare/jamming works in the military realm. I would think the control of these particles, specifically ones that are part of a future expanded understanding of dark matter/dark energy, would be critical for the manipulation of gravitational forces – mass – a ships inertia – and all things “anti-gravity”.

7-      In conclusion – I am making some bold assumptions that in the future we will have some very radical advancements in our understanding of dark matter/dark energy and eventually sort out what exactly they are made of and why they do what they do – this then enabling us to do things like FTL which will still being a “science fiction story” – is rooted in SOME level of physics and real world science. 

I am open to all ideas, criticisms of my logic thus far – and any commentary anyone would like to offer on this please.

Thank you for your time!

04:02 UTC


How do I get started on an Astrophysics career?

I’m currently about to go into my senior year of high school, just finished my first physics class and I’ve always loved space and stuff and I absolutely love physics. I plan on taking a AP physics class in my senior year and then for the 2nd semester, the spring semester, I plan on doing dual enrollment at my local community college to get more information onto this topic. I’m not exactly sure where else to go or what else to do. I do have a job and I’m willing to spend money on books that will help me learn more. But I make my state’s minimum wage ($15) so I would prefer to have free resources. I would like some help and advice on what to do and where to go. I wanted to ask my physics teacher but I also do not want to be a physics teacher and I’m not sure if that’s a different way of going about college or not. I get decent grades. I got a B in physics but I had a A until my appendix burst and I was out for 4 weeks. So I definitely understand and can do this work I believe. I plan on getting a degree in astrophysics, I’m not sure if that’s a good idea or if getting a degree in physics is better. But I need some ideas and help from people in the field and like stuff you would’ve done yk?

18:35 UTC


Studying astrophysics

Hello everyone, I am a uni student and my major is kind of a mixture of electrical engineering, automatization and IT (it's weird I know), however lately I've found a passion in astronomy and astrophysics so decided to pursue it at masters lever when I will have finished my bachelor's degree.

My plan is to take a gap year to study the neccesarry math and physics to be able to study astrophysics at masters level because my math and physics just isn't enough so I'll start from the scratch.

I've searched the internet for texts books, videos and other materials but I worry a year won't be enough to study it all.

I really wanna pursue astrophysics and astronomy. Should I start a bachelor's degree again in physics?

What would be your advice?

15:43 UTC


Astrophysics olympiad

I recently got the opportunity to represent my country in the IOAA. Is there any course or any videos i could watch to prepare for this olympiad.

08:13 UTC


Looking for youtube channels that talk mostly about theories

Theres a lot of channels that talk about super well known theories like the big crunch or the big rip, but im looking for more obscure theories, stuff that they either make up themselves or take from obscure sources, anythings fine really. I just wanna hear some out there theoretical scenarios and the details of them (preferably long form)

07:53 UTC


Searching for a radio telescope site name


About 5 years ago, I read an (non-publication) article describing a new site for a radio telescope that was under construction in South America at the time (IIRC). It was mentionned that this site would be so powerful that it could rescan the whole sky (southern sky) in 3 days (*), and due to the volume of data that would be generated, that no Internet connection would be sufficent to allow researches to download their data for local processing. Hence, the article mentionned that the site would have its own data center where astrophysicists would have to remotely connect to run their analyses.

My Google-Fu is failing me here. Does anyone know the name of the site?

Thanks from a curious mind.

(*) Secondary question about this as I have only entry-level general public knowledge here Wouldn't any telescope/radiotelescope be able to scan the whole sky in nearly any given duration so long as it was sweept across the sky fast enough and you accept much less "exposition per arc-second" of the sky. What could have been meant here?


Your collective answers seem to converge on a few sites. I'll reply here rather to avoid repetition.

The ALMA fits nicely my description... and made me realise I wasn't that sure it was a radio telescope and not an optical one.

The SKA is one impressive installation that I was aware of. I still need to do a bit of reading on it to get my head around it.

The Vera Rubin observatory does fit closely to my recollection. And the ability to "scan the sky in 3 days" finally made sense for me. Finding it crossed an item off the massive secondary todo list in the back of my head.

So many great responses, I want to thank everybody who contribeted to my question.

13:06 UTC


Writing a book: What does a normal day in an astrophysicist's life look like?

Dear Reddit astrophysicists,

I am a writer working on a new novel in which one of the protagonists is an astrophysicist. She is involved in a project that searches for new celestial bodies, specifically planets.

I'm a biologist, so I know a lot about science, but not about astrophysics in the sense that I can imagine what the day-to-day work of an astrophysicist looks like. I'm not soooo much interested in the exciting "yeah, we've found a planet!" stuff (but of course would appreciate infos about how something like that ... happens?), but what I am interested in most is all the "boring" everyday stuff. What might a working day look like? When she comes into the lab, what is the first thing she does? What would be typical everyday actions and tasks? I guess it is just a lot of mathing and computer work? But what exactly? I read a lot of books on astrophysics recently to understand the physics, but am still a bit in the dark concerning the daily work.

I would be really happy if someone had the time and inclination to give me some insights! :) I'd also like to meet with an astrophysicist in my city, but I thought I'd rely on the swarm intelligence here first. Maybe that will give me some new ideas on what I could ask the person. I would appreciate answers!

Thank you! :)

09:27 UTC


Dark Matter and energy

We know it exists but can’t find it. It’s probably been dismissed already, but what if dark matter and energy exist outside our four dimensional universe?

03:09 UTC


How would an astronaut level something in space/zero gravity?

Whether they are trying to level something like the equivalent to hanging a picture frame in space or a nondescript surface, how would they go about it?

Surely a situation where astronauts need to level something has occurred, I just can't think of an exact scenario due to lack of knowledge, nor can I find anything online. I know most levels require gravity in order to work. And then it also depends on what they truly define "level" as--is something level when it is perpendicular to the force of gravity and/or just parallel to another object? Could they use several gyroscopes and simulate "gravity" and creating something like an x and y axis?

Or is "level" simply not a property in space? And how do they deal with this?

22:56 UTC


Under a multiverse scenario, could the extra mass from additional surrounding universes eliminate the need for dark matter in our universe?

22:02 UTC


If we are all living in a simulation, is it possible that this could provide a solution to the 'missing mass' problem?

OK I suspect I'll probably get it in the neck for asking this question. Reddit science subs can be kind of elitist. So I always think twice before posting any science related questions. So here goes nothing.

If we are all living in a simulation, is it possible that this could provide a solution to the 'missing mass' problem? Clearly in a simulation the rules (or programming) behind that simulation can allow the rules of physics to vary over different scales?

I asked ChatGPT to give me some insights and to check if the question made sense. This is what it said:

Edit 1, since many Redditors tend not to like longer posts and often don't read past the title, I've removed the full chat GTP response and have created a simple link to the conversation instead.


Here is another link from Scientific American, which will hopefully serve as a demonstration that the subject is often and openly discussed.


For balance, I've included both emergent perspectives in this discussion. The first being the most conservative responses, which in general are that 'It's not science, and therefore it shouldn't be discussed' (At all). (Usually with some added uniquely Reddit flavoured scorn.) The second is that while such an idea isn't strictly considered scientific, there is no reason why such a topic shouldn't be discussed, as it may assist in extending the boundaries of scientific reasoning. (Although that isn't quite the question I originally posed.)

I don't particularly favour any of these perspectives, although I see no harm in discussing such topics. As noted in a response to another Redditor here, many finer and much sharper minds than my own 'tiny feeble mind' (there I did for y'all) have quite openly discussed ideas very much like this over the decades, ever since digital computers first became a thing. So perhaps some Redditors might just take themselves a little too seriously?

Edit 2

Since some Redditors really do indeed appear to take themselves extremely seriously, here is a list of some very notable scholars and proponents of this kind of 'simulation hypothesis'. Only on Reddit do you need to provide a list of 'sources' to demonstrate that this is indeed a valid topic, that is often and openly discussed among some of the most prominent scientific thinkers of our times.

This still doesn't qualify this kind of 'thought experiment' as being scientific, but it does underscore that there are indeed some very much 'heavy hitters' in physics and (computational) astrophysics who are attempting to 'push the boundaries' of scientific enquiry to make it such.

Nick Bostrom:

Field: Philosophy Affiliation: University of Oxford Contribution: Bostrom's seminal 2003 paper, "Are You Living in a Computer Simulation?", provides a philosophical argument suggesting that it is highly probable we are living in a simulation. Publications: Bostrom has authored numerous papers and books on the simulation hypothesis, existential risk, and the future of humanity.

David Chalmers:

Field: Philosophy and Cognitive Science Affiliation: New York University Contribution: Chalmers has explored the implications of the simulation hypothesis on consciousness and the nature of reality, considering it a legitimate philosophical question. Publications: Chalmers is known for his work on the philosophy of mind and has written extensively on topics related to consciousness and reality.

Seth Lloyd:

Field: Quantum Computing and Physics Affiliation: Massachusetts Institute of Technology (MIT) Contribution: Lloyd has discussed the concept of the universe as a quantum computer, which aligns with ideas related to the simulation hypothesis. Publications: Lloyd is the author of "Programming the Universe" and has published numerous papers on quantum computation and information theory.

John D. Barrow:

Field: Cosmology and Theoretical Physics Affiliation: University of Cambridge Contribution: Barrow has written about the anthropic principle and the idea that the universe's fundamental constants may be fine-tuned, which can be linked to simulation arguments. Publications: Barrow authored "The Anthropic Cosmological Principle" and other works on cosmology and the philosophy of science.

Paul Davies:

Field: Theoretical Physics and Cosmology Affiliation: Arizona State University Contribution: Davies has explored the possibility of the universe as an artificial construct and discussed the simulation hypothesis in the context of cosmological fine-tuning. Publications: Davies is the author of "The Goldilocks Enigma: Why Is the Universe Just Right for Life?" and has written extensively on topics in theoretical physics and cosmology. These individuals are recognized scholars in their respective fields and have contributed to the discussion of the simulation hypothesis through their academic work and publications.

17:05 UTC


is being a research scientist still relevant

hi, currently in 12th grade,India.. rn im preparing for jee which gets you into the country's best engineering colleges and also some research institutes in india..ofcourse to understand the universe my country is not the right place so i have to get down in the line for some scholarships overseas...now money is not the reason i would ever back down and not go in research field(which ive been interested in lately) but ig all the discoveries have been made and modern world doesnt know/care about any scientists as it used to when the era of scientists was actually there..so is the interest worth persuing long term?

16:34 UTC


What Sol is it currently on Mars' Gale Crater??

Can someone explain what does it mean that currently the day where the Curiosity rover is located is Sol 4215. My understanding is that Sol is Martian day, the time it takes for the planet to orbit around it's axis. The Marian year is only around 687 earth days and the day on Mars is slightly longer on Mars (24 hours and 40 mins)....how is it that for one Marian year (it's currently year 37), that has only started, it is already day 4215???

Can someone explain please, cos it's driving me crazy.

02:07 UTC


Why Can’t Light Escape a Black Hole?

If the speed of light is constant in all reference frames, then shouldn’t light be able to escape the inside of a black hole? Is it not able to do so because Spacetime is flowing into the black hole faster than the speed of light (relative to far distant observers)? Is it because light is infinitely redshifted on the way out?

TYIA for any help with this!

01:09 UTC


Highschooler highly interested in becoming an astrophysicist.

Currently in 10th grade or sophomore year. I want to become an astrophysicist or something related to space and research but I have no idea where to start really. I would appreciate someone who reaches out and gives me a path towards astrophysics. Thanks!

13:25 UTC


How to follow latest development in research of black holes.

Like which are the best publications to read for black hole research papers.
And are there other ways to stay updated.

06:27 UTC


What are your favorite memoirs written by astrophysicists

I’ve been on an astrophysicist memoir binge these past few months. Looking for some new book recommendations. What are some of your favorite memoirs by astrophysicists (open to physicists and Astro biologists too) and why?

23:15 UTC


What are your favorite astro conferences?

Out of curiosity, for the astrophysicists in the community, what are some of your favorite astro conferences and why? What are your main objectives when visiting these conferences?

I’m heading to Exoplanet 5 next week!!

23:08 UTC


How sure are we that there is a singularity?

Hobbyist, space lover here.

I recently got intrigued by pulsars. I read a lot about them on the internet and thought to myself - how sure can we be about the singularity? I know what the math says that the core of the sun keeps shrinking until mathematically reaching an infinitely dense point - a singularity.

My question is - how can we be sure? I mean pulsars are halfway there, if you will. Could it be, that a black hole has an immensely dense core with gravity so strong, that even light can’t escape it? I mean, are there any theories that would bend the laws of math?

This question has been driving me nuts! I mean things get pretty crazy near black holes, is there a way black holes could have unimaginably dense cores? Imagine such a core with a diameter of 100 m and a mass of a couple of suns.

I can’t seem to find anything about it, perhaps for a good reason that I am not aware of. Thanks and looking forward to enlightenment :)

19:55 UTC


High schooler interested in astrostatistics but dont know where to start

I'm finishing up grade 12 and will be pursuing my undergrad in statistics at the univeristy of toronto. I'm interested in astrostatistics, although from my research i've seen most people have physics backgrounds rather than stats. I'm more interested in actual statistics/machine learning concepts and applying them to astronomy research rather than learning the physics behind the projects. Do you guys think thats possible or would a physics background be necessary?

18:16 UTC


anyone dealing with cross-matching catalogs of extra galactic sources with astropy?

Premise, I am not a student anymore but since I had to stop my PhD for medical reasons quite a few years ago, I am working on this project on my own (some AI input that is wrong half the time). So I need someone to explain some things i don't understand and tell me i am not going something stupid. Also, If this is not the place to ask, does anyone know where or who? Thank you.

I am trying to crossmatch the latest Fermi LAT catalog to an sdss catalog. I found tsuji et al. 2021 where they create a distance profile and used to decide the cutoff. I did it by using a separation function in astropy but the histogram shows a linear increase where I was expecting a bump near 0 and then a linear increase.

Then I used the match_to_catalog_sky function and in the output there is the bump but not the linear increase..... WHY?!?!?! I created a random catalog to check number of false matches and whether the distribution was a result random matches (chatgpt idea) I did a KS test and I got KS Statistic: 0.7842946490618485, p-value: 0.0 .

Is it correct to just use the output from the match_to_catalog_sky function and setting the cutoff from CDF of the d2d of random position catalog?

11:41 UTC

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