r/astrophysics

I'm writing my own little book, and in it I have two characters fighting. One of them uses a big ass laser to vaporize the other. my question is, how much energy/heat would it have to produce to burn a hole through the Earth, and would it affect Earth in any other way outside of, well the big ass hole? Lastly, how big does that hole have to be for it to destroy the Earth? Would a hole the width of football be sufficient?

Hi r/astrophysics, I previously asked a much more broad version of this question, which turned out to be way too hard to answer. Hopefully this is a little more "possible" haha.

That being said:

Do all planetary bodies which become spherical later begin spherically, OR is it possible for the early stages of many planets to be irregularly shaped, until more mass is accumulated?

For example, in the very first/early stages of a planet's formation, would we be looking at something sort of bumpy, potato shaped, and not-very-round? Or would we be looking at something spherical right off the bat, albeit very small?

If it IS possible for something irregularly shaped to then accumulate mass until it's gravitational force forces it round-- what are the chances of an asteroid or planet-shard becoming a planet?

Thank you for taking the time to read! Hopefully this wasn't too confusing. I haven't been able to find any answers online and would appreciate any insight, however small.

Hi r/astrophysics, I've been thinking about this for a few days. There's a few questions here, so bear with me.

Firstly, do all planetary bodies which become spherical begin spherically, or are the early stages of many bodies irregularly shaped, until more mass is accumulated?

Next, why aren't some of even the largest asteroids then, for example, not spherical? Where's that "tipping point" in size, volume, and mass that causes a spacial object to become (or begin) a spherical shape?

Lastly, is it possible for an irregularly shaped, non-round body to become spherical later due to mass accumulation?

Thank you for taking the time to read. Really looking forward to the answers.

Hey folks! I'm pleased to let you know that I just successfully defended my PhD in astrophysics :) to do so, I had to write and publicly defend a dissertation on my work in high-energy/gravitational astrophysics. While doing this, I had a really interesting idea.

I received very helpful and constructive feedback from my committee on several chapters in my thesis, and the thought occurred that maybe I could have polished it more before sending it to them if I had passed it through an LLM first, to see if it could spot at least the most significant issues. I was intrigued by this because (1) this is WAY easier than the previous experiments I've done. Reading an intro chapter containing knowledge *comfortably* within its training dataset and fact-checking it for technical issues should be well-within the applicable use cases for a "PhD-level expert in your pocket" that is "too dangerous to be released" as they are marketed. And (2) this would be a shockingly useful use case for me. If I could get reliable, substantive feedback on my writing I would run everything I have through these things. It's like having a free grader that you can converse with as much as you want--I would be thrilled by this.

My method was fairly simple. I have a rough draft of my introductory chapter, and comments from my committee. If I pass the same text through an LLM, will it give me similar feedback? I'm not asking it to do new science or make any discoveries; just to check my descriptions of frankly very well-established concepts, which should be a piece of cake for something that is "better than PhD level" in "all subjects no exceptions" which does well on tests that "most PhDs would fail". I use Claude Opus 4.7 with extended thinking activated on the maximum effort mode, which is the best model I had access to (this was conducted back in April).

The results were frankly quite shocking to me. It read through the text in detail and returned about 30 comments. Claude returned 13 of what it called "genuine technical errors", four of what it called "citation/factual issues", and five "logical/expository issues". Of the 13 technical errors, one was accurate but extremely minor (suggested word change from "evaporated" -> "released"), three were factually correct but not an error I made--Claude simply restated something I said correctly--and 9 were fully inaccurate, hallucination-level claims, like confidently claiming I reported a formula incorrectly and even citing the original paper when what I had written matched the original formula exactly. Just straight up hallucinations of honestly not very complicated material. One of the best illustrations of this was when it claimed a formula for Type IIP supernova plateau luminosity L ~ Ec/(k M) was dimensionally incorrect, which is an incredibly simple check that it got wrong. I was absolutely blown away by this error (and there were many more like it) since a high school student could have correctly checked the units on that expression and realized it was right. I go through a few other examples with more detailed explanations in the video, if you want to see more.

Of all the comments it gave, basically zero were correct besides very minor typo fixes. The worst part of it was there was actually a glaring conceptual error in the chapter that my committee flagged immediately, that Opus should have been able to spot as it was a pretty severe mis-statement of an important concept. Its the exact kind of thing I would have been raving about had it spotted it since that would be incredibly useful as someone who needs to learn new things frequently and would love a check on my conceptual understanding.

I understand that we are sort of getting societally acclimated to the approximately correct nature of LLMs. But based on my experience with this particular experiment, I would be extremely cautious when relying on any unsourced statements or interpretation from them, no matter how seemingly trivial. The wide range of hallucinations ranging from direct mis-statements of literature to completely missing deep conceptual issues raised alarm bells for me, especially given how these tools are touted based on their supposed expertise level and even their performance on graduate exams. This task should have been comparatively easy and I'm honestly at a loss for why it was so difficult. I know there will be comments saying that I should use the $200/mo version but I strongly believe that this task (which solely required information synthesis and comparison of a very tightly constrained set of ideas fully available online and in its training data, ZERO creativity or discovery ability required) should have been well within the purview of Opus 4.7 + extended thinking + maximum effort. It's not like I ran out of tokens--the response was just wrong on all counts.

I'm really curious to know your thoughts on this. We've had great discussions here in the past and the general sense I got was that people are not surprised these things can't do science. But did you have a vague sense they were at least good at *literature review* and information synthesis? Have you had a chance to do a very deep dive with an LLM on something you are an expert in? Would love to hear your thoughts! Thanks so much for taking the time to read this.

hey gang,

looking for some guidance and a reality check - i’ve read through the wiki but wanted some more specific help

I’m 30, trans (sharing this as the wiki specifically calls out ageism and sexism), and spent a massive chunk of my 20s dealing with cancer treatment, so I’m starting a bit late on the “proper education and career” front (i think i have a pretty good excuse).

Currently i work in a devops role, i don't have a Bachelor's degree, but i landed professional entry into a Master of Computer Science. i’m one year in with a 6.3/7.0 GPA, but i am having a massive crisis of faith about my direction.

bluntly, i hate where the wider tech sector is heading. between the constant layoffs and the pressure to push corporate products that are actively making the world worse, i feel incredibly disillusioned.

About a year ago I saw Saturn through a telescope for the first time and cried, since then my passion for astro has grown - reading books and learning consumer level information as much as i can. i don’t remember having so much hope as when the Artemis mission happened - i was really inspired.

im good at swe, and its a viable, potentially well paying (if a little shaky) career but i think ive realised i want to work on something that actually fills me with joy and embraces the unknown for the betterment of all of us.

my ultimate goal would be working in computational astrophysics, observational astronomy, data science, or radio astronomy (basically not straight theoretical physics) but i need to know if this is a ridiculous idea or something semi-viable.

pros and cons of me today
- pros: i have a strong IT/Ops background and solid Python skills. im currently doing the University of Arizona 'Time and Space' course on Coursera during a mid semester break and have found the content fairly manageable so far.
- cons: my math and physics foundation is practically non-existent. my only postgrad exposure is some discrete maths and DS&A subjects in my degree. i have very low calculus or physics knowledge. i’ve purchased Carroll, Ostlie, An Introduction to Modern Astrophysics and am acutely aware of how little i know (but hey i’m working through it slowly)
- other: i have EU citizenship, which might open doors overseas later especially as Aus doesn’t have a large space/research sector in comparison to elsewhere.

i’m currently considering changing my MCS (stopping at the Grad. Dip) to a Masters in Astronomy/Astrophysics, the potential courses I’ve found have pathway courses for maths/physics intros and there’s an online option that would easily work for me or i could try and get into a more challenging but better respected interstate face to face program.

Questions:
- my guess is that my background makes me non-competitive for academia, which makes working in industry/adjacent unlikely so even if i changed courses i’d still probably run into the same outcome my current masters gives me - would that be correct?
- so then is it smarter to just keep astronomy as a dream? (get a tech job to pay the bills, and just buy a nice telescope and keep up to date on literature) is a professional pivot realistic?
- instead of traditional academic research, would I be better off targeting research software engineering or high performance computing? ie, can I pivot into the infrastructure side of with a CS background and a Astronomy masters, rather than chasing a traditional PhD?

clear skies, and thank you in advance :)
juno

(also on mobile so sorry for formatting)

As the title says I’m a bit worried about getting into a grad school with my current grades. I’m a rising junior pursuing a physics undergrad w/ a minor in astronomy and a certificate in data science. I’ve only gotten Bs in my core physics classes (My only As were in labs and research courses), and in my math classes I have one A-, one B, and one C (only counting Calcs I-III, not math methods of physics courses). However, I’ve gotten an A and A+ on both my astronomy courses thus far, and I’ve also gotten As on my data science courses too, which I’ve realized I’m more interested in than physics alone. I’ve also done research in time-domain astronomy (during my sophomore year) and will do a semester of theoretical and observational high-energy astrophysics in the fall if all goes well. As for summers, I volunteered in my last one at my local university, helping astrophysics professors with summer programs and some lab diligence, but no actual research (did learn a bit of how to process data from JWST which was pretty cool). This summer, I’m just doing some readings so I can understand the concepts and physics behind what research I’ll be doing next semester. I guess I’m just a bit worried about this, so I’d appreciate any advice from anyone who was in a similar position or any graduates or professors who see this often. I’m open to any insight, even if it’s a hard to swallow pill.

Hello everyone. I'm an undergraduate heading out to college in August. I was undecided recently until finally believing in myself and choosing astrophysics despite all the horror stories I've heard regarding its difficulty.
I chose it over some of my biggest passions, Film/Animal Sciences, since I've been told its better to get a "safe degree" than a "passion" degree and then use the money from jobs with said degree to fund your interests later in life.

That said I'm getting an equal amount of both pros and cons when it comes to Astrophysics as a degree. A lot of people are saying its versatile and you can get a lot of jobs with it, while others are saying it doesn't pay well, there's a lot of competition in it and the job market is terrible.

Astrophysics wasn't my top choice since I'm not entirely enthused about maths but I'm a willing and hard working learner. I pretty much fall into the "Just wanna do something I don't hate that pays okay" type of person everyone's so used to seeing.

I'd love to hear from others in the field either as students, graduates, dropouts or workers: How hard was it earning your degree? Do you regret it? Have you had trouble earning jobs with it? Did you have to travel due to it? Has it offered you opportunities? Can you secure work visas with it? I'd love to hear any pros and all cons you can think of.

For info: I am in the US, with hopes of finishing degree abroad in EU and willing to move for work.

Let’s say our Sun just vanished, no supernova event or anything. How long would it take for us to lose our orbit and where would we go? Would we collide with anything?

Something I keep coming back to: neutron stars sit right at the edge of what matter can survive. They are the densest directly observable objects we have, and we can actually measure things about them, mass, radius estimates, gravitational wave signatures from mergers. Black holes obviously cross a threshold neutron stars do not, but I wonder how much of the interior physics carries over conceptually.

The singularity at the center of a black hole is usually described as where our math breaks down rather than a literal point of infinite density. Some models suggest a finite ultradense core instead, which sounds suspiciously like a neutron star pushed past its limit. Quantum gravity is supposed to fix the breakdown but we have nothing testable yet.

My question is whether neutron star observations actually constrain anything meaningful about black hole interiors, or whether the event horizon is such a hard information barrier that the two objects are basically unrelated from a physics standpoint once you cross the mass threshold.

I know LIGO data from neutron star mergers has pushed our understanding of the equation of state for dense matter. Does any of that translate to predictions about what forms on the other side of collapse, or does everything useful just get locked away the moment a horizon forms?

Genuinely curious how people here think about this boundary.

I love watching short physics videos, and particularly like Cox. He often brings up Einstein, who first published his theories over 100 years ago. Is it true that Einstein's theories have never been surpassed or found to be somehow inaccurate? (I do know that Hawking had some disagreement on whether things can escape black holes.) My background is in biology and medicine, and theories are updated on a pretty routine basis, certainly more than every 110 years. Have Einstein's basic theories ever been wrong? Is there thinking that he missed something obvious? Do you think he ever will be?

if you put three stars with equivalent mass in the center of a galaxy not (necessarily at the center just somewhere), what would happen?

Cause I know if you place two stars, they would theoretically dance around eachother and merge but is that still the case with three or heck multiple stars with similar mass, would it simply be chaos?

I was reading on the different stellar remnants and came across a tidbit of information regarding the formation of neutron stars. It was said that if a white dwarf overcomes the Chandrasekhar Limit, Degeneracy pressure is insufficient to prevent the further compression and reignition of carbon/oxygen nuclei and staring a thermonuclear runaway, leading to the total destruction of the white dwarf.

However, if the white dwarf is made of Magnesium and Neon, the white dwarf simply collapses and becomes a neutron star instead. Why does it do that, what about Magnesium and Neon prevent the white dwarf from being completely destroyed?

I'm currently a high school student working on a machine learning project involving strong gravitational lensing. I'm still new but going through some research papers and I'm wondering the real applications of gravitational lenses. Based on what I've seen, gravitational lensing has two main applications:

1. Seeing distant galaxies (like a huge magnifying glass)

2. Finding the mass of certain objects (stars, dark matter, etc.)

What I’m trying to understand better is why these things are useful in practice. For example, how important is gravitational lensing for actually discovering new galaxies or studying early galaxy formation? And when it comes to mass measurements, can we realistically map dark matter in galaxies or galaxy clusters using it, or measure the mass of specific objects in a meaningful way?

I’m also curious about how this connects to real research today. Are gravitational lenses mostly a supporting tool, or do they lead to discoveries we couldn’t make any other way? And how might machine learning fit into improving lens detection, mass modeling, or dark matter mapping (if anyone knows anything about this)?

Any help would be greatly appreciated, thanks!

Im 17 and in the uk, and as long as i gwt good predicted grades i should be applying to university next year, and am lookong for some good extracorriculars to put on my personal statement. Ive been to some Brian cox live shows and have some books lined up to read over the summer, as well as reading magazines like new scientist and nature every now and then.

Hi

I am a scientist, but have no idea about astrophysics and have a question I was hoping someone could help with.

In short, I am doing a breakdown of how science is portrayed in video games, and there is a scene in one game involving astrophysical research at a radio telescope. The short story is this:

A group of astrophysicists have been collecting data on geomagnetic events/aurora for years, but then the power went out, and "There goes years of post-doc data". They then start talking about getting the power back so that they can extract their data from the memory buffers.

First, while I assume astroresearch captures a ton of data, surely any experienced scientist has multiple copies of their data? Or is "memory buffer" something required in astrophysics due to the volume involved?

Second, in order to extract their data from the memory buffer, they have to recalibrate their telescope and align it to... whatever coordinates in the sky. But... why would you need to do that to retrieve your data from a memory buffer? To me this second part sounds more like they are collecting scanning data, not retrieving stored data in a memory buffer?

Does any of this makes sense to anyone?

Hi! I'm 25 years old, and I'm just now deciding to start college to pursue a degree in Physics with a concentration in Astrophysics. With that being said, I have not told anyone close to me what I'm deciding to take, because they'll disagree or try to change my mind about it. This is something I'm pursuing with a lot of passion, and I understand what comes with taking up something like this, but I feel like my family won't understand. Is the job market really as bad as they're making it out to be? Is this something I'm actually going to end up regretting? My whole heart is in this, but they have me doubting myself.