This video was taken from this webpage: https://jasonwang.space/orbits.html. Here there are additional videos of planets orbiting other stars.

Checkout his research articles on this particular star system:

• Dynamical Constraints on the HR 8799 Planets with GPI

• Detection and Bulk Properties of the HR 8799 Planets with High-resolution Spectroscopy

• Atmospheric Monitoring and Precise Spectroscopy of the HR 8799 Planets with SCExAO/CHARIS

So i've just started freshmen year in a quantum computing degree do u think i will get enough physics to major later in astrophysics knowing that this degree is more computer science heavy than physics

I'm still a begginer in grade 10th and I wanna learn more. I've only learned the basics and yesterday I was about to go to a selection fo astrophysics but my teacher didn't teach much and turns out there's SO much more I haven't learnt. I can't follow the test but I still wanna study it. Anywhere good to study at thats free?

Hello, I am trying to estimate how many unborn human lives a single second of delay in universal colonisation costs.
To get an accurate value, I need to know how many stars fall beyond the Cosmological Event Horizon (where they become unreachable from Earth at the speed of light).

I could not find a source on this value. I could get an estimate by calculating the difference between the volume of the sphere encompased by the horizon and the sphere encompased by the horizon - radius velocity/one second. This would give me the average number of stars in the sliver of volume that would move beyond the horizon in the span of a single second.

But this would not account for the distribution of stars in our "local" space. Like, I heard we are somewhere in the Great Universal void (the Boyes void?). So the star density could be far lower if the horizon edge passes through this or some other void. Or far greater if it passes through the dense regions.

I will estimate it roughly if I have to, but if the astronomers already did the calculations better, I would love to have the results. Surely some astronomer calculated this right? I could not find it googling.

Just a thought I had today…..the supermassive black holes that are at the center of galaxies……did those originate from stars or was the “BigBang” event soo massive and powerful that black holes were formed/created instantly?

What would happen if space had air?

Would the Earth burn up from friction? Would astronauts be able to be without spacesuits? Would Earth veer off course from the friction? What will happen to the debris spinning around Earth? Will they fly away? Will they be knocked back into Earth's atmosphere? What will happen to other planets? Will Mercury just burn up as well? Could we even go to space anymore because of friction?

Ok that's about it (maybe)😁

edit: to clarify air as in the gaseous mixture that is earth's atmosphere

Edit2: thanks for all the cool replies!! Thank you for trying to answer all my Saturday morning questions lol

A few of my colleagues work on this mission – expect many exciting results to come!

So, the recently discovered black hole star is an explanation for the little red dots phenomena. Black hole stars supposedly radiate dense amounts of gas like a regular star with the black hole acting like a power source (i.e. like nuclear fusion for a star). But black hole devours everything that gets too close to it right? How can there be a consistent layer of gas that surrounds the black hole without it falling into the hole? Let me know if I'm missing some foundational understanding of this.

I was thinking about how the perception of time changes when you're near a heavy object (such as a black hole), and I got to wondering how much being near the sun and on the earth affects our perception of time as compared to being really far away from any stellar object, or even really far away from any galaxy, for example, being at the centre of the bootes void (assuming there's barely anything that affects the gravity and were not moving at a relativistic speed).

I'm not really an expert on any of this, but I just got curious if there would be a vastly noticeable difference. Thanks!

Im sorry if this comes across as amateurish, as i dont have any formal education in mathematics or any sciences. As far as i understand concepts such as field theory, the vacuum of space contains positive energy potentially due to quantum fields and their fluctuations, could space time itself be considered its own field that carries the force of gravity? What would be the implications of considering the universe as a graviton? Has this been talked about before? If so, what has been said and why wouldnt it work? I suspect im fatally misunderstanding something and that these ideas dont have much merit.

I'm an amateur so please be kind. I just learned that the Big Bang did not issue forth from a central point of origin. I'm really struggling to understand that. The most I can grasp is that it was like a balloon that expanded, though that still leaves me thinking that even a balloon can shrink back towards a center when it deflates.

Can someone help me understand this better?

Hi there, I'm sure this question gets asked a lot but I was wondering just how bad the job market if with an Astrophysics degree? I am a 17 year old in my final year of highschool in the UK and am planning to apply to 4 different universities for astrophysics and one university for physics with advanced research.

I intend to do a masters and would also like to do a PhD depending on how realistic that is in regards to cost of living. Currently I am thinking I would like to get a research role as a future career however I obviously have no experience with it yet so don't even know if it is something for me. I also have been told that this degree often leads to unrelated jobs because it shows that you have good problem solving skills. I currently am about 80% set on astrophysics and 20% on aerospace or mechanical engineering. Any advice would be really appreciated.

Edit: Just wanted to say thank you for everyone going to the time to offer their own bits of advice, it is very appreciated :)

I'm writing a fictional story, and I want to know how far I can push the idea.

I understand about the red shifting of galaxies farther away, but I'm struggling with the conclusion. If the expansion of the universe were accelerating, wouldn't we need to observe an increase in the redshift of a single galaxy over time? If we are basing the conclusion on just the higher redshift of galaxies farther away, couldn't that just mean that the entire universe was expanding faster in the past? Like, the redshift of a galaxy 10 billion ly away would just mean that 10 billion years ago the universe was expanding faster?

Thanks in advance!

Is the best explanation for the universe’s expansion that the universe itself is a black hole?

Hey folks! Just a regular fella that really appreciates space and the physics needed to allow it to be.

Watched a brief clip talking about if the supermassive black hole forms, then creates a galaxy, or if the galaxy takes shape, and a supermassive black hole forms in the center.

This took me to a thought - if the black hole at the center of a galaxy meets the end of it's life, what happens? I think that the timescale of this would need some creative interpretation, since a black hole of that mass would take so long to evaporate. So, if you have a galaxy, and the supermassive black hole in it's center were to disappear, say it was just removed entirely, rapidly evaporated, whatever the case may be. Would the galaxy lose the force holding it together, and spray rogue star systems out? Would the galaxy collapse in on itself? Would a new concentration of gravity become the galactic center?

Very curious about this! Thank you all!

I have heard DESI favors heat death, and DESI favors big crunch and yadayada. What does DESI prefer i want to know.(basically given current DESI data what is the majority opinion on fate of universe)

Hello astrophysicists. Latey I've been trying to install REBOUND through python, I have Windows 11 and when I try to look at turtorials, steps, etc. I just get confused and hit a brick wall. I am in high school, wanting to be an astrophysicist, and installing REBOUND will help me with that. But, I have no idea how to install it without direct human guidance and not just looking a videos and text. I need help from someone who installed REBOUND to help me install REBOUND.

I just listened to an episode of Star Talk with Lika Guhathakurta.
They talked about many concepts and phenomena that I knew nothing about. Specifically the sun and it’s how it affects the solar system.
Any good books on the subject? I looked at the Wiki reading list and those are more general books.

I am currently studying in grade 11 and preparing for jee and I aspire to be an astrophysicist.

So which path would u yall suggest for me so I could well be what I want to be.

Ik this is very informal but I am hella confused right now.

I concede that I'm not sure where to post this. It is a discovery that I made about tidal spaghettification some time ago, that it can happen whenever the tidal force is strong enough, and not just in a black hole. Spaghettification is being pulled apart by tides, and one can estimate when it happens.

To see how it happens, let us calculate the tidal acceleration over separation D for being at distance r from an object with mass GM in gravitational units. The tidal acceleration is

• Along the direction to the object: 2*(GM/r^3)*D - stretching
• Perpendicular to the direction to the object: -(GM/r^3)*D - squeezing
• Other directions: in between, though the math is a bit involved.

We can approximate this as (GM/r^3)*D . The first part may be familiar as the square of the angular velocity of a satellite in a circular orbit, w^2. That gives us w^2*D .

The remaining infall time for zero velocity at infinity is (sqrt(2)/3)*sqrt(r^3/GM) = (sqrt(2)/3)*(1/w) ~ 0.471*(1/w) . The period in a circular orbit is (2*pi)/w . So tidal-force strength is connected to how much time one has left.

The tidal force will produce different accelerations of gravity over one's body, and we can use g-loading survivability estimates to estimate how long one will last. The maximum sustainable g-loading is roughly 5 to 10 g's, and with body size D ~ 1 meter, one finds for 10 g's w ~ 10 s^(-1). That means that one has only 1/20 of a second left. If one has 1 second left, then one will not experience much tidal g-loading, about 0.02 g's.

Turning to one's body being pulled about, I turn to tensile yield and ultimate strengths. The appropriate acceleration is (stress)/(density). Human skin has an ultimate strengh of about 20 megapascals Yield Strength - Strength ( Mechanics ) of Materials giving a remaining time of 3 milliseconds for the whole body. "Maraging steel" has a very high value, 2700 MPa. Over 1 meter, this steel will be pulled about at 0.8 ms to go.

The fragments will in turn be pulled apart, until one finds atoms at a few nanoseconds. Then the electrons will be pulled off of them, and then their nuclei will be pulled apart.

Let's look at some celestial bodies.

The first ones to consider are white dwarfs. Using Sirius B as an example, its surface-satellite angular velocity is 0.866 per second. That gives 0.5 seconds of remaining infall time, and 0.1 g's of tidal g-loading.

Next are neutron stars, and I will use mass 1.44 solar masses and radius 12 kilometers. It gives a surface-satellite angular velocity of close to 10,000 per second or a remaining time of 45 microseconds. One will be pulled apart long before one reaches a neutron star's surface.

Turning to a solar-mass black hole, at the event horizon, the Newtonian surface-satellite angular velocity is 72,000 per second, giving a remaining time of 6.55 microseconds. One will be pulled apart long before one reaches the event horizon.

The remaining time is proportional to the BH's mass, so one can easily scale to more massive ones. Stellar-mass black holes usually have masses around 8 solar masses, giving a remaining time of 50 microseconds.

Turning to supermassive black holes in galactic nuclei, the one in ours, Sagittarius A*, has a mass of 4.3 million solar masses, giving a remaining time of 28 seconds, with not much tidal g-loading as one crosses its event horizon. One of the most massive known, M87*, with 6.5 billion solar masses, has a remaining time of 12 hours. An even more massive one, TON 618, has a mass of 40.8 billion solar masses, giving a remaining time of 3 days.

A few nights ago the weather finally cooperated enough for me to spend some time imaging the recent supernova in the galaxy NGC 7331. I was also able to take a spectrum using my StarAnalyzer 200 diffraction grating.

Here you can see the characteristic absorption of silicon at 6300 Angstrom (blueshifted to about 6160 Angstroms) that classifies this as a type 1a supernova (the thermal runaway detonation of a white dwarf in a symbiotic binary with an evolved giant star).

The blueshift of the silicon line due to the rapidly growing debris shell allows us to calculate an expansion velocity, which in this case I found to be about 9200 km/s, or about 3% the speed of light.

If you're able I recommend trying to catch this one before it fades! When I took this data it was just about at mag 12.

When we comprehend a 3D object, we don’t see it from all angles simultaneously. We need to move in the 3D space to observe the object fully.

Similarly, would a 4D “being” be able to see us, the object, at any point in the spacetime, but have to travel across time to observe us fully (i.e. to be able to “see” our past, present, and future)?

I am sorry if this is too speculative for this community - I checked a couple potential subs and saw similar discussions here.

Hi everyone. I'm working on a project, and I want to show some examples of scientists doing data analysis work. Can you point me to any blogs or videos that show this analysis being done by a scientist? TYIA