One example, Canis Majoris has a radius of about 1420 solar radii. But its mass is roughly 17±8 times the mass of the Sun and therefore an average density of 5.33 to 8.38 mg/m3. “It is over 100.000 times less dense than Earth’s atmosphere at sea level.”
Only once you get to 10+ solar masses does radiation (light) pressure begin to become significant, and at 50+ solar masses is when it dominates and the atmosphere is held up by the momentum of light.
It needs a core generating energy through fusion, which has density requirements, for what it’s worth.
Depending what kind of reading material you're looking for (e.g. high level details or mathematically/jargon dense papers) look for things discussing "Rosseland optical depth" and "grey atmosphere approximation".
At a high level, the common convention is to define the radius by finding where the optical depth is 2/3 when using Rosselands clever way of calculating a weighted mean of the opacity from that layer in the star to space across different wavelengths of light. 2/3 being a clever derivation from Eddington where, in an idealized model of a star, that's when the actual temperature of the star should equal its blackbody equivalent temperature.
Pedantically, this distance to the point of equality is an ever so slightly different value than the "distance from the center where there is a 50% chance a photon traveling directly outward will escape the star without another interaction" rule of thumb (in the same idealized grey model). Practically, that the difference is so small is why it's a fantastic rule of thumb explanation.
That's nuts. How on earth does fusion happen at that density? Is there a denser core that actually fuses, and the outer fluffy bits just glow from the inner heat?
As an example, I pulled the stats for an electric locomotive. 19x3x4.4 meters, mass 90 metric tonnes. That's an average density of about 1/3rd of water.
An example being the number of stars in the (observable) universe which ranges from 10^22 to 10^24 stars...a variance of 100x (or ~10,000%)!!! https://www.esa.int/Science_Exploration/Space_Science/How_ma...
“We predict a year, so it’ll take anywhere between 8 seconds and 24 months!” AND IT WORKED???
https://en.wikipedia.org/wiki/Quasi-star#Formation_and_prope... (Caption: "Size comparison of a hypothetical quasi-star to some of the largest known stars")
PBS Space Time: https://www.youtube.com/watch?v=FMdrD_jcYgE
love those channels
Is there anything behind these objects they could lens?
To me it's an interesting coincidence, thought description of these objects baffles me.
Unless the universe is recursively within itself: the black hole stars have black holes within them that also exit at the big bang. But then so do all other smaller big bangs we see: exact same exit point and coincidentally, the same moment in time.
Oh, and there is a beautiful symmetry here: only one white hole exists.
One beginning, many endings. It's armchair philosophy but fun to imagine.
Fuel for a Big Bang, if you can imagine. A universe within itself.
The article says they're sucking up gas though so I don't know. The arrow of time is weird. It would feel elegant to me, but I'm way out of my league.
The imagined scenario only works if you picture all black holes 'twisting time' towards its beginning.
Sort of like recursion, or a tesseract, where there's one beginning and many endings.