А neutron star and a photon sphere

In summary, the conversation discusses the existence of photon spheres and how they can only exist around extremely compact objects, such as a black hole or a neutron star. There is a question about whether a neutron star can have a photon sphere due to its increasing mass and decreasing radius. The conversation also mentions the Oppenheimer-Volkoff limit and its potential inconsistency with the existence of a photon sphere around a neutron star. A reference is provided to a paper that suggests certain equations of state could allow for a neutron star to have a photon sphere.
  • #1
daggab
3
0
Wikipedia(https://en.m.wikipedia.org/wiki/Photon_sphere):
'This equation entails that photon spheres can only exist in the space surrounding an extremely compact object (a black hole or possibly a neutron star)'
But how can a neutron star?
I have a doubt because
1. When а mass of а star increases, radius decreases.
2. The radius of the most massive NS exceeds the schwarzschild radius.
3. We know Oppenheimer-Volkoff limit roughly. It is not known exactly.
I suppose that the existence of such neutron stars is questionable.
Is it correct?
 
Astronomy news on Phys.org
  • #2
daggab said:
We know Oppenheimer-Volkoff limit roughly.
Hi daggab:

The Wikipedia article text indicates that at a neutron start of radius r,
rs < r < (3/2) rs,​
could have a photon sphere. Are you saying that the Oppenheimer-Volkoff limit is inconsistent with this?

Regards,
Buzz
 
  • Like
Likes daggab
  • #3
If you follow the link to reference [1] in that Wikipedia article, it links to a paper "Properties of ultracompact neutron stars" which mentions that certain equations of state would allow a neutron star to be less than 1.5 times the Schwarzschild radius and hence have a photon sphere.
 
  • Like
Likes daggab

1. What is a neutron star?

A neutron star is a celestial object that is formed after the core of a massive star collapses under its own gravity during a supernova explosion. It is extremely dense, typically with a mass greater than that of the Sun but a radius of only a few miles. Neutron stars are composed almost entirely of neutrons and they have incredibly strong magnetic fields.

2. How is a neutron star different from a regular star?

Neutron stars are significantly different from regular stars in terms of their size, density, and composition. While a regular star is made up of mostly hydrogen and helium, a neutron star is composed mostly of neutrons. Neutron stars are also much smaller in size compared to regular stars, with a radius of only a few miles compared to the Sun's radius of about 432,000 miles.

3. What is a photon sphere?

A photon sphere is a theoretical region around a compact object, such as a neutron star, where photons (particles of light) can orbit in a perfect circle. This orbit is possible because the intense gravitational force of the compact object bends the path of light, causing it to follow a curved path around the object.

4. How does a neutron star create a photon sphere?

The intense gravitational force of a neutron star is responsible for creating the photon sphere. As light nears the neutron star, it is bent and pulled towards the star, causing it to orbit around in a circular path. The closer the light gets to the neutron star, the stronger the gravitational force and the tighter the orbit becomes, creating the photon sphere.

5. Why are neutron stars and photon spheres important in astrophysics?

Neutron stars and photon spheres are important in astrophysics because they allow us to study and understand the effects of extreme gravity. These objects provide valuable information about the nature of space and time, as well as the behavior of matter under extreme conditions. They also play a crucial role in our understanding of the universe and its evolution.

Similar threads

B If Quark stars exist why do Neutron stars become Black holes?
    • Astronomy and Astrophysics
Replies
17
Views
4K
B Stars massive enough to evolve into black holes
    • Astronomy and Astrophysics
Replies
5
Views
1K
B Galactic Collision Creates a Ring of Black Holes and Neutron Stars....
    • Astronomy and Astrophysics
Replies
1
Views
2K
I SN 2019hgp, new type of supernova? Wolf-Rayet progenitor?
    • Astronomy and Astrophysics
Replies
1
Views
859
Neutron Star Collapse: Q&A on Physics and Observation
    • Astronomy and Astrophysics
Replies
9
Views
3K
Neutron Star Collapse: Upper Limit & Physics Explained
    • Astronomy and Astrophysics
Replies
2
Views
2K
I What happens when a Neutron Star forms a Black Hole?
    • Cosmology
Replies
17
Views
1K
A Dark Matter Accretion Disk for Black Hole (Neutron Star)
    • Astronomy and Astrophysics
Replies
1
Views
1K
Stellar-mass black hole formation sequence
    • Astronomy and Astrophysics
Replies
30
Views
4K
A Falsifications and constraints due to GW measurements
    • Astronomy and Astrophysics
Replies
19
Views
4K

Hot Threads

Recent Insights

Back
Top