Questions tagged [particles]
The particles tag has no usage guidance.
20
questions
1
vote
1
answer
80
views
Why are WIMP dark matter particles, if Majorana-like, expected to annihilate upon contact? But not neutrinos?
I have heard a lot recently about so-called 'dark stars'; stars that are formed with the help of the gravitational pull of dark matter, or perhaps entirely from self-annihilating Majorana-type dark ...
- 4,789
3
votes
1
answer
116
views
When two galaxies with dark matter halos merge do they provide evidence for fermionic or bosonic dark matter?
If dark matter is made from fermions these should collide and cause dark matter to become denser in some places than others Bosons wont collide in this way so there should a different effect .So is ...
user50918
5
votes
2
answers
822
views
Hubble expansion rate and reaction rates
I've come across sentences like
...the reaction
rates (the number of reactions per particle per unit time) must
be larger than the cosmic expansion rate $H(t)$ in order for the
particles to maintain ...
- 427
4
votes
0
answers
36
views
Total scattered flux and polarization for a ring of dust particles close to a star
I have an important problem and maybe some of you can help me with the following question:
I have a mathematical expression for the total scattered flux in Jansky and the total linear polarized flux (...
- 41
1
vote
0
answers
52
views
How much does the Higgs field contribute to the energy of empty space?
The Higgs field was not spontaneously broken when the universe was young and hot (like I am not...:)). At the very high temperature that existed back then, the Higgs' energy of the Higgs field was non-...
1
vote
1
answer
230
views
How can we know the density of particles in interstellar or intergalactic space and could that density form dark matter?
It is assumed that the density of particles in the empty space between stars or galaxies is extremely low. But how do we know this density? The space surrounding the Sun is contaminated by cosmic ...
3
votes
1
answer
118
views
Directionality of solar flares
I have read a number of articles about Coronal Mass Ejections (CME) and solar flares and I’m trying to establish how directional the radiation from them is.
I am aware that radiation from these solar ...
- 259
4
votes
1
answer
230
views
Could Sgr A* be a core of dark matter instead of a supermassive black hole?
A recent paper (related news) shows that Sgr A* at the center of the Milky Way galaxy could be a dark matter core, instead of a supermassive black hole, according to their calculation using the ...
- 593
1
vote
0
answers
37
views
Astrophysical particle spectroscopy; narrow-line particle sources (charged or uncharged) for things other than photons? Have any been detected?
Is Cosmic Ray Astronomy a thing?
Is there an equivalent of the red shift effect for cosmic rays?
have got me thinking and under this answer I've commented:
That's a good point; there aren't as many ...
- 31.7k
2
votes
0
answers
75
views
How do we know or predict which particles were present before Big Bang Nucleosynthesis occurred?
I'm reading Carroll and Ostlie's "An Introduction to Modern Astrophysics". In the BBN section, they describe that the universe contains a mixture of photons, electron-positron pairs, and ...
- 1,111
3
votes
1
answer
96
views
What consequences does a positive muon anomalous magnetic moment have for astronomy?
On April 7th, 2021, the muon $(g-2)$ collaboration published Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm, a result which made it to standard news, partly under headlines ...
- 5,504
0
votes
4
answers
362
views
Absorption of light by matter
What determines whether or not photons can be absorbed by matter? Intuitively, the answer is that a charged particle can absorb photons (whether it's positively or negatively charged), and neutral ...
- 299
4
votes
1
answer
97
views
What are the sources of antimatter particles in the magnetosphere?
The PAMELA instrument detected antimatter particles in the Earth's magnetosphere. What are the sources of these particles?
The answer to Source of high energy cosmic particles outlines the sources ...
- 1,009
4
votes
1
answer
455
views
Have there been studies of "old photons" to see just how constant things like Planck constant has been?
The question Are photons aged? and answers therein have got me thinking:
I vaguely remember hearing something about experiments where "old photons" were collected by large telescopes from very ...
- 31.7k
9
votes
1
answer
172
views
What is happening with these solar particles detected near the Sun that is so newsworthy?
Phys.org's Team identifies low-energy solar particles from beyond Earth near the Sun links to the open access ApJ article Properties of Suprathermal-through-energetic He Ions Associated with Stream ...
- 31.7k
9
votes
1
answer
361
views
How are neutrinos produced in blazar jets?
I was watching the press release about measuring neutrinos and gamma rays from a distant blazar. One of the presenters mentioned that the neutrinos are associated with very high energy protons caught ...
- 448
36
votes
5
answers
6k
views
How exactly does Hawking radiation decrease the mass of black holes?
From what I understand so far, when one of virtual particles crosses the event horizon and the other does not, they can not annihilate each other. The latter wanders off into the universe (btw, is it ...
- 601
1
vote
1
answer
182
views
Possible to use tachyons to explore black hole?
I read on a Wikipedia article lately that tachyons are theoretical particles which always travel at or above the speed of light. That means that when one passes us, we see two images, a blue shifted ...
- 1,862
1
vote
1
answer
322
views
What could be past the particle horizon?
Forgive any kind of "dumb" question I may ask as this is a new interest of mine and I know it's purely hypothetical.
If one were able to surpass light speed and the expansion of space to go beyond ...
- 113
21
votes
1
answer
475
views
Dark Matter Particle Candidates
Dark matter appears to dominate the matter component of the universe as compared to luminous, or baryonic, matter. Though it does not interact electromagnetically (it doesn't absorb, scatter, or emit ...
- 6,013