Unanswered Questions
113 questions with no upvoted or accepted answers
1
vote
0
answers
15
views
cross-matched SDSS-WISE catalog
Please where can I find cross-matched SDSS and WISE dataset for a machine learning project?
(Galaxy-star-qso classification task)
1
vote
0
answers
119
views
Determining Time Based on Arc Seconds
So our arc day starts at 20°41'32 which is midnight (0:00) and ends 24 hours later at 21°42'42. According to my calculations it traveled 0 degrees, 59 minutes, and 30 seconds or 3570 arc seconds in 24 ...
- 2,339
1
vote
0
answers
24
views
What would be the new Equation of motion if the magnetic field's origin is shifted from the origin of a co-rotating spherical polar coordinates?
The equation of motions due to the dipole magnetic force of a planet in a frame corotating with the planet and origin at the centre of planet assumed to be sphere components wise are given as below:
\...
- 145
1
vote
0
answers
37
views
What is value of charge by mass ratio (q/m) for a spherical micro charged particle with surface potential 6 volts in S.I units and in e/amu units?
In Liu and Ip (2014),The Astrophysical Journal, 786:34 (8pp), the value of q/m is derived as follows :
"for a dust grain with radius 'a', from $\phi = \frac{4\pi q}{\varepsilon_0 a}$ we have $\...
- 145
1
vote
0
answers
99
views
Formula for "gravity assist"
I am familiar with the concept of "gravity assist" by which a space probe or other object, passing near a moving planet, can pick up some of the planet's orbital velocity.
I presume that ...
- 511
1
vote
0
answers
94
views
Is there such a thing as a map that shows the current (not observed) positions of celestial objects?
As I understand it, maps of the sky and three-dimensional maps of the universe all show the observed positions of celestial objects.
Are there any maps that show our best guess at their current ...
- 111
1
vote
0
answers
219
views
Typical astronomical and astrophysical problems in various programming languages
As a rule, work in the field of observational astronomy and astrophysics requires knowledge of such programming languages as: C/C++ and the principles of OOP, MPI, CUDA. Sometimes additional ...
- 853
1
vote
0
answers
107
views
What exactly IS a "Domain Wall"?
A Domain Wall is an "topological defect" and a 2-dimensional singularity. They are widely theorized to exist throughout the universe, but none have been detected yet. I'm having trouble ...
- 125k
1
vote
0
answers
95
views
Stellar structure equations - mass continuity
Out of the four stellar structure ODEs, I would like to understand why the mass continuity equation was named this way. It reads
$$ \frac{dm}{dr}=4\pi r^2\rho \tag{1} $$
and I understand what it means,...
- 11
1
vote
0
answers
56
views
How does the entropy diffusivity changes with radius in the Sun?
Could you please explain - How does the entropy diffusivity changes with radius in the Sun?
As far I know, In the convection zone, the entropy diffusivity increases as the temperature and density ...
- 11
1
vote
0
answers
24
views
what does it mean to have momentum suppressed cross section
What does it mean to have momentum suppressed cross section and zero momentum transference in direct and indirect detection of dark matter
- 11
1
vote
0
answers
51
views
Calculating the angular momentum of stars from Gaia archive (Gaia DR3)
I am trying to calculate the angular momentum for a subset of stars from Gaia DR3. I have scanned the available fields in their database and could only find out the below fields that specifies the ...
- 163
1
vote
0
answers
105
views
Why do most astrophysicists believe the cosmic microwave background (CMB) provides the best evidence for dark matter? What, exactly, IS that evidence?
I frequently read that the cosmic microwave background contains the best overall evidence for the existence of dark matter, and conversely against alternative gravity theories like MOND.
However, I ...
- 5,177
1
vote
0
answers
101
views
Find Periodicity in Lightcurve Using Lombscargle Periodogram(Astropy)
How to find the Nyquist factor for unevenly sampled data like here.https://github.com/jakevdp/PracticalLombScargle/blob/master/figures/LINEAR_Example.ipynb ? I have time binned for 5 mins. I mean for ...
- 21
1
vote
0
answers
36
views
Curated dataset of labelled images for NEO detection
I am looking for a dataset of images. Some images should contain NEO's (1 or more), others should not. With the dataset, there should also be an accompanying file, of which should contain 'labels'. ...
- 171