Unanswered Questions

1,358 questions with no upvoted or accepted answers
18 votes
1 answer
647 views

How small can a spiral galaxy be?

The smallest observed spiral galaxies I can find are NGC 2976 and NGC 4605, both with a diameter of 20 kly, but I don't have anything like an exhaustive source to search. I've also found a mention ...
13 votes
0 answers
308 views

Planning to revisit Arthur Eddington's experiment from 1919

As the fateful day draws closer, the United States will host a celestial event that comes once in three generations. I plan to witness this first hand at the exact center of greatest eclipse. In the ...
12 votes
0 answers
282 views

What is the limiting abundances of elements at the end of the stelliferous era?

Is there any reputable published source on expected elemental abundances at the end of the era of stellar fusion? I am here interested in the contents of galaxies; much of intergalactic gas will be ...
10 votes
0 answers
165 views

Estimating the tangential and cross component of the galaxy's shear using Gnomonic projection

I would like to know how I can estimate the tangential and cross component of the galaxy's shear using Gnomonic projection of the right ascension and declination the galaxies relate to the center of ...
9 votes
1 answer
195 views

Error propagation methods for orbit parameters

Recently I've encountered an article in our local astronomical popularization magazine. It is about a well known task of Sgr A*-black hole's mass estimation. The article is written as a step by step ...
9 votes
0 answers
101 views

How can maser emission be unpolarized?

I was reading that: However, unlike Galactic sources such as W3(OH), the emission is unpolarized and the 1667 MHz line is stronger than the 1665 MHz line. but how is this possible? Does not the ...
8 votes
0 answers
116 views

How well conserved is etendue in extreme gravitational lensing scenarios?

This excellent answer to Could dark matter exist in the Universe in the form of sufficiently dense objects? includes the following image and description: Light from the background galaxy circles a ...
8 votes
0 answers
117 views

Spatial wind speed distribution on Mars using dune shapes?

As a fan of exometeorology (the study of atmospheres of other planets), I scanned through a whitepaper Measuring Mars Atmospheric Winds from Orbit which says Measurements of Mars atmospheric winds ...
7 votes
0 answers
91 views

How are the occurrence and nature of micrometeoroid impacts on JWST optics identified?

There are been recent news about a larger-than-expected micrometeoroid impact on the James Webb Space Telescope's optics. Apparently this was one of several impacts that have already been observed. ...
7 votes
0 answers
104 views

Color index B-V of the dimming Betelgeuse

Using AAVSO light curve generator I have plotted V and B magnitudes of Betelgeuse in the past 150 days to see trend of B-V color index. If dust would be the cause of the recent drop in the star ...
7 votes
0 answers
161 views

Why would a black hole have a disk, but not emit x-rays?

There's a recent paper in Nature about LB-1, a B-class star orbiting a massive black hole. I don't understand how these two parts of the paper can be reconciled. On page 2, the authors argue that the ...
7 votes
0 answers
126 views

Water vapour in space

This question is inspired by, but different from, What happens if an ice cube is left in space? Mark's accepted answer says "…if you stick your ice cube out in the Oort Cloud, it'll grow: the mean ...
7 votes
0 answers
465 views

What are the analysis steps in taking raw data from Kepler to a planetary system determination

I wish to get a concise list of the analysis steps required to take raw light data from a Kepler data set of a star through the steps needed to get to an analytical determination of the existence of a ...
7 votes
0 answers
111 views

Why can primordial tensor perturbations of the CMB be ascribed to gravitational waves?

Why can primordial tensor perturbations of the CMB be ascribed to gravitational waves? Is this attribution unique, or are there other mechanisms that could lead to the excitation of tensor modes? In ...
6 votes
0 answers
98 views

How are the aberrations seen in early JWST images corrected?

I found this image on space.com and it can also be found in NASA's JWST blog. This is one step in the process of aligning the 18 mirrors on JWST. A single relatively-isolated star has been selected. ...

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