Unanswered Questions

1,016 questions with no upvoted or accepted answers
16
votes
1answer
370 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 ...
14
votes
0answers
512 views

How to determine scalar-to-tensor ratio r from CMB polarization spectrum?

CMB polarization spectrum can tell us about the primordial scalar and tensor perturbation. By analyze B and E mode angular spectrum power spectrum and temperature power spectrum we can determine the ...
12
votes
0answers
93 views

The compatibility of the Grand Tack hypothesis with the “core-warping impact” theory of Jupiter's diffuse core

In recent years, the Juno mission revealed that Jupiter's core was much more diffuse than astronomers had expected. One theory is that "within a few million years" of its formation, Jupiter ...
11
votes
0answers
270 views

What fraction of a star's hydrogen store will be fused over its lifespan?

A main sequence star will fuse some of its hydrogen, but not all. In massive stars ($>1.5M_\odot$) the core is convective but the rest of the atmosphere radiative and hence does not mix much: as it ...
11
votes
0answers
127 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 ...
10
votes
0answers
231 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
0answers
225 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 ...
9
votes
0answers
83 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
0answers
83 views

Determining 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 ...
8
votes
0answers
160 views

How many meteorites have been found some place other than Earth? Where is an authoritative list maintained?

Backgound: After seeing this tweet by astronomer Kacper Wierzchoś about our not-so-new but at least newly-discovered "mini-moon" I scrolled down and saw the tweeted image below. The object ...
8
votes
0answers
69 views

What are the 4 candidates for Planet Nine reported in 2017?

From Wikipedia Planet Nine#Citizen science: In April 2017, using data from the SkyMapper telescope at Siding Spring Observatory, citizen scientists on the Zooniverse platform reported four ...
7
votes
0answers
86 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 ...
7
votes
0answers
109 views

What alternative facilities would be available in the event of JWST being destroyed?

Unfortunately, space launches can and do go wrong. Suppose that after all the delays and budget overruns, the launch of the James Webb Space Telescope fails and the telescope becomes a cloud of very ...
7
votes
0answers
80 views

Is the Ordovician meteor event detectable in the lunar cratering record?

Approximately 468 million years ago there were a large number of L-chondrite meteorites falling to Earth. This is called the Ordovician meteor event and was probably the result of a large collision in ...
7
votes
0answers
116 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 ...

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