Unanswered Questions
349 questions with no upvoted or accepted answers
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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 ...
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10
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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 ...
- 5,636
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Is there a standard deconvolution procedure to remove JWST's diffraction pattern yet? If so, would Arp 220 be a good candidate on which to try it?
Source: Webb captures the spectacular galactic merger Arp 220
Shining like a brilliant beacon amidst a sea of galaxies, Arp 220 lights up the night sky in this view from the NASA/ESA/CSA James Webb ...
- 30.3k
7
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Can terrestrial infrared telescopes see through clouds or haze, sometimes at least?
My answer to Could UV-A imaging sensor reasonably see a total eclipse in progress through clouds? suggests that while clouds blocking visible light observation of the (partially) eclipsed solar disk ...
- 30.3k
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Angular resolution of naked eye at night; type of vision used
It appears that most sources quote the angular resolution of the eye as 1', regardless of day and night.
For instance,
Naked eye
Seconds of Arc and the Unaided Eye
However, the following websites give ...
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What's the largest angle that light has been "seen to bend" by gravity? (of one object by a separate object)
Gravitational lensing is everywhere! because it falls off so slowly with $r$:
$$\Delta \phi \approx \frac{4GM}{c^2r_0}.$$
That's the first order term. For a nice derivation see Viktor Toth's The ...
- 30.3k
7
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Get the expression of probed volume between 2 redshifts
1) I can't manage to find/justify the relation (1) below, from the common relation (2) of a volume.
2) It seems the variable r is actually the comoving distance and not comoving coordinates (with ...
CommunityBot
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6
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How was the axial tilt of planets measured?
https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies gives the axial tilt of all planets with two decimal precision, but how and when were they measured so precisely ?
I guess it's "easy&...
- 30.3k
6
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How far have stars been seen beyond the center of the Milky Way?
What lies near the center of the galaxy is of great interest and in recent times the motion of dozen(s) of stars at the center of our galaxy orbiting around Sgr A* have been measured in great detail. ...
- 30.3k
6
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510
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Could non-supernova carbon, oxygen, or silicon flashes be observed?
I was reading about the helium flash, the short but sudden onset of helium fusion in certain red giant stars. As I understand, the upper (nondegenerate) layers of the star absorb the energy as they ...
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Is there a noob-friendly website/app for tracking a astronomical body's apparent movement over time?
As I walk home along my road most nights in winter, I see the Moon and one-or-more planets.
Unsurprisingly, over the last 2 months, if it's been the same planet and it (and the Moon) has been in ...
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513
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How far away must galaxies be before current telescopes can no longer measure how quickly they are rotating around one another or internally?
What is the distance limit and does it depend on the size of the galaxy and on noise and interference from gas clouds and our own Milky Way?
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Do all the accretion disks around a compact object (black hole or neutron star) emit astrophysical jet outflow?
Do all the accretion disks around a compact object (black hole or neutron star) emit astrophysical jet outflow? I mean is it mandatory for a jet to be emitted from an accretion disk?
If so, then why?
...
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Positional astronomy - Speed of the sun in sky
Let $\vec{r}$ be the position of the Sun in the sky, from Earth. How could I estimate the magnitude of $d\vec{r}/dt$, to measure the rate of change in time of the arc it traces? I suppose it would be ...
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A new (radio) neutrino telescope in Greenland?
I just stumbled upon ScienceMag news from July 14th, 2021 which says:
By placing hundreds of radio antennas on the ice surface and dozens of meters below it, they hope to trap elusive particles known ...
- 5,636
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What about the U planet?
In 2014 and 15, an object called U has been detected by the ALMA in Chile, considered likely to be a super-Earth at 300 AU, among other options. Is it located where the hypothetical super-Earth ...
- 1,538
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Explain as simply as possible how the Sunyaev-Zeldovich (SZ) effect is used to estimate the Hubble constant
The Sunyaev–Zeldovich effect (SZ effect) is useful in determining the Hubble constant because it is independent of the cosmic distance ladder. This effect occurs when CMB (cosmic microwave background) ...
- 30.3k
5
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Significantly blueshifted Lyman-$\alpha$
Lyman-$\alpha$ line in galaxies is notably known to show a double peaked profile, mainly due to its scattering in a moving medium, see e.g., the very recent Matthee et al. 2021, The X-SHOOTER Lyman-α ...
- 30.3k
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What are some good books/online resources for astronomy problem sets?
I am currently studying for the international olympiad for astronomy and astrophysics (the syllabus can be found here: https://www.ioaastrophysics.org/syllabus/). I am currently using Carroll Ostlie's ...
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What are the deciding optical factors between a refractive and reflective space telescope optics as a function of aperture? (visible light)
Reading Yale News' Lighting a path to Planet Nine:
To detect objects that are otherwise undetectable, Rice and Laughlin employ a method called “shifting and stacking.” They “shift” images from a ...
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Are occultation observations used/useful for orbit determination?
The IAU Minor Planet Center lists $(486958)\space 2014 \space MU_{69}$ "Ultima Thule" as having an uncertainty parameter of 2, based on the observation arc of 851 days, from its discovery in 2014, to ...
- 30.3k
5
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Strength of core-envelope coupling in stars
For a star with a given Zero-Age Main Sequence (ZAMS) mass, as a function of metallicity how strongly is the star's core coupled to its envelope?
I understand that the core-envelope boundary is only (...
- 4,533
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56
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In the JPL small body browser, why is uncertainty on absolute magnitude "N/A"?
In the JPL small body browser, orbital elements are all provided with uncertainties and even a covariance matrix, such as for 2013 LA2. Very good. But underneath, the absolute magnitude is reported ...
- 2,233
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Infrared telescopes, magnitude and observations
Currently 22-23 magnitude could be the limit to make a spectrum for ground based 10m class telescopes, 21-22 magnitude may be easy for them.
4m class telescopes could possibly handle 20 magnitude, I ...
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4
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66
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What are the technologies needed to make deep space LIDAR competitive with RADAR? Any plans for tests, prototypes or "pathfinder" systems?
ProfRob's answer to Would it be practical to map out the Kuiper Belt and Oort Cloud via Radar? gives us a "sobriety check" on the idea. Citing an example of a 1 million watt transmitter at ...
- 30.3k
4
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Can a meteor streak exhibit different colors denoting presence of more than1 element?
A meteoroid's elemental composition can be determined by the color it exhibits while burning in the earth's atmosphere which we also call a "meteor". However, is it possible that a meteor ...
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Just how resonant is the "resonant sextuplet of sub-Neptunes transiting the bright star HD 110067"?
The November 29, 2023 arXiv preprint A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067 constructs a resonant chain of orbital periods based on mean motion resonances (MMRs) and ...
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4
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Do the discs of observed solar systems have random orientations?
Is there any bias in the orientation of solar systems?
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44
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What special auxiliary equipment / modeling are needed for ground-based sub-milliarcsecond astronomy?
I'm not asking about the astronomical equipment itself. I'm asking about the auxiliary equipment and modeling needed to enable the primary astronomical equipment to work properly at the sub-...
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4
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553
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How to measure the latitude of the moon?
In the geocentric solar ecliptic (GSE) system of coordinates, the position of the Moon is described by its longitude and latitude. The former is, with great accuracy, the angular distance between the ...
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