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631 questions with no upvoted or accepted answers
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16
votes
0answers
503 views

Is it “weird” that all disc galaxies rotate once every billion years?

In a recent paper (Cosmic clocks: A Tight Radius - Velocity Relationship for HI-Selected Galaxies by Meurer, et al.), it was noted in the conclusion that: [This] implies a constant orbital time of ∼...
15
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0answers
694 views

Terrestrial Exoplanet Skies – I've Built a Visual Sky Chart. Is it Accurate?

I'm an artist (and science enthusiast) and I've been trying to find a comprehensive resource that would help me clearly identify likely sky colors (as perceived by human vision) for exoplanets that ...
9
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0answers
459 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 ...
8
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0answers
73 views

How actively is Deep Learning being used in exoplanet identification?

Papers, like this one from Google, show that Deep Learning and Machine Learning are effective in detecting exoplanets from luminosity data provided by telescopes like TESS or Kepler. These models ...
8
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0answers
212 views

How would astronomical seeing on Mars differ from that on Earth?

Astronomical seeing is the limiting factor for the resolution of all but the smallest Earthbound telescopes. Source Stunning advances in adaptive optics (along with it's predecessor speckle ...
8
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0answers
192 views

What are Kepler's laws (as he wrote them)?

There are of course many, many sources that quote Kepler's laws of planetary motion. This is preventing me from finding out what I really want to know: which is - what are Kepler's laws as he wrote ...
8
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0answers
186 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 ...
8
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0answers
101 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 ...
7
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1answer
198 views

Breakthrough Starshot; could we detect similar probes flying by Earth?

If extraterrestrial civilizations were sending probes by Earth similar to our plans for Breakthrough Starshot (where the probes are only a few meters in diameter and will be moving at up to 0.2c when ...
7
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1answer
176 views

First observation that the Sun and Jupiter (and friends) move around a common barycenter?

Answers to the question How did Kepler determine the orbital period of Mars? describing careful observations centuries ago got me thinking. What was the first analysis of observations that directly ...
7
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194 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 ...
7
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0answers
196 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 ...
6
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90 views
+50

What do the fusing 'onion layers' of a pre-supernova star look like to scale?

I'm sure we've all seen the diagrams of various layers of element fusion from hydrogen to silicon in a star that's just about to go supernova. (Picture from courses.lumenlearning.com) I suspect ...
6
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85 views

Is Spherical Astronomy by W. M. Smart a good book on positional/spherical astronomy?

I'm a math undergrad, but I'm really interested in learning positional astronomy; However, the only well-referenced textbook I've come up with is Spherical Astronomy by W. M. Smart. I would like to ...
6
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0answers
85 views

Can the period of the planet transit across the sun be calculated in the same way the eclipse year is?

I read from Wikipedia$-$Eclipse cycle that the eclipse year, which is the period of Earth's hitting a certain node of its orbit around the sun, that is, the ecliptic, and the moon's orbit around Earth,...
6
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0answers
87 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 ...
6
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0answers
89 views

Do mixed type remnant collisions produce anything interesting?

The recent detection of a binary neutron star inspiraling and colliding raises an interesting question in my mind. Type Ia supernovae are believed to be caused by white dwarf/regular star pairs and/or ...
6
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0answers
99 views

What is the farthest reported distance from observer from which a solar system body has occulted a star?

I originally wrote "...farthest distance from Earth..." but changed to "observer" in case the occultation was observed from a space telescope. It may not matter much but I didn't want to over-...
6
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0answers
69 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 ...
6
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0answers
167 views

Is the wind's intensity on Mars similar to Earth?

I've read that in Mars' poles, the winds can be as fast as 400 km/h, when the poles are exposed to sunlight because the frozen $CO_2$ sublimes. I know that the Martian atmosphere is much thinner than ...
6
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59 views

Has the Kepler data been examined for light curves due to phase changes of non-transitting hot Jupiters and other?

I found this article http://www.epj-conferences.org/articles/epjconf/pdf/2011/01/epjconf_ohp2010_03005.pdf from 2011 announcing that two dozen secondary eclipses of "hot Jupters" have been seen in ...
6
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116 views

Semimajor axis variations in co-orbital moons

I've been playing with simulations of co-orbital bodies similar to Saturn's moons Janus & Epimetheus- horseshoe orbits where the two bodies are of comparable mass- and I'm seeing some very odd ...
6
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1answer
281 views

The most feasible hypothesis about Theia

The formation of the Moon had many hypothesis over the years, most of them involving a Mars-sized body called Theia, which presumably collided with the Earth. But even within the Theia hypothesis, is ...
5
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43 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 ...
5
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0answers
96 views

Is there any difference between M87's image and predictions?

Today, the EHT released (somewhat blurry as compared to simulations)images of M87 blackhole. Did the image contain anything which might lead to a correction to General Relativity or were all the ...
5
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0answers
62 views

Can anyone explain this odd Galactic dust filament near the LMC?

Perusing the Planck 353 GHz polarisation Aitoff projection I noticed an apparent magnetically driven dust filament rising abruptly from the Galactic ß-field in the Chameleon-Mensa S polar region. It ...
5
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0answers
66 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 ...
5
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0answers
143 views

Is Optical VLBI theoretically feasible? If not why not?

There are plenty of optical interferometers in use with baselines of up to maybe 1km. As far as I can find out, they all work by directly collecting the light at all the telescopes, using mirrors to ...
5
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0answers
56 views

How open is China in sharing data from the Chang'e 4 mission?

It's really good to see that man (well, machine) has gone back to the moon again. Chang'e 4 is studying potential mantle material from the lunar depths and will be conducting radio astronomy in ...
5
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0answers
67 views

Does the orbital decay of Triton affect Neptune's rotation?

Just a quick question regarding Neptune. Because Phobos is spiraling in towards Mars, Mars' rotation speeds up. Does the same thing happen with Neptune's rotation?
5
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0answers
47 views

What is the relation between the saros (18 years, 11 days, 8 hours) and the period of lunar nodal precession (18.6 years)?

I am wondering. I am sure that they are related. How can we derive one from the other?
5
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0answers
97 views

Which astronomer set his beard on fire because he left the cap off his telescopes finder?

There is a famous story of an experienced astronomer setting his beard on fire because he left the cap off his telescopes finder. I know it's said to be true of Galileo, but I thing it's relatively ...
5
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0answers
177 views

Gravitational eddies across the galaxy?

I read about natural gravitational eddies that travel in a wave that black holes have. They also have a strong magnetic field. Does those eddies follow magnetic field lines of the rotating black hole? ...
5
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0answers
85 views

Need help understanding stellar spectroscopy data from ESO

The European Southern Observatory webpage has a web page that has tabular spectrogram data from A. J. Pickles, University of Hawaii. There are over 130 .dat files there. Each one represents a ...
5
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0answers
192 views

When the Moon formed and early on, did it orbit over the Earth's equator?

Or was it always at about 5.14 degrees inclination or has the inclination changed over time? See diagram. James K's answer to this question got me thinking about this, and I don't mean to call him ...
5
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0answers
49 views

Did the Juno mission locate Jupiter at the same precision as Saturn (4 km)?

Juno's low perijove should be great for measuring Jupiter's gravitational effect on Juno's orbit. Cassini together with VLBI has measured Saturn's location to within 4 km. Will Was Juno be able to ...
5
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0answers
426 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 ...
5
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0answers
2k views

Exoplanet Temperature Calculations

I was given an exoplanet similar in size and distance to host star to our own earth. It's orbiting a star with luminosity six times our sun, the greenhouse coefficient 0.3, bond albedo 0.3. I need to ...
5
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0answers
93 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 ...
5
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1answer
131 views

Do narrow lines in the spectra of O- and B- type stars always indicate magnetic fields?

I was reading a paper on the differential emission measures of a set of hot O- and B- type stars. As the authors discuss in Section 3 (page 959), two stars, $\tau$ Sco and $\theta^1$ Ori C, have ...
5
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1answer
234 views

Why did the Event Horizon Telescope take so long to take a photo of a black hole?

The Event Horizon Telescope is in the news now because they are about to release the first ever picture of a black hole. They have been working on this since 2006. Why did it take 13 years to produce ...
5
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1answer
112 views

What if there was an asteroid belt with the mass of a planet?

In the past, the asteroid belt was thought to be the remains of a shattered planet. Of course, that was all pseudoscience, the mass of the asteroid belt being 4% of the moon. I've been wondering, what ...
4
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37 views

Simulate earth, moon, sun constellation with dates

I would like to simulate the three object distance, specifically the distance of the moon to both, sun and earth for further investigation into tide prediction. What would be a good starting point ...
4
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0answers
50 views

Counter clockwise rotation of storms at Jupiter's north pole. What explanations have been proposed?

On Earth, high pressures and low pressures occur interchangeably. So that where two pressure systems intersect, they move the air in the same direction. But as Juno revealed the first observations of ...
4
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0answers
110 views

How to apply Fast Folding algorithm?

I have High Time Resolution Universe dataset. I have applied de-dispersion on this HTRU dataset, and thereafter I applied the folding function to fold the dataset. How I can find that the periodicity ...
4
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0answers
59 views

Why does “longitude by chronometer” require first calculating latitude?

I'm studying the history of longitude and Greenwich Time, and I'm currently confused about the "longitude by chronometer" technique. Conceptually, the method seems extremely simple. With a ...
4
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0answers
40 views

What are realistic and unrealistic values for the high energy gamma ray spectral indices of pulsar wind nebulae?

This summer, I was working on a project fitting very high energy gamma ray spectra of the Crab Nebula, a pulsar wind nebula. At energies about $\sim$1 TeV, a simple power law suffices, i.e. $\phi(E)\...
4
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0answers
92 views

What decides the shape of a galaxy?

As I know, most galaxies are spiral, some elliptical, and a rare type is ring-shaped. What causes a galaxy to become a specific shape (i.e. ring vs spiral)?
4
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0answers
80 views

How does the orbit of a 2-body system evolve as it orbits a more massive 3rd body?

I have been reading up on how multiplicity of star systems decline with star mass, which implies a relatively common occurrence of binary star systems orbiting more massive stars. I would imagine this ...
4
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0answers
60 views

When was it realised that most major moons orbit in the equatorial plane of their parent planets?

Inspired by the discussion of the moons of Uranus providing a clue to the planet's axis of rotation in this question, I'm wondering when it was realised that the major satellites are typically located ...

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