All Questions

1,756 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
6 votes
0 answers
504 views

How do I calculate the Hill radius of a star in a binary system?

Is there an easy way to calculate the Hill radius of a star in a binary system at different orbital radii where both stars are of the same mass and in circular orbit around one another’s centre of ...
Slarty's user avatar
  • 349
6 votes
0 answers
199 views

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. ...
uhoh's user avatar
  • 31.1k
6 votes
0 answers
103 views

What's the number density of `Oumuamua like objects?

Recently, the fly-through the Solar system of the inter-stellar object (ISO) `Oumuamua caused quite a stir in the astronomy community. I wonder whether there are reliable estimates for the (local) ...
Walter's user avatar
  • 5,546
6 votes
0 answers
69 views

Recreating Observer Ecliptic Lat/Lon from JPL Horizons using SPICE toolkit

I apologise if this is the wrong place to ask. I am trying to recreate part of the calculations by the JPL Horizons system using SPICE. Specifically the Observer Ecliptic Latitude and Longitudes. I'd ...
FridgeMagnet's user avatar
6 votes
0 answers
109 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?
Youngsub Yoon's user avatar
6 votes
0 answers
331 views

What would go into the design of a simple sky quality meter, used to measure night sky brightness?

@MCG's answer mentions several methods to classify night sky quality or brightness, and goes on to say: Additionally, you could always purchase a SQM (Sky quality meter) which is a small, portable ...
uhoh's user avatar
  • 31.1k
6 votes
0 answers
102 views

How often do partial solar eclipses of 90% of totality occur in same place?

I know that the mean interval between total eclipses in a single place is about 375 years, which is not surprising given the small band of area of the totality. However, the penumbra of the eclipse ...
Tyler Durden's user avatar
6 votes
0 answers
118 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 ...
Lakey's user avatar
  • 161
6 votes
0 answers
239 views

Viewing "Diamond Fuji"

Diamond Fuji is a phenomenon in which the (typically) setting sun is positioned directly atop Mt Fuji. Some relatively detailed predictions for viewing times at a nearby park are available here. I ...
kyle's user avatar
  • 161
6 votes
0 answers
216 views

Kepler - Creating the Ellipse (Astronomia Nova)

In Chapter 58 in Astronomia Nova, Kepler made his final step to finally create the ellipse (for the orbit of planets) http://science.larouchepac.com/kepler/newastronomy/part4/58/index.html In the ...
user15474's user avatar
  • 159
6 votes
0 answers
62 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 ...
LocalFluff's user avatar
  • 11.4k
6 votes
0 answers
479 views

Linear limb darkening coefficient, u

I was wondering if anyone knew of any resources to understand the linear limb darkening coefficient, $u$. That is to say, how the $\theta$-dependent coefficient $u$ (or sometimes $b_{\nu}$) varies ...
MichaelJRoberts's user avatar
6 votes
0 answers
148 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 ...
Logan R. Kearsley's user avatar
6 votes
0 answers
68 views

What is the reason for the dispute over the variation of core mass with heavy metal abundance?

In Metal-Poor Stars IV: The Evolution of Red Giants, Rood writes The differences in the results of these papers are large enough to introduce appreciable uncertainties into the study of the ...
HDE 226868's user avatar
  • 36.5k
6 votes
1 answer
187 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 ...
HDE 226868's user avatar
  • 36.5k
6 votes
1 answer
475 views

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 ...
HDE 226868's user avatar
  • 36.5k
6 votes
1 answer
292 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 ...
David says Reinstate Monica's user avatar
6 votes
1 answer
216 views

Could an ultra-hot Jupiter flare?

Some of the ultra-hot Jupiters (WASP-33b, KELT-9b) have dayside surface temperatures similar to low-mass stars. Would they be capable of producing flares? To be specific, I am asking about the ...
user avatar
5 votes
0 answers
26 views

Newtonian theory of small perturbations: Continuity equation

Starting with the continuity equation $$\frac{\partial \rho}{\partial t} + \nabla_r(\rho \vec{u}) = 0$$ making those substitutions. $$\nabla_r = \frac{\nabla_x}{a}$$ $$\rho(\vec{x},t) = \bar \rho(t)[1 ...
merlinbluepickle's user avatar
5 votes
0 answers
125 views

Why do double neutron stars remain bounded?

I read that in principle, the formation of a double neutron star requires that at the time of the second supernova explosion the binary consists of a $\sim$ 1.4 solar mass neutron star, and a second ...
some_math_guy's user avatar
5 votes
0 answers
61 views

Is gravitational lensing "additive" in a line of sight?

As usually depicted, gravitational lensing implies, at least, three objects: a distant source, an observer, and a "massive enough" object in the middle, where enough is the mass needed to ...
nuwe's user avatar
  • 769
5 votes
0 answers
86 views

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 ...
Brondahl's user avatar
  • 338
5 votes
1 answer
238 views

Will Lunar Months be the same length Millions of Years in the Future?

If I remember correctly, the amount of time it takes for the moon to rotate around Earth is getting longer over time. Is this true, and if so or the opposite is true and a lunar month is getting ...
Dromeoraptor pennato's user avatar
5 votes
0 answers
153 views

If a Milky Way supernova were to happen, how long would it take for astronomers to be notified?

If a Supernova were to happen in the Milky Way, how long would it take for astronomers to be notified? How long would it take for the people running the gravitational wave and neutrino detectors to ...
blademan9999's user avatar
5 votes
0 answers
90 views

Are dust-dust collisions necessary to explain Kordylewski clouds at Earth-Moon L4/5? Aren't the cross-sections, number density timescales too small?

The recent question Can dark matter accumulate at Lagrange points? mentions Kordylewski clouds and that article begins: Kordylewski clouds are large concentrations of dust that exist at the L4 and L5 ...
uhoh's user avatar
  • 31.1k
5 votes
0 answers
174 views

Why does the tropical year have a ~161 years cycle?

Using PyEphem, I calculated the time difference between consecutive summer solstices in the south hemisphere for the last 4000 years, and plotted them in a graph. It seems like random noise around the ...
ordptt's user avatar
  • 173
5 votes
0 answers
513 views

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?
user avatar
5 votes
0 answers
202 views

Different techniques for calculation of celestial bodies dynamics with different time-scales

Differential equations describing the dynamics of celestial bodies (rotation, nutation, precession and other effects) can be solved numerically, which makes it possible to study their general non-...
dtn's user avatar
  • 706
5 votes
0 answers
113 views

There is a decibel limit to sound based on the medium, what is the decibel limit in neutronium?

I've been participating in many discussions online about the classic thought experiment on pressing a button a light year away with a light year long rod. The solution boils down to the speed of ...
Aaron Hathaway's user avatar
5 votes
0 answers
68 views

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? ...
SCh's user avatar
  • 151
5 votes
0 answers
83 views

A couple of questions about Earth's hypothetical planetary rings

From what little I know of this subject, It should be possible for Earth (Or a planet the size of Earth) to keep a system of Planetary Rings. However, looking around the internet only gives me info ...
Erik Mækir's user avatar
5 votes
0 answers
133 views

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 ...
nuwe's user avatar
  • 769
5 votes
0 answers
105 views

Beginners question about time scales

I'm using https://github.com/Bill-Gray/jpl_eph for a personal project to read JPL DE files, namely DE430 and the more recent DE440. This generally works great and when tested against a reference ...
zero0cool's user avatar
  • 151
5 votes
0 answers
134 views

What is this cluster of light trails captured on long exposure images?

I was taking photos of the Perseids meteor shower on 13/08/2022 in Peak District in the UK. The camera was fixed stably on a tripod, set on manual mode, taking 8-second exposures continuously. When I ...
Anthony's user avatar
  • 151
5 votes
0 answers
70 views

"Quarter root of intensity" in coronographic plots

In excitement regarding the JWST release, I came across Krist et al, The JWST/NIRCam coronagraph: mask design and fabrication, within which there is the following plot: Fig. 9. Focal plane images ...
0xDBFB7's user avatar
  • 151
5 votes
0 answers
121 views

When's the most recent time that we could have missed a supernova?

I know that if a supernova were to happen in the galactic Core, the dust there would prevent the visible light from it from reaching us, so if one were to have occurred there in say 1900, we wouldn't ...
blademan9999's user avatar
5 votes
0 answers
89 views

Time dilation if an asteroid and a small black hole entered a larger black hole?

For an outside observer, everything moves slower the closer it is to a black hole's event horizon, even photons, due to the black hole's time dilation. We also know that when two black holes collide, ...
Devon's user avatar
  • 151
5 votes
0 answers
266 views

Why aren't there sulfuric acid seas on Venus?

It's commonly known that sulfuric acid rain doesn't reach Venus' surface. It evaporates instead because the surface it too hot. But considering how high the pressure at the surface (9.3 MPa), shouldn'...
Prido1024's user avatar
5 votes
0 answers
49 views

Extract surface density profile from a temperature profile?

I have a protoplanetary disk model which outputs a temperature vs. radius profile, based on radiative transfer. Looks something like this... One of the inputs to the model is the surface density ...
lucas's user avatar
  • 1,386
5 votes
0 answers
207 views

Spectrum features of main sequence and giant stars with the same spectral type

Hence, the spectral features of the supergiant are different from those of the Sun-in accordance with the Saha equation- even though both stars are essentially at the same temperature. The pressure ...
빛나는밤's user avatar
5 votes
0 answers
42 views

HR 6819 "Vampire" star - mass disparity in binary star system

Regarding the two B-type stars of the HR 6819 system, a recent news item (2 March 2022), European Southern Observatory researchers find 'vampire' star sucking outer layers of companion star states, ...
Fred's user avatar
  • 2,169
5 votes
0 answers
36 views

How to model the kinematics of gases expelled from comets and planetary atmospheres?

Once the ices of comets sublimate, where do they move to, and with which equations do you describe their motion in the interplanetary medium? Similarly, where do the gases that are stripped from the ...
Astrolien's user avatar
  • 151
5 votes
0 answers
149 views

Is it possible to narrow down possible dates for the following eclipse pattern?

I am searching for an year which satisfies the following criteria. Dates are in Gregorian calendar. Criteria Year range 3800 BC to 500 BC Solar Eclipse of any kind between October 14 and October 22 ...
Profile name's user avatar
5 votes
0 answers
98 views

How do the giant planets excite the orbits of asteroids?

The giant planets, particularly Jupiter, are notorious for bringing about changes in eccentricities and inclinations of smaller bodies(asteroids and KBOs). Jupiter, in fact, throws almost all the ...
Ambica Govind's user avatar
5 votes
0 answers
64 views

Type Ia supernova by fallback?

Is it possible for a massive star of more than 1.4 solar masses (probably around 3 or more but below the threshold for type II) to collapse into a white dwarf and a planetary nebula, then go supernova ...
WarpPrime's user avatar
  • 6,653
5 votes
0 answers
77 views

Obtaining the derived period of $\omega$ Canis Majoris

I have read these two papers: On the nature of the Be phenomenon I. The case of ω Canis Majoris Stellar and circumstellar activity of the Be star ω CMa II. Periodic line-profile variability In the ...
Anna-Kat's user avatar
  • 505
5 votes
0 answers
73 views

Is there a mass-vs-radius chart for neutron stars?

I'm aware that we currently don't have an equation of state for the radius of a neutron star, because we don't know what happens to neutrons at their cores, and because the equations involved with ...
zucculent's user avatar
  • 1,748
5 votes
0 answers
104 views

Comparing Observing Techniques to Quantify the Effects of Starlink Satellites on Astronomical Observations

To take pictures of satellites I think I could use these methods listed below (are there more?) Method 1 The satellites are tracked and their positions predicted. By utilising software tools and code ...
Alessandro Portante's user avatar
5 votes
0 answers
79 views

What limits can we set about life beneath the ice of Europa?

Do we know enough about the conditions beneath the ice of Europa to say anything about the complexity of life that may live there? Can we rule out macroscopic life?
Ryan_L's user avatar
  • 643
5 votes
0 answers
79 views

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 ...
B--rian's user avatar
  • 5,616

15 30 50 per page
1
2
3 4 5
36