# All Questions

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7 views

### What is wrong in my calculation of eigenvectors?

On pp. 280–281 of the book Solar System Dynamics (https://books.google.ca/books?id=aU6vcy5L8GAC&printsec=frontcover#v=twopage&q&f=true), eigenvalues $g$ and eigenvectors $\bar e_{ji}$ ...
25 views

### .mt file convert to .fits/.ascii/.dat

How to convert .mt file with a spectrum to a more convenient format, please? I am able to display that in fv: Fits Viewer, but I am lost in converting. Thank you
33 views

### Orbital path projections onto a 2D plane

In ProfRob's excellent answer to Is S2 still the fastest known star in the galaxy?, he posted a figure of the orbital paths of stars passing close to the supermassive black hole near the center of the ...
6 views

### How massive does a moon have to be to have a stable magnetic field?

Is there a minimum mass or other minimum properties necessary for a body to have a strong, stable dynamo to create a magnetic field conducive for life? For example, would it be possible for Titan to ...
44 views

### IRAF Like software that work on Window

My professor asks to me install IRAF for the photometry project but We have a hard time installing it and also I'm more comfortable with the Windows environment (because there is other software that ...
997 views

### Why can't we use the semi-minor axis in Kepler's third law?

Why can't we use the semi-minor axis in Kepler's third law? The formula for the third law is: $$\dfrac{a^3}{T^2} = \text{const.}$$ Instead of semi-major axis (a) why can't we use the semi-minor axis (...
5 views

### Universe expansion data validation

I am not an expert, just a enthusiast, so if possible please keep explanation simple. That said I have start reading about universe expansion and the idea seems to me revolutionary (the image of an ...
62 views

### In which countries are there organised Messier Marathons?

Just out of curiosity... In which countries have there been or are current, organised Messier Marathons? Thank you for all answers and effort for this!
4k views

### Does General Relativity really predict Black Holes?

I'm doing some research on black holes for a science video contest. I want to explain the physics of how they work, but also want to have a little background on how they're formed. As far as I've ...
36 views

### Installing IRAF

Recently I asked this question on IRAF like software that can be run in a window but it seems it is not possible. So I installed window subsystem for linux. I followed these steps to install IRAF. ...
41 views

### Can the lensing effect of Sagittarius A* be used to image the stars diametrically opposite to the sun?

The sun can magnify an image of a source 100 ly away nearly 100 billion times, if the ring is captured from the nearest focal point (550AU). According to Christian Ready of Launch Pad Astronomy, we ...
80 views

### What are the real conditions for the creation of an atmosphere/loss of an existing atmosphere?

Overview: Taking a planet Ganymede for example (moon, technically I suppose). Ganymede is huge (well, in contrast to other bodies) and I've noticed a pattern between larger bodies and atmospheres. ...
20 views

### Are features in the CMB correlated with features in the SDSS map of the most distant galaxies?

This is a follow up to an earlier question to which @pela gave an excellent answer. Apparently the statistics of the length-scales of the CMB fluctuations are similar to those obtained from other ...
90 views

### Accuracy of calculating the vernal equinox?

Calculating the exact time of the vernal equinox is essential for many ephemeris calculations. NASA Goddard Institute for Space Studies uses (at least for some purposes) the following, rather short ...
74 views

### Trying to calculate terrestrial line of sight duration to a fictional satellite [closed]

Let me preface this with most of my understanding or orbital mechanics come from playing Kerbal Space Program. I understand most of the terminology, and a good chunk of the math, but not all of it. I'...
51 views

### Error in Jean Meeus textbook? (rising, transit, setting)

In Astronomical Algorithms 2nd Ed. by Jean Meeus, we have the following example of calculation of rising, transit and setting times for Venus on 1988 March 20 at Boston (Example 15.a): Page 103: https:...
138 views

### Why (the heck) is the basic angle of GAIA 106.5°?

This answer to Why does the Gaia space telescope have two main mirrors says: According to the GAIA FAQs which does an excellent job: http://www.cosmos.esa.int/web/gaia/faqs: Why is there an angle of ...
97 views

### what is the net effect of nodal and apsidal lunar precession?

In apsidal lunar precession, the moon's elliptic major axis precesses eastward and completes one revolution eastward in 8.85 years. Because the orbit is inclined relative to the ecliptic, basic ...
171 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 ...
96 views

### Density of stars on celestial sphere

The pattern of stars on the surface of the celestial sphere seems perceptually to have an universally looking pattern. If you pick a region of the sky at random, for instance here by using the (...
2k views

### Why isn't most hydrogen in the universe molecular (diatomic), instead of atomic (monoatomic)?

Similar questions have been asked before; but, why? Is the monoatomic hydrogen left over from the Big Bang? And hasn't had the opportunity to collide with other hydrogen atoms yet? Or are hydrogen ...
598 views

### Orbits of Trojan Asteroids

I understand that the Trojan points are located 60 degrees ahead and behind a planet in its orbit. However, since there are quite a number of Trojans in Jupiter's orbit, they cannot all be exactly at ...
90 views

### Could photons orbit a black hole if fired at the correct angle?

My experience with Kerbal Space Program gives me the impression that it's impossible to transfer from a stable orbit of one body to the stable orbit of another without deceleration. But is this true ...
49 views

### What consequences does a positive muon anomalous magnetic moment have for astronomy?

On April 7th, 2021, the muon $(g-2)$ collaboration published Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm, a result which made it to standard news, partly under headlines ...
113 views

### Could diatom blooms affect albedo of an exoplanet?

And perhaps display a seasonal variation if the exoplanet has an axial tilt, providing proof of an Earth-like world supporting at least oceans with microbial life?
35 views

### Can we identify planets, moons, and large asteroids in our solar system have a unique spectroscopy?

I'm looking to create a database of relatively consistent measurements for various cosmic bodies. Please inform if there's a way to gather reproducible signatures, with the same set of instruments to ...
16 views

### Specifications of a High Gain Antenna [migrated]

I am designing a telecommunications device capable of redundant communication from Earth to Saturn's moon Enceladus which ranges from 8 to 11 AU from Earth. I have decided on an X-band high-gain ...
89 views

### Open source code for the maths behind a heliostat?

Theoretically, using a Raspberry Pi, (at least) one mirror, and two motors, one should be able to build a heliostat, i.e. a device which redirects sunlight to a fixed spot, like a scrub in the shadow ...
114 views

### Estimating close approach between all asteroids themselves

I am currently writing a C++ program to show asteroids in 3D, and find close approaches or collisions. I got my orbital elements from JPL https://ssd.jpl.nasa.gov/sbdb_query.cgi. So far so good, with ...
42 views

### Naked-eye limiting magnitude: mismatch between Wikipedia, online converter and Shaefer's formula

I'm trying to make sense of the difference between the reference Sky Quality Meter (SQM) readings given in the Wikipedia article on Bortle scale, online converters like [1] that are based on Shaefer's ...
70 views

### Formula to calculate the apparent magnitude of Earth from arbitrary distances

I would like to calculate the apparent magnitude of Earth from various distances, say from the Voyager probe at this moment or from various stars in the sky. I know there must be a formula that I can ...
56 views

### Did we adapt to Earth or Earth to us?

I often hear that Earth is a unique planet because it has life. We also see a proper balance between plants and humans and other animals. Why is life not possible on another planet? Often people say ...
15k views

### If light has no mass, why is it affected by gravity?

Light doesn’t accelerate in a gravitational field, which things with mass would do, because light has a universally constant velocity. Why is that exception?
34 views

### How to estimate the inclination of a galaxy between edge on and face on?

I have the images of a galaxy and the field of view and I would like to determinte the inclination of a galaxy between edge-on and face-on. Would that information be enough to do the calculation? Or ...
35 views

### IAU 2018 Exoplanet definition

In 2018 the IAU produced a definition of an exoplanet: The current official wokring definition of an exoplanet as amended by IAU Comission F2: Exoplanets and the Solar System in August 2018, reads as ...
23 views

### Is GAIA the only game in town for looking at quadrupole gravitational deflection of light?

From Gerry Gilmore (2018) Gaia: 3-dimensional census of the Milky Way Galaxy 4.4 Fundamental physics Relativistic effects are highly significant for Gaia measurement accuracy, with tests of General ...
19 views

### Has GAIA learned anything about General Relativity looking near Jupiter? (Gerry Gilmore: “oblate rotating mass moving in a deeper (Solar) potential”)

From Gerry Gilmore (2018) Gaia: 3-dimensional census of the Milky Way Galaxy 4.4 Fundamental physics Relativistic effects are highly significant for Gaia measurement accuracy, with tests of General ...
206 views

### Precision in the measurement of the distance to the Sun

How precisely can the distance to the Sun be measured? Wikipedia says the distance to the Moon can be measured upto millimeter precision. But Wikipedia article on distance to the Sun says only about ...
260 views

### Why is the Boomerang Nebula colder than the CMB?

An earlier answer on temperature mentioned that the temp of the Cosmic Microwave Background (CMB) is $2.4\,{\rm K}$ and the temp of the Boomerang nebula as ${\rm 1\,K}$. How did the nebula cool faster ...
3k views

### Where can I find the positions of the planets, stars, moons, artificial satellites, etc. and visualize them?

What resources are available to find the positions of planets, stars, moons, artificial satellites, asteroids, and other heavenly bodies?
57 views

### Is there any correlation between the Cosmic Microwave Background (CMB) and the distribution of distant galaxies?

The Cosmic Microwave Background (CMB) is remarkably isotropic but does exhibit a distinct dipolar Doppler shift and also much smaller but measurable fluctuations in intensity and polarization. ...
117 views

### Calculate how long it takes for the sun to complete one orbit around the galaxy?

We know the speed that the sun travels around the galaxy is $220\, {\rm km/s} = 0.00021 \, {\rm parsec/year}$. I'm unsure of how to find the period?
273 views

### Why aren't there blue elliptical galaxies or yellow spiral galaxies?

Elliptical galaxies are universally old and yellow; about three-quarters of all ellipticals have no significant star-forming gas or dust left, and even the quarter or so of ellipticals that are still ...
89 views

### How much is usually deposited in a Mars regional dust storm?

Is there any indication of how much dust is deposited, especially in areas that are not open where wind might produce a cleaning event?
51 views

### What is the significance of using baseline pairs in radio interferometry?

Radio interferometry utilizes arrays of smaller telescopes that are linked together to synthesize a larger aperture telescope. Astronomical radio observatories, such as the Very Large Array in New ...
19 views

### What is time period of sun revolving around the center of Milky Way? [duplicate]

What is time period of sun revolving around the center of Milky Way?
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### How to remove radial velocity effects of an exoplanet from the host star spectra?

I have a spectra of an M dwarf and I would like to remove the Doppler shift effects due to a known exoplanet, with known planetary parameters, from the whole spectra of the star. I have shifted/...
71 views

### Why does Hellas Basin look white on some maps?

One map of Mars I see a lot is this colourized map: the Viking colourized global mosaic (Source): But one thing which strikes me as odd is just how white the Hellas Basin is (the white patch which is ...
I have a value for the relative flux $F_2/F_1$. With some uncertainty value $a$. If I use the equation to get relative magnitude: $m_1 - m_2 = 2.5 \log_{10}(F_2/F_1)$ How do you now calculate the ...