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2answers
52 views

What are the effects of using non-spherical lenses in refracting telescopes?

Non-spherical (or non-circular) mirrors for reflecting telescopes are common and discussed in many places... But what about elliptical, parabolic or hyperbolic lenses?
1
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1answer
30 views

How to recognize exoplanet transit

I am using Python package lightkurve for exoplanets searching by the transit method. When I download light curve of some star and apply periodogram, I find frequency and power of periodic components ...
5
votes
2answers
275 views

GW190521 black hole merger total mass calculation and missing mass, how does this happen?

I have just read an article about that black hole merge event (it's in Italian): Sette miliardi di anni fa, due mostri si unirono What made me curious is that the article tell that a 66 solar mass ...
0
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1answer
26 views

Fraction of initial mass lost (radiated) by neutron star mergers compared to black hole mergers?

GW190521 black hole merger total mass calculation and missing mass, how does this happen? notes that there are about 9 solar masses missing from the final black hole. GW170817 is the first observed ...
8
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3answers
566 views

Cosmological redshift vs doppler redshift

I'm reading Harrison's "Cosmology: Science of the universe" because Harrison focuses on the distinction between cosmological redshift (he calls it expansion redshift) and the Doppler redshift. He ...
1
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1answer
93 views

Number of actuators in adaptive optics

It is well known that diffraction resolution of a telescope depends on the exterior radius of aperture: One can, for instance, use just a narrow outer ring of a parabolic mirror and the resolution ...
4
votes
1answer
127 views

How far should the source be, for the gravitation waves to be visible on Earth?

If I understand it well enough, gravitational waves cause ripples in the space-time fabric. To our eyes, that would look like those rippling-effects on amateur videos. Where does a source have to be,...
3
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0answers
24 views

Understanding WISE acronyms

I've enoucntered many acronyms related between them, like AllWISE, WISE, NEOWISE, CatWISE, WISEA, WISEAR, WISEAF, WISEU, WISEP, WISEPA, WISEPC, WISEF, WISEPF, WISER, WISEWF, WISET, WISETF, WISENF... ...
0
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0answers
22 views

How were the boundaries of LEO and MEO (or all geocentric orbits) determined? [migrated]

From my understanding: Low Earth Orbit is from 100 - 1240 miles. Medium Earth Orbit is from 1240 - 22246 miles. High Earth Orbit is from 22246 and above. What ...
5
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3answers
2k views

How gently could a comet/asteroid/meteorite “hit” Earth?

Could an object from outer space with the right velocity and orbit come into contact with the surface of our planet in a "slowish" manner?
3
votes
1answer
73 views

GW190521's Luminosity Distance is greater than the age of the universe - how?

According to this article about the gravitational wave observation, GW190521, the estimated luminosity distance is appx 5+/-2 Gigaparsecs, which is appx 16 billion light years +/- 6: https://dcc.ligo....
3
votes
1answer
31 views

What is the difference between aurorae and electroglow?

One of the discoveries of Voyager 2 at Uranus was a phenomenon called "electroglow", which as I understand it is related to charged particles interacting with the atmosphere that cause the ...
5
votes
1answer
4k views

Has THC been detected in space?

I was wondering if and how astronomers have/had detected the molecule Tetrahydrocannabinol (THC), commonly known for it's effects in marijuana, in space. I had previously seen a hoax regarding the ...
2
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0answers
49 views

Could life forms have travelled between the Earth and Mars on meteoroids?

Mars meteorites have been found on Earth, and there likely are Earth meteorites that have crashed on Mars. If you take any random piece of rock from the surface of Earth, the odds are there will be ...
5
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3answers
502 views

Is there a way to tell the difference between earth andesite from Mars

I'm curios if there is a way to test if this sample might be Martian andesite. What type of oxygen isotope (or other) test can be done to address this in some way? As background, any information ...
1
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0answers
29 views

Apparent magnitude of a spherical body with specular, rather than diffuse reflectivity? How bright were Sputnik 1 and Vanguard 2?

How bright are geostationary satellites due to reflected sunlight? and Did Sputnik 1 tell us more than “beep”? What science was improved by information gained from its orbiting the Earth? now have me ...
4
votes
1answer
550 views

Why isn't IMBH candidate GW190521 very “chirpy”? Which types of events will produce the most chirp-like behavior?

The first gravitational wave observations were noted for their "chirp-like" behavior; the objects would speed up as they got closer, radiating more strongly and therefore loosing energy ...
2
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2answers
49 views

How to find the mass of a planet not knowing the gravitational constant?

So I found this problem, I know the gravity of earth $g_0$, I found the orbital speed of one satellite using this equation $\frac{GM_em_s}{(R_e+h)^2}=m_sa$ ($M_e$ is the mass of earth, $m_s$ is the ...
0
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1answer
111 views

How can I crop a fits file and get correct WCS header info without a new plate solve and WITHOUT USING PYTHON?

While my question is similar to this one, the suggestions offered there won't work for my specific situation. For over a month I've been trying to find software capable of this but it's been an ...
3
votes
0answers
71 views

A simple echelle spectrograph for viewing solar spectrum

On the Astrosurf website here, someone has designed a deceptively simple echelle spectrograph for viewing solar spectrum. Briefly, light from an optical fiber falls on an echelle grating and which is ...
2
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1answer
34 views

Strip Brightness in a Spherical System

My question concerns the following problem, published in Galactic Dynamics by Binney and Tremaine and based on a work by Schwarzschild. Specifically, I am having difficulties in deriving the given ...
16
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2answers
2k views

How do satellites impede current telescopes?

As we send up more and more satellites, it stands to reason that our view of the universe becomes more and more obscured. I would certainly expect for example that a large telescope such as the LSST ...
3
votes
1answer
144 views

Latitude and longitude of Eugene Shoemaker's final resting place?

Eugene Shoemaker was an esteemed and celebrated astronomer and planetary geologist. Is it possible to localize their final resting place with a latitude, longitude and feature name?
4
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0answers
67 views

What actually determines the angular uncertainty of the source of a detected gravitational wave?

This answer and comments got me thinking. Astrometry 101 tells us that while we can use $\lambda/D$ as an estimator of resolution, if we can assume a point source we can determine the centroid or ...
7
votes
2answers
370 views

Why are the magnetic poles of a pulsar so far off the rotational axis, yet stable?

My understanding is that a pulsar is a neutron star whose magnetic poles don't coincide with the rotational poles and whose magnetic poles sweep through Earth (allowing us to hear radio noise). If we ...
6
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1answer
61 views

Do the neutrons in neutron stars emit the radio waves?

Neutrons can, especially in extreme circumstances (and large concentrations) emit electromagnetic radiation. I specifically asked about this in Physics S.E. Has a free neutron ever been shown to ...
0
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2answers
31 views

is there a way to determine a distant galaxy’s speed relative to the Hubble Flow by measuring time dilation effects between there and this galaxy?

As I understand it there is a preferred frame of reference based on the velocity for the CMB and our galaxy is moving in relation to it (at about 600 km/s). I think this is how the Hubble Flow is ...
2
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1answer
478 views

How common are binary stars with only one visible sibling?

Single-lined spectroscopic binaries is a binary system where only one star can be detected. Are they common enough to contribute noticeable to dark matter?
2
votes
2answers
46 views

Celestron Nexstar 102GT

Good day folks. My Grandson would like to start using this Telescope Celestron Nexstar GT102, has been in the basement for years, and unfortunately, we appear to have misplaced the eyepieces. Just ...
1
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0answers
52 views

How does hawking radiation work without virtual particles?

How does hawking radiation work without the existence for virtual particles? I read that certain quantum fields are distorted when a black hole forms on top of them. But what fields specifically? If ...
4
votes
1answer
119 views

Does the Sun have a numerical designation in any star catalogues?

Given the existence of large star catalogues listing millions of astronomical objects with numerical designations (such as Tabby's Star, KIC 8462852) it occurred to me that one of them might contain ...
5
votes
0answers
38 views

How is angular momentum transferred between a neutron star and its accretion disk?

Accreting neutron stars can either gain or loose angular momentum via interaction with their accretion disks. This leads to either spin-up or spin-down. Which of the two is the case, depends on the ...
11
votes
3answers
870 views

Has anyone ever tried to make a simple telescope using ice?

I grew up with long cold winters, and saw a lot of remarkably transparent ice formed by refreezing meltwater, both in puddles and ponds, and in large icicles. I'd always thought about making optical ...
1
vote
1answer
40 views

What are the most recent minerals modified by water found to date on Mars?

There likely was quite a bit of liquid water on the surface of Mars less than 4 billion years ago. We know this because we found rocks that old that have been modified by the presence of water. For ...
4
votes
3answers
2k views

Converting Jy/beam to Jy?

Maybe its a dumb question, but to convert Jy/beam to Jy, I just have to multiply it by the beam size in sr right? Being $\Omega$ the beam size: $\Omega = \frac{\pi \theta_{maj} ~~ \theta_{min}}{4 \...
2
votes
1answer
29 views

What is the difference between $E_\gamma$ and $E_{\gamma,iso}$ in gamma ray bursts?

In the literature on gamma ray bursts I see several references to $E_\gamma$ and $E_{\gamma,iso}$ for example as in Piran (2005) $E_{k,iso,52}$ is “isotropic equivalent” kinetic energy, discussed ...
13
votes
2answers
601 views

How will Starlink affect observational astronomy?

I have recently found that people around the world have been posting observations of a line of moving objects in the sky which is very likely to be a part of Starlink satellite constellation, such ...
5
votes
3answers
122 views

Moving from mathematics to astronomy/astrophysics

I'm currently studying for a PhD in pure mathematics (the topic is the cohomology of differential graded categories, just to give you an idea of how pure I mean), although the first year of my ...
1
vote
2answers
55 views

How bright are geostationary satellites due to reflected sunlight?

We are all familiar with seeing low-Earth orbit satellites scooting across the sky in a couple of minutes. Many of them are bright and readily identifiable with the naked eye. Geostationary satellites ...
1
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1answer
40 views

Why does the moon looks like having different filters sometimes?

Why does the moon look more yellow or more LED-like? Thanks in advance
2
votes
3answers
97 views

Why does the latitude of an observer affect the hour angle of a body in Stellarium?

I am using Stellarium for astronomical data to help in studying celestial navigation. While trying to track down a source of errors in my sextant reading or sight reductions I noticed that the local ...
-3
votes
0answers
87 views

Is there any way that we can see the signs of Cosmic Big Bounce of Loop Quantum Gravity, in the Cosmic Microwave background?

Today, Quantum Cosmologies' biggest questions are that what happened before the Big Bang?? Some say, that we can actually have a certain sort of clue with Gravitational Waves to see exactly that what ...
26
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1answer
884 views

Why are there no green stars?

There are red stars, and orange stars, and yellow stars, and blue stars, and they are all understandable save the fact that there is a 'gap': There are no green stars. Is this because of hydrogen's ...
14
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4answers
2k views

Looking for a detailed Milky Way map?

I am a UI designer working on a sci-fi strategy video game. I was wondering wether anybody here might be able to help? I am looking for a top down projection of the Milky Way that labels regions of ...
2
votes
1answer
39 views

Is there any way to distinguish the doppler redshift from a distant galaxy from the probably much greater cosmological redshift? [duplicate]

Is there any way to distinguish the doppler redshift from a distant galaxy, caused by its initial recessional velocity relative to this galaxy, from the probably much greater, cosmological redshift, ...
1
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1answer
89 views

The drift of the Moon's equatorial rotation velocity

Are there any citation or documentation showing the measured degradation of the Moon's equatorial rotation velocity (thus affecting its moon's axial rotation)? I am looking for the drift of the Moon'...
6
votes
4answers
2k views

Need Simple equation for Rise, Transit, and Set time

I've been looking, unsuccessfully, for hours for a simple set of equations: Input: RA and Dec of an object Observers Lat and Lng Current Time Output: Rise Time Transit Time Set Time (and, ...
3
votes
1answer
233 views

What is the “lunar irradiance” received by the Earth from the full Moon?

The solar irradiance received by the Earth is 1361 $W/m^2$. What is the lunar irradiance received by Earth from the full Moon in the same units? My first thought was to work it out via apparent ...
1
vote
1answer
48 views

Right ascension, Equinox, Positions Help

I am trying to answer the following question which I slightly understand but need a clearer explanation: What are the times of year to observe an object at X hours of RA at visual wavelength? I am ...

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