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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?
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 ...
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 ...
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 ...
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 ...
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 ...
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,...
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... ...
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 ...
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?
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....
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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?
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 ...
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 ...
229 views

If a pulsar's rotational and magnetic axes were aligned and both aimed at us, would we see a steady radio source?

In other words, a non-pulsing pulsar?
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 ...
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 ...
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?
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...