# All Questions

9,727 questions
Filter by
Sorted by
Tagged with
13 views

### What if the two Black Holes spiraling around each other are evaporating via their Hawking radiation?

A non-technical explanation In a Gravitational Wave event, the point is that in this event when Black Holes are spiraling around each other, they will cause the very fabric of Space-time to ripple and ...
45 views
+50

### How do you know that the remnants of the explosion of a Star are of a Hypernova?

Some Background? There are many types of Supernovae that can be classified into the following categories :- (This list is available here.) Type 1A supernovae • Their spectra show very little hydrogen ...
11 views

### Does lightning on Venus affect the chemical composition of the clouds?

It is established that lightning occurs on Venus due to the presence of sulfuric acid clouds. Does this constant electric discharges and electrolysis affect the composition of the clouds on Venus ...
37 views

### Could Earth be the only and last planet with life?

The other day I had a dream...I don't remember anything about it but I woke up with almost a crystal clear realization/moment of clarity: The reason why we can't find alien life and all other planets ...
18 views

### Why Trojans haven't merged into moons

Jupiter's trojans are located in the L4 and L5 Lagrange points. These two points are stable, so why don't all the trojans have already merged into small moons? And since it's not the case, what ...
71 views

### How to plot celestial equator in galactic coordinates? Why does my plot appear “backwards”?

I'm trying to plot celestial equator in galactic coordinates. Here is my code (based on this answer): ...
2k views

### Why does Titan have lower surface gravity than the Moon when Titan is more massive?

Reading on Wikipedia I saw that Titan is 80% more massive than the earth's moon but has only 85% the surface gravity. Why is this?
119 views

### Star map, where?

I have been looking at the website https://thenightsky.com and wanted to create a star map my self, from a specific place on a specific date. Where would I be able to find this?
1k views

### Retrofitting a DSLR camera to a super-cheap Tasco reflector telescope

I was given a 1995 vintage Tasco "302003" Newtonian telescope recently and have had some exciting success with it. I have managed to view the Moon in beautiful detail and also had my first glimpse of ...
55 views

### Universe being a computer simulation [closed]

If the Universe were not real and was a computer simulation, then why do we never see people reappear that have died ? They could be programmed back into the simulation. So couldn't this be considered ...
30 views

### A strangely moving bright orange light in the sky [closed]

My brother came downstairs at 3 AM and told me about a light in the sky that was moving around but not in the way that a plane does. It was a bright orange light that was moving strangely in a way ...
134 views

### Two luminous points disappearing in the sky

I saw a few days ago two luminous points in the sky, which were quite close (about 1-2 degree of separation between them) and not apparently moving (or to slow to be noticed with the naked eye). The ...
39 views

### Why does the Hubble flow does not carry photons with it?

I have this naive question. We know that the expansion of the universe "takes" or "carries" the galaxies with it, separating them, but this doesn't apply to photons. My guess is ...
33 views

### Is it true that star treks 'Klingons', come from Uranus? [closed]

Is it true that star trek's 'Klingons', come from Uranus? i'm asking for a friend... a non-believer science guy, who drinks too much and smokes a lot of weed. :)
234 views

### Is there any proof of space being created?

Is there any proof for space being created? Because I guess an explanation for the dark energy (dark = our understanding of it) could be that there is a gigantic amount of matter/dark matter that we ...
490 views

### Is the Universe really expanding at an increasing rate?

Here's what I just read from Wikipedia's page on the Hubble Space Telescope: While Hubble helped to refine estimates of the age of the universe, it also cast doubt on theories about its future. ...
72 views

### Can New Horizons be used to measure the distance to Betelgeuse (despite its fickle photocenter)?

The New Horizons spacecraft is almost 50 AU from Earth and near-simultaneous images taken by its telescope and one on Earth have demonstrated parallax without relying on the movement of Earth in it's ...
37 views

### Why do brighter stars/planets appear physically larger?

Look at Sirius and then some 2nd magnitude star. Sirius appears physically larger despite both stars subtending approximately the same angular diameter. Callisto is far enough from Jupiter at its ...
140 views

### How accurately could late 50s - early 60s humans have mapped the solar system?

What if early SETI investigations had focused on our own solar system, rather than distant stars? Given the technology that existed around the 1950s, how much surveillance would humanity be able to do?...
55 views

### What inaccuracies are in this Stellarium depiction of the sky?

I found this depiction on Stellarium of the sky as seen from near the Apollo 12 landing site on January 11, 2131. The earth is the black circle in the arm of the Milky Way. Here is a similar view ...
27 views

The abstract of A magnetar parallax (also in MNRAS) says: TE J1810-197 (J1810) was the first magnetar identified to emit radio pulses, and has been extensively studied during a radio-bright phase in ...
168 views

### Does Saturn raise tides on Titan's lakes?

Titan is the only body in the Solar System other than Earth to have large bodies of surface liquid. Since Saturn is much more massive than the Moon, I would expect for tides, if they're present to ...
58 views

### When was the parallax of a star first measured?

Telescopes like Gaia measure the parallax of stars with a great precision. But for stars that are beyond 11 kpc, their parallax is still too small to be measured. With Earth-bound telescopes, only the ...
41 views

### A double star consists of two stars of equal brightness at equal distance from the Earth. What is the apparent magnitude of the combined object?

The magnitude of each star in the V-band is mV= 8.34. If these stars are so close together that they appear as one object, what is the apparent magnitude of the combined object? I just want someone to ...
32 views

### I witnessed a steady stream of falling stars slowly falling one after another this morning. What was it? [duplicate]

This morning at 6:18am I witnessed a steady stream of falling stars that lasted at least 90 seconds from the time I noticed it. I live on a farm east of Edmonton, Alberta, Canada and the stars were ...
30 views

### Help understanding why these two sub-Hill sphere moon stability limits are so different?

Comments under this answer to What orbital period would produce one New Moon (and one Full Moon) each year? What other effects would this produce? link to Stable satellites around extrasolar giant ...
2k views

### Do all objects get larger in an “expanding universe”?

I'm envisioning an analogy of the universe as a plane with marbles in that plane to represent different planets. Now, if this plane expands how does this work? I assume that it is not like 'nothing' ...
49 views

### Does the Sun and Moon basically appear to “move on the sky” identically regardless of location and date?

For a long time, I've been trying to use Stellarium (simulation) and many visualizations and animations in order to get a good idea of how the Sun and Moon move across the sky, as seen by a human from ...
9 views

### Cross-correlations between Lagrange and Fourier synthesis

In the context of forecast for large surveys, I have to make cross-correlations between 2D (with angular coordinates of Lagrange transformation for GC photometric and Weak Lensing) and 3D (Fourier ...
32 views

### Get the expression of probed volume between 2 redshifts

1) I can't manage to find/justify the relation (1) below, from the common relation (2) of a volume. 2) It seems the variable r is actually the comoving distance and not comoving coordinates (with ...
75 views

### How will they know when to start taking the picture of the black hole at the center of the Milky Way?

@csm's answer to Why not take a picture of a closer black hole? points out that it's necessary for the supermassive black hole at the center of a galaxy to be actively feeding for it to generate a ...
22 views

### How did Michelson measure the diameters of jupiter's moons using optical interferometry?

In Betelgeuse: How its Diameter was measured (Chant, C. A., Journal of the Royal Astronomical Society of Canada, Vol. 15, p.133, Bibliographic Code: 1921JRASC..15..133C) the author says: The paper in ...
29 views

### Radial velocity exoplanet search - can mathematical details be explained? (Bayesian periodogram MCMC)

Radial velocity (RV) is one of main methods for exoplanet search. The popular description of the method sounds simple - one should measure periodic Doppler variation of a spectral line of a star and ...
2k views

### What orbital period would produce one New Moon (and one Full Moon) each year? What other effects would this produce?

I am interested to know whether it's possible for the moon to orbit the earth at such a rate that we would see only one New Moon and one Full Moon a year. If so, what other effects would we experience?...
38 views

### Photon A has a wavelength that is 810 times shorter than the wavelength of photon B [closed]

Photon A has a wavelength that is 810 times shorter than the wavelength of photon B. What is the ratio of the energy of photon A to the energy of photon B?
11k views

### How does the Moon look like from different latitudes of the Earth?

I have heard, that on the northern hemisphere, you can estimate a direction of south if you imagine a line going through the tips of the border between illuminated and shadowed part of the Moon, and ...
42 views

### Relation between photometric redshift in a given bin and conditional probability

I take over an old question that is not yet clear for me. Indeed, I would like to formulate the equation (1) below under the form of "conditional probability" but I can't manage to do that. ...
39 views

### Do brown dwarfs have stripes?

Brown dwarfs (BD) are often depicted with stripes. brown dwarf Jupiter Pictures of BD resemble Jupiter but brown dwarfs ...
4k views

### Do celestial objects need to be big to have liquid water on their surfaces?

I mean no asteroid, planetoid that I am aware of has water on its surface. It is way more common to see ice in it. So I figured that the size of the celestial body has something to do with the cycle ...
746 views

### Is the Object in this Photo Mars?

A little bit of context: I dabble in amateur astronomy, however only very lightly. I originally wanted to make some observations of Mars because I know it is supposed to be very close these days but ...
10k views

### How do scientists know that distant parts of the universe obey the physical laws exactly as we observe around us?

How do scientists know that distant parts of the universe obey the physical laws exactly as we observe around us? The question might look a bit odd but I am really stuck on my head. We know, ...
88 views

### Is the angular size of the black hole in the movie “interstellar” completely overblown?

I assume everybody is tired of reading questions derived from the movie Interstellar, I will try to keep this short and simple: In general in movies, in order to have stunning visuals, celestial ...
26 views

### What is the 'scale factor' equation for a dark-matter dominated universe?

The Friedmann equations can be solved exactly in presence of a perfect fluid with equation of state $${\displaystyle p=w\rho c^{2},}p=w\rho c^2$$, where ${\displaystyle p}$ is the pressure, \${\...
8k views

### Why haven't I seen the Moon?

It has been some time since I've seen the Moon. What are the conditions that might affect whether or not the Moon is visible within a 24-hour period? Please take into consideration any notable ...
47 views

### How to view the surface of Mars with a 130 mm Newtonian?

I bought a Celestron AstroMaster 130EQ telescope, but I am not able to see the surface of Mars through using the 10 mm eyepiece. Instead I only see a glowing dot. What should I do to view the mars ...
33 views

### Is extra-planetary phosphine actually a new discovery?

For all the buzz on Venus’s phosphine, I’m curious as to what sets it apart from the findings of phosphine on Jupiter, Titan, etc. There are several papers on NASA.gov dating to 1979 and more recent ...
52 views

### What is a good focal length for DSO

I found two telescopes that i'd like to buy, but one has 900mm focal length ((Skywatcher Newton 114/900 EQ1)) and the other has 500mm focal length ((National Geographic Dobson N 114/500)). My ...
41 views

### Historical Lunar Tables and the Associated Error Bound

Consider as an example, AstroPixel's Six Millennium Catalog of Phases of the Moon''--- http://astropixels.com/ephemeris/phasescat/phasescat.html My question is two-fold: How are these tables which ...