2
votes
2answers
92 views

In geocentric models, did the earth rotate?

Under geocentric models, did the earth rotate around its axis? I assume that if the earth rotated around its axis, then the sun would not have to orbit around the earth at a very fast rate, whereas ...
5
votes
3answers
110 views

Is it possible to disprove geocentrism without telescopes?

The development of telescopes enabled the discovery of moons orbiting around Jupiter, and the existence of a full set of phases of Venus, as opposed to a limited set which would be predicted by ...
1
vote
2answers
41 views

What qualifies as a local star?

My professor used the term 'local star'. What range of distance is generally considered 'local' for a star? And what would be considered distant?
-3
votes
2answers
91 views

earth is spherical , does it mean the ground on earth is like a ball? [closed]

I know earth is spherical in shape. Does this means earths atmosphere is spherical in shape or the ground/(land+water combined) is in spherical shape. I have some doubts if the second is true. ...
0
votes
2answers
47 views

Why do we have so few neutrinos to study?

According to Wikipedia most neutrinos passing through the Earth emanate from the Sun. About 65 billion (6.5^10) solar neutrinos per second pass through every square centimeter perpendicular to the ...
0
votes
1answer
56 views

Why do not we use optical telescopes to study cosmic rays directly?

HESS, CTA, and VERITAS are used to study cosmic rays. What they receive are optical (maybe very blue) photons. So my question is: Why don't we use optical telescopes to study cosmic rays directly?
1
vote
2answers
89 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?
-1
votes
4answers
65 views

Light Cone Explanation

Not sure if this question belongs here, or on Physics. Would someone please describe the "anatomy" of a light cone and provide an intuitive example? I have read the Wikipedia article ...
3
votes
0answers
40 views

How Are Radioactive Decay Rates Influenced by Neutrinos - On Earth and Other Dense Planets

I read a science report recently that mentioned an accidental discovery where radioactive decay rates shifted slightly slower in advance ( about a day and a half) of solar storms or in sync with sun's ...
1
vote
1answer
65 views

Retrograde motion and Kuiper Belt Objects

As seen from Earth, planets such as Mars and Jupiter exhibit retrograde motion when they are near opposition (from Earth). I am wondering how this effect extends to very distant objects, such as ...
5
votes
1answer
83 views

Theoretical limits for natural satellites having natural satellites

Is there an inherent instability or limit that prevents natural satellites like the moons of Jupiter from having their own natural satellites? I looked at other questions such as do moons have moons ...
-2
votes
2answers
47 views

What “revolutionary” discoveries were made by Hubble Telescope [closed]

Forgive me for the naive question. Besides taking pictures of tons of objects in space, what kinds of revolutionary discoveries were made as a result of data from Hubble? Did Hubble shed light on any ...
2
votes
1answer
78 views

Calculating 2004 BL86 position using software

Is it possible to view asteroid 2004 BL86 using Stellarium or the iOS Star Walk app?
2
votes
2answers
101 views

How do stars or galaxies get their spin?

It is my understanding that when a star, a planetary disk, or a galaxy forms, the rotational momentum of the whole system is conserved. Due to the smaller size of the resulting object, it will spin ...
2
votes
0answers
50 views

Is there a cosmic, rather than technological, upper limit to what a telescope can resolve?

Space radio interferometers could have a baseline of millions of kilometers, but is there a point where a larger baseline doesn't improve the resolution anymore because the photons observed are ...
4
votes
3answers
112 views

Do objects look larger the further away they are, beyond z=1?

I stumbled upon this text which illustrates and says: We find that as the object is moved to higher redshifts its angular size first decreases (as naively expected) but soon begins to increase ...
1
vote
2answers
79 views

How to complete the Hipparcos Catalog?

I've downloaded hipparcos catalog from the Strasbourg Universe but whilst there is a lot of information, I can't find the names of the stars that the HipID relates to. There is the wikipedia page ...
-1
votes
2answers
76 views

The destruction of the Universe by a bubble

So I was watching a documentary on television about this and a number of theories that are proposed as to what the fate of the Universe will be: "Big Crunch" "Big Freeze" "Big Rip" I understand ...
1
vote
2answers
130 views

Why don't we orbit the center of our galaxy?

At the center of the milky way, there must be some giant mass that keeps the galaxy from just floating away from itself. So, obviously, we feel the immense gravitational pull of whatever this is. But, ...
1
vote
3answers
46 views

How to find RA 0

I am standing in an open area and can see the sky for a full 360 degrees. I have the coordinates of an object (RA and DEC). Where do I look to find RA 0?
2
votes
2answers
80 views

What does it mean to say 'space exists?'

From another question I posted, I learned that not only was matter created from the Big Bang, but more importantly, space itself. What does it mean for space to be created? Does it exist in the same ...
1
vote
1answer
39 views

Why do we need to add a second to 30 June and risk upsetting Internet?

We linked a physical constant (the time of one second) to a physical non constant (the rotation of the earth) so there will have to be adjustments - or not? Is it important that the UTC in one line on ...
5
votes
1answer
82 views

What's special about Saturn that it has distinctive rings?

This may overlap with other questions, but I'm asking what is unique about Saturn in location, properties, etc that is has far more pronounced rings? It's between Jupiter and Uranus and Neptune in ...
2
votes
1answer
75 views

The tidal locking problem concerning Earth sized planets in habital zone around Red Dwarfs

Would twin planets orbiting around each-other present a solution to tidal locking of habitable planets in Red Dwarf systems. It's an awfully easy equation to set up....oh ok I'm fibbing I can't do it. ...
1
vote
2answers
50 views

What are the units of distance in this subtended angle calculation?

I'd like to find the distance at which a 2.4 cm coin is subtended by an angle of 10". I've drawn my diagram and found that $D=\dfrac{d}{\alpha}$ using the small angle approximation. Since $10" = ...
1
vote
1answer
43 views

PowerSeeker 114Q

I just purchased a powerseeker 114q by Celestron. This is my very first telescope. I believe I assembled it correctly however I can't see anything out of it. Well I can see a small corner of an image. ...
-2
votes
1answer
51 views

Why does the sun rise north of east between the vernal and autumnal equinox?

Can someone please explain this phenomenon? A solid explanation seems to be missing from the entire internet.
1
vote
1answer
34 views

Did I see a meteor or a re-entry?

Last night (January 21, possibly 5:30 UTC), from my house in northern California, I saw a moving point of light in the sky, going west to east, crossing about 120 degrees of sky in 5 seconds or so. ...
5
votes
1answer
147 views

How often does the supermassive black hole in the Milky Way become a quasar?

My current interest is black holes and quasars. I was wondering how often they erupt--specifically ours? Would it be blindingly bright on Earth? Finally, would there be any effects that would alter ...
1
vote
1answer
573 views

Is there any planet/star bigger than VY Canis Majoris?

Compared to VY Canis Majoris, our Sun is more like a speck of space dust. Is there any planet or star which is known to us that is bigger than the VY Canis Majoris?
1
vote
1answer
31 views

Recent origin of Saturn's rings

Saturn was formed around billion years ago along with Jupiter. After which it had enough time to form moon which can break into rings. Then why is it said that Saturn's ring are of recent origin - ...
2
votes
1answer
37 views

Where does the dust on 67P/Churyumov-Gerasimenko come from?

As we (laymen) are told, comets lose gas and dust when they descent into the denser regions of the solar system. Seemingly so much and so large parts that they can even cause meteor showers like in ...
3
votes
1answer
80 views

If Alpha Centauri A's solar system exactly mirrored our own, what would we be able to detect?

Suppose there was an exact replica of our solar system 4.4 ly away (people included). What would we be able to detect and with what telescope(s)? Which planets? Could we detect radio transmissions ...
1
vote
0answers
14 views

How do I deduce my latitude and longitude from N obervations of occultations from the same place?

I think it would be an interesting exercise to measure the latiude and longitude of my house using N occultation timings. I would like to see how precisely I can measure it using that technique, and ...
1
vote
2answers
63 views

Finding the temperature of Earth from temperature of Mars and its distance from Sun

I am to compute the temperature of planet--in fact I've already found out it's Earth--knowing only: the surface temperature of Mars (210 K) and its distance from Sun (1.524 AU) and of course ...
4
votes
1answer
103 views

How likely is it that the Sun will destroy our electric society?

Given the studies of the Sun and similar stars and the most impressive understanding of its physics, is there any kind of probability distribution for its dangerous behavior? There are also some ...
4
votes
1answer
418 views

What is supposedly in the center of the Milky Way?

It's big. It's bright. It's white. It's so intense. But what is at the center of the Milky Way?
1
vote
1answer
33 views

When is Gamma Draconis closest to the zenith in London on April 4th

I am reading Roobert Hooke's paper An attempt to prove the motion of the earth from observations (1674, faksimile). Hooke writes The principal dayes of doing which will be about the 4 of April, ...
1
vote
2answers
80 views

How to calculate distance from object to point on celestial sphere

I'd like to calculate the distance (in arcsec) from the object nearest to ra='08h55m10s' dec='-7d14m42s' to that point on the celestial sphere. I am actually having trouble identifying the object. I ...
0
votes
2answers
77 views

Do we have knowledge of the geology of the moon?

With reference to the Ebb and Flow lunar satellites, was there any data about its geology? Is there a central core, or is it homogenous?
5
votes
3answers
740 views

Is it safe to view moon at daytime through telescope

I have a little 76mm Newtonian Reflector. I want to see the moon at daytime. Is it safe to look at sky at daytime when sun is shinning or there is any risk of sun.
3
votes
1answer
103 views

Could the planets in the Solar System have been captured?

Ignoring any current beliefs, is it possible that the planets could have been captured by the Sun's gravitational force after drifting through space while retaining their axis of spin and speed? ...
3
votes
2answers
110 views

Why do scientists think life requires water? [duplicate]

As far as I know, scientists seeking extraterrestial life are simply looking for plantets containing water in liquid state. To be honest, I find this weird. It is true that life - in the form we know ...
15
votes
8answers
3k views

Why can't we see distant galaxies with the naked eye?

If light keeps travelling in a straight line, why can't we see distant galaxies with the naked eye? Surely if you stared long enough, the light from them would eventually hit your eye? I apologize if ...
1
vote
2answers
99 views

How can I see a nebula?

I've recently been seeing a bunch of pictures of nebulae and I'm just fascinated by their beauty and complexity. Is there any kind of telescope that would make it possible to view it from here on ...
-2
votes
3answers
58 views

the initial astrometry calibration for a telescope

Generally a telescope can memorize how to point to a target with a particular RA&Dec. There is no need to calibrate every day. How can it happen? How to let the telescope(non-amateur) know the ...
2
votes
2answers
98 views

Is the universe simply a mass of atoms in 'void'; what does it look like?

I've always been stumped with the question of what lies beyond the universe, and I've come to the firm conclusion - void (i.e. completely empty). Does it make sense then to think of the universe as a ...
3
votes
1answer
48 views

Why is [O III] a good density probe in interstellar medium?

According to Draine in his book "Physics of the interstellar and intergalactic medium" (page 210/211) and Caltech [O III] line ratio's (amongst others) are a good density probe, but I cannot really ...
1
vote
1answer
49 views

How fast does Venus move as seen from the earth?

So last night I was about to sleep with the window in front of me. there was a 3 inch gap between the curtains that let me see a small portion of the sky. I could see something magnificently bright in ...
3
votes
1answer
58 views

What are the exact physical parameters used to calculate Mercury precession with Einstein theory?

NASA measured 43,13 arc seconds per century. General relativity predicts 42,98 arc seconds per century. I try to find out what the parameters' values such as $G$, $M_{sun}$, $\omega_{min}$ at ...

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