3
votes
2answers
378 views

Equation to find distance between objective and eyepiece

I have a home made astronomical telescope with 100 cm objective lens and 5 cm eyepiece.when viewing an object in infinity the distance between eyepiece and objective is 105 cm. So how could I ...
2
votes
2answers
168 views

Can we have a second moon?

This question sounds like silly and rather fantasy filled. But can our earth's gravity capture a sizable asteroid and make it rotate around our earth like our moon which become visible from ground. Is ...
3
votes
2answers
86 views

Is it plausible that Mars could have been one of Jupiter's natural satellites at one time?

Would more questions regarding the planet be answered if this was the case?
2
votes
1answer
45 views

What is Color Index?

I found this Wikipedia page on this property called color index. Unfortunately, I could not find a source that explains this property well. My interpretation is that color index is the brightness ...
3
votes
1answer
106 views

Does the Sun orbit the Milky way in a (kind of) flat or inclined orbit or more of a sine wave? [duplicate]

I know it can't be a perfect ellipse or smooth orbit due to all the matter in every direction, and our Sun could be affected by a gravity assist of sorts if it passes close enough to another massive ...
2
votes
4answers
143 views

Notable differences if all stars would disappear except the Sun

I am not an astronomy expert, but as of today, all other stars than the Sun have little to no effect on life on Earth. So I was thinking, would there be any differences for the Earth at all if all ...
5
votes
1answer
211 views

Can a gas moon exist?

Could a gaseous moon exist in the same way as a giant gas planet? All the moons in the solar system are rocky, or icy. Why shouldn't gas planets have gas moons?
3
votes
1answer
173 views

Is a black hole heavier than the star from which it was created?

I did some googling around and couldn't get answer to a simple question of black hole mass compared to the star from which it was created. It is well known that giant stars burn very bright and ...
5
votes
3answers
153 views

Visibility of human activity on the moon

In this video the host of Test Tube Plus states that you can go out a buy a laser, point it at the moon, and see the retroreflector left by the astronauts. When you point at the right spot you'll ...
1
vote
1answer
111 views

Where did everything come from?

Where did all the material and gas contained in our universe come from? If it was the size of a "coin," then it could not have contained all the matter that is in our universe today before the Big ...
3
votes
0answers
58 views

How bright can white dwarf stars glow as they accrue matter?

I realize this is kind of general as it would depend on the size of the white dwarf and the rate of accrual. The general idea I got thinking about is what would happen if a white dwarf star - lets ...
8
votes
3answers
245 views

How do we know that our galaxy is a spiral galaxy?

I know that our galaxy is spiral in shape, but I'm wondering how the scientists found out that our galaxy has a spiral shape. I don't think we can see the entire galaxy from telescopes on Earth, ...
1
vote
2answers
88 views

Are objects in the universe moving away from each other at the same acceleration?

This is a follow up question to Does the universe expand at the same rate everywhere in the universe?. If the universe is expanding, then it would seem necessary for each object (ie galaxy) to be ...
2
votes
1answer
51 views

What is the share of stars in total radiation input of Earth?

Earth gets its radiation input primarily from Sun, then from reflected sunlight from Moon, and stars. Among these, what is the share of stars (or sources outside solar system) to this total radiation ...
2
votes
1answer
85 views

How can the observable universe be so small if there are so many stars in it?

The observable universe has a radius of about 46.5 billion light years. That’s big but I just wonder how that can be big enough to fit in everything we know exists in the universe. There are hundreds ...
3
votes
1answer
89 views

Is there a photo that shows a iron meteor or asteroid in space in raw form having no layers of fusion crust?

A raw iron meteor or asteroid in outer space should be in its raw form having no signs of fusion crust from the friction of atmospheric entry and should therefore show distinctive signs like the ...
3
votes
1answer
155 views

Why is the Color scheme of natural satellites in our solar system based of light shades of grey?

What is the explanation of the color similarity that the majority of natural satellites obtain?
1
vote
0answers
51 views

What would be the maximum theoretically possible angular resolution?

I have studied some basic astronomy, but I have difficulty conceptualizing the physics of luminosity and optics. We use electromagnetic spectra to detect existence and properties of distant planets, ...
4
votes
2answers
258 views

Can we compress any object to create black Holes?

In general, when a star runs out of nuclear fuel, gravity gets the upper hand and the material in the core is compressed even further and creates black holes. I am clear till here. Now the question ...
0
votes
1answer
67 views

could dark energy be a force coming from the hyperspace outside the universe?

It seems to me that the expansion of the universe is only being looked at one way. a repelling force, basically being the opposite of gravity. After pondering this for many nights, I began to wonder ...
3
votes
1answer
82 views

Estimates of exoplanets distribution consistent with current data

I am interested in current estimate of distribution of planets of various radii in various distances from their parent star. There is many sources, where one can find database of presently known ...
2
votes
2answers
131 views

Does all of time exist and if so where is it?

I've recently learned about the theory of relativity and time. I'm trying to understand it more. My (basic) understanding is that there is no distinction between past present and future and that ...
0
votes
0answers
27 views

Does all of time already exist if so why can't we see it? [duplicate]

I've recently become fascinated with the theory of relativity and time. If all of time already exists, and there is no difference between past, present and future then what is preventing us from being ...
0
votes
1answer
59 views

TIME TRAVEL-Can it be really done? [closed]

Is it posssible for us to time travel? Is light essential factor or the dark matter and dark energy?
1
vote
1answer
42 views

What exactly is a stellar association?

What exactly is a "stellar association" in the strict kinematic sense?
1
vote
2answers
112 views

Gravitational red hift vs Doppler redshift: Is the universe really expanding?

Is it possible that the redshift observed by Edwin Hubble is really from a gravitational redshift and the universe isn't expanding as he has predicted? What I think I know thus far is this: ...
4
votes
1answer
45 views

Do sungrazing comets leave a field of meteoroids near the Sun?

A large fraction (a third?) of all comets found (with observational bias thanks to SOHO) have been sungrazers, breaking up with perihelion of a few of Sun's radius. Is there reason to believe that ...
3
votes
1answer
112 views

What is the color of Venus if it has no atmosphere?

Mars looks reddish and Mercury looks gray because they lack thick atmospheres and we can see their "real color" easily, how about Venus? Is the surface of Venus really yellowish in color?
15
votes
1answer
182 views

Why does a mirror bent 'like a potato chip' allow space telescopes to be smaller and have a wider field of view?

I was browsing NASA featured items and came across this - Out With the Old, In With the New: Telescope Mirrors Get New Shape Called freeform optics, this emerging mirror technology, brought about ...
0
votes
1answer
65 views

Could the Earth use gravitational lensing / bending of light to see it's own bottom?

Specifically, I have often wondered whether gravitational lensing might be able to (theoretically) be used in order to see light reflecting off the Earth that has zoomed off into space and been bent ...
2
votes
2answers
54 views

Astronomical telescope making

I am thinking about making a telescope. I have a 100cm focal length lens which I can use as objective lens in my telescope. So which is the best focal length I can use as eyepiece in my astronomical ...
3
votes
5answers
210 views

Why does gravity increase in star formation?

When a star ignites ( ie. fusion starts ), the star maintains its form by balancing gravity's inward pressure, and radiation's outward pressure. I get that the fusion of hydrogen atoms releases ...
4
votes
3answers
333 views

Is a black hole a perfect sphere?

I know all about how black holes form and why their gravity is so strong. However, is the gravity equally powerful in all directions? Will the event horizon appear as a perfect sphere?
1
vote
0answers
48 views

How to use spectral profiles to determine luminosity class?

I know the luminosity classes are: Ia-0 ( Hypergiants ), Ia ( bright supergiants ), ... , VII ( white dwarf ). I also have learned that you can use the presence of absorption lines ( ie. use spectral ...
4
votes
1answer
33 views

What parameters determine whether galaxies colliding will result in a merger or a hit and run?

Colliding galaxies sometimes merge and sometimes pass through each other. Either way, there are huge changes as a result. What are the parameters that matter in determining whether a collision will ...
1
vote
2answers
90 views

Gravitation - Pulling or Pushing force?

According to Newton, gravity is the pulling - or in fact the attracting - force of any heavenly body towards any object to its center. But, to the contrary, Einstein once said that the four dimensions ...
1
vote
1answer
167 views

Does the Moon capture radiation pressure from the sun causing momentum from photon propulsion? [closed]

Could a planet's main use for natural satellites be that of a photon sail?
3
votes
2answers
87 views

What are the stars/constellations a beginner/enthusiast can easily identify?

I was just wondering what are some of the stars, constellations or any other things that one can just identify by looking up at the night sky. For example, when ever i look up, I immediately see ...
1
vote
4answers
193 views

Does time slow down because the universe is expanding at an accelerating rate?

If the universe is expanding at an accelerating rate, such that the galaxies' moving away from each other is accelerated, then time should also slow down. And when universe will accelerate to the ...
1
vote
1answer
83 views

Are hot stars like O-type stars entirely composed of helium?

Hot stars like O-type stars show no hydrogen in their spectra. Does this mean they are made entirely of helium? Any explanation would be really helpful.
2
votes
1answer
47 views

Math for calculating the terrestrial longitude directly under the sun with time

I'm trying to calculate the longitude on the earth where it's noon at some time. (That is, the longitude which is coplanar with the plane defined by the sun and the earth's axis.) Here is my python ...
2
votes
0answers
19 views

What are the implications if the Sun was formed in a warm nebula?

Molecular oxygen O2 has been found on comet 67P/C-G in a ratio of 3.8% to water, which is much higher than expected. An explanation proposed is that the Solar System formed from a molecular cloud ...
5
votes
3answers
227 views

Is extraterrestrial mining more difficult or impractical for bodies without plate tectonics?

This article talks about the possibility of mining Uranium on the moon. Since the Moon lacks the geological forces that have created veins of concentrated minerals on Earth, would extraterrestrial ...
2
votes
0answers
46 views

Are there equal number of planets, stars, galaxies etc in observable universe spinning in both directions?

Just because we observed that our milky way galaxy is spinning in a certain direction therefore we assume it is applicable to all other galaxies, I am curious to find out if hypothetically most of the ...
4
votes
2answers
306 views

What happens to oxygen produced on the Sun (or other stars)?

Through nuclear fusion, the Sun can (or at the very least, someday will) produce atoms of all elements up to and including oxygen. And in terrestrial chemistry at least, when you combine oxygen, ...
2
votes
2answers
62 views

Linear extent of an accretion disk

I have a homework assignment question on accretions discs (essentially an estimation of the number of electron scatterings, but this is just for background). There are a few parameters, one of them ...
5
votes
2answers
112 views

Was that actually a shooting star during the supermoon eclipse on September 27th 2015?

During the super-moon total lunar eclipse on September 27th a meteor-like streak passed very close within view of the event. It appeared to happen at the very middle, the maximum eclipse. ...
4
votes
1answer
101 views

Conversion between Astronomical Frames, ex. IRCF, FK5, FK4, etc…

I'm a little bit confused about reference frames, and I was wondering if someone could help clarify a few things? So let's say I have equatorial coordinates that refer to the mean equator and equinox ...
4
votes
1answer
122 views

Where are we in an approximate timeline of the possibly habitable universe?

Our universe is supposedly 13+ billion years old and our Sun is a third generation star. It seems to me that we are now in a relatively young stage of the universe. How many generations of stars will ...
8
votes
3answers
150 views

How do scientists name space objects?

I am curious that there are lots of celestial objects (planets, comets, stars, galaxies, etc.) in space. How do we name them?

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