Questions regarding the amount of space between two objects, the units, or measurement thereof.

learn more… | top users | synonyms

1
vote
1answer
43 views

How many light years away is Earth from the closest outer edge of the black hole at the center of the Milky Way?

How many light years is Earth away from the closest outer edge of the supermassive black hole in Sagittarius A* at the center of the Milky Way? I don't mean the distance to the center of the galaxy, ...
0
votes
0answers
24 views

How do we determine something is “x” light years away? [duplicate]

I always read/hear "This galaxy is X thousand light years away" or some similar statement (for example see this table). Please excuse the naivety of question. How do we determine that some ...
3
votes
1answer
72 views

what is the farthest object we've been able to bounce signals off of to date?

I know people bounced lasers off of Venus and Mercury in 1960s in order to test the Shapiro delay. Since then, we've developed higher-power lasers and radio transmitters (Bolshakovo transmitter). ...
0
votes
1answer
45 views

Distance of extra-galactic Classical Cepheids

There have been many questions and answers about finding the distance of a star from the earth. But as I did some research on the net, I found that we have specific approaches for finding the ...
4
votes
1answer
110 views

How often do stars pass close (~1ly) to the Sun?

Interstellar exchange of massive objects is difficult across several light years. But as the stars orbit the galaxy the distances between them change. I don't find data for neighbor star distances ...
2
votes
1answer
52 views

Does Tobler's First Law of Geography Apply to Star Composition?

There is a principle in Geography called Tobler's First Law of Geography which states that "Everything is related to everything else, but near things are more related than distant things." Does this ...
6
votes
1answer
43 views

Do we make predictions in our time, or local time?

I was scrolling idly through the Wikipedia article on Orion when I read: Orion will still be recognizable long after most of the other constellations—composed of relatively nearby stars—have ...
0
votes
0answers
32 views

Triangular Asterism Trigonometry

Using the SIMBAD database for Alnitak, Saiph, and Sirius -- i.e.: Alnitak: FK5 coord. (J2000): RA = 05 40 45.527 DEC = -01 56 33.26; Saiph; FK5 coord. (J2000): RA = 05 47 45.389 DEC = -09 40 10.58; ...
1
vote
2answers
63 views

How are the speed, distance and time of India's MOM and USA's Maven Mars missions calculated?

How do the scientists calculate the correct time to launch the Mars mission so that the satellite travel time is less? How they are synchronizing the speed of satellite with respect to earth and mars ...
2
votes
2answers
82 views

Conundrum involving distance to object, universal expansion, age of universe, etc

I was recently reading about a galaxy or quasar (not sure which, so lets just say quasar) where the estimated distance to this thing was some very significant fraction of the age of the universe. ...
6
votes
2answers
67 views

Present distances between planet. How can I find them?

It's "commonly known" how distant are our solar system planets from Sun. But we can't easily say that about planets, which distances can differ greatly, without some observations (or simulations, ...
1
vote
2answers
62 views

What's the furthest object observable by the naked eye from earth?

From XKCD: Caption: 'The light from those millions of stars you see is probably many thousands of years old' is a rare example of laypeople substantially OVERestimating astronomical numbers. So, ...
1
vote
1answer
78 views

3D Positions of Nearby Stars

I have come across a number of star catalogs that list stars by right ascension and declination, along with other data such as magnitude. Is there a star catalog that lists the 3-D position of stars ...
5
votes
1answer
101 views

How far apart can two people watch the moon simultaneously?

Obviously there's a limited part of earths surface where the moon is visible at any given time. I imagine the area of this surface would be a lot smaller than the area where the sun is visible at any ...
2
votes
2answers
56 views

How close would quasars have been to each other?

My understanding is that quasars are the early phase of formation of galaxies. At the time quasars were forming, the universe would have been smaller and therefore things closer to each other. About ...
3
votes
2answers
246 views

How to measure distances to stars by means of spectroscopic parallaxes?

How to measure distances to stars by means of spectroscopic parallaxes on practice? What is the accuracy of measuring distances using this method compared with distances based on HIPPARCOS ...
5
votes
1answer
110 views

When we say a galaxy is 200 million light years away, does this account for the expansion of space in the time it took it's light to reach us?

When we see a distant galaxy, the light we are watching started it's journey millions of years ago. In all that time, space has been expanding, so if the initial distance was A, right now the distance ...
5
votes
1answer
155 views

If we were to see the Sun with our naked eyes from the Orion belt, would all planets be encompassed inside the star? Is this calculable?

When we see a star it looks much bigger in diameter to us than it really is, this picture (extracted from here) explains what I mean: Notice that the point we see in the skynight, represented by ...
1
vote
1answer
32 views

How do we know that the intrinsic brightness of Cepheid variables corresponds to their period?

As I understand it, beyond parallax the next way of estimating the distance to astronomical objects is by using a relationship between the period and intrinsic luminosity of Cepheid variables. How do ...
8
votes
1answer
197 views

How do people measure the distance between the earth and the moon?

How do people measure the distance between the earth and the moon? What methods were used? Where can I find the official data?
0
votes
3answers
95 views

What is the formula to figure out how far away a star is? [duplicate]

I have tried to search for this but it won't show me the formula or "how to" figure out the formula. So what is the formula, and how do you figure it out? (The formula for stars within 400 light ...
4
votes
3answers
107 views

Find distance from star to star?

How do you find the distance from a star/planet/black hole to another? I know people can calculate the distance from Earth to a star, but what about from one to another?
7
votes
2answers
150 views

Why is the observable Universe larger than its age would suggest?

The age of the Universe is estimated at 13.8 billion years, and current theory states nothing can exceed the speed of light, which can lead to the incorrect conclusion that the universe can't have a ...
9
votes
3answers
820 views

What is the distance that the Moon travels during one orbit around the Earth?

What is the distance that the Moon covers in one orbit around the Earth, and does it always take the same amount of time, or does it fractionally differ on each revolution?
4
votes
1answer
72 views

How can we be sure that we have identified very distant stars correctly?

From reading this question on calculating distance to stars and from a bit of background reading on the standard candle theory I still don't see how we can confirm that a star we see at one distance ...
9
votes
2answers
130 views

Calculate Distance To Stars

I was just watching a lecture from Carl Sagan. He talked about figuring out the distance to the stars; it got me interested in learning more about the subject. As far as I know, the Inverse square ...
2
votes
0answers
26 views

How is the distance from Earth to distant celestial bodies calculated? [duplicate]

It's difficult for most people to grasp how distances between the Earth and distant celestial bodies are calculated. For example, when someone tells me that a given star is 100 light years away, how ...
12
votes
4answers
617 views

Is the light we see from stars extremely old?

Our nearest star Proxima Centauri is 4.243 light years away from Earth. Does that mean we are seeing light that is 4.243 years old everyday?
7
votes
1answer
110 views

Which is the closest exoplanet to Earth?

The closest star to Earth (after the Sun) is well-known: Alpha Centauri, 4.3 light years away. But what about the closest exoplanet to Earth, outside of the Solar System?
5
votes
1answer
62 views

Why has Moving Cluster Method been successful only for Hyades?

At all places where I have read of Moving Cluster Method for measuring distance to a cluster and once applied myself on data, I have been told that the method has been successfully applied only to ...
9
votes
2answers
151 views

How does angular resolution of a telescope translate to its parallax precision?

We can often read in the scientific and also more casual reader literature and articles about the angular resolution of various telescopes and other optical equipment, be it ground based or onboard ...
17
votes
2answers
279 views

What is a parsec and how is it measured?

Astronomical units of measurement are mostly pretty straight-forward: Astronomical Units refer to the mean Earth-Sun distance (~150 million km or 93 million miles) Light years are the distance light ...
15
votes
1answer
220 views

How distances are measured in the Solar System, in the Galaxy, and in the Universe?

Distances in our universe can be calculated in several ways: Stellar Parallax Standard Candles Redshift How are these methods linked, and how they are actually used to calculate distances are ...