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Questions tagged [distances]

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

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How is the size of a distant planet determined?

How is an object's size determined from other solar systems than our own? How are new large bodies being found in our solar system currently?
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3answers
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How do we measure distance in space?

I know that you can calculate the distance to another star for example, by using the phenomenon redshift to determine how much it has redshifted because of the expansion of the universe. But how do ...
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1answer
63 views

How Did Early Astronomers Measure Distances?

Prior to the era of radar and other forms of radio/RF/EM ranging, what approaches, methods, and techniques did early astronomers (e.g., Kepler, Cassini, Copernicus) use to measure the distance(s) from ...
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2answers
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Ludwig's star distance

Mizar and Alcor, each about 83 light-years away (in fact Mizar presents system of four stars and Alcor is binary system. It is not yet known if those 6 stars presents one or two star systems. In ...
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1answer
36 views

What limits the use of the H-R diagram to measure distance (main sequence fitting), what distances is it useful for?

Is it only possible to measure objects that form around the same time? Is it possible to measure clusters from distant galaxies other than our own?
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2answers
123 views

What is the maximum distance measurable with parallax?

What is the furthest star or celestial object whose distance has been calculated with parallax and how does it compare to the theoretical limit using today's telescopes? And how exactly does telescope ...
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1answer
104 views

Can you find your own location in space by measuring angles between stars?

Imagine you have 3 star points in 3D space A,B and C. From your unknown position P in space you can measure the angles APC, APB, BPC and you know coordinates of A,B and C and therefore the distances ...
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1answer
120 views

What is the farthest we can see into the universe?

Is there a limit in which the mass in space obscure the ability to detect anything farther even as technology progresses? Related: Can the range of the observable universe be extended through an ...
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1answer
62 views

What does it mean when there are two plus-or-minus signs for a measurement?

As far as I know, the plus-or-minus sign is used to indicate the statistical margin of error of a measurement. But what does it mean when there are two plus-or-minus signs in the same measurement? ...
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2answers
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How would I search within an angular distance of an object corresponding to a distance in parsecs?

I'm interested in the learning about the local densities around galaxies. I've found myself a bit confused on how to relate angular distances (arcseconds) with physical distances (parsecs) when ...
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2answers
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Determine distance from the galactic center in DS9

I have a list of coordinates of black hole/neutron star systems in decimal degrees (ie. {(266.416,-29.009), (266.418,-29.009),...} from DS9 and would like to determine the distance from SgrA* in ...
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Data on galactocentric distances of various stars?

I'm creating a project for my astronomy class (introductory course) that requires knowledge of the galactocentric distances for many stars. I'm struggling to find a good source on this, and I'd rather ...
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1answer
873 views

Calculate the true diameter of stars from photographic plate

I am reading the book "Fourier Analysis" from T. W. Körner, and in chapter 95, he explains how you can compute the diameter of stars on a photographic plate. He says that "Since observations of the ...
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1answer
67 views

Historical Distance of Planets to Earth [duplicate]

I'm curious if there is a readily accessible tool available, or simply a reliable way to find out what the distance of the planets in the solar system were on a given date. For example, if I am ...
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3answers
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Beta Andromedae (Mirach) and distances mentioned in original Cosmos series from 1980

In one of the episodes from Carl Sagan's show Cosmos he explains that Beta Andromedae is the second brightest star in the constellation Andromeda, and is 75 light years away. The link to the video is ...
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1answer
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How do we know if an object is redshifted?

I have some questions about redshift. I think that the first two hang on the last two, but feel free to point out anything you think I should know. How do we know if an object is actually redshifted,...
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3answers
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Is this a coincidence?

The smallest distance probed in any experiment so far conducted is $10^{-18}$m and the largest distance we can have is the radius of the universe, nearly $10^{26}$m. The ratio is $10^{44}$. In ...
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2answers
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Was Earth closer to Europa on 1983-11-25 or 1985-07-22?

xkcd #2003: gives a humorous line of succession to the United States presidency. The comic's title text, found by hovering over the comic, states that a tie is broken by whoever was closest to the ...
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How tightly clustered are the CHIME-detected FRB repeats?

In the past few days, journalists have been playing the usual "X could be aliens" game. This time, X is repeating FRBs from a galaxy 1.5 billion light years away. (Or is it 1.5 billion years ago? The ...
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1answer
78 views

Logarithmic scale for large distances?

I understand this is an icky subject, but I recently got interested in units for large distances for applications in cosmology and what not (after hearing about the redefinition of the kilo and kelvin)...
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2answers
82 views

Galactic mass estimation from apparent magnitude and distance

Can we estimate the order of the total mass of any galaxy from the apparent magnitude and its distance to us? Just like \begin{equation} M_{galaxy}=c\times 10^{8}M_{\odot }, \end{equation} where $c$ ...
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0answers
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Deducing distance of closest neighbor galaxy from expression of correlation and mean galaxy density

The original post was on physics exchange but I prefer to move it here : I am trying to estimate the distance of closest galaxy neighbor knowing the expression of number of neighbors $\text{d}N$ into ...
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4answers
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Is parallax a “technique to measure the star distances” or a “tiny shift in star's position”?

I am not completely sure whether the Parallax is a "technique to measure the star distances" or a "tiny shift in star's position"? The a book says two points about Parallax: Astronomers have ...
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2answers
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Why is Proxima Centauri called Proxima Centauri?

It seems very logical, to call the star, closest to earth, "Proxima" ("Proximus" is Latin for "close" and the word for star, "stella", is feminin, hence "Proxima"), but there's one thing I don't ...
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Lunar illumination (percentage) data on an eclipse day needed

I am looking for the information on the percentage illumination of the moon during the different stages of a total lunar eclipse. Is there a database from where I can acquire information of lunar ...
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Distance between two planets [closed]

Planet A and Planet B orbit a sun-like star. Planet A has a semi-major axis of 1 AU from the star. Planet B has an albedo of .8 and has the same radius as Jupiter. When Planet B is observed from ...
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1answer
82 views

How to calculate the time and distance of closest approach of a star?

How should I approach this problem? A star has a motion on the sky of 0.78 arcsec/yr in declination and 1.33 arcsec/yr in right ascension. Calculate the velocity of the star in the plane of the sky ...
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1answer
79 views

Would you get the same planet-discovering data for our own system at the same distance we're getting from Earth?

So there's a boatload of planets being discovered around stars in our solar neighborhood. Kepler 22, 638 ly away, was discovered to have a planet Kepler 22b, calculated to be twice the size of Earth. ...
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2answers
162 views

How is distance in light-years converted to years back in time?

When I look at the Alnitak,the left most star of Orion's belt, it is 736 light years away. How could I convert this distance to an estimate of how long ago what I am seeing happened. Would it be ...
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2answers
163 views

Are the viewable nebulae only in our galaxy?

Where are all the nebulae located? Yes, a simple question that should be obvious but apparently is not to me. To be more explicit, how far are all these objects? Are they mostly in our galaxy? I'm ...
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2answers
229 views

Where is the center of the Milky Way located?

I have downloaded a star database from this page (The HYG Database): http://astronexus.com/node/34 And all the stars have (among other parameters) their XYZ coordinates in parsecs according to this ...
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1answer
20 views

DSO carthesian coordinate estimations

I'm more in the CS based stack exchange, but this question prompted me to come in here. I've been compiling a large set of ephemerides for solar system, stars with mag > 6.8, exo planets etc, and I ...
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2answers
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Of the stars in the Gaia / Hipparchos catalogs, which one is the most isolated?

This is just a matter of curiosity; I was thinking about a scifi story. By "Isolated", I mean that if for every star (or binary) we found the distance to its closest neighboring star, then which one ...
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1answer
73 views

Which star with a Bayer designation is the farthest from the Sun?

The key to finding the answer seems to involve processing data from astronomical databases, which I'm not sure how to do in this case. I'd prefer to limit the answer to the original list of ...
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1answer
79 views

How to find star location knowing latitude and LST

Newbie learning Astronomy and was curious how to locate a star giving a Latitude and LST. For example if my LST is 4:00 and my latitude is 20*N, how would I find where the Horsehead Nebula appears in ...
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1answer
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How thick is the cosmic microwave background, including the part we cannot see within the observable universe?

What I want to know is how thick the observable universe is from the point of the cosmic microwave background and beyond. It appears the thickness of the cosmic microwave background itself (the part ...
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1answer
122 views

What would be the average distance between each 1-degree latitude on Jupiter?

Do planets like Jupiter have a system of latitudes and longitudes (I believe yes)? So if yes, what purpose do they serve? Is there anything different in their purpose from Earth lat-longs? and What ...
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0answers
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Comoving distance between two points [(RA1, Dec1, z1) and (RA2, Dec2, z2)]

I have Redshift (z), RA and Dec positions for two points in a galaxy catalogue (say P1 = [<...
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2answers
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How far away is this galaxy?

Arp 299 is in the news, with most sources reporting it as 140 or 150 million light-years away. But what kind of distance is this? The paper which is trhe source for the news item has Supplementary ...
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1answer
212 views

Question from Introduction to Modern Cosmolgy by Andrew Liddle

The exact question goes like this: In the real Universe the expansion is not completely uniform. Rather, galaxies exhibit some random motion relative to the overall Hubble expansion, known as their ...
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How can you estimate distance of an object by its redshift? [duplicate]

Is there a way to take the red shift of an object and, from that, calculate a rough estimate of its distance from us (in parsecs, preferably)?
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1answer
100 views

What is difference between horizon and comoving distances?

I wonder if there a difference between horizon and comoving distances in cosmology ? I mean both correspond to a null geodesic $(ds^2=0)$ right ? $$d_{horizon} (t) =a(t) \int\limits_{0}^{r} \frac{{\...
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2answers
109 views

Are we really seeing the asteroids from the past?

Is it actually relevant to study objects that are light years far? Because in theories we are actually seeing the past as the light takes years to reach us. Lets say we are studying a asteroid that ...
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3answers
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How close would the sun have to get to Earth for there to be severe consequences?

According to earthsky.org the Earth gets 3 million miles closer to the Sun than its usual distance of about 93 million miles on average. My question is, how close would the earth have to be to the ...
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2answers
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Would you expect this planet to be hotter or colder than earth?

I have a lab where given the mass of a star being $1.23$ times the math of our sun, some planets wobble of central start is $273$ days, and the velocity of 79 m/s. I found that the mass of the planet ...
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1answer
89 views

Distance parallax and cosmological distance in universe in expansion

I know that we cannot measure cosmological distances with parallax, but this is more a philosophical question. Am I correct in assuming that if we could measure distances using parallax (like stellar ...
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1answer
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Thought experiment about our location in the Universe [closed]

[I am sorry if this isn't the best place for this - it was either here or maybe on the Worldbuilding SE.] I recently re-read one of my favourite childhood sci-fi books (Chocky by John Wyndham), and ...
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Is the Milky Way seen as how it looked millions of years ago?

The distant an interstellar object is, the more time is required for light to travel, which is known, measured as light years. So are the farthest stars and gas clusters in the Milky Way seen as how ...
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Type I delta-Cepheid star, calculation of apparent maginute and luminosity

I am curious to see if I have calculated this correctly: A Type I delta-Cepheid star with a one month (30day) period is put at the distance of the star Vega. a) Determine the apparent magnitude ...
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1answer
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Distance from the sun can equal a hospitable planet?

It is said that planets are continuously moving away from the sun. At one time Mars was just the right distance to support life at least temperature wise? Could Venus be far enough from the sun ...