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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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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
58 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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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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87 views

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
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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
56 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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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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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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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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995 views

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
77 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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75 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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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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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
155 views

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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61 views

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
78 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
75 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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158 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
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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
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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
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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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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
68 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
72 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
72 views

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
113 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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46 views

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
111 views

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
171 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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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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108 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
316 views

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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134 views

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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70 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
107 views

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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361 views

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 ...
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2answers
265 views

Can we see the stars the at the edge of the Milkyway?

This question proved much more difficult to formulate than I initially imagined. It concerns how far out in the Milky Way that we actually see with different telescopes. I know the Milky Way disk is ...
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1answer
382 views

Distance between stars Epsilon Eridani and Tau Ceti?

I am working on a story. It would be helpful if someone could provide the distance in light years between star Epsilon Eridani and star Tau Ceti.
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423 views

Observed lunar distance data?

Where can I find free/open data for the observed (not calculated/theoretical) distance between the Earth & Moon? I want to see the observed distance of the Moon, hour by hour.
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103 views

Is there a physical limit to how far we can go?

Is there a physical limit to how far we can go? I am thinking there could be based on the following: 1: There are parts of the universe expanding faster than the speed of light that we will never be ...
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1answer
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Finding the number of stars n light-years from the sun

The nearby stars seem homogenously spaced out enough to give a general "stellar density." Does there exist some kind of mathematical expression that can determine the number of stars n light-years ...
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1answer
383 views

What's the distance between Venus and Jupiter?

What is the minimum, maximum and average distance of the Venus and Jupiter? I only found 670,130,000 km and 670,198,000 km as an average distance (here and here).
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Is the Alpha Centauri star system moving closer to us?

The closest star system after our sun is Alpha Centauri, a three star system with Proxima Centauri, a red dwarf, slightly closer to us than the other 2, around 4.3 light years. I tried Wikipedia and ...