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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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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
51 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
31 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
63 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 ...
2
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1answer
53 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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27 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
89 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
75 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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0answers
48 views

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
65 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
105 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
146 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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2answers
73 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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1answer
63 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
84 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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3answers
255 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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0answers
45 views

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
60 views

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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1answer
151 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 Milkyway that we actually see with different telescopes. I know the Milkyway disk is ...
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1answer
185 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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3answers
207 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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1answer
91 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
60 views

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
189 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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1answer
289 views

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 ...
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0answers
377 views

question about distance between moon and earth at apogee and perigee (wikipedia has different value to space.com)

I have a question about the distance between moon and earth at apogee and perigee (wikipedia has different value to space.com) Wikipedia says https://en.wikipedia.org/wiki/Lunar_distance_(astronomy) ...
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5answers
221 views

Whats the farthest distance a spacecraft has been detected (except by radio)

As far as I understand it, one can not hide spacecraft, because the heat from the engine would be very visible. Now I tried searching for the farthest distance an actual spacecraft has been detected ...
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2answers
87 views

Can we, with arbitrary precision, calculate what's the place on earth that's closest to the sun on a given day?

Can we, with arbitrary precision, calculate what's the place on earth that's closest to the sun on a given date? If so, what's the math like? Say, if I wanted to calculate this within 1m, 10cm or 1cm ...
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1answer
84 views

How have we measured the radius of the Earth (old and new)?

I'd imagine ancient methods are fun exercises in geometry. how has the measurement has evolved over time? The first method is credited to Eratosthenes. He knew that during the summer solstice in ...
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1answer
491 views

How big would Earth be in the sky of the moon?

Imagine standing (somewhere) on the moon's surface, how big would Earth be in the sky of the moon, compared to the image of the moon we see in the Earth's ( night ) sky. What would be the ratio ...
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1answer
410 views

Understanding The Turnover Point of Angular Diameter Distance

I am trying to get a better understanding of cosmological distances, in particular the angular diameter distance which I have also seen referred to as angular size distance. What I am looking for is ...
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1answer
369 views

Are the distances between two celestial bodies the distance of their centers?

For example, the average Sun-Earth distance is 1 AU. Is this the distance between the center of the Sun and the center of the Earth the distance bewteen the surface of the Sun and the surface of the ...
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1answer
61 views

Has the Lyman-alpha forest ever been used to test Arp's theory?

Has the Lyman-alpha forest ever been used to test Halton Arp's theory that quasars are not cosmological but instead are ejected from relatively near-by galaxies? If Arp was right, then the spectra of ...
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1answer
60 views

Spacing of G and K class stars

I was looking at the Wikipedia article "List of potentially habitable exoplanets" and I noticed that many of the closest planets listed(tens or hundreds instead of thousands of light-years away) ...
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1answer
110 views

Problem about finding distance with magnitude given

A star in Pleiades cluster has apparent magnitude of +12 ($m_{star} = +12$) determine it's distance from the sun? (We know the Sun properties such apparent and absolute magnitudes, distance from earth,...
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12answers
16k views

Why don't astronomers use meters to measure astronomical distances?

In astronomy distances are generally expressed in non-metric units like: light-years, astronomical units (AU), parsecs, etc. Why don't they use meters (or multiples thereof) to measure distances, as ...
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3answers
304 views

Is our universe flat?

I heard our universe is flat. Then one question is puzzling in my mind. If our universe is really flat, why we measure distance from any point across in a spherical way. In other words, why we say, ...
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0answers
58 views

Annual parallax for planets

Why can't you measure the annual parallax for planets? Nearby stars tend to have small, yearly oscillations in their apparent positions relative to stars much further away, due to the back-and-forth ...
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1answer
488 views

How to find a Cepheid's pulsation period using its graph?

Basically, I've been seeing these graphs that say: Cepheid Period-Luminosity Relation and the Period axis is supposed to be "logarithmic"; How does this graph work? Since the luminosity of a star ...
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3answers
1k views

What's the farthest object as determined only by parallax?

I'm wondering what the farthest object we know of, as measured only by parallax methods, from either earth or satellite based telescopes, and at either visible light or radio wavelengths. Basically, ...
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3answers
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Could space time curve from the vantage point of earth and out into the universe, and would d = 1 / P in that case give false estimates?

The seventeenth century saw a revolution in astronomy. The invention of the telescope and the acknowledgement of the heliocentric system triggered a race amongst astronomers to measure the parallax of ...
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2answers
164 views

What would be the difference in distance between earth and moon on supermoon night (14 November 2016)

As we all know the usual distance between earth and moon is 384,400 km. But i was thinking how much closer it will be on 14 November 2016, as it will be a supermoon, the brightest and biggest moon in ...
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1answer
1k views

How to calculate the current distance between two planets [duplicate]

I'd like to add a feature to one of my apps that calculates the current distance between the Earth and Mars (or any other planet, for that matter). My google searches have led me to statistics of ...
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1answer
63 views

Dfferent distances to comet 67P

Earlier, I was looking for the current distance from Earth to 67P/Churyumov-Gerasimenko, in order to do a "back of envelope" calculation of signal delay. Not important, but I was somewhat puzzled to ...
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2answers
524 views

Did Gaia actually generate complete light curves for 212 Cepheids in other galaxies?

The recent BBC news item Gaia clocks speedy cosmic expansion says that a recent Gaia measurement of 212 Cepheid variables in other galaxies within the local group yields a Hubble constant of ~73 km/s/...
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1answer
113 views

How far apart are stars in Terzan 5 cluster?

I've just learned about the Terzan 5 globular cluster, which according to Wikipedia has one of the highest star densities in our Galaxy - $10^6\ M_\odot/\mathrm{pc}^3$. Problem is, I've no idea how ...
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2answers
202 views

Stellar Mapping and Coordinates [closed]

Why are the Galactic Coordinates not aligned so that the Axes go through the Long Bar Y-axis aligned to it's longer side, positive with Sol, and the X-axis align to the center of the short length with ...
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2answers
2k views

Exact measurement of a light year

What is the exact measurement of a light year? I searched google for the answer in meters and came up with $9.461\cdot 10^{15}$ meters. When I calculated the answer considering $299\,792\,458 \;\text{...
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1answer
72 views

Is it possible to calculate distance between two objects?

For example: I want to know the distance between Alpha Orionis (Betelgeuse) and Beta Orionis (Rigel). Is this possible? You only know the distance from Earth. May be this is a math problem and not an ...
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3answers
5k views

Is the Sun visible from Proxima Centauri to human eyes?

I know that the light coming from Proxima Centauri is not bright enough to make it naked-eye visible from the Earth. Is the Sun naked-eye visible from Proxima Centauri?