Questions tagged [distances]

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

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How to calculate the distance to the galaxy center in an extra-galactic system presenting an inclinaison angle?

I have an observational image of a galaxy and I need to draw its radial profile. This galaxy is observed with a known inclinaison angle, INC, and with a position angle, PA. To realize the profile, I ...
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Calculating distance from center of mass of two stars in a binary system

I am confused on how to calculate the distances for each star in a binary system to their centre of mass. I am trying to solve it from a book I am reading which shows the solution but I do not ...
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How did Eratosthenes know that the sun is far away?

The famous measurements and calculations done by Eratosthenes around 300 BC are very widely known. He concluded correctly that the circumference of the Earth is about $252\,000$ times the length of an ...
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What error bar / confidence level is generally reported in galaxy distances?

In reporting distances of galaxies, what are the typical error bars and associated confidence levels?
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Software apps for calculating distances between planets

Are there somewhere any software apps for calculating distances between any planets in our solar system?
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How close would a Sunlike star have to be in order to be dangerous to look at it through a spyglass?

Alpha Centauri A which has an about 50% higher luminosity than the Sun is obviously undangerous to look at through a handheld telescope, at about 4.4 ly distance. How close would a yellow dwarf have ...
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How to calculate how much of the Earth's (or another planet's) surface is visible? [duplicate]

My latter three questions remain unanswered but I won't wait with this one, I'd like to learn the formula and hope this question gets an answer. As you're going higher respectively farther away from ...
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Where are the two recently confirmed unusual brown dwarfs?

The News report of two confirmed unusual T-type brown dwarfs but they don't tell where in space or on the night sky they were found or how far they are from the Earth/Sun. The brown dwarfs are WISE ...
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87 views

At what distance wouldn't the Sun cast a visible shadow anymore? [closed]

How far from the Sun would a (dwarf) planet have to be so that the Sun is dim enough that it doesn't cast a shadow when you're standing on the planet? What magnitude is the border in brightness beyond ...
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Were radio spectroscopic observations ever used to first measure a distance successfully?

Usually, especially for an extragalactic object, its redshift is determined by optical spectroscopic redshift. But the angular resolution of early radio observations is poor and an optical counterpart ...
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Expresion of comoving distance

I have a simple question : How to prove the following relation : The comoving distance to an object at redshift $z$ can be computed as $$r(z)=\dfrac{c}{H_{0}} \int_{0}^{z} \dfrac{\mathrm{d} z}{E(z)}$...
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Distance and absolute brightness

This is an exercise from a text, I’m learning from and I can’t understand it so I’m asking just to develop my knowledge: The explosion of V603 Aql (Nova Aquilae) took place in June 1918. The nova ...
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What would Jupiter look like from a Galilean moon?

If I were on a Galilean moon of Jupiter, like Europa or Ganymede, what would the planet look like? (Let's say I'm on a space station that provides atmosphere to make it slightly less unrealistic.) ...
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Closest star system to Alpha Centauri?

The closest star system to our Solar System is Alpha Centauri. But is our Solar System the closest star system to Alpha Centuari? If not, which star system is?
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Do parsecs scale as an inverse proportion with parallax angle?

high school student here. In astronomy my teacher says that if the parsec angle ($\alpha$) of a star is 1/50 arcsecond, then that star is 50 parsecs away. I'm not really convinced - calculation of ...
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Determine distance to Moon after diurnal parallax?

So, I want to find the distance to the Moon/any body after performing the correction for diurnal parallax. Unfortunately, the resources I have do not cover how to do this. Is there an easy algorithm ...
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79 views

How do we determine a redshift error?

I am struggling to calculate the redshift error of a galaxy. I was able to determine the redshifts of the absorption and emission lines from the galaxy's spectrum and then took the average of the ...
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What was that single file line formation of flashing plane lights flying in the sky at night? [duplicate]

It was here on the west coast at 5 am pacific standard time when I went outside for a smoke when out of the corner of my eye what looks like a plane with flashing lights going across the sky when all ...
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Could you use luminosity changes over time to calculate distance?

More specifically: if you know your movement relative to a body, could you use the inverse square law to calculate distance? Since if you are distance $D$ away and you move $d$, $\Delta L \propto (D-d)...
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Calculating distance of comet C/2019 Y4 (ATLAS)

SO, I decided I would take some pictures of the comet C/2019 Y4 last night. Afterwards, I thought I would try and do a rough estimation of distance based on my observations. I don't have any fancy ...
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I sighted a group of satélites moving in a interesting pattern in a way I never seen from this area where I live is this posible? [duplicate]

I live in the rural area of the state of São Paulo in brasil (mata atlántica). the sky is absolutely clear, when there is no clouds you see the milky way perfectly and a sky full of stars. I just ...
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Volume of Galaxies

Pretty much awkward question though. I would like to ask how is the volume of a Galaxy X is measured? For example consider milky way, what are the techniques to measure the same? How accurate and ...
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Information about known objects in the Universe

I want to retrieve coordinates, photos, and information (size, atmosphere composition, distance from Earth, etc.) about every known object in the universe. Ideally, the information is available via an ...
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What's the most distant object we've measured by parallax? [duplicate]

The openstax Astronomy textbook says that when the Gaia mission is complete, we'll have parallax measurements to 30k light years. Do we have those now? What's the most distant object astronomers have ...
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If the distance between galaxies is increasing and the speed of light is constant will the most of the light from the universe ever reach us?

Will the light from other galaxies ever reach us if the universe is expanding?
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What star is the closest to Betelgeuse?

Based on this answer, I should be able to figure out this question, if I know the distance between Betelgeuse and its nearest neighbor. So what is Betelgeuse's nearest neighbor? I do mean the ...
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206 views

Was the Earth-Sun distance ever calculated based on the time difference between night and day?

If we define sunrise and sunset as the time when the center of the Sun goes over the horizon then day time is a little bit shorter than night time because from a single point one cannot see a complete ...
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Are there celestial bodies that are about as far away as the Sun?

Just curious. The Sun is 500 light seconds away from the Earth depending on time of the year. The orbit of Mars is about 50% as far as the Sun, the orbit of Vesta about 150%. Is there / Are there ...
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91 views

Earth as a grain of sand

If Earth was a grain of sand in Buenos Aires in what point in this observable universe map would be LA be?
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304 views

Distance to Proxima Centauri (Gaia VS New Horizons parallax program)

The current best parallax measurement for the nearest star to the Solar System, Proxima Centauri, has been given by the European Space Agency's Gaia mission. This is $768.5004\; \pm \; 0.2030 \; mas$ (...
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Minimum apparent magnitude of galaxy

currently I'm working on astronomy problem which deals with finding redshift of a galaxy. But the first part asks to derermine apparent magnitude of a galaxy: Find what should be the minimum ...
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Is Olbers' Paradox Nonsense? [closed]

Ok, this is a bold question, I know. But, let me explain: After first hearing about Olbers' paradox, I found that something seemed 'off' about it, so I looked into the subject as much as my skills (...
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Did a galaxy get discovered more than 30 billion light-years away? How does one observe light older than the estimated age of the universe? [duplicate]

I'm more into questioning mainstream science and pseudo-science to remain open-minded. Why is it that we are seeing light 30 billion light years away; when the estimated age of the universe is much ...
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How many galaxies have had their distance determined using SNIa?

Supernovae of type Ia can be used as standard candles to determine extra-galactic distances. But these event only occur (roughly) once every 200 years in any given galaxy and rapidly fade away. So to ...
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How the depth[Mpc] is obtained from the redshift

I read this paper. In this paper, they show the three-dimensional distribution of the [OII] emitters. It is mentioned that The depth in z-axis is converted from the redshift, which is estimated from ...
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1answer
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Expansion of the universe and visibility of distant galaxies [duplicate]

The universe expands at an accelerating rate, which makes me wonder if at a certain point the speed of expansion between two points will exceed the speed of light. In that case, it might eventually ...
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How to determine the orbital period of an asteroid using Kepler laws given its orbit's radius?

Given that the mean distance of an asteroid from the Sun is $450 \times 10^6$ km is it possible that the asteroid completes one rotation around the Sun in two years? According to the third law of ...
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Why is there “modulus” word in the “distance modulus” term?

The difference of apparent (m) and absolute (M) magnitudes of an object is called "distance modulus", which is related to the distance $d$ to the object in parsecs with equation $$m - M = 5 \log \Big(...
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1answer
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How to convert from FELO-HEL to Km/s?

I am using DS9 to calculate the rotational velocity of a galaxy. I have 21cm cube and I used DS9 to plot this graph I do not understand what is FELO-HEL! and I want to convert the units from FELO-...
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1answer
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How was Cassini able to measure and use the Earth-Mars distance to get the Earth-Sun distance?

How was Cassini able to measure and use he distance between Earth and Mars to get the Earth-Sun distance? How were the ratios of Earth-Mars and Earth-Sun calculated then? Given Kepler's laws all we ...
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1answer
42 views

Redshift, velocity, distance

How are redshift, (recessional) velocity and distance of a galaxy related? I understand what v=HD states. So I assume that Hubble measured a direct relation between the distance and recessional ...
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1answer
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What is the relative velocity between planets in different solar systems?

Is it possible to estimate what the difference in velocity is between the earth and another convenient exoplanet? Or perhaps just our star and a near neighbour? I'd be curious where I could find the ...
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199 views

How to create unique 3d star maps?

I have been trying to create a calculator which finds the distance between two stars that the user chooses. But I'm having a hard time visualizing where these stars are in real space. Do you know of ...
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Turn celestial coordinates into light years

I have a question about celestial coordinates. I have been working on a calculator that takes in different stars and tells you how far apart they are, and their coordinates (x, y, z). But I didn't ...
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How does time dilation from a large body fall off? [closed]

A magnetic fields generally fall off as 1 / r^3 rather than 1 / r^2 for gravity. How does time dilation fall off from a large body? Where would the gravity and magnetic field line be in this chart ...
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How to calculate the distance to galaxies with standard candles?

I was wondering how the distance in Mpc could be calculated between Earth and a galaxy using the luminosity provided? Do not be shy to use all math necessary :)
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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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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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76 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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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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