# Questions tagged [distances]

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

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### Photometry templates — what are the templates of?

Redshift measurements from photometric data can be determined using template-fitting (Cosmos website, SDSS photo-z). What does it mean to fit a template to determine redshift? What is the template of?
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### How to find the scale factor on given time in the future if initial distance between source and destination is known

Assume the received redshift $z$ of a photon is known. We then can calculate the initial distance (when the received photon was emitted), the light Travel Distance, the current Distance (proper ...
185 views

### How to actually obtain the parallax angles that are used to determine distances of stars?

I’m trying to understand how to measure the distance to nearby stars using the parallax method. My question is: how do you get the value of the p angle?
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### Comoving Volume Calculation

Suppose I have data from an astronomical survey at redshifts in the range $z = [2,3]$. Suppose that, on average in this range, the data covers an area on the sky of $A=1$ $\mathrm{Mpc}^2$. How would I ...
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### Nearby galaxy distances

Type Ia supernovae are extremely useful in measuring the distance of remote galaxies. It is known that type Ia supernovae always reach the same brilliance at their peak. Like Cepheid variables, they ...
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### How can I find the distance of the tower while standing at my roof?

Whenever someone starts telling about finding distances in astronomy, it all starts with a parallax. The example they give is straightening your hand and see how your thumb changes its location while ...
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### What's the difference between minutes and arcminutes?

I read in trigonometry class that 1 minute is equal to 1/60 degrees. So, 'minute' is an angular unit. But also 'arcminutes' are used to measure seperation between celestial objects and also equals to ...
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### Will the night sky ever be more stars than darkness? [duplicate]

Given enough time, will enough light from distant stars reach Earth so that our night sky will be more than 50% stars?
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### Converting parsecs to light years in the dumbest way possible

I have to convert 132 parsecs to light years and I'm struggling to get the expected result. Here is my method: $132 \text{ pc} = 132'' = 2,2' = 0,03(6)°$ I have an equation for stellar parallax which ...
66 views

### How to compute for Distance Modulus' uncertainty/ies?

This is rather a short question. As we know of; Distance Modulus (DM) $\mu = 5 \log d - 5$ If $d = 168_{-14.9}^{+27.5}$ pc ($3\sigma$ value), how can I possibly compute for $\mu$'s uncertainty? P.S. ...
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### How can you find the distance to a galaxy using right ascension and declination?

For example, Galaxy NGC 3689 has the right ascension of 11:28:11 and declination of +25:39:40.0. Using these values, how can we find the distance to the galaxy? If it helps, its radial velocity is ...
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### Since Proxima Centauri orbits the other two Alpha Centauri stars, will it eventually be farther away from us than they are?

And, if so, will we have to change its name to Distal Centauri ;-) ? Granted, its orbital period around the other two is about 550,000 Earth years, so we have some time....
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### Converting equatorial coordinates to Cartesian coordinates for extragalactic distances

I'm trying to search for galaxy clusters with the friends-of-friends (FoF) algorithm. I have the equatorial coordinates ($\alpha, \delta$) and redshifts ($0.5<z<2.5$) of galaxies that I wish to ...
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### What instruments are used to measure the distance to the Sun?

In the 18th century, the distance to the Sun was measured using the transits of Venus. Nowadays, the timing of radar pulses is used to measure the distance of things in our solar system. What ...
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### Before the 1761 transit, what was our best estimate of the distance to the Sun?

In 1761, many expeditions were launched to determine the distance to the Sun using parallax during the transit of Venus. Prior to the 1761 transit, what was the best estimate for the Earth-Sun ...
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### Units of angle in comoving transverse distance calculation

For two objects at a redshift $z$, I know that the proper distance between them is given by $\delta \theta d_M(z)$, where $d_M(z)$ is the transverse comoving distance. What are the units of the angle ...
330 views

### 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 ...
7k views

### 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 ...