Questions tagged [distances]
Questions regarding the amount of space between two objects, the units, or measurement thereof.
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What are we misunderstanding about the scale factor-redshift relation? [closed]
If the scale factor as a function of time represents or is equal to the average distance between the galaxies, then it increases altogether with the CMB redshift $z$, but it also must be equal to the ...
user57748
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How to count observable number of galaxies at a given latitude considering interstellar extinction?
If galaxies are uniformly distributed in space, then in the absence of extinction, the number of galaxies per square degree brighter than magnitude m is given by $$\log_{N_0}(m) = 0.6m + C$$
How will ...
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Distance from Earth to Sun averaging method in AU definition
Historically, $1~\text{AU}$ is defined as $1/2(r_{min}+r_{max})$, but the problem is that this is not the average radius if Earth orbit would be transformed into circle, with Sun at the center and ...
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How to calculate moon's distance and parallax in it's altitude
I'm trying to calculate moon's parallax in it's altitude depending on the day I need and I followed this formula by geoastro.de Basics of Positional Astronomy and Ephemerides
but I need to calculate ...
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How close will Pluto come to Earth this year (2024)?
For reasons associated with a 1943 story, I am keen to find how close Earth will come to Pluto in 2024. According to https://theskylive.com/pluto-tracker today (21-May-2024), Pluto is now slowly ...
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Calculating lunar parallax based on a distance between two objects at certain latitude
I want to compute lunar parallax based on the distance between two points. In fact I know the formula, but I guess they're explained wrong.
By looking at the image below we can see the polar radius, ...
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Easy guideline for using JPL Horizons DE431 for planets in aphelion and perihelion from 11000 BC to 16000 AD?
Can someone give me a step by step Guide how to use JPL DE431 or DE441 as a Beginner.
I tried the Horizons website app and Webgeocalc but it didn't showed understandable Information.
This websites ...
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Closest/farthest point where the sun stops being the brightest star?
Which is the closest point to the Sun where it's not the brightest star anymore?
My intuition is that this is either on a direct line between the Sun and Alpha Centauri, or between the Sun and Sirius ...
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Measure the radius of the earth using the sun?
Can someone tell me why this would or would not work?
I have a sun spotter device that projects an image of the sun onto a piece of paper using a lens and some mirrors. When you use the device it’s ...
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Luminosity distance in a FRW Universe
In the following presentation:
https://www.slac.stanford.edu/econf/C0307282/lec_notes/pinto/pinto.pdf
we have the relation for the luminosity distance in a FRW universe:
\begin{aligned}
D_L & =\...
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Calculating Earth-Sun distance only using trigonometry and terrestrial measurements
I have an interest in mathematics and astronomy, and my curiosity was piqued by the methodologies employed in contemporary solar distance measurement. Current practices use sophisticated instruments ...
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Why was the standard distance set to 10 parsec and not simply to 1 parsec?
On closer inspection of the absolute visual magnitude and the apparent visual magnitude of the sun, I noticed that their magnitude range (4.83 + 26.74 = 31.57) exactly matches the human eye. The ...
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How do we work out the light travel time on a cosmic scale?
I just read this article in the AUSTRALIAN SKY & TELESCOPE magazine, Nov/Dec 2022 Issue 140, on P16, KEEP YOUR DISTANCE: How far away are the objects we see in the universe? And on P23:
"And ...
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What is Hubble's parameter/constant H0 supposed to mean, exactly? [duplicate]
Surely it must mean that every second each Mpc expands by that much. Well what else, could it be.
So if the expansion is accelerating, then how can H0 be decreasing!?
Let's look at Hubble's law: v=H0D,...
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Why are distant type Ia supernovae dimmer than expected?
Why are the (extremely) distant type Ia supernovae dimmer than expected?
Relative to what? Their cosmological red shift? Well, what else.
Please don't just say "Because the expansion is ...
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