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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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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, ...
Geographos's user avatar
3 votes
1 answer
78 views

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 ...
Futur AE's user avatar
2 votes
0 answers
76 views

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 ...
Michael Borgwardt's user avatar
3 votes
1 answer
487 views

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 ...
James Thiamin's user avatar
0 votes
0 answers
21 views

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 & =\...
Vincent ISOZ's user avatar
6 votes
2 answers
505 views

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 ...
Parseval's user avatar
  • 163
11 votes
1 answer
1k views

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 ...
SmilySunMike's user avatar
7 votes
3 answers
2k views

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 ...
Curious Cat's user avatar
3 votes
2 answers
184 views

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,...
Curious Cat's user avatar
2 votes
1 answer
131 views

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 ...
Curious Cat's user avatar
0 votes
1 answer
235 views

What is the distance between Stephenson 2-18 and Earth?

The distance between Earth and Stephenson 2-18 is 19,570 light years (1.15×10¹⁷ miles). The thing that makes this reasonable is because the Earth is in the Milky Way Galaxy and Stephenson 2-18 is in ...
Astral's user avatar
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7 votes
3 answers
3k views

Distance of the Crab nebula and the speed of light

I am watching a youtube video that says that, there is plenty of historic records that shows that the star, that turned into the Crab nebula, blew up in 1054. According to the video, it is located ...
dotnetCarpenter's user avatar
3 votes
3 answers
832 views

Orion stars distance from Earth

For a textbook I'm creating a figure depicting the distances of Orion constellation's stars from Earth. However i wasn't able to found an Official Scientific catalog of most recent stars distance ...
Vincent ISOZ's user avatar
1 vote
1 answer
148 views

How did scientists decide the boundary of the Milky Way at Edwin Hubble times?

I know Edwin Hubble used Cepheid variables to prove the Andromeda Galaxy is not part of the Milky Way. But how did scientists at that time decide the boundary of the Milky Way? And how did they find ...
Qiulang's user avatar
  • 127
1 vote
1 answer
104 views

Finding an expression for the rate of change of Comoving volume with respect to redshift

I am trying to find the expression for the rate of change of comoving volume with respect to redshift, that is $\frac{\mathrm{d}V_c}{\mathrm{d}z}$. In this paper (Hogg, David W.), the comoving volume ...
noob anomaly's user avatar
1 vote
0 answers
55 views

Large dataset of galaxies redshift, mass, and metallicity?

I'm curious if there is a standard dataset for redshift-mass or redshift-metallicity like there is for redshift-distance with Pantheon+SH0ES. https://github.com/PantheonPlusSH0ES/DataRelease/tree/main/...
MikeHelland's user avatar
1 vote
0 answers
45 views

Where to find data about as many stars as possible?

I need computer-readable data about as many stars as possible, with their: distance to the Earth (or Sun), their masses, and if possible: coordinates, age, brightness distance to the center (...
Dimitre Novatchev's user avatar
-2 votes
1 answer
202 views

Planets revolving counter clockwise around the Sun

Planets revolving around the Sun Hypothetical case: What could have been or no impact if the planets viz Earth, Jupiter, Saturn, Mercury, Venus, Mars, Pluto, Uranus, Neptune in different orbits ...
Prashant Akerkar's user avatar
1 vote
1 answer
513 views

How to find the distance between stars

I wanted to calculate the distance between the end points of the Orion's belt (Alnitak and Mintaka). I searched in the internet and I found out their angular separation to be 2.736°. Then I searched ...
Snack Exchange's user avatar
8 votes
1 answer
2k views

Is Webb or any near-future telescopes like ELT capable of observing redshift changes to confirm General Relativity?

The (Davis and Lineweaver (2003)) "Expanding Confusion" paper states that "the expected change in redshift due to cosmological acceleration or deceleration is only ∆z ∼ 10^(−8) over 100 ...
Glycoversi's user avatar
3 votes
1 answer
105 views

How can we estimate distance of galaxies by only redshift when there are other several factors other than distance to cause redshift

There are different factors for red appearance of different objects in the night sky. Two reasons which I know are Star red by nature Example: red supergiants They emit red light because of their ...
Prajwal D M's user avatar
-1 votes
2 answers
188 views

Why is a megaparsec considered to be a useful distance in astronomy?

Is the megaparsec fundamental or man made? I have read that galaxy clusters are megaparsecs wide for example.
user avatar
4 votes
1 answer
222 views

How can I get a list of the closest x stars and their distances from the Gaia ESA Archive using Python?

I've been trying to find this out for a while now, but I'm making zero progress. I really struggle to find good documentation for the query language, and even in the astroquery library I can't find ...
Outis Nemo's user avatar
2 votes
0 answers
35 views

Which value of the apparent magnitude do I use from a Supernova light curve

I am trying to get the distance modulus from a light curve of a supernova and obviously the apparent magnitude changes with time. Not only that but there are so many filters with different mags. So my ...
Abdullah's user avatar
2 votes
3 answers
499 views

How to calculate distance between stars?

I have data on nearby stars, including galactic coordinates and distance from Sun. And I have a dilemma. In a story I'm writing, I have two starfaring alien civilisations. One originates from a planet ...
Krišjānis Liepiņš's user avatar
21 votes
2 answers
4k views

What equation tells you how far in space you can go from a point and return?

We know that hubble expansion increases the distance between points in space, and that the cosmological event horizon represents the distance from the observer at which objects are receding faster ...
user52978's user avatar
  • 313
3 votes
1 answer
98 views

How to obtain luminosity distance from a light curve

I have some light curve data of a SN Ia from which I want to find the luminosity distance $D_L$. How can I do it mathematically? I'll then try to implement the answer using Python.
Abdullah's user avatar
2 votes
1 answer
120 views

How to calculate the distance from earth and Vega in 1000 years?

Hello I read that Vega is getting closer to earth. I would like to learn how to calculate its displacement and calculate the galactic coordinates that it will have next year or in 1000 years. Knowing ...
Cynhnab Exilé's user avatar
0 votes
1 answer
77 views

Calculate the distance between two planets eliptical orbit point

What is the distance between Saturn's moons Polydeuces and Dione, Looking for Kilometers if one was to travel Nearest and farthest based on orbit. Best I can find: "Polydeuces can get as close ...
PatTracy's user avatar
4 votes
1 answer
126 views

See Venus in daylight

At what distance (in angular degrees) from the Sun, could we see Venus, in mid daylight, with a pair of binoculars (7x50)?
Jacquelin Hardy's user avatar
3 votes
0 answers
181 views

Determining the distance to the Moon from parallax using the following information

How could I determine the distance from the Earth to the moon by using the method of simultaneous parallax? I know the right ascension and declination as seen from two different points on earth. I ...
Luis Sarmiento's user avatar
1 vote
1 answer
37 views

How can a time-like trajectory be calculated using the Friedmann-Robertson-Walker metric?

Using the following FRW metric, $$ds^2=-c^2dt^2+R^2(t)(d\chi^2+f(\chi)d\Omega)$$ and considering $d\Omega=0$ from now on, it is clear that for a light-like trajectory, the equation must read $ds^2=0$ ...
user9867's user avatar
  • 147
6 votes
3 answers
3k views

What is the apparent size of Earth from the Sun?

Heatwaves have been in the news in recent years. I found it amazing to consider that the energy from the Sun is enough to kill you, when only a tiny fraction of its radiation reaches Earth. Then I ...
albertoeda's user avatar
2 votes
1 answer
268 views

3d distance between the Galaxies inside the galaxy cluster

I am currently working on the dynamics of the galaxy cluster, so i am trying to get the distance between the galaxies inside the galaxy cluster from its centre. As a input i have RA , DEC and Z (...
Atul's user avatar
  • 41
11 votes
1 answer
226 views

Farthest distance two objects are "gravitationally bounded", considering expansion of the Universe

The narrative is: "on greater scales the expansion of the Universe dominates, but on smaller scales gravitationally bounded objects still stay bounded". But how small is meant by "...
Heopps's user avatar
  • 647
9 votes
4 answers
2k views

Does stellar parallax only occur parallel to the ecliptic?

Does stellar parallax only occur parallel to the ecliptic, or has it been observed in other directions, too?
Geremia's user avatar
  • 219
9 votes
2 answers
3k views

What would Betelgeuse look like from Earth if it was at the edge of the Solar System

If we parked Betelgeuse just outside the Solar System, how big would it look from Earth?
Jordan's user avatar
  • 388
5 votes
2 answers
583 views

Distance from Earth to Mars at time of November 8, 2022 lunar eclipse maximum

I’m looking for the “exact” distance from the Earth to Mars, at the moment of the lunar eclipse maximum earlier this week (November 8, 2022). As many significant digits as you can muster. Between the ...
Bruce Simonson's user avatar
3 votes
1 answer
156 views

How dark is the side of the Moon facing away from the Sun? ( I don't mean the far side)

Remember, the actual "dark side" of the Moon is not the far side, facing away from us that we can't see, but rather it's the side that faces away from the Sun that is illuminating it.​
james taylor's user avatar
3 votes
2 answers
550 views

How can I convert a galaxy arcmin to light years?

https://en.wikipedia.org/wiki/List_of_largest_galaxies says galaxy ESO 383-76 has a MA diameter of 1,764,000 light years based on information from https://ned.ipac.caltech.edu/cgi-bin/objsearch?...
MiscellaneousUser's user avatar
3 votes
2 answers
3k views

What is the difference between the Synodic & the Sidereal Periods?

While studying Spherical Astronomy, I came to know the two terms: 'Synodic Period' & 'Sidereal Period'. Both were referring to the returning of a particular celestial body on the sky or the ...
user avatar
3 votes
1 answer
314 views

Redshift distance proportionality at high Z and need for "mighty mouse" galaxies?

Allegedly supported by some evidence from the new James Webb space telescope physicist Eric Lerner has written an article that have garnered some attention. He writes that: "Put another way, the ...
Agerhell's user avatar
  • 457
2 votes
0 answers
31 views

How much does foreground clumping affect the estimated sizes of high-redshift objects?

I've always converted angular to linear size by using the angular-diameter distance without really thinking about it. But in light of recent stories about high-$z$ galaxies observed by JWST being ...
benrg's user avatar
  • 3,862
2 votes
1 answer
128 views

Distance of distant galaxies

Can two galaxies, one with a redshift of 7 and the other a redshift of 8 have the same angular distance (distance from the Earth during the emission of the observed photons)? If not why ? Example: ...
Sebastyen Laroche's user avatar
5 votes
2 answers
188 views

Measurement unit of coordinate systems in astronomy

Nearly all of the coordinate system I have studied in Positional astronomy use the degree system. This makes me curious about why astronomers prefer degrees over radians as we know that Radian is a ...
Particle king's user avatar
3 votes
1 answer
199 views

Space travel to distant stars

This is more of a hypothetical question. Say space travel at near light speed was possible, and I wanted to travel in my spaceship to some distant star many light years away. At the time and location ...
Tachyon's user avatar
  • 133
4 votes
1 answer
146 views

Is there something close to a consensus on Earth-Sun annual distance increase (speed)?

I've seen estimates varying by an order of magnitude, e.g. (New Scientist) Having such a precise yardstick allowed Russian dynamicists Gregoriy A. Krasinsky and Victor A. Brumberg to calculate, in ...
against very long user names's user avatar
10 votes
1 answer
114 views

How do astronomers distinguish between Cepheids and other types of variable stars?

So my understanding of how Cepheid is used as standard candle to determine distance of galaxies is like this: Astronomers observe a galaxy, notice an object within that galaxy whose brightness ...
mudiwii's user avatar
  • 101
43 votes
6 answers
7k views

In this image taken by Voyager 1, which is closer: the earth or the moon?

NASA reports this photo was taken 19 Sep 1977 by Voyager 1: It doesn't strike me as obvious how to determine which celestial body is closer to Voyager 1 as the photo was taken. My (not very ...
Rebecca J. Stones's user avatar
1 vote
1 answer
465 views

Distribution function for distance to nearest stars from any given star in our galaxy

If I pick any random star in our galaxy, what is the mean & std dev of distances from that star to its, say, 5 nearest neighbors? As this distribution likely depends on the distance from the ...
Carl Witthoft's user avatar

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