Questions tagged [distances]

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

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2 votes
1 answer
52 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 ...
2 votes
0 answers
26 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 ...
2 votes
3 answers
176 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 ...
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 ...
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3 votes
1 answer
34 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.
2 votes
1 answer
47 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 ...
0 votes
1 answer
52 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 ...
3 votes
1 answer
99 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)?
3 votes
0 answers
109 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 ...
1 vote
1 answer
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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 $ds^2=0$ ...
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6 votes
3 answers
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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 ...
2 votes
1 answer
98 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 (...
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10 votes
1 answer
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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 "...
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9 votes
4 answers
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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?
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9 votes
2 answers
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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?
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5 votes
2 answers
571 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 ...
3 votes
1 answer
124 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.​
3 votes
2 answers
219 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?...
3 votes
2 answers
695 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 ...
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3 votes
1 answer
201 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 ...
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2 votes
0 answers
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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 ...
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2 votes
1 answer
83 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: ...
4 votes
2 answers
118 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 ...
3 votes
1 answer
172 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 ...
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4 votes
1 answer
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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 ...
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10 votes
1 answer
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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 ...
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40 votes
6 answers
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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 ...
1 vote
1 answer
279 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 ...
3 votes
1 answer
140 views

Is V616 Monocerotis the closest black hole?

Now that HR 6819 has been found not to be a black hole after all, does that currently leave V616 Monocerotis as the closest known stellar mass black hole?
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1 vote
1 answer
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How do we measure the current positions of galaxies?

I do wonder how do we measure current position of galaxies since all the information transfer speed of the universe is limited by the light speed. My understanding is the we can only measure the ...
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4 votes
1 answer
63 views

How to build an adjacency matrix of stars connectivity from their physical kpc distances?

I'm probing into the Illustris API, and gathering information from a specific cosmos simulation, for a given redshift value. This is how I request the api: ...
3 votes
0 answers
79 views

Star charts showing distances instead of apparent magnitudes?

I am curious as to what star charts would look like, if instead of scaling the size of dots by apparent magnitude, the size of dots were scaled by actual distance from earth. It would be nice to ...
7 votes
3 answers
1k views

Compute Distance Between Stars

If I have the following information about star A and Star B, how can I compute the distance between A and B? Distance from Sol for Star A Right Ascension/Declination of Star A Parallax/Absolute ...
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9 votes
2 answers
4k views

Am I miscalculating distance to Moon?

The Moon's orbital period is generally given as 27.3 days, and the radius of Geostationary orbit as 26,200 miles. However, using Kepler's Third Law, if I raise 27.3 to the power of 2/3, and multiply ...
1 vote
1 answer
129 views

Is luminosity distance related to both heliocentric redshift and CMB restframe redshift?

The luminosity distance $$d_l=(1+z)r(z)\ ,$$ where $r(z)$ is given by $$r(z)=cH^{-1}_0\int_{0}^{z}\frac{dz'}{E(z')}\ .$$ When I use the SNe dataset "Pantheon", I find there are two redshifts:...
6 votes
3 answers
814 views

Can the Event Horizon Telescope been used to find intergalactic distances?

Now that we have the Event Horizon Telescope (EHT), why can't we just guess and check intergalactic distances by changing the EHT's focal length? For instance why don't we take another picture of M87,...
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2 votes
1 answer
294 views

How to calculate distance to other galaxies using type 1a supernova?

This is for a project in astronomy with extensive data analysis. How should I calculate the distance of galaxies using AGN and supernova Ia? I am using the data from dr17 of SDSS.
1 vote
1 answer
84 views

What exactly is the estimated distance to a far-off object when they say '50 Mpc/h' or '50 Mpc h^-1'? Is it less than 50 Mpc? Do you ÷ by 67 or 74?

Several recent arxiv.org papers I read mention distances to very distant objects in Mpc (megaparsecs) divided by Hubble's 'constant'.... Does that mean we should divide the Mpc or Gpc (gigaparsecs) by ...
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6 votes
1 answer
167 views

The two channels of Type Ia SNe and their use as standard candles

As we know, Type Ia supernovae are used as standard candles since their absolute luminosities are expected to be roughly constant. The consensus model, as seen from the Wikipedia page, suggests this ...
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3 votes
1 answer
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What is that stuff around Andromeda Galaxy

I know Andromeda Galaxy is one of the closest galaxies to our Milky Way, but there are photographs showing it to be surrounded by smaller bodies. Are there any that are closer, or are they all farther ...
2 votes
2 answers
401 views

Horizontal and equatorial coordinate systems

What is the difference between horizontal and equatorial coordinate systems apart from the notations (azimuth, altitude) and (right ascension and declination angle)? Please provide some measurements ...
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2 votes
1 answer
279 views

Calculating distance to High Redshift Galaxies based on observations

I am aware that we need to account for the expansion of the universe, changing $H$, the relativistic redshift eqn: $1+z=\sqrt{\frac{c+v}{c-v}}$ and so on, but can we accurately calculate velocity ...
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0 votes
1 answer
87 views

Radar technique for distant objects

If we want to detect the distance to an object using radar, we can do it only for objects inside the solar system, otherwise the returning signal would be too weak to detect. On the other hand, we are ...
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-2 votes
1 answer
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What is Saturn’s apparent magnitude at its brightest when viewed from Uranus?

Considering that the apparent magnitude scale is an inverted scale; what is the lowest apparent magnitude of Saturn that can be seen from Uranus. We are of course talking about when Saturn is viewed ...
-2 votes
3 answers
249 views

If we could fly off edge of observable universe what would happen? [closed]

If we could be at the edge of expanding universe in a fast space ship such that we could go beyond the edge, what does the science think we might experience? Would we still be floating in space? Would ...
0 votes
1 answer
148 views

Why does apparent magnitudes get increased fourfold when distances get halved, instead of simply getting doubled?

This website explains: The apparent brightness of a star is proportional to 1 divided by its distance squared. That is, if you took a star and moved it twice as far away, it would appear 1/4 as ...
2 votes
1 answer
273 views

Is it more accurate to measure distances from Mars?

I'm trying to figure out answer to this task: At a certain level of development of the Martian civilization, scientists of this planet began to measure distances. Will their measurements be more or ...
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12 votes
4 answers
3k views

Could Neptune be viewed with the naked eye from Uranus?

Which star or planet in our night sky can match what Neptune would look like when viewed from Uranus, or one of its moons? The answer would be for the most favourable condition, which is when Neptune ...
36 votes
8 answers
7k views

Is saying that what we see of an object 1 light-year away happened 1 year "ago" in any a way useful view of the universe?

Since the speed of light is the speed of causality, the "now" state of the a faraway object for an observer should be the exact point at which its light reaches the observer, for literally ...
3 votes
1 answer
251 views

Calculating the present comoving distance or light travel distance of distant objects when only one value is given?

I was wondering how to calculate either the present comoving distance or the light travel distance when the source material only gives one value? Is there and an online calculator or simple equation ...

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