Questions tagged [distances]

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

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2answers
61 views

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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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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How do you calculate comoving distance and light's travel distance? According to the formulae below?

According to Wikipedia, Distance measures (cosmology), Comoving distance: $${\displaystyle d_{C}(z)=d_{H}\int _{0}^{z}{\frac {dz'}{E(z')}}}$$ Light-travel distance: $${\displaystyle d_{T}(z)=d_{H}\int ...
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How long does it take for a galaxy (or other object) to disappear behind the cosmic sight horizon?

After looking at this question, I am wondering, how long does it take for a galaxy or other space object, to disappear from our view from the Milky Way due to the expansion of the universe? Assume GN-...
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How reliable is it to use globular cluster lumniosity function as a distance indicator?

I have seen many research suggesting that GCLF can be used as a secondary distance indicator for extragalactic objects. However, this method seems to be only reliable when the GCs in use come from say,...
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Which celestial body is able to come closest to Pluto?

Other than Pluto's moons (including Charon), which known body comes closest to Pluto, and how close? Neptune doesn't come closer than 16 au. What about Orcus, whose orbit is similar to Pluto's, or ...
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1answer
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Approximate spectral type and luminosity given apparent magnitude and distance

I am looking at the data acquired from the Gaia DR2 survey. I found that most of the stars had their distance and apparent magnitude catalogued, but not their spectral type and luminosity class. Is ...
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What is the mean separation between a star and its closest neighbor in the Milky Way halo?

My question is inspired by this previous question, Are there any stars that orbit perpendicular to the Milky Way's galactic plane?. In the great answer posted by @ConnorGarcia, one commenter said he ...
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How do you correct the Period-Luminosity relationship for metallicity?

Refer to the link: https://www.astro.utoronto.ca/DDO/research/cepheids/cepheids.html Tha author has used the relationship $M_V=-2.902log(P)-1.203$. It is mentioned that this is not corrected for ...
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SIMBAD TAP queries seem to indicate there are no distance measurements for a great many nearby stars, including Alpha Centauri or Barnard's Star

I'm attempting to create a map of all objects within 50LY, including main-sequence stars, binaries, planemos, etc. As such, I'm trying to do it all from first principles, building a micro-ETL to ...
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1answer
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How precisely we know the Gaia spacecraft baseline? [Question related to Planet 9 and the cosmic distance ladder]

The European Space Agency mission Gaia is performing an outstanding job by measuring the parallaxes of almost 2 billion stars, many of which are thousands of light years away from the Sun. For this ...
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How is it that Jupiter and Saturn appear the same size in the sky?

Saturn is twice as far as Jupiter is from Earth according to a quick Google search. But I needed to understand why do they appear as if they are the same size. I mean as if they are not far apart. For ...
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1answer
51 views

Computing the over-density of Lyman-alpha emitters

Let's assume that I have observations of $N$ galaxies in a projected area $A$, within a redshift range $\Delta z = z_{max} - z_{min}$. What is the correct way of computing their number volume density? ...
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1answer
217 views

Minimum distance between planets

In our solar system, MOIDs (minimum orbital intersection distance) of different planets reach a minimum of ~30 million miles (Mercury and Venus). However, other star systems have more compact planets. ...
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How to find the distance between two galaxies from ra and dec and redshift [duplicate]

I have ra and dec and corresponding redshift of galaxies. I would like to calculate the distance between two galaxies. I did like this to find the nearest neighbour galaxies. Suppose I am trying to ...
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1answer
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Type II supernovae as a distance indicator

Could someone explain in brief exactly how type II supernovae could be used as distance indicators? as in simply the formulae used and how they are employed? I know there are certain methods based on ...
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1answer
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How to improve the precision in a star's distance

When I use the Gaia star catalogue, the parallax values often have large uncertainties which, therefore, leads to a large uncertainty for the distances to the stars. If you were interested in the ...
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3answers
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What's the farthest point humans have explored?

By using powerful telescopes on land and space, what's the farthest point humans have explored or viewed?
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1answer
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How do you go from transit times to Earth-Sun distance?

In the early 18th century, Halley described a method to determine the value of the astronomical unit by observing a transit of Venus from multiple locations on Earth. How do you go from the transit ...
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1answer
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How were the distances to stars measure before parallax?

A comment under When was the distance to a star measured for the first time without using parallax? mentions that the distance to stars was measured before parallax was possible. How was this done?
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How did we determine the distance of the CMB?

The cosmological microwave background (CMB) is the oldest electromagnetic radiation in the universe. How do we know how far away the CMB is?
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When was the distance to a star measured for the first time without using parallax?

This is somewhat of a follow-up to When was the parallax of a star first measured? Once the distance to the nearest stars was determined, it was possible to discover physical properties of stars (such ...
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Why is WISE J0521+1025's distance so uncertain?

If you look at the Wikipedia page List of nearest stars and brown dwarfs , you'll notice that all stars mentioned in the list have a very precise value; all are $\pm0.02$ ly (except for GJ 1005, but ...
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From what distances do the atoms in you come from?

If the atoms of a human come from stars, comets, nebulas and magnetrons, then what is the greatest distance that two atoms of a human can possibly have been away from each other previously? Perhaps ...
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1answer
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What is the distance from Alpha Centauri to Barnard's Star?

Alpha Centauri AB is the closest star system to Earth (4.366 ly), followed closely by Barnard's star (5.988 ly). The closest star system to Alpha Centauri is Luhman 16 (3.8 ly from α Cen). So I am ...
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Transverse Comoving distance

I don't understand the link between the comoving distance and transverse comoving distance : how can they be equal ? Here an example of definition that I have found : Angular Diameter Distance : The ...
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1answer
224 views

How can you determine the distance of a star using the magnitude equation?

In high school we are undergoing a short course about astronomy. It is stated that you can use the apparent and absolute magnitude (m, M) to get a distance (D) of a star, with the formula $$m - M = 5 \...
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1answer
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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 ...
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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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1answer
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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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1answer
142 views

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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1answer
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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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1answer
121 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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1answer
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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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1answer
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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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3answers
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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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1answer
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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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