Questions tagged [distances]
Questions regarding the amount of space between two objects, the units, or measurement thereof.
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What is the farthest object we've been able to bounce signals off of to date?
I know people bounced lasers off of Venus and Mercury in 1960s in order to test the Shapiro delay. Since then, we've developed higher power lasers and radio transmitters (Bolshakovo transmitter).
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Is the diameter of the observable universe a relative quantity?
The diameter of my observable universe is 90 billion ly measured in proper distance. But isn't lenght a relative quantity in the theory of Relativity? Could an observer moving at a different velocity ...
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Do objects look larger the further away they are, beyond z=1?
I stumbled upon this text which illustrates and says:
We find that as the object is moved to higher redshifts its angular
size first decreases (as naively expected) but soon begins to increase
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If we were to see the Sun with our naked eyes from the Orion belt, would all planets be encompassed inside the star? Is this calculable?
When we see a star it looks much bigger in diameter to us than it really is, this picture (extracted from here) explains what I mean:
Notice that the point we see in the skynight, represented by the ...
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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 ...
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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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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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Why don't we see more supernovae in our galaxy?
I found this on the Wikipedia page on supernovae:
The total supernova rate in our galaxy is estimated to be about 4.6 per century, or one every 22 years, although we haven't actually observed one ...
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How do we know that the intrinsic brightness of Cepheid variables corresponds to their period?
As I understand it, beyond parallax the next way of estimating the distance to astronomical objects is by using a relationship between the period and intrinsic luminosity of Cepheid variables. How do ...
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When we say a galaxy is 200 million light years away, does this account for the expansion of space in the time it took it's light to reach us?
When we see a distant galaxy, the light we are watching started it's journey millions of years ago. In all that time, space has been expanding, so if the initial distance was A, right now the distance ...
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How far apart can two people watch the moon simultaneously?
Obviously there's a limited part of earths surface where the moon is visible at any given time. I imagine the area of this surface would be a lot smaller than the area where the sun is visible at any ...
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What would the night sky look like if Earth orbited an intergalactic star?
If the Earth and its host star were located exactly in-between the Milky Way and Andromeda would the night sky be completely void of light?
Would stars be visible to the unaided eye?
So there could ...
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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 ...
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3D Positions of Nearby Stars
I have come across a number of star catalogs that list stars by right ascension and declination, along with other data such as magnitude.
Is there a star catalog that lists the 3-D position of stars (...
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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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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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Calculate the true diameter of stars from photographic plate
I am reading the book "Fourier Analysis" from T. W. Körner, and in chapter 95, he explains how you can compute the diameter of stars on a photographic plate. He says that "Since observations of the ...
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Can we see the stars at the edge of the Milkyway?
This question proved much more difficult to formulate than I initially imagined. It concerns how far out in the Milky Way that we actually see with different telescopes. I know the Milky Way disk is ...
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Does Tobler's First Law of Geography Apply to Star Composition?
There is a principle in Geography called Tobler's First Law of Geography which states that "Everything is related to everything else, but near things are more related than distant things."
Does this ...
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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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What is difference between horizon and comoving distances?
I wonder if there a difference between horizon and comoving distances in cosmology ?
I mean both correspond to a null geodesic $(ds^2=0)$ right ?
$$d_{horizon} (t) =a(t) \int\limits_{0}^{r} \frac{{\...
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What's the furthest object observable by the naked eye from earth?
From XKCD:
Caption: 'The light from those millions of stars you see is probably many thousands of years old' is a rare example of laypeople substantially OVERestimating astronomical numbers.
So, ...
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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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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 ...
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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 ...
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Did Gaia actually generate complete light curves for 212 Cepheids in other galaxies?
The recent BBC news item Gaia clocks speedy cosmic expansion says that a recent Gaia measurement of 212 Cepheid variables in other galaxies within the local group yields a Hubble constant of ~73 km/s/...
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Was the Earth-Sun distance ever calculated based on the time difference between night and day?
If we define sunrise and sunset as the time when the center of the Sun goes over the horizon then day time is a little bit shorter than night time because from a single point one cannot see a complete ...
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How can we be sure that we have identified very distant stars correctly?
From reading this question on calculating distance to stars and from a bit of background reading on the standard candle theory I still don't see how we can confirm that a star we see at one distance ...
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Comoving distance between two points [(RA1, Dec1, z1) and (RA2, Dec2, z2)]
I have Redshift (z), RA and Dec positions for two points in a galaxy catalogue (say P1 = [<...
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Why is Proxima Centauri called Proxima Centauri?
It seems very logical, to call the star, closest to earth, "Proxima" ("Proximus" is Latin for "close" and the word for star, "stella", is feminin, hence "Proxima"), but there's one thing I don't ...
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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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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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How do we measure distance in space?
I know that you can calculate the distance to another star for example, by using the phenomenon redshift to determine how much it has redshifted because of the expansion of the universe. But how do ...
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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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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 calculate the lookback time distance to a given galaxy?
By lookback time distance I mean the same as light-travel distance.
Can it be calculated from just knowing the redshift?
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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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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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Calculating distance of comet C/2019 Y4 (ATLAS)
SO, I decided I would take some pictures of the comet C/2019 Y4 last night. Afterwards, I thought I would try and do a rough estimation of distance based on my observations. I don't have any fancy ...
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Distance between stars Epsilon Eridani and Tau Ceti?
I am working on a story. It would be helpful if someone could provide the distance in light years between star Epsilon Eridani and star Tau Ceti.
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Are there good animations of the movement of proximate stars over long time periods?
After reading about Barnard's Star and how it's approaching us 140 km/sec, I'm curious if there are any visualizations of how the nearest stars to Sol will be moving over the next 100k years or so.
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How do astronomers measure the size of celestial objects?
What techniques and tools are available to astronomers in order to measure the size of celestial objects, such as stars or perhaps black holes that don't emit light or reflect starlight?
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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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Why is there "modulus" word in the "distance modulus" term?
The difference of apparent (m) and absolute (M) magnitudes of an object is called "distance modulus", which is related to the distance $d$ to the object in parsecs with equation
$$m - M = 5 \log \Big(...
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Observed lunar distance data?
Where can I find free/open data for the observed (not calculated/theoretical) distance between the Earth & Moon?
I want to see the observed distance of the Moon, hour by hour.
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Sun as our Supergiant
Let's talk about the time when our sun becomes a supergiant. We know that our solar system may get destroyed or it may get affected due the large mass of the supergiant and also due to the large ...
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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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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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Could you use luminosity changes over time to calculate distance?
More specifically: if you know your movement relative to a body, could you use the inverse square law to calculate distance? Since if you are distance $D$ away and you move $d$, $\Delta L \propto (D-d)...
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How was Cassini able to measure and use the Earth-Mars distance to get the Earth-Sun distance?
How was Cassini able to measure and use he distance between Earth and Mars to get the Earth-Sun distance? How were the ratios of Earth-Mars and Earth-Sun calculated then? Given Kepler's laws all we ...