All Questions
Tagged with distances observational-astronomy
30 questions
-1
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2
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93
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How can I calculate the distance between a star in the Hipparcos catalogue and the Earth?
I'm developing a VR application using the Hipparcos catalogue to get the right ascension and declination to show them.
I need to know the distance between all of these stars from the catalogue, and I'...
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3
votes
1
answer
510
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 ...
-1
votes
2
answers
221
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.
user50623
3
votes
1
answer
121
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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.
- 53
5
votes
2
answers
217
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 ...
- 557
3
votes
1
answer
211
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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 ...
- 133
7
votes
3
answers
1k
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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 ...
- 182
1
vote
1
answer
111
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 ...
- 5,585
7
votes
1
answer
328
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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 ...
- 578
2
votes
2
answers
754
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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 ...
- 191
2
votes
1
answer
769
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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 ...
- 437
0
votes
1
answer
102
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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 ...
- 11
11
votes
1
answer
2k
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How exactly was Giovanni Cassini able to measure the distance to Mars?
Recently learned that Cassini was able to calculate the distance to Mars quite well using parallax in 1672. I was surprised, since even at opposition of Mars, the parallax (with respect to the Earth's ...
- 1,707
13
votes
2
answers
884
views
Radius to which all hydrogen-burning stars are known?
For the purposes of this question, I wish to consider active, hydrogen-burning stars, not deuterium-burning brown dwarfs, or stellar remnants like black holes or neutron stars. (Though including ...
- 4,823
3
votes
1
answer
3k
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Comoving Volume Calculation
Suppose I have data from an astronomical survey at redshifts in the range $z = [2,3]$. Suppose that, on average in this range, the data covers an area on the sky of $A=1$ $\mathrm{Mpc}^2$. How would I ...
- 205
19
votes
4
answers
5k
views
What's the difference between minutes and arcminutes?
I read in trigonometry class that 1 minute is equal to 1/60 degrees. So, 'minute' is an angular unit. But also 'arcminutes' are used to measure seperation between celestial objects and also equals to ...
- 301
0
votes
1
answer
91
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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? ...
- 103
1
vote
1
answer
5k
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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 ...
- 11
3
votes
1
answer
86
views
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 ...
- 17.7k
5
votes
1
answer
1k
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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 ...
- 17.7k
3
votes
1
answer
107
views
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 ...
- 3,157
1
vote
1
answer
1k
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How Did Early Astronomers Measure Distances?
Prior to the era of radar and other forms of radio/RF/EM ranging, what approaches, methods, and techniques did early astronomers (e.g., Kepler, Cassini, Copernicus) use to measure the distance(s) from ...
user28134
6
votes
1
answer
1k
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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 ...
- 175
0
votes
1
answer
945
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Moving-Cluster method for determination of the distance of Hyades. A starter problem
I am currently following a class of observational astronomy lab. I will present a brief description of the method in first and then proceed to the question, so anyone is welcomed to read the entire ...
3
votes
2
answers
387
views
Why are distant objects observed in the near infrared?
I was reading an article that explains why JWST is a successor to Hubble and not a replacement for Hubble. They explained that Hubble's science pushed astronomers to look at longer wavelength. And ...
- 218
4
votes
4
answers
16k
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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?
- 559
4
votes
2
answers
3k
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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?
- 2,511
10
votes
2
answers
415
views
Present distances between planet. How can I find them?
It's "commonly known" how distant are our solar system planets from Sun. But we can't easily say that about planets, which distances can differ greatly, without some observations (or simulations, ...
- 203
8
votes
1
answer
1k
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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 ...
- 2,695
13
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2
answers
2k
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How does angular resolution of a telescope translate to its parallax precision?
We can often read in the scientific and also more casual reader literature and articles about the angular resolution of various telescopes and other optical equipment, be it ground based or onboard ...
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