Questions tagged [parallax]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0 votes
1 answer
92 views

Is this how we get the stellar parallax angle?

I know this question has been asked before, but for me, something is missing in the answers. I think I might have it figured out though. So the parallax is usually explained with an illustration ...
  • 93
0 votes
1 answer
173 views

What is the formula to calculate the parallax angle?

The images were rendered in Blender. The two images were rendered 20 meters apart, side by side. The focal length is 50 mm if that matters. What is the formula to calculate the parallax angle θ as ...
  • 11
0 votes
2 answers
186 views

How does a proper motion displacement of $x$ arcseconds/year mean a star is moving at $x$ AU/year?

I trying to understand the author's answer to this question: I don't understand the part underlined red. How does 3.6pc mean 3.6AU? It says a "distance of 3.6AU", but doesn't say what is ...
1 vote
0 answers
37 views

How to evaluate the parallax error in the measure of diffraction rings' diameter?

I have to estimate with an image analysis the diameter of the rings generated by the diffraction of an electron beam with a polycrystalline graphite target. The pattern is made visible by a ...
0 votes
0 answers
38 views

Parallax and redshift - has anyone used Gaia data to match objects with redshift data?

Given the recent Gaia parallax data out to large distances, has anyone used that data to match objects with observed redshift data? I have taken as much Gaia object data as I can and compared it with ...
  • 1
0 votes
1 answer
62 views

Is the parallax of NEOWISE primarily caused by the earth's or the comet's motion?

The Comet C/2020 F3 (also known as "NEOWISE") appears to move compared to stars in the background: (Screenshots from Stellarium) Those images are one hour apart as seen from Germany. Is ...
  • 3,577
0 votes
2 answers
2k views

How do scientists calculate the orbital period of a planet?

It is known that you can calculate the distance to a planet using parallax, but how do scientists calculate the orbital period of a planet? (Assuming they don't know the distance and can't use Kepler'...
0 votes
1 answer
48 views

Hologram Questions

How does a hologram create parallax, compared to a photograph? If a hologram's purpose is to reproduce the light field, what part of that field creates parallax (angle, magnitude or position)?
  • 1
4 votes
1 answer
389 views

Parallax angle calculation

I'm trying to understand how the parallax angle is calculated. I alredy read this explanation. So we got that distance between the sun and the star is d = tan(α) * 1 AU. That said my doubt is about ...
  • 161
19 votes
7 answers
6k views

What is a simple argument to prove that the stars in the sky are further away from the Earth than the Moon?

How do we know, without using modern equipment, that the stars are further away than the moon in the night sky? Further, is there a simple and actionable argument to prove that this is indeed the case?...
  • 2,324
-1 votes
3 answers
317 views

Would a parallax measurement of distance to a star be affected by relativistic length contraction?

Let's say you had 2 ships launched 1 light year apart towards a star 10 ly away and they were equidistant from the star moving at .6c towards it. Would their velocity cause their parallax distance ...
  • 422
2 votes
3 answers
782 views

How to find transverse component of star's velocity given its proper motion and distance from observation point?

If $\mu$ is the proper motion of a star in arcseconds per year, and $d$ is the star’s distance from us, then the transverse speed, $v_t$ will be $$v_t=d\sin\mu$$ For small motions (assumed for ...
  • 2,251
2 votes
4 answers
940 views

Why do we have to wait half a year to measure stellar parallax

To measure distance of astronomical objects, often we may use parallax, the angle it makes with the earth-sun and trigonometry to determine the distance. The thing I don't get is why do we need to ...
  • 2,206
1 vote
1 answer
72 views

How accurately can the distance of a star be measured?

With the launch of the GAIA mission some years ago, a new precedent was set in mankind's ability to map our universe. However, how accurate are the distances created by this? From ESA's website, I ...
  • 113
1 vote
2 answers
158 views

What is the simplest way to find the distance of stars?

Once, I was staring at the sky and wanted to know the distance to stars I could see. I searched the Internet but didn't find any easy to use tools. The distance to stars can be measured using ...
1 vote
1 answer
839 views

Parallax versus Redshift when measuring astronomical distances?

From my understanding, the most common method for calculating how far away stars and galaxies are relative to us is by accounting for their redshift. I feel that this method could be inaccurate, ...
1 vote
1 answer
620 views

How to use parallax and Cepheids together to measure distances?

I can't quite grasp the simple version of how the Cepheid method uses the parallax method to measure the distance to distant galaxies. What I know is that Cepheids exhibit a period vs luminosity ...
14 votes
2 answers
13k views

How is the parallax angle actually measured?

I understand that parallax is used to measure distances to stars. But how is the parallax angle actually measured? In the parallax diagram we have two similar triangles, but we don't know any values ...
  • 375
0 votes
1 answer
367 views

Parallax calculation

I am asked to find the parallax of a star "Spica" as observed at $30.1$ $AU$ from the Sun. I want to use the small-angle formula: $\alpha=\frac{206265*D}{d}$ where $D$ is the baseline, $d$ the ...
  • 123
5 votes
2 answers
3k views

Why do some stars have a negative parallax?

I am constructing a Hertzsprung-Russell diagram for stars within some radius around Pleiades and have repeatedly come across stars that have negative parallaxes. For example, http://vizier.u-strasbg....
  • 746
4 votes
3 answers
830 views

How to account for the movement of stars during measurement of parallax?

In my GCSE physics class today I was doing revision for my upcoming GCSEs, and we came to parallax measurements, as before my teacher explained that two measurements are taken six months apart as the ...
3 votes
0 answers
109 views

3D movie optics mathematics

I get the idea that we use two polarized light sources and a parallax rendered film such that the objects seem to resemble true parallax in our eyes once it passes through the polarized glasses, but I'...
  • 1,921
0 votes
1 answer
546 views

Describe a path that a star moves around the sky [closed]

Suppose a star in the ecliptic plane has a parallax of p = 0.5 arcsec and a proper motion perpendicular to the ecliptic plane of µ = 1.0 arcsec/year. I need to describe the path that the star ...
  • 143
2 votes
2 answers
1k views

How are the distances and diameters of stars measured experimentally?

How is the distance of a star and its diameter measured using Earth-based tools? Normally we can measure the angle between the stars edge. But diameter or distance are needed to measure the other ...
  • 684
3 votes
1 answer
167 views

Measuring parallaxes from the moon

If one were to measure star parallaxes from the moon, what (if any) changes would you have to make compared to someone making the calculation from earth? What about on another planet in our solar ...
0 votes
2 answers
182 views

Quick question on astronomical units

I'm trying to solve for $\frac{M*}{M_0}$ and $p''$ using these two equations: Here is the lecturer's working, I worked it out several times and I got a different answer! Surely when you use Kepler's ...
  • 893
0 votes
1 answer
693 views

Quick question on parallax and parsec

I know that 1 parsec (pc) is the distance of star at which 1 AU subtends 1 arcsecond. so $1 pc = \frac{1 AU}{1"}$ Now, if two stars in a binary with a separation of 3" and have a trigonometric ...
  • 893
2 votes
2 answers
572 views

How to calculate error of parallax and sextant based navigation?

First of all, why wasn't the sextant ever used for land navigation? The horizon is easier to see at sea, but land based sextants could be used in conjunction with artificial horizons (as at sea when ...
  • 1,437
8 votes
3 answers
1k views

Parallax, obliquity, precession, and Orion?

Today, the obliquity of the earth is about 23.4°. 6500 years ago, it was about 24.1° Imagine the blue square is the constellation of Orion, and the yellow star is the sun. Viewpoint B is you, on ...
  • 81
0 votes
1 answer
223 views

Other than the motion of the Earth, what else would cause parallax?

Wikipedia has this to say about the discovery of the aberration of light: In 1728, while unsuccessfully attempting to measure the parallax of Eltanin, James Bradley discovered the aberration of ...
  • 4,498
6 votes
5 answers
1k views

Why don't the relative positions of stars and other objects in a galaxy change over the year?

Though the identifiable stars in a constellation (say Andromeda) and a galaxy (say the Andromeda galaxy) are situated light years apart, why doesn't the galaxy appear at different positions with ...
  • 61
8 votes
1 answer
3k views

When and how were relative distances to the planets first measured?

I understand that the absolute distance to a planet can be measured using earth-baseline (e.g., diurnal) parallax, and that the first reasonably accurate such measurement was made for Mars by Cassini (...
  • 4,920