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How to calculate the distance between the earth and Sirius by parallax method
The angle to be measured in this trigonometric distance measurement is not the angle from which we look at Sirius, but the angle between the two viewing directions
You also need to know the linear distance between the two points
In general, the annual parallax is used, that is, the two points with the largest distance are selected in orbit by using the earth's revolution
Specifically, on a certain day in winter and summer (opposite to the Yellow meridian), we can see the displacement angle of Sirius on the background
Stellar parallax and distance
There is parallax phenomenon when observing stars on the earth. At this time, the baseline is the diameter of the earth's orbit, and the parallax of the observed star is the internal angle P formed by the sun, the star and the earth. With the revolution of the earth, the star appears annual parallax motion as shown in the figure below. The closer the star is to us (d), the greater the parallax P, and vice versa
Because most of the stars are too far away, the parallax is very small. The parallax of the nearest star (Centaur nearby star) is only 0.75 arcsec, even less than 1 arcsec (1 / 3600 degrees). In addition to the atmospheric effect of ground observation, the error is very large. Therefore, the parallax method is only suitable for measuring the distance of stars within 300 light years
Second gap
Parsec is the unit of the distance between celestial bodies. It is composed of parallax and arc seconds. PC is the reciprocal 1 / P of annual parallax P. when the annual parallax of celestial bodies is 1 arcsec, the distance between them is 1 second. Since the length difference between the two sides corresponding to 1 arcsec can be ignored, this triangle can be thought of as a right triangle, One second gap = 206265a. U. = 3.26 light years
Let's deduce the calculation method. I've been thinking about it for a long time. I'm old
1. When p is small（
What is parallax, what is the cause of parallax and how to eliminate it?
Parallax is caused by the bending of light due to gravity. Observe the stars according to the different positions of the earth's revolution, and use the data obtained twice to determine the position of the stars (just to reduce the error)
What is parallax? What is the cause of parallax? How to eliminate parallax?
Due to the imperfect focusing of objective lens, the real image of the target does not completely coincide with the cross wire plane, resulting in relative movement, which is called parallax, Then focus the objective lens carefully until the image is stable and clear
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