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Breakthrough in Parallax Measurements and Galaxy Mapping
A real breakthrough in parallax measurement and therefore in determining distances of stars in our galaxy, the Milky Way, came with a mission called Hipparchos, after the ancient Greek astronomer that first used the method to estimate the distance of the moon.
This mission, launched by ESA in 1989, measured the positions and parallaxes as well as proper motions for nearly 120,000 stars. The spacecraft orbited Earth for about four years, allowing astronomers to probe the neighbourhood of the sun up to the distance of 300 light-years with the accuracy of 0.001 arcseconds.
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The Night Sky Isn't Two Dimensional
Parallax is the observed displacement of an object caused by the change of the observer's point of view. In astronomy, it is an irreplaceable tool for calculating distances of far away stars.
The night sky appears two-dimensional.
However, it took astronomer...
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The History of Parallax Measurements in Astronomy
The first known astronomical measurement using parallax didn't involve a star but the moon. The ancient Greek astronomer Hipparchus reportedly used observations of a solar eclipse from two different locations to calculate the distance of Earth's celestial companion.
In 1672, Italian astrono...
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Using Parallax for 3D Imaging
Another application of parallax is the reproduction and display of 3D images. The key is to capture 2D images of the subject from two slightly different angles, similar to the way human eyes do, and present them in such a w...
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2013: GAIA Telescope
In 2013, ESA launched a telescope called Gaia that charts the positions, parallaxes, and proper motions of more than one billion stars. That number represents only about 1% of the actual number of stars in the galaxy, but that's enough for astronomers to extrapolate the observations to u...
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Learning From The Parallax Effect
The light is spread over an area four times larger, and it will be only one-fourth as bright as when the projector was half as far away. If you move the projector three times farther away, the light will cover 9 square feet and appear only one-ninth as bright.
If a star measured in this ma...
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