![]() The instrument requirements are summarized here. Image collection over several hours reduces the measurement noise.Īmateur telescopes, cameras, and mounts are perfectly suited to capture the images needed for this project. Earth’s Western Hemisphere is perfectly placed to view SAO 93016 as Jupiter makes its closest approach. Jupiter shines high near the meridian in much of the U.S., but southern sites with good seeing will provide better measurements. The view from Jupiter in Figure 2 shows Earth at the time shown in Figure 1. The slow motion of Jupiter with respect to the stars allows several hours to acquire images. SAO 93015 (magnitude 7.6) and SAO 93020 (magnitude 8.3) provide good references to calibrate the plate scale. This close conjunction last occurred in 1928 and does not repeat until 2106, so this opportunity needs to be measured! SAO 93016 (magnitude 7.1) should show a 0.0085″ gravitational deflection as Jupiter passes nearby in October 2023. Jupiter’s gravity should generate an apparent outward deflection of 0.0085″. The closest approach of SAO 93016 is at 7:15 UT (3:15 EDT 00:15 PDT), when it will be only 25″ from Jupiter’s limb. Figure 1 shows the target star and the two reference stars near Jupiter. Because every instrument slowly changes with temperature, the best possible reference stars would be in a line, minimizing changes in the relative plate scale.īy coincidence, such a conjunction does appear the night of October 27–28, 2023. It is also essential that the target star be accompanied by two bright reference stars so that an accurate plate scale can be calculated. The Jovian passage takes several hours, so timing is not critical and the measurement noise can be reduced by analyzing thousands of images. One convenience of using Jupiter to measure stellar deflections is that an observer can use a telescope almost anywhere in the world, as long as a bright star passes within 100″ of Jupiter while at high elevation in a clear sky. While the Gaia analysis included Jovian deflections in calculating the positions of stars for its catalog (reference 8), a direct optical measurement has never been completed. The Hubble Space Telescope attempted to measure the deflection of a star near Jupiter in 1995, but no results were obtained (reference 7). Deflections there would be about 100 times smaller than those near the Sun, so technology was not good enough during his lifetime. Einstein also suggested that these measurements could be done during the daytime without an eclipse, but that has proven unsuccessful (references 4, 5, 6).Įinstein’s third suggestion was to use Jupiter as the gravitational source. Those events are not very common or convenient, and the observations had to be completed during the few minutes of totality. Einstein suggested this in 1916, but astronomers were understandably frustrated because observing during a total eclipse was necessary. Stellar deflections due to General Relativity have been measured near the Sun since 1919, where the deflection coefficient is 1.75″ for stars located near its limb (see references 1, 2, and 3 listed at the end). If successful, this measurement will fulfill one of Einstein’s wishes. Interested astronomers are invited to contribute data to this project. A test in November 2021 demonstrated the required precision. The data analysis will extract the star positions from thousands of images, followed by averaging the values in 30-minute intervals to reduce the measurement noise. The data collection will require continuously recording images over several hours over two nights. A fortuitous alignment of three bright stars with Jupiter in October 2023 should make this measurement possible using only small telescopes placed almost anywhere in the Western Hemisphere. Astronomers measured this at radio frequencies, but no one has accomplished this in the visible spectral region. General Relativity predicts that starlight will be deflected by 0.016″ if its light passes close to the planet’s limb. Get involved in a project that will measure the deflection of light due to Jupiter's gravitational effect.
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