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October 10, 2024

Comet Viewing – Catch it While You Can

S. M. Gollmer

Tsuchinshan-ATLAS (C/2023 A3) is a once in a lifetime comet, actually once in a million lifetimes.  It was discovered by the Purple Mountain Observatory in China over a year ago.  A rough estimate of its orbital period is 10 million years, and some predict it will leave the gravitational influence of the sun and never return.   It reached perihelion (closest approach to the sun) on September 27th, coming as close to the sun as the planet Mercury.  It is now speeding away from the sun and will make its closest approach to Earth on October 12th.

Between tonight and Saturday, Tsuchinshan-ATLAS can be viewed right after sunset near the western horizon.  It is currently as bright as the star Sirius but will quickly dim over the next week.  There is a trade-off as to the best viewing night.  While it is close to the sun, the twilight sky will wash out the brightness of the comet.  Each subsequent night the comet can be seen later after sunset providing more contrast.  At the same time, Tsuchinshan-ATLAS will approach the brightness of ordinary stars.  My expectation of best viewing, given clear skies, is October 12th when it can be seen up to an hour after sunset.

Make sure you take this opportunity to view Tsuchinshan-ATLAS.  Seeing the tail of the comet streaming away from the sun is a sight rarely seen.  The last time I had this experience was viewing comet Hale Bopp in 1995.  Binoculars and telescopes allow you to view this comet until the end of October, but now is the time to see it with your own eyes.

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