Comet 29P/Schwassmann-Wachmann 1

 

Are you a collector of comets? Are you keeping a list of all the comets you've looked at or taken pictures of with your telescope? If so, is Comet 29P/Schwassmann-Wachmann 1 on your list of comets that you've already seen? It should be! If not, make it so!

Comet 29P/Schwassmann-Wachmann 1 (which I will hereafter refer to as "Comet 29P" or just "29P") is not your ordinary comet. No, it's not interstellar, like Comet 3I/ATLAS. It's not inhabited by aliens. That's not what I mean by "not your ordinary comet."

No, what I mean is that, unlike other comets, 29P has a nearly circular orbit, out beyond the orbit of Jupiter. It constantly displays a coma, throughout its entire journey around the sun each year. Its average distance from the sun is 562,417,500 miles, and the difference between its furthest point (aphelion) and closest point (perihelion) is only 50.3 million miles. Both aphelion and perihelion are farther away from the sun than Jupiter.

And yet, somehow during Comet 29P's nearly circular orbit that is out beyond Jupiter, it still manages to undergo frequent outbursts. That means that if you want to check 29P off of your "comets seen" list, you need to pay attention to the news and capture your image or observation when it goes through one of these sudden outburst events. You can't simply wait for perihelion, like most comets, because 29P's outbursts don't always coincide with its closest approach to the sun. They can literally happen at any time.

In the orbital-view graphic above (from JPL's Small-Body Database Lookup website), you can see where the comet was with respect to both earth and sun when I took the image at the top of this page. The vertical lines (like fence posts) along its orbit indicate whether it is above or below the plane of the solar system. At the time I took its picture, Comet 29P was below the plane, meaning that it appeared lower in our skies, which was not advantageous. 

In other words, I did not necessarily take my picture during the time of an outburst. The media announced an outburst more than a month ago, on February 9th. My image, which is a stack of 15 x 15-second exposures with an 11-inch SCT at f/2 taken on March 22nd, more probably shows the view that you might expect to get on a normal night. 

The comet will reach its most southerly point (the least favorable time to look at it, unless it's in outburst) in our skies around August of 2028. On the other hand, should you choose to wait until we can see 29P at its highest point in our skies, you'll need a lot of patience! That won't happen again until December of 2035! 

Much better to pay attention to the news and check Comet 29P off your list when you hear about it going into outburst!

The last outburst of Comet 29P that I recorded was in October of 2021. Compare my image below with the one at the top of this page. Notice especially the difference in total exposure time. The one at the top of this page was 3-3/4 minutes long (15 x 15 seconds), whereas the one below was only about 2-1/4 minutes (6 x 22 seconds). Yet, even with its shorter overall exposure time, notice the brightness and size of the comet's nucleus below, compared to the picture at the top. I should also note that the picture below was not taken at perihelion, but rather about at its average distance to the sun.




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