Telescope users may want to take a look at Jupiter in the next couple weeks. The Great Red Spot (GRS) is more obvious now that it was a year ago, in part because its color has deepened as the South Equatorial Belt has faded. If your scope is 6 inches or larger and you crank your magnification beyond 150x, you’ll notice the Spot’s little companion, nicknamed Red Spot Jr., located due south of the main spot.
Propelled by powerful winds reaching 225 mph, the little spot, formally called Oval BA, has gone around the planet a couple times since it formed in the late ’90s through 2000 when three smaller ovals merged into one. Its progenitors were colorless, but as Oval BA continued to grow, it changed color from white to pink, mimicking the GRS’ hue. Apparently its swirling winds reached deep enough into Jupiter’s atmosphere to dredge up colorful compounds from below.
Ovals are storms in Jupiter’s atmosphere that take the shape of swirling vortices. The largest, the Great Red Spot, spans nearly three Earths and hasn’t let up since French astronomer Jean-Dominique Cassini first saw it in 1655. Its outer edge rotates in a counter-clockwise direction about once every 6 days.
Oval BA is almost directly south of the Red Spot — you could even say it’s in conjunction with it. When my friend Will and I first saw it through his telescope last weekend, he remarked the pair looked like a snowman with his fat torso on the bottom and little head on top. Like the Red Spot, Oval BA is pink but the color is very subtle and takes concentration to see well. Sometime this week or next , BA will slide past the GRS as it continues its merry way along Jupiter’s South Temperate Zone. Its last encounter with the red monster happened in 2006. Astronomers watched and waited to see if the bigger spot would either eat or tear apart junior. Thankfully Oval BA survived. Will we see this Earth-sized hurricane remain unscathed during this passage?
To help you find out the answer, here’s a list of times when the GRS and little junior will be squarely facing Earth, or in astronomy parlance, when they’re on the planet’s central meridian (CM). The best times for viewing are an hour on either side of CM passage. For times beyond the dates below, jump on over the Sky and Telescope’s handy Red Spot calculator.
Great Red Spot – times of best visibility (Central Daylight time)
* 11:03 p.m. tonight Aug. 20
* 4:50 a.m. Sunday
* 12:41 a.m. Monday
* 2:19 a.m. Wednesday
* 10:10 p.m. Thursday (Jupiter low in sky)
* 3:57 a.m. Friday morning and again at 11:48 p.m. Friday night