QUIET WITH A CHANCE OF FLARES: The sun remains relatively quiet for the third day in a row despite the presence of multiple large sunspot groups. NOAA forecasters say there is a 15% chance the calm will end with an M-class solar flare on Aug. 17th. Solar flare alerts: SMS Text
NEW COMET ALERT: A hyperbolic comet is falling into our solar system. Japanese amateur astronomer Hideo Nishimura discovered it just a few days ago in the constellation Gemini. Although it is relatively dim right now (magnitude +9), Comet Nishimura (C/2023 P1) could soon brighten more than 100-fold to become a naked-eye object in mid-September.
Above: A sky map with an inset photo of the comet from Dan Bartlett of June Lake, CA
A "hyperbolic comet" is a comet with too much energy to remain trapped inside the solar system. It will visit us only once, with the sun acting as a gravitational slingshot, sending the comet hurtling back into deep space after its flyby. Does that mean Comet Nishimura is an interstellar comet? Not necessarily. It might have come from the Oort Cloud. Indeed, that is more likely.
Because this is Comet Nishimura's first trip to the inner solar system, it is extra unpredictable. On Sept. 18th, the comet will make its closest approach to the sun deep inside the orbit of Mercury. Anything could happen when intense sunlight touches the comet's pristine surface for the first time. Possibilities range from dramatic brightening to a disappointing fizzle. Standard models suggest a peak brightness of 3rd magnitude. This would make it visible to the naked eye from rural areas.
Monitoring is encouraged. Comet Nishimura can be found in the pre-dawn sky using backyard telescopes larger than 6 inches. A date of particular interest is Aug. 25th when the comet lines up with Gemini's brightest stars, Castor and Pollux, making it particularly easy to find. Sky maps: Aug. 18, 19, 20, 21, 22, 23, 24, 25. Ephemeris: from JPL.
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THE WILSON EFFECT: The air in the French Alps was unusually steady on Aug. 15th when Thierry Legault pointed his telescope at the sun and captured a phenomenon rarely seen by amateur astronomers. It's called the "Wilson effect:"
"The sunspot's umbra is lower than the average solar surface, with surrounding penumbral filaments dipping down into it," says Legault. "The filaments are visible on the far edge of the 'bowl,' but not on the near edge, highlighting the depression."
Scottish astronomer Alexander Wilson discovered the effect in 1769 during Solar Cycle 2. In daily observations, he noticed that sunspots approaching the sun's limb were foreshortened and often appeared to be sunken or depressed in the middle. (The same observations proved that sunspots were features on the solar surface, not, say, dark satellites orbiting just above the sun.)
The Wilson effect has been debated for more than 250 years. Is it real? Some researchers in the 1950s argued that it was a purely psychological effect. Others retorted that observers couldn't be crazy; there was too much photographic evidence. Although the cause of the Wilson effect is still debated, many modern researchers take it at face value: Sunspots are shallow depressions. One idea holds that high pressure systems trapped in the magnetic canopies of sunspots press down on the underlying umbra, creating a dark bowl.
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FANTASTIC DRAGON SPACE PENDANT: Are you looking for a far-out gift? Consider the Fantastic Dragon Space Pendant. This one hitched a ride onboard an Earth to Sky Calculus cosmic ray research balloon, reaching an altitude of 117,524 ft:
You can have it for $124.95. The pendant is hand-crafted with colorful enamel inlaid on a hypoallergenic dragon exoskeleton. It makes a great gift for anyone who loves fantasy and dragonlore.
The students are selling space pendants to support their cosmic ray ballooning program. Each one comes with a greeting card showing the pendant in flight and telling the story of its trip to the stratosphere and back again.
Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education
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