2019 July 15
Explanation:
That's no sunspot.
It's the
International Space Station (ISS)
caught passing in front of the Sun.
Sunspots, individually, have a dark central
umbra, a lighter surrounding penumbra, and
no solar panels.
By contrast, the ISS is a complex and multi-spired mechanism,
one of the largest and most sophisticated machines ever created by
humanity.
Also, sunspots occur on the
Sun,
whereas the
ISS orbits the
Earth.
Transiting the Sun is not very unusual for the
ISS, which orbits the Earth about every 90 minutes,
but getting one's timing and equipment just right for a
great image is rare.
Strangely, besides that fake spot, in this recent two-image composite, the Sun
lacked any real sunspots.
The featured picture combines two images -- one capturing the space
station transiting the Sun -- and another taken consecutively capturing
details of the Sun's surface.
Sunspots have been
rare on the
Sun
since the dawn of the current
Solar Minimum,
a period of low solar activity.
For reasons not yet fully understood, the
number of sunspots occurring during both the previous and current solar minima have been
unusually low.