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Skywatch for the week of August 24, 2020

Mon Aug 24, 2020        LONG MONTH, BLAME CAESAR

August used to be only thirty days long; now it’s 31. You can blame an old Roman emperor for this. Back in 46 BC, our calendar system got a major overhaul when Julius Caesar re-set the beginning of spring to March 25th (it had slid over into May). He also introduced the leap year, which gave an extra day to February every fourth year. Then the dictator was assassinated (probably no connection here,) and eventually his step-son Caesar Augustus took over. To honor dear old dad, Augustus changed the name of the 31-day month Quintillis, and it became July. Then Augustus decided that he ought to have a month named for himself too, and so he changed the next month, Sextillus, re-naming it August. But it had only 30 days, so the emperor tacked on another day to make it just as long as his father’s, and that’s why this month is so long, and that’s also why politicians should never be left in charge of calendars.


Tue Aug 25, 2020         NAME THAT MOON

The moons of our solar system have many shared features, such as meteor impact craters, mountains, plains and valleys. See if you can identify the moon if I list some of those named features. This first moon has impact craters named Plato, Kepler, Copernicus, Galileo, Aristotle and Hevelius, plus great dark features like the Sea of Cold, the Bay of Rainbows, the Ocean of Storms and the Sea of Tranquility. This is easy, it’s the moon, our moon. What about El Dorado, Aztlan, Xanadu and Shangri-La? These features are found on Saturn’s largest moon, Titan. This next moon has lots of volcanoes with names like Thor and Loki, Marduk, Maui and Pele. The moon is Io and it orbits Jupiter. And finally, try Kirk, Spock, Uhura, the plains of Vulcan, Nemo, Skywalker, Ripley, Vader crater, the Tardis chasm, and a dark feature at its north pole named Mordor? These are found on Pluto’s largest moon, Charon.


Wed Aug 26, 2020        STARING AT THE SUN – DON’T! 

The brightest object in the sky is the sun - so bright, in fact, that it's difficult to look anywhere near it because of its blinding brilliance. One rumor often heard is that the Italian astronomer Galileo went blind from viewing the sun through a telescope, but it’s not true: he used his telescope only to project the sun’s image onto a viewing surface, which is perfectly safe. Long before the invention of the telescope, ancient Greeks observed and described large sunspots, perhaps 40,000 miles across that sometimes appeared on its face. They did this by watching the sun only while it was rising or setting, and at its dimmest. As you may have guessed, this is definitely NOT a safe practice: even though the amount of visible light is cut down by the thick column of air at the earth's horizon, the sun is still emitting invisible radiation which can blind you. So never stare at the sun, even at the beginning or end of the day.


Thu Aug 27, 2020         CRASH GO THE COMETS!

On August 31st, 1979, a comet crashed into the sun. Well, crashed is probably not the right word. It’s hard to crash into anything if you’ve been vaporized long before impact. It turns out that a lot of comets have augered into the sun over the years. That’s because the sun’s huge gravity field is powerfully attractive! The comet actually had a name before it was destroyed: Comet Howard-Koomur-Michiels. Not exactly a household name, but that’s the beauty of comets: they’re named after the people who discover them, and that’s typically amateur astronomers who scan the heavens using telescopes with wide fields of view for searching large sections of the sky. Comet Howard-Koomur-Michiels was discovered independently by three amateur astronomers, so their names were attached to it. Of course, the comet no longer exists; as I’d mentioned it got toasted by the sun 39 years ago.


Fri Aug 28, 2020          THE CRAB NEBULA

On the night of August 28th in the year 1758, the Crab Nebula was discovered with a telescope. The nebula's discoverer, Charles Messier of France, thought at first that it was a comet, which when seen far out in space, resembles a small fuzzy splotch of light. But unlike comets, this fuzzy object didn't move against the starry background. Hour after hour, night after night, the thing refused to budge. Disappointed in his failure to find a new comet, Messier catalogued this object as Messier #1, or M-1, and from then on, whenever he saw it, he quickly moved on to more promising candidates. But when bigger and better telescopes were invented, other astronomers found that M-1, the Crab Nebula, is more impressive than any comet: it is the exploded remains of a star that went supernova. Tonight M-1 can be found, with a telescope, low in the east northeast, a little after 1 AM, behind the forward horn tip of Taurus the Bull.