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For the United States, the biggest astronomy story for 2017 is the total eclipse of the sun that occurs over much of the continental U.S. on Aug. 21.
From the Hawaiian Islands, this will be visible as a partial solar eclipse at dawn on Aug. 21. Viewers in Hawaii with a clear eastern horizon and with a safe viewing filter will see a chunk of the sun blocked by the moon as the sun rises already in eclipse.
A total solar eclipse is generally considered the most awe-inspiring experience in astronomy. For the few moments when the sun’s blazing disk is completely blocked by the moon, the land grows dark, the air cools, and the brighter stars and planets emerge. During this total phase, and only then, it is possible to view the eclipse directly; the pale, beautiful corona of the sun, a million times dimmer than the sun itself and only visible during total solar eclipses, shines around the black disk of the moon.
A total eclipse of the sun is rare for any given spot on Earth; on average, a location gets a total solar eclipse once every 360 years.
The Aug. 21 total eclipse is being called “The Great American Eclipse,” as its path will pass over the continental United States from Oregon to South Carolina. The total eclipse will be visible in parts of Oregon, Idaho, Wyoming, Nebraska, Missouri, Kentucky, Tennessee, North Carolina and South Carolina before ending in the Atlantic Ocean.
The last total solar eclipse visible in the continental United States occurred in 1979, and the next one will not happen until 2024.
Those parts of the continental U.S. not in the total solar eclipse’s path will instead have a partial eclipse during this event, as will we in Hawaii. The islands will have to wait until 2106 for a view of a total solar eclipse.
On Aug. 21, the sun will rise in Honolulu at 6:20 a.m. in partial eclipse, with about one-third of the sun’s disk blocked by the moon. For the next hour, viewers using safe viewing devices (and who have a clear eastern horizon — the sun will still be low in the east, in this hour after dawn) will see the moon slowly uncover the sun.
By 7:25 a.m. in Honolulu the eclipse will be over.
As this eclipse ends in the islands, it will be getting underway on the North American continent as the shadow of the moon races across our planet.
Please note that it is never safe to view a partial solar eclipse directly; the only kind of solar eclipse you can view directly is the few moments of a total solar eclipse, and again we won’t see that in the islands. You can purchase inexpensive safe viewing glasses at Bishop Museum’s Shop Pacifica.
Perseid meteors
The Perseid meteor show is the most well-known annual shooting-star shower. Its peak this year will occur from 12:01 a.m. until dawn on both Aug. 11 and 12.
The Perseids is one of the more consistent meteor showers, with up to 80 shooting stars an hour under good circumstances. The Perseids often leave long trails. The shower is generated by debris from Comet 109 P Swift Tuttle. This comet takes 130 years to orbit the sun and passed through the Earth’s part of the solar system back in 1992, leaving lots of fresh comet debris that led to particularly good showers.
That said, we expect lots of lunar interference this year, since the moon (which will be between a full and a third-quarter moon during the peak days of the shower) will be in the sky and bright during peak viewing times.
August planets
Jupiter remains the brightest dot in the evening sky this August. Look for it about halfway up in the west at dusk in early August; it sets by 11 p.m. By the end of August, Jupiter is only about 20 degrees above the west horizon at dusk (the width of two palms) and sets by 9 p.m.
While it’s been with us all summer, the time of Jupiter is ending; by the end of September it will be lost in the light of the setting sun.
Saturn is about halfway up in the south as it gets dark in early August. The yellow-white planet is about one fist’s diameter to the left of Antares, the orange Mars-like star that is the brightest star in Scorpius. Saturn sets in the west at 2 a.m. in early August. By the end of the month, look for Saturn high in the southeast at dusk; it will set just before 12:30 a.m. While it’s nowhere near as bright as Jupiter, Saturn does shine nicely — about 2.5 times brighter than Antares.
In early August, Venus rises in the east right around 3 a.m. and is about a third of the way up in the east at daybreak. Venus shines many times brighter than even Jupiter. By the end of the month, Venus rises at 4 a.m. and the planet is only about a fourth of the way up in the east at daybreak. Venus will remain in this role as a predawn beacon until the end of October.
The elusive planet Mercury is visible for the first few days of August, but it will be hard to spot. It emerges from the dusk, low in the west, at 8 p.m. and sets by 8:20 p.m. After Aug. 4, we’ve lost it for the rest of the month.
Mike Shanahan is director of visitor experience and planetarium at Bishop Museum. Reach him at mikes@bishopmuseum.org.
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