Skywatch August 2017

Skywatch August 2017

For much of the United States, the biggest astronomy story for 2017 is the total eclipse of the sun that occurs over much of the continental US on Monday August 21, 2017. From the Hawaiian Islands, this eclipse will be visible as a partial solar eclipse at dawn on August 21; viewers in Hawai‘i 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.

 

Total Solar Eclipse over much of the continental US, August 21 2017

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 phrase, 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 disc of the moon. A total eclipse of the sun is a rare event for any given spot on earth; on average, a given location gets a total eclipse of the sun once every 360 years.

The August 21 total eclipse is being called “The Great American Eclipse,” as the path of the total eclipse 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. Cities along the path of totality include Salem, Oregon; Nashville Tennessee; and both Columbia and Charleston, South Carolina. In Salem, Oregon, to give one example, the total phrase of the eclipse runs from 10:17 to 10:19 a.m. on August 21 Pacific Daylight Time (it will be total there for 1 minute and 53 seconds). In Nashville, 1:27 to 1:29 p.m. Central Daylight Time; and in Charleston, the total phrase runs from 2:46 to 2:49 p.m. Eastern Daylight time, for a total of 1 minute and 39 seconds of totality.

The last total solar eclipse visible in the continental United States occurred in 1979 and the next one will not take place until 2024.

Those parts of the continental US not it total path will instead have a partial eclipse during this event; as will we, in the Hawaiian Islands.

 

August 21 eclipse in the Hawaiian Islands

In the Hawaiian Islands, we will not see a total solar eclipse; in fact we’ll have to wait till 2106 for a total solar eclipse over our islands!  We will, however, have a partial solar eclipse right at dawn.

The sun will rise in Honolulu at 6:20 a.m. on the morning of Monday August 21 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 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 at 7:25 Hawaii Standard Time on August 21 in the islands, it will be getting underway on the North American continent as the shadow of the moon races across our planet. 7:25 a.m. HST is 12:25 p.m. Central Daylight Time in Nashville, for example, and at that time the partial eclipse will be underway in Nashville; the eclipse in Nashville goes total at 1:27 p.m. CDT on August 21, which is 8:27 a.m. Hawaii Time if you wish to watch it here in the islands on a webcast.

Please note that it is never safe to view a partial solar eclipse directly; the only kind of solar eclipse you can view directly as the few moments of a total solar eclipse, and again we won’t see that in the islands. Your best get: purchase inexpensive safe viewing glasses carried by Bishop Museum’s Shop Pacifica. It is also essential this time around to have a clear view of the west, since the eclipse will occur when the sun is low in the morning sky.

Due to the fact that it’s very dicey that we’ll even be able to see the sun from our Bishop Museum campus as it rises over the hills of Kalihi that morning, Bishop Museum will NOT be doing an eclipse event early on August 21. However, this is a good ‘do it yourself’ event; just purchase our solar viewers and find a flat horizon, such as at a beach, with a good eastern view.

 

Other sky events for August

Perseid Meteor Show, early hours of August 11 and August 12

This is the most well-known annual shooting start shower. Its peak will occur in the morning on August 11, from 12:01 am till dawn; and again early in the morning of August 12, 12:01 a.m. till dawn.

The Perseids is one of the more consistent meteor showers, with up to 80 shooting stars per 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

Jupiter remains the brightest dot in the evening sky for August 2017.  Look for it about halfway up in the west at dusk in early August; it shines at just under minus 2 magnitude and sets by 11 p.m. By the end of August, Jupiter is only about twenty 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

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 at 0 magnitude. This makes Saturn about 2.5 times brighter than the star Antares in the Scorpion, that first-magnitude star to the right of Saturn.

 

Venus

In early August, Venus rises in the east right around 3 a.m. as is about 1/3 of the way up in the east at daybreak. Venus shines at minus 4 magnitude, many times brighter than even Jupiter. By the end of the month, Venus-rise occurs at 4 a.m. and the planet is only about 1/4th of the way of in the east at daybreak. Venus will remain in this role as a predawn beacon all the way till the end of October 2017.

 

Mercury

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, very low in the west, at 8 p.m. and sets by 8:20 p.m.  After about the 4th of the month, we’ve lost it for the rest of August.

 

Mars

 Mars is not visible at all in August.

 

Partial Lunar Eclipse (not visible in the Hawaiian Islands)

There is always some sort of lunar eclipse either two weeks before, or two weeks after, a solar eclipse.  Two weeks before the August 21 “Great American Solar Eclipse,” on August 7, a partial lunar eclipse will be visible from much of our planet, although not from the Hawaiian Islands. A partial lunar eclipse occurs when the moon passes through the earth’s partial shadow, or penumbra, and only a portion of it passes through the darkest shadow, or umbra. During this type of eclipse a part of the moon will darken as it moves through the earth’s shadow.

The eclipse will be visible throughout most of eastern Africa, central Asia, the Indian Ocean, and Australia.

For the August 7 eclipse, only a small portion of the moon will go into the deep inner shadow of the earth; viewers will see only a small ‘bite’ taken out of the moon at the peak of the eclipse, as about 20 per cent of the moon will go into the umbra.

We will just miss this lunar eclipse in the Hawaiian Islands. The full moon sets in Hawaii at 5:55 a.m. that morning of August 7, right as the penumbral phrase is beginning. (The penumbral phase, as the moon starts to enter the faint outer shadow of the earth, is not visible to the naked eye anyway, even were the moon not setting as the phase begins).  By the time the partial phrase (the time when a lunar eclipse becomes visible) begins at 7:25 a.m. Hawai‘i time, the moon will be well below the horizon in Hawai‘i.

The peak of the lunar eclipse occurs at 18:20 Universal Time on August 7; this is 8:20 a.m. on August 7 Hawaii Time, though again we will not see it since the moon will have already set more than two hours earlier.

In Mumbai, India, as an example, the peak of the lunar eclipse will occur around midnight local time on the evening leading from August 7 to august 8. Again, about 20 per cent of the moon will be in the earth’s shadow at the peak, making the moon look like a cookie with a bite taken out.

Star map constellations

Keah Watkins | Bishop Museum

Moon phases (Hawaiian Time zone):

First Quarter: July 30
Full: August 7
Third Quarter: August 15
New: August 21
First Quarter: August 29

2017-08-18T11:27:44+00:00 Monthly Astronomy Article|