Sunday, September 11, 2011

90 Antiope's Dual Asteroid Occultation - The Results

After occulting each other (and the star LQ Aquarii), 90 Antiope made a memorable day this past July 19. That dual-asteroid occultation was a treat for those on the Pacific coast, becasue these events are the events you don't see everyday. After waiting almost two months, we have finally got the report in from Sky & Telescope concerning what actually happened that commemorated day. Although asteroid occultations are not very impressive as grand-scale total solar and lunar eclipses, asteroid occultations "can be just as rewarding — and sometimes have far more scientific value," Kelly Beatty writes in his post, Antiope Occultation Yields Double Bonanza.

4 Days before occultation. Photo Credit giant Keck Telescope: W. Merline & others

Considering carefully the last remark, 'far more scientific value' (from the quote above), astronomers have realized the complexity and scientific values of this occultation. To describe this event in detail, from our earlier post entitled Rare Event: Dual Asteroid Occultation:
July 19, Tuesday, brings us a rare event of an occultation of dual (binary) asteroid 90 Antiope. Between the hours of 10:18 to 10:25 Universal Time, 90 Antiope will occult one its members, so us here in America can see it. If you're on the east coast - you're out of luck, as sad as it is. Only the northeast to southwest portions across central Saskatchewan, southeastern Alberta, western Idaho and Montana, northern Nevada, and north-central California will be able to witness this rare event.
Sky & Telescope points out three advances in why this occultation was so beneficial, despite the low magnitude of the binary pair and bright condition of the moon.*

1) Despite the fact that 90 Antiope is just at magnitude 8.27 together (9.02 each separate), the star occulted was rather bright (magnitude 6.7) and could be viewed easily by small, personal telescopes.
2) Visible, 90 Antiope is comprised of two bodies, each approximately 90 kilometers across, which when viewed in a stellar occultation, is very impressive. (90 kilometers = 55 miles).
3)The predicted track of occultation visibility crossed a well-populated region of the United States and portions of Canada.

"I'm happy to report that Antiope did not disappoint," Beatty writes. Fifty plus observers plotted their estimations concerning the occultation, as the plot below demonstrates. If you can note, the southern object has a rather well pronounced missing side, perhaps a crater, but astronomers are not entirely sure. Since 90 Antiope was discovered in 1888 by German astronomer Robert Luther, many observers have watched these objects in their celestial course; a myriad have noted that irregularity in perfect proportion.

Each multicolored line shows an approximate estimate on the path of occultation. Credit: IOTA, David Dunham

Concerning the actual occultation of LQ Aquarii, astronomer William Merline (leader of a team from the Southwest Research Institute; giant Keck Telescope in Hawaii) had predicted that each component of 90 Antiope would "clip" the edges of the star. Because of this, a 'partial' occultation is granted, but no-one expected that the gap would be that wide. "A few observers in the middle had no occultation by either component," explains David Dunham, IOTA's president. "We're debating whether to call these central miss observations 'Moses chords' or 'Hercules chords', for threading the Pillars of Hercules to gain new knowledge."

In a grandiose conclusion, this occultation has provide a significant amount of scientific information. Sky&Telescope ranks it to be "among the most remarkable and scientifically valuable in recent years." Although pure irony, in the era of the 1970s, when astronomical understanding was nothing compared to today**, astronomers argued that there was no such thing of dual asteroids (See our other article, under title 'The History...Binary-Asteroids'). David Dunham was one that actually supported this 'outlandish' idea, and he finally did succeed in his efforts. This was resolved due to the fact of Galileo and Ida & Dactyl (lower portion of article). Today more than 200 multiple asteroids are known. (I recommend that link immensely for study).

Ida and Dactyl, thanks to Galileo spacecraft.

Sky&Telescope: "You can click here to learn more about IOTA and here for predictions of upcoming occultations that you might be able to observe. And you'll find several articles right here on about how to view and record occultations."

*Sky&Telescope takes credit for the formation of the ideas, I take credit for the embellishment of them - and they are embellished.  
**This is a eloquent simile, yes, there was astronomical understanding in the 1970s, but becasue of today's astronomy knowledge and equipment, we know much more. 

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