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 SkyandTelescope.com about how to view and record occultations."

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*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. 

The New Vesta: Dawn Spreads the Asteroid's Secrets

O beautiful Vesta! Vesta has become quite a spectacular asteroid, not only because of its beauty (as you can see in the image below), but becasue of everything Dawn has sent us so far. After Dawn reached asteroid 4 Vesta this past weekend, continual pictures and information has been sent to our planet. Vesta isn't just any old asteroid.

Isn't the protoplanet beautiful?! Dawn sure thinks so! Vesta is the second most massive object in the asteroid belt, with Ceres being the first, so it's a big deal to see such wonderful surface features on this asteroid. Ground-based telescopes have been trying to get a good picture of Vesta forever, but nothing was as good until Dawn arrived.

"We are beginning the study of arguably the oldest extant primordial surface in the solar system," said Dawn principal investigator Christopher Russell from the University of California, Los Angeles. "This region of space has been ignored for far too long. So far, the images received to date reveal a complex surface that seems to have preserved some of the earliest events in Vesta's history." No spacecraft has ever visited the asteroid belt before, so this is a first for the whole earth. NASA has accomplished much, but nothing this significant yet. It was the first space exploration group to launch a craft to visit the asteroid belt, which is very impressive.

Here, you can view Vesta's size relative to other major asteroid bodies in the asteroid belt. Click on the picture to make it larger; if you can't do that: 21 Lutetia is on top (very massive), two under that is 243 Ida and moon Dactyl, and under that is 433 Eros, just naming the famous, well-known asteroids.

As people are still in awe of Dawn's arrival after traveling over 1.7 billion miles for four years, you have to admit Dawn did make good time. Being the first spacecraft to ever make the largest propulsive acceleration of any spacecraft, Dawn made a change of velocity of more than 4.2 miles a second, on account of its high-tech ion-powered engines.

"Dawn slipped gently into orbit with the same grace it has displayed during its years of ion thrusting through interplanetary space," said Marc Rayman, Dawn chief engineer and mission manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It is fantastically exciting that we will begin providing humankind its first detailed views of one of the last unexplored worlds in the inner solar system."

Dawn will keep on approaching Vesta for about three weeks, looking for hypothetical moons, observing surface features and properties. NASA writes, "In addition, navigators will measure the strength of Vesta's gravitational tug on the spacecraft to compute the asteroid's mass with much greater accuracy than has been previously available. That will allow them to refine the time of orbit insertion."

Dawn will leave Vesta in July 2012, making its way to minor-planet 1 Ceres in February of 2015. More of Dawn is here, along with Dawn's 'journal.' More of Dawn at Astronomical Events Calender is Here.