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Author
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Topic: Rare Star Eclipse - Friday Morning, January 26th
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Mark J. Marshall
Film God
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Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002
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posted 01-17-2007 12:30 PM
This is interesting. I never even knew that anyone had such an understanding of asteroid paths that they could predict something like this with such precision. I'm kind of impressed actually.
According to this site, the star 32 Lyncis will wink out for a period of up to 14 seconds when the asteroid Palma passes in front of it. This will only be visible to a small band that spans across the US' mid section. They have a power point map that shows the areas that can expect to see the eclipse. Unfortunately, 1) I'm a little bit too far north, 2) I have way too many lights in my area, and 3) my telescope isn't that good. So I won't be able to see this.
Anyway, if there are any star gazers out there, I thought I'd pass this on. I'd be interested to know if you're able to see it.
quote: Rare Eclipse of the star 32 Lyncis by the asteroid (372) Palma, Friday Morning, Jan. 26, 2007
Updated: 2007 January 17 UT, 4h UT
The path prediction was updated on Jan. 12 by Steve Preston, moving the path 9 km farther south (from the Dec. 30th update). I've updated the overall USA map here and in the Power Point file, but will update the other more detailed maps in a day or two. I've added some full-sky finder charts and text information to help novice observers locate the target star.
This is the best eclipse of a star by an asteroid in the U.S.A. in many years, possibly since September 1983, when 40 observers from Alabama to southeastern Virginia timed the eclipse of a slightly brighter star by the asteroid (51) Nemausa. The star, at "magnitude" 6.3, is just barely visible to the naked eye for those in a dark location with good eyesight, but can be easily seen by anyone able to find it with binoculars. This rare eclipse will be visible from a wide path that extends across the U.S.A. from the Delmarva Peninsula (where it will occur at 4:44 am Eastern Standard Time, or EST) to northern California, where it will occur 3 minutes later, at 1:47 pm Pacific Standard Time (PST). Astronomers call such an event an "occultation" (from the Latin for the act of hiding) and that is the term that will usually be used below.
For those near the center of the path of visibility of the occultation, the event will last almost 15 seconds, and possibly even a little longer if the asteroid is not circular and its long dimension is aligned near the direction of motion. In binoculars, the star will just abruptly vanish from sight when Palma reaches it, and just as suddenly reappear several seconds later. Those with moderate-sized telescopes will be able to see the asteroid, which at 10th "magnitude" will be about 50 times fainter than the star. If the star is a previously-unknown very close double star (we have no information indicating that it is, but these observations can resolve double stars that even the most powerful telescopes can't see directly), it could disappear and reappear in quick steps, or a companion star might not be eclipsed by the asteroid and remain visible during the event. Also, dozens of asteroids are now known to have satellites, but Palma is not one of them. However, a small moon of Palma might not be found by other techniques, but could occult the star (see a section about this below) as seen from anywhere in the U.S.A. except Alaska (around 11:52 pm Hawaiian Standard Time Thursday evening, Jan. 25, in Hawaii).
OBSERVING THE OCCULTATION
Anyone with a pair of binoculars, or small telescope, within or near the predicted path is encouraged to try to observe the occultation, and to try to time its duration if an occultation occurs. The detail of the asteroid that we can obtain is proportional to the number of separate locations from which the occultation can be observed. Since 32 Lyncis will be above the horizon most of the night, you can practice finding it Thursday evening, Jan. 25, before you go to bed. Since you only need to watch the star for 2 or 3 minutes, you should be able to lose less than half an hour's sleep to make the observation from your home. Simple methods for timing the occultation are described in this Word file, written for observers in the Washington, DC region, but most of the basic timing methods can be used by observers throughout the USA.
THE PATH ACROSS THE USA
The path of the occultation across the USA is shown between the two parallel solid lines on the first slide of this Power Point file. The location of the path is not perfectly known; it could shift a little north or south of the area shown. There is a 16% chance that the northern edge of the path could be as far north as the dashed line just north of the northern solid line, and a similar chance that the southern edge could be as far south as the dashed line just south of the southern solid line. The first slide is from Steve Preston's Web site; slides two to five show the path in more detail relative to major highways and cities on 4 separate maps roughly corresponding to the path across the four continental USA time zones; and the sixth slide shows the northern limit in detail over the Washington, DC region. The last 5 slides were created from Derek Breit's interactive path map Web page that uses Google maps. Maps like the one for the Washington, DC region can be created from Derek Breit's Web site. These maps use the path updated by Steve Preston on Dec. 30, but as noted above, he updated the path with some more recent observations on Jan. 12, and that moved the path 9 km farther south. The maps will be updated in a few days to use the Jan. 12th path.
On the 4 maps below, showing the occultation path across the USA along with major highways and cities, the green line is the central line (100% chance for an occultation); the blue lines are the predicted limits (northern and southern limits; 50% chance for an occultation); the red lines are the 1-sigma limits (16% chance for an occultation); and the gray lines are the 2-sigma limits (2% chance for an occultation). These are also in the Power Point file mentioned above.
Eastern Time Zone, Delmarva to Ohio Central Time Zone, Indiana to Kansas Mountain Time Zone, Colorado to Utah Pacific Time Zone, Utah to California
On the map below, the blue line is the predicted northern limit (50% chance for an occultation); the red line is the 1-sigma northern limit (northern limit in case of a 1-sigma path shift to the north, 16% chance for an occultation); and the gray line is the northern limit in case of a 1-sigma path shift to the south, with an 83% chance for an occultation).
Washington, DC/n. VA region
SATELLITES OF (372) PALMA?
Over 100 asteroids are now known to have satellites, but Palma is not one of them. However, observers throughout the USA have a chance to see an occultation by a possible small satellite of Palma, so even observers far from the predicted path are encouraged to watch for a possible event. In November, observers in Japan managed to time an occultation of a 9th-mag. star by the asteroid (22) Kalliope as well as by its satellite Linus from several stations; details are here. So if you can watch 32 Lyncis for about a 5- minute period centered on its time of closest approach for your location, you might see the star blink out briefly by a satellite of Palma.
SKY CHARTS FOR LOCATING 32 LYNCIS
I've created some full-sky charts to help novice observers find the target star. There are charts made for six locations; pick the location nearest to yours. These are "bare" charts, that have only Jupiter (for those in the East), Saturn, and the target star labelled. I've annotated the charts for Richmond, VA, and for Redding, CA, with one that shows the area of the 3 detailed charts described below; one that shows only the third one that I recommend to be the main one to use; and then one that labels the major constellations to find the target star, nearly all of the first- magnitude (the brightest) stars, and the fainter stars needed to find the target star. The target star is not too difficult to find with binoculars once you've located the pair of stars iota and kappa Ursae Majoris (labelled "D" on the charts), which are about halfway between the bowl of the Big Dipper, and Castor and Pollux, the bright pair of stars parallel to the horizon that are prominent in the western sky at the time of the event. In the labelled chart, I show how to star-hop from the bowl of the Big Dipper to 3rd- magnitude stars southeast of the bowl; if you are not too close to a bright street light, you should be able to see these without binoculars (that is, with naked eye, or glasses or contact lens, if you need those for distance vision). Once you have found the "D" pair, you can then use the #3 detailed chart described below to find the target star with binoculars or the finder scope of a telescope.
Full-sky charts with 32 Lyncis circled and the local time of the occultation given; otherwise, they are unlabelled and do not show the areas of the detailed charts:
Richmond, VA, 4:44 am EST Indianapolis, IN, 4:44 am EST Omaha, NE, 3:45 am CST Cheyenne, WY, 2:46 am MST Salt Lake City, UT, 2:46 am MST Redding, CA, 1:47 am PST
For labelling, and for versions that show the area of the detailed charts, consult the charts in the Power Point file for the location closest to you below:
Richmond, VA annotated charts in Power Point file Redding, CA annotated charts in Power Point file
Detailed sky charts showing stars to 9th magnitude, the view that can be seen from a dark location with a good pair of binoculars or a good finder scope on a telescope, are in this Power Point file. These charts were adopted from the Herald-Bobroff Astro Atlas. In the Power Point file, there are 3 charts, with the 3rd (northern) chart copied in the 4th "slide" of the file, and annotations added showing how I recommend finding the target star from the "D" pair (iota & kappa Ursae Majoris). These charts just have north at the top; they are not oriented the way you will see the pattern of stars in the sky. So you should turn the charts to help match the view in the sky; the annotated full-sky charts will help show you how to turn the detailed chart. Also, once you find Talitha and the slightly fainter star of the pair, kappa Ursae Majoris (also marked "D" on the 4th slide), you can use their orientation as seen in your binoculars or finder scope to match the chart. Then follow the arrows on that chart, moving south to find first a small triangle of stars, then the star marked "35". Then continue south but jogging to the left to find relatively bright 10 Ursae Majoris (marked "E"), and then on to "G" (SAO 61254). Then move west (right) at a right angle from the "E" to "G" line, using the pattern of stars to reach the diagonal line of a few stars marked "H". Then just continue in that direction to the pair of stars marked 32 and 33. These are 32 and 33 Lyncis; 33 is the slightly brighter star that is closer to "H". The other, slightly fainter, star is the one you should watch, 32 Lyncis, the one that may be occulted by the asteroid Palma, or by a satellite of Palma, depending on where you observe.
More detailed information about this occultation an be found at Steve Preston's Web site. I have put the USA path map, and the finder charts of different scales, from Steve Preston's Web site in this Power Point file, which may be easier to view and print for some.
REPORTING OBSERVATIONS
For reporting observations, even if the star is monitored and no occultation is seen, you should use the new report forms that you can get here and click on "Templates for Report Forms". Completed reports should be sent to reports@asteroidoccultation.com and copied to Jan Manek at jan.manek@worldonline.cz .
Good luck with your observations!
David Dunham, 2007 Jan. 17, 4h UT home dunham@starpower.net 301-474-4722 cell 301-526-5590 office david.dunham@jhuapl.edu 240-228-5609
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