posted 01-17-2007 12:30 PM                   

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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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posted 01-18-2007 01:32 PM                       

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Also in 2007, asteroid 372 Palma passes in front of the borderline naked-eye star 32 Lyncis on January 26th; see the February Sky & Telescope, page 64, for this event's visibility path, which extends clear across the US from coast to coast.

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