Sky and Telescope - May 2018 - 51

Asteroid
Occultations

Count the Eta Aquariids?
Eta Aquariid Meteor Shower

IN THE EARLY MORNING hours of

90 minutes before dawn

Water Jug
of
AQUARIUS
Radiant

Great Square
of
PEGASUS

Circlet
of PISCES

Looking East

G REGG DINDER M A N / S&T

p From latitude 30º north about 90 minutes before sunset, the radiant for the Eta Aquariid meteor
shower rides low in the sky. For observers farther north, the radiant rises later, so is even lower
when the sky begins to lighten.

MOONLIGHT WILL AFFECT visual
observations of this year's Eta Aquariid
meteors. The shower is usually one
of the best of the year for the Southern Hemisphere. For viewers at more
northerly latitudes, the radiant is above
the horizon for just a few hours before
dawn. Subsequently, the shower often
produces long, fast meteors along the
eastern horizon as morning twilight
begins - that is, when the Moon
doesn't get in the way.
This year's peak is predicted to
fall on May 6th, which means that it
coincides with a waning gibbous Moon,
not ideal lighting conditions. Even so,
the International Meteor Organization (IMO) recommends that observers
get out and record this year's shower
activity. Research prompted by J. Hutch
Kinsman's and David Asher's inquiry
into meteor showers during the Maya
Classic period (see S&T: April 2018,
p. 36) indicates that there may be a
slight enhancement of activity on May

3rd due the gravitational inﬂuence of
Jupiter on the 164 BC trail of the parent object, Comet 1P/Halley. A similar
bump may occur on May 5th, thanks to
Jupiter's inﬂuence on Halley's AD 218
trail.
If you're interested in doing a scientiﬁc meteor count, you'll need to commit to at least one hour of observing
and follow a standardized method. This
involves determining the faintest stars
you can see with your naked eye from
your location, as well as recording your
latitude and longitude. Note the time,
and keep track of the times you looked
away from the sky. Ideally, you should
watch in a direction free of interference
by trees and artiﬁcal lights, and in a
direction away from the Moon.
Visit imo.net for more instructions
on how to report your count.

* FIND YOUR CLUB:

skyandtelescope.com/astronomyclubs-organizations.

May 11th, the asteroid 472 Roma will
occult a 10.8-magnitude star in Serpens
Caput. Observers along a path that
stretches from the West Coast to the
South Atlantic region will see the star's
brightness drop 2.4 magnitudes for up
to 4.2 seconds.
The International Occultation Timing Organization (IOTA) notes that
Roma was well observed during an
occultation on July 8, 2010, but because
the star occulted had an angular size of
about 1/3 that of the asteroid, it was difﬁcult to completely determine Roma's
size and shape.
For observers in Redding, California, the event should begin within a
minute or two of 8h 14m UT (1:14 a.m.
PDT). Observers near Oklahoma City
can expect it to begin near 8h 10m UT
(3:10 a.m. CDT). And near Savannah,
Georgia, look for the occultation to
occur within a minute or so of 8h 08m
UT (4:08 a.m. EDT).
On the night of May 21-22, the
88-km-wide main-belt asteroid 201
Penelope will temporarily dim the
light of a 9.9-magnitude star in Virgo.
Observers along a path that crosses
the western United States and Central
America will see the star appear to drop
to 13.7, the magnitude of Penelope. The
event could last as long as 40 seconds.
This long period of asteroid interference
centers on 5h 22m UT.
Analyses of Penelope's spectra suggest that it's an M-type, or metallic,
asteroid. Could its composition mean
that it's the leftover core of a larger,
now-destroyed asteroid? More observations will help pin down the details of
Penelope's faceted form.
About a week before both events,
more precise predictions and path maps
will be available from Steve Preston's
minor-planet occultation website
(asteroidoccultation.com). For advice
on timing occultations and reporting
observations, see asteroidoccultation.
com/observations.
s k y a n d t e l e s c o p e . c o m * M AY 2 0 1 8

http://www.imo.net http://www.asteroidoccultation.com http://www.asteroidoccultation.com/observations http://www.skyandtelescope.com/astronomy-clubs-organizations http://www.asteroidoccultation.com/observations http://www.skyandtelescope.com

Sky and Telescope - May 2018

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