http://www.skyandtelescope.com.au 47by Con Stoitsis METEORSThe ever-reliable Eta Aquariids
Don’t let the Moon spoil your meteor observing fun.
T
he Eta Aquarid shower never fails
to put on a good show, and is best
seen from our southern skies.
Like the Orionids in October, the Eta
Aquariid meteoroid stream is associated
with comet 1P/Halley. The meteors are
often fast and bright and are usually
yellow, although orange and blue is also
often seen. Many of them leave persistent
trains, some lasting for minutes.
In recent years, overall rates as well
as the number of bright meteors have
been increasing. The average magnitude
has increased to 2.4, and fireball and
bolide activity, although low, is also
on the rise. International Meteor
Organisation (IMO) analyses based on
data collected between 1984 and 2001,
have shown that the zenithal hourly
rates (ZHRs) are generally above 35 in
the period May 3 to 10.
A relatively broad maximum occurs
around May 5/6, sometimes with a
variable number of sub-maxima either
side of that date. The IMO has predicted
several sub-maxima for 2018, the first
one being on May 3 at 19:11 UT, from
small particles left in the 164 BCE trail
of comet 1P/Halley. There are three
other sub-maxima predicted for May
5, from particles in the comet’s 218 CE
trail. The first is expected to occur at
05:49 UT, the second at 07:34 UT, and
the third at 07:35 UT.
Although the radiant is low, Eta
Aquariids tend to have very long paths,
so start your observations early; say,
around 3:00am. And even though this
year the waning gibbous moon (full on
April 30; last quarter on May 8) will
affect observations, nevertheless, it will
be worth getting up and having a look.CON STOITSIS is director of the
Astronomical Society of Victoria’s comet
and meteor sections. Follow him on
Twitter @vivstoitsisAPRIL(dates in AEST)
1 Moon 7° north of Spica
2 Mars 1.3° south of Saturn
4 Jupiter 4° south of Moon
7 Saturn 1.9° south of Moon
8 Mars3°southofMoon
14 Mercury 4° north of Moon
18 Venus 5° north of Moon
18 Saturn stationary
19 Aldebaran 1.1° south of Moon
22 Moon8°southofPollux
24 Venus3.6°southofthePleiades
25 Regulus1.2°southofMoon
30 Mercury greatest elong. west (27°)SKY PHENOMENA LUNAR PHENOMENA
APRIL
Last Quarter ...... 8th, 07:18 UT
New Moon ...... 16th, 01:57 UT
First Quarter ...... 22nd, 21:46 UT
Full Moon ...... 30th, 00:58 UT
Apogee ...... 8th, 06h UT, 404,144 km
Perigee ...... 20th, 15h UT, 368,714 km