Sky and Telescope - November 2017 - 50

NOVEMBER 2017 OBSERVING
Celestial Calendar

that sifts through all of it and creates a
light curve for any small spot on the sky
you care to specify, such as an accurate
star position. Results may take a few
minutes to appear. (Stars brighter than

8th magnitude overexpose the detectors
and cannot be usefully measured.)
u An automated array of ASASSN patrol
cameras, with long dew shields, on Mount
Haleakala, Hawai'i.

* For current news of Comet ASASSN1's behavior, and to see how your observations
match others', see the Recent Observations box on the home page of the Comet
Observation database, cobs.si, as well as updates at skyandtelescope.com.

The Taurids Are Back
HAVE YOU EVER SEEN a Taurid ﬁre-

ball? An unusually bright, unusually
slow meteor on an October or November evening, sailing away from the
general direction of Taurus or Aries as
they climb the eastern sky?
The Taurid shower is unusual for
several reasons. It's divided into two
sub-branches, the Southern and Northern Taurids, with large, poorly deﬁned
radiants about 6° apart. The peak dates
of the two branches are sometimes
listed as November 5th and 12th,
respectively. But both branches are so
long-lasting - meaning the meteoroid

streams are so wide - that they overlap
greatly. In fact, recent video and visual
plotting work indicate that the southern
branch "probably reaches its peak about
a month before the northern one,"
according to the 2017 Meteor Shower
Calendar of the International Meteor
Organization (IMO).
And because the radiant spots rise
high in the east moderately early,
evening skywatchers are not left in the
fringes of the action as happens with
most meteor showers, whose radiants
only rise high in early morning hours.
The Taurids are sparse at all times,

with zenithal hourly rates reaching only
about 5 meteors visible per hour even
under ideal conditions. But an unusually high proportion of these few are
bright. Occasionally a Taurid ﬁreball is
long and dazzling enough for people to
call the police to report a burning plane
falling out of the sky.
In 2005 a sub-stream of unusually
large Taurid meteoroids intersected
Earth's orbit. These were the sizes of
pebbles to small stones, rather than
the sand grains to peas typical of most
meteoroid streams, and the resulting
"Halloween Fireballs" made the news.
There's been no repeat of this outburst,
but the name has stuck. Don't take it
too literally; think Halloween plus or
minus several weeks.

p A dazzling Taurid fireball streaked down to the left of Fomalhaut while Marko Korošec had
his camera open to the sky over Brkini, Slovenia, early on the evening of October 30, 2015.

N O V E M B E R 2 0 17 * S K Y & T E L E S C O P E

A more ordinary shower should peak
on the mornings of November 17th
and 18th, in the dark of the Moon this
year. But the Leonids, a grand spectacle around the turn of this century,
have since diminished into obscurity.
The IMO is predicting a peak zenithal
hourly rate of about 15, so prepare for
quiet meteor watches.
If you want to do a useful, scientiﬁc
meteor count for the IMO, you can read
about how to do it, and where to report,
at imo.net/observations/methods/
visual-observation/major/. The IMO
has overhauled its website since you
may have last looked; check it out.

CA MER A A RR AY: ASASSN / OHIO STATE UNIV ERSIT Y

The Leonids

http://www.cobs.si http://www.skyandtelescope.com http://www.imo.net/observations/methods/visual-observation/major/ http://www.imo.net/observations/methods/visual-observation/major/

Sky and Telescope - November 2017

Table of Contents for the Digital Edition of Sky and Telescope - November 2017