Sky & Telescope - January 2019 - 49

It wasn't until 2003, with the discovery of the near-Earth asteroid 2003
EH1, that the shower's parentage was
revealed. Detected during the Lowell
Observatory Near-Earth Object Search
(LONEOS), 2003 EH1 follows an orbit
much like the one proposed for the
Quadrantids and is likely an extinct
Jupiter-family comet or the remnant
of a disintegrated comet nucleus. Peter
Jenniskens (NASA Ames, now at the
SETI Institute) suspects that the large
total mass of the shower (1013 kg,
which is much higher than the 1010 kg
expected to be produced by a comet during a single return) could be explained
by the recent breakup of a larger active
body. The massive remnants may have
acted like small comets soon after the
breakup, feeding the fresh stream, but
they're now extinct, or at least dormant.
In 2015, Toshihiro Kasuga (Chiba
Institute of Technology, now at National
Astronomical Observatory of Japan)
and David Jewitt (Kitt Peak National
Observatory/UCLA) conﬁrmed that
2003 EH1 showed no ongoing mass
loss, and that the total mass loss of the
object over the course of the 200- to
500-year age of the shower is too small
to produce the reported 1013 kg stream
mass. They detected no sublimation
of ice, nor did it appear that 2003 EH1
released dust due to heat fracture when
it's closest to the Sun (as does the rock
comet 3200 Phaethon). Subsequently,
they suggested that another source has
fed the stream, or that 2003 EH1 isn't
completely extinct, but dormant. It only
episodically releases material.
This somewhat mysterious origin
seems appropriate for such a poorly
observed shower. According to the
International Meteor Organization
(IMO), only 32 observers submitted
data for the 2018 Quadrantids; compare that to the 203 individuals who
ﬁled observational data for the 2018
Perseids. This low participation can
probably be explained by the shower's
short peak, a poorly placed radiant, and
u By 1 a.m. local time the Quadrantid shower's
radiant in northern Boötes is well above the
horizon for observers at mid-northern latitudes.

the potential for the peak to fall during
bad weather in northern climes.
This year offers a mix of conditions
for the Quadrantids. New Moon falls
on January 6th, so won't interfere with
observations. But maximum is predicted for 02h UT January 4th (9 p.m.
EST January 3rd), when the radiant
in northern Boötes is only just peeking above the horizon in the northnortheast. The radiant climbs higher
throughout the evening, but by the
time it's decently placed, around 1 a.m.
local time, the shower is wrapping up.
The weather during maximum? That's
anybody's guess.
The Quadrantid stream appears wellsorted by mass. A small peak for fainter
objects (radio or telescopic meteors)
may occur up to 14 hours before visual
and photographic maximum, when
anywhere between 60 and 200 meteoroids could be detected per hour. On a
few returns, the peak for radio meteors
occurred 9 to 12 hours after visual. The
IMO encourages observers to watch
through the predicted period of maximum as well as at the outer range of
the shower, so if you are clouded out at
actual peak, try again 6 or 8 hours later.
For more detailed instructions regard-

Shower Sources
Shower

Parent Object

Quadrantids
Lyrids

2003 EH1
Comet Thatcher
(C/1861 G1)

Eta Aquariids

Comet 1P/Halley

Delta Aquariids

Comet 96P/
Machholz

Perseids

Comet 109P/
Swift-Tuttle
Comet 1P/Halley

Orionids
Leonids

Comet 55P/
Tempel-Tuttle

Geminids

3200 Phaethon

ing recording and reporting, visit the
IMO Visual Observations page (https://
is.gd/IMOvisual).
The Quadrantids are occasionally referred to as the Boötids, as the
shower's radiant lies in the modern
constellation of Boötes. When the
shower was ﬁ rst witnessed in 1835,
however, that part of the sky still
belonged to Quadrans Muralis, the
Mural Quadrant, a constellation created by the French astronomer Jérôme
Lalande in 1795.

Quadrantid Meteor Shower
1 am, Jan 4

Big
Dipper
Polaris

URSA
MINOR

URSA
MAJOR
10°
Mizar

Little Dipper
Quadrantid
radiant

DRACO

BOÖTES

HERC ULES

Arcturus

Looking Northeast

sk yandtele scope.com * JA N UA RY 2 019

https://www.is.gd/IMOvisual https://www.is.gd/IMOvisual http://www.skyandtelescope.com

Sky & Telescope - January 2019

Table of Contents for the Digital Edition of Sky & Telescope - January 2019