My first Magazine Sky & Telescope - 01.2019

It wasn’t until 2003, with the dis- covery of the near-Earth asteroid 2003 EH 1 , that the shower’s parentage was revealed. Detected during the Lowell Observatory Near-Earth Object Search (LONEOS), 2003 EH 1 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 (10 13 kg, which is much higher than the 10 10 kg expected to be produced by a comet dur- ing 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 EH 1 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 10 13 kg stream mass. They detected no sublimation of ice, nor did it appear that 2003 EH 1 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 EH 1 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; com- pare 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 pre- dicted for 02 h UT January 4th (9 p.m. EST January 3rd), when the radiant in northern Boötes is only just peek- ing above the horizon in the north- northeast. 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 well- sorted 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 meteor- oids 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 maxi- mum 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 EH 1 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 occasion- ally 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 cre- ated by the French astronomer Jérôme Lalande in 1795. Quadrantid Meteor Shower 1 am, Jan 4 Big Dipper URSA MAJOR Polaris URSA MINOR 10° Mizar Little Dipper Quadrantid radiant DRACO BOÖTES HERC ULES Arcturus Looking Northeast sk yandtele scope.com • JA N UA RY 2 019 49

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