A distant comet that was as faint as magnitude 18 on October 20th has suddenly brightened by a millionfold, altering the naked-eye appearance of the constellation Perseus.
This startling outburst of Comet Holmes (17P) may be even stronger than the one that occurred 115 years ago, in November 1892, when the comet was first spotted by English amateur Edwin Holmes.
According to IAU Circular 8886, issued today by the Central Bureau for Astronomical Telegrams in Cambridge, Massachusetts, A. Henriquez Santana at Tenerife, Canary Islands, was the first to notice the outburst shortly after local midnight on Wednesday morning, October 24th. The comet was then about 8th magnitude, but within minutes Ramon Naves and colleagues in Barcelona, Spain, caught it at magnitude 7.3.
Internet discussion groups came alive with the news. "To my amazement, 17P had brightened to naked-eye visibility," exclaimed Bob King when he spotted Comet Holmes shortly before dawn in Duluth, Minnesota. "What a sight!" he posted to the Comets Mailing List. Alan Hale of Cloudcroft, New Mexico, concurred. To Hale (well known as the codiscoverer of Comet Hale-Bopp) it appeared essentially starlike in a telescope until he switched to high power.
Then things only got better. As Earth continued to turn, nightfall arrived in Japan. "It is visible with naked eyes in a large city!" posted Seiichi Yoshida, who observed the comet from beside Tsurumi River in Yokohama. By 17:15 Universal Time he was describing Comet Holmes as magnitude 2.8.
Comet expert Gary Kronk expects this object to remain bright and grow from a starlike point to several arcminutes across over the next few nights as it makes its way slowly westward across Perseus. Its position on October 25th (0h UT) is right ascension 3h 53m, declination +50.1° (equinox 2000), and by October 30th it will have moved only to 3h 48m, +50.4°. For those living in the Northern Hemisphere, Perseus is visible all night at this time of year.
Roger W. Sinnott
Sky & Telescope