In the Transient Sky – October 2012
September 30, 2012 1 Comment
October 2012 Highlights * Orionid meteor shower peaks on the night of October 20-21 * Venus and Regulus pair up on the morning of the 3rd * Mars and Antares pair up on the evening of the 20th Note: If anyone has pictures or observations of these objects/events and want to share them with my readers, send them to the Transient Sky at <email@example.com>.
Mercury – For northern hemisphere observers, Mercury spends the month in a very poor evening apparition. The best time to try and spot Mercury will be on the 16th when a very young, day old Moon is just to the lower right of Mercury. South of the equator, the show is much better as this is one of Mercury’s best evening apparitions of the year.
Mars – Continuing its slow descent towards the Sun in the evening, Mars glows at a rather meager +1.2 magnitude. On the 20th and for a few days on either side of that date, Mars pairs up with its nemesis, Antares (in ancient Greek, ‘the anti-Mars’). Antares is just a bit brighter than Mars at magnitude +1.1 and both objects are red. You can spot the two low in the SW at the end of evening twilight. The Moon joins the show on the evenings of the 17th and 18th.
Jupiter – Jupiter rises around 10-11 pm at the start of the month and around 8-9 pm at the end of the month. Still it is considered a morning object because it reaches its highest point in the sky after midnight. Shining between magnitude -2.5 to -2.7, it is the brightest object in the night sky after the Moon and Venus. This month Jupiter is slowly traveling among the picturesque stars of the winter Milky Way constellation of Taurus as it heads towards opposition on December 3rd. The Moon passes nearby on the nights of Oct. 5th and 6th.
Venus – Venus rises about 3.5 hours before the Sun this month. In a telescope the planet will appear more than half-illuminated (about 70-80%). At magnitude – 4.1, Venus is by far the brightest ‘star’ in the morning sky. October sees Venus make a tight pair (0.2°) with Regulus, the brightest star in Leo, on the 3rd. The Moon also passes to the south of Venus on the morning of the 12th.
Saturn – The ringed planet is too close to the Sun to be easily seen this month.
The year is usually split in 2 with January through June having low rates with few major showers while July through December have high rates with many major showers. Meteor activity is at an annual peak this month.
Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During October mornings, 10 or so Sporadic meteors can be observed per hour from a dark moonless sky.
Major Meteor Showers
Orionids (ORI) [Max Date = Oct 21, Max ZHR = ~35-45 per hour]
The Orionids are one of the most reliable and productive showers of the year. Another point in their favor is their high level of activity over the course of ~5 nights or so. This gives ample opportunity to catch a few Orionid meteors. This year the waxing Moon will set before midnight making for nice dark skies during the prime Orionid-watching early morning hours.
The meteors that make up the Orionid shower were originally released by the one comet everyone has heard of, Comet Halley. Computer simulations of the past movements of Halley and its dust suggest that many of this year’s Orionid meteors were released by Halley between 1265 BC and 910 BC (for some points of reference, the Trojan War took place around 1200 BC and King David ruled around 1000 BC).
The Orionids are usually active from Oct 3 to Nov 11 with a broad peak between Oct 18 and 24. During their peak, rates can be as high as 20-70 meteors per hour. During the last two years ZHRs reached 35-45 meteors per hour which is nearly half the rate observed in 2007 (70 per hour). This year’s activity should be similar to the last few years.
The Orionids appear to come from an area in northern Orion. This area, called the radiant, rises around 10pm local time. It is best to wait till the radiant is high in the sky before looking for meteors (say 1am). The radiant is highest around 3:30am which is the best time to look. Meteors can appear anywhere in the sky so you don’t have to look at the radiant.
Minor Meteor Showers
Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Info on many minor showers are provided on a weekly basis by Robert Lunsford’s Meteor Activity Outlook.
Additional information on these showers and other minor showers not included here can be found at the International Meteor Organization’s 2012 Meteor Shower Calendar.
Naked Eye Comets (V < 6.0)
None this month.
Binocular Comets (V = 6.0 – 8.0)
None this month
Small Telescope Comets (V = 8.0 – 10.0)
None this month