In The Sky This Month – August 2010
August 2, 2010 14 Comments
This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of August 2010.
August 2010 Highlights * Venus, Mars and Saturn close in on each other in the evening sky * A 2nd trio of Venus, Mars and Spica form at the end of the month * Perseid meteor shower visible under great conditions * Mercury has a mediocre evening apparition in July/August (great from SH) * Comet 10P/Tempel 2 reaches small telescope brightness in the morning sky
Note: If anyone has pictures or observations of these objects/events and want to share them, send me a comment and I’ll post them on the blog.
Venus, Mars and Saturn – Venus is the brightest “star” visible in the early evening (at magnitude -4.3 to -4.6). Low in the west it sets about 1.9 to 1.5 hours after sunset. Maximum height above the horizon was reached a few months ago. As a result, Venus will appear to sink lower in the sky every night. Still, it will be well placed for easy observing as it is at its brightest this month. If you are located south of the equator, this is a much better apparition and Venus is sitting as high above the horizon as it can get. Regardless, of where you are located it will be hard to miss brilliant -4 magnitude Venus in the west an hour or 2 after sunset.
This month Venus, Mars and Saturn form a tight trio in the early evening sky. On August 8, Venus (magnitude -4.3), Mars (magnitude +1.5) and Saturn (magnitude +1.1) are located within 4.8° of each other.
August 8 - Venus and Saturn within 2.7° of each other August 13 - Moon passes within 4.2° of Venus, 7.3° of Saturn and 5.5° of Mars August 19 - Venus and Mars within 1.9° of each othe
Jupiter – Jupiter once again returns to sight as a brilliant star in the east-southeast a few hours after sunset. The magnitude -2.6 planet will get brighter and better place for observing over the next few months. Last year Jupiter made a series of close approaches to Neptune. This year Jupiter will do the same for Uranus. All month long Jupiter will be located within a few degrees of Uranus.
August 27 - Moon passes within 6.7° of Jupiter
Mercury – Mercury is in the midst of a mediocre evening apparition for northern observers. The apparition is a great one for southern hemisphere observers.
August 12 - Moon passes within 2.2° of Mercury
Meteor activity is near a yearly maximum in August. The year is usually split in 2 with January through June having low rates with few major showers while July through December (really through the 1st week of January) have high rates with many major showers.
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 August, 12-18 or so Sporadic meteors can be observed per hour from a dark moonless sky.
Major Meteor Showers
The Perseids are one of 2 showers that are worth getting up early for. This year the Moon will set early in the evening so the prime meteor watching hours will be nice and dark. Based on the their behavior in prior years a broad maximum is expected between 2010 Aug. 12, 18:30 UT and Aug. 13, 7:00 UT. There may even be a little enhancement as we pass through a dust trail ejected by the Perseids’ parent comet, Swift-Tuttle, in 441 AD at 13:19 UT on Aug. 13 (from the work of Mikhail Maslov). An additional dust trail created in 1479 may also add a few meteors. The enhancements will be small and may only add another 10 or so meteors per hour to the expected maximum rate of 100 per hour.
These rates will only be visible for those under a very dark sky when the radiant is high in the sky. For most of us, rates will be lower due to light pollution. Still, unless you live in a bright major city, you should be able to see a few dozen meteors per hour.
The best time to look will be after about 1-2 am on the night of August 12/13. Meteors will appear to radiate from the constellation of Perseus in the northeast sky.
Minor Meteor Showers
Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Starting this month, info on most of the minor showers will be 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 following sites: Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2010 Meteor Shower Calendar.
Naked Eye Comets (V < 6.0)
Binocular Comets (V = 6.0 – 8.0)
Small Telescope Comets (V = 8.0 – 10.0)
Comet 10P/Tempel 2
’10P’ says it all. This was only the 10th comet to be observed at a 2nd apparition meaning we’ve been following this comet for a long time. Discovered by prolific German comet discoverer Ernst Wilhelm Leberecht Tempel in Marseille, France on July 4, 1873, Tempel 2 has been observed at nearly every return since then. The comet’s current orbit brings it to within 1.42 AU of the Sun on July 4 and to within 0.65 AU of Earth in late August.
The comet is currently at a brightness of 9.0 to 9.5 magnitude. This is a large diffuse object so it will be more difficult to see than your average 9th magnitude comet or deep sky object. From my moderately light polluted backyard and 12″ telescope, the comet was a difficult object and was estimated to be magnitude 10.0. From a dark site and 30×125 binoculars, the comet was much brighter (magnitude 9.5), larger and easier to see. The added brightness was probably due to the dark site allowing me to see much more of the comet’s coma.
At mid-month the comet will be 1.49 AU from the Sun and 0.66 AU from Earth. Tempel 2 is a morning object moving from the constellation of Aquarius to Cetus.
A finder chart for Comet Tempel 2 can be found at Comet Chasing.
Binocular and Small Telescope Asteroids (V < 9.0)
Ceres is the biggest asteroid in the Main Belt with a diameter of 585 miles or 975 km. It is so big that it is now considered a Dwarf Planet. Classified as a carbonaceous (carbon-rich) Cg-type asteroid, there are suggestions that it may be rich in volatile material such as water. Some even propose that an ocean exists below its surface. Ceres is the other target of NASA’s Dawn spacecraft which is scheduled to visit it in 2015.
This month Ceres is a month past opposition. The asteroid will start the month at magnitude 8.1 and fade to magnitude 8.6 by the end of the month. All month long it will slowly moving in the constellation Ophiuchus.
(6) Hebe and (8) Flora
These 2 large inner Main Belt asteroids will move in tandem this fall. Both are S-type asteroids with similar compositions and albedos. (6) Hebe is the larger of the pair (205 x 185 x 170 km). Recent research suggests that it is the source of many ordinary chondrite meteorites and near-Earth asteroids. (8) Flora is a little smaller (136 x 136 x 113 km) and is the largest surviving member of a numerous asteroid family created by a long ago impact.
This month Hebe is retrograding in Cetus and will brighten from magnitude 8.7 to 8.0. Just across the border in Aquarius Flora will brighten from magnitude 9.2 to 8.4.