This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of October 2008.

Planets

Venus is the very bright “star” close to the southwestern horizon for an hour or so after sunset. When it is above the horizon, it is the brightest “star” in the sky.

Jupiter is located in the constellation of Sagittarius. At the beginning of the month, Jupiter starts the night almost due south in the southern part of the sky. As the night progresses, it slowly moves to the west and sets around 11 pm local time. By Halloween, Jupiter starts the night low in the southwestern sky and sets around 9 pm. Jupiter is fainter than Venus but brighter than any star.

Saturn is located low in the east just before sunrise. It is as bright as many of the brightest stars.

Mercury is too close to the Sun at the beginning of the month. By the mid-month, it will become observable as a bright “star” low in the ESE sky just before sunrise. It reaches the best time for observation on Oct 22 when it is furthest from the Sun. It will continue to be observable for the rest of the month as it slowly drops towards the horizon.

Mars is too close to the Sun to be seen.

Meteors

October sees a number of meteor showers including one of the year’s best, the Orionids.

Sporadic Meteors

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, ten (10) or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Orionids (ORI)

The Orionids are the best shower during the month of October. When you see an Orionid meteor, you are seeing small pieces of Halley’s Comet which were released thousands of years ago. The Eta Aquarids of May are also from Comet 1P/Halley.

This shower is active from Oct 3 to Nov 11 with a broad peak between Oct 18 and 24. They radiate from northern Orion. During their peak, rates can be as high as 30-100 meteors per hour. Last year rates reached 70 meteors per hour and similar circumstances are predicted for this year with the best time being the morning of Oct 19 (for the US). However, a bright quarter Moon will wash out many of the fainter meteors resulting in smaller rates. Much of this year’s ORI meteors were released by Comet 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).

Minor Meteor Showers

Minor showers produce so few meteors that they are barely noticeable above the background of regular meteors.

Northern and Southern Taurids (NTA/STA)

The Taurids never produce more than ~5 meteors per hour. They make up for their low rates by being active for over two months and by producing many bright fireballs. Their fireballs are more apparent to the average observer because, unlike most meteor showers, the Taurids are observable all night long rather than just in the morning. They are active for the entire month of October with activity slowly building as the month progresses. Though named after the constellation of Taurus, the Taurids radiate from the constellation of Aries for most of October.

The Taurids are produced by Comet 2P/Encke. Encke is an enigmatic object with the shortest period for any known comet at 3.3 years. First observed in 1786, it has been observed over ~60 orbits and has been seen every year since 1993.

Delta Aurigids (DAU)

Until a few years ago, the September Perseids and the Delta Aurigids were considered part of the same shower. Analysis of the orbits of their meteors suggested that there are in fact two overlapping showers each originating from a different unknown long-period comet. Like the SPEs, this minor shower usually produces no more than ~3 meteors per hour at its maximum. There is some disagreement as to when this shower is active. Naked eye observations over the past few decades suggest a period of activity from Sept 18 through Oct 10 with a broad peak between Sept 23 and Oct 3. Recent video data finds a later period of activity between Oct 6 and 12 with no obvious peak. The DAUs radiate from the northern part of the constellation of Auriga just to the north of the bright star Capella.

October Camelopardalids (OCT)

This is a new shower first recognized in 2005, though sightings as early as 1902 have been recorded. A few OCAs are observable between Oct 1 and 10. The vast majority of meteors occur during a short  ~2 hour span at the time of peak activity. This year’s peak is predicted to occur within a few hours of ~14:00 UT (7:00 am PDT) on October 5. Unless the peak comes early it will occur after sunrise for observers in the western US. The peak time suggests a nice, but short, shower may be visible across the northern Pacific basin and in northeastern Asia. Since Camelopardalis is a far northern constellation, this shower is not visible from the Southern Hemisphere.

Draconids (Giacobinids) (GIA)

The Draconids have produced some of the highest rates of meteor activity in history. In both 1933 and 1946 rates were greater than 10,000 meteors per hour. Impressive rates of greater than 500 meteors per hour were also observed in 1952, 1985 and 1998. Unfortunately, this shower barely produces any meteors in non-storm years. What will this year hold in store? There are no predictions for any enhanced activity this year but we won’t know for sure unless we watch. This is another shower only observable from the Northern Hemisphere. It radiates from the constellation of Draco.

The Draconids are also known as the Giacobinids because they are produced by Comet 21P/Giacobini-Zinner. This comet was discovered by the same late 19th/early 20th century astronomer who found the recently re-discovered Comet 205P/Giacobini.

Epsilon Geminids (EGE)

This is an early morning shower which radiates from the constellation Gemini. It is visible between Oct 5 and 22 with a peak on Oct 14. At its best, only about 2 meteors per hour are visible.

Leo Minorids(LEO)

Yet another early morning shower, this time radiating from Leo Minor, a faint constellation just north of Leo. It is visible between Oct 17 and 27 with a maximum rate of only ~2 meteors per hour occurring on Oct 24.

Additional information on these showers and other minor showers not included here can be found at the following sites: Robert Lunsford’s Meteor Activity Outlook, Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2008 Meteor Shower Calendar.

Comets

Naked Eye Comets

There are no comets bright enough to be seen without binoculars or a telescope.

Binocular Comets

Comet C/2008 A1 (McNaught)

Comet McNaught is a long-period comet that will pass closest to the Sun on Sept 29 at a distance of 1.07 AU (100 million miles or 160 million km). It was the first comet discovered in 2008 having been found by  Robert McNaught of the Siding Spring Survey back on Jan 10. It was McNaught’s 43rd comet discovery.

Since discovery this comet could only be seen from the Southern Hemisphere. This month it moves rapidly to the north and is easily visible from the Northern Hemisphere by mid-month. During October, the comet travels through the constellations of Libra and Ophiuchus. The comet is as bright as it is going to get at magnitude 6.5. A comet of this brightness can be seen in binoculars or a small telescope.

A finder chart for Comet McNaught can be found at Comet Chasing.

Small Telescope Comets

Comet 6P/d’Arrest

Comet 6P/d’Arrest was one of the first short-period comets to be observed. First seen by the Frenchman Philippe de la Hire in 1678, the comet was definitively discovered by Heinrich Louis d’Arrest of Germany on 1851 June 28.

Comet d’Arrest is in a short-period orbit with a period of 6.5 years. It passed closest to the Sun back on Aug 14 at a distance of 1.35 AU (125 million miles or 200 million km). Comet d’Arrest starts the month in the southern constellation of Grus before entering Sculptor near months end. The comet is a very difficult object for observers in the Northern Hemisphere. With a brightness of magnitude 8.5 it will require a telescope to be seen though observers at very dark sites may be able to see it in binoculars.

A finder chart for Comet d’Arrest can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Asteroids

Binocular and Small Telescope Asteroids

(1) Ceres

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 the surface. Ceres is one of two targets for NASA’s Dawn spacecraft which is scheduled to visit it in 2015. This month Ceres is located low in the eastern sky right before sunrise in Leo at magnitude 8.7.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(2) Pallas

Pallas is also a carbonaceous asteroid though with a slightly bluish B-type spectrum. Due to its high inclination (tilt of its orbit with respect to Earth’s orbit) of 34 degrees it is a difficult target for future spacecraft missions. Pallas is large with dimensions of 350×334x301 miles or 582×556x501 km. This month it is located in the southern constellation of Lepus and brightens from magnitude 8.7 to 8.2 over the course of the month.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(4) Vesta

Though not as large as Ceres, Vesta is more reflective making it the brightest asteroid in the Main Belt. Vesta is peculiar in that it appears to have evidence of volcanism on its surface. Similar to the Moon, Vesta may be covered with large expanses of frozen lava flows. It is classified as a V-type asteroid and is the only large asteroid with this classification. Many of the smaller V-type asteroids are chips of Vesta blasted off it by past asteroid and comet impacts. Vesta is similar in size to Pallas with dimensions of 347×336x275 miles or 578×560×458 km. Vesta will also be visited by NASA’s Dawn spacecraft which will arrive in 2010. This month it is located in Cetus and brightens from magnitude 6.9 to 6.4 over the course of the month.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.

(9) Metis

Metis was discovered in 1848 by Andrew Graham of Ireland. It is a S-type asteroid with a composition similar to stony meteorites (ordinary chondrites). With a diameter of 140×120x85 miles or 235×195×140 km, it is much smaller than Ceres, Pallas or Vesta. In October Metis is located in Aries only a few degrees north of Vesta. It brightens from magnitude 9.4 to 8.6.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand.