This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of December 2008. The biggest event of the month will be the Venus-Jupiter-Moon conjunction on the 1st. On the 13th, the Geminid meteor shower will peak. Though usually one of the best showers of the year, the Full Moon will ruin the show.

Planets

Venus and Jupiter start off the month in grand fashion. On the 1st, the two are located in the south-southwest just after sunset within 2 degrees of each other. Venus is by far the brighter of the pair. Not that Jupiter is a slouch only being the brightest “star” in the sky after Venus. To add to the sight, a thin crescent Moon will be located just to the upper left of the pair.

As the month progresses, Venus will rapidly move away from Jupiter. Venus will appear to start each evening higher and higher in the sky. Jupiter, on the other hand, will quickly drop towards the horizon and by the end of the month, will be located close to the southwest horizon. But Jupiter will not be alone and ends the month within 1.3 degrees of the innermost planet Mercury. The Moon can also be used at the end of the month to find the evening planets as it passes close to Jupiter and Mercury on the 29th and Venus on the 31st.

This month, Saturn starts to rise before midnight. The best time to observe it, though, is just before the start of dawn when it will be located high in the sky in the constellation of Leo. The Moon will pass close to Saturn on the nights of the 18th and 19th.

Mars is too close to the Sun to be seen.

Meteors

The month of December experiences 2 major showers, the Geminids and the Ursids, and a slew of minor ones.

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 November, twelve (12) or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Geminids (GEM)

Along with the Perseids of August, the Geminids are one of the best meteor showers delivering great displays year after year. Unfortunately, this year sees the worst circumstances possible for Geminid watching as the nearly Full Moon is located right next to the radiant. Similar circumstances occurred in October for the Orionids but observers were still able to see quite a few meteors.

According to Sirko Molau’s analysis of video data, the Geminids are already observable at the beginning of the month though their rates are very low. The peak is predicted for the nights of December 13-16. With a radiant near the star Castor in the constellation of Gemini, the Geminids are one of the rare major showers that are observable before midnight and can be observed as early as 8:00 pm though rates are usually best after 10:00 pm. Under a dark rural moon-less sky, the Geminids can produce as many as 100+ meteors per hour. With the bright Moon, rates of a few tens of meteors per hour may still be observed.

The Geminids are the result of the break-up and subsequent activity of the “asteroid” Phaethon. Why asteroid in quotes? Most meteor showers come from comets yet Phaethon is on a very non-cometary orbit and has never shown any cometary activity. There is still much scientific discussion about what exactly Phaethon is.

More details on the Geminids and their parent “asteroid” Phaethon will be posted as we get closer to its peak.

Ursids (URS)

The Ursids will produce up to 10 meteors per hour at their peak on December 22-23. That rate makes it a borderline major/minor shower though the Ursids have experienced a number of outbursts in the past. With a radiant near the “bowl” of Ursa Minor (the “Little Dipper”), this shower is also observable all night long though the best time to observe it is during the last hours of the night. More details on the Ursids and their parent comet, Comet Tuttle, will be posted later.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors.

December Phoenicids (PHO)

The December Phoenicids (also just called the Phoenicids) radiate from the far southern constellation of Phoenix. Due to its southern radiant, this shower is very difficult to observe from the Northern Hemisphere. The shower results from the break-up or splitting of Comet P/1819 W1 (Blanpain) in 1819. Most years the shower only produces a few meteors per hour but on occasion up to 100 meteors per hour have been seen (1887, 1938 and 1956). No further outbursts are predicted until 2050 though that doesn’t mean we can’t be surprised. The shower is predicted to peak on December 6. In 2003, the barely active nucleus of Comet Blanpain was re-discovered by the Catalina Sky Survey.

Puppid/Velids (PUP)

These showers are another two for the southern hemisphere. There is evidence that the Puppids and the Velids are part of a much larger complex of showers that span from November through February. Their orbits suggest they are the result of the break-up of a yet-to-be-discovered comet or asteroid on a high inclination orbit (50-70 degrees). At their best, Puppid/Velids produce 5-10 meteors per hour for those south of the equator. Not too many are visible for northern hemisphere observers.

Monocerotids (MON)

The December Monocerotids (sometimes just called the Monocerotids) are produced by Comet C/1917 F1 (Mellish). Discovered in 1917 this bright comet is on a ~145 year orbit and isn’t due back till around 2062. There is evidence that this shower may have produced a number of bright fireballs during the 11th through 16th century. The shower is predicted to peak on December 7th-9th with a paltry 2 meteors per hour radiating from the faint constellation of Monoceros (located just east of Orion).

σ-Hydrids (HYD)

With a peak on December 9th of only 3 meteors per hour, these meteor from the “head” of the constellation of Hydra will be difficult to observe by all but the most advanced observers. Not much is known about this shower other than it was created by an unknown long-period or Halley-type comet with a perihelion of ~0.25 AU and an inclination of ~125 to 130 degrees.

Coma Berenicids (COM)

The Coma Berenicids are another minor shower with rates of ~5 meteors per hour at their peak. The shower is active from mid-December to late January as its radiant moves from southern Ursa Major through Coma Berenices and into Virgo. The shower may have been created by Comet C/1913 I (Lowe) a retrograde Halley-type comet. That is assuming Comet Lowe ever existed. There are some doubts that the comet was real since other observers were not able to observe the comet.

According to Peter Jennisken’s book “Meteor Showers and Their Parent Comets” a number of meteor outbursts seen between the years of 609 AD and 764 AD may have caused by this shower.

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/2007 N3 (Lulin)

The brightest comet of the month is not visible for the 1st half of the month. Comet Lulin will be too close to the Sun until after mid-month when it will be visible low in the southeast (near the “head” of Scorpius) at the start of dawn. Comet Lulin was discovered by the Lulin Sky Survey in Taiwan on 2007 July 11. At the time the comet was located beyond the orbit of Jupiter.

The comet will be closest to the Sun on 2009 January 10 at 1.21 AU from the Sun. It will be closest to Earth in late-February when it will be only 0.41 AU from us. At that time the comet may be as bright as 4th magnitude making it an easy object for binoculars and small telescopes. In fact, the comet will be visible to the naked eye as a small faint fuzzball from dark sites.

In December the comet should brighten from 7th magnitude to 6th. I say “should” because the comet has not been seen since late October because it has been too close to the Sun. As a result, we don’t know how bright Lulin is right now. Baring a new discovery or unforeseen outburst, Comet Lulin may be the best comet of 2009.

A finder chart for Comet Lulin 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.

Small Telescope Comets

Comet C/2008 A1 (McNaught)

Comet McNaught is a long-period comet that passed 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 January 10. It was McNaught’s 43rd comet discovery.

The comet is only visible from the Northern Hemisphere and during December it travels through northern Ophiuchus into southern Hercules. After getting as bright as 6th magnitude at perihelion, the comet will slowly fade from magnitude 8.8 to 10.0 during the month. This will probably be the last month to see this comet in regular sized backyard telescopes.

A finder chart for Comet McNaught 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.

Comet C/2006 W3 (Christensen)

This comet was discovered over 2 years ago on 2006 November 18 by Eric Christensen of the Catalina Sky Survey north of Tucson. At the time the comet was located at 8.7 AU from the Sun which is nearly the distance of Saturn. The comet continues to move closer to the Sun and Earth and is currently 3.8 AU from the Sun and 3.4 AU from the Earth.

The comet is currently around magnitude 10.2 and will slowly brighten during the month.  It will be traveling south through the constellations of Cepheus and Lacerta and is nicely positioned for evening observing. I was able to observe the comet visually with my backyard 12″ reflecting telescope a few weeks ago. Being small and condensed, the comet was fairly easy to see.

The comet will continue to brighten as it approaches perihelion at a still rather distant 3.12 AU from the Sun on 2009 July 6. At the time, the comet will be 8th magnitude and visible in many smaller backyard telescopes and even binoculars from dark sites. Christensen should remain bright enough to see in modest sized backyard telescopes for all of 2009.

A finder chart for Comet Christensen 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.

Comet P/2003 K2 (Christensen)

Yet another comet discovered by Eric Christensen may be visible in backyard scopes in December. This comet is a short-period comet with a period of 5.7 years. It is very faint except when close to the Sun. With perihelion predicted for 2009 January 8 at a distance of 0.53 AU from the Sun, the comet may be bright enough for backyard observers by the end of the month.

There are a lot of question marks about this comet. It was only observed for 1 month in 2003 and those observations were made after perihelion. The comet has yet to be observed during this return and its exact location is unknown. Plus since the comet has never been observed before perihelion we don’t know how bright it should be. Hopefully the comet will be picked up in the next few weeks. When/if that happens, we’ll have a better idea of how observable it will be.

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 high in the sky right before sunrise in Leo brightening from magnitude 8.3 to 7.9.

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 moves through the far southern constellations of Columba and Caelum. It peaks at magnitude 8.0 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. On October 30, Vesta was at opposition (directly opposite from the Sun in the sky) and at its brightest. This month Vesta will fade from magnitude 7.0 to 7.6 as it moves through Pisces.

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. During the month, it will quickly fade from magnitude 9.1 to 9.8 as it travels through Aries just a few degrees northeast of Vesta.

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