We are now in totality. Luckily the thick cirrus has moved out and it’s relatively clear here in Tucson.
The astronomical event of the month is Tuesday morning’s Total Lunar Eclipse. With the Moon riding high in the sky near the border of Taurus and Gemini, the eclipse is perfectly placed for observers in North America.
Check out the Shadows and Substance site for animations and graphics about tonight’s eclipse.
The table below lists times for all 4 American time zones. Though the penumbral part of the eclipse starts at 5:28 UT, most people won’t see a noticeable darkening of the Moon until sometime around 6:00 UT.
UT EST CST MST PST Start of Penumbral Eclipse 5:28 12:28a 11:28p 10:28p 9:28p Start of Partial Eclipse 6:32 1:32a 12:32a 11:32p 10:32p Start of Total Eclipse 7:40 2:40a 1:40a 12:40a 11:40p Mid-Eclipse 8:17 3:17a 2:17a 1:17a 12:17a End of Total Eclipse 8:54 3:54a 2:54a 1:54a 12:54a End of Partial Eclipse 10:02 5:02a 4:02a 3:02a 2:02a End of Penumbral Eclipse 11:06 6:06a 5:06a 4:06a 3:06a
Dec 16th did bring some rain as forecast (0.24″ to be exact). Not since Nov 28 have we had any rain at the house and not since Oct 20 have we had any measurable precipitation. Even with the rain and clouds, the sky cleared up after midnight and SALSA3 was able to pick up 3 meteors through the fog. So the streak still stands and is currently at 85 nights. Unfortunately the entire western US is being hammered by a wet winter storm system so the next few nights will be iffy.
Obs Date(UT) Time TOT SPO ANT HYD DLM MON COM URS SAL3 2010-12-19 05h 46m 17 13 0 3 1 0 0 0 ALLS 2010-12-19 04h 51m 14 10 1 3 0 0 0 0 SAL3 2010-12-18 03h 45m 12 7 0 2 1 0 1 1 ALLS 2010-12-18 03h 51m 7 5 0 1 1 0 0 0 SAL3 2010-12-17 01h 15m 3 3 0 0 0 0 0 0 ALLS 2010-12-17 00h 00m Left Off Due to Rain SAL3 - SALSA3 camera in Tucson (Carl Hergenrother) ALLS - Near all-sky camera in Tucson (Carl Hergenrother) VIST - Visual observations from Tucson (Carl Hergenrother) VISH - Visual observations from Hermosillo (Salvador Aguirre) HERM - PARENI camera in Hermosillo (Salvador Aguirre) SDG - Camera in San Diego operated by Bob Lunsford Time - Total amount of time each camera looked for meteors TOT - Total number of meteors detected SPO - Sporadics (meteors not affiliated with any particular meteor shower) ANT - Antihelions HYD - Sigma Hydrids DLM - December Leonis Minorids MON - Monocerotids COM - Coma Berenicids URS - Ursids
The Meteor Activity Outlook is a weekly summary of expected meteor activity written by Robert Lunsford, Operations Manager of the American Meteor Society and contributor to this blog. The original unedited version of this week’s Meteor Activity Outlook can be found at the American Meteor Society’s site.
No matter where you live, the first half of December provides some of the best meteor activity of the year. In the northern hemisphere the sporadic rates are still strong plus you can also count on strong activity from the Geminids, which peak on December 14. There are also several minor radiants that add a few meteors each hour. All of these centers of activity are located high in the sky during the early morning hours this time of year. Much of the activity mentioned above can also be seen from the southern hemisphere. While the sporadic rates are not as strong as those seen from the north, they are stronger than the previous months and heading for a maximum in January. The warm, but short summer nights south of the equator make for some great viewing as long as the moon does not interfere.
During this period the moon reaches its full phase on Tuesday December 21st. At this time the moon lies opposite the sun and is above the horizon all night long from most locations. This is the worst time to attempt to view meteor activity as the bright moonlight will obscure all but the brightest meteors. The estimated total hourly rates for evening observers this week is ~3 from the northern hemisphere and ~2 for observers south of the equator. For morning observers the estimated total hourly rates should be ~10 from the northern hemisphere and ~9 as seen from the southern hemisphere. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Rates are reduced during this period due to moonlight.
The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning December 18/19. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.
The following showers are expected to be active this week. The detailed descriptions will be continued next week when the moonlight is not as intense.
Shower Name RA DEC Vel Rates km/s NH SH ANT Antihelions 06h 40m +23 30 2 2 MON Monocerotids 07h 08m +07 41 <1 <1 GEM Geminids 07h 56m +31 35 1 1 HYD Sigma Hydrids 08h 56m +00 61 <1 <1 DLM Dec Leonis Minorids 10h 44m +31 71 1 <1 COM Coma Berenicids 11h 48m +18 65 2 <1 URS Ursids 14h 12m +75 33 <1 <1 RA - Right Ascension DEC - Declination Vel - Velocity relative to Earth (in km per sec) Rates - Rate of visible meteors per hour from a dark site NH - Northern Hemisphere SH - Southern Hemisphere
A week ago, Steve Larson of the Catalina Sky Survey came across a bright but peculiar looking comet. At 13th magnitude it was strange to find a new comet that bright in a part of the sky that had been picked over numerous times in the past month or two. Even weirder was the appearance of the comet, a bright stellar core with 2 tails, one straight and one curving almost 180°. But the oddest thing about this new find is that the object isn’t new at all. In fact, it had been discovered over 100 years ago back in 1906. Only from the time of discovery till two night ago it was known as asteroid (596) Scheila.
Up until ~15 years ago, the line between comets and asteroids was sharp and easy to see. Asteroids were rocks baked dry by billions of years of orbiting relatively close to the Sun. Comets were dirty snowballs born in the outer reaches of the Solar System. Sure there were a few objects that straddled the line such as Comets Encke and Wilson-Harrington but those objects could be hand-waved into one camp or the other.
But in 1996 the discovery of Comet Elst-Pizzaro changed all that. This comet was on a boring Main Belt asteroid orbit and probably had been for most of the history of the Solar System. Here was an example of an asteroid that was not bone dry but had, somehow, retained some volatiles over the past 4.5 billion years. It wasn’t long before more ‘Main Belt Comets’ were found: 176P/LINEAR, 238P/Read, P/2008 R1 (Garradd), P/2010 R2 (La Sagra). And now we get to add the large, 100+ km asteroid (596) Scheila to the list. [Note, that though Comet P/2010 A2 (LINEAR) is also on a Main Belt orbit, recent studies suggest its cometary appearance was the result of an asteroid-to-asteroid collision rather than cometary outgassing.]
I was finally able to get an image of this object a few nights ago. The ghostly ‘wings’ extending out from Scheila is dust ejected during its outburst. Based on images from the Catalina Sky Survey, the outburst occurred a day or two before December 3. So the image below was taken 11-12 days after the outburst.
Two nights ago my cameras detected a total of 206 Geminids (some were probably duplicates). One night ago the total number dropped to 32 Geminids. Last night the number of Geminids was a whopping 2. It’s amazing how quickly the Geminids can fall off after their peak. It is safe to say that the 2010 Geminids are pretty much over for visual observers.
Last night marked SALSA3’s 82nd straight night with a meteor detection. With it currently raining and more forecast for tonight the streak may very well end at 82.
Obs Date(UT) Time TOT SPO ANT GEM HYD DAD DLM MON COM SAL3 2010-12-16 05h 54m 19 10 1 0 2 1 3 1 1 ALLS 2010-12-16 04h 58m 19 12 1 2 1 1 2 0 0 HERM 2010-12-16 11h 31m 9 7 0 1 1 - - 0 0 SAL3 - SALSA3 camera in Tucson (Carl Hergenrother) ALLS - Near all-sky camera in Tucson (Carl Hergenrother) VIST - Visual observations from Tucson (Carl Hergenrother) VISH - Visual observations from Hermosillo (Salvador Aguirre) HERM - PARENI camera in Hermosillo (Salvador Aguirre) SDG - Camera in San Diego operated by Bob Lunsford Time - Total amount of time each camera looked for meteors TOT - Total number of meteors detected SPO - Sporadics (meteors not affiliated with any particular meteor shower) ANT - Antihelions GEM - Geminids HYD - Sigma Hydrids DAD - December Alpha Draconids DLM - December Leonis Minorids MON - Monocerotids
What a difference 24 hours makes! Only a day removed from the Geminids peak and rates have crashed to a fraction of their peak. During the past 5 nights SALSA3 detected 12, 22, 69, 124 and now 20 Geminids. This is a characteristic of the Geminids in that the post-peak rates fall off much more rapidly than the pre-peak increase.
The night of Dec 14/15 marked the 81st consecutive nights that SALSA3 detected a meteor. As of right now, there is a good chance that it is clear enough for night 82 to produce a few meteors. Tomorrow night will be iffy as a storm, our first in 2 months, is forecast to bring rain and clouds to the area. Will the streak survive? We’ll have to wait and see.
Obs Date(UT) Time TOT SPO ANT GEM HYD PUP DAD DLM MON COM SAL3 2010-12-15 12h 10m 53 20 5 20 1 1 1 1 2 2 ALLS 2010-12-15 12h 38m 40 15 4 11 3 0 1 3 1 2 HERM 2010-12-15 11h 50m 28 15 2 10 0 1 - - - 0 VISM 2010-12-15 02h 00m 37 0 1 28 3 1 - - 1 3 (LM = +5.7 to +6.0) SAL3 - SALSA3 camera in Tucson (Carl Hergenrother) ALLS - Near all-sky camera in Tucson (Carl Hergenrother) VIST - Visual observations from Tucson (Carl Hergenrother) VISH - Visual observations from Hermosillo (Salvador Aguirre) HERM - PARENI camera in Hermosillo (Salvador Aguirre) SDG - Camera in San Diego operated by Bob Lunsford Time - Total amount of time each camera looked for meteors TOT - Total number of meteors detected SPO - Sporadics (meteors not affiliated with any particular meteor shower) ANT - Antihelions GEM - Geminids HYD - Sigma Hydrids PUP - Puppids-Vellids DAD - December Alpha Draconids DLM - December Leonis Minorids MON - Monocerotids