Oct 25/26/27/28 Meteors

In the last ‘Meteor’ post, I was all excited about getting a clear night (Oct 25/26) to catch some Orionids. I guess I spoke too soon. Even though there were no obvious clouds in all of AZ on the IR satellite image, there were clouds over Tucson. I’ve seen this before where the entire state is clear but the Tucson valley forms a cap of clouds. Luckily, the conditions have gotten better and last night (Oct 27/28) was crystal clear.

Last night marked the 33rd straight night with a meteor detection. Sure, one of those nights consisted of a single meteor between the clouds but it is still an impressive run. With no storms in the forecast, the streak still has a way to go.

The Orionids are on the downswing but still make up half of the detected meteors. This is true on both the near all-sky fireball camera as well as the deeper, smaller FOV camera. Unfortunately the Moon is still an issue for visual observers. Currently it is sitting right on top of the Orionid radiant (as well as on top of Comet Hartley 2).

Speaking of Comet Hartley 2, the possibility of seeing ‘Hartley-ids’ next week has made the mainstream news. A NASA Science News story suggests that two bright fireballs, with an apparent common origin seen on Oct. 16 from Western Ontario and Alabama, might be from Hartley 2. With Earth making its closest approach to Hartley 2′s orbit on Nov 2/3, any shower related to Hartley 2 will appear to radiate from Cygnus.

Though the current orbit of Hartley 2 does come within 0.068 AU of Earth and in the past it came even closer (~0.03 AU) that really is not close enough to expect any meteors. Most of the showers we see come much closer to Earth’s orbit. Peter Jennsiken’s book ‘Meteors and Their Parent Comets’ does show that Hartley 2 may produce ‘Hartley-ids’ staring in the 2050/2060 time frame. Even with a very low probability of any ‘Hartley-ids’ this year the IMO video network of cameras will be up and running. If there are any Hartley-ids (actually the shower will probably be named ‘???? Cygnids’ after a bright star nearest to the radiant) we should catch them.

Obs  Date(UT)      Time    TOT SPO NTA STA ORI EGE LMI OUI ETT BCN
SAL3 2010-10-28   07h 12m   35  12  2   2   17  1   0   1   0   0
ALLS 2010-10-28   11h 48m   18  6   1   0   9   1   1   0   0   0
SAL3 2010-10-27   06h 40m   40  12  2   6   11  1   2   0   2   4
ALLS 2010-10-27   11h 41m   19  7   1   0   10  1   0   0   0   0
SAL3 2010-10-26   04h 31m   18  4   1   0   11  0   0   0   1   1
ALLS 2010-10-26   04h 39m   13  4   0   0   6   0   0   1   1   1

SAL3 - SALSA3 camera in Tucson (Carl Hergenrother)
ALLS - Near all-sky camera in Tucson (Carl Hergenrother)
VIST - Visual observations from Tucson (Carl Hergenrother)
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  
NTA - Northern Taurids
STA - Southern Taurids 
ORI - Orionids
EGE - Epsilon Geminids
LMI - Leonis Minorids
OUI - October Ursa Minorids
ETT - Eta Taurids
BCN - Beta Cancrids

Recent Discoveries – Oct 19 to 28

The past week saw only a few new asteroid discoveries. Due to bright sky conditions caused by the nearly Full Moon, most of the surveys go on hiatus for a few days. Now that the Moon is well past Full, discoveries are ramping up again.

Asteroid   Type   Mag    MOID     a     e     i     H   Discoverer      MPEC
2010 UC7   Apollo  18   0.004   1.89  0.57   5.2  24.6  Catalina        2010-U48
2010 UB7   Amor    19   0.243   2.46  0.50  11.2  21.9  Catalina        2010-U47
2010 UA7   Amor    20   0.173   2.41  0.51   3.7  23.3  Mount Lemmon    2010-U46
2010 UZ6   Amor    20   0.034   2.54  0.60   6.3  26.4  Mount Lemmon    2010-U45
2010 UY6   Amor    20   0.059   2.70  0.62  20.1  20.3  WISE            2010-U44
2010 UX6   Apollo  18   0.021   2.55  0.61   1.3  23.1  La Sagra        2010-U43
2010 UP    Apollo  18   0.017   1.07  0.10   9.3  24.5  LINEAR          2010-U27
2010 UO    Apollo  19   0.029   1.41  0.28   5.5  26.2  Mount Lemmon    2010-U26
2010 UM    Amor    20   0.203   1.94  0.38   3.9  21.7  Mount Lemmon    2010-U22
2010 TX168 Apollo  19   0.021   1.48  0.52  25.9  19.8  Catalina        2010-U25 

Comet       Type       T        q     a     e      i  Mag  Period        MPEC 
None

Type
Aten -  Earth crossing with semi-major axis (avg distance from Sun) < 1 AU
Apollo - Earth crossing with semi-major axis (avg distance from Sun) > 1 AU
Amor - non-Earth crossing with perihelion distance < 1.3 AU
JFC - Jupiter family comet
HFC - Halley family comet
LPC - Long-period comet
MBC - Main belt comet
ECC - Suspected extinct or dormant (or just unrecognized) comet
T - Date of Perihelion
MOID - Minimum Orbit Intercept Distance, minimum distance between asteroid and Earth's orbit
a - semi-major axis, average distance from Sun in AU (1 AU = 93 million miles)
e - eccentricity
i - inclination
H - absolute magnitude
Mag - magnitude at discovery
Discoverer - survey or person who discovered the object
MPEC - Minor Planet Electronic Circular, the discovery announcement

Oct 23/24/25 Meteors

Oct 23/24 finally brought a clear night… well at least one with only a little cirrus. The next night was back to fighting with lots of bright moonlit cirrus.

The Orionids are still going strong. Unfortunately my rates are down big time due to the aforementioned clouds and moonlight. Visual reports to the IMO show that after a 4 day plateau with ZHR rates of 35-40 per hour, rates are now in decline. It will be interesting to see how the video rates turn out since southern AZ finally has a night with no clouds.

Obs  Date(UT)      Time    TOT SPO NTA STA ORI EGE LMI SSA OUI ETT BCN
SAL3 2010-10-25   07h 05m   30  9   1   2   15  2   0   -   0   1   0
ALLS 2010-10-25   09h 03m   27  3   1   1   18  2   1   -   0   1   0
SAL3 2010-10-24   10h 25m   46  14  2   1   25  2   1   0   0   1   -
ALLS 2010-10-24   10h 38m   48  2   3   1   32  6   0   3   0   1   -

SAL3 - SALSA3 camera in Tucson (Carl Hergenrother)
ALLS - Near all-sky camera in Tucson (Carl Hergenrother)
VIST - Visual observations from Tucson (Carl Hergenrother)
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  
NTA - Northern Taurids
STA - Southern Taurids 
ORI - Orionids
EGE - Epsilon Geminids
LMI - Leonis Minorids
SSA - Sigma Arietids
OUI - October Ursa Minorids
ETT - Eta Taurids
BCN - Beta Cancrids

Oct 19/20 to 22/23 Meteors

The night of October 21/22 marked the peak of this year’s Orionids shower. For observers around the world the display was hampered by a Full Moon which never left the night sky. Here in Tucson, the sky was mostly cloudy as a cut-off low brought some light rain. Still, there were enough clear patches to count quite a few meteors.

Visual reports submitted to the International Meteor Organization suggest a peak ZHR of ~40-50 per hour. Of course, ZHR rates are only observed under perfectly dark conditions. With the nearly Full Moon and the usual issue of light polluted skies, the actual observed rate was much lower.

Obs  Date(UT)      Time    TOT SPO NTA STA ORI EGE LMI OCU SSA OUI
SAL3 2010-10-23   04h 47m   26  5   0   2   18  1   0   -   0   0
ALLS 2010-10-23   11h 17m   25  5   2   0   15  3   0   -   -   -
SAL3 2010-10-22   03h 38m   9   2   1   0   5   0   0   -   0   1
ALLS 2010-10-22   04h 47m   19  6   0   0   13  0   0   -   -   -
SAL3 2010-10-21   02h 05m   11  0   0   0   8   2   0   0   1   0
SAL3 2010-10-20   04h 46m   35  9   1   2   20  1   0   1   0   1
ALLS 2010-10-20   04h 23m   16  3   1   0   9   2   1   -   -   -

SAL3 - SALSA3 camera in Tucson (Carl Hergenrother)
ALLS - Near all-sky camera in Tucson (Carl Hergenrother)
VIST - Visual observations from Tucson (Carl Hergenrother)
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  
NTA - Northern Taurids
STA - Southern Taurids 
ORI - Orionids
EGE - Epsilon Geminids
LMI - Leonis Minorids
OCU - October Ursa Majorids
SSA - Sigma Arietids
OUI - October Ursa Minorids

Meteor Activity Outlook for October 23-29, 2010

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.

Meteor activity in general increases in October when compared to September. A major shower (the Orionids) is active most of the month along with several minor showers. Both branches of the Taurids become more active as the month progresses, providing slow, graceful meteors to the nighttime scene. The Orionids are usually the big story of the month but this year the Orionid peak coincides with the full moon, which will severely reduce the number of meteors seen. Orionid activity can be seen before and after maximum when the moon is not so troublesome. Unfortunately on these nights the Orionid rates will be low, most likely less than five per hour.

During this period the moon is full on the 23rd and wanes toward last quarter, which is reached on the 30th. The bright moon will make observing meteors difficult as only the brightest ones can be seen in the lunar glare. Those viewing under transparent skies will have better success as the moonlight will be less scattered. The estimated total hourly rates for evening observers this week is near four from the northern hemisphere and two for observers south of the equator. For morning observers the estimated total hourly rates should be near twelve from the northern hemisphere and nine 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 this week due to lunar interference.

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 October 23/24. 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
OUI October Ursa Minorids 18h 12m  +74    28    <1    <1
NTA Northern Taurids      02h 52m  +20    29     1    <1
STA Southern Taurids      02h 32m  +11    30     2     2
ETT Eta Taurids           04h 00m  +24    47    <1    <1
ORI Orionids              06h 32m  +16    67     5     5
EGE Epsilon Geminids      07h 04m  +27    70    <1    <1
BCN Beta Cancrids         07h 12m  -03    65    <1    <1
LMI Leonis Minorids       10h 48m  +36    60    <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

Latest on Comet Hartley 2

Just a quick update on the status of Comet 103P/Hartley 2. This is the 3rd update on 103P (1st update on Sep.22 and 2nd update on Oct. 8). Up-to-date lightcurves and images will also be posted on a special page devoted to 103P. The 103P page can be located with the 103P tab at the top of the blog or by going here.

Summary

Comet 103P/Hartley 2 is currently in the middle of Auriga moving to the southeast at a little over 3° per day. With closest approach to Earth on Oct. 20 (0.121 AU) and closest approach to the Sun on Oct. 28 (1.059 AU), the comet is as big and bright as it will probably get for this return. Unfortunately, the bright Full Moon will make observing the comet difficult for the next week and a half. By the beginning of November the Moon will be out of the morning sky and the comet will be easily visible once again. At that time the comet should still be a large 4th magnitude fuzzball as it moves through Gemini. It should fade to magnitude ~6.0 by the end of November and magnitude 7.5 to 8.0 by the end of the year.

Finder charts can be found at Sky and Telescope.

Analysis

In the previous updates, there was concern that Comet Hartley 2 was not as bright as predicted. We have good data from the 1991 and 1997 returns which suggested that the comet’s 2010 return was running at least a magnitude fainter. There was also a question as to whether this was due to change in the intrinsic brightness of the comet or to difficulty in measuring the brightness of such a large object.

Based on the recent data (up to Oct 18), the apparent ‘faintness’ of the comet has more to do with measuring a large, low surface brightness coma than any intrinsic fading. 103P’s coma is LARGE. My most recent CCD images from Oct. 17 (see image further below) shows a coma over 70′ across (~1.2°). Other CCD observers such as Francois Kugel of France have reported coma measurements of 1° or larger. For comparison, the Moon’s average apparent diameter is 31′ so the comet appears ~2.3 times larger than the Moon. Only observers at very dark sites (lm of 6.5 or fainter) will be able to see the full extent of the coma with the naked eye or even optical aid. As a result, many visual observers (myself included) are not seeing the entire coma and have been underestimating the brightness of Hartley 2.

The brightest visual magnitude estimates are in the 4.5 to 5.0 range. Juan José González has consistently found the comet to be magnitude 5.0 or brighter over the past 2 weeks from extremely dark sites in northern Spain. My own CCD measurement from Oct. 17 was magnitude 4.6 so it’s probably safe to say the comet is currently a 4th magnitude object. If it brightens and fades at the same rate as it did in 1991 and 1997 then the comet is currently near its brightest and we can only expect another 0.1 to 0.2 magnitude brightening before perihelion. Unfortunately with the Moon now dominating the morning sky, the comet may actually appear fainter as bright moonlight washes out much of the coma.

The three lightcurves below are updates of the ones from my previous posts. Nothing has changed except for the addition of recent data (valid to Oct 18).

Lightcurve 1 : Apparent magnitude of Comet 103P versus time from perihelion. For comparison, the expected brightness of the comet (based on observations from the 1997 return) is also plotted (dashed line). Visual magnitude estimates (red circles) are from the ICQ, CometObs and COBS while the CCD measurements (blue diamonds) are by Carl Hergenrother.

Lightcurve 2 : Heliocentric magnitude of Comet 103P versus time from perihelion. Magnitudes are normalized to a distance of 1 AU from Earth and Sun and to o° phase angle. For comparison, visual magnitude observations from the 1991 return (dark grey boxes) and 1997 return (light grey circles) are also plotted. Visual magnitude estimates (red circles) are from the ICQ, CometObs and COBS while the CCD measurements (blue diamonds) are by Carl Hergenrother.

Lightcurve 3 : Heliocentric magnitude of Comet 103P versus heliocentric distance. Magnitudes are normalized to a distance of 1 AU from Earth and Sun and to o° phase angle. For comparison, visual magnitude observations from the 1991 return (dark grey boxes) and 1997 return (light grey circles) are also plotted. Visual magnitude estimates (red circles) are from the ICQ, CometObs and COBS while the CCD measurements (blue diamonds) are by Carl Hergenrother.

Closest approach to Earth occurred on Oct. 20 at 0.121 AU (11.25 million miles / 18 million km / ~48 lunar distances). The image below was taken a few nights earlier on Oct. 17 with a 10.6-cm refractor operated by Global-Rent-a-Scopes in New Mexico. Due to the rapid motion of the comet I was able to do a median combine on the 13 60-sec exposures and remove most of the stars. The remaining stellar signal can be seen as short fuzzy streaks. When the contrast is stretched the coma extends to a diameter of 71′. At the time the image was taken, the comet was 0.123 AU from Earth. Using these 2 bits of information we can determine the actual size of the coma at ~236,000 miles or ~378,000 km across which is roughly the distance from Earth to the Moon. Though large, the coma is mostly empty space filled with a scattering of cometary dust and gas. The nucleus responsible for producing all of this dust and gas is much, much smaller. At only ~1.2 km across, the nucleus is swamped by the glow of the coma and is not directly visible at this time (at least not at visible wavelengths, it could be directly observed at IR wavelengths).

The image (as well as those by others) shows a faint dust tail extending to the west-south-west. On the Oct. 17 image its length was just under 1°. Based on images from the 1991 return I’m surprised that we haven’t seen evidence of a long, narrow gas tail yet. [Added later: After reading Nicolas Biver’s recent posting on comets-ml, I’m of the opinion that the tail in my images is the ion tail. According to his calculations, the ion tail should be in a position angle (PA) of ~245° while the dust tail is at a PA of ~296°. The tail in the Oct. 17 image has a PA of 245° so it is an ion tail. It will be interesting to see if this tail lengthens in the coming weeks. Also to watch is the appearance of a dust trail as we pass through the orbit plane in early November.)

The next image was taken with a single-shot color CCD. The image only shows the inner coma of the comet but does a good job of representing the color and appearance of the comet in small telescopes.

First Half of October Meteors

This week’s main event, meteor-wise, is the maximum of the Orionids. These meteors were produced by Comet Halley over 2000-3000 years ago and would put on quite a show if, and there’s usually an if, it weren’t for the Full Moon spoiling the view. The Orionids have a broad maximum that may last up to 5 days. This year high rates are expected from October 20 to 25 with the peak occurring on the 22nd. This year also sees a few dust trail encounters (1266 BC trail on Oct. 21 9hrs UT and 911 BC on Oct. 25 4hrs UT).

Though ZHR rates of 40-50 per hour are expected the bright moonlight will make actual visible rates much lower, probably in the 10-20 per hour range.

Obs  Date(UT)      Time    TOT SPO DAU NTA STA ORI OCA GIA TUM EGE LMI 
SAL3 2010-10-19   05h 28m   53  15  -   1   2   32  -   -   -   3   0
ALLS 2010-10-19   03h 43m   24  2   -   0   1   17  -   -   -   2   2
SAL3 2010-10-18   03h 53m   15  8   -   0   1   6   -   -   0   0   
ALLS 2010-10-18   04h 10m   14  9   -   0   1   4   -   -   0   0
SAL3 2010-10-17   06h 28m   44  22  -   0   5   11  -   -   2   1
SAL3 2010-10-16   00h 49m   3   1   -   0   2   0   -   -   0   0
SAL3 2010-10-15   02h 09m   6   2   -   0   1   2   -   -   0   1
SAL3 2010-10-14   09h 20m   34  21  -   2   4   6   -   -   0   1
SAL3 2010-10-13   10h 42m   38  23  -   1   8   3   -   -   1   2
SAL3 2010-10-12   10h 51m   20  14  -   2   1   3   -   -   0
SAL3 2010-10-11   10h 50m   34  27  -   2   3   2   -   -
SAL3 2010-10-10   10h 47m   39  24  2   1   2   7   -   3
SAL3 2010-10-09   10h 34m   40  29  1   1   5   4   -   0
SAL3 2010-10-08   10h 38m   36  22  2   2   4   6   -   0
SAL3 2010-10-07   10h 42m   29  24  2   1   1   0   1   0
SAL3 2010-10-06   01h 02m   4   2   2   0   0   0   0   0
SAL3 2010-10-05   04h 25m   9   6   0   0   3   0   0
SAL3 2010-10-04   01h 22m   1   1   0   0   0   0  
SAL3 2010-10-03   04h 29m   22  19  2   0   0   1
SAL3 2010-10-02   10h 21m   24  20  1   1   1   1
SAL3 2010-10-01   07h 15m   28  23  1   2   2   -

SAL3 - SALSA3 camera in Tucson (Carl Hergenrother)
ALLS - Near all-sky camera in Tucson (Carl Hergenrother)
VIST - Visual observations from Tucson (Carl Hergenrother)
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  
DAU - Delta Aurigids
NTA - Northern Taurids
STA - Southern Taurids 
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