Comet PANSTARRS naked eye from Tucson

This evening I was successful in visually seeing Comet C/2011 L4 (PANSTARRS) for the first time. Though not an easy object to see I was consistently able to observe it with the naked eye after ~7:00 pm when the comet had already descended to an elevation of ~4-6 degrees above the horizon.

The comet was much easier to see in 10×50 and 30×125 binoculars. Though the comet appeared as nothing more than a faint star to the unaided eye, its yellow color and 0.3-0.4 degree long tail were very obvious in the binoculars.

Due to the bright sky and lack of bright stars near the comet it was difficult to estimate the brightness of the comet. Using a few stars that were much higher in the sky and atmospheric extinction tables produced by Dan Green at the International Comet Quarterly, I estimated the comet to be magnitude +1.5.

Now that I’ve seen the comet, I can recommend that anyone attempting to see the comet for themselves needs the following: 1) a very clear horizon free of any obstructions, 2) binoculars and 3) plan your observations in advance to pinpoint exactly where the comet will be in the sky. For #3 I noted the point on the horizon where the Sun set and then determined that the comet would be located near the same azimuth of the location of sunset. Then it was just a matter of time (over 30 minutes after sunset) till the sky darkened enough for the comet to appear.

Bob King has a nice collection of finder charts that will help in locating the comet over the next few weeks. Finding the comet will be a little easier on Tuesday evening because a very thin crescent Moon will be located only a few degrees to the right of the comet.

Happy Perihelion Day, Comet PANSTARRS!

Today (March 10) at 4 hours UT (or GMT) comet C/2011 L4 (PANSTARRS) reached perihelion, or the point in its orbit when it is closest to the Sun. The time of perihelion passage corresponds with 9 pm on the night of March 9 for Tucson (MST -7 hours). At that time PANSTARRS was located at a distance of 0.302 AU from the Sun (28.0 million miles or 45.1 million km) which is ~3.3 times closer to the Sun than the Earth’s average distance and about 1 million km closer to the Sun than Mercury gets. On March 5 it also came as close to the Earth as it will get, a rather distant 1.097 AU (102.0 million miles or 164.1 million km). This is 10% further than the distance between the Earth and Sun.

As the comet rounds the Sun it is quickly heading north. After months of being only visible from south of the Equator, those of us up north will have the comet to ourselves starting this week. Already observers as far north as New Jersey (latitude 40°) have reported seeing the comet. Here in Tucson I tried to find the comet last week but it was still too deep in the bright twilight to see. Now that a recent bout of rain and clouds has moved through I will try again this evening.

The video below by Jay Lawson from Sparks, Nevada (latitude 39.5°) shows what the comet looks like in a small telescope or pair of binoculars (note the video is in black and white so it doesn’t show the true color of the comet and sky).

Another video from Brisbane, Australia back on Feb. 23 gives a good idea of what the comet will look like to naked eye observers. Please note that even though the comet is a very bright magnitude 1.5 and this does place it among some of the brighter comets of the past, it is not an easy object to see. If it were located high up in the night sky it would be unmistakable with a tail many degrees long to the naked eye. Such a well placed comet would even be visible under bright city lights. But Comet PANSTARRS is not located up high in a dark sky but rather close to the horizon against a bright twilight sky. By the time the sky is dark the comet will either have set or will be only a few degrees above the horizon.

Bob King has a great post about PANSTARRS on his blog Astro Bob. He highlights one of the problems of spotting a comet so close to the horizon, especially one in the western sky near the just set Sun. Many reports of PANSTARRS have actually been of distant aircraft contrails. His posting shows the different appearances of the comet versus plane contrails.

Bob also has a nice post with finder charts for locating the comet over the next few weeks.

Meteor Activity Outlook for March 9-15, 2013

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

As seen from the northern hemisphere, March is the slowest month for meteor activity. No major annual showers are active and only a few very weak minor showers produce activity this month. The sporadic rates are also near their annual minimum so there is not much to look forward to this month except for the evening fireballs that seem to peak this time of year from the northern hemisphere. This could be due to the fact the Antapex radiant lies highest above the horizon this time of year during the evening hours. From the southern hemisphere, activity from the Centaurid complex begins to wane with only the weak activity visible from Norma and perhaps others areas nearby. At least southern sporadic rates are still strong to make the late summer viewing a bit more pleasurable.

During this period the moon reaches its new phase on Monday March 11th. At this time the moon is located near the sun and cannot be seen at night. Late in this period the waxing crescent moon will enter the evening sky but will not interfere with meteor observing whatsoever. The estimated total hourly meteor rates for evening observers this week is near two as seen from the northern hemisphere and five as seen from south of the equator. For morning observers the estimated total hourly rates should be near eight from the mid-northern hemisphere and eighteen from the mid-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.

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 March 9/10. 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:

On the last day of this period, members of the Northern March Virginids (NVI) should become visible as this shower peaks on the first day of its activity. The radiant is expected to be located at 11:34 (174) +09. This position is located near the Leo-Virgo border between the faint stars Iota Leonis and Nu Virginis. These meteors are best seen near 0100 local daylight time (LDT) when the radiant lies highest above the horizon. Rates would mostly likely be less than one shower member per hour, no matter your location. Since this radiant is located near the celestial equator, this activity can be seen most everywhere. At 22 km/sec. these meteors would have a slow velocity.

The large Anthelion (ANT) radiant is currently centered at 12:08 (182) -02. This position lies in western Virgo, two degrees southwest of the fourth magnitude star Zaniah (Eta Virginis). These meteors may be seen all night long but the radiant is best placed near 0200 LDT when it lies on the meridian and is highest in the sky. Rates at this time should be near two per hour no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.

The Gamma Normids (GNO) are active from a radiant located at 15:40 (235) -50. This position lies in western Norma, five degrees northeast of the third magnitude star Zeta Lupi. Due to the southerly declination (celestial latitude) these meteors cannot be seen north of the northern tropical regions. They are best seen from mid-southern latitudes where the radiant lies high in the sky near 0500 local summer time. This shower peaks on March 13 so current hourly rates would be near two per hour as seen from south of the equator and less than one per hour as seen from northern latitudes. At 56km/sec. the Gamma Normids would produce mostly swift meteors.

On Monday March 11, activity from the Xi Herculids (XHE) should become detectable. The peak occurs on Wednesday March 13th when the radiant is located at 17:11 (258) +48. This position is located in northern Hercules, five degrees southwest of the third magnitude star Rastaban (Beta Draconis). These meteors are best seen near during the last dark hour before dawn when the radiant lies highest above the horizon in a dark sky. Rates should be near one shower member per hour as seen from the northern hemisphere. These meteors are not well seen south of the equator as the radiant does not rise very high from points south of the equator. At 37 km/sec. these meteors would have a medium velocity.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately five sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near one per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near fourteen per hour as seen from rural observing sites and four per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.

The list below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning .

Northern March Virginids (NVI) – 11:34 (174) +09   Velocity – 22km/sec.
Northern Hemisphere – <1 per hr.   Southern Hemisphere – <1 per hr

Anthelions (ANT) – 12:08 (182) -02   Velocity – 30km/sec.
Northern Hemisphere – 2 per hr.   Southern Hemisphere – 2 per hr

Gamma Normids (GNO) – 15:40 (235) -50   Velocity – 56km/sec.
Northern Hemisphere – <1 per hr.   Southern Hemisphere – 2 per hr

Xi Herculids (XHE) – 15:43 (236) +42  Velocity – 37km/sec.
Northern Hemisphere – 1 per hr.   Southern Hemisphere – <1 per hr

Clear Skies!
Robert Lunsford
American Meteor Society

Comet PANSTARRS heads north

Comet C/2011 L4 (PANSTARRS) has been thrilling observers in the southern hemisphere for the past few weeks as it approaches its March 10 perihelion at a distance of 0.30 AU from the Sun. Over the next week, the comet will travel north and become visible (though still a difficult sight) for those of us north of the Equator.

At discovery PANSTARRS appeared to be an intrinsically bright comet and many forecast that it would brighten to magnitude -1 or so. But as is common for dynamically new comets making their first trip through the inner Solar System, PANSTARRS’ rate of brightening slowed down. With the comet as close to the Sun and Earth as it will get it should not brighten further. Still at magnitude +1.5 it ranks as one of the brighter comets of recent times.

The image below shows PANSTARRS in at its current best. The image is interesting in that it shows us a lot about this particular comet. First off, it is a brilliant yellow. Being a dust-rich comet, the dust it has released does a very good job of reflecting the light of the Sun, hence the yellow color. Its yellowness is also enhanced by the excitation of sodium atoms in the comet’s dust. This is especially true for comets that have perihelia at small heliocentric distances.

The other thing to notice in the image below is that PANSTARRS has three separate tails. The most obvious is the broad dust tail extending towards 11:30am position from the head of the comet. This tail is composed of dust released by the comet over the past few weeks. The narrower dust tail extending towards the 9:30 am direction is composed of larger dust particles that were released by the comet over the past few years. It is very possible that some of this larger dust may even have been released before the comet was discovered when it was located 10-20 AU from the Sun and activity was driven by highly volatile ices. The third tail is the hardest to see. It is easiest seen near the top of the image as a thin long tail just to the right of the main dust tail. This faint thin tail is the comet’s gas or ion tail. Its faintness is a clear indication that PANSTARRS is not a very gas-rich comet. Note, that the gas tail is usually bluish in color so it is not as easy to see in a bright (and blue) twilight sky compared to the yellow dust tails.

Comet PANSTARRS seen from Queenstown, New Zealand, on Mar. 2, 2013. Credit: spaceweather.com, Minoru Yoneto / AP .

.

Though observers down under have had the comet all to themselves the past few months, PANSTARRS is now rapidly moving north. Last night I tried to spot the comet during bright twilight with 10×50 binoculars here in Tucson with no luck (latitude 32°). Also Salvador Aguirre was unsuccessful in his naked eye attempts to spot the comet from Hermosillo, Mexico (latitude 29°). The northernmost observations that I know of is from Malaysia (as reported by Spaceweather.com) (latitude 5°).

The lack of northern observations should change rapidly. Luckily for us, the Moon will be well placed to point the way to the comet next week. On the evening of March 12, the comet will be located within 2 to 3° to the left of the Moon. Even then this will be a very difficult observation. A clear unobstructed view of the west horizon is a must as the two will be only a few degrees above the horizon. Also binoculars are highly recommended as even the Moon will be very difficult to find due to its thinness, faintness, low elevation and the brightness of the sky.

Over the next few weeks the comet will slowly appear higher in the sky though it may not be till early to mid-April till we see a nice view of the comet in a dark sky. By that time the comet will have faded to a faint naked eye object (for folks under dark skies, city folks will likely have to rely on binoculars to spot the comet by then). The finder chart below was produced by Bob King (‘Astro Bob’).

Comet L4 PANSTARRS keeps low to the horizon when its brightest from early to mid-March. The map shows the comet’s position and approximate tail direction each night from March 7-25 about 30 minutes after sunset from the mid-section of the U.S. (around latitude 42 degrees N). Created by Bob King with Chris Marriott’s SkyMap software.

.

As impressive as the comet appeared in the first image above, to the naked eye it should look more like the image below.

Comet C/2011 L4 PANSTARRS as seen from Mount Dale, Western Australia. The lights on the distant horizon are from the city of Armadale, which is southeast of Perth. Image credit: Astronomy Education Services/Gingin Observatory.

Meteor Activity Outlook for March 2-8, 2013

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

As seen from the northern hemisphere, March is the slowest month for meteor activity. No major annual showers are active and only a few very weak minor showers produce activity this month. The sporadic rates are also near their annual minimum so there is not much to look forward to this month except for the evening fireballs that seem to peak this time of year from the northern hemisphere. This could be due to the fact the Antapex radiant lies highest above the horizon this time of year during the evening hours. From the southern hemisphere, activity from the Centaurid complex begins to wane with only the weak activity visible from Norma and perhaps others areas nearby. At least southern sporadic rates are still strong to make the late summer viewing a bit more pleasurable.

During this period the moon reaches its last quarter phase on Monday March 4th. At this time the moon is located ninety degrees west of the sun and rises near midnight local standard time (LST) as seen from mid-northern latitudes. This weekend the slightly gibbous moon will be a major nuisance unless you have extremely transparent skies which will allow you to see faint meteors. As the week progresses the waning crescent moon will rise later each morning, allowing a little more viewing time under dark skies. The estimated total hourly meteor rates for evening observers this week is near two as seen from the northern hemisphere and four as seen from south of the equator. For morning observers the estimated total hourly rates should be near six from the mid-northern hemisphere and thirteen from the mid-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. Morning 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 March 2/3. 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 large Anthelion (ANT) radiant is currently centered at 11:40 (175) +01. This position lies in western Virgo, two degrees west of the fourth magnitude star Zavijava (Beta Virginis). These meteors may be seen all night long but the radiant is best placed near 0100 LST when it lies on the meridian and is highest in the sky. Rates at this time should be near two per hour no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.

The Gamma Normids (GNO) are active from a radiant located at 15:12 (228) -51. This position lies in southeastern Lupus, two degrees north of the third magnitude star Zeta Lupi.  Due to the southerly declination (celestial latitude) these meteors cannot be seen north of the northern tropical regions. They are best seen from mid-southern latitudes where the radiant lies high in the sky near 0500 local summer time. This shower peaks on March 13 so current hourly rates would less than one no matter you location. At 56km/sec. the Gamma Normids would produce mostly swift meteors.

IMO shower #37 is active Tuesday March 5th through March 10th. Maximum activity is expected on the 5th from a radiant located at 15:43 (236) +42. This position is located in a extreme northeastern Bootes. The closest bright star is second magnitude Alphecca (Alpha Coronae Borealis), which lies fifteen degrees to the southwest. These meteors are best seen near during the last dark hour before dawn when the radiant lies highest above the horizon in a dark sky. Rates would mostly likely be less than one shower member per hour, no matter your location. Observers in the northern hemisphere have an advantage in that the radiant lies higher in the sky during the morning hours. At 42 km/sec. these meteors would have a medium velocity.

IMO shower #35 is active through Tuesday from a radiant located at 16:39 (250) +49. This position is located in a remote area of northwestern Hercules. The closest bright star is Eltanin (Gamma Draconis), which lies twenty degrees to the east.  Peak activity is expected on the morning of March 4th. These meteors are best seen near during the last dark hour before dawn when the radiant lies highest above the horizon in a dark sky. Rates would mostly likely be less than one shower member per hour, no matter your location. Observers in the northern hemisphere have an advantage in that the radiant lies higher in the sky during the morning hours. At 40 km/sec. these meteors would have a medium velocity.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately four sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near one per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near eleven per hour as seen from rural observing sites and three per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Rates are reduced during the morning hours due to moonlight.

The list below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning .

Anthelions (ANT) – 11:40 (175) +01   Velocity – 30km/sec.
Northern Hemisphere – 2 per hr. Southern Hemisphere – 2 per hr

Gamma Normids (GNO) – 15:12 (228) -51   Velocity – 56km/sec.
Northern Hemisphere – <1 per hr. Southern Hemisphere – <1 per hr

IMO #37 – 15:43 (236) +42   Velocity – 42km/sec.
Northern Hemisphere – <1 per hr. Southern Hemisphere – <1 per hr

IMO #35 – 16:39 (250) +49 Velocity – 40km/sec.
Northern Hemisphere – <1 per hr. Southern Hemisphere – <1 per hr

Clear Skies!
Robert Lunsford
American Meteor Society

In the Transient Sky – March 2013

March 2013 Highlights
* Comet C/2011 L4 (PANSTARRS) will be visible in the evening sky for northern observers at magnitude 1-2 though it will be very low on the horizon
* Comet C/2012 F6 (Lemmon) will be 4th-5th magnitude for SH observers
* Saturn rises before midnight
* Jupiter continues to dominate the evening sky
* Mercury starts a great morning apparition for southern observers (not so good for northerners)
Note: If anyone has pictures or observations of these objects/events and want to share them with my readers, send them to the Transient Sky at <transientsky1@yahoo.com>.

Planets

Evening Planets

Jupiter – The King of the Planets dominates the evening sky being visible nearly overhead at the end of evening twilight. Jupiter is now three months past opposition. It spends the month just north of the stars of the Hyades cluster in Taurus as it fades from magnitude -2.3 to -2.1.  The Moon pays Jupiter a visit on the evening of the 17th.

Saturn – Saturn is an early morning object rising around 11:00 am at the start of the month and 9pm by the end of the month.  All month Saturn glows at magnitude +0.2 between Virgo and Libra. The Moon passes close to Saturn on the morning of the 2nd.

Morning Planets

Mercury – Mercury starts the month too close to the Sun to be seen. By the last third of the month, the innermost planet is rapidly rising out of the morning twilight glow for southern observers. Up north, the view will be much poorer.

Venus and Mars – Both planets are too close to the Sun for easy observation this month. They will be back this summer, Venus in the evening sky and Mars in the morning sky.

Meteors

The year is usually split in 2 with January through June having low rates with few major showers while July through December have high rates with many major showers. Meteor activity is near its annual minimum this month.

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 March mornings, 5 or so Sporadic meteors can be observed per hour from a dark moonless sky. The rate is near an annual minimum this month.

Major Meteor Showers

None this month.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Info on many minor showers are 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 International Meteor Organization’s 2012 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

C/2011 L4 (PANSTARRS)

Last month Comet PANSTARRS looked on pace to peak around magnitude -1 near its March 10th perihelion. But over the past few weeks the comet has not been brightening as quickly as hoped. As a result it is likely that the comet will be much fainter than -1 at its peak brightness and more along the lines of 2nd to 4th magnitude. The comet will still be a nice sight especially in binoculars and telescopes.

The comet was first seen by the Hawaiian based PanSTARRS asteroid survey on June 6, 2011 at a large distance of 7.9 AU from the Sun. At perihelion it will approach within 0.30 AU of the Sun. The comet is a new Oort cloud comet meaning it is making its first passage through the inner Solar System. The fact that it is a new Oort cloud comet explains its failure to brighten as quickly as first predicted. These sort of comet often appear relatively bright when far from the Sun because they still contain a large amount of very volatile ices. As the comet approaches the Sun, these ices sublimate and the comet brightens at a slower rate.

Even though we are only 10 days from perihelion, the comet’s peak brightness is still uncertain. The comet should be a 1st or 2nd magnitude object as it rounds the Sun near mid-month. The comet also becomes visible again from the Northern Hemisphere around that time though it will never stray far from the western horizon during evening twilight. Its low elevation and the bright evening sky will make the comet a difficult sight.

Finder charts can be found at Chasing Comets.

Ephemeris for C/2011 L4 (PANSTARRS)
Date            RA        DEC    Delta   r   Elong    V
2013 Mar 01   23h 25m  -27d 18'  1.111 0.411   21    2.5
2013 Mar 11   00h 25m  -02d 52'  1.115 0.303   15    1.4
2013 Mar 21   00h 35m  +19d 43'  1.186 0.444   21    2.9
2013 Mar 31   00h 31m  +35d 14'  1.267 0.662   31    4.5

RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU
r = distance from the Sun in AU, Elong = elongation from Sun in degrees
V = Visual magnitude

C/2012 F6 (Lemmon)

Everyone was expecting C/2011 L4 (PANSTARRS) and C/2012 S1 (ISON) to be the two naked eye comets of 2013. No one was expecting C/2012 F6 (Lemmon) to be vying for the status of naked eye comet when it was discovered by Alex Gibbs of the Mount Lemmon survey back on March 23, 2012. At that time the comet was a faint 20th-21st magnitude and 5.0 AU from the Sun. It also appeared to be an intrinsically faint comet. So faint in fact that I though it had a good chance of disintegrating near perihelion. Instead the comet brightened at a rapid rate. Perihelion will occur on March 24, 2013 at a distance of 0.73 AU from the Sun.

Over the past few days visual observers have estimated the comet at magnitude 6.2 to 6.5.

The comet is too far south for most northern observers and the comet will continue to travel the southern sky this month. As a result, this comet will only be visible to southern observers till May.

Though the comet rapidly brightened for months after discovery, its rate of brightening has slowed down markedly. Observations at the end of February place it between magnitude 5.0 and 5.5. This month the comet should brighten some more up to magnitude ~4.7.

Finder charts can be found at Chasing Comets.

Ephemeris for C/2012 F6 (Lemmon)
Date            RA        DEC    Delta   r   Elong    V
2013 Mar 01   00h 04m  -51d 22'  1.167 0.867   46    4.9
2013 Mar 11   00h 08m  -39d 10'  1.301 0.780   36    4.7
2013 Mar 21   00h 09m  -29d 31'  1.430 0.735   28    4.7
2013 Mar 31   00h 10m  -18d 46'  1.538 0.743   23    4.9
RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU
r = distance from the Sun in AU, Elong = elongation from Sun in degrees
V = Visual magnitude

Binocular Comets (V = 6.0 – 8.0)

None

Small Telescope Comets (V = 8.0 – 10.0)

C/2011 F1 (LINEAR)

No one has seen this comet for a few months because it has been too close to the Sun. Still it should have been seen by now yet it is still AWOL. Perhaps as it moves further from the glare of the Sun, it will be more easily spotted.

The LINEAR near-Earth asteroid survey picked up this comet back on March 17, 2011 at 18th magnitude. It passed perihelion on January 8 of this year at 1.82 AU from the Sun.

It is yet another comet that can only be seen from the Southern Hemisphere this month as it moves from Sagittarius to Microscopium.

Finder charts can be found at Chasing Comets.

Ephemeris for C/2011 F1 (LINEAR)
Date            RA        DEC    Delta   r   Elong    V
2013 Mar 01   21h 18m  -40d 51'  2.607 1.935   38    10?
2013 Mar 11   21h 54m  -41d 55'  2.585 1.981   43    10?
2013 Mar 21   22h 29m  -42d 39'  2.570 2.034   47    10?
2013 Mar 31   23h 05m  -43d 03'  2.561 2.092   51    10?

RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU
r = distance from the Sun in AU, Elong = elongation from Sun in degrees
V = Visual magnitude

Meteor Activity Outlook for February 16-22, 2013

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

February offers the meteor observer in the northern hemisphere a couple of weak showers plus falling sporadic rates. This may not seem too exiting but you never know when surprises are in store. An errant earth-grazer from the Centaurid complex may shoot northward. Better yet, a bright fireball may light up the sky. February is the start of the fireball season, when an abundance of fireballs seem to occur. This lasts well into April and seems to occur mostly during the early evening hours.

Observers in the southern hemisphere are treated to the Alpha Centaurid peak on the 8th plus the entire Centaurid complex of radiants is active all month long. Sporadic rates also peak this month south of the equator this month adding to the celestial show.

During this period the moon reaches its first quarter phase on Sunday February 17th. At this time the moon is located ninety degrees east of the sun and sets near midnight local standard time (LST) as seen from mid-northern latitudes. As the week progresses the waxing gibbous moon will set during the early morning hours, allowing a few hours of dark skies between the time of moon set and the beginning of morning twilight. The estimated total hourly meteor rates for evening observers this week is near two as seen from the northern hemisphere and four as seen from south of the equator. For morning observers the estimated total hourly rates should be near eight from the mid-northern hemisphere and seventeen from the mid-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. Evening 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 February 16/17. 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 large Anthelion (ANT) radiant is currently centered at 10:44 (161) +07. This position lies in southern Leo, ten degrees southeast of the first magnitude star Regulus (Alpha Leonis). These meteors may be seen all night long but the radiant is best placed near 0100 LST when it lies on the meridian and is highest in the sky. Rates at this time should be near one per hour no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.

The Alpha Centaurids (ACE) are active from a radiant located at 14:43 (221) -62. This position lies in southeastern Centaurus, very close to the position occupied by the zero magnitude star Rigel Kentaurus (Alpha Centauri). These meteors cannot be seen north of the northern tropical regions. They are best seen from mid-southern latitudes where the radiant lies high in the sky near 0500 local summer time. This shower peaked on February 8th so current rates would be near one per hour as seen from the southern hemisphere. At 56km/sec. the Alpha Centaurids would produce mostly swift meteors.

The Beta Herculids are active through Tuesday from a radiant located at 15:52 (238) +28. This position is actually located in Corona Borealis, four degrees northeast of the second magnitude star Alphecca (Alpha Coronae Borealis). It is suggested that the observer be liberal with shower association as the actual radiant position is not well defined. These meteors are best seen near during the last dark hour before dawn when the radiant lies highest above the horizon in a dark sky. Rates would mostly likely be less than one shower member per hour, no matter your location. Observers in the northern hemisphere have an advantage in that the radiant lies higher in the sky during the morning hours. At 56 km/sec. the Beta Herculids would produce mostly swift meteors.

The IMO video list of radiants has several entries for the Delta Serpentids (DSE). On most nights of possible activity this shower is extremely weak, far less than the weak sporadic rate seen this time of year from the northern hemisphere. On the morning of the February 16th though, it becomes the second most active radiant in the sky. At that time the radiant is located at 16:37 (249) +09, which actually places it in among the stars of Ophiuchus. The nearest bright stars are fourth magnitude Kappa and Iota Ophiuchi, which lie six degrees to the east. This position is well seen from either side of the equator. These meteors are best seen near during the last dark hour before dawn when the radiant lies highest above the horizon in a dark sky. On other mornings rates for this shower are so weak that the chance of sporadic alignment is extremely high. At 57 km/sec. the Delta Serpentids would produce mostly swift meteors.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately six sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near one per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near fourteen per hour as seen from rural observing sites and three per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Rates are reduced during the evening hours due to moonlight.

The list below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning .

Anthelions (ANT) – 10:44 (161) +07   Velocity – 30km/sec.
Northern Hemisphere – 1 per hr.   Southern Hemisphere – 1 per hr

Alpha Centaurids (ACE) – 14:43 (221) -62   Velocity – 56km/sec.
Northern Hemisphere – <1 per hr.   Southern Hemisphere – 1 per hr

Beta Herculids (BHE) – 15:52 (238) +28   Velocity – 56km/sec.
Northern Hemisphere – <1 per hr.   Southern Hemisphere – <1 per hr

Delta Serpentids (DSE) – 16:37 (249) +09   Velocity – 57km/sec.
Northern Hemisphere – 1 per hr.   Southern Hemisphere – 1 per hr

Clear Skies!
Robert Lunsford
American Meteor Society