Comet PANSTARRS now fading

Comet C/2011 L4 (PANSTARRS) peaked between magnitude +1.0 and +2.0 in the days after its March 10th perihelion. Since then the comet has moved away from the Sun and Earth is now located 0.57 AU from the Sun (versus 0.30 AU at perihelion) and 1.23 AU from Earth (versus 1.10 AU on March 5).

The comet is still a difficult object to observe since it located low in the northwestern sky during evening twilight. Adding to the difficulty is a nearly Full Moon and the fact that the comet has now faded to magnitude +3.0 to +3.5. That’s 4-6 times fainter than it was two weeks ago.

The image below was taken from my backyard near Tucson with a Canon 50mm F/1.4 lens, Hoya X1 (Green) filter and a Imaging Source DMK41 camera. It is a composite of 19 2-second exposures. As you can see by the trees, the comet was already quite low at an elevation of ~5 degrees above the horizon.

The image is also close to what the comet looked like in 7×50 binoculars. Close but not quite… I’d say the comet was looked a little fainter in the binoculars versus the image.

C2011L4_2013Mar24_50mm

Meteor Activity Outlook for March 23-29, 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 full phase on Wednesday March 27th. At this time the moon is located opposite the sun and will be above the horizon the entire night. This weekend the waxing gibbous moon will set during the late morning hours, allowing a short period of dark skies between moon set and the start of morning twilight. The estimated total hourly meteor rates for evening observers this week is near two as seen from the northern hemisphere and three as seen from south of the equator. For morning observers the estimated total hourly rates should be near five from the mid-northern hemisphere and seven 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. Rates are reduced during this period due to interfering 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 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 large Anthelion (ANT) radiant is currently located at 13:04 (196) -07. This position lies in central Virgo, five degrees northwest of the first magnitude star Spica (Alpha Virginis). These meteors may be seen all night long but the radiant is best placed near 0200 Local Daylight Time (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.

IMO #49 is an unnamed shower active between March 22 and April 7. The radiant is currently located at 19:28 (292) +42. This position lies on the Lyra-Cygnus border, directly between the bright stars Vega and Deneb. Rates are expected to be exceedingly low this week no matter your location. Your best chance to catch this activity would be near April 3rd when it briefly becomes the strongest radiant in the sky. The radiant is best placed in a dark sky just before dawn. At 45km/sec. this shower would produce meteors of medium velocity.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately three 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 five per hour as seen from rural observing sites and two per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Rates are reduced during this period 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) – 113:04 (196) -07   Velocity – 30km/sec.
Northern Hemisphere – 2 per hr.   Southern Hemisphere – 2 per hr

IMO #49  – 19:28 (292) +42   Velocity – 45km/sec.
Northern Hemisphere – <1 per hr.   Southern Hemisphere – <1 per hr

Clear Skies!
Robert Lunsford
American Meteor Society

Comet PANSTARRS dazzles in the evening sky

Comet PANSTARRS is putting on a nice show in the evening sky. Even though it is located low in the west and is definitely affected by the brightness of the twilight sky, many observers have been able to spot it with the naked eye and small binoculars. My magnitude estimates place the comet around magnitude +1.5. This agrees with estimates made by other observers from around the world.

Here in Tucson, I first saw the comet on Sunday night. Though I first spotted it in 10×50 binoculars I was able to see it, with difficulty, with the naked eye. On Tuesday and Wednesday evening, the comet was much easier to see. Here in Tucson we are blessed with dry, clear skies so I the comet was relatively easy to spot with the naked eye.

On Tuesday night, a thin crescent Moon was located only a few degrees to the right of the comet. Salvador Aguirre of Hermosillo, Sonora, Mexico imaged the pair. His image comes very close to matching what the comet and Moon looked like to the naked eye. Note that the comet really only looks like a faint star with a hint of a tail. And this is under dry clear Sonoran skies. Anyone observing from locations with any amount of humidity and/or smog will have a much harder time to see the comet. This is why binoculars are a must for finding and enjoying the comet.

Salvador_C2011L4
Image of Comet C/2011 L4 (PANSTARRS) and the crescent Moon on the evening of March 12 from Hermosillo, Sonora, Mexico. Credit: Salvador Aguirre.

 

The following image was taken on the same night as Salvador’s by Bob Lunsford from Chula Vista, CA. This view closely matches what the comet looks like in small binoculars.

 

Lunsford_C2011L4_moon_2013mar13_crop
Image of Comet C/2011 L4 (PANSTARRS) and the crescent Moon on the evening of March 12 from Chula Vista, CA, USA. Credit: Bob Lunsford.

 

The view of the comet gets better in a telescope. Salvador also acquired a movie of the comet as it set through his telescope.

 

 

I was able to get a few images of the comet through my 12″ dobsonian. Unfortunately the telescope doesn’t have a tracking mount so I had to obtain a hundred or so very short exposures and co-add them.

 

2013mar13_C2011L4_12inch

 

The comet is slowly moving higher in the sky every night. This should make the comet easier to see though the comet will also start to fade as it moves away from the Sun. Also the Moon will start to become a problem as it gets brighter. For those who want to observe the comet please see Bob King’s finder charts at his Astro Bon blog.

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.

close-comet
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.
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.
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.