Skywatching Archives

November 27, 2013December 23, 2015 by David Dickinson

ISON Watch: A Post-Perihelion Viewing Guide

ISON: A 2013 pre-perihelion portrait. (Credit and copyright: Efrain Morales/Jaicoa observatory. Used with permission).

“ISON Lives!!!”

“ISON R.I.P…”

Those are just some of the possible headlines that we’ve wrestled with this week, as Comet C/2012 S1 ISON approaches perihelion tomorrow evening. It’s been a rollercoaster ride of a week, and this sungrazing comet promises to keep us guessing right up until the very end.

Comet ISON reaches perihelion on U.S. Thanksgiving Day Thursday, November 28^th at around 18:44 Universal Time/ 1:44 PM Eastern Standard Time. ISON will pass 1.2 million kilometres from the surface of the Sun, just over eight times farther than Comet C/2011 W3 Lovejoy did in 2011, and about 38 times closer to the Sun than Mercury reaches at perihelion.

Comet ISON as seen from Ottawa, Canada on the morning of November 20th. (Credit: Andrew Symes/@FailedProtostar).

Earth-based observers essentially lost sight of ISON in the dawn twilight this past weekend, and there were fears that the comet might’ve disintegrated all together as it was tracked by NASA’s STEREO spacecraft. Troubling reports circulated early this week that emission rates for the comet had dropped while dust production had risen, possibly signaling that fragmentation of the nucleus was imminent. Certainly, this comet is full of surprises, and our observational experience with large sungrazing comets of this sort is pretty meager.

Credit: SOHO — ISON (entering frame, to the right) currently “photobombing” SOHO’s LASCO C3 camera. Credit: NASA/ESA/SOHO.

However, as ISON entered the field of view of the Solar and Heliospheric Observatory’s LASCO C3 camera earlier today it still appeared to have some game left in it. NASA’s Solar Dynamics Observatory will pick up ISON starting at around 17:09UT/12:09 PM EST tomorrow, and track it through its history-making perihelion passage for just over two hours until 19:09UT/2:19PM EST.

And just as with Comet Lovejoy a few years ago, all eyes will be glued to the webcast from NASA’s Solar Dynamics Observatory as ISON rounds the bend towards its date with destiny… don’t miss it!

Note: you can also follow ISON’s current progress as seen from SOHO at their website!

The tracking plan for the Solar Dynamics Observatory on November 28th as ISON passes through perihelion. (Credit: NASA/SDO).

For over the past year since its discovery, pundits have pondered what is now the astronomical question of the approaching hour: just what is ISON going to do post-perihelion? Will it dazzle or fizzle? In this context, ISON has truly become “Schrödinger’s Comet,” both alive and dead in the minds of those who would attempt to divine its fate.

Recent estimates place ISON’s nucleus at between 950 and 1,250 metres in diameter. This is well above the 200 metre size that’s considered the “point of no return” for a comet passing this close to the Sun. But again, another key factor to consider is how well put together the nucleus of the comet is: a lumpy rubble pile may not hold up against the intense heat and the gravitational tug of the Sun!

Current updated light curve for ISON. Be sure to check with NASA's Comet ISON Observing Campaign for the latest updates. (Compiled by Matthew Knight on November 24th, 2013). — Current updated light curve for ISON. Be sure to check with NASA’s Comet ISON Observing Campaign for the latest updates. (Compiled by Matthew Knight on November 24th, 2013).

But what are the current prospects for spotting ISON after its fiery perihelion passage?

If the comet holds together, reasonable estimates put its maximum brightness near perihelion at between magnitudes -3 and -5, in the range of the planet Venus at maximum brilliancy. ISON will, however, only stand 14’ arc minutes from the disk of the Sun (less than half its apparent diameter) at perihelion, and spying it will be a tough feat that should only be attempted by advanced observers.

Note that for observers based at high northern latitudes “north of the 60,” the shallow angle of the ecliptic might just make it possible to spot Comet ISON low in the dawn after perihelion and before sunrise November 29^th:

ISON Perihelion 1730UT Fairbanks — ISON post-perihelion at sunrise on November 29th as seen from Fairbanks, Alaska. (Created using Starry Night Education software.

We’ve managed to see the planet Venus the day of solar conjunction during similar circumstances with the Sun just below the horizon while observing from North Pole, Alaska.

Most northern hemisphere observers may catch first sight of Comet ISON post-perihelion around the morning of December 1^st. Look low to the east, about half an hour before local sunrise. Use binoculars to sweep back and forth on your morning comet dawn patrol. Note that on December 1^st, Saturn, Mercury, and the slim waning crescent Moon will also perch nearby!

Comet ISON will rapidly gain elevation on successive mornings as it heads off to the northeast, but will also rapidly decrease in brightness as well. If current projections hold, ISON will dip back below magnitude 0 just a few days after perihelion, and back below naked eye visibility by late December. Observers may also be able to start picking it up low to the west at dusk by mid-December, but mornings will be your best bet.

ISON path — The path of comet ISON for the first week of December as seen from latitude 30 degrees north. Note: the planets and the Moon are depicted for December 1st. (Created using Stellarium).

Keep in mind, if ISON fizzles, this could become a “death-watch” for the remnants of the comet, as fragments that might only be visible with binoculars or a telescope follow its outward path. If this turns out to be the case, then the best views of the “Comet formerly known as ISON” have already occurred.

Another possible scenario is that the comet might fragment right around perihelion, leaving us with a brief but brilliant “headless comet,” similar to W3 Lovejoy back in late 2011. The forward light scattering angle for any comet is key to visibility, and in this aspect, ISON is just on the grim edge in terms of its potential to enter the annals of “great” comets, such as Comet Ikeya-Seki back in 1965.

ISON will then run nearly parallel to the 16 hour line in right ascension from south to north through the month of December as it crosses the celestial equator, headed for a date with the north celestial pole just past New Years Day, 2014.

Whether as fragments or whole, comets have to obey Sir Isaac and his laws of physics as they trace their elliptical path back out of the solar system. Keep in mind, a comet’s dust tail actually precedes it on its way outbound as the solar wind sweeps past, a counter-intuitive but neat concept we may just get to see in action soon.

Here are some key dates to watch for as ISON makes tracks across the northern hemisphere sky. Passages are noted near stars brighter than +5^th magnitude and closer than one degree except as mentioned:

November 29th through December 15th. — The celestial path of ISON from November 29th to December 15th. (Credit: Starry Night).

December 1st: ISON is grouped with Saturn, Mercury and the slim crescent Moon in the dawn.

December 2nd: Passes near the +4.9 magnitude star Psi Scorpii.

December 3rd: Passes into the constellation Ophiuchus.

December 5th: Passes near the +2.7 magnitude multiple star Yed Prior.

December 6th: Crosses into the constellation Serpens Caput.

December 8th: Crosses from south to north of the celestial equator.

December 15th: Passes into the constellation Hercules and near the +5^th magnitude star Kappa Herculis.

December 17th: The Moon reaches Full, marking the middle of a week with decreased visibility for the comet.

December 19th: Passes into the constellation of Corona Borealis.

December 20th: Passes near the +4.8^th magnitude star Xi Coronae Borealis.

December 22nd: Passes 5 degrees from the globular cluster M13. Photo op!

Dec 16-Jan 8 — The path of Comet ISON from December 16th to January 8th. (Credit: Starry Night).

December 23^rd: Crosses back into the constellation Hercules.

December 24^th: Passes near the +3.9 magnitude star Tau Herculis.

December 26^th: Comet ISON passes closest to Earth at 0.43 A.U. or 64 million kilometres distant, now moving with a maximum apparent motion of nearly 4 degrees a day.

December 26^th: Crosses into the constellation Draco and becomes circumpolar for observers based at latitude 40 north.

December 28^th: Passes the +2.7 magnitude star Aldhibain.

December 29^th: Passes the +4.8 magnitude star 18 Draconis.

December 31^st: Passes the 4.9 magnitude star 15 Draconis.

January 2^nd: Crosses into the constellation Ursa Minor.

January 4th: Crosses briefly back into the constellation Draco.

January 6th: Crosses back into the constellation Ursa Minor.

January 7th: Crosses into Cepheus; passes within 2.5 degrees of Polaris and the North Celestial Pole.

And after what is (hopefully) a brilliant show, ISON will head back out into the depths of the solar system, perhaps never to return. Whatever the case turns out to be, observations of ISON will have produced some first-rate science… and no planets, popes or prophets will have been harmed in the process. And while those in the business of predicting doom will have moved on to the next apocalypse in 2014, the rest of us will have hopefully witnessed a dazzling spectacle from this icy Oort Cloud visitor, as we await the appearance of the next Great Comet.

Enjoy the show!

ISON: "Great Comet" or the "Great Pumpkin?" Photo and gourd-based artwork by author. — ISON: “Great Comet” or “Great Pumpkin?” Photo and gourd-based artwork by author.

– Got question about Comet ISON? Lights in the Dark has answers!

– Be sure to post those amazing post-perihelion pics of Comet ISON on Universe Today’s Flickr page.

November 20, 2013December 23, 2015 by David Dickinson

Get Out Your Comet Scorecards: Comet Nevski Now Visible With Binoculars

Capture of Comet Nevski shortly after discovery using the ITelescope Observatory in New Mexico. (Credit: Ernesto Guido, Nick Howes & Martino Nicolini).

Is 2013 truly the “Year of the Comet?” Perhaps “Comets” might be a better term, as no less than five comets brighter than +10^th magnitude grace the pre-dawn sky for northern hemisphere observers.

Comet C/2013 V3 Nevski has just brightened up 6 magnitudes — just over a 250-fold increase in brightness — and now sits at around magnitude +8.8. Comet Nevski was just recently discovered by Vitali Nevski using a 0.4 metre reflecting telescope 12 days ago on November 8^th. If that name sounds familiar, it’s because Nevski discovered the comet from the Kislovodsk observatory located near Kislovodsk, Russia which is part of the International Scientific Optical Network survey which located comet ISON last year. In fact, there was some brief controversy early on in its discovery that Comet C/2012 S1 ISON should have had the moniker Comet Nevski-Novichonok.

At the time of discovery, Comet Nevski appeared to be nothing special: shining at magnitude +15.1, it was well below our +10 magnitude limit for consideration as “interesting,” and was projected to linger there for the duration of its passage through the inner solar system. About a dozen odd such comet discoveries crop up per year, most of which give astronomers a brief pause as the orbit and size of the comet become better known, only to discern that they’re most likely to be nothing extraordinary.

The orbit of comet Nevski, as seen during the closest approach to the Earth on December 21st. (Credit: The Solar System Dynamics JPL Small-Body Database Browser).

Such was to be the case with Comet Nevski, until it suddenly flared up this past weekend.

Observer Gianluca Masi caught Comet Nevski in outburst, using a Celestron C14 remotely as part of the Virtual Telescope 2.0 project:

Comet Nevski captured on November 14th by Gianluca Masi. (Credit: The Virtual Telescope 2.0 Project).

You’ll note that Comet Nevski shows a small, spiky tail on the brief exposure. As of this writing, it currently sits at between magnitudes +8 and +9 and should remain there for the coming week if this current outburst holds.

Comet Nevski is well placed for northern hemisphere observers high in the morning sky, and will spend the remainder of November and early December crossing the astronomical constellation of Leo.

The celestial path of Comet Nevski from mid-November to the end of December. (Created by the author using Starry Night Education simulation software).

Here’s a blow-by-blow rundown on noteworthy events for this comet for the remainder of 2013:

November 23rd: Passes the +5.3 magnitude star Psi Leonis and crosses north of the ecliptic plane.

December 1st: Passes +3.4 magnitude star Eta Leonis.

December 6th: Passes +4.8 magnitude 40 Leonis and the bright +2nd magnitude star Algieba.

December 15th: Crosses into the constellation Leo Minor.

December 17th: Passes near the +5.5^th magnitude star 40 Leonis Minoris.

December 21st: Passes closest to Earth, at 0.847 Astronomical Units (A.U.s), or 126 million kilometres distant.

December 30th: Passes into the constellation Ursae Majoris.

Note that a “close pass” denotes a passage of the comet within a degree of a bright or interesting object.

The orbit of Comet Nevski is inclined 31.5 degrees relative to the ecliptic, and it will be headed for circumpolar for observers based in high northern latitudes as it dips back down below our “interesting” threshold of magnitude +10 in early 2014.

This comet passed perihelion on October 27^th, 2013 just over a week prior to discovery. Comet Nevski is Halley-type comet, with a 27.5 year orbit.

So, looking at the “Comet Scorecard,” we currently have:

Comet C/2012 X1 LINEAR: Still undergoing a moderate outburst at magnitude +8.2, very low to the north east for northern hemisphere observers at dawn in the constellation Boötes.

Comet 2P/Encke: Reaches perihelion tomorrow at 0.33 AU’s from the Sun, shining at magnitude +7.7 near Mercury in the dawn sky but is now mostly lost in the Sun’s glare.

Comet C/2013 R1 Lovejoy: is currently well placed in the constellation Ursa Major crossing into Canes Venatici in the hours before dawn. Currently shining at magnitude +5.4, Comet R1 Lovejoy is visible to the unaided eye from a dark sky site. We caught sight of the comet last week with binoculars, looking like an unresolved globular cluster as it passed through the constellations of Leo and Leo Minor.

And of course, Comet C/2012 S1 ISON: As of this writing, ISON is performing up to expectations as it approaches Mercury low in the dawn shining at just above +4^th magnitude. We’ve seen some stunning pictures as of late as ISON unfurls its tail, and now the eyes of the astronomical community will turn towards the main act: perihelion on November 28^th. Will it fizzle or dazzle? More to come next week!

The recent outbursts of Comets X1 LINEAR and V3 Nevski are reminiscent of the major outburst of Comet Holmes back in 2007. Of course, the inevitable attempts to link these outbursts to the current sputtering solar max will ensue, but to our knowledge, no conclusive correlations exist. Remember, the outburst from Comet Holmes occurred as we were approaching what was to become a profound solar minimum.

Also, it might be tempting to imagine that all of these comets are somehow related, but they are in fact each on unique and very different orbits, and only appear in the rough general direction in the sky as seen from our Earthly vantage point… a boon for dawn patrol sky watchers!

Got pics? Send ‘em in to Universe Today!

November 14, 2013December 23, 2015 by David Dickinson

Here Comes the Weekend Leonid Meteor Shower!

November 2013 offers a chance to catch a dependable meteor shower, albeit on an off year. The Leonid meteors are set to reach their annual peak this coming weekend on Sunday, November 17th. We say it’s an off-year, but not that it should discourage you from attempting to catch the Leonids this weekend in the early dawn.

Projections for 2013 suggest a twin-peaked maximum, with the first peak arriving on November 17^th at 10:00 UT/5:00 AM EST favoring North America, and the second one reaching Earth on the same date six hours later at 16:00 UT/11:00, favoring the central Pacific.

Unfortunately, the Full Moon also occurs the on very date that the Leonids peak at 10:16 AM EST/ 15:16UT, right between the two peaks! This will definitely cut down on the number of meteors you’ll see in the early AM hours.

That’s strike one against the 2013 Leonids. The next is the curious sporadic nature of this shower. Normally a minor shower with a zenithal hourly rate (ZHR) in the range of 10-20 per hour, the Leonids are prone to great storms topping a ZHR of 1,000+ every 33 years. We last experienced such an event in 1998 and 1999, and we’re now approaching the mid-point lull between storms in the 2014-2016 time frame.

An early Leonid meteor captured last week from the United Kingdom Meteor Observing Network's Church Crookham station. (Credit: UKMON/Peter-Campbell-Burns). — An early Leonid meteor captured last week from the United Kingdom Meteor Observing Network’s Church Crookham station. (Credit: UKMON/Peter-Campbell-Burns).

Still, this is one shower that’s always worth monitoring. The source of the Leonids is Comet 55p/Tempel-Tuttle, which is on a 33-year orbit and is due to reach perihelion again in 2031.

Note that the Leonids have also continued to show enhanced activity in past years even when the Moon was a factor:

2012- ZHR=47.

2011- ZHR=22, Moon=8% waning gibbous.

2010- ZHR=40, 86% waxing gibbous.

2009- ZHR=79.

2008-70 ZHR=72% waning gibbous

We even managed to observe the Leonid meteors from Vail, Arizona in 2002 and 2005, on years when the Moon was nearly Full.

Now, for the good news. The Leonids have a characteristic r value of 2.5, meaning that they produce a higher than normal ratio of fireballs. About 50-70% of Leonid meteors are estimated to leave persistent trains, a good reason to keep a pair of binoculars handy. And hey, at least the 2013 Leonids peak on the weekend, and there’s always comet’s ISON, X1 LINEAR, 2P/Encke and R1 Lovejoy to track down to boot!

A 2002 Leonid captured over Redstone Arsenal, Alabama. (Credit: NASA/MSFC/MEO/Bill Cooke).

Here’s a few tips and tricks that you can use to “beat the Moon” on your Leonid quest. One is to start observing now, on the moonless mornings leading up to the 17^th. You’ll always see more Leonid meteors past local midnight as the radiant rises to the northeast. This is because you’re standing on the portion of the Earth turning forward into the meteor stream. Remember, the front windshield of your car (the Earth) always collects the most bugs (meteors). Observers who witnessed the 1966 Leonid storm reported a ZHR in excess of thousands per hour, producing a Star Trek-like effect of the Earth plowing through a “snowstorm” of meteors!

The radiant of the Leonids sits in the center of the backwards question mark asterism of the “Sickle” in the astronomical constellation Leo (hence name of the shower).

You can also improve your prospects for seeing meteors by blocking the Moon behind a building or hill. Though the Leonids will appear to radiate from Leo, they can appear anywhere in the sky. Several other minor showers, such as the Taurids and the Monocerotids, are also active in November.

Meteor shower photography is simple and can be done with nothing more than a DSLR camera on a tripod. This year, you’ll probably want to keep manual exposures short due to the Full Moon and in the 20 seconds or faster range. Simply set the camera to a low f-stop/high ISO setting and a wide field of view and shoot continuously. Catching a meteor involves luck and patience, and be sure to examine the frames after a session; every meteor I’ve caught on camera went unnoticed during observation! Don’t be afraid to experiment with different combinations to get the sky conditions just right. Also, be sure to carry and extra set of charged camera batteries, as long exposures combined with chilly November mornings can drain DSLR batteries in a hurry!

A Woodcut print depicting the 1933 Leonids as seem from Niagara Falls. (Wikimedia Commons image in the Public Domian). — A Woodcut print depicting the 1933 Leonids as seem from Niagara Falls. (Wikimedia Commons image in the Public Domain).

The Leonids certainly have a storied history, dating back to before meteors where understood to be dust grains left by comets. The 1833 Leonids were and awesome and terrifying spectacle to those who witnessed them up and down the eastern seaboard of the U.S. In fact, the single 1833 outburst has been cited as contributing to the multiple religious fundamentalist movements that cropped up in the U.S. in the 1830s.

We witnessed the 1998 Leonids from the deserts of Kuwait while stationed at Al Jabber Air Base. It was easily one of the best meteor displays we ever saw, with a ZHR reaching in access of 500 per hour before dawn. It was intense enough that fireballs behind us would often light up the foreground like camera flashes!

Reporting rates and activity for meteor showers is always fun and easy to do — its real science that you can do using nothing more than a stopwatch and your eyes. The International Meteor Association is always looking for current meteor counts from observers. Data goes towards refining our understanding and modeling of meteor streams and future predictions. The IMO should also have a live ZHR graph for the 2013 Leonids running soon.

Have fun, stay warm, send those Leonid captures in to Universe Today, and don’t forget to tweet those meteors to #Meteorwatch!

November 11, 2013December 23, 2015 by David Dickinson

Tracking Comet C/2013 R1 Lovejoy through November

Comet R1 Lovejoy passes the Beehive Cluster: (Credit Damian Peach).

Tired of comets yet? Right now, northern hemisphere observers have four (!) comets within range of binoculars in the dawn sky. Comet C/2012 S1 ISON, is, of course, expected to dazzle towards month’s end. Comet 2P/Encke is an “old standby,” with the shortest orbital period of any comet known at 3.3 years, and is making a favorable appearance this Fall. And comet C/2012 X1 LINEAR added to the morning display recently, reaching about +8^th magnitude in an unexpected outburst…

But the brightest and best placed comet for morning viewing is currently Comet C/2013 R1 Lovejoy. Shining at +6^th magnitude, R1 Lovejoy just passed into the constellation Leo after a photogenic pass near the Beehive Cluster (M44) in Cancer last week. We caught sight of R1 Lovejoy a few mornings ago, and it’s an easy binocular object, looking like a fuzzy unresolved globular cluster with barely the hint of a tail.

If the name sounds familiar, that’s because the comet was discovered by Australian observer Terry Lovejoy, the prolific discoverer of four comets, including the brilliant sungrazing Comet C/2011 W3 Lovejoy that survived its 140,000 kilometre perihelion passage above the surface of the Sun on December 16th and went on to dazzle southern hemisphere observers in late 2011 and early 2012.

Comet R1 Lovejoy as imaged by Rob Sparks (@HalfAstro) from Tucson, Arizona near the Beehive cluster. (Credit: Rob Sparks). — Comet R1 Lovejoy as imaged by Rob Sparks (@HalfAstro) from Tucson, Arizona passing near the Beehive cluster. (Credit: Rob Sparks).

Terry discovered R1 Lovejoy on September 7^th, 2013 while it was still at magnitude +14.4. The comet is expected to top out at +4^th magnitude in late November as it passes 61.4 million kilometres from Earth on November 19^th and heads for perihelion at 0.877 AUs from the Sun on December 25^nd, 2013. Comet R1 Lovejoy is on a 64 degree orbit highly inclined to the ecliptic, and has a period roughly 7,000 years long. The last time R1 Lovejoy graced Earthly skies, our early ancestors still thought copper smelting was a pretty hip idea!

The orbital path of Comet R1 Lovejoy through the inner solar system. (Credit: NASA/JPL Solar System Dynamics explorer).

And unlike comets Encke and ISON that are plunging near the Sun, Comet R1 Lovejoy never gets closer than 19 degrees elongation from our nearest star in late December. It also reaches a maximum northern declination of 43 degrees on November 28^th, the same day that ISON reaches perihelion. For mid-latitude northern hemisphere observers, R1 Lovejoy will remain well placed at 35 to 45 degrees above the northeastern horizon about an hour before sunrise through late November.

Here are some key dates to aid you in your quest to spy Comet R1 Lovejoy in late November:

November 11^th: Passes near +4.5 Kappa Leonis.

November 14^th: Passes from Leo into the constellation Leo Minor & passes near the +5.3 star 20 Leonis Minoris.

November 16^th: Passes near the +5^th magnitude stars 28, 30, and 34 Leonis Minoris.

November 18^th: Passes into the constellation Ursa Major.

November 19^th: Passes near the +4.8 magnitude star 55 Ursae Majoris & +5.3 magnitude star 57 Ursae Majoris.

November 19^th: Closest to Earth, at 0.4 AUs distant.

The celestial path of Comet R1 Lovejoy spanning November 11th to the 30th. (Created using Starry Night Education software).

November 21^st: Passes into the constellation Canes Venatici.

November 22^nd: Passes near the +6^th magnitude star 4 Canum Venaticorum & the +4.2 magnitude star Chara (Beta Canum Venaticorum).

November 24^th: Passes near the Sunflower Galaxy (M63).

November 27^th: Passes into the constellation Boötes.

December 1^st: Passes near +3.5 magnitude star Nekkar (Beta Boötis).

December 4^th: crosses into Corona Borealis.

Note that passes on the list above denote passages closer than one degree of Comet R1 Lovejoy near bright objects.

Perihelion for the comet is December 25^th at 0.877 AU, and its closest approach to Earth is November 19^th. On this date, it will also be moving at its maximum apparent speed as seen from Earth, covering about 3 degrees of the sky every 24 hours, or the angular span of the Full Moon every 4 hours.

United Kingdom observer Pete Lawrence imaged Comet R1 Lovejoy this past weekend from his backyard garden using a 4-inch apochromatic refractor and a Canon 40D DSLR:

Comet R1 Lovejoy as imaged by Pete Lawrence on November 9th. (Credit: Pete Lawrence).

He also made his first confirmed binocular sighting of Comet ISON using a pair of 15×70 binocs, noting to Universe Today that “ISON’s head appears to be small and stellar compared to Lovejoy’s extended coma, which is obvious in binoculars, and also brighter!”

It’s worth noting that all four of these morning comets are on separate orbital paths, and only seem to be in the same general region of the sky as seen from our Earthly vantage point… and none of them are passing near the Earth!

This week is also a good time to hunt for comets in the pre-dawn sky for another reason: the Moon reaches Full this coming weekend on Sunday, November 17^th. After this week, it will start to creep into the morning sky and interfere with deep sky observations for the next two weeks.

Comet R1 Lovejoy imaged on November 10th by astrophtographer Justin Ng. (Credit: Justin Ng).

It’s also interesting to note that amateur observers discovered two more faint comets this past weekend. Though comets C/2013 V3 Nevski and C/2013 V2 Borisov aren’t slated to be anything spectacular, that brings the number of amateur discoveries to 13 for 2013. Are amateur comet hunters mounting a comeback?

In this age of automated surveys, the question is often raised as to whether amateurs can still discover comets. Keep in mind, Terry Lovejoy found Comet R1 Lovejoy with a medium-sized 8-inch Schmidt Cassegrain reflecting telescope… the age of amateur comet hunters seemes far from over in 2013!

November 6, 2013December 23, 2015 by David Dickinson

Bright Venus Takes Center Stage in November

(Credit: Brian McGaffney/Nutwood Observatory).

“What’s that bright object to the southwest at dusk?” We’ve already fielded more than a few such questions as Earth’s sister world shines in the dusk sky. Venus just passed its maximum elongation 47 degrees east of the Sun on November 1^st, and currently shines at a brilliant magnitude -4.46. This is almost 16 times brighter than the brightest star in the sky, -1.46th magnitude Sirius.

Venus and the waxing crescent Moon, looking to the west tonite at 30 minutes after sunset for latitude 30 degrees north. (Created using Stellarium).

Just like the Moon, Venus goes through a full range of phases. Through the telescope, Venus currently presents a 26.7” diameter disk. That size will swell to almost 40” by month’s end, as Venus begins to approach the Earth and presents a noticeable crescent phase. We just passed dichotomy — the theoretical point where Venus presents a half-illuminated phase as seen from Earth — on October 31^st, and Venus already shows a noticeable crescent:

Venus on the night of November 5th 2013, a quick stack of about 200 frames. (Photo by Author)

Note that we say “theoretical” because there’s typically a discrepancy of a day or two between predicted and observed dichotomy. This is also known as Schröter’s Effect. One probable cause for this is the dazzling appearance of the disk of Venus. We typically use a variable polarizing filter to cut the glare of Venus down at the eyepiece.

You might also note that Venus currently occupies the “basement” of the zodiac in the constellation Sagittarius. In fact, the planet is currently as far south as it can go, sitting at a declination of -27° 14’ on this very evening. You have to go all the way back to 1930 to find a more southerly declination of Venus, just 12’ lower!

But you won’t have to wait much longer to break that record, as the chart below shows for the most southerly declinations of Venus for the next half century:

Year	Date	Declination
2013	November 6^th	-27° 09’
2021	“ “	-27° 14’
2029	“ “	-27° 18’
2037	“ “	-27° 23’
2045	“ “	-27° 29’
2053	“ “	-27° 34’
2061	“ “	-27° 39’

Note that each event occurs on November 6^th, and they’re spaced 8 years apart. Apparitions of Venus closely duplicate their paths in the sky over an 8 year cycle. This is because the planet nearly completes 13 orbits of the Sun for our 8. Venus “catches up” to the Earth on its interior orbit once every 584 days to reach inferior conjunction. It usually passes above or below the Sun from our vantage point, though last year it transited, a feat that won’t be witnessed again until 2117 AD.

How far south can Venus go? Well, its orbit is tilted 3.4 degrees relative to the ecliptic. It can reach a southern declination of -28 05’, though you have to go way back to 1874 for its last occurrence!

Today is also a great time to try your hand at spotting Venus in the daytime, as a 3-day old waxing crescent Moon lies about eight degrees to its upper right:

A daytime Venus near the Moon transiting to the south at about 3:30PM EST today. A 5 degree wide Telrad "bullseye" is provided for scale. (Credit: Stellarium). — A daytime Venus near the Moon, transiting to the south at about 3:30PM EST today. A 5 degree wide Telrad “bullseye” is provided for scale. (Credit: Stellarium).

Note that seeing Venus in the daytime is surprisingly easy, once you known exactly where to look for it. Your best chances are around mid-afternoon at about 3PM local, when the daytime Moon and Venus lie highest in the southern sky. Did you know that Venus is actually intrinsically brighter per square arc second than the Moon? It’s true! The Moon actually has a very low reflective albedo of 12% — about the equivalent of fresh asphalt — while the cloud tops of Venus are more akin the fresh snow with an albedo of about 80%.

Its also worth checking out Venus and its local environs after nightfall as it passes near the Lagoon (M8) and the Trifid nebula (M8) on the night of November 6^th. Continuing with its trek across the star rich plane of the heart of the Milky Way galaxy, Venus also passes near the globular cluster M22 on November 13^th.

Venus also sits in the general of Pluto on November 15^th, lying just 6.6 degrees south of it. Be sure to wave in the general direction of NASA’s New Horizons spacecraft bound for Pluto in July 2015 tonight as well, using the Moon and Venus for a guide:

The position of the Moon, Venus, Pluto, & New Horizons on the night of November 6th, 2013. (Created using Starry Night Education Software). — The position of the Moon, Venus, Pluto, & New Horizons at 14UT on November 7th, 2013. (Created using Starry Night Education Software).

Another shot at seeing Venus paired with the Moon occurs on December 5^th.

Venus also presents a maximum area of illumination on December 6^th, and will shine at its brightest on December 10^th at magnitude -4.7. Can you catch it casting a shadow? The best time to search for this illusive phenomenon would be just before New Moon on December 2^nd. A dark sky site away from any other sources of illumination, and a snow covered ground providing high contrast also helps. Fortunately, snow isn’t in short supply in the northern hemisphere in December!

Venus is currently the only naked eye planet in the November early evening sky. We always thought that it’s a bit of a cosmic irony that the nearest planet presents a dazzling, but featureless white disk as seen from Earth. Diligent amateurs have, however, been able to tease out cloud patterns on Venus using UV filters.

Another elusive phenomenon to watch for as Venus reaches a crescent phase is ashen light. Long reported by observers, a faint glow on the night side of Venus is something that persists, but shouldn’t be. A similar effect seen on the night side of the Moon known as Earthshine is easily explained by sunlight being reflected off of the Earth… but Venus has no moon. What gives? Frequent explanations over the years have been aurorae, electrical activity, airglow, or, more frequently cited, observer bias. The brain wants to see a filled in space, and promptly inserts it betwixt the dazzling horns of the planet.

Keep an eye on Venus as it reaches maximum brilliancy and heads towards inferior conjunction on January 11^th, 2014, and a rare chance to see it on said date… more to come!

November 1, 2013December 23, 2015 by David Dickinson

Watch Live: Sunday’s “Hybrid Solar Eclipse”

Totality! As seen during the November 13th, 2012 total solar eclipse. (Image credit: Narayan Mukkavilli, used with permission).

The chase is on. On Sunday, November 3^rd, the shadow of the Moon will cross the Earth for one last time in 2013. We recently wrote about the prospects for viewing this “hybrid” annular-total solar eclipse as it crosses the Atlantic and central Africa. Viewers from northern South America across the U.S. Eastern Seaboard up into the Canadian Maritimes will also be treated to a brilliant rising partial eclipse over the Atlantic at sunrise. Tickets are already in hand for many, as umbraphiles wing their way (cue Indiana Jones music) to dusty and exotic far off locales to stand briefly in the shadow of our Moon…

But what if it’s cloudy?

Once the bane of eclipse-chasers, you can now thwart our sometimes murky atmosphere by catching the solar eclipse online.

I remember our first experience with eclipse-chasing on the internet, trying to catch an eclipse broadcast on ye ole dial up modem from an internet café (remember internet cafes?) way back in the late 90s. This was pre-You Tube, pre-UStream. Needless to say, the tenuous connection afforded nary a frozen glimpse of the partially eclipsed Sun, and crashed all together at the onset of totality.

Fast forward to 2013, when ginormous data packets routinely fly around the globe.

True, this eclipse presents a challenge, as it crosses some pretty wild and unconnected terrain. But one standby that we can expect is the good people at Slooh, who have dispatched a broadcast team to the African nations of Gabon and Kenya:

As of this writing, Slooh looks to be going live at around 11:45 UT on Sunday November 3^rd. This is 6:45 AM EST, which takes into account our “falling back” one hour to UT -5 hours on Sunday morning. Astronomer Brian Cox will be broadcasting live from Kenya, and the broadcast starts just over two hours prior to the first landfall of totality at just before 14:00 UT. From Gabon, Maximum totality will be a brief 1 minute and 5 seconds, and will dwindle to an even briefer 14 seconds over Lake Turkana in Kenya before ending as a brilliant sunset eclipse over Somalia and Ethiopia. A backup broadcast of the partial phases of the eclipse is also planned from Slooh’s home base site in the Canary Islands.

Another fascinating potential broadcast may come our way from the BRCK organization basing their observations of the eclipse from the shores of Lake Turkana in Kenya. Billed as “Your Backup Generator for the Internet,” BRCK’s mission is to bring broadband access internet to people in remote regions of the world. This weekend’s eclipse certainly qualifies. As of writing this on Halloween, October 31^st, the BRCK team had gone into the field to “stress test” their webcasting capability onsite; follow them on Twitter as @brcknet for the latest updates. As of yet, there’s no embed for the broadcast, though we’ll be sure to drop it in if it surfaces!

There’s also some interesting science afoot during this eclipse as well. A recent press release out from Williams College notes that Field Memorial Professor of Astronomy and chair of the International Astronomical Union’s Working Group on Eclipses Jay Pasachoff will observe the eclipse, along with a student and tourist expedition from Gabon. A veteran eclipse chaser, Pasachoff will be working in concert with Dr. Vojtech Rusin of the Astronomical Institute of Slovakia, solar researchers Aris Voulgaris and Robert Lucas and William College students to study the ethereal solar corona. Satellite-based coronagraphs, such as the one employed by SOHO, can create an “artificial eclipse” of the Sun to study the corona, but also face the challenge of scattered light via a phenomenon known as Fresnel-diffraction. Pasachoff and team hope to combine their observations with those being routinely carried out by NASA, the European Space Agency and the Royal Observatory in Belgium to characterize the solar corona and improve our understanding of the space weather environment. Pasachoff’s expedition is being assisted via support from the South African Astronomical Observatory, Nommo Astronomia, the Gabon Astronomy Society and the Gabon Space Agency. Veteran eclipse chaser and historian Michael Zeiler (@EclipseMaps) has also joined up with Pasachoff’s group in Gabon.

In space, the NASA/JAXA joint solar observing Hinode spacecraft and ESA’s Sun watching Proba-2 will also catch several partial eclipses from their respective perches in low Earth orbit. Expect to see these pics in the days following Sunday’s eclipse.

We’ll be dropping in more broadcasts as they come to our attention this weekend here at Universe Today. Planning an ad-hoc webcast of the eclipse? Let us know in the comments below! Even if it’s just a brief view of the rising partially eclipsed Sun from the beach, its worth the effort. Just remember that you’ll need a fairly long focal length (in the range of 200mm or longer) and a proper solar filter for the Sun to appear like anything more than a washed out dot in the broadcast. And always run a test of your rig beforehand!

Good luck, happy eclipse chasing, and don’t forget to send those eclipse pics to Universe Today!

October 28, 2013April 26, 2016 by David Dickinson

Rare ‘Hybrid’ Solar Eclipse on November 3, 2013: How to See It

A partially eclipsed setting Sun as seen from Dallas, Texas on May 20th, 2012. This weekend's eclipse will offer U.S. East Coast residents a similar sunrise view. (Credit: Jason Major/Lights in the Dark).

It’s almost upon us. The final eclipse of 2013 occurs this coming weekend on Sunday, November 3^rd. This will be the fifth eclipse overall, and the second solar eclipse of 2013. This will also be the only eclipse this year that features a glimpse of totality.

This eclipse is of the rare hybrid variety— that is, it will be an annular eclipse along the very first 15 seconds of its track before transitioning to a total as the Moon’s shadow sweeps just close enough to the Earth to cover the disk of the Sun along the remainder of its track.

An animation of the path of the November 3rd hybrid solar eclipse. (Credit: NASA/Goddard Space Flight Center).

How rare are hybrid solar eclipse? Of the 11,898 solar eclipses listed over a 5,000 year span from 1999 BC to 3000 AD in Fred Espenak’s Five Millennium Catalog of Solar Eclipses, only 569, or 4.8% are hybrids.

Who can see this eclipse?

People from northern South America, across the U.S. Eastern Seaboard and up through the Canadian Maritimes will see a brief partial solar eclipse finishing up around 30 minutes after local sunrise. The brief annular “ring of fire” portion of the eclipse begins at sunrise just ~1,000 kilometres east of Jacksonville, Florida, as it races eastward across the Atlantic. See our timeline, below.

Eclipse prospects for the US East Coast. (Courtesy of Michael Zeiler @EclipseMaps)

Nearly all of Africa and the southern Mediterranean region including Spain will see partial phases of the eclipse, while greatest totality occurs just off of the coast of Liberia and heads for first landfall on the African continent over Wonga Wongue Reserve in Gabon. At this point, the duration of totality will already have shrunk back down to 1 minute and 7 seconds. The shadow of the Moon will then cross central Africa, headed for a short but brilliant sunset total eclipse over Uganda, Ethiopia, Kenya and Somalia.

The global path of this weekends eclipse-click to enlarge. (Credit: Michael Zeiler, @EclipseMaps).

This particular eclipse part of saros series 143 and is member 23 of the 72 eclipses in the cycle. The first eclipse in this saros occurred on March 7^th, 1617, and the last one will occur on April 23^rd, 2897.

Saros 143 also has a checkered place in eclipse history. The last eclipse in this series crossed south eastern Asia on October 24^th, 1995.

The first detailed picture of a solar eclipse was also taken of a saros 143 member on July 28, 1851. And one saros later, a total solar eclipse on August 7^th, 1869 may have saved the butt of astronomer and explorer George Davidson while traversing the wilds of Alaska. And one more saros period later, Dmitri Mendeleev (he of the modern periodic table) observed the total solar eclipse of August 19^th, 1887 from a balloon.

A daguerreotype image of the 1851 eclipse captured by Berkowski of the Royal Observatory in Königsberg, Prussia. (Public domain image).

We’ve compiled a brief worldwide timeline for the November 3^rd hybrid eclipse. Keep in mind, the shift back off of Daylight Saving Time occurs on the same morning as the eclipse for North America, putting the U.S. East Coast once again back to -5 hours off of Universal Time (UT):

10:04 UT: The partial phases of the eclipse begin.

11:05:17 UT: annular phases of the eclipse begin.

11:05:36 UT: The eclipse transitions from an annular to a total along its track.

12:46: The point of greatest eclipse, occurring off of the SW coast of Liberia along the coast of Africa. The path will be 57 kilometres wide at this point with a maximum duration for totality at 1 minute & 40 seconds.

14:27 UT: The total phases of the eclipse end.

15:28 UT: Partial phases end.

Remember that solar safety is paramount while observing an eclipse during all partial phases. This is especially critical, as millions of viewers along the U.S. East Coast are poised to catch the eclipse at sunrise over the Atlantic on Sunday. Use only glasses designed specifically for eclipse viewing or welder’s glass #14. One project headed by Astronomers Without Borders is also working to provide eclipse glasses to schools in Africa.

Students in Tanzania demonstrating proper eclipse viewing safety. (Credit: Astronomers Without Borders).

Projecting the Sun onto a wall or a piece of paper is also a safe method to observe the eclipse. Construction of a Sun Gun, a pinhole projector, or even using a spaghetti strainer or colander to project the partially eclipsed sun are all fun projects to try.

Shooting pictures of the rising eclipse is also possible using a DSLR. To capture the disk of the Sun plus an outline of the foreground, you’ll want to use a combination of low ISO 100 and a fast shutter speed (1/4000 or faster) and a zoom lens of at least 200mm or greater. Keep in mind, DO NOT look at the Sun through the camera’s view finder— simply set the focus to infinity and aim via projection. It’s worth practicing your technique a morning or two prior to the main event!

As the partial phase of the eclipse progresses, keep an eye out for “tiny crescents” that may litter the ground. These are caused by gaps in things such as leaves, latticework, etc that may act as natural “pinhole projectors”. Those lucky enough to stand in the path of totality may snare a look at shadow bands sweeping across the landscape as totality approaches, as well as catch a brief glimpse of Baily’s Beads and the pearly white corona of the Sun.

Totality will last less than a minute across most of central Africa, giving viewers a very hurried view before partial phases commence once more. Venus will be easily visible at magnitude -4.4 just 47 degrees east of the Sun. Unfortunately, prospects aren’t great for air or seaborne viewers in the mid-Atlantic to catch sight of comet ISON during the frenzied moments of totality, which will sit 50 degrees from the Sun between magnitude +7 & +8.

The sky over Gabon during mid-eclipse. (Created by the author using Starry Nite).

Weather prospects are an all-important consideration when planning for an eclipse. Jay Anderson maintains an outstanding site with projections tailor-made for each eclipse. For the U.S. East Coast, clear skies right down to the crucial eastern horizon will be key!

A recent surge in piracy off of the West Coast of Africa may also factor into travel considerations for eclipse chasers. You can actually monitor such activities on the high seas now in near real time. Perhaps one could take a page from Mark Twain’s A Connecticut Yankee in King Arthur’s Court, and impress any would-be-brigands with the glory of an impending solar eclipse…

Unfortunately, the International Space Station will have an orbit nearly perpendicular to the Earth-Moon-Sun syzygy, and won’t lend itself to any great prospects of a transit during the partial phases of the eclipse. ESA’s Proba-2 and JAXA’s Hinode will, however, see several partial eclipses from orbit:

Sunspot activity has also been on the upswing as of late, making for a photogenic Sun heading into the partial phases of the eclipse. A well-placed, naked eye Coronal Mass Ejection on the solar limb also isn’t out of the question. Eclipse historian and expert Michael Zeiler notes that a CME last occurred during a total solar eclipse way back in 1860.

Sunspot activity as of October 28th... will it stay active until this weekend's eclipse? (Photo by author). — Sunspot activity as of October 28th… will it stay active until this weekend’s eclipse? (Photo by author).

Totality for this eclipse passes over some wild and largely wifi free areas; few plans to broadcast the eclipse live have surfaced thus far.

Slooh plans a broadcast, as did a proposed Indiegogo project whose current status is unclear. BRCK also plans to broadcast the eclipse live from the shores of Lake Turkana, Kenya. Got plans to webcast even the partial phases of the eclipse? Let us know!

And speaking of eclipse chasing, we plan on heading to the Florida Space Coast Sunday morning at o’dark thirty to nab the partial sunrise eclipse over the Atlantic.

And as always, the question posed immediately after totality is: when’s the next one? Well, the next annular eclipse graces Australia on April 29^th, 2014. The U.S. will also see a partial solar eclipse on October 23^rd next year… but totality will not touch the surface of our fair planet until a high Arctic eclipse on March 20^th, 2015.

Good luck, clear skies, and safe journeys to all who are chasing after this one near and far, and don’t forget to post those pics to Universe Today’s Flickr page!

-See more of Michael Zeiler’s work at Eclipse Maps.

-Simulations were created using Starry Night Education Software.

October 23, 2013December 23, 2015 by David Dickinson

Comet LINEAR Suddenly Brightens with Outburst: How to See It

Comet C/2012 X1 LINEAR as imaged by Howes, Guido & Nicolini on Monday, October 21st. (Credit: remanzacco.blogspot)

It’s swiftly becoming an “all comets, all the time” sort of observing season. The cyber-ink was barely dry on our “How to Spot Comet 2P/Encke” post this past Monday when we were alerted to another comet that is currently in the midst of a bright outburst.

That comet is C/2012 X1 LINEAR. Discovered on December 8^th, 2012 by the ongoing Lincoln Near Earth Asteroid Research (LINEAR) survey based in Socorro, New Mexico, Comet X1 LINEAR was expected to peak out at about +12^th magnitude in early 2014.

That all changed early this week, when amateur observers began to report a swift change in brightness for the otherwise nondescript comet. Japanese observer Hidetaka Sato reported the comet at magnitude +8.5 on October 20^th, a full 5.5 magnitudes above its expected brightness of +14. Remember, the magnitude scale is logarithmic, and the lower the number, the brighter the object. Also, 5 magnitudes represent an increase in brightness of 100-fold.

Astronomers Nick Howes, Martino Nicolini and Ernesto Guido used the remote 0.5 metre iTelescope based in New Mexico on the morning of Monday, October 21^st to confirm the outburst. Other amateurs and professional instruments are just now getting a look at the “new and improved” Comet X1 LINEAR low in the dawn sky. Romanian amateur observer Maximilian Teodorescu noted on yesterday’s Spaceweather that the comet was not visible through his 4.5 inch refractor, though it was easy enough to image.

Comet X1 LINEAR currently sits in the constellation Coma Berenices about mid-way between the stars Diadem, (Alpha Coma Berenices) and Beta Coma Berenices. Shining at +8.5 magnitude, the coma is about 85” across with a 10” bright central region. This gives X1 LINEAR the appearance of an unresolved +8^th magnitude globular cluster. In fact, a classic globular and a star party fave known as M3 lies about 8 degrees away at the junction of the constellations Canes Venatici, Boötes and Coma Berenices. M3 shines at +7^th magnitude and will make a great contrast on the hunt for the comet.

Unfortunately, the window of time to search for the comet is currently short. From latitude 30 degrees north, the comet sits only 15 degrees about the northeast horizon 30 minutes before local sunrise. The situation is a bit better for observers farther to the north, and mid-November sees the comet 20 degrees above the horizon in the dawn sky.

Comet X1 LINEAR is currently covering 40’ (2/3^rdsof a degree, or 1 1/3 the size of a Full Moon) a day, and will spend most of the month of November in the constellation Boötes. Keep in mind, X1 LINEAR is currently still on brightening trend “with a bullet.” Revised light curves now show it on track to reach magnitude +6 near perihelion early next year, but further brightening could still be in the cards for this one. Remember Comet 17P/Holmes a few years back? That one jumped from an uber-faint +17^th magnitude to a naked eye brightness of +2.8 in less than 48 hours.

Comet X1 LINEAR will reach a perihelion of 1.6 Astronomical Units (A.U.s) from the Sun on February 21st, 2014, and pass 1.6 A.U.s from the Earth around June 28^th, 2014. The comet has a high inclination of 44.4° degrees relative to the ecliptic, and is on a respectable 1872 year orbit.

Here are some notable dates for the comet through the end of 2013;

The path of Comet C/2012 X1 LINEAR from October 23 to November 28th. Click to enlarge. (Credit: Created using Starry Night Education Software).

-November 2^nd: Crosses into the constellation Boötes.

-November 6^th: Passes near the +4.9^th magnitude star 6 Boötis.

-November 16^th: Passes near the bright star Arcturus.

-December 6^th: Crosses into the constellation Serpens Caput.

-December 10^th: Passes near the +5 magnitude star Tau1 Serpentis.

-December 14^th: Comet X1 LINEAR sits only 8 degrees from Comet ISON.

-December 26^th: Crosses into the constellation Hercules.

Note: “Passes near” on the above list denotes a pass closer than one degree, except as noted.

Now, we REALLY need the Moon to pass Last Quarter phase this coming Saturday so we can get a good look at all of these dawn comets! As of writing this, the current scorecard of binocular comets— comets with a brightness between magnitude +6 and +10 —sits at:

-2P Encke: +7.9 magnitude in Leo.

-C/2013 R1 Lovejoy: +8.7^th magnitude in Canis Minor.

-C/2013 X1 LINEAR: +8.5^th magnitude in Coma Berenices.

-C/2012 S1 ISON: +9.7^th magnitude in Leo.

-C/2012 V2 LINEAR: +8.9^th magnitude in Centaurus.

Comet X1 LINEAR on the morning of October 25th, as seen from latitude 30 degrees north 45 minutes prior to sunrise. (Created using Stellarium).

It’s also amusing to note how the method of notification for these sorts of outbursts has changed in recent years. I first heard of the outburst of X1 LINEAR on Monday evening via Twitter. Contrast this with Comet Holmes in 2007, which came to our attention via message board RSS feed. And way back in 1983, we all read about of the close passage of Comet IRAS-Araki-Alcock… weeks after it occurred!

Another curious phenomenon may also work its way through the news cycle. When Comet Holmes became a hit back in 2007, spurious reports of comets brightening became fashionable. If you were to believe everything you read on the web, it suddenly seemed like every comet was undergoing an outburst! This sort of psychological trend towards wish fulfillment may come to pass again as interest in comet outbursts mounts.

It’s also worth noting that, contrary to rumors flying around ye’ ole web, Comet X1 LINEAR is not following Comet ISON. The two are on vastly different orbits, and only roughly lie along the same line of sight as seen from our Earthly vantage point.

The orbital path of Comet X1 LINEAR. (Credit: The JPL Solar System Dynamics Small-Body Database Browser). — The orbital path of Comet C/2012 X1 LINEAR. (Credit: The JPL Solar System Dynamics Small-Body Database Browser).

And that’s it for our weekly (daily?) segment of “As the Comets Turn…” don’t forget to “fall back” one hour and plan your morning comet-hunting vigil accordingly this coming Sunday if you live in Europe-UK. North America still has until November 3^rd to follow suit.

Happy comet hunting!

-Got a recent pic of Comet X1 LINEAR? be sure to post it in the Universe Today Flickr forum!

October 21, 2013December 23, 2015 by David Dickinson

How to See This Season’s “Other” Comet: 2P/Encke

Comet 2P/Encke as imaged by Damian Peach on October 12th. (Credit: D. Peach)

2013 may well go down as “The Year of the Comet.” After over a decade punctuated by only sporadic bright comets such as 17P/Holmes, C/2011 W3 Lovejoy and C/2006 P1 McNaught, we’ve already had two naked eye comets visible this year by way of C/2012 F6 Lemmon and C/2011 L4 PanSTARRS. And of course, all eyes are on Comet C/2012 S1 ISON as it plunges towards perihelion on U.S. Thanksgiving Day, November 28^th.

But there’s an “old faithful” of comets that’s currently in our solar neighborhood, and worth checking out as well. Comet 2P/Encke (pronounced EN-key) currently shines at magnitude +7.9 and is crossing from the constellation Leo Minor into Leo this week. In fact, Encke is currently 2 magnitudes— over 6 times brighter than Comet ISON —and is currently the brightest comet in our skies. Encke is expected to top out at magnitude +7 right around perihelion towards the end of November. Encke will be a fine binocular object over the next month, and once the Moon passes Last Quarter phase on October 26^th we’ll once again have a good three week window for pre-dawn comet hunting. Comet Encke made its closest pass of the Earth for this orbit on October 17^th at 0.48 Astronomical Units (A.U.s) distant. This month sees its closest passage to the Earth since 2003, and the comet won’t pass closer until July 11^th, 2030.

The orbital path of Comet 2P/Encke. (Credit: The NASA/JPL Solar System Dynamics Small-Body Database Browser).

This will be Comet Encke’s 62^nd observed perihelion passage since its discovery by Pierre Méchain in 1786. Encke has the shortest orbit of any known periodic comet, at just 3.3 years. About every 33 years we get a favorable close pass of the comet, as last occurred in 1997, and will next occur in 2030.

But this year’s apparition of Comet Encke is especially favorable for northern hemisphere observers. This is due to its relatively high orbital inclination angle of 11.8 degrees and its passage through the morning skies from north of both the ecliptic and the celestial equator. Encke is about half an A.U. ahead of us in our orbit this month, crossing roughly perpendicular to our line of sight.

Note that Encke is also running nearly parallel to Comet ISON from our vantage point as they both make the plunge through the constellation Virgo into next month. Mark your calendars: both ISON and Encke will fit into a telescopic wide field of view around November 24^th in the early dawn. Photo-op!

Here are some key dates to help you in your morning quest for Comet Encke over the next month:

-October 22^nd: Crosses into the constellation Leo.

-October 24^th: Passes near the +5.3 magnitude star 92 Leonis.

-October 25^th: Passes near the +4.5 magnitude star 93 Leonis.

-October 27^th: Passes briefly into the constellation Coma Berenices.

-October 29^th: Passes near the +11^th magnitude galaxy M98, and crosses into the constellation Virgo.

-October 30^th: Passes near the +10^th magnitude galaxy pair of M84 & M86.

2P Encke from 20 Oct to 20 Nov (Created using Starry Night Education Software). — The celestial path of Comet 2P/Encke from October 20th to 20 November 20th. Note that ISON is very near Encke on the final date. Click on the image to enlarge. (Created using Starry Night Education Software).

-November 2^nd: Passes between the two +5^th magnitude stars of 31 and 32 Virginis.

-November 3^rd: A hybrid solar eclipse occurs across the Atlantic and central Africa. It may just be possible to spot comet Encke with binoculars during the brief moments of totality.

-November 4^th: Passes near the +3.4 magnitude star Auva (Delta Virginis).

-November 7^th: Crosses from north to south over the celestial equator.

-November 11^th: Passes near the +5.7^th star 80 Virginis.

-November 17^th: The Moon reaches Full, and enters into the morning sky.

-November 18^th: Passes 0.02 A.U. (just under 3 million kilometers, or 7.8 Earth-Moon distances) from the planet Mercury. A good chance for NASA’s Messenger spacecraft to perhaps snap a pic of the comet?

-November 19^th: Passes 1.5 degrees from Mercury and crosses into the constellation Libra.

-November 20^th: Crosses to the south of the ecliptic plane.

-November 21^st: Reaches perihelion, at 0.33 AU from the Sun.

-November 24^th: Comet Encke passes just 1.25 degrees from Comet ISON. Both will have a western elongation of 15 degrees from the Sun.

-November 26^th: Passes near the +4.5 magnitude star Iota Librae and the +6th magnitude star 25 Librae.

-December 1^st: Crosses into the constellation Scorpius.

-December 5^th: Enters into view of SOHO’s LASCO C3 camera.

Note: “Passes near” on the above list indicates a passage of Comet Encke less than one angular degree (about twice the size of a Full Moon) from an interesting object, except where noted otherwise.

Binoculars are your best bet for catching sight of Comet 2P/Encke. For middle northern latitude observers, Comet Encke reaches an elevation above 20 degrees from the horizon about two hours before local sunrise. Keep in mind, Europe and the U.K. “fall back” an hour to Standard Time this coming weekend on October 27^th, and most of North America follows suit on November 3^rd, pushing the morning comet vigil back an hour as well.

Two other comets are both currently brighter than ISON and also merit searching for: Comet C/2013 R1 Lovejoy, at +8.7^th magnitude in Canis Minor, and Comet C/2012 X1 LINEAR, currently also in Coma Berenices and undergoing a minor outburst at magnitude +8.5.

Be sure to check these celestial wonders out as we prepare for the “Main Event” of Comet ISON in November 2013!

October 14, 2013December 23, 2015 by David Dickinson

This Week’s Penumbral Lunar Eclipse and the Astronomy of Columbus

You can always count on an eclipse to get you out of a delicate situation. Today is Columbus Day in the United States and Thanksgiving north of the border in Canada. Later this week also marks the start of the second eclipse season for 2013. Today, we thought we’d take a look at the circumstances for the first eclipse of the season kicking off this coming Friday night, October 18, as well as the fascinating role that eclipses played in the life and times of Christopher Columbus.

Friday’s event is a penumbral lunar eclipse, meaning that the Full Moon will only pass through the outer bright rim of the Earth’s shadow. Such events are subtle affairs, as opposed to total and partial lunar eclipses, which occur when the Moon enters the dark inner core, or umbra, of the Earth’s shadow. Still, you may just be able to notice a slight dusky shading on the lower southern limb of the Moon as it flirts with the umbra, barely missing it around the time of central eclipse at 23:51 Universal Time/ 7:51 PM Eastern Daylight Saving Time. Friday night’s penumbral is 3 hours and 59 minutes in duration, and 76.5% of the disk of the Moon will be immersed in the penumbra at maximum eclipse.

Key Events occurring on Friday, October 18^th:

21:50UT/5:50PM EDT: 1^st contact with the Earth’s shadow.

23:51UT/7:51PM EDT: Mid-eclipse.

01:49UT(Oct 19^th)/9:49PM EDT: Last contact. Eclipse ends.

The eclipse will be underway at moonrise for North and South America and occur at moonset for central Asia— Africa and Europe will see the entire eclipse. Standing on Earth’s Moon, an observer on the nearside would see a partial solar eclipse.

A simulation of Friday's lunar eclipse, looking back from Earth Moon at mid-eclipse. (Credit: — A simulation of Friday’s lunar eclipse, looking back from Moon at mid-eclipse. (Wikimedia Commons graphic in the Public Domain).

This eclipse is the 3^rd and final lunar eclipse of 2013, and the 5^th overall. It’s also the first in a series of four descending node eclipses, including the total lunar eclipse of October 8^th next year. It’s also the 52^nd eclipse of 72 in the lunar saros series 117, which started on April 3^rd, 1094 and will end with a final lunar eclipse on May 15^th, 2356. Saros 117 produced its last total lunar eclipse in 1815 and its final partial in 1941.

Though penumbrals are slight events, we’ve been able to notice an appreciable difference before, during and after the eclipse photographically:

Penumbral I — Can you spy the difference? The May 18th, 2002 penumbral lunar eclipse before (left) and during mid-eclipse (right). Photos by Author.

Be sure to use identical exposure settings to catch this effect. Locations where the Moon rides high in the sky also stand the best chance of imaging the faint penumbral shading, as the Moon will be above the discoloring effects of the thicker air mass low to the horizon.

The Moon reaches descending node along the ecliptic about 20 hours after the end of the eclipse, and reaches apogee just over six days later on October 25^th. The October Full Moon is also known as the Hunter’s Moon, providing a bit of extra illumination on the Fall hunt.

And this sets us up for the second eclipse of the season the next time the Moon crosses an ecliptic node, a hybrid (annular-total) solar eclipse spanning the Atlantic and Africa on November 3^rd. More to come on that big ticket event soon!

In Columbus’s day, the Moon was often used to get a rough fix of a ship’s longitude at sea. Columbus was especially intrigued with the idea of using lunar eclipses to determine longitude. If you can note the position of the Moon in the sky from one location versus a known longitude during an event— such as first contact of the Moon with the Earth’s umbra during an eclipse —you can gauge your relative longitude east or west of the point. The sky moves 15 degrees, or one hour of right ascension overhead as we rotate under it. One of the earliest records of this method comes to us from Ptolemy, who deduced Alexander the Great’s position 30 degrees (2 hours) east of Carthage during the lunar eclipse of September 20^th, 331 B.C. Alexander noted that the eclipse began two hours after sunset from his locale, while in Carthage it was recorded that the eclipse began at sunset.

A Jacob's crossstaff, a simple tool for measuring angles in the sky. (Photo by Author). — A Jacob’s cross staff, a simple tool for measuring angles in the sky. (Charles Towne Landing Historic Site Museum, Photo by Author).

Columbus was a student of Ptolemy, and used this method during voyages to and from the New World during the lunar eclipses of September 14^th, 1494 and February 29, 1504. Of course, such a method is only approximate. The umbra of the Earth often appears ragged and indistinct on the edge of the lunar disk at the start of an eclipse, making it tough to judge the actual beginning of an eclipse by more than ten of minutes or so. And remember, you’re often watching from the pitching deck of a ship to boot!

Another problem also plagued Columbus’s navigation efforts: he favored a smaller Earth than we now know is reality. Had he listened to another Greek astronomer by the name of Eratosthenes, he would’ve gotten his measurements pretty darned close.

An eclipse also saved Columbus’s butt on one occasion. The story goes that tensions had come to a head between the locals and Columbus’s crew while stranded on the island of Jamaica in 1504. Noting that a lunar eclipse was about to occur on March 1^st (the evening of February 29th for North America), Columbus told the local leader that the Moon would rise “inflamed with wrath,” as indeed it did that night, right on schedule. Columbus then made a great show of pretending to pray for heavenly intersession, after which the Moon returned to its rightful color. This kept a conniving Columbus and his crew stocked in supplies until a rescue ship arrived in June of that year.

A depiction of the 1504 lunar eclipse from the 1879 text Astronomie Populare by Camille Flammarion. — A depiction of the 1504 lunar eclipse from the 1879 text *Astronomie Populare* by Camille Flammarion.

Be sure to check out this Friday’s penumbral eclipse, and amaze your friends with the prediction of the next total lunar eclipse which occurs on U.S. Tax Day next year on April 15^th, 2014. Can you do a better job of predicting your longitude than Columbus?