Astro-Challenge: Watch the Moon Occult Venus in the Daytime

The Moon meets Venus on February 26th, 2014. Image credit and copyright: Konstantinos Spanos

The year 2015 saved one of the best astronomical events for last, as the waning crescent Moon occults (passes in front of) the planet Venus as seen from North America on Monday, December 7th.

This is the final of seven naked eye occultations of planets by the Moon in 2015, three of which involve Venus. It’s also the best of the year, well positioned for North America. Continue reading “Astro-Challenge: Watch the Moon Occult Venus in the Daytime”

The Moon Greets the Planets in the November Dawn

So, did this past weekend’s shift back to Standard Time for most of North America throw you for a loop? Coming the day after Halloween, 2015 was the earliest we can now shift back off Daylight Saving Time. Sunday won’t fall on November 1st again until 2020. Expect evenings get darker sooner for northern hemisphere residents, while the planetary action remains in the dawn sky.

Though Mercury has exited the morning twilight stage, the planets Jupiter, Venus and Mars continue to put on a fine show, joined by the waning crescent Moon later this week. The action starts today on November 3rd, which finds +1.9 magnitude Mars passing just 0.68 degrees (40’, just over the apparent diameter of a Full Moon) from brilliant -3.9 magnitude Venus. Though the two nearest planets to the Earth appear to meet up in the dawn sky, Mars is actually 2.5 times more distant than Venus, which sits 74.4 million miles (124 million kilometres) from the Earth. Venus exhibits a 57% illuminated gibbous phase 21” across this week, versus Mars’ paltry 4.5” disc.

November 6th. Image credit: Starry Night Education Software
The lunar planetary lineup on the morning of November 6th… Image credit: Starry Night Education Software

Watch the scene shift, as the Moon joins the dance this weekend. The mornings of Friday, November 6th and Saturday, November 7th are key, as the Moon passes just two degrees from the Jupiter and Mars pair and just over one degree from Venus worldwide. Similar close pairings of the Moon and Venus adorn many national flags, possibly inspired by a close grouping of Venus and the Moon witnessed by skywatchers of yore.

November 7th
… and the view the next morning on November 7th. Image credit: Starry Night Education software

Saturday November 7th is also a fine time to try your hand at seeing Venus in the daytime, using the nearby crescent Moon as a guide. The Moon will be only four days from New, and the pair will be 46 degrees west of the Sun, an optimal situation as Venus just passed greatest western elongation 46.4 degrees west of the Sun on October 26th.

Nov 3
Mars meets Venus on November 3rd-4th… the center circle = 1 degree FoV. Image credit: Stellarium

Though Venus may seem like a difficult daytime object, it’s actually intrinsically brighter than the Moon per square arc second. Difficulty finding it stems from seeing it against a low contrast blue daytime sky, its small size, and lack of context and depth. The larger but dimmer Moon actually serves as a good anchor to complete this feat of visual athletics.

Venus from the morning of November 3rd. Image credit and copyright: Shahrin Ahmad
Venus from the morning of November 3rd. Image credit and copyright: Shahrin Ahmad

Looking for more? Comet C/2013 US10 Catalina will join the planetary lineup next lunation ‘round, hopefully shining at magnitude +5 as it glides past Venus and the Moon on December 7th. Karl Battams at the U.S. Naval Research Labs has confirmed that Comet US10 Catalina—which reaches perihelion this month on November 15th –should also briefly graze the field of view for SOHO’s LASCO C3 camera on November 7th.

There’s also a few notable lunar occultations this week. The Moon also occults the +5 magnitude star Chi Leonis for viewers around the Gulf of Mexico on November 4th, including a dramatic grazing event for Northern Florida. The Moon also occults the +3.5 magnitude star Omicron Leonis on Nov 4th for Alaska as well.

Image credit:
The occultation footprint for Chi Leonis. The solid lines indicate where the event will occur during darkness and twilight hours, while the dashed lines denote where the event transpires during the daytime. Image credit: Occult 4.2 software

See a bright star near the Venus this week? It’s none other than +3.6 magnitude Beta Virginis (Zavijava). The star passes 15’ from Venus on the morning of November 6th. Stick around ‘til 2069, and you can actually witness Venus occult Beta Virginis. Between Beta Virginis and Mars, Venus has the appearance this week of having the large pseudo-moon it never possessed. From Venus, our Moon would appear near magnitude +0.4 with a disk 6.4” this week, and range 12’ from the Earth.

Nov 7
The closeup view on the morning of November 7th along with a 5 degree Telrad FoV. image credit: Stellarium

Now for the wow factor. All of these disparate objects merely lie along our Earthbound line of sight this week. Traveling at the speed of light (186,282 miles or 299,792 kilometers a second), the Moon lies just over a second away. Venus, Mars and Jupiter are next, at 6, 18, and 49 light minutes out, respectively… and Beta Virginis? It lies 36 light years distant.

This pass of the Moon also sets us up for an occultation of Mars and a dramatic daytime occultation of Venus for North America during the next lunation…

More to come!

-Got pictures of the planetary grouping this week with the Moon? Be sure to send ’em in to Universe Today and our Flickr forum.

Can Lunar Earthshine Reveal Ashen Light on Venus?

A recent celestial event provided a fascinating look at a long-standing astronomical mystery.

Is the ‘ashen light of Venus’ a real phenomena or an illusion?

On October 8th, the waning crescent Moon occulted (passed in front of) the bright planet Venus for observers in the southern hemisphere. And while such occurrences aren’t at all rare—the Moon occults Venus 3 times in 2015, and 25 times in this decade alone worldwide—the particulars were exceptional for observers in Australia, with a -4.5 magnitude, 40% illuminated Venus 30” in size emerging under dark skies 45 degrees west of the Sun from behind the dark limb of the Moon.

David and Joan Dunham rose to the challenge, and caught an amazing sequence featuring a brilliant Venus reappearing from behind the Moon as seen from the Australian Outback. When I first watched the video posted on You Tube by International Occultation Timing Association (IOTA) North American coordinator Brad Timerson, I was a bit perplexed, until I realized we were actually seeing the dark nighttime side of a waning Moon, with the bright crescent just out of view. Venus fully emerges in just under a minute after first appearing, and its -4th magnitude visage shines like a spotlight when revealed in its full glory.

Image credit:
A simulation of Venus on the limb of the Moon on October 8th. Image credit: Stellarium

“Joan and I observed the reappearance of Venus from behind the dark side of the 15% sunlit waning crescent Moon, from a dark and wide parking area on the east side of the Stuart Highway that afforded a low (1-2 degree) horizon to the east,” Dunham said. “Since the past observations of ashen light were visual, I decided that it would be best to use the 25mm eyepiece with the 8-inch visually rather than just make a redundant video. Neither the real-time visual observation, nor close visual inspection of the video recording, showed any sign of the dark side of Venus.”

Image credit:
Dunham’s ‘box scope’ imaging set up Image credit: David Dunham

We’ve written about the strange puzzle of ashen light on the nighttime side of Venus previously.

Reports by visual observers of ashen light on the dark limb of Venus over the centuries remain a mystery. On the crescent Moon, it’s easy to explain, as the Earth illuminates the nighttime side of our natural satellite; no such nearby illumination source exists in the case of Venus. Ashen light on Venus is either an illusion—a trick of the dazzling brilliance of a crescent Venus fooling the eye of the observer—or a real, and not as yet fully described phenomenon. Over the years, suggestions have included: lightning, airglow, volcanism, and aurora. A good prime candidate in the form of an ‘auroral nightglow” was proposed by New Mexico State University researchers in 2014. 19th century astronomers even proposed we might be seeing the lights of Venusian cities, or perhaps forest fires!

Could we ever separate the bright crescent of Venus from its nighttime side? A lunar occultation, such as the October 8th event provides just such a fleeting opportunity.  Though it’s hard to discern in the video, Dunham also watched the event visually through the telescope, and noted that, in his words, “the dark side of Venus remains dark,” with no brief appearance prior to sighting the crescent shining through the lunar valleys.

A tentative light curve made by Mr. Timerson seems to support this assertion, as the appearance of Venus quickly over-saturates the view:

Image credit
A rough light curve of the event. Photon counts are along the vertical axis, each tick mark along the horizontal equals one second. Image credit: Brad Timerson

Of course, this is far from conclusive, but seems to support the idea that the ashen light of Venus noted by ground observers is largely an optical illusion. Not all occultations of Venus by the Moon are created equal, and the best ones to test this method occur when Venus is less than half illuminated and greater than 40 degrees from the Sun against a relatively dark sky. Compounding problems, the ‘dark’ limb of the Moon has a brightness of its own, thanks to Earthshine. Dunham notes that observers in southern Alaska may have another shot at seeing this same phenomenon on December 7th, when the 13% illuminated crescent Moon occults a -4.2 magnitude 69% illuminated Venus, 42 degrees west of the Sun… the rest of North and South America will see this occultation in the daytime, still an interesting catch.

Image credit
The occultation footprint for the Dec 7 event. The dashed lines indicate where the event happens during daylight. Image credit: Occult 4.1

Looking at future occultations, there’s an intriguing possibility to hunt for the ashen light on the evening of October 10th, 2029, when then Moon occults a 57% illuminated Venus against dark skies for observers along the U.S. West Coast. Incidentally, a dawn occultation provides a better circumstance than a dusk one, as Venus always reemerges from the Moon’s dark limb when it’s waning. It enters the same when waxing, perhaps allowing for observer bias.

Image credit:
A simulation of the 2029 event. Image credit: Stellarium

Can’t wait for December? The Moon also occults the bright star Aldebaran on October 29th for Europe and North America on November 26th near Full phase… the good folks at the Virtual Telescope will carry the October event live.

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The occultation footprint for the 2029 event. Image credit: Occult 4.1

For now, the ashen light of Venus remains an intriguing mystery. Perhaps, an airborne observation could extend the appearance of Venus during an occultation, or maybe the recently announced Discovery-class mission to Venus could observe the night side of the planet for an Earthly glow… if nothing else, it’s simply amazing to watch the two brightest objects in the nighttime sky come together.

Challenge-Watch the Daytime Moon Occult Aldebaran for North America This Friday

How about that total lunar eclipse this past Sunday? Keep an eye of the waning gibbous Moon this week, as it begins a dramatic dive across the ecliptic towards a series of photogenic conjunctions throughout October.

The Main Event: This week’s highlight is an occultation of the bright +0.9 magnitude star Aldebaran (Alpha Tauri) by the waning gibbous Moon on Friday morning October 2nd.

Image credit: Occult 4.0 software
The occultation footprint for Friday’s occultation of Aldebaran by the Moon, with pre-dawn, dawn and post-dawn zones annotated. Image credit: Occult 4.0 software

This occurs in the pre-dawn hours for Alaskan residents, and under favorable dawn twilight skies along the U.S. and Canadian Pacific west coast; the remainder of the contiguous United States and Canada will see the occultation transpire after sunrise.   This is the 10th of 49 occultations of Aldebaran by the Moon worldwide running from January 29th, 2015 through September 3rd, 2018. The Moon will be at 74% waning gibbous phase, and Aldebaran will disappear behind its illuminated limb to reappear from behind its trailing dark limb.

Check out this amazing Vine of the last occultation of Aldebaran by the Moon courtesy of Andrew Symes @FailedProtostar:

It’s interesting to note that the southern graze-line for the occultation roughly follows the U.S./Mexican border. Seeing a bright star wink in and out from behind the lunar valleys can be an unforgettable sight, adding an eerie 3D perspective to the view. A detailed analysis of the event can even help model the rugged limb of the Moon.

Hunting stars and planets in the daytime can be an interesting feat of visual athletics. We’ve managed to spy Aldebaran near the lunar limb with binoculars during an occultation witnessed from Alaska on September 4th, 1996, and can attest that it’s quite possible to see a +1st magnitude star near the Moon with optical aid. A clear blue sky is key.  The Greek philosopher Thales noted that stars could be seen from the bottom of a well (though perhaps he’d fallen down a well or two too many in his time)… Friday’s event should push your local seeing to its limits. Start tracking Aldebaran before local sunrise, and you should be able to follow it all the way to the lunar limb, clear skies willing.

Image credit: Dave Dickinson/Stellarium
The occultation path for various locales across the United States Friday morning. Image credit: Dave Dickinson/Stellarium

Here’s a listing of times for key events for Friday from around the U.S. Check out The International Occultation Timing Association’s page for the event for an extensive listing:

Image credit: Dave Dickinson
Key times for the occultation for the same locales depicted in the graphic above, along with the lunar elevation (altitude) above the local horizon at the time noted. Image credit: Dave Dickinson

And whenever the Moon meets Aldebaran, it has to cross the open star cluster of the Hyades to get there, meaning there’ll be many other worthy occultations of moderately bright stars around October 2nd as well.  Gamma Tauri, 75 Tauri, Theta^1 Tauri, and SAO93975 are all occulted by the Moon on the morning of October 2nd leading up to the Aldebaran occultation; particularly intriguing is the grazing occultation of +5 magnitude 75 Tauri across the Florida peninsula.

The path of the moon through the Hyades this weekend. Image credit: Starry Night Education software
The path of the Moon through the Hyades this weekend. Image credit: Starry Night Education software

Fun fact: the Moon can, on occasion, occult members of the M45 Pleiades star cluster as well, as last occurred in 2010, and will next occur on 2023.

Chasing the Moon through October

Follow that Moon for the following dates with astronomical destiny worldwide:

  • The Moon reaches Last Quarter phase on Sunday, October 4th at 21:06 UT/5:06 PM EDT.
  • A close pass with Venus on October 8th, with a brilliant occultation visible in the pre-dawn hours from Australia.
  • A tight photogenic grouping of the Moon, Mars and Jupiter in a four degree circle on the morning on October 9th;
  • A close pass of the Moon just 36 hours from New near Mercury on the morning of Sunday, October 11th, with another occultation of the planet visible from Chile at dawn;
  • And finally, New Moon (sans eclipse, this time) occurring at 00:06 UT on October 13th, marking the start of lunation 1148.

Why occultations? Consider the wow factor; light from Aldebaran left about 65 years ago, before the start of the Space Age, only to get ‘photobombed’ by the occulting Moon at the last moment. Four bright stars (Regulus, Spica, Antares and Aldebaran) lie along the Moon’s path in our current epoch. Dial the celestial scene back about two millennia ago, and the Moon was also capable of occulting the bright star Pollux in the astronomical constellation of Gemini as well.

We’ll be running video for the event clear skies willing Friday morning here from Hudson, Florida in the Tampa Bay area. And as always, let us know of your tales of astronomical tribulation and triumph!

Catch Mercury Brushing Past Venus in a Spectacular Dusk ‘Quasi-Conjunction’ This Week

Missing Venus? The third brightest natural object in the heavens returns to prime time dusk skies in 2015 after being absent and lingering in the dawn for most of 2014. But there’s another reason to hunt down the Cytherean world this week, as elusive Mercury chases after it low in the dusk. If you’ve never seen Mercury for yourself, now is a great time to try, using brilliant Venus as a guide.

The circumstances surrounding this pairing are intriguing. We have to admit, we missed this close conjunction whilst filtering through research for the Top 101 Astronomical Events for 2015 due to those very same unique attributes until an astute reader of Universe Today pointed it out.

December 31st Bob King
Venus and Mercury setting over the Duluth, Minnesota skyline on December 31st. Credit and copyright: Bob King.

On the evening of January 5th, Venus shines at magnitude -3.3 and sits about 18 degrees east of the Sun in dusk skies.  You’ll have a narrow window of opportunity to nab Venus, as it’ll sit only 10 degrees above the southwestern horizon as seen from latitude 40 degrees north about an hour after sunset. Make sure you have a clear, uncluttered horizon, and start sweeping the field with binoculars about half an hour after sunset.

Do you see a tiny point of light about a degree and a half to Venus’s lower right? That’s Mercury, just beginning its first dusk apparition of seven for 2015, the most possible in a calendar year. Shining at -0.7 magnitude, Mercury is currently about 8 times fainter than Venus, and drops to +1.4 magnitude by late January.

If you watch the pair on successive evenings, you’ll see Mercury — aptly named after the fleet-footed Roman god — racing to rapidly close the gap. Mercury crosses the one degree separation threshold from January 8th through January 12th, and sits just 39’ — slightly larger than the apparent size of the Full Moon — right around 7:00 PM EST/Midnight Universal Time on January 10th, favoring dusk along eastern North America just a few hours prior.

Credit Jose
Venus and Mercury as seen from Venezuela on January 2nd. Credit and copyright: Jose Rozada.

This also means that you’ll be able to squeeze both Mercury and Venus into the same low power telescopic field of view. They’ll both even show the same approximate gibbous phase, with Venus presenting a 10.5” sized 95% illuminated disk, and Mercury subtending 6” in apparent diameter with a 74% illuminated visage. Venus will seem to be doing its very own mocking impersonation of the Earth, appearing to have a single large moon… Neith, the spurious pseudo-moon of Venus lives!

One curious facet of this week’s conjunction is the fact that Venus and Mercury approach, but never quite meet each other in right ascension. We call such a near miss a “quasi-conjunction.” This is the closest pairing of Venus and Mercury since 2012, though you have to go all the way back to 2005 for one that was easily observable, and the last true quasi-conjunction was in October 2001. Miss this week’s event, and you’ll have to wait until May 13th 2016 to catch Mercury — fresh off of transiting the Sun a week earlier — passing just 26’ from Venus only 6.5 degrees west of the Sun. This is unobservable from your backyard, but SOHO’s LASCO C3 camera’s 15 degree wide field of view will have a front row cyber-seat.

Venus 2015
The dusk path of Venus through early 2015. Credit: Starry Night Education software.

In 2015, Venus will become ever more prominent in the dusk sky before reaching greatest elongation 45.4 degrees east of the Sun on June 6th, 2015. The angle of the January ecliptic at dusk is currently shoving Mercury and Venus southward for northern hemisphere observers, though that’ll change dramatically as we head towards the March equinox. Venus reaches solar conjunction sans transit (which last occurred in 2012 and won’t happen again til 2117 A.D.) on August 15th before heading towards its second elongation of 2015 on October 26th in the dawn sky.  And don’t forget, it’s possible to see Venus in the daytime as it approaches greatest elongation. Venus is also occulted by the Moon 4 times in 2015, including a fine daytime occultation on December 7th for North America.

Mercury through January 2015.
The path of Mercury through January 2015. Credit: Starry Night Education software.

This month, Mercury reaches greatest eastern elongation on January 14th at 18.9 degrees east of the Sun.  Mercury begins retrograde movement later this month — one of the prime reasons this week’s conjunction is quasi — before resuming direct (eastward) motion as seen from our terrestrial vantage point. Though it may seem convenient to blame your earthly woes on Mercury in retrograde as astrologers will have you believe, this is just an illusion of planetary orbital motion. And speaking of motion, Mercury transits the Sun next year on May 9th.

John Barantine
Venus and Mercury as seen from Tucson, Arizona on January 3rd. Credit and copyright: John Barentine (@JohnBarentine)

Mercury and Venus factor in to space exploration in 2015 as well. NASA’s MESSENGER spacecraft wraps up its successful mission  in orbit around Mercury in a few months, and the Japanese Space Agency takes another crack at putting its Akatsuki spacecraft in orbit around Venus this coming November.

So don’t fear the bone-chilling January temps (or Mercury in retrograde) but do get out there these coming evenings and check out the fine celestial waltz being performed by the solar system’s two innermost worlds.

 

Spectacular Views of Venus and the “Decrescent” Moon Worldwide

Did you see it? Earlier this week, we wrote about the spectacular conjunction of the planet Venus and the waning crescent Moon this week, which culminated in a fine occultation of the planet by our large natural satellite on Wednesday morning. The footprint of the occultation crossed northern Africa in the predawn hours to greet daytime observers across southern Asia. And although the pass was a near miss for many, viewers worldwide were treated to a fine photogenic pairing of Venus and the Moon.

Credit: SculptorLil
An “aircraft/Moon/Venus tri-conjunction” captured February 26th from London, UK. Credit: Sculptor Lil

This was a highlight event of the 2014 dawn apparition of Venus, and some great pics have been pouring in to us here at Universe Today via Twitter, Google+ and our Flickr pool. We also learned a new word this week while immersed in astronomical research: a decrescent Moon.  We first thought this was a typo when we came across it, but discovered that it stands for a waning crescent Moon going from Last Quarter phase to New. Hey, it’s got a great ring to it, and its less characters than “waning crescent” and thus comes ready Tweet-able.

Credit: Gadi Eidelheit
Venus and the Moon in the predawn sky captured from Israel. Credit: Gadi Eidelheit @gadieid

Some great video sequences have emerged as well, including this fine grazing sequence of a daytime crescent Venus brushing past the crescent Moon taken by Shahrin Ahmad:

Shahrin journeyed to the northern tip of Peninsular Malaysia to the town of Perlis near near the Thai border to capture the graze. “It was a really close event,” he noted. “Today, the clouds began to appear and posed some real tense moments during the occultation.”

And although many weren’t fortunate enough to be in the path of the occultation, many observers worldwide captured some very photogenic scenes of the conjunction between the Moon and Venus as the pair rose this morning, including this great video sequence from  Ryan Durnall:

And clear skies greeted a series of early morning astronomers worldwide, who shared these amazing images with us:

Brad Timerson
This morning’s conjunction as imaged from Newark, New York. Credit- Brad Timerson @btimerson
Venus and the Moon the day prior to the occultation, shot by Ken Lord from Maple Ridge, British Columbia. Credit- Ken Lord.
Venus and the Moon the day prior to the occultation, shot by Ken Lord from Maple Ridge, British Columbia. Credit- Ken Lord.
The Moon approaching Venus on February 25th as seen from Carbon County, Pennsylvania. Credit: Tom Wildoner.
The Moon approaching Venus on February 25th as seen from Carbon County, Pennsylvania. Credit: Tom Wildoner.
Venus and the Moon rising through the fog: Credit: Joanie Boloney @jstabila
Venus and the Moon rising through the fog: Credit: Joanie Boloney @jstabila

John Chumack was also up early this morning and was able to capture this fine image of the pair rising above the University of Dayton’s PAC Center:

Credit: John Chumack, www.galacticimages.com
Venus and the Moon as seen from Dayton, Ohio. Credit: John Chumack, www.galacticimages.com

“All I had available was a point and shoot camera (not even mine!)” Chumack told Universe Today. “I’m surprised it came out okay, considering all the ambient light on Campus!!!” Chumack used a Fujifilm Finepix S1000 point and shoot camera, and went sans tripod, doing a 2″ exposure with the camera perched atop a trash can. The results of this ad hoc setup look great!

Astrophotographer Giuseppe Petricca based in Pisa, Italy north of the occultation path also grabbed this outstanding closeup image of the crescent pair:

Credit: Giuseppe Petricca
Taken using a Nikon Coolpix P90 Bridge camera on a tripod mount. Credit: Giuseppe Petricca

“This morning was awesome!” Petricca told Universe Today. “The weather forecast showed a compact high layer of clouds, but there were enough gaps between them that allowed me to see the conjunction in a lot of different moments.”

You can compare and contrast the twin crescents of Venus and the Moon evident in the above image. “You can easily see the phase of the Planet Venus and a lot of details on the lunar surface, despite the high clouds that partially blocked the view sometimes!” Petricca noted.

And finally, I give you our own humble entry, a  conjunction over suburbia snapped pre-caffeination:

DSC_0584   We think its great that you can sometimes catch a memorable glimpse of the celestial even from your own doorstep.

And when is the next occultation of a planet by the Moon? That would be next month, when Saturn is occulted by the waxing gibbous Moon for South Africa and Brazil after sunset on March 21st, 2014. We’re in the midst of a cycle of occultations of the ringed planet by the Moon, occurring every lunation through the final one this year on October 25th.

The next occultation of Venus occurs on October 23rd 2014, but is only one degree from the Sun and is unobservable. The next observable event occurs on July 19th 2015 for northern Australia in the daytime, and for a remote stretch of the South Pacific at dusk.

And its still not too late to spy Venus in the daytime today, using the nearby Moon as a guide. Here’s a handy simulation to aid you in your quest generated for mid-noon, February 26th:

stellarium
The orientation of the Moon and Venus at ~17:00UT, including a five degree Telrad bullseye. Created by the author using Stellarium.

And finally here’s handy chart of maps of occultations of Venus by the Moon for the current decade, just click to enlarge:

Occult 4.0
Occultations of Venus by the Moon from 2011-2020. Created using Occult 4.0.

Enjoy!

Watch the Moon Meet Venus in the Dawn this Wednesday

Are you ready for some lunar versus planetary occultation action? One of the best events for 2014 occurs early this Wednesday morning on February 26th, when the waning crescent Moon — sometimes referred to as a decrescent Moon — meets up with a brilliant Venus in the dawn sky. This will be a showcase event for the ongoing 2014 dawn apparition of Venus that we wrote about recently.

This is one of 16 occultations of a planet by our Moon for 2014, which will hide every naked eye classical planet except Jupiter and only one of two involving Venus this year.

An occultation occurs when one celestial body passes in front of another, obscuring it from our line of sight. The term is used to refer to planets or asteroids blocking out distant stars or the Moon passing in front of stars or planets.

Wednesday’s event has a central conjunction time of 5:00 Universal. Viewers in northwestern Africa based in Mali and southern Algeria and surrounding nations will see the occultation occur in the dawn sky before sunrise, while viewers eastward across the Horn of Africa, the southern Arabian peninsula, India and southeast Asia will see the occultation occur in the daylight.

January 29th, 2014
A comparison of Venus versus the Moon in the daytime taken by Sharin Ahmad (@shahgazer) from Malaysia during the last lunation on January 29th, 2014.

Observers worldwide, including those based in Australia, Europe and the Americas will see a near miss, but early risers will still be rewarded with a brilliant dawn pairing of the second and third brightest objects in the night sky. This will also be a fine time to attempt to spot Venus in the daytime, using the nearby crescent Moon as a guide. It’s easier than you might think!  In fact, Venus is actually brighter than the Moon per apparent square arc second of surface area, owing to its higher average reflectivity (known as albedo) of 80% versus the Moon’s dusky 14%.

The International Occultation Timing Association also maintains a chart of ingress and egress times for specific locations along the track of the occultation.

Credit: Created using Occult 4.0.11.
The footprint of the Wednesday occultation of Venus by the Moon. Solid lines indicate where the occultation occurs before sunrise, while the dashed area denotes where the occultation occurs after sunrise. Credit: Created using Occult 4.1.0.11.

The Moon occults Venus 21 times in this decade. The last occultation of Venus by the Moon occurred on September 8th, 2013, and the next occurs October 23rd 2014 over the South Pacific in daylight skies very close to the Sun, and is unobservable.

Wednesday’s event also offers a unique opportunity to catch a crescent Venus emerging from behind the dark limb of the Moon. On Wednesday, Venus presents a 34” diameter disk that is 35% illuminated and shining at magnitude -4.3, while the Moon is a 12% illuminated crescent three days from New. Fun fact: February 2014 is missing a New Moon, meaning that both January and March will each contain two!

Apparent path of Venus in relation to the Moon
Apparent path of Venus in relation to the Moon Wednesday morning as seen from a theoretical geocentric (Earth-centered) location. Created using Starry Night Education software.

This also means that a well positioned observer in northwestern Africa would be able to see able to catch the dark limb of Venus creeping out from behind the nighttime side of the Moon against a dark sky. Such favorable occurrences only happen a handful of times per decade, and this week would be a great time to try and briefly spot – or perhaps even video or photograph – a phenomenon know as the ashen light of Venus as the dazzling crescent daytime side of the planet lay obscured by the Moon. Is this effect reported by observers over the years a fanciful illusion, or a real occurrence?

Perhaps, due to the remote location, this chance to spy and record this elusive effect will go unnoticed this time ‘round. The next chance with optimal possibilities to catch a crescent Venus occulted by the Moon against a dark sky occurs next year on October 8th, 2015, favoring the Australian outback. Anyone out there down for an observing expedition to prove or disprove the ashen light of Venus once and for all? Astronomy road trip!

Photo by Author
April 22nd, 2009 conjunction of Venus and the Moon as seen from Hudson, Florida. The Photo by author.

This event also provides optimal circumstances as Venus heads towards greatest elongation west of the Sun on March 22nd and the Moon-Venus pair lay 43 degrees west of the Sun during Wednesday’s event. Compare this to the impossible to observe occultation this October, when the pairing is only one degree east of the Sun! The next occultation of Venus for North America occurs next year on December 7th, 2015 and will be visible in the daytime across the extent of the track except for Alaska and Northwestern Canada.

Vexillographers may also want to take note: this week’s Venus-Moon pairing will closely emulate the familiar crescent Moon plus star pairing seen on many national flags worldwide. Did an ancient and unrecorded occultation of Venus by the Moon inspire this meme?   Tradition has it that Sultan Alp Arslan settled on the star and crescent for the flag of the Turks after witnessing a close conjunction after the defeat of the Byzantine Army at the Battle of Manzikert on August 26th, 1071 A.D. This tale, however, is almost certainly apocryphal, as no occultations of planets or bright stars by the Moon occurred on or near that date, and only two occultations of Venus by the Moon occurred that year. And Venus was less than two degrees from the Sun on that date, yet another strike against it. In fact, the only occultations of Venus by the Moon in 1071 occurred on June 29th and November 27th. Perhaps Arslan just took a while to decide…

Still, this week’s event provides a great photo-op to have “Fun with Flags” and capture the pair behind your favorite astronomical conjunction-depicting banner. And be sure to send those pics into Universe Today… methinks there’s a good chance of us running a post occultation photo-essay later this week!

A Challenging Series of Occultations of Spica by the Moon Coming to a Sky Near You

The first in a cycle of challenging occultations of the bright star Spica for northern hemisphere observers begins this coming Monday on August 12th.

Watching a bright star or planet wink out on the dark limb of the Moon can be an amazing event to witness. It’s an abrupt “now you see it, now you don’t” event in a universe which often seems to move at an otherwise glacial pace. And if the event grazes the limb of the Moon, an observer may see a series of winks as the starlight streams through the lunar valleys.

Close companion stars have been discovered during occultations, and astronomers even used a series of occultations of radio source 3C 273 in 1962 to pin down the position of the first quasar.

An occultation occurs when one object passes in front of another as seen from the observer’s vantage point. The term has its hoary roots back in a time when astronomy was intertwined with its pseudoscience ancestor of astrology. Even today, I still get funny looks from non-astronomy friends when I use the term occultation, as if it just confirms their suspicions of the arcane arts that astronomers really practice in secret.

But back to reality-based science. At an apparent magnitude of +1.1, Spica is the 3rd brightest star that the Moon can occult along its five degree path above and below the plane of the ecliptic. It’s also one of only four stars brighter than +1.4 magnitude on the Moon’s path. The others are Antares (magnitude +1.0), Regulus (magnitude +1.4), and Aldebaran (magnitude +0.8). All of these are bright enough to be visible on the lunar limb through binoculars or a telescope in the daytime if conditions are favorable.

It’s interesting to note that this situation also changes over time due to the precession of the equinoxes. For example, the bright star Pollux was last occulted by the Moon in 117 BC, but cannot be covered by the Moon in our current epoch.

Spica is currently in the midst of a cycle of 21 occultations by our Moon. This cycle started in July 25th, 2012 and will end in January 2014.

Spica is a B1 III-IV type star 10 times the mass of the Sun. At 260 light years distant, Spica is one of the closest candidates to the Earth along with Betelgeuse to go supernova. Now, THAT would make for an interesting occultation! Both are safely out of the ~100 light year distant “kill zone”.

What follows are the circumstances for the next four occultations of Spica by the Moon. The times are given for closest geocentric conjunction of the two objects. Actual times of disappearance and reappearance will vary depending on the observer’s location. Links are provided for each event which include more info.

Starry Night
Looking westward 30 minutes after sunset for North American viewers on the night of August 12th. (Created by the Author using Starry Night).

First up is the August 12th occultation of Spica, which favors Central Asia and the Asian Far East. This will occur late in the afternoon sky around 09:00 UT  and prior to sunset. The waxing crescent Moon will be six days past New phase. North American observers will see the Moon paired five degrees from Spica with Saturn to the upper left on the evening of August 12th.

Occult
The footprint for the September 8th occultation of Spica by the Moon. Note that the broken line indicates where the occultation will take place in the daytime sky. ( Credit: Occult 4.1.0.2)

Next is the September 8th daytime occultation of Spica for Europe, the Middle East and northern Africa around ~15UT. This will be a challenge, as the Moon will be a waxing crescent at only 3 days past New. Observers in the Middle East will have the best shot at this event, as the occultation occurs at dusk and before moonset. Note that the Moon also occults Venus six hours later for Argentina and Chile.

Stellarium
Looking to the east the morning of November 2nd for North American observers. (Created by the author using Stellarium).

After taking a break in October (the occultation of October 5 occurs only 23 hours after New and is unobservable), the Moon again occults Spica on November 2nd for observers across Europe & Central Asia. This will be a difficult one, as the Moon will be only 20 hours from New and a hybrid solar eclipse that will cross the Atlantic and central Africa. It may be possible to lock on to the Moon and track it up into the daylight, just be sure to physically block the rising Sun behind a building or hill!

USNO
The occultation footprint of Spica by the Moon for November 29th, 2013.  (Reproduced from the Astronomical Almanac online and produced by the U.S. Naval Observatory and H.M. Nautical Almanac Office).

Finally, the Moon will occult Spica for North American observers on November 29th centered on 17:03 UT. This will place the event low in the nighttime sky for Alaskan observers. It’ll be a bit more of a challenge for Canadian and U.S. observers in the lower 48, as the Moon & Spica will be sandwiched between the Sun and the western horizon in the mid-day sky. As an added treat, comet C/2012 S1 ISON will reach perihelion on November 28th, just 20 hours prior and will be reaching peak brilliance very near the Sun.

And as an added bonus, the Moon will be occulting the +2.8 star Alpha Librae (Zubenelgenubi) on August 13th for central South America.

All of these events are challenges, to be sure. Viewers worldwide will still catch a close night time pairing of the Moon and Spica on each pass. We’ve watched the daytime Moon occult Aldebaran with binoculars while stationed in Alaska back in the late 1990’s, and can attest that such a feat of visual athletics is indeed possible.

And speaking of which, the next bright star due for a series of occultations by the Moon is Aldebaran starting in 2015. After 2014, Spica won’t be occulted by the Moon again until 2024.

But wait, there’s more- the total eclipse of the Moon occurring on April 15th 2014 occurs just 1.5 degrees from Spica, favoring North America. This is the next good lunar eclipse for North American observers, and one of the best “Moon-star-eclipse” conjunctions for this century. Hey, at least it’ll give U.S. observers something besides Tax Day to look forward to in mid-April. More to come in 2014!