Watch Rotating Horns of Venus at Dawn

Venus inferior conjunction
Venus inferior conjunction
Venus just 10.5 hours before inferior conjunction on March 25th. Image credit and copyright: Shahrin Ahmad (@Shahgazer)

Have you seen it yet? An old friend greeted us on an early morning run yesterday as we could easily spy brilliant Venus in the dawn, just three days after inferior conjunction this past Saturday on March 25th.

This was an especially wide pass, as the planet crossed just over eight degrees (that’s 16 Full Moon diameters!) north of the Sun. We once managed to see Venus with the unaided eye on the very day of inferior conjunction back in 1998 from the high northern latitudes of the Chena Flood Channel just outside of Fairbanks, Alaska.

The planet was a slender 59.4” wide, 1% illuminated crescent during this past weekend’s passage, and the wide pass spurred many advanced imagers to hunt for the slim crescent in the daytime sky. Of course, such a feat is challenging near the dazzling daytime Sun. Safely blocking the Sun out of view and being able to precisely point your equipment is key in this endeavor. A deep blue, high contrast sky helps, as well. Still, many Universe Today readers rose to the challenge of chronicling the horns of the slender crescent Venus as they rotated ’round the limb and the nearby world moved once again from being a dusk to dawn object.

Venus rotating horns
A daily sequence showing the ‘Horns of Venus’ rotate as it approaches inferior conjunction. Image credit and copyright: Shahrin Ahmad (@ShahGazer)

The orbit of Venus is tilted 3.4 degrees with respect to the Earth, otherwise, we’d get a transit of the planet like we did on June 5-6th, 2012 once about every 584 days, instead of having to wait again until next century on December 10th, 2117.

The joint NASA/European Space Agency’s SOlar Heliospheric Observatory (SOHO) mission also spied the planet this past weekend as it just grazed the 15 degree wide field of view of its Sun-observing LASCO C3 camera:

Venus SOHO
The glow of Venus (arrowed) just barely bleeding over into the field of view of SOHO’s LASCO C3 camera. Credit: SOHO/NASA/LASCO

Venus kicks off April as a 58” wide, 3% illuminated crescent and ends the month at 37” wide, fattening up to 28% illumination. On closest approach, the planet presents the largest apparent planetary disk possible as seen from the Earth. Can you see the horns? They’re readily readily apparent even in a low power pair of hunting binoculars. The coming week is a great time to try and see a crescent Venus… with the naked eye. Such an observation is notoriously difficult, and right on the edge of possibility for those with keen eyesight.

One problem for seasoned observers is that we know beforehand that (spoiler alert) that the Horns of Venus, like the Moon, always point away from the direction of the Sun.

True Story: a five year old girl at a public star party once asked me “why does that ‘star’ look like a tiny Moon” (!) This was prior to looking at the planet through a telescope. Children generally have sharper eyes than adults, as the lenses of our corneas wear down and yellow from ultraviolet light exposure over the years.

Still, there are tantalizing historical records that suggest that ancient cultures such as the Babylonians knew something of the true crescent nature of Venus in pre-telescopic times as well.

The Babylonian frieze of Kudurru Melishipak on display at the Louvre, depicting the Sun Moon and Venus. According to some interpretations, the goddess Ishtar (Venus) is also associated with a crescent symbol… possibly lending credence to the assertion that ancient Babylonian astronomers knew something of the phases of the planet from direct observation. Credit: Wikimedia Commons/Image in the Public Domain.

Another fun challenge in the coming months is attempting to see Venus in the daytime. This is surprisingly easy, once you know exactly where to look for it. A nearby crescent Moon is handy, as occurs on April 23rd, May 22nd, and June 20th.

Daytime Venus
Venus (arrowed) near the daytime Moon. Photo by author.

Strangely enough, the Moon is actually darker than dazzling Venus in terms of surface albedo. The ghostly daytime Moon is just larger and easier to spot. Many historical ‘UFO’ sightings such as a ‘dazzling light seen near the daytime Moon’ by the startled residents of Saint-Denis, France on the morning on January 13th, 1589 were, in fact, said brilliant planet.

The Moon near Venus on May 22nd. Credit: Stellarium.

Venus can appear startlingly bright to even a seasoned observer. We’ve seen the planet rise as a shimmering ember against a deep dark twilight sky from high northern latitudes. Air traffic controllers have tried in vain to ‘hail’ Venus on more than one occasion, and India once nearly traded shots with China along its northern border in 2012, mistaking a bright conjunction of Jupiter and Venus for spy drones.

The third brightest object in the sky behind the Sun and the Moon, Venus is even bright enough to cast a shadow as seen from a dark sky site, something that can be more readily recorded photographically.

Watch our nearest planetary neighbor long enough, and it will nearly repeat the same pattern for a given apparition. This is known as the eight year cycle of Venus, and stems from the fact that 13 Venusian orbits (8x 224.8 days) very nearly equals eight Earth years.

Follow Venus through the dawn in 2017, and it will eventually form a right triangle with the Earth and the Sun on June 3rd, reaching what is known as greatest elongation. This can vary from 47.2 to 45.4 degrees from the Sun, and this year reaches 45.9 degrees elongation in June. The planet then reaches half phase known as dichotomy around this date, though observed versus theoretical dichotomy can vary by three days. The cause of this phenomenon is thought to be the refraction of light in Venus’ dense atmosphere, coupled with observer bias due to the brilliance of Venus itself. When do you see it?

Also, keep an eye out for the ghostly glow on the night-side of Venus, known as Ashen Light. Long thought to be another trick of the eye, there’s good evidence to suggest that this long reported effect actually has a physical basis, though Venus has no large reflecting moon nearby… how could this be? The leading candidate is now thought to be air-glow radiating from the cooling nighttime side of the planet.

Cloud enshrouded Venus held on to its secrets, right up until the Space Age less than a century ago… some observers theorized that the nighttime glow on Venus was due to aurorae, volcanoes or even light pollution from Venusian cities (!). This also fueled spurious sightings of the alleged Venusian moon Neith right up through the 19th century.

Venus should also put in a showing 34 degrees west of the Sun shining at magnitude -4 during the August 21st, 2017 total solar eclipse. Follow that planet, as it makes a complex meet up with Mars, Mercury, and the Moon in late September of this year.

More to come!

-Read about planets, occultations, comets and more for the year in our 101 Astronomical Events for 2017, out as a free e-book from Universe Today.

Venus Rules the Dusk Skies at Greatest Elongation

Venus at dusk
Venus at dusk
Venus, Mars, and the waxing crescent Moon at dusk from the evening of January 3rd, 2017. Image credit and copyright: Alan Dyer.

“What’s that bright light in the sky?” The planet Venus never fails to impress, and indeed makes even seasoned observers look twice at its unexpected brilliance. The third brightest natural object in the sky, Venus now rules the dusk, a fine sight for wintertime evening commuters. Venus reaches greatest elongation tomorrow, a excellent time to admire this dazzling but shrouded world of mystery.

Venus at greatest elongation

Only the two planets interior to Earth’s orbit – Mercury and Venus – can reach a point known as greatest elongation from the Sun. As the name suggests, this is simply the point at which either planet appears to be at its maximum angular distance from the Sun. Think of a big right triangle in space, with Venus or Mercury at the right angle vertex, and the Sun and Earth at the other two corners. High school geometry can come in handy!

Venus elongation
Venus at greatest elongation (planets and orbits not to scale). Credit: Dave Dickinson

This Thursday on January 12th Venus reaches a maximum of 47 degrees elongation from the Sun at 11:00 Universal Time (UT) / 6:00 AM Eastern Standard Time, shining at magnitude -4.4. The maximum/minimum elongation for Venus that can occur is 47.3 to 45.4 degrees respectively, and this week’s is the widest until 2025.

Here’s some key dates to watch out for:

Jan 12th: Venus passes less than a degree from Neptune.

Jan 14th: Venus reaches theoretical dichotomy?

Jan 14th: Venus passes 3′ from +3.7 the magnitude star Lambda Aquarii.

Jan 17th: Venus crosses the ecliptic plane northward.

Venus and Mars reach ‘quasi-conjunction’ in late January.

January 30th: Venus crosses the celestial equator northward.

January 31st: The Moon passes 4 degrees south of Venus, and the two also form a nice equilateral triangle with Mars on the same date.

Looking west on the evening of January 31st, 2017. Image credit: Stellarium.

February 17th: Venus reaches a maximum brilliancy of magnitude -4.6.

March 26th: Solar conjunction for Venus occurs eight degrees north of the Sun … it is possible to spy Venus at solar conjunction from high northern latitudes, just be sure to block out the Sun.

Through the telescope, Venus displays a tiny 24.4” size half phase right around greatest elongation. You could stack 74 Venuses across the diameter of tomorrow’s Full Moon. When does Venus look to reach an exact half phase to you? This point, known as theoretical dichotomy, is often off by just a few days. This is a curious observed phenomenon, first noted by German amateur astronomer Johann Schröter in 1793. The effect now bears his name. A result of atmospheric refraction along the day/terminator on Venus, or an optical illusion?

Gibbous Venus
Almost there… a waning gibbous Venus from the evening of January 5th, 2017. Image credit and copyright: Shahrin Ahmad (@Shahgazer)

And hey, amateurs are now using ultraviolet filters to get actual detail on the cloud-tops of Venus… we like to use a variable polarizing filter to cut down the dazzling glare of Venus a bit at the eyepiece.

Also, keep an eye out for another strange phenomenon, known as the Ashen Light of Venus. Now,ashen light or Earthshine is readily apparent on dark side of the Moon, owing to the presence of a large sunlight reflector nearby, namely the Earth. Venus has no such large partner, though astronomers in the early age of telescopic astronomy claimed to have spied a moon of Venus, and even went as far as naming it Neith. An optical illusion? Or real evidence of Venusian sky glow on its nighttime side? After tomorrow, Venus will begin heading between the Earth and the Sun, becoming a slender crescent in the process. Solar conjunction occurs on March 25th, 2017. Venus sits just eight degrees north of the Sun on this date, and viewers in high Arctic latitudes might just be able to spy Venus above the horizon before sunrise on the day of solar conjunction. We performed a similar feat of visual athletics on the morning of January 16th, 1998 observing from North Pole, Alaska.

Venus as seen from Fairbanks, Alaska on the morning of solar conjunction, 2017. Image credit: Starry Night.

From there, Venus heads towards a fine dawn elongation on June 3rd, 2017. All of these events and more are detailed in our free e-book: 101 Astronomical Events for 2017.

Spying Venus in the Daytime

Did you know: you can actually see Venus in the daytime, if you know exactly where to look for it? A deep blue, high contrast sky is the key, and a nearby crescent Moon is handy in your daytime quest. Strange but true fact: Venus is actually brighter than the Moon per square arc second, with a shiny albedo of 70% versus the Moon’s paltry 12%. But Venus is tiny, and hard to spot against the blue daytime sky… until you catch sight of it.

The Moon passing Venus on January 31st, 2017 in the daytime sky. Image credit: Stellarium.

There’s another reason to brave the January cold for northern hemisphere residents: Venus can indeed cast a shadow if you look carefully for it. You’ll need to be away from any other light sources (including the Moon, which passes Full tomorrow as well with the first Full Moon of 2017, known as a Full Wolf Moon). And a high contrast surface such as freshly fallen snow can help… a short time exposure shot can even bring the shadow cast by Venus into focus.

If you follow Venus long enough, you’ll notice a pattern, as it visits very nearly the the same sky environs every eight years and traces out approximately the same path in the dawn and dusk sky. There’s a reason for this: 8 Earth years (8x 365.25 = 2922 days) very nearly equals 5 the synodic periods for Venus (2922/5=584 days, the number of days it takes Venus to return to roughly the same point with respect to the starry background, separate from its true orbit around the Sun of 225 days). For example, Venus last crossed the Pleiades star cluster in 2012, and will do so again in – you guessed it — in 2020. Unfortunately, this pattern isn’t precise, and Venus won’t also transit the Sun again in 2020 like it did in 2012. You’ll have to wait until one century from this year on December 10-11th, 2117 to see that celestial spectacle again….

Hopefully, we’ll have perfected that whole Futurama head-in-a-jar thing by then.

Catch a Fine Lunar Planetary Grouping This Weekend

Phew! Our eyes and thoughts have been cast so far out into the outer reaches of the solar system following New Horizons and Pluto this week, that we’re just now getting to the astronomical action going on in our own backyard.

You’ll recall that Venus and Jupiter have made a fine pairing in the evening sky since their close approach on July 1st. Despite some of the incredulous ‘Star of Bethlehem’ claims that this was a conjunction that happens ‘once every two thousand years,’ this sort of pairing is actually quite common. In fact, Venus and Jupiter are set to meet up again in the dawn sky later this year on October 25th. Continue reading “Catch a Fine Lunar Planetary Grouping This Weekend”

Two Observing Challenges: Catch Venus Passing Neptune And Occulting a Bright Star

 Have you been following the planet Venus this season? 2014 sees the brightest planet in our Earthly skies spend a majority of its time in the dawn. Shining at magnitude -3.8, it’s hard to miss in the morning twilight. But dazzling Venus is visiting two unique celestial objects over the next week, and both present unique observing challenges for the seasoned observer.

First up is an interesting close conjunction of the planets Venus and Neptune on the morning of Saturday, April 12th. Closest conjunction occurs at 3:00 Universal Time (UT) April 12th favoring Eastern Europe, the Middle East and eastern Africa, when the two worlds appear to be just 40 arc minutes apart, a little over – by about 10’ – the apparent size of a full Moon. Shining at magnitude +7.8 and 30,000 times fainter than Venus, you’ll need a telescope to tease out Neptune from the pre-dawn sky. Both objects will, however, easily fit in a one degree field of view, in addition to a scattering of other stars.

Stellarium
Looking to the east the morning of April 12th from the U.S. East Coast near latitude 30 degrees north.  Nearby stars are annotated in red by magnitude with decimals omitted. Created using Stellarium, click to enlarge.

At low power, Venus will display a 59% illuminated gibbous phase 20” across on the morning of the 12th, while Neptune will show a tiny disk barely 2” across. Still, this represents the first chance for viewers to recover Neptune since solar conjunction behind the Sun on February 23rd, 2014, using dazzling Venus as a guide.

Both sit 45 degrees west of the Sun and currently rise around 3 to 4 AM local dependent on latitude.

This is one of the closest planet-planet conjunctions for 2014. The closest is Venus and Jupiter at just 0.2 degrees apart on August 18th. This will represent the brightest planet versus planet conjunction for the year, and is sure to illicit multiple “what’s those two bright stars in the sky?” queries from morning commuters… hopefully, such sightings won’t result in any border skirmishes worldwide.

Now, for the mandatory Wow factor. On the date of conjunction, Earth-sized Venus is 0.84 Astronomical Units (A.U.s) or over 130 million kilometres distant. Ice giant Neptune, however, is 30.7 AUs or 36 times as distant, and only appears tiny though it’s almost four times larger in diameter.  Sunlight reflected from Venus takes 7 minutes to reach Earth, but over four hours to arrive from Neptune. We’ve visited Venus lots, and the Russians have even landed there and returned images from its smoldering surface, but we’ve only visited Neptune once, during a brief flyby of Voyager 2 in 1989.

From Neptune looking back on April 12th, Earth and Venus would appear less than 1 arc minute apart…. though they’d also be just over one degree from the Sun!

The "shadow path" of the occultation of Lambda Aquarii by Venus on April 16th. Credit: IOTA/Steve Preston/www.asteroidoccultation/Occult 4.0.
The “shadow path” of the occultation of Lambda Aquarii by Venus on April 16th. Credit: IOTA/Steve Preston/www.asteroidoccultation/Occult 4.0.

But an even more bizarre event happens a few days later on April 16th, though only a small region of the world in the South Pacific may bare witness to it.

Next Wednesday from 17:59 to 18:13 UT Venus occults the +3.7 magnitude star HIP 112961 also known as Lambda Aquarii on the morning of April 16th 2014.

Venus will be a 61% illuminated gibbous phase 19” in diameter. Unfortunately, although North America is rotated towards the event, it’s also in the middle of the day.

The best prospects to observe the occultation are from New Zealand and western Pacific at dawn. The star will disappear behind the bright limb of Venus in dawn twilight before emerging on its dark limb 5 minutes later as seen from New Zealand.

Starry Night
The path of Lambda Aquarii behind Venus as seen from New Zealand the morning of the 16th. Created in Starry Night.

Note: New Zealand switched back to standard time on April 6th – it’s currently Fall down under – and local sunrise occurs around ~7:40 AM.

Lambda Aquarii is a 3.6 solar mass star located 390 light years distant. As far as we know, it’s a solitary star, though there’s always a chance that a companion could make itself known as it emerges on the dark limb of Venus. Such an observation will, however, be extremely difficult, as Venus is still over 700 times brighter than the star!

North Americans get to see the pair only 20’ apart on the morning of the 12th.

Starry Night
One degree fields of view worldwide showing Venus and Lambda Aquarii at 7AM local. Credit: Starry Night.

And further occultation adventures await Venus in the 21st century. On October 1st, 2044 it will occult Regulus… and on November 22nd, 2065 it will actually occult Jupiter!

Such pairings give us a chance to image Venus with a “pseudo-moon.” Early telescopic observers made numerous sightings of a supposed Moon of Venus, and the hypothetical object even merited the name Neith for a brief time. Such sightings were most likely spurious internal reflections due to poor optics or nearby stars, but its fun to wonder what those observers of old might’ve seen.

… and speaking of moons, don’t miss a chance to see Venus near the daytime Moon April 25th. Follow us as @Astroguyz on Twitter as we give shout outs to these and other strange pairings daily!

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!

Astro-Challenge: Nabbing Venus… at Inferior Conjunction

Residents of high northern latitudes can take heart this frigid January: this coming weekend offers a chance to replicate a unique astronomical sighting.

Veteran sky watcher Bob King recently wrote a post for Universe Today describing what observers can expect from the planet Venus for the last few weeks of this current evening apparition leading  up to Venus’s passage between the Earth and the Sun on January 11th. Like so many other readers, we’ve been holding a nightly vigil to see when the last date will be that we can spot the fleeing world… and some great pics have been pouring in.

But did you know that when the conditions are just right, that you can actually spy Venus at the moment of inferior conjunction?

No, we’re not talking about a rare transit of Venus as last occurred on June 6th, 2012, when Venus crossed the disk of the Sun as seen from our Earthly perspective… you’ll have to wait until 2117 to see that occur again. What we’re talking about is a passage of Venus high above or below the solar disk, when spying it while the Sun sits just below the horizon might just be possible.

The disk of Venus at inferior conjunction. Simulation created by the author using Starry Night.
The disk of Venus at inferior conjunction. Simulation created by the author using Stellarium.

Not all inferior conjunctions of Venus are created equal. The planet’s orbit is tilted 3 degrees with respect to our own and can thus pass a maximum of eight degrees north or south of the Sun. Venus last did this on inferior conjunction in 2009 and will once again pass a maximum distance north of the Sun in 2017. For the southern hemisphere, the red letter years are 2007, and next year in 2015.

You’ll note that the above periods mark out an 8-year cycle, a period after which a roughly similar apparition of the planet Venus repeats. This is because Venus takes just over 224 days to complete one orbit, and 13 orbits of Venus very nearly equals 8 Earth years.

And while said northern maximum is still three years away, this week’s inferior conjunction is close at five degrees from the solar limb. The best prospects to see Venus at or near inferior conjunction occur for observers “North of the 60”. We accomplished this feat two Venusian 8-year cycles ago during the inferior conjunction of January 16th, 1998 from latitude 65 degrees north just outside of Fairbanks, Alaska. We set up on the Chena Flood Channel, assuring as low and as flat a horizon as possible… and we kept the engine of our trusty Jeep Wrangler idling as a refuge from the -40 degrees Celsius temperatures!

A daytime Venus just over five days from inferior conjunction. Credit
A 1.3% illuminated daytime Venus just over five days from inferior conjunction. Credit Shahrin Ahmad www.shahgazer.net

It took us several frigid minutes of sweeping the horizon with binoculars before we could pick up the dusky dot of Venus through the low atmospheric murk and pervasive ice fog. We could just glimpse Venus unaided afterward, once we knew exactly where to look!

This works because the ecliptic is at a relatively shallow enough angle to the horizon as seen from the high Arctic that Venus gets its maximum ~five degree “boost” above the horizon.

A word of warning is also in order not to attempt this sighting while the dazzling (and potentially eye damaging) Sun is above the horizon. Start sweeping the horizon for Venus about 30 minutes before local sunrise, with the limb of the Sun safely below the horizon.

Venus presents a disk 1’ 02” across as seen from Earth during inferior conjunction, the largest of any planet and the only one that can appear larger than an arc minute in size. Ironically, both Venus and Earth reach perihelion this month. Said disk is, however, only 0.4% illuminated and very near the theoretical edge of visibility known as the Danjon Limit. And although the technical visual magnitude of Venus at inferior conjunction is listed as -3.1, expect that illumination scattered across that razor thin crescent to be more like magnitude -0.6 due to atmospheric extinction.

The mid-January passage of Venus through the field of view of SOHO's LASCO C3 imager. Field orientation is set for January 7th. Created using Starry Nite Software.
The mid-January passage of Venus through the field of view of SOHO’s LASCO C3 imager. Field orientation is set for January 7th. Created using Starry Nite Software.

Are you one of the +99% of the world’s citizens that doesn’t live in the high Arctic? You can still watch the passage of Venus from the relative warmth of your home online, via the Solar Heliospheric Observatory’s (SOHO) vantage point in space. SOHO sits at the sunward L1 point between the Earth and the Sun and has been monitoring Sol with a battery on instruments ever since its launch in 1995. A great side benefit of this is that SOHO also catches sight of planets and the occasional comet that strays near the Sun in its LASCO C2 and C3 cameras. Venus will begin entering the 15 degree wide field of view for SOHO’s LASCO C3 camera on January 7th, and you’ll be able to trace it all the way back out until January 14th.

Venus post solar transit as seen in SOHO's LASCO C3 imager. Credit-ESA/NASA
Venus post solar transit as seen in SOHO’s LASCO C3 imager. Credit-ESA/NASA

From there on out, Venus will enter the early morning sky. When is the first date that you can catch it from your latitude with binoculars and /or the naked eye? Venus spends most of the remainder of 2014 in the dawn, reaching greatest elongation 46.6 degrees west of the Sun on March 22nd, 2014 and is headed back towards superior conjunction on the farside of the Sun on October 25th, 2014. But there’s lots more Venusian action in 2014 in store…. more to come!

Now is a Great Time to Try Seeing Venus in the Daytime Sky

Here’s a feat of visual athletics to amaze your friends with this week. During your daily routine, you may have noticed the daytime Moon hanging against the azure blue sky. But did you know that, with careful practice and a little planning, you can see Venus in the broad daylight as well?

This week offers a great chance to try, using the daytime Moon as a guide. We recently wrote about the unique circumstances of this season’s evening apparition of the planet Venus. On Friday, December 6th, Venus will reach a maximum brilliancy of magnitude -4.7, over 16 times brighter than Sirius, the brightest star in the sky. And just one evening prior on Thursday December 5th, the 3-day old crescent Moon passes eight degrees above it, slightly closer together than the span of your palm held at arm’s length.

Created using Starry Night Education software.
The orientation of Venus and the Moon on Thursday, December 5th as it crosses the local meridian at 3PM EST. Created using Starry Night Education software.

The Moon will thus make an excellent guide to spot Venus in the broad daylight. It’s even possible to nab the pair with a camera, if you can gauge the sky conditions and tweak the manual settings of your DSLR just right.

The best time to attempt this feat on Thursday will be when the pair transits the local meridian due south of your location. Deep in the southern hemisphere, the Moon and Venus will appear to transit to the north.  This occurs right around 3:00 PM local. The fingernail Moon will be easy to spot, then simply begin scanning the sky to the south of it with the naked eye or binoculars for the brilliant diamond of Venus. High contrast and blocking the Sun out of view is key — Venus will easily pop right out against a clear deep blue sky, but it may disappear all together against a washed out white background.

The Moon will be at a 10% illuminated phase on Thursday, while Venus presents a slimming crescent at 27% illumination. Though tougher to find, Venus is actually brighter than the Moon in terms of albedo… expand it up to the apparent size of a Full Moon and it would be over four times as bright!

Photo by author.
Church and Venus as seen from Westgate River Ranch, Florida. Photo by author.

You’ll be amazed what an easy catch Venus is in the daytime once you’ve spotted it — we’ve included views of Venus in the daytime when visible during sidewalk star parties for years.

Due to its brilliancy, Venus has also been implicated in more UFO sightings than any other planet, and even caused the Indian Army to mistake the pair for snooping Chinese drones earlier this year when it was in conjunction with the planet Jupiter. A daytime sighting of the planet Venus near the Moon was almost certainly the “curious star” reported by startled villagers observing from Saint-Denis, France on January 13th, 1589.

Venus can also cast a noticeable shadow near greatest brilliancy, an effect that can be discerned against a fresh snow-covered landscape. Can’t see it? Take a time exposure shot of the ground and you may just be able to tease it out… but hurry, as the waxing Moon will soon be dominating the early evening night sky show!

Another phenomenon to watch for this week on the face of the waxing crescent Moon is known as Earthshine. Can you just make out the dark limb of the Moon? This is caused by the Earth acting as a “mirror” reflecting sunlight back at the nighttime side of the Moon. And don’t forget, China’s Chang’e-3 lander plus rover will be landing on the lunar surface in the Sinus Iridum region later this month on December 14th, the first lunar soft landing since 1976!

The imaginary line of the ecliptic currently bisects the Moon and Venus, as Venus sits at an extreme southern point 2.5 degrees below the ecliptic — in fact, 2013 the farthest south it’s been since 1930 — and the Moon sits over four degrees above the ecliptic this week. The Moon also reached another notable point today, as it reached its most northern “southerly point” for 2013 at a declination of -19.6 degrees. The Moon’s apparent path is headed for a “shallow year” in 2015, after which it’ll begin to slowly widen over its 18.6 year cycle out to a maximum declination range in 2024. It’s a weird but true fact that the motion of the Moon is not fixed to the Earth’s equatorial plane, but to the path of our orbit traced out by the ecliptic, to which its orbit is tilted an average of five degrees.

Stellarium
The view looking west tonight from latitude 30 degrees north. Created using Stellarium.

And speaking of the Moon, there’s another fun naked-eye feat you can attempt tonight. At dusk, U.S. East Coast observers might just be able to pick up the razor thin crescent Moon hanging low to the West, only 23 hours past New. Begin scanning the western horizon about 10 minutes after sunset. Can you see it with binoculars? The naked eye? Chances get better for sighting the slim crescent Moon the farther west you go. North American observers will have a chance at a “personal best” during next lunation in the first few days of 2014… more to come!

Be sure to send those Venus-Moon conjunction pics in to Universe Today!

Bright Venus Takes Center Stage in November

“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 1st, 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).
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 31st, 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)
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 6th -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 6th, 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 6th. 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 13th.

Venus also sits in the general of Pluto on November 15th, 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 5th.

Venus also presents a maximum area of illumination on December 6th, and will shine at its brightest on December 10th 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 2nd. 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 11th, 2014, and a rare chance to see it on said date… more to come!