Astro-Challenge: Adventures in Daytime Astronomy

Daytime planets
Daytime planets

It’s one of the stranger observations in ancient literature, and one of the earliest recorded tales of daytime astronomy.

A curious account comes to us from the 1st century AD Roman scholar Pliny the Elder, concerning the exploits of Greek philosopher Thales of Miletus, who notes that:

“The Sun’s radiance makes the fix’d stars invisible in the daytime, although they are shining as much as in the night, which becomes manifest at a solar eclipse and also when the star is reflected in a very deep well.”

Continue reading “Astro-Challenge: Adventures in Daytime Astronomy”

Catch Jupiter Homing in on Venus Through June

Getting closer... Venus, Jupiter, the Moon and an iridium flare on the night of May 26th, 2015. Image credit and copyright: Chris Lyons

Are you ready to hear an upswing in queries from friends/family and/or strangers on Twitter asking “what are those two bright stars in the evening sky?”

It’s time to arm yourself with knowledge against the well-meaning astronomical onslaught. The month of June sees the celestial action heat up come sundown, as the planet Jupiter closes in on Venus in the dusk sky. Both are already brilliant beacons at magnitudes -1.5 and -4 respectively, and it’s always great to catch a meeting of the two brightest planets in the sky.

June 5th
Looking west on the evening of June 5th from latitude 30 degrees north… Image credit: Stellarium

Be sure to follow Venus and Jupiter through June, as they close in on each other at a rate of over ½ a degree—that’s more than the diameter of a Full Moon—per day.

June 20th
…and looking west on the evening of June 20th…

Venus starts June at 20 degrees from Jupiter on the first week of the month, and closes to less than 10 degrees separation by mid-month before going on to a final closing of less than one degree on the last day of the June. Th climax comes on July 1st, when Venus and Jupiter sit just over 20’ apart—2/3rds the diameter of a Full Moon—on July 1st at 3:00 UT or 11:00 PM EDT (on June 30th). This translates to a closest approach on the evening of June 30th for North America.

July 1st
… and finally, looking westward on the evening of July 1st.

Venus starts the first week of June forming a straight line equally spaced with the bright stars Castor and Pollux in the astronomical constellation Gemini. On June 12-13, Venus actually nicks the Beehive cluster M44 in the constellation Cancer, a fine sight through binoculars.

Credit: Starry night Education software
The apparent paths of Venus versus Jupiter through the month of June. Credit: Starry Night Education software

Jupiter and Venus will then be joined by the Moon on the evening of June 20th to form a skewed ‘smiley face’ emoticon pairing. Not only is the pairing of Venus and the crescent Moon represented on many national flags, But the evening of June 20th will also be a great time to try your hand at daytime planet spotting before sunset, using the nearby crescent Moon as a guide.

The daytime view of Venus, the Moon and Jupiter of the evening of June 20th. Image Credit: Stellarium
The daytime view of Venus, the Moon and Jupiter of the evening of June 20th. Image Credit: Stellarium

The Moon will actually occult Venus three times in 2015: On July 19th as seen from the South Pacific, on October 8th as seen from Australia and New Zealand, and finally, on December 7th as seen from North America in the daytime.

This conjunction of Venus and Jupiter occurs just across the border in the astronomical constellation of Leo. As Venus can always be found in the dawn or dusk sky, Jupiter must come to it, and conjunctions of the two planets occur roughly once every calendar year. A wider dawn pass of the two planets occurs this year on October 25th, and in 2019 Jupiter again meets up with Venus twice, once in January and once in November. The last close conjunction of Venus and Jupiter occurred on August 18th, 2014, and an extremely close (4’) conjunction of Venus and Jupiter is on tap for next year on August 27th. Check out our nifty list of conjunctions of Venus and Jupiter for the remainder of the decade from last year’s post.

The view through the telescope on the evenings June 30th and July 1st will be stunning, as it’ll be possible to fit a 34% illuminated 32” crescent Venus and a 32” Jupiter plus its four major moons all in the same low power field of view. Jupiter sits 6 astronomical units (AU) from Earth, and Venus is 0.5 AU away on July 1st.

30 FoV
Looking at Jupiter and Venus on July 1st using a 30 arc minute filed of view. Image credit: Starry Night Education Software

And just think of what the view from Jupiter would be like, as Venus and Earth sit less than 3 arc minutes apart:

View from jupiter
The view from Jupiter on July 1st looking at the Earth. Image credit: Starry Night Education software

Venus reaches solar conjunction this summer on August 15th, and Jupiter follows suit on August 26th. Both enter the field of view of the European Space Agency’s Solar Heliospheric Observatory (SOHO) LASCO C3 camera in mid-August, and are visible in the same for the remainder of the month before they pass into the dawn sky.

But beyond just inspiring inquires, close conjunctions of bright planets can actually raise political tensions as well. In 2012, Indian army sentries reported bright lights along India’s mountainous northern border with China. Thought to be reconnaissance spy drones, astronomers later identified the lights as Venus and Jupiter, seen on repeated evenings. We can see how they got there; back in the U.S. Air Force, we’ve seen Venus looking like a ‘mock F-16 fighter’ in the desert dusk sky as we recovered aircraft in Kuwait. Luckily, cooler heads prevailed during the India-China incident and no shots were exchanged, which could well have led to a wider conflict…

Remember:  Scientific ignorance can be harmful, and astronomical knowledge of things in the sky can save lives!

Slender Moonspotting, Occultations, Daytime Planets and More

Credit and copyright:

One of nature’s grandest ‘occultations’ of all is coming right up this Friday, as the Moon passes in front of the Sun for viewers in the high Arctic for a total solar eclipse. And although 99.999+% percent of humanity will miss totality, everyone can trace the fascinating path of the Moon as it moves back into the evening sky this weekend.

As of this writing, it looks like the fickle March weather is going to keep us guessing right up to eclipse day. Fear not, as the good folks over at the Virtual Telescope Project promise to bring us views of the eclipse live.  Not only does this eclipse fall on the same day as the start of astronomical spring in the northern hemisphere known as the vernal (northward) equinox, but it also marks the start of lunation 1141.

Ever try hunting for the slender crescent Moon in the dawn or dusk sky? The sport of thin Moon-spotting on the days surrounding the New Moon can push visual skills to the very limit. Binoculars are your friend in this endeavor, as you sweep back and forth attempting to see the slim fingernail of a Moon against the low contrast background sky.  Thursday morning March 19th provides a great chance for North American observers to spy an extremely thin Moon about 24 hours prior to Friday’s eclipse.

Projected locales for the first sightings of the slim crescent Moon on the evening of March 20th. Credit: Created by author.

Unfortunately, most of North America misses the eclipse, though folks on the extreme east coast of Newfoundland might see a partially eclipsed sunrise if the day dawns clear.

The Moon will first be picked up in the evening sky post-eclipse this weekend. On Friday evening, folks in the southern United States might just be able to spy a 15 hour old Moon with optical assistance if skies are clear.

As the Moon fattens, expect to see it at its most photogenic as Ashen light or Earthshine illuminates its nighttime side. What you’re seeing is sunlight from the Earth being reflected back in a reverse (waning gibbous) phase as seen from the earthward side of the Moon. The prominence of Earthshine can vary depending on the amount of cloud and snow cover currently turned moonward, though of course, if it’s cloudy from your location, you won’t see a thing…

The universe smiles back: A skewed emoticon grouping of Venus, Mars and the Moon plus Earthshine on February 20th. Photo by author.

Watch that Moon over the coming weeks, as it has a date with destiny.

The Moon occults (passes in front of) two planets and one bright star in the coming week. First up is an occultation of Uranus on March 21st at around 11:00 UT/7:00 AM EDT. Sure, this one is for the most part purely academic and unobservable, as it occurs over central Africa in the daytime and is only 15 degrees east of the Sun. Still, if you can pick up the Moon on the evenings of March 20th or March 21st, you might just be able to spy nearby Uranus shining at +6th magnitude nearby before it heads towards solar conjunction on April 6th.

The visibility footprint of the March 21st occultation of Mars by the Moon. Credit: Occult 4.1.

Next, the Moon occults Mars on March 21st at 22:00 UT/6:00 PM EDT for the southern Pacific coast of South America. North America will see an extremely close photogenic pairing of Luna and the Red Planet. This is one of seven occultations of a naked eye planet by the Moon for 2015, and the first of two for Mars for the year, the next falling on December 6th.

The Moon pairs with Venus on the evening of March 22nd. Credit: Stellarium.

Next up, the Moon has a tryst with brilliant Venus, passing 2.8 degrees from the Cytherean world on March 22nd. Can you spy -4th magnitude Venus near the two day old Moon before sunset? This is the stuff that has inspired astronomically-themed flags and skewed emoticon ‘smiley face conjunctions’ of yore, including the close pairing of Mars, Venus and the Moon seen worldwide last month.

The occultation of Aldebaran by the Moon on March 25th. Credit: Occult 4.1.

Next up, the 30% illuminated Moon occults the bright star Aldebaran for Alaskan viewers at dusk on March 25th. This is the third occultation of the star by the Moon in the ongoing cycle, and to date, no one has, to our knowledge, successfully caught an occultation of Aldebaran in 2015… could this streak be broken next week?

The daytime Moon paired with Jupiter on March 30th. Credit: Starry Night Education software.

And speaking of daytime planet-spotting, Jupiter will sit only five degrees south of the waxing gibbous Moon on the evening of March 30th. Can you spy the giant planet near the daytime Moon in the afternoon sky using binocs? And finally, watch that Moon, as it heads for the third total lunar eclipse of the last 12 months visible from the Americas and the Pacific region on the morning of April 4th

More to come!

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

Venus (arrowed) imaged near the waning crescent Moon on August 13th, 2012. (Photo by author).

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.

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!

See Venus and the Moon Together in the Sky on September 8

A close conjunction of Venus and the crescent Moon as seen on February 27th, 2009. (Photo by author).

Sky watchers worldwide are in for a treat Sunday evening September 8, 2013 as the waxing crescent Moon passes near the dazzling planet Venus. And for a select few, the Moon will actually pass in front of Venus, in what is known as an occultation.

The action has already started this week, as the Moon reached New phase earlier today at 7:36 AM EDT/11:36 UT. The appearance of the slim crescent Moon nearest to the September equinox marks the start of the Jewish New Year with the celebration of Rosh Hashanah, which this year began as early as it possibly can at sundown on September 4th. As per tradition, Rosh Hashanah formally begins when the sky is dark enough for three stars to be seen.  The convention established by Hillel II in 363 A.D. uses the mean motion of the Moon to fix the start dates of the Jewish luni-solar calendar, which means that occasionally Rosh Hashanah can start a day early. This also occurred in 2002.

The New Moon has also been historically an opportune time for nighttime military operations to commence —Desert Storm in 1991 and the raid against Bin Laden in 2011 were both conducted under the darkness afforded by the absence of moonlight around a New Moon. It’s yet to be seen if planners looking to conduct airstrikes on Syria are planning on taking advantage of the same conditions to begin operations soon.

Tonight, you can see the +1st magnitude star Spica less than two degrees away from -4th magnitude Venus. This places Venus at 100 times brighter than Spica and visible before sunset if you know exactly where to look for it.

The brightest star in the constellation Virgo, Spica is 260 light years distant and on the short list of nearby stars that will eventually go supernova. Fortunately for us, Spica is well outside of the ~100 light year radius “kill zone”.

You might just be able to spy the Moon and the -1st magnitude planet Mercury low to the west at dusk for the first time for this lunation tonight or (more likely) Friday night. This is also a great time to check out LADEE’s future home as it departs for lunar orbit from Wallops Island in Virginia on Friday night.

Hey, LADEE sitting on the pad atop its Minotaur V rocket with the slim crescent Moon in the background at dusk Friday night would be a great money shot, I’m just sayin’…

This weekend will see the Moon increase in illumination and elevation above the western horizon each evening until Spica, Venus, and the waxing crescent Moon fit within a four degree circle on Sunday night. The Moon will be 12% illuminated, while Venus is currently at a gibbous phase and 72% lit.

Looking west from latitude 30 north Sunday night from the US east coast... note that Mercury and Saturn are in the picture as well! (Created by the author in Stellarium).
Looking west from latitude 30 north Sunday night from the US east coast… note that Mercury and Saturn are in the picture as well! (Created by the author in Stellarium).

This will also present a good chance to see Venus during the daytime, using the nearby crescent Moon as a guide. This is a fun thing to try, and no gear is required! Though Venus may seem tough to find against the bright daytime sky, appearances are deceptive. With an albedo of 67% versus the Moon’s average of 14% Venus is actually brighter than the Moon per square arc second of size!

The Moon will also occult Spica on the evening of September 8th for observers in the Middle East and Europe right around sunset. Spica is one of four bright stars that the Moon can occult in the current epoch, along with Antares, Aldebaran, and Regulus. This is also part of a series of fine occultations of Spica by the Moon ongoing from 2012 to 2014.

Sundown on September 8th offers a special treat, as the 3-day old Moon passes less than a degree from Venus worldwide. The pair will fit easily into the field of view of binoculars or a telescope at low power and present an outstanding photo op.

And for observers based in Argentina and Chile, the Moon will actually occult Venus. Occultations are grand events, a split-second astronomical event in a universe that seems to usually move at a glacial pace. This particular occultation occurs for South American observers just before & after sunset.

The occultation of Venus by the Moon; the footprint over South America. (Credit: Occult
The occultation of Venus by the Moon; the footprint over South America. (Credit: Occult

We witnessed and recorded a similar pairing of Venus and the daytime Moon from the shores of our camp on Saint Froid Lake in northern Maine back in 2007:

Also, keep an eye out for a ghostly phenomenon known as the ashen light on the dark limb of the Moon. Also known as Earthshine, what you’re seeing is the reflection of sunlight off of the Earth illuminating the (cue Pink Floyd) dark side of the Moon. When the Moon is a crescent as seen from the Earth, the Earth is at gibbous phase as seen from the nearside of the Moon. Remember, the lunar farside and darkside are two different things! Earthshine can vary in brightness, based on the amount of cloud and snow cover present or absent on the Earth’s moonward side. My Farmer’s Almanac-consulting grandpappy would call ashen light the “Old Moon in the New Moon’s arms,” and reckon rain was a comin’…

Be sure to check out these astronomical goings on this weekend, and send those pics in to Universe Today!