Skywatching Archives

November 8, 2016November 8, 2016 by Bob King

What I Learned Writing ‘Night Sky with the Naked Eye’

The author enjoys a pretty display of the northern lights on October 23 under a starry sky. His new book, "Night Sky with the Naked Eye," explores all the amazing things you can see in the sky without special equipment including satellites, planets, meteor showers and of course, the aurora. — The author enjoys a pretty display of the northern lights on October 23, 2016 under a starry sky. His new book, “Night Sky with the Naked Eye,” explores all the amazing things you can see in the sky without special equipment including satellites, planets, meteor showers and of course, the aurora.

My book Night Sky with the Naked Eye publishes today. It would have never seen the light of day much less ever been conceived were it not for Fraser Cain, publisher of Universe Today, and Nancy Atkinson, an editor and writer for the same. Several years ago, Nancy invited me to write for UT. I hopped at the chance. Before her contact, I’d been writing a daily blog on astronomy called Astro Bob (and still do).

Fast forward to last summer when I got an email from Nancy saying Page Street Publishing had contacted her about writing a book about space missions. The publisher also wanted a book about night sky observing without fancy equipment for which she recommended me. Me? I felt like the luckiest guy on the planet!

Book writing proceeds in many stages. First, the table of contents had to be prepared and approved. Then followed a sample chapter. The publisher chose the one on artificial satellites, which I wrote in about a week. The tone was right, but he asked for changes in the organization, which I dutifully made. By November, a contract followed and the project was underway with a first draft due to my editor in about 10 weeks.

Cover of my book that publishes today. Credit: Bob King

Writing is hard work. But it’s a special place all writers come back to again and again. We can’t help but keep trying to find just the right words to capture a concept or emotion. And when we do, a quiet pleasure flows down the spine like warmth creeping into cold fingers splayed in front of a fire. Not that these moments always come easily. Writer Colson Whitehead describes the experience of writing as “crawling through glass.” I would soon become well-acquainted with that feeling, too.

Nancy wrote her book Incredible Stories from Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos at nearly the same time. We were grateful for each other’s support, and it was a kick to follow her progress as well as bounce ideas around. With a tight deadline in front of me, I set to work immediately, taking more than two weeks of vacation from my regular job to make sure the draft was done on time. No way was I going to compromise an opportunity of a lifetime.

Maybe you’ve thought of writing a book, starting a blog or hope one day to write for Universe Today or another online astronomy site. There’s plenty of good advice for writers out there. I’ll share what worked for me.

#1: Put your butt in the chair and keep it in the chair. My wife reminded me of this often, adding that the book wasn’t going to write itself. Temptations are everywhere. Answering the phone, making another cup of tea, staring out the window and my favorite, shoveling the driveway. I had the cleanest driveway in the neighborhood. Even an inch of new snow was enough to grab the shovel and happily scrape down to the gravel. So yes, I did occasionally get out of the chair, but many times it did me good, freeing up the brain to see more clearly into a topic. Or dream up a fitting photo or illustration.

Creativity comes at odd little moments. It can flow while tapping away in front of a glowing screen or sneak into consciousness when you’re bending down to feed the dog. So a mix of activities seemed the best but with extra emphasis on staying put. I rarely hiked last winter and kept my walks in the neighborhood brief. Instead of observing at night, I wrote or gathered photos. By January, I joked to my friends that I’d voluntarily put myself under house arrest.

#2: Spill your guts, worry about the details later. It’s incredibly tempting when writing to continuously edit one’s work, going back over every sentence to make each “perfect”. This is a muse-killer. Though difficult to stick to, once you let your thoughts flow onto paper without worrying about spelling, clauses and the whole lot of burdensome rules, you’ll become a wild horse running free on the prairie. Let it out, let it out and worry about the commas later. I don’t play a musical instrument, but free-flow writing — just getting the ideas out — must feel something like riffing on a jazz melody.

#3: When stuck, move on to another topic, take a walk, listen to music. Struggling to describe an important concept or connecting your thoughts in a way that flows on the page can drive you nuts, even bring you to tears. Sure, you can keep beating on the idea like a madman hammering on a bent nail, but why why torture yourself? A little distraction can be good. Move on to another part of the story or a different chapter or get up and take a short walk. Defocusing allows the ideas you’re having a tug-of-war with to come of their own accord.

To keep track of ideas, topics and the photos I'd need for the book, I kept a notebook. Credit: Bob King — To keep track of ideas, topics and the photos I’d need for the book, I kept a notebook filled to the gills with lists. Checkmarks indicate tasks accomplished. Credit: Bob King

As the February 1 deadline approached, time took on a physical dimension under the intense pressure to get everything done. I cut time into little blocks that when added up would get me to the finish line on the first draft. I made it just in time, shipped off my copy via e-mail, got in the car to go to work and turn up the music really LOUD. For a fews days I was on top of the world. Invincible.

My editor, Elizabeth, contacted me later with positive comments and then returned the manuscript with “developmental edits” or questions about descriptions and organization. We pitched the ever-refined draft back and forth over the next few months. Each time I read through the ten chapters and made both suggested changes and other refinements. I also added photos during this stage and worked via e-mail with the layout staff to place the best images and graphics at the best places in the text. I shot more images and requested photos from talented astrophotographers, prepared the acknowledgments and sought our recommendations from respected scientists and writers.

This diagram from the book uses the human face to illustrate how changing lighting angles causes the phases of the moon. Credit: Bob King

The editors at Page Street were quite generous with photo usage, a joy for me because that’s what I do for a living. I’ve been a photographer and photo editor at the Duluth News Tribune in Duluth, Minn. for many years. My favorite subjects are people, but I slip in an aurora or eclipse now and again. And that’s the irony. I never saw myself as a writer.

Like many, I started by keeping a journal of my observations through the telescope and reflections about the night sky. The Astro Bob blog took that a step further and writing for Universe Today and Sky & Telescope let me find my voice. So I maybe I have a voice, and I like to think I can be a helpful guide at your side, but writer? That still seems too lofty a term to describe what I do. But here we are.

After several edits including the final one, when I was sent a thick stack of low-res black and white pages of the book to mark up and return, I rested briefly before beginning the final phase: publicity. This is the weird part, where you tell everyone what a nice book you’ve written and how it would make a great Christmas gift for that budding astronomer in the family. When I held the first copy in my hands I couldn’t believe that all those hours of work at the computer became a physical object, a beautiful one even.

This map from the book shows Saturn's location around the time of opposition through 2021. — This map from the book shows Saturn’s location around the time of opposition through 2021. Credit: Bob King, Source: Stellarium

I’m biased of course, but I think both beginning and amateur astronomers will find the book useful. It includes lots of suggested activities – set off in separate boxes – to encourage you to get out under the stars. I make regular mention of the Web and phone apps as ways to become more familiar with the constellations, learn of newly-discovered bright comets and even find a dark sky.

Besides the easy naked eye topics like how to find the brightest constellations or see the best meteor showers of the year, the book offers visual challenges. Have you ever seen craters on the Moon without optical aid or the midnight glow of the gegenschein? You’ll find out how in my book. As a photographer, I’ve included tips on how to focus a digital camera and use it to photograph the aurora or a space station pass.

I’d be willing to bet that most books aren’t as complete as their authors would hope. I had to cut precious photos, graphics, 3 years of a sky calendar and other bits and pieces from mine. Ouch! To this day, I’m still thinking of ways to improve it with a fresh photo, new diagram or change of wording. Now it’s your turn to be the judge.

The zodiacal light punctuated by the planet Jupiter reflects off Lake Superior near Duluth, Minn. this morning (Nov. 8). The book describes nighttime lights such as the zodiacal, gegenschein, airglow and lunar halo and corona phenomena. Credit: Bob King — The zodiacal light punctuated by the planet Jupiter towers over northern Wisconsin along Lake Superior near Duluth, Minn. this morning (Nov. 8). The book describes nighttime lights such as the zodiacal, gegenschein, airglow in addition to lunar halo and corona phenomena. Credit: Bob King

Throughout, Nancy and I rooted for one another and shared our ups and downs. Incredible Stories was to publish within a week of Night Sky, but a type corruption error discovered in several chapters put the book on hold. Her new publication date is December 20, and I encourage you to pre-order a copy, so it arrives in time for Christmas. Order a copy of my book also, and I promise the two of us will keep you company on those long winter nights ahead.

Can I share one final tip? Once you’ve found your passion, say ‘yes’ to every opportunity that furthers it. You’ll be amazed at the places that one word will take you to.

*** To order a copy of Night Sky with the Naked Eye just click an icon to go to the site of your choice — Amazon, Barnes & Noble or Indiebound. It’s currently available at the first two outlets for a very nice discount. It should also be at your local B&N bookstore. And don’t forget to vote today!

November 2, 2016 by David Dickinson

Watch Asteroid 2016 VA Pass Through Earth’s Shadow

Mining asteroids might be necessary for humanity to expand into the Solar System. But what effect would asteroid mining have on the world's economy? Credit: ESA.

Holy low-flying space rocks, Batman.

Newly discovered asteroid 2016 VA snuck up on us last night, and crossed through the Earth’s shadow to boot.

Discovered just yesterday by the Mount Lemmon Sky Survey based outside of Tucson Arizona, 2016 VA passed just 58,600 miles (93,700 kilometers) from the surface of the Earth this morning at 00:42 Universal Time (UT). That’s a little over 20% of the distance from the Earth to the Moon, and just over twice the distance to the ring of geosynchronous and geostationary satellites around the Earth.

This sort of close pass of a newly discovered asteroid happens a few times a year. What made 2016 VA’s passage unusual, however, was its transit through the Earth’s shadow. The discovery was announced yesterday by the Minor Planet Center, and astronomer Gianluca Masi soon realized that the Virtual Telescope Project had a unique opportunity to capture the asteroid on closest approach.

The passage of asteroid 2016 VA. Image credit: The Virtual Telescope Project. — Asteroid 2016 VA. Image credit: The Virtual Telescope Project.

Gianluca Masi explained how the difficult capture was done:

“The image is a 60-second exposure, remotely taken with “Elena” (a PlaneWave 17” +Paramount ME+SBIG STL-6303E robotic unit) available at the Virtual Telescope project. The robotic mount tracked the extremely fast apparent motion of the asteroid, so stars are trailing. The asteroid is perfectly tracked; it is the sharp dot in the center, marked with two white segments. At imaging time, asteroid 2016 VA was at about 200,000 kilometers from us and approaching.”

Catching a fast-moving asteroid such as 2016 VA on closest approach isn’t easy. First off, there’s an amount of uncertainty surrounding the orbit of a newly discovered object until more observations can be made. 2016 VA passed close enough to the Earth that our planet’s gravity substantially altered the tiny asteroid’s future orbit. Also, a house-sized Earth-crosser like 2016 VA is really truckin’ across the sky on closest approach: 2016 VA was moving at 1500” a minute through Earth’s shadow – that’s 25” a second, fast enough to cross the apparent diameter of a Full Moon in just 72 seconds.

Masi also notes:

“During its flyby, asteroid 2016 VA was also eclipsed by the Earth. We covered the spectacular event, clearly capturing the penumbral effects. The movie is an amazing document showing the eclipse. Each frame comes from a 5-second integration.”

Watch as 2016 VA winks out as it hits Earth's shadow... Image credit: The Virtual Telescope Project. — Watch as 2016 VA winks out as it hits Earth’s shadow… Image credit: The Virtual Telescope Project.

At an estimated 16 to 19 meters in size, 2016 VA shined at 13^th magnitude as it crossed the southern hemisphere constellation of Sculptor on closest approach. It crossed through the Earth’s shadow for 11 minutes from 23:23 to 23:34 UT last night, just over an hour before closest approach. You can see the dimming effect of the Earth’s outer penumbral shadow in the video, just before the asteroid strikes the inner dark umbra and emerges back into eternal sunshine once again. Sitting on 2016 VA, and observer would have seen a total solar eclipse, as the bulk of the Earth passed between the asteroid and the Sun in an event not witnessed by the tiny world for thousands of years.

Such transits of asteroid through the Earth’s shadow have been observed before: 2012 XE54 crossed through the Earth’s shadow a few years back, and 2008 TC3 crossed through the Earth’s shadow before striking the Nubian desert in the early morning hours of October 7^th, 2008.

Satellites in geostationary orbit also pull a similar vanishing act right around either equinox as well.

The orbit of 2016 VA. Iimage credit: NASA/JPL. — The orbit of 2016 VA. Image credit: NASA/JPL.

2016 VA is also a similar size to another famous space rock: the 20 metre asteroid that exploded over the city of Chelyabinsk the day after Valentine’s Day in 2013. 2016 VA gave us a miss, and won’t make another pass as close to the Earth again for this century.

To our knowledge, such a video capture of an asteroid crossing through Earth’s shadow is a first, or at least the first that we’ve seen circulated on ye ole Web.

The light curve of 2016 as it passed through the Earth's shadow. Image credit: Peter Birtwhistle, Great Shefford Observatory. — The light curve of 2016 as it passed through the Earth’s shadow. Image credit: Peter Birtwhistle, Great Shefford Observatory.

Congrats to the good folks at the Virtual Telescope Project for swinging into action so quickly, and providing us with an amazing view!

-Catch the closest Full Moon of the year (and for many years to come!) on November 14^th live courtesy of the Virtual Telescope Project.

November 1, 2016November 4, 2016 by Bob King

November Opens with a Splendid Gathering of Moon and Planets

Crescent Moon and flag. Credit: Bob King

Look how pretty. This will be the scene from your yard, apartment window or driving west along the freeway Tuesday evening about 45 minutes after sundown. Saturn and the Moon will be in conjunction about 3 degrees apart with Venus 6 degrees to the southeast of the crescent. Source: Stellarium — Look how pretty. This will be the scene from your yard, apartment window or driving west along a freeway Tuesday evening about 45 minutes after sundown. Saturn and the Moon will be in conjunction about 3 degrees apart with Venus 6 degrees to the southeast of the crescent. Source: Stellarium

I love easy and bright. While I often spend time seeking faint nebulae and wandering comets, there’s nothing like just looking up and seeing a beautiful scene aglow in the night sky. No binoculars or telescope needed. That’s exactly what will happen Tuesday November 2, when an attractive crescent Moon will join Saturn and Venus at dusk in the southwestern sky.

The supermoon of March 19, 2011 (right), compared to an average moon of December 20, 2010 (left). Note the size difference. Image Credit: Marco Langbroek, the Netherlands, via Wikimedia Commons. — The Supermoon of March 19, 2011 (right), compared to an average moon of December 20, 2010 (left). November’s Supermoon will be 14% bigger and 30% brighter than a regular Full Moon. Credit: Marco Langbroek / Wikimedia Commons

What a fine threesome they’ll make: Venus the white-hot spark shining at magnitude –4.0; Saturn a mellow magnitude +0.5, some 20 times fainter and the Moon a fingernail crescent above them both. The Moon will be just two days past apogee, the furthest point in its orbit from Earth. Does it look a little smaller than the usual crescent? If you’re a keen watcher of crescents, you just might notice the difference.

In less than two weeks, on November 14, the crescent will have waxed to full, swung around to the opposite end of its orbit, where it will be at perigee, its closest point to Earth. When a Full Moon occurs at perigee, we call it a Supermoon because it’s closer and correspondingly bigger and brighter than a typical Full Moon.

For a variety of reasons, the November Supermoon will come exceptionally close to Earth, the closest one in 70 years as a matter of fact. The last time Earth and Moon embraced each other so tightly was January 26, 1948, the year baseball great Babe Ruth died. But I’m getting ahead of myself. We’ll have much more on the Supermoon soon!

This photo shows the contrast between the bright, sunlit crescent and the ghostly earth-lit Moon. Several prominent craters are identified. Credit: Bob King

Tuesday night you have the pleasure of an eye-catching crescent filled with darkly luminous earthshine, sunlight reflected off our jolly blue and white globe into space that reflects from the Moon and back to Earth. Being twice reflected, the returning light is feeble, giving the Moon a haunted look.

The phases of the Moon and Earth are complementary; when one's a crescent, the other's nearly full. Credit: Bob King, Source: Stellarium — The phases of the Moon and Earth are complementary; when one’s a crescent, the other’s nearly full. Credit: Bob King, Source: Stellarium

Crescent phase is when earthshine is brightest. Why? Phases of Earth and Moon are complementary — when we see a crescent, an astronaut on the Moon would look back to see a nearly Full Earth in the sky. As you’ve already guessed, a Full Earth reflects a great deal more light than a half or crescent. Be sure to point your binoculars at the earth-lit Moon; the contrast of dusky earthlight adjacent to the sunlit crescent gives the scene a striking 3D look.

And if your glass can magnify ten times or more, you’ll get a sneak preview of several of the dark lunar seas or maria in the smoky light. Seas that will by and by ease into sunlight as the lunar terminator, the line separating day from night, rolls ever westward.

Through a small telescope, Venus appears three-quarters full in waning gibbous phase. Saturn's rings are still tipped wide open, and it's brightest moon, Titan, should be easy to spot Tuesday night in a small telescope. Source: Stellarium — Through a small telescope, Venus appears three-quarters full in waning gibbous phase. Saturn’s rings are still tipped wide open, and its brightest moon, Titan, should be easy to spot Tuesday night in a small telescope. Appearances are shown for Nov. 2. North is up and west to the right. Source: Stellarium

Have a small telescope? This may be one of your last easy chances at seeing the planet Saturn before it’s gobbled up by the western horizon. The ringed one has been sinking westward the past couple months and will soon be in conjunction with the Sun. I hate to see a good planet go, that’s why I’m happy to share that Venus will be with us a long, long time. Watch for this most brilliant of planets to rise higher in the southwestern sky as we approach Christmas and then swing to the north through early winter before dropping out of the evening sky in March 2017.

Thank you Venus for lighting our path on the snowy nights that lie ahead!

*** If you’d like learn more about how to find the planets, check out my new book, Night Sky with the Naked Eye. It covers all the wonderful things you can see in the night sky without special equipment. The book publishes on Nov. 8, but you can pre-order it right now at these online stores. Just click an icon to go to the site of your choice – Amazon, Barnes & Noble or Indiebound. It’s currently available at the first two outlets for a very nice discount:

October 25, 2016 by David Dickinson

Boo! A Black Moon Halloween Weekend

This Halloween weekend’s top astronomical event features something that you won’t see in the sky.

By now, you’ve probably seen the stories circulating ’round ye ole web about how this month features a ‘Black Moon.’ The internet seems to love promulgating the passing of such curious calendrical oddities as Moons both Black, Blue and otherwise.

What’s all of the hoopla about? Well, simply put, the Moon reaches New phase this weekend on October 30^th at 17:38 Universal Time (UT), marking the start of lunation 1161. This is the second New Moon for the month, as the first fell on October 1^st, just 11 minutes into the month as reckoned in Universal Time.

Now, this isn’t at all rare or unusual; the synodic period of the Moon (that is, the time it takes to return to a similar phase, such as New back to New) is 29.5 days long, a period that shoehorns well in to a 31 day month like October, or occasionally, a 30 day month.

More Fun With Calendars

February is the only month that cannot contain a ‘repeat phase,’ leap year or no. Occasionally, a given phase such as New or Full can be absent from short February all together… sometimes, this oddity is also sometimes referred to as a ‘Black Moon.’ 2014 and 2033 are the nearest years to 2016 that are missing New Moons in February.

And then there’s the relict definition of a Blue Moon as the ‘3^rd in an astronomical season with 4…‘ that can also be ascribed to a Black Moon as relates to New phase, as if we already lack enough multi-hued Moons in or lives.

Keep in mind, the moment of New is but an instant, a point a which the Moon’s longitude along the ecliptic plane equals the Sun’s. The Moon makes a miss of the Sun on most lunations, and only directly passes between the Sun and the Earth during an annular or solar eclipse. We’ve got one each coming up in 2017: an annular solar eclipse crossing the southern tip of South America on February 26^th, and the historic return of totality to the United States on August 21^st, 2017.

Said high profile solar eclipse next August also has a lesser role, as it fits that old-timey definition of the 3^rd New Moon in an astronomical season with four. Of course, this is only the juxtaposition of the lunar cycle on our current Gregorian calendar, using time reckoned in UT/GMT.

Don’t fear the Black Moon. This year’s New Moon just misses Halloween. The next New Moon on Halloween (which, of course, is always a ‘Black Moon’) occurs in 2035.

The view looking eastward on the morning of Friday, October 28th. Image credit: Stellarium

And we’ll let you in on a secret: astronomers don’t spend nights in mountaintop observatories discussing Black or Blue Moons… the term has more of an astrological tinge to it. Even in amateur astronomy circles, you sometimes hear the term ‘the dark of the Moon’ used to refer to the weeks surrounding New Moon, a prime time for deep sky astrophotography.

Looking for a New Moon-related observing challenge? Spotting the razor thin waxing or waning Moon is a fun feat of visual athletics. Look for a thin waning crescent Moon hanging near Jupiter on the morning of Friday, October 28^th. This weekend, the first shot at catching the uber-thin Moon occurs for observers along a curve from southeastern Asia at dusk on October 31^st westward at dusk. For Spain (and Astroguyz basecamp) the Moon will be 24 hours past New, and for the United States, the Moon will be 28 to 32 hours old at sunset for roaming Halloween ghouls and goblins, an easy catch.

First sighting opportunities for the waxing crescent Moon on Halloween evening. Graphic created by the author.

A time change is also afoot this weekend, as folks in Europe and the UK ‘fall back’ one hour to standard time. This setback falls nearly as late as it can in 2016, and we now enter that wacky oneeek period where the world slowly slips back to standard time. Blame ‘Big Sugar’ for the latency in most of North America, as prospective trick-or-treaters now make their rounds during daylight hours. In most of the US and Canada, the switch occurs on Sunday, November 6^th.

And there’s one more astronomical tie-in for Halloween: the holiday traces its roots back as one of the four cross-quarter days of yore, including Lammas Day, Groundhog Day, and May Day. Of course, the fixing of Hallow’s Eve on October 31^st makes the midway date only approximate: in 2016, the actual mid-point occurs on November 10^th.

Out of this world stuff to consider, as you inventory the night’s sugary bounty and contemplate the night sky.

October 18, 2016 by David Dickinson

Photobomb: The Moon Occults Aldebaran Wednesday

An occultation of Aldebaran by the Moon: before and after. Image credit and copyright: Eliot Herman.

How about that Hunter’s Supermoon this past weekend, huh? Follow that Moon, as it’s meeting up with the Hyades again this week, and occults (passes in front of) Aldebaran Tuesday night into Wednesday morning.

Here’s the lowdown on the event:

The 86% illuminated waning gibbous Moon occults the +0.9 magnitude star Aldebaran across North America, the Northern Atlantic and Europe. The Moon is three days past Full during the event. Both are located 136 degrees west of the Sun at the time of the event. The central time of conjunction is ~6:40 Universal Time (UT). The event occurs during the daylight hours over western Europe and northwestern Africa and under darkness for southeastern North America, including the eastern United States and Mexico. The Moon will next occult Aldebaran on November 15^th, 2016. This is occultation 24 in the current series of 49 running from January 29^th, 2015 to September 3^rd 2018.

The occultation of Aldebaran by the Moon as seen from London on December 23rd, 2015. Image credit and copyright: Roger Hutchinson.

The graze line is of particular interest during this event. We’re talking about the very edge of the footprint of the Moon’s ‘shadow’ cast by Aldebaran, running through Canada and bisecting the United States. Observers based along this line could see a spectacular ‘grazing occultation’ of Aldebaran by the Moon. We usually think of the limb of the Moon as a smooth curve, but it’s actually jagged. What you may see is Aldebaran wink in and out as light shines down those lunar valleys and is alternately blocked out behind peaks and crater rims. This is an unforgettable sight, and makes for great video. A record of a grazing occultation by multiple observers can also be used to create a profile of the lunar limb. That light from Aldebaran took 65 years to get here, only to be blocked by our Moon at the very last second.

The occultation footpring for tonight's event. The solid lines denote where the occultation occurs under dark night time skies, while the blue lines denote twilight and the broken lines describe where the event occurs in the daytime. Image credit: Occult 4.2. — The occultation footprint for tonight’s event. The solid lines denote where the occultation occurs under dark nighttime skies, while the blue lines denote twilight, and the broken lines describe where the event occurs in the daytime. Image credit: Occult 4.2.

And observers (myself one of them) based in Europe shouldn’t count themselves out. Like brighter planets, you can spy a +1 magnitude star such as Aldebaran near the daytime Moon using binoculars or a telescope… if, of course, you have a high contrast deep blue sky and know exactly where to look for it. The International Occultation Timing Association has a page for the event with a complete list of ingress and egress times for key cities on three continents in the path. We’ll be watching the Wednesday event – clear skies willing — from our present basecamp in the Andalusian foothills just outside of Jimena de la Frontera, Spain.

The northern graze line for tonight's occultation. Note that several major cities lie along the crucial path. Image credit: Dave Dickinson. — The northern graze line for tonight’s occultation. Note that several major cities lie along the crucial path. Image credit: Dave Dickinson.

During our current epoch, the Moon can only occult four +1^st magnitude stars: Regulus, Spica, Antares and Aldebaran. The slow motion movement of the Moon, the Earth and the background stars make this prestigious A-list change over time: until about two millennia ago, you could also count the bright star Pollux in Gemini among them.

In the current century, (2001-2100 AD) the Moon occults Aldebaran 247 times, topped only by Antares (386 times) and barely beating out Spica (220 times).

Timing an occultation is fun and as easy as shooting video of the Moon through a telescope at the appointed time of ingress or egress. Practice on framing the dazzling Moon first well in advance — probably the toughest part is getting the exposure of the bright limb stopped down enough to still see and image the star. We find that shooting anywhere from 1/100^th to 1/500^th frame rate for a gibbous Moon is about right. Don’t be afraid to crank up the magnification a bit, so you can place the bulk of the Moon out of view. Also, catching occultations of stars and planets during waning Moon phases are more challenging than waxing, as the star will ingress behind the bright leading limb and later reappear behind the dark trailing limb (waxing is vice versa).

Observing: Running an audible time hack in the background such as WWV radio out of Fort Collins, Colorado can provide a precise record of the occultation.

But wait, there’s more. When the Moon occults Aldebaran, its also crossing the background V-shaped open star cluster known as the Hyades. Worldwide the waning gibbous Moon also occults Gamma, 51, and Theta^1 and Theta^2, SAO 93975, and 119 Tauri. Chances are, there’s an occultation for YOU to catch this week, regardless of your location.

Want more? Well, the Moon continues to occult Aldebaran every lunation through 2017, and will also start a cycle of passes in front of Regulus on December 18^th. In fact, the next occultation of Aldebaran on November 15th favors central Asia, and the event two lunations from now on December 13^th brings the path back around the North America.

A great close out for 2016, for sure. Don’t miss this week’s occultation!

October 13, 2016 by David Dickinson

This Weekend: A Hunter’s Full Moon Kicks Off Supermoon Season

The #MemoriesInDNA project intends to create an archive of human knowledge which will be sent to the Moon. Credit and copyright: John Brimacombe.

Ready for some lunar action of proxigean proportions? This weekend’s Full Moon ushers in that most (infamous?) of internet ready cultural memes: that of the Supermoon. This moniker stands above the Blood, Mini, and Full Moons both Black and Blue as the Full Moon of the year that folks can’t seem to get enough of, and astronomers love to hate.

But wait a minute: is this weekend’s Full Moon really the closest of the year?

Nope, though it’s close. But this month’s Full Moon does, however, usher in what we like to call Supermoon season.

Let us explain.

First, we’ll let you in on the Supermoon’s not so secret history. Yes, the meme arose over the last few decades, mostly due to the dastardly deeds of astrologers. Y’know, that well meaning friend/coworker/relative/anonymous person on Twitter that constantly mistakes your passion for the night sky as ‘astrology.’ Anyhow, the idea of the Supermoon has gained new life via the internet, and loosely translates as the closest Full Moon of the year. Sometimes, its dressed up with the slightly science-y sounding ‘a Full Moon along the closest 90% of its orbit’ (!) definition.

Now, to know the orbit of the Moon is to understand celestial mechanics. The Moon’s orbit is indeed elliptical, ranging from an average perigee (its closest point to the Earth) of 362,600 kilometers, to an apogee of 405,400 kilometers distant.

Fun fact: the time it takes the Moon to go from one perigee to the next (27.55 days) is one anomalistic month, a fine pedantic point to bring up to said relative/coworker the next time they refer to you as an astrologer.

And yes, the perigee Full Moon is a thing. We even like to throw about the quixotic term of the proxigean Moon, a time when tidal variations are at an extreme. Plus, all perigees are not created equal, but range from 356,400 kilometers to 370,400 kilometers distant, as the Earth-Moon system not only swings around its common barycenter, but the Sun also drags the entire orbit of the Moon around the Earth, completing one complete revolution every 8.85 years in what’s known as the precession of the line of apsides. Note that the nodes of the Moon’s orbit actually move in the opposite direction, with an 18.6 year period.

The complex motion of the Moon. Image credit: Wikimedia Commons/Geologician/Homunculus2.

Yup, the motion of the Moon has given humanity a fine study in Celestial Mechanics 101. Anyhow, we contend that a more succinct definition for a perigee ‘Supermoon’ is simply a Full Moon that falls within 24 hours of perigee. Under this definition, the Full Moon this Sunday on October 16^th occurring at 4:23 Universal Time (UT) certainly meets the criterion, occurring 19 hours and 24 minutes before perigee… as does the Full Moon of November 14^th (2.4 hours from perigee) and December 13^th (just under 24 hours from perigee).

For extra fun, said November 14^th perigee Full Moon is the closest in 30 years; expect Supermoon lunacy to ensue.

A fun place to play with Full and New Moons vs perigee and apogee past present and future is Fourmilab’s Lunar Apogee and Perigee Calculator. Hey, it’s what we do for fun. Looking over these cycles, you’ll notice a pattern of ‘supermoon seasons’ emerge, which moves forward along the calendar about a lunation a year. (that’s our friend the precession of the line of apsides at work again).

(another fun fact: the time it takes for the Moon to return to a similar phase—for example, Full back to Full—is 29.5 days, and known as a synodic month.)

The Full Moon does appear slightly larger at perigee than apogee, to the tune of 29.3′ versus 34.1′ across. This change is enough to notice with the unaided eye, though the Moon is deceptively smaller than it appears: you could, for example, line up 654 ‘Supermoons’ around the local horizon from end to end.

A 'super' vs average Full Moon. Image credit: Marco Langbroek. — A ‘super’ vs average Full Moon. Image credit: Marco Langbroek.

The October Moon is also referred to by the Algonquin Native Americans as the ‘Hunter’s Moon,’ a time to use that extra illumination to track down vital sustenance as the harsh winter approaches. Very occasionally, the Harvest Full Moon falling near the September southward equinox falls in early October (as occurs next year in 2017) and bumps the Hunter’s Moon from its monthly slot.

Be sure to stalk the rising Hunter’s Moon near perigee this weekend. Of course, we’ll be shooting at our prey with nothing more than a camera, as the Full Moon rises from behind the Andalusian foothills.

October 6, 2016October 6, 2016 by Bob King

Celebrate the Power of Naked-Eye Observing With New Book

The cover of my new book "Night Sky with the Naked Eye". The book is currently available for pre-order on Amazon and Barnes and Noble. Publication date is November 8. — This is the cover of my new book “Night Sky with the Naked Eye”, a non-technical guide to all the great things visible with the naked eye at night. It’s published by Page Street Publishing and distributed by Macmillan and currently available for **pre-order on Amazon** and **Barnes and Noble**. Publication date is November 8. Look for it here on Universe Today soon!

If you’re like a lot of people, you don’t own a telescope but still have a passionate curiosity for what’s going on over your head. Good news! There’s lots to see up there without any equipment at all. This is the premise of my new book titled Night Sky with the Naked Eye, a guide to the wonders of the night sky that anyone can enjoy and understand whether you live in an apartment in the city or cabin 50 miles from nowhere.

This diagram from the book depicts why many satellites are visible during twilight before they're eclipsed by Earth's shadow. Credit: Gary Meader — This diagram from the book depicts why many satellites are visible during twilight before they’re eclipsed by Earth’s shadow. Credit: Gary Meader

I’ve always been amazed at how accessible the universe is. To make that personal connection to the cosmos we only need acquire the habit looking up. Total eclipses, monster auroras and rich meteor showers get a lot of coverage and rightly so, but there’s a lot of other stuff up there. Little things that stoke our sense of wonder happen all the time: Earth’s rising shadow at sunset, nightly satellite flyovers, the beauty of an earth-lit crescent moon or seeing your shadow by the light of Venus.

Skywatching not only informs and delights, it has the power to expand our perspective and sense of place in the scheme of things. Gazing up at the Milky Way on a dark summer night, we feel both humbled and fortunate to be alive. The night sky’s elixir of beauty, timelessness and possibility feeds an inner quietude that can be our strength in stressful times.

Night sky observing sometimes means pleasant surprises like seeing this rare Venus pillar and corona. The book explores both celestial and atmospheric phenomena. Credit: Bob King

While the book touches on the contemplative aspects of skywatching, the bulk of it is activity-oriented, intended to inspire you to get outside. I’ve got tips on weather-watching and making the most of online resources like Clear Dark Sky and satellite imagery to help you find clear skies for that must-see special event. And if light pollution is a problem where you live, we explore ways to make a difference in reducing it as well as using online atlases to find a dark observing site.

The book covers the basics of celestial and planetary motions, how to find the brighter constellations and naked-eye deep sky objects along with suggested night sky viewing activities to share with friends and family. There are 1o chapters in all:

Chapter 1: Wave “Hi!” to the Astronauts
Chapter 2: Anticipating the Night
Chapter 3: Rockin’ N’ Rollin’ Earth
Chapter 4: Dive Into the Dippers
Chapter 5: Four Seasons of Starlight
Chapter 6: Meet the Rabbit in the Moon
Chapter 7: Face to Face with the Planets
Chapter 8: Wish Upon a Shooting Star
Chapter 9: Awed by Aurora
Chapter 10: Curiosities of the Night

This is back cover of the Night Sky with the Naked Eye book jacket. — This is back of the *Night Sky with the Naked Eye* book jacket. My book will appear back to back with another space book, titled *Incredible Stories from Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos,* by Universe Today contributing editor Nancy Atkinson. Watch for her announcement shortly.

Not everything is a billion miles away. We also take time to examine and appreciate closer-to-home phenomena that are part of the nighttime experience like lunar halos, light pillars and the aurora borealis. No observers’ guide would be complete without challenges. How about seeing craters on the moon with no optical aid or spotting the gegenschein? It’s all here.

Because the Internet has become an integral part of our lives, the book includes numerous online resources as well as useful mobile phone apps related to constellation finding and aurora tracking and tips on night sky photography.

Whether for yourself or to give as a holiday gift for a budding skywatcher, I hope you check out my book, which will be featured in a special promotion here at Universe Today. It would be my privilege to serve as your night sky guide.

October 5, 2016October 5, 2016 by David Dickinson

Seeing Double: Jupiter Returns at Dawn

Missing Jove? The largest planet in our solar system is currently on the far side of the Sun and just passed solar conjunction on September 26^th, 2016. October now sees Jupiter slowly return to the dawn sky. Follow that gas giant, as an interesting set of double shadow transits transpires in late October leading in to early November.

This particular cycle of double shadow transits involves the large Jovian moons of Europa and Ganymede.

The scene on October 24th at 23:55 UT. Image credit: Created using Starry Night Education software.

Europa and Ganymede double shadow transit season begins later this month, as both cast shadows on the Jovian cloud tops. This series of simultaneous shadow transits runs from October 17^th to November 8^th, and includes four weekly events.

The inner three large moons Io, Europa and Ganymede are in a 4:2:1 resonance. Europa orbits Jove once every 3.6 days and makes two circuits for Ganymede’s one. This means there’s a double shadow transit once every week in the current season:

The double shadow transit season of 2016. Created by author.

When can you first spy Jupiter, post solar conjunction? Catching this particular series of double shadow transits is challenging this time around, owing to the planet’s position low in the dawn twilight. The first event on October 17^th starts with Jupiter just 16 degrees west of the Sun, and the cycle ends with Jove 38 degrees west of the Sun on November 8^th.

Keep in mind, it is possible to track Jupiter up in to the daytime sky, post sunrise. To do this, you’ll need a ‘scope with a solid equatorial mount and good sidereal tracking. The trick is to lock on to Jupiter before sunrise and track it up in to the dawn sky. Be sure to physically block that dazzling rising Sun out of view behind a hill or building, and NEVER aim your telescope at the Sun!

Using this method opens up the possibility of nabbing a given double shadow event to longitudes due east of the quoted locales above.

The waning crescent Moon also passes 1.4 degrees NNE of Jupiter on October 28^th, offering another chance to spy the gas giant in the dawn sky, using the nearby crescent Moon as a guide.

The Moon and Jupiter in the daytime skies on Novemebr. — The Moon and Jupiter in the daytime skies on October 28th. Image credit: Stellarium.

And another interesting pairing is coming right up on the morning of Tuesday, October 11^th, when Mercury passes just 0.8 degrees (48′) NNE of Jupiter. Both are only 12 degrees west of the Sun at closest approach, which occurs around 10:00 UT. Still, both will appear as an interesting pseudo-double star, with Mercury shining at magnitude -1.1 and Jupiter only half a magnitude fainter at -1.6.

You can even see Jupiter coming off of solar conjunction and headed toward dawn skies courtesy of SOHO’s LASCO C3 camera:

Jupiter (arrowed) exiting the 15 degree wide field of view of SOHO's LASCO C3 camera on October 5th. Image credit: NASA/ESA/SOHO. — Jupiter (arrowed) exiting the 15 degree wide field of view of SOHO’s LASCO C3 camera on October 5th. Image credit: NASA/ESA/SOHO.

Callisto, the outermost large moon of Jupiter, ceased casting its shadow on Jupiter earlier this year on September 1^st 2016. Callisto is the only large moon that can ‘miss’ the gas giant’s cloud tops. Callisto must be involved for a triple shadow transit to occur, and the moon resumes regularly casting its shadow on Jove on December 4th, 2019.

Callisto can also experience total solar eclipses similar to those seen from the Earth during the mutual eclipse season for Jupiter’s moons, albeit shorter in duration:

And don ‘t forget: we’ve got a spacecraft currently exploring Jupiter for the next year and a half: NASA’s very own Juno.

Be sure to check out the Jovian action over the next month, gracing a dawn sky near you.

September 26, 2016 by David Dickinson

Tears of the Hunter: Our Guide to the 2016 Orionid Meteor Shower

The month of October is upon us this coming weekend, and with it, one of the better annual meteor showers is once again active: the Orionids.

In 2016, the Orionid meteors are expected to peak on October 22^nd at 2:00 UT (10:00 PM U.S. Eastern Time on October 21^st) , favoring Europe and Africa in the early morning hours. The shower is active for a one month period from October 2^nd to November 2^nd, and can vary with a Zenithal Hourly Rate (ZHR) of 10-70 meteors per hour. This year, the Orionids are expected to produce a maximum ideal ZHR of 15-25 meteors per hour. The radiant of the Orionids is located near right ascension 6 hours 24 minutes, declination 15 degrees north at the time of the peak. The radiant is in the constellation of Orion very near its juncture with Gemini and Taurus.

A gallery of Fall meteor shower radiants, including the October Orionids. Image credit: Stellarium

The Moon is at a 55% illuminated, waning gibbous phase at the peak of the Orionids, making 2016 an unfavorable year for this shower, though that shouldn’t stop you from trying. It’s true that the Moon is only 19 degrees east of the radiant in the adjacent constellation Gemini at its peak on the key morning of October 22, though it’ll move farther on through the last week of October.

In previous recent years, the Orionids produced a Zenithal Hourly Rate (ZHR) of 20 (2014) and a ZHR of 30 (2013).

The Orionid meteors strike the Earth at a moderately fast velocity of 66 km/s, and the shower tends to produce a relatively high ratio of fireballs with an r value of = 2.5. The source of the Orionids is none other than renowned comet 1/P Halley. Halley last paid the inner solar system a visit in early 1986, and will once again reach perihelion on July 28, 2061. Let’s see, by then I’ll be…

The orientation of the Earth's shadow vs, the zenith positions of the Sun, Moon and the radiant of the Orionid meteors at the expected peak of the shower on October 22nd. Image adapted from Orbitron — The orientation of the Earth’s shadow vs the zenith positions of the Sun, Moon and the radiant of the Orionid meteors at the expected during the peak of the shower on October 22nd. Image adapted from Orbitron.

Unlike most meteor showers, the Orionids display a very unpredictable maximum – many sources decline to put a precise date on the shower’s expected maximum at all. On some years, the Orionids barely top 10 per hour at their maximum, while on others they display a broad but defined peak. One 1982 study out of Czechoslovakia suggested a twin peak for this shower after looking at activity from 1944 to 1950. All good reasons to be vigilant for Orionids throughout the coming month of October.

And check out this brilliant meteor that lit up the skies over the southern UK this past weekend:

‘Tis the season for cometary dust particles to light up the night sky. Trace the path of a suspect meteor to the club of Orion, and you’ve likely sighted an Orionid meteor. But other showers showers are active in October, including:

The Draconids: Peaking around October 8th, these are debris shed by Comet 21P Giacobini-Zinner. The Draconids are prone to great outbursts, such as the 2011 and 2012 meteor storm, but are expected to yield a paltry ZHR of 10 in 2016.

The Taurids: Late October into early November is Taurid fireball season, peaking with a ZHR of 5 around October 10^th (the Southern Taurids) and November 12^th (the Northern Taurids).
The Camelopardalids: Another wildcard shower prone to periodic outbursts. 2016 is expected to be an off year for this shower, with a ZHR of 10 topping out on October 5.

And farther afield, we’ve got the Leonids (November 17^th) the Geminids (December 14^th) and the Ursids (December 22^nd) to close out 2016.

A 2015 Orionid captured by a NASA All-Sky camera atop Mt. Lemmon, Arizona. Image credit: NASA.

Observing a meteor shower like the Orionids is as simple as finding a dark site with a clear horizon, laying back and watching via good old Mark-1 eyeball. Blocking that gibbous Moon behind a building or hill will also increase your chances of catching an Orionid. Expect rates to pick up toward dawn, as the Earth turns forward and plows headlong into the meteor stream.

You can make a count of what you see and report it to the International Meteor Organization which keeps regular tabs of meteor activity.
Photographing Orionids this year might be problematic, owing to the proximity of the bright Moon, though not impossible. Again, aiming at a wide quadrant of the sky opposite to the Moon might just nab a bright Orionid meteor in profile. We like to just set our camera’s intervalometer to take a sequence of 30” exposures of the sky, and let it do the work while we’re observing visually. Nearly every meteor we’ve caught photographically turned up in later review, a testament to the limits of visual observing.

Clear skies, good luck, and send those Orionid images in the Universe Today’s Flickr forum.

September 25, 2016September 25, 2016 by Bob King

Bright Binocular Nova Discovered in Lupus

The possible nova in Lupus photographed on Sept. 25 from Australia. Credit: Joseph Brimacombe — The possible nova in Lupus photographed on Sunday, Sept. 25 from Australia. The star is now bright enough to see in binoculars for observers in the far southern U.S. and points south. Credit: **Joseph Brimacombe**

On September 20, a particular spot in the constellation Lupus the Wolf was blank of any stars brighter than 17.5 magnitude. Four nights later, as if by some magic trick, a star bright enough to be seen in binoculars popped into view. While we await official confirmation, the star’s spectrum, its tattle-tale rainbow of light, indicates it’s a nova, a sun in the throes of a thermonuclear explosion.

A bright possible nova was discovered only days ago near the 3rd magnitude star Epsilon Lupi. It shot from fainter than magnitude +17.5 to its current magnitude +6.8 in just four nights ... and it's still rising. The nova is bright enough to see in binoculars for observers in the far southern U.S., where it's visible low in the southwestern sky in late evening twilight. This map shows the sky facing southwest about an hour after sunset from Key West, Florida, latitude 24.5 degrees north. Source: Stellarium — The nova was discovered on Sept. 23 near the 3rd magnitude star Epsilon Lupi. It rose from fainter than magnitude +17.5 to its current magnitude +6.8 in just four nights … and it’s still rising. It’s visible low in the southwestern sky in late evening twilight low northern latitudes, the tropics and southern hemisphere. This map shows the sky facing southwest about an hour after sunset from Key West, Florida, latitude 24.5 degrees north. Source: Stellarium

The nova, dubbed ASASSN-16kt for now, was discovered during the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or “Assassin”), using data from the quadruple 14-cm “Cassius” telescope in CTIO, Chile. Krzysztof Stanek and team reported the new star in Astronomical Telegram #9538. By the evening of September 23 local time, the object had risen to magnitude +9.1, and it’s currently +6.8. So let’s see — that’s about an 11-magnitude jump or a 24,000-fold increase in brightness! And it’s still on the rise.

Use this chart with binoculars to help you find the likely nova. The field of view is about 5 degrees with north up. The "new star" lies between a bright triangle of stars to the east and the naked-eye star Epsilon Lupi to the west. Stars are labeled with magnitudes. Chart: Bob King, Source: Stellarium — Use this chart with binoculars to help you find the likely nova. The field of view is about 5 degrees with north up. The “new star” lies between a bright triangle of stars to the east and the naked-eye star Epsilon Lupi to the west. Stars are labeled with magnitudes. Chart: Bob King, Source: Stellarium

The star is located at R.A. 15h 29?, –44° 49.7? in the southern constellation Lupus the Wolf. Even at this low declination, the star would clear the southern horizon from places like Chicago and further south, but in late September Lupus is low in the southwestern sky. To see the nova you’ll need a clear horizon in that direction and observe from the far southern U.S. and points south. If you’ve planned a trip to the Caribbean or Hawaii in the coming weeks, your timing couldn’t have been better!

Novae occur in close binary systems where one star is a tiny but extremely compact white dwarf star. The dwarf pulls material into a disk around itself, some of which is funneled to the surface and ignites in a nova explosion. Credit: NASA — Novae occur in close binary systems where one star is a tiny but extremely compact white dwarf star. The dwarf draws material into a disk around itself, some of which is funneled to the surface and ignites in a nova explosion. Credit: NASA

I’ve drawn the map for Key West, one of southernmost locations on the U.S. mainland, where the nova stands about 7-8° high in late twilight, but you might also see it from southern Texas and the bottom of Arizona if you stand on your tippytoes. Other locales include northern Africa, Finding a good horizon is key. Observers across Central and South America, Africa, India, s. Asia and Australia, where the star is higher up in the western sky at nightfall, are favored.

Nova means “new”, but a nova isn’t a brand new star coming to life but rather an explosion that occurs on the surface of an otherwise faint star no one’s taken notice of – until the blast causes it to brighten 50,000 to 100,000 times.

You can use this AAVSO chart to find the nova and track its changing brightness. Star magnitudes are shown to the tenth with the decimal omitted. Credit: AAVSO — You can use this AAVSO chart to find the nova and track its changing brightness. Star magnitudes are shown to the tenth with the decimal omitted. Click to enlarge. Credit: AAVSO

A nova occurs in a close binary star system, where a small but extremely dense and massive (for its size) white dwarf siphons hydrogen gas from its closely-orbiting companion. After whirling around in a flattened accretion disk around the dwarf, the material gets funneled down to the star’s 150,000 F° surface where gravity compacts and heats the gas until it detonates in a titanic thermonuclear explosion. Suddenly, a faint star that wasn’t on anyone’s radar vaults a dozen magnitudes to become a standout “new star”.

Novae are relatively rare and almost always found in the plane of the Milky Way, where the stars are most concentrated. The more stars, the greater the chances of finding one in a nova outburst. Roughly a handful a year are discovered, many of those in Scorpius and Sagittarius, in the direction of the galactic bulge.

We’ll keep tabs on this new object and report back with more information and photos as they become available. You can follow the new celebrity as well as print out finder charts on the American Association of Variable Star Observers (AAVSO) website by typing ASASSN-16kt in the info boxes.

I sure wish I wasn’t stuck in Minnesota right now or I’d be staring down the wolf’s new star!