David Dickinson, Author at Universe Today

November 30, 2016December 3, 2016 by David Dickinson

Japanese Company Plans Artificial Meteor Shower

An artificial meteor shower coming to a sky-scape near you? Image credit: Sky Canvas.

A company named Sky Canvas plans to launch a colorful artificial meteor shower barrage via micro-satellite.

In the ‘strange but true department’ and a plan that would make any super-villain envious, a Japanese start-up plans to shoot meteoroids at the Earth to create the first orchestrated artificial meteor shower. The effort is benign in a bid to study the behavior of meteors and reentry characteristics, while also putting on a good show.

The idea is brainchild of Lena Okajima, who started the ALE Company which is funding the project.

“I’m very excited about this project, not only because it will turn my childhood dream into a reality, but also because it can contribute to fundamental scientific research in a new form without relying on public funds and donations,” Okajima said on her biography on the ALE website.

First, a clarification: despite what several news sites have reported, Sky Canvas/ALE have not made a formal bid to incorporate the proposal as part of the 2020 Olympics in Japan, though they’re certainly open to the idea. An artificial meteor shower during the opening ceremonies for the 2020 Olympics in Japan would definitely be a unique first!

Early testing and a first satellite launch with an as-yet unannounced carrier may occur in the later half of 2017, with another launch per year, each year following.

Long a dream of astronomer Lena Okajima, an artificial meteor shower may soon grace a sky near you.

A ball-bearing sized artificial meteor on reentry. Image credit: Sky Canvas.

Visibility Prospects

The meteoric payload will be carried into low Earth orbit aboard a small 50x 50x 50 centimetre cubical satellite dispenser. Different pellets will burn blue, orange and green. The team won’t reveal the ‘secret formula’ for the colors, but you only have to think back to high school chemistry class and Bunsen Burner flame tests to imagine the elements probably used. (hint: the green isn’t kryptonite). Laboratory tests suggest that the artificial meteors should be visible from about 200 kilometers (120 miles) away. Said satellite dispenser will carry about a 300-500 pellets. At say, a meteor a second, such a display would last from five to just over eight minutes in duration.

A test carried out in the lab verified that the brightness for the pellets should be right around apparent magnitude -0.86, just a bit fainter than the brightest star in the sky Sirius at magnitude -1.5.

Looking for an artificial meteor shower to light up your next event? Well, such a performance isn’t cheap. With a roughly eight million dollar price tag, an artificial meteor shower breaks down to about $16,000 USD per meteor.

The plan is to place the 50 kilogram satellite (fully loaded) in a sun-synchronous orbit. This is a highly inclined retrograde polar orbit, also favored by Earth-observing and (supervillians take note) spy satellites.

The visibility prospects for Sky Canvas over a major urban area. Image credit: Sky Canvas.

The Sky Canvas system will also have the ability to ‘weather abort’ about 100 minutes prior to the event in case of inclement weather. Once in low Earth orbit, said satellite will orbit the planet once every 90 minutes. Such a dispenser is a one shot affair, and will burn up shortly after use.

Are artificial meteor showers a great idea? On one hand, it might be a great educational resource, and a way to get the general public excited about space and astronomy. Still, for those of us who have endured many an early morning vigil for the occasional surprise flash of a meteor, there’s perhaps something a bit kitschy about meteor showers on demand. It’s also slightly reminiscent of the early Space Age ideas to create nighttime illumination via large mirrors floating in space, or place advertising (!) in low Earth orbit. Streaks of artificial satellites already routinely photobomb deep sky images… do we want to contend with orbiting Pepsi logos as well?

Some may also bemoan the advent of yet more artificial light – however ephemeral — streaking across the already brightening sky. And here’s another possible dilemma: will a -1 magnitude artificial meteor appear all that impressive from the already garish glare of downtown Tokyo, Las Vegas or Dubai? Still, I’d make the trip to see the world’s first artificial meteor shower… and humanity already routinely creates similar unheralded “shows” every time a piece of space junk reenters the Earth’s atmosphere.

I also can’t help but think of the fictional metal band Disaster Area from Douglas Adams’ Hitchhiker’s Guide to the Galaxy, which ended each concert with a sun-diving spaceship.

There are also possible practical applications for the project, including understanding meteor showers, spacecraft reentry, studying the upper atmosphere, etc. And though this may seem far-fetched, NASA already uses luminous chemicals dispersed from sounding rockets to do the same thing.

JAXA has already performed similar artificial meteor experiments here on Earth using an arc-heated wind tunnel laboratory, mimicking and modeling the Chelyabinsk meteor and the asteroid sample return mission Hayabusa-1 and the future return of Hayabusa-2.

Just maybe though, light pollution awareness might prove to be the project’s greatest strength. An artificial meteor shower might just cause city dwellers and urban planners to turn the lights down, and simply gaze up at the night sky for a brief moment.

November 15, 2016 by David Dickinson

When Good Showers Turn Bad: The 2016 Leonids

A flash of light recently reminded us of the most stunning sight we ever saw.

We managed to catch an early Leonid meteor this past Saturday morning while waiting for the new Chinese space station Tiangong-2 to pass over southern Spain. The Leonids are active this week, and although the light-polluting just past Super Moon lurks nearby, we’ve learned to never ignore this shower, even on an off year.

First though, here’s a rundown on what’s up with the Leonids in 2016:

The Leonid meteors are expected to peak on the night of Thursday, November 17^thinto the morning of Friday, November 18^th. The shower is active for a 25 day span from November 5^th to November 30^th and though the Leonids can vary with an Zenithal Hourly Rate (ZHR) of thousands of meteors per hour, and short outbursts briefly topping hundreds of thousands per hour, in 2016, the Leonids are expected to produce a maximum ideal ZHR of only 10 to 15 meteors per hour. The radiant of the Leonids is located at right ascension 10 hours 8 minutes, declination 21.6 degrees north at the time of the peak, in the Sickle or backwards Question Mark asterism of the astronomical constellation of Leo the Lion.

The rising radiant of the Leonids versus the nearby waning gibbous Moon. image credit: Stellarium. — The rising radiant of the Leonids versus the nearby waning gibbous Moon. Image credit: Stellarium.

The source of the Leonids is periodic Comet 55P/Tempel-Tuttle.

Now, for the bad news. The Moon is an 82% illuminated, waning gibbous phase at the peak of the Leonids, making 2016 an unfavorable year for this shower. In fact, the Moon is located just 42 degrees from the shower’s radiant in the nearby constellation of Gemini at the shower’s peak on Friday morning. In previous years, the Leonids produced a ZHR numbering in the 15-20 per hour. The estimated ZHR last topped 100 in 2008.

The Leonid meteors strike the Earth at a moderate/fast velocity of 71 km/s, and produce many fireballs with an r value of 2.5.

The Leonids are notorious for producing storms of epic proportions every 33 years. This last occurred in years surrounding 1999, and isn’t expected to occur again until around 2032. Some older observers still remember the great Leonid meteor storm over the southwestern United States in 1966, and the U.S. East Coast witnessed a massive storm in 1833.

A woodcut engraving depicting the 1833 Leonids over Niagara Falls. Public Domain image.

We can attest to what the Leonids are capable of. We saw an amazing display from the shower in 1998 from Al Jaber Air Base in Kuwait, with an estimated rate of around 900 per hour towards dawn. When a shower edges towards a zenithal hourly rate of 1,000, you’re seeing meteors every few seconds, with fireballs lighting up the desert night.

And it is possible to defeat the waning gibbous Moon. Though the Moon is near the zenith as seen from the mid-northern latitudes in the early AM hours (the best time to watch the shower,) its almost always possible to view the shower with the Moon blocked behind a house or hill… unless you have the bad luck of viewing from latitude 20 degrees north, where the Moon crosses directly through the zenith on Friday morning.

But take heart, as we’re past the halfway mark in 2014, headed to the Leonid ‘storm years’ of the early 2030s.

Don’t miss the 2016 Leonids… if for no other reason, to catch a flash of storms to come.

November 10, 2016February 3, 2017 by David Dickinson

Preview: Comet 45P/Honda–Mrkos–Pajdušáková Brightens in December

Comet 45P/Honda-Mrkos-Pajdušáková From October 1st, 2011 taken with a 10"/3.8 Newtonian and CCD imager. Image credit and copyright: Michael Jäger.

Looking for a good binocular comet? Well, if luck is on our side, we should be getting our first looks at periodic Comet 45P/Honda-Mrkos-Pajdušáková as it tops +10th magnitude in dusk skies over the next few weeks.

The swift path of Comet 45P/Honda-Mrkos-Pajdušáková on the nights of February 9th to February 12th. Image credit: Starry Night.

Comet 45P/Honda-Mrkos-Pajdušáková is expected to reach maximum brightness around late February 2017. Discovered independently by astronomers Minoru Honda, Antonin Mrkos and L’udmila Pajdušáková on December 3^rd, 1948, Comet 45P/Honda-Mrkos-Pajdušáková orbits the Sun once every 5.25 years on a short period orbit. Comet 45P/Honda-Mrkos-Pajdušáková is set to break binocular +10^th magnitude brightness in mid-December 2017, and may reach a maximum brightness of magnitude +7 from January through February 2017.

Slovak astronomer ?udmila Pajdušáková, co-discoverer of 5 comets, including Comet 45P/Honda-Mrkos-Pajdušáková. Image credit: The Skalnaté Pleso Observatory.

Currently and through the end of 2016, the comet sits towards the center of the Milky Way Galaxy in Sagittarius at a faint +15^th magnitude in the evening sky. The comet may break +10^th magnitude and become very briefly visible in the first few weeks of December before getting too close to the Sun to observe in late 2016 and crossing into the morning sky in early 2017.

The path of Comet 45/P from mid-November through December 15th, 2016. Image credit: Starry Night.

Visibility prospects: At its brightest, Comet 45P/Honda-Mrkos-Pajdušáková will be passing through the constellation Hercules during closest approach on February 11^th. The comet then passes through the constellations of Corona Borealis, Boötes, Canes Venatici, Ursa Major into Leo through to the end of February as it recedes. In the second week of February, the comet is visible in the dawn sky 82 degrees west of the Sun at maximum brightness. This apparition favors the northern hemisphere. The comet will reach perihelion on December 29^th, 2016 at 0.53 Astronomical Units (AU) from the Sun, and the comet passes just 0.08 AU (7.4 million miles) from the Earth on February 11^th at 14:44 UT. The comet made a slightly closer pass in 2011, and was a fine binocular object that time around. At its closest, the comet will cross nine degrees of sky from one night to the next. Some notable dates for comet 45P/Honda-Mrkos-Pajdušáková are:

November 23^rd: Venus passes 6′ from the comet.

December 12^th: May break 10^th magnitude.

December 14^th: Passes near M75.

December 15^th: Crosses into the constellation Capricornus.

January 4^th: Passes near the +4^th magnitude star Theta Capricorni

January 10^th: Crosses the ecliptic northward.

January 16^th: Passes into Aquarius.

January 22^nd: Passes near NGC 7009, M72 and M73.

January 25^th: Passes 8 degrees from the Sun and into the dawn sky.

January 28^th: Crosses into Aquila.

February 3^rd: Crosses the celestial equator northward.

February 4^th: Passes 4′ from the star +3.3 magnitude star Delta Aquilae.

February 6^th: Crosses the Galactic equator.

February 7^th: Crosses into Ophiuchus.

February 9^th: Crosses into Hercules.

February 16^th: makes a wide pass near M3.

February 19^th: Drops back below +10^th magnitude.

The path of Comet 45P/Honda-Mrkos-Pajdušáková through the inner solar system. Image credit: NASA/JPL.

This is the final close (less than 0.1 AU) passage of Comet 45P/Honda-Mrkos-Pajdušáková near the Earth for this century.

On July 1^st 1770, Comet D/1770 L1 Lexell passed 0.0151AU from the Earth; a comet in 1491 may have passed closer. Next year’s passage of 45P/Honda-Mrkos-Pajdušáková ranks as the 21^st closest passage of a comet near the Earth.

The light curve of Comet 45/P Honda-Mrkos-Pajdušáková. Credit: Seiichi Yoshida’s *Weekly Information About Bright Comets.*

Why do comets end up with such cumbersome names? Well, comets derive their names from the first three discovers that submit the find within a 24 hour period to the Minor Planet Center’s Central Bereau for Astronomical Telegrams, which, in fact, received its last ‘telegram’ during the discovery of Comet Hale-Bopp around two decades ago. Increasingly, comets are receiving names of all sky surveys such as LINEAR and PanSTARRS from robotic competition against amateur hunters. It does seem like you need an umlaut or the chemical symbol for boron to in your moniker to qualify these days… rare is the ‘Comet Smith.’ But hey, it’s still fun to watch science journalists try and spell the Icelandic volcano Eyjafjallajökull and comet Churyumov-Gerasimenko over and over… Perhaps, we should insist that our first comet discovery is actually spelled Comet Dîckînsðn…

And Comet 45/P is just one of the fine binocular comets on deck for 2017. We’re also expecting Comet 41P/Tuttle-Giacobini-Kresák, 2/P Encke, C/2015 ER61 PanSTARRS Comet C/2015 V2 Johnson to break +10^th magnitude next year… and the next great naked eye ‘Comet of the Century’ could light up the skies at any time.

Goldstone radar pings comet 45/P back in 2011. Image credit: NASA.

Binoculars are the best tool to observe bright comets, as they allow you to simply sweep the star field and admire the full beauty of a comet, coma, tail(s) and all. Keep in mind, a comet will often appear visually fainter than its quoted brightness… this is because, like nebulae, that intrinsic magnitude is ‘smeared out’ over an extended area. To my eye, a binocular comet often looks like a fuzzy, unresolved globular cluster that stubbornly refuses to snap into focus.

Don’t miss your first looks at Comet 45/P 45P/Honda-Mrkos-Pajdušáková, as it spans 2016 into 2017.

November 9, 2016November 9, 2016 by David Dickinson

November’s Supermoon 2016 – Closest of a Lifetime?

The 2015 Supermoon. Image credit and copyright: Wils 888.

What’s that, rising in the sky?

By now, you’ve heard the news. We’ll spare you the “it’s a bird, it’s a plane…” routine to usher in the Supermoon 2016. This month’s Full Moon is not only the closest for the year, but the nearest Full Moon for a 80 year plus span.

Like Blue and Black Moons, a Supermoon is more of a cultural phenomenon than a true astronomical event. The Moon’s orbit is elliptical, taking it from 362,600 to 405,400 km from the Earth in the course of its 27.55 day anomalistic orbit from one perigee to the next. For the purposes of this week’s discussion, we consider a Supermoon as when the Full Moon occurs within 24 hours of perigee, and a Minimoon as when the Full Moon occurs within 24 hours of apogee. From the Earth, the Moon varies in apparent size from 29.3” to 34.1” across. This month, the Moon reaches perigee on November 14^th at 356,511 kilometers distant, 2 hours and 22 minutes before Full.

A perigee 'Supermoon' versus an apogee 'Minimoon'. Image credit and copyright: Raven Yu. — A perigee ‘Supermoon’ versus an apogee ‘Minimoon’. Image credit and copyright: Raven Yu.

This is the closest perigee Moon for 2016, beating out the April 7^th, 2016 perigee Moon by just 652 kilometers. Perigee can vary over a span of 2,800 kilometers. In the 21^st century, the farthest lunar perigee (think the ‘most distant near point’) occurs on January 3^rd, 2100 at 370,356 kilometers distant, while the closest perigee of the century (356,425 kilometers) occurs on December 6^th , 2052.

When the Moon reaches Full on November 14^th at 13:51 UT, it’s just 356,520 kilometers distant, (that is , as measured from the Earth’s center) the closest Full Moon since January 26^th, 1948 (356,490 km) and until November 25^th , 2034 (356,446 km) losing out to either dates by just 21 kilometers.

Why does perigee vary? Well, as the Moon orbits the Earth, the Sun tugs our large natural satellite’s orbit around as well, in an 8.85 year cycle known as the precession of the line of apsides. Earth’s orbit is elliptical as well, and the tugging of the Sun (and to a much lesser degree, the other planets in the solar system) alters the perigee and apogee points slightly based on where the Earth-Moon pair fall in their swing about a common barycenter.

The November Full Moon is also known as the Full Beaver Moon by the Algonquin Native Americans, a good time to ensure a supply of winter furs before the swamps froze over. A good sign that even in 2016, ‘Winter is Coming.’

Does the Moon look any larger to you than usual as it rises to the east opposite to the setting Sun on Monday night? When the Moon reaches Full, it passes the zenith as seen from the central Indian Ocean region just south of Sri Lanka, 354,416 km distant. Of course, as the Moon rises, it’s actually one full Earth radii more distant than when straight overhead at the zenith.

A side-by-side 'Super' vs 'Minimoon.' Image credit and copyright: Marco Langbroek. — A side-by-side ‘Super’ vs ‘Minimoon.’ Image credit and copyright: Marco Langbroek.

Would you notice any difference in the size of the November Full Moon, if you didn’t know better? The 4′ odd difference between an apogee and perigee Full Moon is certainly discernible in side-by-side images… but it’s interesting to note that early cultures did not uncover the elliptical nature of the Moon’s motion, though it certainly would have been possible. Crystalline spheres ruled the day, a sort of perfection that was just tough to break in the minds of many.

Be sure to enjoy the rising Full Moon on Monday night, the largest for many years to come.

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.

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 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.