Boo! A Black Moon Halloween Weekend

Black Moon

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 30th 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 1st, 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 ‘3rd 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 26th, and the historic return of totality to the United States on August 21st, 2017.

Said high profile solar eclipse next August also has a lesser role, as it fits that old-timey definition of the 3rd 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
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 28th. This weekend, the first shot at catching the uber-thin Moon occurs for observers along a curve from southeastern Asia at dusk on October 31st 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.
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 6th.

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 31st makes the midway date only approximate: in 2016, the actual mid-point occurs on November 10th.

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

April Lunacy: Getting Ready for the Full ‘Mini-Moon’

2015 Mini-Moon

Do you welcome the extra evening light of the Full Moon, or curse the additional light pollution? Either way, this week’s Full Moon on Friday April 22nd is special. It’s the smallest Full Moon of 2016, something we here at Universe Today have christened the Mini-Moon.

Mini-Moon 2016: This year’s Mini-Moon falls on April 22nd at 5:25 Universal Time (UT), just 13 hours and 19 minutes after lunar apogee the evening prior at 16:06 UT on April 21st. Though apogee on the 21st is 406,350 km distant – a bit on the far end, but the third most distant for the year by 300 km — this week’s Full Moon is the closest to apogee for 2016 time-wise. The 2015 Mini-Moon was even closer, in the 10 hour range, but you’ll have to wait until December 10th, 2030 to find a closer occurance.

Image credit and copyright:
The Mini-Moon versus the 2011 Supermoon. Image credit and copyright: Ken Lord.

What is the Mini-Moon, you might ask? As with the often poorly defined Supermoon, we like to eschew the ambiguous ‘90% of its orbit’ definition, and simply refer to it as a Full Moon occurring within 24 hours of lunar apogee, or its farthest point from the Earth in its orbit.

Fun fact: the 29.55 day period from perigee to perigee (or lunar apogee-to-apogee) is known as an anomalistic month.

Image credit: Dave Dickinson
Mini-Moons by year for the remainder of the decade. Note that the 2020 Full Moon is also the 2nd of the month… A ‘Mini-Blue Halloween Moon?’ Image credit: Dave Dickinson

Thank our Moon’s wacky orbit for all this lunacy. Inclined 5.14 degrees relative to the ecliptic plane, the Moon returns to the same phase (say, Full back to Full) every 29.53 days, known as a synodic month. The Moon can appear 33.5′ across during perigee, and shrink to 29.4′ across near apogee.

The appearance of the Moon through one synodic period. Note that in addition to rocking back and forth (libration) and side-to-side (nutation), the Moon appears to swell and shrink in size. Wikimedia Commons graphic in the public Domain.
The appearance of the Moon through one synodic period. Note that in addition to rocking back and forth (libration) and side-to-side (nutation), the Moon appears to swell and shrink in size. Wikimedia Commons graphic in the Public Domain.

And don’t fear the ‘Green Moon,’ and rumors going ’round ye’ ole internet that promise a jaded Moon will occur in April or May; this is 100% non-reality based, seeking to join the legends of Super, Blood, and Full Moons, Black and Blue.

Image faked by: David Dickinson.
No. Just. No. Image faked by: David Dickinson.

The April Full Moon is also known as the Full Pink Moon to the Algonquin Indians. The April Full Moon, can, on occasion be the Full Moon ushering in Easter (known as the Paschal Moon) as per the rule established by the 325 AD council of Nicaea, stating Easter falls on the first Sunday after the first Full Moon after the fixed date of the Vernal Equinox of March 21st. Easter can therefore fall as late as April 25th, as next occurs on 2038. The future calculation of Easter by the Church gets the Latin supervillain-sounding name of Computus.

April 21st. Image credit: Stellarium
Looking east on the evening of April 21st. Image credit: Stellarium

Of course, the astronomical vernal equinox doesn’t always fall on March 21st, and to complicate matters even further, the Eastern Orthodox Church uses the older Julian Calendar and therefore, Easter doesn’t always align with the modern western Gregorian calendar used by the Roman Catholic Church.

The Moon can create further complications in modern timekeeping as well.

Here’s one wonderful example we recently learned of in our current travels. The Islamic calendar is exclusively based on the synodic cycle of the Moon, and loses 11 days a year in relation to the Gregorian solar calendar. Now, Morocco officially adopted Daylight Saving (or Summer) Time in 2007, opting to make the spring forward during the last weekend of March, as does the European Union to the north. However, the country reverts back to standard time during the month of Ramadan… otherwise, the break in the daily fast during summer months would fall towards local midnight.

You can see a curious future situation developing. In 2016, Ramadan runs from sundown June 5th, to July 4th. Each cycle begins with the sighting of the thin waxing crescent Moon. However, as Ramadan falls earlier, you’ll get a bizarre scenario such as 2022, when Morocco springs forward on March 27th, only to fall back to standard time six days later on April 2nd on the start of Ramadan, only to jump forward again one lunation later on April 30th!

Morocco is the only country we’ve come across in our travels that follows such a convoluted convention of timekeeping.

Fun fact #2: the next ‘Mini-Moon’ featuring a lunar eclipse occurs on July 27th 2018.

And the Spring Mini-Moon sets us up for Supermoon season six months later this coming October-November-December. Though lunar perigees less than 24 hours from Full usually occur as a trio, an apogee less than 24 hours from Full is nearly always a solitary affair, owing to the slightly slower motion of the Moon at a farther distance.

Don’t miss the shrunken Mini-Moon rising on the evenings of Thursday April 21st and Friday 22nd, coming to a sky near you.

The Mini-Moon Cometh: Catch the Smallest Full Moon of 2015 This Thursday

Supermoons. Blood Moons. Moons both Black and Blue… by now, you’d think that there was nothing new under the Sun (or Moon, as it were) when it comes to new unofficial lunar terminology.

Sure, the Moon now seems more colorful than controversial viral dress shades. Love it or loathe it, the Internet can sure set a meme in motion. And this week’s Full Moon on Thursday evening offers up one of our faves, as the most distant Full Moon of 2015 occurs on March 5th. Yup, the Mini-Moon is indeed once again upon us, a time when the Full Moon appears slightly smaller than usual as seen from the Earth. But can you really tell the difference?

The third Full Moon of the year occurs this week on Thursday, March 5th. Also known as the Worm or Sap Moon by the Algonquin tribes of New England, the moment of Full phase occurs at 18:07 Universal Time (UT) or 1:07 PM Eastern Standard Time (EST). This is also just over 10 hours after apogee, which occurs at 7:36 UT/2:36 AM EST. This month’s apogee is also an exceptionally distant one, measuring 406,385 kilometres from the center of the Earth to the center of the Moon. This is just 80 kilometres shy of the most distant apogee of 2015 on September 14th, which occurs when the Moon is near New phase.

Stellarium
Can you spy Jupiter next to the waxing gibbous Moon before sunset tonite? Credit: Stellarium.

Apogee for the Moon ranges from 404,000 to 406,700 kilometres distant, and the Full Moon appears 29.3 arc minutes across near apogee versus 34.1’ across near perigee as seen from the Earth.

This is also the closest apogee near a Full Moon time-wise until January 27th, 2032.

What is a Mini-Moon? As with a Supermoon, we prefer simply defining a Mini-Moon as a Full Moon which occurs within 24 hours of apogee. That’s much more definitive in our book rather than the cryptic and often cited ‘within 90% of its orbit’ refrain for Supermoons.

And speaking of which, we’ve got three ‘Super’ Full Moons in 2015, with the very closest Super (Duper?) Full Moon occurring within an hour of perigee on September 28th during the final total lunar eclipse of the ongoing tetrad… what will the spin doctors of the Internet make of this? A ‘Super Duper Blood Moon,’ anyone?

The path of the Moon this week also takes it towards the Fall equinoctial point in the astronomical constellation of Virgo, as it crosses Leo and nicks the corner of the non-zodiacal constellation Sextans. The Moon reaches Full two weeks prior to the Vernal Equinox, which falls this year on March 20th. Keep an eye on the Moon, as the first eclipse of 2015 and this year’s only total solar eclipse also occurs just 13 hours prior to the equinox for observers in the high Arctic. (More on that next week).

Can’t wait til Thursday? Tonight, observers across Canada, northern Maine, and Europe will see a fine occultation of the star Acubens (a.k.a. Alpha Cancri) by the 94% illuminated waxing gibbous Moon:

Credit:
The ‘shadow footprint’ for tonight’s occultation of Acubens by the Moon. Credit: Occult 4.0.1.

Alpha Cancri is 175 light years distant, and folks living along the U.S./Canadian border will be treated to a fine grazing occultation as the double star plays hide and seek along the limb of the Moon. This is number 17 in an ongoing series of 21 occultations of the star by the Moon stretching out until June 20th, 2015. There’s a wide separation of 11” between the star’s A and B components, and there are suspicions from previous lunar occultations that Alpha Cancri A may itself be a double star as well.

We caught a similar occultation of the star Lambda Geminorum by the Moon this past Friday:

Ever feel sorry for moonless Venus? This Wednesday night also offers a chance to spy Venus with a brief ‘pseudo-moon,’ as +6th magnitude Uranus passes just 15’ — less than half the apparent diameter of a Full Moon — from brilliant -4th magnitude Venus. Neith, the spurious 18th century moon of Venus lives! From the vantage point of Venus on March 4th, the Earth and Moon would shine at magnitudes -2.3 and +1.5, respectively, and sit about 4 arc minutes apart.

Starry Night Education Software.
The rising Full ‘Mini-Moon’ of March 5th. Credit: Starry Night Education Software.

Does the rising Full Moon look smaller to you than usual this week? While the apparent change in diameter from apogee to perigee is slight, it is indeed noticeable to the naked eye observers. Remember, the Moon is actually about one Earth radius (6,400 kilometres) more distant on the local horizon than when it’s directly overhead at the zenith. The Moon is also moving away from us at a current rate of 1-2 centimetres a year, meaning that Mini-Moons will get ever more distant in epochs hence.

Already, annular solar eclipses are currently more common than total ones by a ratio of about 11 to 9. The first annular eclipse as seen from the Earth went unheralded some time about 900 million to a billion years ago, and 1.4 billion years hence, the last total solar eclipse will occur.

Photo by author.
The rising waxing gibbous Moon against the daytime sky. Photo by author.

Be sure to get out and enjoy the rising Mini-Moon later this week!

-Send those Mini-Moon pics in to Universe Today.

-Looking for eclipse sci-fi? Check out Dave Dickinson’s eclipse-fueled tales Exeligmos and Shadowfall.

Astrophotos: The February 2015 ‘Black’ Moon

As our David Dickinson noted in his recent article, a new term is “creeping into the popular astronomical vernacular: that of a ‘Black Moon’.” This is the New Moon version of a Blue Moon, and is either:

  1. A month missing a Full or New Moon… this can only occur in February, as the lunar synodic period from like phase to phase is 29.5 days long. This last occurred in 2014 and will next occur in 2018.
  2. The second New Moon in a month with two. This can happen in any calendar month except February.
  3. And now for the most convoluted definition: the third New Moon in an astronomical season with four.

The February 18th New Moon met the requirements expressed in rule 3. The fourth New Moon of the season falls on March 20th, just 13 hours before the northward equinox on the same date.

But no matter what the occasion, there are always astrophotographers out to grab pictures, and here are some shared with Universe Today via email and on our Flickr page.

The sliver of the February 2015 new 'black' Moon. Credit and copyright: Héctor Barrios.
The sliver of the February 2015 new ‘black’ Moon. Credit and copyright: Héctor Barrios.
The less than 24-hour old Moon on February 19, 2015, as seen from Toronto, Canada. Credit and copyright: Michael Watson.
The less than 24-hour old Moon on February 19, 2015, as seen from Toronto, Canada. Credit and copyright: Michael Watson.
The Moon, Mars and Venus. Credit and copyright: Neil Ghosh.
The Moon, Mars and Venus. Credit and copyright: Neil Ghosh.

And remember, tonight you can see a close conjunction of the Moon, Venus and Mars. Here’s how you can photograph the event, and make sure to share your photos with Universe Today!

Black Moon: Why the New Moon on February 18th is Special

Did you hear the one about last month’s ‘supermoon?’

Yeah, we know. The hype was actually for an event that was less than spectacular, as it revolved around the first New Moon of 2015 on January 20th. Said suspect Moon was touted as ‘super’ (we prefer the quixotic term proxigean) as it occurred 18 hours prior to perigee.

Not that the first lunar perigee of 2015 was an especially close one in time or space at 359,642 kilometres distant. Is every New and Full Moon now destined to become branded ‘super’ in the never ending SEO quest to get eyeballs on web pages?

But wait, there’s more. We’ve noticed as of late that another popular term is creeping into the popular astronomical vernacular: that of a ‘Black Moon’.

Black Moons for the next decade. Created by the author.
Black Moons for the next decade. Created by the author.

We’ve written lots about Moons both of the Black and Blue variety before. We’ll also let you in on a small secret: astronomers rarely sit around observatories discussing these Moons, be they Blue, Black or Super. At most, astronomers note the weeks surrounding New as the ‘Dark of the Moon,’ a prime time to go deep for faint objects while the light polluting Moon is safely out of the sky. And yes, terms such as ‘Super’ or ‘Black Moon’ have dubious roots in astrology, while the term Blue Moon comes down to us via a curious mix-up from Sky and Telescope and the Maine Farmer’s Almanac.

Simply put, a Black Moon is the New Moon version of a Blue Moon, and is either:

  1. A month missing a Full or New Moon… this can only occur in February, as the lunar synodic period from like phase to phase is 29.5 days long. This last occurred in 2014 and will next occur in 2018.
  2. The second New Moon in a month with two. This can happen in any calendar month except February.
  3. And now for the most convoluted definition: the third New Moon in an astronomical season with four.

We bring this up because the February 18th New Moon is ‘Black’ in the sense that it meets the requirements expressed in rule 3. The fourth New Moon of the season falls on March 20th, just 13 hours before the northward equinox on the same date.

Credit: David Blanchflower.
An extremely thin crescent Moon against a low contrast twilight sky. Credit and copyright: David Blanchflower.

Such are the curious vagaries of the juxtaposition of the lunar cycle on our modern day Gregorian calendar. Unfortunately, this doesn’t mean you’ll win the lottery or be lucky in love: any Earthly woes are strictly your own affairs to deal with, Black Moon or no. Continue reading “Black Moon: Why the New Moon on February 18th is Special”