Catch ‘The Great American Occultation’ of Aldebaran Saturday Night

The Moon nearing Aldebaran on February 5th, 2017. Image credit and copyright: Chris Lyons.

Ever watch the Moon cover up a star? There’s a great chance to see just such an event this coming weekend, when the waxing gibbous Moon occults (passes in front of)  the bright star Aldebaran for much of North America on Saturday night, March 4th.

Shining at magnitude +0.85, Aldebaran is the brightest star that lies along the Moon’s path in the current epoch, and is one of four +1st magnitude stars that the Moon can occult. The other three are Regulus, Antares and Spica. This is the 29th in a series of 49 occultations of Aldebaran worldwide spanning from January 29th, 2015 to September 3rd, 2018, meaning Aldebaran hides behind the Moon once every lunation as it crosses through the constellation Taurus and the Hyades open star cluster in 2017. Like eclipses belonging to the same saros cycle, successive occultations of bright stars shift westward by about 120 degrees westward longitude and slowly drift to the north. Europe saw last month’s occultation of Aldebaran, and Asia is up next month on April 1st.

The occultation footprint for Saturday night’s event. Credit: Occult 4.2 software.

All of the contiguous ‘lower 48 states’ except northern New England see Saturday night’s occultation, and under dark skies, to boot. It’s a close miss for Canada. Mexico, central America and the Caribbean will also witness the event under dark skies. Hawaii will see the event under daytime skies. We can attest that this is indeed possible using binocs or a telescope, as we caught Aldebaran near the daytime Moon during last month’s event.

Occultations give us a chance to see a split second magic act, in a Universe that often unfolds over eons and epochs. The motion you’re seeing is mostly that of the Moon, and to a lesser extent, that of the Earth as the star abruptly ‘winks out’.

Observers in northern tier states might witness an additional spectacle, as Aldebaran grazes the northern limb of the Moon. This can make for an unforgettable sight, as the star successively winks in at out from behind lunar peaks and valleys. The graze line for Saturday night follows the U.S./Canadian border from Washington state, Idaho and Montana, then transects North Dakota, Minnesota just below Duluth and northern Wisconsin, Michigan and New York and Connecticut. Brad Timerson over at the international Occultation Timing Association has a good page set up for the circumstances for the grazing event, and the IOTA has a page detailing ingress (start) and egress times for the event for specific cities.

The northern limit grazeline for Saturday night’s occultation. Credit: USAF/Wikimedia Commons/Dave Dickinson

You’ll be able to see the occultation of Aldebaran with the unaided eye, no telescope over binocular needed, though it will be fun to follow along with optics as well. The ingress along the leading dark limb of the Moon is always more dramatic, while reemergence on the bright limb is a more subtle affair.

The path of the occultation for select cities. Credit: Stellarium.

A simple video aimed afocally through a telescope eyepiece can easily capture the event. We like to run WWV radio on AM shortwave in the background while video recording so as to get a good time hack of the event on audio. Finally, set up early, watch those battery levels in the frigid March night, and be sure to balance out your exposure times to capture both Aldebaran and the dazzling limb of the Moon.

Can you see it? The Moon paired with Aldebaran on February 5th. Image credit and copyright: Lucca Ruggiero.

Anyone Live-casting the event? It’ll be a tough one low to the horizon here in central Florida, but a livestream would certainly be possible for folks westward with Aldebaran and the Moon high in the sky. Let us know of any planned webcasts, and we’ll promote accordingly.

The Moon also occults several other bright stars this week, leading up to an occultation of Regulus on March 10th favoring the southern Atlantic. Read all about occultations, eclipses, comets and more in our free e-book, 101 Astronomical Events for 2017 from Universe Today.

Don’t miss Saturday night’s stunning occultation, and let us know of your tales of astronomical tribulation and triumph.

-Send those astro-images in to Universe Today’s Flickr forum, and you might just see ’em featured here in a future article.

This Week: Occultations of Aldebaran, Regulus vs. the Supermoon

Aldebaran Occultation

It’s a busy week for the Moon. While our large solitary natural satellite reaches Full and interferes with the 2016 Geminids, it’s also beginning a series of complex bright star occultations of Aldebaran and Regulus, giving us a taste of things to come in 2017.

First up, here’s the lowdown on this week’s occultation of Aldebaran by the Moon, coming right up tonight:

Aldebaran Occultation
The footprint for tonight’s occultation of Aldebaran by the Moon. You can find specific ingress and egress times for major cities near you on the IOTA event page. Credit: Occult 4.2.

The 99% illuminated waxing gibbous Moon occults the +0.9 magnitude star Aldebaran on Monday, December 12th. The Moon is just 19 hours and 30 minutes before reaching Full during the event. Both are located 167 degrees east of the Sun at the time of the event. The central time of conjunction is 4:37 Universal Time (UT). The event occurs during the daylight hours over Hawaii at dusk during Moonrise, and under darkness for Mexico, most of Canada and the contiguous United States. The event also includes the United Kingdom and southwestern Europe at Moonset near early dawn. This is the final occultation of Aldebaran by the Moon for 2016; The Moon will next occult Aldebaran on January 9th, 2017. This is occultation 26 in the current series of 49, running from January 29th, 2015 to September 3rd, 2018.

Moon Gibraltar
The view from Gibraltar just prior to this week’s occultation of Aldebaran by the Moon. Credit: Stellarium.

Four 1st magnitude stars are along the Moon’s path in the current epoch: Regulus, Aldebaran, Antares and Spica. 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). The Moon also occults Regulus 220 times this century, and occultations of Spica and Antares resume on May 2024 and July 2023, respectively.

And yes, this Supermoon 3 of 3 for 2016, though actual perigee occurs at 23:28 UT tonight, 39 minutes past our own ’24 hour from Full’ rule. The Moon reaches Full on Wednesday, December 14th at just past midnight at 00:07 UT. This is also the closest Full Moon to the December 21st winter solstice next week, and the Full Moon will ride high in the sky this week for northern hemisphere observers on long winter nights.

Keep an eye out for Geminid meteors tonight as well… sure, 2016 may be an off year for this usually spectacular shower, but a few brighter fireballs may still punch through the lunar light pollution.

Clouded out? Be sure to catch the Supermoon action tomorrow night live online starting at 16:00 UT, courtesy of Gianluca Masi and the Virtual Telescope Project.

And there’s more. This coming weekend marks the start of an upcoming new cycle of occultations of Regulus by the Moon. These run right through 2018, as the Moon visits the bright star Regulus five days after crossing the Hyades and occulting Aldebaran for every lunation pass in 2017.

Here’s the specifics for Sunday’s event:

Moon Regulus
The footprint for Sunday’s occultation of Regulus by the Moon. You can find specific ingress and egress times for major cities near you on the IOTA event page. Credit: Occult 4.2.

The 73% illuminated waning gibbous Moon occults the +1.4 magnitude star Regulus on Sunday, December 18th. The Moon is just four days past Full during the event. Both are located 117 degrees west of the Sun at the time of the event. The central time of conjunction is 18:38 Universal Time (UT). The event occurs during the daylight hours over Tasmania, and under darkness for the southwestern tip of Australia, including Perth. The Moon will next occult Regulus on January 15th, 2017. This is the first occultation in a new series of nineteen, running from this weekend to April 24th, 2018.

moon regulus
The view of Sunday’s event from Perth, Australia. Credit: Stellarium.

It’s worth noting that the graze line for Sunday’s occultation of Regulus by the Moon runs just north of the Australian city of Perth and the Perth Observatory… let us know if anyone ‘Down Under’ witnesses the first occultation of Regulus in the new cycle.

Can you spy Regulus’ white dwarf companion? Located 77 light years distant, the Regulus system has at least four components: a B/C pair shining at a combined magnitude of +8, with an apparent separation of 3”, (5,000 AU physical distance in a ~600 year orbit) and an unseen white dwarf companion in a tight 40 day orbit. We know that said white dwarf companion exists from spectroscopic analysis… and it would shine at an easy magnitude +13, were it not near dazzling Regulus shining over 10,000 times brighter. Could this elusive companion turn up just moments before the reappearance of Regulus from behind the Moon? Remember, the dark limb of the Moon leads the way during waxing phases, then trails as the Moon wanes. These and other amazing facts are included in our forthcoming free guide to 101 Astronomical Events to watch out for in 2017.

Regulus occultations
Every occultation of Regulus for the upcoming cycle. Credit: Occult 4.2.

Follow that Moon, and don’t miss these fine astro-events coming to sky above you this week!

Watch the Moon Occult Vesta and Aldebaran This Weekend

So, did you miss yesterday’s occultation of Venus by the Moon? It was a tough one, to be sure, as the footpath for the event crossed Europe and Asia in the daytime. Watch that Moon, though, as it crosses back into the evening sky later this week, and occults (passes in front of) the bright star Aldebaran for eastern North America and, for Hawaii-based observers, actually covers the brightest of the asteroids, 4 Vesta. Continue reading “Watch the Moon Occult Vesta and Aldebaran This Weekend”

Lights Out: A Fine Occultation of Aldebaran Spans the Atlantic

They braved the cold, cursed the clouds, wrestled with frozen telescope focusers and more, as dedicated astros worked to catch the first occultation of the bright star Aldebaran for 2016 by the waxing gibbous Moon.

The event went down last night into the wee hours of the morning, and was visible across North America into western Europe and the United Kingdom. Continue reading “Lights Out: A Fine Occultation of Aldebaran Spans the Atlantic”

Challenge-Watch the Daytime Moon Occult Aldebaran for North America This Friday

How about that total lunar eclipse this past Sunday? Keep an eye of the waning gibbous Moon this week, as it begins a dramatic dive across the ecliptic towards a series of photogenic conjunctions throughout October.

The Main Event: This week’s highlight is an occultation of the bright +0.9 magnitude star Aldebaran (Alpha Tauri) by the waning gibbous Moon on Friday morning October 2nd.

Image credit: Occult 4.0 software
The occultation footprint for Friday’s occultation of Aldebaran by the Moon, with pre-dawn, dawn and post-dawn zones annotated. Image credit: Occult 4.0 software

This occurs in the pre-dawn hours for Alaskan residents, and under favorable dawn twilight skies along the U.S. and Canadian Pacific west coast; the remainder of the contiguous United States and Canada will see the occultation transpire after sunrise.   This is the 10th of 49 occultations of Aldebaran by the Moon worldwide running from January 29th, 2015 through September 3rd, 2018. The Moon will be at 74% waning gibbous phase, and Aldebaran will disappear behind its illuminated limb to reappear from behind its trailing dark limb.

Check out this amazing Vine of the last occultation of Aldebaran by the Moon courtesy of Andrew Symes @FailedProtostar:

It’s interesting to note that the southern graze-line for the occultation roughly follows the U.S./Mexican border. Seeing a bright star wink in and out from behind the lunar valleys can be an unforgettable sight, adding an eerie 3D perspective to the view. A detailed analysis of the event can even help model the rugged limb of the Moon.

Hunting stars and planets in the daytime can be an interesting feat of visual athletics. We’ve managed to spy Aldebaran near the lunar limb with binoculars during an occultation witnessed from Alaska on September 4th, 1996, and can attest that it’s quite possible to see a +1st magnitude star near the Moon with optical aid. A clear blue sky is key.  The Greek philosopher Thales noted that stars could be seen from the bottom of a well (though perhaps he’d fallen down a well or two too many in his time)… Friday’s event should push your local seeing to its limits. Start tracking Aldebaran before local sunrise, and you should be able to follow it all the way to the lunar limb, clear skies willing.

Image credit: Dave Dickinson/Stellarium
The occultation path for various locales across the United States Friday morning. Image credit: Dave Dickinson/Stellarium

Here’s a listing of times for key events for Friday from around the U.S. Check out The International Occultation Timing Association’s page for the event for an extensive listing:

Image credit: Dave Dickinson
Key times for the occultation for the same locales depicted in the graphic above, along with the lunar elevation (altitude) above the local horizon at the time noted. Image credit: Dave Dickinson

And whenever the Moon meets Aldebaran, it has to cross the open star cluster of the Hyades to get there, meaning there’ll be many other worthy occultations of moderately bright stars around October 2nd as well.  Gamma Tauri, 75 Tauri, Theta^1 Tauri, and SAO93975 are all occulted by the Moon on the morning of October 2nd leading up to the Aldebaran occultation; particularly intriguing is the grazing occultation of +5 magnitude 75 Tauri across the Florida peninsula.

The path of the moon through the Hyades this weekend. Image credit: Starry Night Education software
The path of the Moon through the Hyades this weekend. Image credit: Starry Night Education software

Fun fact: the Moon can, on occasion, occult members of the M45 Pleiades star cluster as well, as last occurred in 2010, and will next occur on 2023.

Chasing the Moon through October

Follow that Moon for the following dates with astronomical destiny worldwide:

  • The Moon reaches Last Quarter phase on Sunday, October 4th at 21:06 UT/5:06 PM EDT.
  • A close pass with Venus on October 8th, with a brilliant occultation visible in the pre-dawn hours from Australia.
  • A tight photogenic grouping of the Moon, Mars and Jupiter in a four degree circle on the morning on October 9th;
  • A close pass of the Moon just 36 hours from New near Mercury on the morning of Sunday, October 11th, with another occultation of the planet visible from Chile at dawn;
  • And finally, New Moon (sans eclipse, this time) occurring at 00:06 UT on October 13th, marking the start of lunation 1148.

Why occultations? Consider the wow factor; light from Aldebaran left about 65 years ago, before the start of the Space Age, only to get ‘photobombed’ by the occulting Moon at the last moment. Four bright stars (Regulus, Spica, Antares and Aldebaran) lie along the Moon’s path in our current epoch. Dial the celestial scene back about two millennia ago, and the Moon was also capable of occulting the bright star Pollux in the astronomical constellation of Gemini as well.

We’ll be running video for the event clear skies willing Friday morning here from Hudson, Florida in the Tampa Bay area. And as always, let us know of your tales of astronomical tribulation and triumph!