The Birth of a Saros – This Weekend’s Hidden Eclipse

(Photo by Author)

As the first eclipse season of 2013 comes to an end this weekend, an extremely subtle lunar eclipse occurs on the night of Friday, May 24th going into the morning of Saturday, May 25th. And we do mean subtle, as in invisible to the naked eye… this eclipse only lasts 34 minutes in duration and less than 2% of the disk of the Moon enters the bright outer penumbra of the Earth’s shadow!

So, why talk about such a non-event at all?

Great things come from such humble beginnings. And while this weekend’s eclipse is one mostly for the almanacs and astronomical tables rather than a true observational event, it also marks the start of a new lunar saros cycle.

This weekend’s eclipse is one of five for 2013, a year which contains two solars and three lunars. This eclipse marks the end of the first “eclipse season” of the year, a time when the intersection of the Moon’s orbit (known as nodes) and the ecliptic nearly coincide with the position of the Sun (for a solar eclipse at New Moon) and the Earth’s shadow (for a lunar eclipse at Full Moon).

The current season began with a very slight partial eclipse on April 25th, followed by an annular eclipse on May 10th. It will last only 33 minutes and 45 seconds in duration starting at 03:53:11 UTC on May 25th. The Moon will be high over the Americas at the time, but again, shading on the southern limb of the Moon will be too slight to be seen.

Curiously, SLOOH will be providing live coverage of the eclipse, although again, it will be too slight to see.

Starry Night
The Full Moon just nicks the Earth’s penumbra in the early morning hours of May 25th. (Created by the author in Starry Night).

What is a saros? A saros is a period of 18 years 11 days and 8 hours after which an eclipse cycle lines up, producing a similar eclipse to the one that preceded it 18 years before. Note that due to its 8 hour offset, the Earth will have rotated 120° and the visibility region will have shifted westward.

In said period, three lunar cycles very nearly line up;

The Anomalistic month (the period the Moon takes to go from one perigee to another) = 27.555 days.

The Draconic month (the period the Moon takes to return to the same node) = 27.212 days.

The Synodic month (the most familiar one, the period between similar phases) = 29.531 days.

Note that:

239 Anomalistic months = 239×27.555= 6585.645 days.

242 Draconic months = 242×27.212=6585.304 days.

223 Synodic months = 223×29.531=6585.413 days.

There’s that mis-alignment of a third of a day again (8 hours) for every 18 years and 11 days. This also causes the node of each eclipse in the cycle to drift eastward by 0.5° along the ecliptic. Thus, each eclipse isn’t exactly the same. A lunar saros series starts with a very brief penumbral like this weekend’s, becomes deeper and deeper every 18+ year period until partial and total eclipses begin centuries down the road. Thereafter, the cycle reverses, until a final faint penumbral marks the end of the lunar saros.

diagram
The progression of selected eclipses of the same saros cycle. (Credit: Matthew Zimmerman. Wikimedia Commons graphic in the Public Domain).

After this weekend’s eclipse, the next start of a lunar saros won’t occur until November 8th 2060 with the start of saros 156. The last new saros series (number 149) began on June 13th, 1984.

There are numbered saros series for both lunar and solar eclipses. There are currently 41 saroses (the plural of saros) active with the inclusion of this weekend’s start of lunar saros 150.

Saros 150, of which this eclipse is the 1st of 71, will last for just over 1,262 years. It will begin to produce partial eclipses on August 20th, 2157 and produce its 1st total on its 32nd lunar eclipse on April 29th, 2572.

It amazes me that ancient cultures such as the Chaldeans new of saros cycles and could predict eclipses. Being geographically isolated, lunar eclipse cycles would have been easier to decipher than solar ones, as you only have to be on the Moonward facing hemisphere of the Earth to witness the eclipse. They may well have stumbled upon the saros while attempting to calculate a slightly longer 19 year period known as a Metonic cycle to align ancient luni-solar calendars.

And yes, that 8 hour offset also means that after a triple saros period, lunar and solar eclipses of the same saros series do return to roughly the same longitude every 54 years & 34 days. This is known as an exeligmos, and if you get this on a triple-word score in Scrabble, you can safely retire from the game.

NASA
The theoretical visibility circumstances for this week’s penumbral eclipse. (Credit: F. Espenak/NASA/GSFC).

And while this eclipse is more of academic than observational interest, you can always enjoy the light of a brilliant Full Moon. The May Full Moon is referred to as the Flower, Milk, and Corn Planting Moon by the Algonquian Indians of North America, alluding the latent season of Spring.

Also, keep an eye out for several conjunctions and occultations this week by the Moon with bright stars and planets.

The first up is the bright star Spica (Alpha Virginis) which gets occulted by the waxing gibbous Moon around ~11:00 UT on Wednesday, May 22nd for viewers across northern Australia, southern Asia and the South Pacific. Spica is one of four stars brighter than magnitude +1.5 that the Moon can occult, the others being Antares, Aldebaran and Regulus. This is the 6th occultation in a cycle of 13 of Spica by the Moon spanning 2013.

The planet Saturn will lie about 4° north of the waxing gibbous Moon on the following evening of May 23rd.

Also, watch for an occultation of the +2.6th magnitude star Beta Scorpii on the evening of May 24th around the time of the lunar eclipse. This will be a difficult one, as the Moon will be near 100% illumination. Conjunction of the Moon and Beta Scorpii in right ascension occurs at 3:04 UT on May 25th, about 2.5 hours after Full. The occultation will span the southeastern US, Caribbean, northern South America and western Africa.

Created by Author
Visibility path of the occultation of Beta Scorpii by the Moon. (Credit: Occult 4.1.0.2).

2013 isn’t a grand year for eclipses. We’ve got two more in the late season of the year, another slightly deeper penumbral on October 18th and a hybrid solar eclipse on November 3rd. And when, may you ask, will we FINALLY have another total lunar eclipse? Stick around ‘til U.S. Tax Day next year (April 15th 2014) for a total lunar eclipse spanning the Americas!

 

Super-Bright Explosion Seen on the Moon

A bright flash on the Moon on March 17, 2013 when a boulder-sized asteroid hit the lunar surface.

If you were looking up at the Moon on March 17, 2013 at 03:50:55 UTC, you might have seen one of the brightest “lunar flashes” ever witnessed. And it would have been visible with just the naked eye.

“On March 17, 2013, an object about the size of a small boulder hit the lunar surface in Mare Imbrium,” says Bill Cooke of NASA’s Meteoroid Environment Office. “It exploded in a flash nearly 10 times as bright as anything we’ve ever seen before.”

The scientists estimate that the flash came from a 40 kg meteoroid measuring 0.3 to 0.4 meters wide hitting the Moon, likely traveling about 90,000 km/hr (56,000 mph.) The resulting explosion packed as much punch as 5 tons of TNT.

(FYI, lunar meteors hit the ground with so much kinetic energy that they don’t require an oxygen atmosphere to create a visible explosion. The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site.)

The crater could be as wide as 20 meters. The scientists for the Lunar Reconnaissance Orbiter are hoping to image the impact site the next time the spacecraft passes over the area. It should be relatively easy to spot, and lunar scientists are always on the lookout for recent impacts. Additionally, comparing the size of the crater to the brightness of the flash would give researchers a valuable “ground truth” measurement to validate lunar impact models.

Were you observing the Moon that night? Universe Today’s David Dickinson pointed out to me that it is quite possible an amateur could have caught it; however no amateur images have surfaced yet. The Moon would’ve been a waxing crescent and visible to the Pacific region and US West Coast at the time. If you have archived images or video, it might be worth a look. And we’d love to hear from you if you happened to catch anything! NASA said the impact site would have glowed like a 4th magnitude star for about one second.

These false-color frames extracted from the original black and white video show the explosion in progress. At its peak, the flash was as bright as a 4th magnitude star. Credit: NASA
These false-color frames extracted from the original black and white video show the explosion in progress. At its peak, the flash was as bright as a 4th magnitude star. Credit: NASA

During the past 8 years, Cooke and a team of NASA astronomers have been monitoring the Moon for signs of explosions caused by meteoroids hitting the lunar surface.

Ron Suggs, an analyst at the Marshall Space Flight Center, was the first to notice the March 17th impact in a digital video recorded by one of the monitoring program’s 14-inch telescopes. “It jumped right out at me, it was so bright,” he said.

During the 8 years of observations, the team has found that the flashes on the Moon are more common than anyone expected, with hundreds of detectable impacts occurring every year.

Since the monitoring program began in 2005, NASA’s lunar impact team has detected more than 300 strikes, most orders of magnitude fainter than the March 17th event. Statistically speaking, more than half of all lunar meteors come from known meteoroid streams such as the Perseids and Leonids. The rest are sporadic meteors–random bits of comet and asteroid debris of unknown parentage.
Cooke believes the lunar impact might have been part of a much larger event.

NASA's lunar monitoring program has detected hundreds of meteoroid impacts. The brightest, detected on March 17, 2013, in Mare Imbrium, is marked by the red square. Credit: NASA
NASA’s lunar monitoring program has detected hundreds of meteoroid impacts. The brightest, detected on March 17, 2013, in Mare Imbrium, is marked by the red square. Credit: NASA

“On the night of March 17, NASA and University of Western Ontario all-sky cameras picked up an unusual number of deep-penetrating meteors right here on Earth,” he said. “These fireballs were traveling along nearly identical orbits between Earth and the asteroid belt.”

This means Earth and the Moon were pelted by meteoroids at about the same time.

“My working hypothesis is that the two events are related, and that this constitutes a short duration cluster of material encountered by the Earth-Moon system,” said Cooke.

One of the goals of the lunar monitoring program is to identify new streams of space debris that pose a potential threat to the Earth-Moon system. The March 17th event seems to be a good candidate.

Source: Science@NASA

An Awesome Annular Eclipse! Images and Videos from Earth and Space

@Beyond_Beneath Geoff Sims Plutonic Gold Mine, Australia

A spectacular annular eclipse of the Sun was witnessed across Australia and the southern Pacific region early today. Morning dawned mostly clear across the Australian continent, and those who journeyed out to meet the antumbra of the Moon as the Sun rose across the Great Sandy Desert and the Cape York Peninsula were not disappointed. The rest of us watched worldwide on as Slooh and a scattering of other ad-hoc broadcasts delivered the celestial event to us via the web.

This was a challenging one. Although partial phases of the eclipse was visible across the entirety of Australia, Hawaii, and as far north as the Philippines and as far south as New Zealand, the track of annularity passed over some very remote locales. Stable Internet connections were scarce, and many photos and videos are still trickling in as die-hard eclipse chasers return “from the Bush.”

One lucky witness to the eclipse was Druce Horton (Xylopia on flickr) who caught the eclipse from Kuranda, Australia just north of Cairns. “It was completely clouded over here in Kuranda and I didn’t even bother going to a place where I could get a clear view.” Druce told Universe Today. “I then noticed the sky lightening a little and I rushed out with the camera and desperately tried to set an appropriate exposure and frame it while avoiding getting an eyeful of sunlight and/or a tree branch in the way.”

As seen by Druce Horton near Kurunda, Australia.
A rising crescent eclipse as seen by Druce Horton near Kurunda, Australia. (Credit and Copyright: Druce Horton. Used with Permission).

As pointed out the us by Michael Zeiler (@EclipseMaps) earlier this week, the town of Newman and surrounding regions in Western Australia were a great place to witness the rising annular eclipse. Geoffrey Sims ventured out and did just that:

eclipse...
The rising annular eclipse. (Credit: Geoff Sims).

Note how the atmospheric haze is distorting the solar annulus into a flattened ring… pure magic! Mr. Sims got some truly stunning pictures of the eclipse, and was one of the first to manage to get them out onto the Internet, though he stated on Twitter that it “will likely take weeks to sort through the images!”

All get reasons to keep a close eye on Mr. Sims’ Facebook page

Mr. Joerg Schoppmeyer also ventured about 70 kilometres south of Newman to catch the rising “Ring of Fire”:

Annularity just moments after internal contact of the antumbra. Credit:
Annularity just moments after internal contact of the antumbra. Credit: Joerg Schoppmeyer).

We also mentioned earlier this week how you can use the “strainer effect” to create a flock of crescent Suns during a partial solar eclipse.

Amanda Bauer (@astropixie) of Sydney, Australia did just this to create her name in “eclipse pacmans”:

eclipse
An Astropixie Eclipse… (Credit: Amanda Bauer).

And speaking of which, eclipse crescents can turn up in the most bizarre of places, such as a lens flare caught by a webcam based at the Canberra Deep Space Network:

Credit: NASA
A lens flare eclipse. (Credit: CDSCC/NASA).

Trevor Sellman (@tsellman) based in northern Melbourne preferred to catch sight of the partial phase of the eclipse “the old fashioned way,” via a simple pinhole projection onto a white sheet of paper:

Pinhole
A pinhole eclipse. (Credit: Trevor Sellman).

In addition to Slooh, the Mead West Vaco Observatory in conjunction with the Columbus State University’s Coca-Cola Space Science Center provided an excellent webcast of the full phases of the eclipse, and in multiple wavelengths to boot:

CCSS
The solar annulus as seen near mid-eclipse in hydrogen alpha. (Credit: the CCSSC).

And they also provided a view in Calcium-K:

Screen cap in Cal-K
A screen capture of the final stage of the eclipse as seen in Cal-K. (Credit: the CCSSC).

But Earth bound-observers weren’t the only ones on hand to witness this eclipse. Roskosmos also released a video animation of the antumba of the Moon crossing the Earth as seen from the Elektro-L satellite:

“These images interest Russian space enthusiasts because we asked  Roskosmos to optimize (the) work of satellite for best pictures of eclipse,” Vitaliy Egorov told Universe Today.

There’s no word as of yet if the NASA/JAXA spacecraft Hinode or if ESA’s Proba-2 caught the eclipse, although they were positioned to take advantage of the opportunity.

There were also some active sunspot regions on the Earthward face of the Sun, as captured by Monty Leventhal in this outstanding white-light filtered image:

Eclipse

Another fine video animation of the eclipse turned up courtesy of Steve Swayne of Maleny in Queensland, Australia;

And finally, Vanessa Hill caught the partial stage of the eclipse while observing from the CSIRO Astrophysics & Space Sciences viewing event:

eclipse
A partially eclipsed Sun. (Credit: @nessyhill).

Partial stages of the eclipse were also captured by Carey Johnson (@TheTelescopeGuy) from Hawaii and can be viewed on his flickr page.

If this eclipse left you jonesin’ for more, there’s a hybrid solar eclipse across the Atlantic and central Africa on November 3rd 2013. Maximum totality for this eclipse is 1 minute and 40 seconds. Unfortunately, after two solar eclipses in 6 months, another total solar eclipse doesn’t grace the Australian continent until July 22nd, 2028!

But such are the ways of the cosmos and celestial mechanics… hey, be glad we occupy a position in space and time where solar eclipses can occur.

Thanks to all who sent in photos… if you’ve got a picture of today’s eclipse, an anecdote, or just a tale of triumph and/or eclipse chasing tribulations drop us a line & share those pics up to the Universe Today flickr group. See you next syzygy, and may all your eclipse paths be clear!

 

 

Buzz Aldrin is on a Mission (to Mars), Part 1

Moonwalker and space visionary, Buzz Aldrin. Credit: National Geographic.

Buzz Aldrin, celebrated Apollo astronaut and an outspoken champion for the pursuit of space exploration has written a new book titled “Mission to Mars.” While the title focuses on Mars, the book covers much more. Aldrin says that while Mars is the destination, getting there is a journey that includes taking advantage of the efforts from commercial space companies, embracing space tourism, working towards planetary defense, developing technology, promoting STEM (science, technology, engineering and mathematics) education, and working together with international partners. What Aldrin calls his “unified vision” could provide a timeline of crewed missions to Mars is between 2035-2040.

“His point is trying to unify all of this,” said noted journalist and long-time Space.com writer Leonard David in an email to Universe Today. David is a co-author with Aldrin on this new book. “I hope the book is a good platform for moving the space exploration agenda forward.”

“Mission to Mars” is written from Aldrin’s perspective, and Aldrin and David spend little time looking back at the past achievements of Gemini and Apollo, and instead look forward of how the next steps in space exploration should be taken.

Universe Today had the chance to talk with Buzz Aldrin about his book and his plan. Following is part 1 of our interview:

Mission_to_Mars_CoverFINAL
Universe Today: Mr. Aldrin, it is an honor to talk with you – and congratulations on publishing another book. We really enjoyed getting the chance to read it and get your perspective on the future of space exploration.

Buzz Aldrin: Thank you very much. As far as the title, I really wanted to change the title to add an “s” to mission, as after thinking about it, it is the same title as Mike Collins’ book he wrote after we came back from the Moon, and it’s also the title of a not-so-successful movie! In this book, we also talk about much more than just one mission to Mars. We want many missions there, with a future-focused space exploration program.

Find out how to win a copy of Mission to Mars (contest open to US residents only)

Universe Today: Ever since you walked on the Moon, I think that Mars has been the ultimate destination that we’ve all dreamed about, and back in 1969, I think many people thought that by 2013, we certainly would have humans on Mars by this time. What do you think has been the biggest reason or roadblock that we’ve yet to achieve that goal?

Buzz Aldrin: There are probably a number of reasons. With Apollo, once having achieved the goal in a relatively intense parade of achievements, leading up to the crescendo of landing on the Moon six out of seven times, then it all ended. The events in the future are going to require much longer commitments to a pathway and a unified vision of what we should be doing and where we should go in space. I have always felt Mars should be the next destination following our landings on the Moon, but a unified vision is what we need to be able to increase the probability of being successful.

We are in a world that focuses on short term returns, and the politics these days is controlled by the desire to have an extraordinary portion of influence and control over the direction of the space program. That is probably one of the most important reasons for my embarking on a creating a foundation for the evolution of space policy, using what we’ve learned from the past to redirect some of our policies in the future for two things: the expansion of humans outward into the solar system and specifically for the US, global leadership in space as long as possible.

UT: You’ve long proposed the cycling system of having spacecraft almost on a railroad or bus lines of going regularly back and forth to Mars. Can you explain for our readers why this is the most efficient way of getting supplies and people to Mars?

Buzz Aldrin: When a spacecraft departs Earth, the main portion of it is rarely ever re-used. This one spacecraft contributes its one mission, as we did with the Apollo spacecraft. Now, if we can depart a spacecraft from the Earth that can carry some of the mass, in particular the radiation protection and other supplies for a brief 5-6 month trajectory of swinging past Mars, we can reduce costs.

Years ago I devised a method with cycling orbits of spacecraft on continuous trajectories between the Earth and Mars – a spacecraft going to Mars and then returning back to Earth at just the right time, angle and velocity to be able to repeat the process 26 months later when Earth, again, is in a favorable position. By using interplanetary cyclers, I feel, and other space experts agree with me, this is the most economical transportation system concept between the Earth and Mars.

When I first discovered this, it was studied and understood by the 1986 Paine Commission, a group who looked at pioneering space, led by the administrator of NASA who had directed us in our lunar landings, Tom Paine. This was, I think, one of the best and most complete studies ever really done.

Timetable of events proposed by Buzz Aldrin's Unified Space Vision. Via BuzzAldrin.com
Timetable of events proposed by Buzz Aldrin’s Unified Space Vision. Via BuzzAldrin.com

But since this Commission’s reference to cycling spacecraft, NASA officials and space companies have paid little attention to the advantages of cycling orbits — with the exception of the University of Purdue, which works with engineers at JPL and Caltech — and together with my pioneering ideas, we have discovered that if there are two cycling spacecraft, it gives us a bigger advantage and reduction in the fuel needed. In each cycle, the Cycler’s trajectory swings it by the Earth, and a smaller Earth-departing interceptor spacecraft ferries crew and cargo up to dock with the Cycler spacecraft, and likewise at Mars to reach the surface. So we’ve improved the cycling orbit potential. We now need to test the long-duration equipment that will be needed. Ultimately, this Cycler system of transportation offers a way to make travel to Mars sustainable for the long-term.

For the spacecraft, what I’ve done is taken my concept, which is based on some of NASA’s work of an interplanetary vehicle and put of them together side by side for redundancy, and perhaps adding a few other necessary elements, to become the Cycling spaceship. I also propose building a permanent base on the surface of Mars by actually landing on the moon of Mars Phobos, and building it tele-robotically from there, with various objects such as inflatable habitats, to be assembled into a Mars base. These missions should be international in nature.

All of this is very complex and we need to learn how to build up to it. But one of the most attractive ways would be, before finalizing the Mars base, we could execute an international lunar base. This could be based upon US leadership of what could be an international lunar development authority — much like Intelsat was developed for international satellite communications in geosynchronous orbit. We also have the International Space Station to do some of the initial testing of equipment, such as long duration life support systems.

Not only does NASA need this long-duration life support but also the recently announced Inspiration Mars Mission, which would send a married couple in January 2018 on a flyby of Mars. This would do much to stimulate the planning and testing of the progressive development of the interplanetary space capabilities.

Before we execute an international partner mission back to the Moon, we can test that assembly process on the Big Island of Hawaii where people have been working to select a site similar to where we might have a lunar base built and there we could practice building a base tele-robotically. Once on the Moon, we could develop lunar infrastructure, and allow for robotic mining that could be done for commercial development.

We’ll need cooperative activities between the government, NASA, other government agencies and the commercial companies executing their activities designed to evolve into profit-making businesses.

UT: You mention in your book that a space race with China would be counterproductive. Do you think there’s a way to work with them and have it be productive and beneficial beyond space exploration?

Buzz Aldrin: Right now, unfortunately, Congress forbids NASA personnel to even talk with China. The great opportunity of bringing China into the ISS, is that we could still do this during the lifetime of the space station. China is developing its own its space station, but there doesn’t seem to be an openness between our two countries to work on the big picture of space exploration. Everyone is out for their own return. But there could be a wonderful opportunity here for the US to exercise global leadership in space activities.

Tomorrow: Part 2 of our interview with Buzz Aldrin, where he discusses his thoughts on NASA’s asteroid-lassoing plans, space elevators, and future commercial mission.

How to Catch This Week’s ‘Ring of Fire’ Annular Eclipse

A perfect ring of fire captured by Kevin Baird on May 20th, 2012 from Bluit New Mexico. (Credit: Kevin Baird/Universe Today flickr Group).

The first solar eclipse of 2013 is upon us this week, with the May 10th annular eclipse crossing northern Australia and the Pacific.

2013 is an off year for eclipses. There are five eclipses this year, three lunars and two solars. Last month’s very shallow partial lunar eclipse set us up for the annular that occurs this week. In fact, the theoretical mid-point for the first of two eclipse seasons for 2013 occurs on May 7th at 7:00 UT/ 3:00 EDT when the longitude of the Sun equals the descending node where the Moon’s path crosses the ecliptic. This further sets us up for the third and weakest eclipse of the year, a grazing penumbral on May 25th.

Animation of the path of this week's annular solar eclipse. (Credit: NASA/GSFC/A.T. Sinclair).
Animation of the path of this week’s annular solar eclipse. (Credit: NASA/GSFC/A.T. Sinclair).

An annular eclipse occurs when the Moon eclipses the Sun while near apogee and is hence visually too small to entirely cover the Sun.

The Moon reaches apogee on May 13th at 13:32 UT/9:32AM EDT at 405,826 kilometres from Earth, just 3 days and 13 hours past New.

Annulars are currently more common than total solar eclipses, occurring 33.2% of the time in our current 5,000 year epoch versus 26.7% for total solar eclipses. The remainders are hybrid and partial eclipses. Annulars will become even more common as our Moon recedes from us at a current rate of about 3.8 centimetres a year. In about 1.4 billion years, the final brief total solar eclipse as seen from the Earth will occur. Likewise, somewhere back about 900 million years ago, the very first annular eclipse as seen from the Earth occurred.

Solar viewing with a properly  fitted glass white light filter over the aperture of a Schmidt-Cassegrain telescope. (Photo by Author).
Solar viewing with a properly fitted glass white light filter over the aperture of a Schmidt-Cassegrain telescope. (Photo by Author).

Safety is paramount while viewing an annular solar eclipse. As mentioned above, an annular eclipse throughout all phases is much brighter than you’d expect. Thus precautions to protect your eyes MUST be taken throughout ALL phases of the eclipse. Permanent eye damage can result from staring at the Sun without proper protection, and this can be near instantaneous when done through an unfiltered telescope!

We witnessed the 1994 annular eclipse from the shores of Lake Erie, and can tell you that 5% of the Sun is still extremely bright. You wouldn’t even know an annular eclipse was underway at midday unless you were looking for it. Use only filters approved for eclipse viewing that fit snugly over the FRONT of your optics. Throw those old eyepiece screw-on filters away, as they can heat up and crack!

Check filters before use and never leave a telescope aimed at the Sun unattended. Projecting the Sun is another option via a telescope or “Sun Gun,” but again, never leave such a rig unattended, and keep finderscopes covered at all times. Also, telescopes with folded optical paths such as Schmidt-Cassegrains can heat up to dangerous levels and should not be used for projecting the Sun.

The path of the May 9th/10th annular eclipse across Australia & the Pacific. (Map courtesy of Michael Zeiler at Eclipse Maps, click to enlarge).
The path of the May 9th/10th annular eclipse across Australia & the Pacific. (Map courtesy of Michael Zeiler at Eclipse Maps, click to enlarge).

This eclipse has a magnitude rating of 0.9544, meaning that 95.44% of the diameter of the Sun will be eclipsed at its maximum. Keep in mind, this leaves about 8.9% percent of the Sun, or about 1/11th of its visual area exposed. This translates to only a 2.5 magnitude drop in brightness. Thus, the brightness of the Sun will drop from magnitude -27 to -24.5, still well over 25,000 times brighter than the Full Moon!

Note that this one crosses the International dateline as well.

The action for this eclipse begins as the partial phases touch down over Western Australia at sunrise at 21:25 UT on May 9th (The morning of May 10th in Australia). The annulus makes its appearance at 22:30 UT over western Australia, with its 172 kilometre wide track racing to the northeast over Tennant Creek in the Northern Territories and crossing the Cape York peninsula as it crisscrosses the path of last November’s total solar eclipse just north of Cairns.

A closeup of the path of the annular eclipse across Australia, click to enlarge. (Courtesy of Miichael Zeiler at Eclipse Maps).
A closeup of the path of the annular eclipse across Australia, click to enlarge. (Courtesy of Miichael Zeiler at Eclipse Maps).

Note that the eclipse will be 80% partial near Alice Springs and Uluru (Ayers Rock), presenting an excellent photo op. Michael Zeiler at Eclipse Maps also points out that the area near the town of Newman in Western Australia will see an amazing sunrise annular eclipse. The path of the annular eclipse will then traverse the Coral Sea crossing over islands in eastern Papua New Guiana, the Solomon Islands and Kiribati before reaching greatest annularity with a duration of 6 minutes and 3 seconds at latitude 2° 13’ north and longitude 175° 28’ east. The path of annularity crosses over Bairiki Atoll and makes last landfall over Fanning Island north of Kiribati. Note that most of Australia, New Zealand, Indonesia and the Philippines will see partial phases of the eclipse. The islands of Hawaii across the dateline will also see a 40-50% partial eclipse on May 9th before the event ends in the eastern Pacific at 03:25:23 UT.

Weather prospects for the eclipse look to be best along the track through Australia with less than 20% chance of cloud cover then getting progressively worse as the eclipse path tracks northeastward out to sea. The Solomon Islands region can expect cloud cover in the 60% range, while in Hawaii prospects are about 70%. Eclipser maintains a site dedicated to weather prospects for upcoming eclipses.

Solar activity is currently moderate, with several sunspot groups currently turned Earthward making for a photogenic Sun on eclipse day;

Sunspot activity as of May 5th. (Photo by Author).
Sunspot activity as of May 5th. (Photo by Author).

This eclipse belongs to saros series 138 and is number 31 of 70. This saros started with a 2% partial solar eclipse on June 6th, 1472 and will end with a 12% partial on July 11th,2716 AD having produced 3 total, 1 hybrid, 16 partial and 50 annular eclipses.

Fans of this saros may remember the last annular in this series which crossed South America on April 29th, 1995.

A sequence of eclipse pictures taken from Huntington Beach, California on May 20th, 2012. (Credit: jimnista/Universe Today flickr gallery).
A sequence of eclipse pictures taken from Huntington Beach, California on May 20th, 2012. (Credit: jimnista/Universe Today flickr gallery).

Catching a rising annular eclipse can also make for a stunning photograph. To catch the eclipse and the foreground horizon in silhouette, a DSLR with a 400mm lens running at 1/500th of a second shutter speed or faster is a good combination. Remember, you’ll have to aim this via projection. DO NOT look through the camera at the Sun! Exposures slower than 1/200th of a second are also out of the question, as you can damage the camera sensor at slow exposures.

Another cool effect to watch for is the appearance of tiny little “crescent Suns” littering the ground as sunlight streams through gaps in the tree leaves. This occurs because the gaps act like tiny little pinhole cameras.  A spaghetti strainer is also a highly scientific apparatus that can be used to mimic this effect!

Several solar observing satellites, including Hinode and the European Space Agency’s Proba-2 are poised to catch multiple partial solar eclipses on May 9th and 10th. We ran simulations of these this weekend:

Finally, if you’re like 99.99% of humanity, you’ll be watching this eclipse online. Slooh will be broadcasting this eclipse live.

Also, the eclipse will be broadcast live via the Coca-Cola Space Science Center starting at 5PM ET.

Amateur astronomer Geoff Sims @beyond_beneath will be tweeting near real time images of the eclipse from the path of annularity. Colin Legg (@colinleggphoto) will also be observing the event. Also check out:

-Australian observer Gerard Lazarus’s live feed of the eclipse.

3News in New Zealand and Sky News Australia for eclipse coverage.

Got an ad hoc eclipse broadcast planned? Let us know and we’ll include it!

The next and final solar eclipse for 2013 is a hybrid (annular along one section of the path and total along another) on November 3rd across the mid-Atlantic and central Africa. Another annular eclipse doesn’t occur until April 29th 2014, and the next total solar eclipse occurs on March 20th, 2015.

If you’re in the region be sure to catch this rare celestial event in person, or watch the action worldwide online!

 

Into Oblivion: What If the Earth Had No Moon?

A shattered Luna as depicted in the summer blockbuster Oblivion. (Credit: Universal Pictures).

AVAST gentle reader: mild SPOILER(S) and graphic depictions of shattered satellites ahead!

We recently had a chance to catch Oblivion, the first summer blockbuster of the season. The flick delivers on the fast-paced Sci-Fi action as Tom Cruise saves the planet from an invasion of Tom Cruise clones.

But the movie does pose an interesting astronomical question: what if the Earth had no large moon? In the movie, aliens destroy the Earth’s moon, presumably to throw our planet into chaos. You’d think we’d already be outclassed by the very definition of a species that could accomplish such a feat, but there you go.

Would the elimination of the Moon throw our planet into immediate chaos as depicted in the film? What if we never had a large moon in the first place? And what has our nearest natural neighbor in space done for us lately, anyway?

Earth is unique among rocky or terrestrial planets in that it has a relatively large moon. The Moon ranks 5th in diameter to other solar system satellites. It is 27% the diameter of our planet, but only just a little over 1/80th in terms of mass.

Clearly, the Moon has played a role in the evolution of life on Earth, although how necessary it was isn’t entirely clear. Periodic flooding via tides would have provided an initial impetus to natural selection, driving life to colonize the land. Many creatures such as sea turtles take advantage of the Full Moon as a signal to nest and breed, although life is certainly resilient enough to find alternative methods.

The 2000 book Rare Earth by Peter Ward and Donald Brownlee cites the presence of a large moon as just one of the key ingredients necessary in the story of the evolution of life on Earth. A Moon-less Earth is also just one of the alternative astronomical scenarios cited by Arthur Upgreen in his 2005 book Many Skies.

Save our satellite: A possible target for an alien attack? (Photo by author).
Save our satellite: A possible target for an alien attack? (Photo by author).

Contrary to its depiction on film, the loss of the Moon wouldn’t throw the Earth into immediate chaos, though the long term changes could be catastrophic. For example, no study has ever conclusively linked the Moon to the effective prediction of terrestrial volcanism and earthquakes, though many have tried. (Yes, we know about the 2003 Taiwanese study, which found a VERY weak statistical signal).

All of that angular momentum in the Earth-Moon system would still have to go somewhere. Our Moon is slowly “braking” the rotation of the Earth to the tune of about 1 second roughly every 67,000 years. We also know via bouncing laser beams off of retro-reflectors left by Apollo astronauts that the Moon is receding from us by about 3.8 cm a year. The fragments of the Moon would still retain its angular momentum, even partially shattered state as depicted in the film.

The most familiar effect the Moon has on Earth is its influence on oceanic tides. With the loss of our Moon, the Sun would become the dominant factor in producing tides, albeit a much weaker one.

But the biggest role the Moon plays is in the stabilization of the Earth’s spin axis over long scale periods of time.

Milankovitch cycles play a long term role in fluctuations in climate on the Earth. This is the result of changes in the eccentricity, obliquity and precession of the Earth’s axis and orbit. For example, perihelion, or our closest point to the Sun, currently falls in January in the middle of the northern hemisphere winter in the current epoch. The tilt of the Earth’s axis is the biggest driver of the seasons, and this varies from 22.1° to 24.5° and back (this is known as the change in obliquity) over a span of 41,000 years. We’re currently at a value of 23.4° and decreasing.

But without a large moon to dampen the change in obliquity, much wider and unpredictable swings would occur. For example, the rotational axis of Mars has varied over a span of 13 to 40 degrees over the last 10 to 20 million years. This long-term stability is a prime benefit that we enjoy in having a large moon .

Perhaps some astronomers would even welcome an alien invasion fleet intent on destroying the Moon. Its light polluting influence makes most deep sky imagers pack it in and visit the family on the week surrounding the Full Moon.

But I have but two words in defense of saving our natural satellite: No eclipses.

The diamond ring effect as seen during a 2008 total solar eclipse. (Credit: NASA/Exploratorium).
The diamond ring effect as seen during a 2008 total solar eclipse. (Credit: NASA/Exploratorium).

We currently occupy an envious position in time and space where total solar and lunar eclipses can occur.  In fact, Earth is currently the only planet in our solar system from which you can see the Moon snugly fit in front of the Sun during a total lunar eclipse. It’s 1/400th the size of the Sun, which is also very close to 400 times as distant as the Moon. This situation is almost certainly a rarity in our galaxy; perhaps if alien invaders did show up, we could win ‘em over not by sending a nuclear-armed Tom Cruise after ‘em, but selling them on eclipse tours… Continue reading “Into Oblivion: What If the Earth Had No Moon?”

Astrophotographers Capture “Mini” Lunar Eclipse

The brief partial lunar eclipse on Ari 25, 2013 captured over Israel. Credit and copyright: Gadi Eidelheit.

The lunar eclipse on April 25 was described by astrophotographer Gadi Eidelheit as “the greatest, slightest eclipse I ever saw!” The brief and small eclipse saw just 1.47% of the lunar limb nicked by the dark umbra or shadow from the Earth. It was visible from eastern Europe and Africa across the Middle East eastward to southeast Asia and western Australia. Here are a few more shots, including a serendipitous shot of an airplane flying through the eclipse!

Airliner flies through partial eclipse! On April 25, 2013, around 10:10 PM local time, the partial Lunar eclipse was at its maximum. The Moon only traveled 1,3% into the central Earth shadow (umbra). The event was visible from Europe, Asia and Australia. Canon EOS 600D on 130 mm (f/7,1) triplet Apo-refractor settings: 1/200 exposure at ISO 100.  Credit and copyright:  Philip Corneille – FRAS (Belgium).
Airliner flies through partial eclipse! On April 25, 2013, around 10:10 PM local time, the partial Lunar eclipse was at its maximum. The Moon only traveled 1,3% into the central Earth shadow (umbra). The event was visible from Europe, Asia and Australia. Canon EOS 600D on 130 mm (f/7,1) triplet Apo-refractor settings: 1/200 exposure at ISO 100. Credit and copyright: Philip Corneille – FRAS (Belgium).
The small, shallow eclipse on April 25, 2013. Credit and copyright: Andrei Juravle.
The small, shallow eclipse on April 25, 2013. Credit and copyright: Andrei Juravle.
Partially eclipsed Moon rising over Brixton in the UK on April 25, 2013. Credit and copyright: Owen Llewellyn.
Partially eclipsed Moon rising over Brixton in the UK on April 25, 2013. Credit and copyright: Owen Llewellyn.
Eclipsed Moon on April 25, 2013 over the UK. Credit and copyright: Sculptor Lil on Flickr.
Eclipsed Moon on April 25, 2013 over the UK. Credit and copyright: Sculptor Lil on Flickr.
The eclipsed Moon, with Saturn showing as a bright point of light on the left, as seen over Königswinter, Germany. Credit and copyright: Daniel Fischer.
The eclipsed Moon, with Saturn showing as a bright point of light on the left, as seen over Königswinter, Germany. Credit and copyright: Daniel Fischer.
The mini lunar eclipse on April 25, 2013 as seen from Bruges, Belgium. Credit and copyright: Cochuyt Joeri.
The mini lunar eclipse on April 25, 2013 as seen from Bruges, Belgium. Credit and copyright: Cochuyt Joeri.
A 'before' and 'during' comparison picture of the partial lunar eclipse on the 25th of April 2013. The photo on the left ('before') was taken at about 20h00 CAT and the photo on the right ('during') was taken around 22h06 CAT. Credit and copyright: Hein Oosthuyzen, Johannesburg, South Africa.
A ‘before’ and ‘during’ comparison picture of the partial lunar eclipse on the 25th of April 2013. The photo on the left (‘before’) was taken at about 20h00 CAT and the photo on the right (‘during’) was taken around 22h06 CAT. Credit and copyright: Hein Oosthuyzen, Johannesburg, South Africa.
Partial Lunar Eclipse on April 25, 2013. Credit and copyright: Henna Khan.
Partial Lunar Eclipse on April 25, 2013. Credit and copyright: Henna Khan.

Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.

Why Spacewalking Is All About The Hands

NASA astronaut Shane Kimbrough works outside the International Space Station in 2008. Credit: NASA

Think about your typical construction worker — there’s a lot of reaching, bending, stretching, lifting. How do you accomplish those tasks without gravity, as astronauts do on the International Space Station?

According to astronaut Shane Kimbrough — who should know, as he spent more than 12 hours “outside” doing station work and repairs during shuttle mission STS-126 in 2008 — instead of using your feet, you transfer most of the work to your hands. Your feet are basically used to brace yourself.

“You’re moving around, kind of walking with your hands, and pulling yourself in between the handholds and the rails,” he said to Universe Today, expanding on comments he made publicly at a conference last week.

Astronauts train for hours in a large pool known as the Neutral Buoyancy Laboratory, which includes a full-size model of the station modules inside. “You build up the [hand] strength in the NBL,” Kimbrough said, “with your hands fighting against the pressure of the spacesuit. If you didn’t do that, your hands would be fatigued [during a spacewalk.]”

It’s not a perfect training environment, though. “The big difference in the water is the drag it produces. You don’t realize you are floating, at times. If you’re moving along and walking with your hands down the rail, and you stop, you will immediately stop. In space, the mass of your spacesuit keeps going even if you stop. Your body will keep moving back and forth a few times, and using more energy when you need.”

Shane Kimbrough spent more than 12 hours outside the International Space Station during one mission. Credit: NASA
Shane Kimbrough spent more than 12 hours outside the International Space Station during one mission. Credit: NASA

During the shuttle era, astronauts tended to specialize in different areas of spaceflight — robotics and extra-vehicular activity (spacewalks) being some of the fields. The station, however, demands that astronauts be versed in both, Kimbrough said. Any crew could be called upon to do a repair on short notice, or to haul in a robotic spacecraft (like SpaceX’s Dragon) that arrives at station.

This means there’s a huge demand within NASA now for spacewalking expertise. Before stepping into the NBL, the astronauts run through the procedures in the classroom, and will get a look at the tools to make sure they understand their functions. Occasionally, a crew might pop on scuba suits to do a rough run of an expected spacewalk at the station, rehearsing where they should be and how they should position themselves.

A spacesuit really limits the astronaut’s range of motion, making the hours of training crucial. “For people like myself, with short arms, our work envelope is very small,” said Kimbrough, who is hoping for another flight assignment.

“It’s really out in front, not very far, in a circular motion. If you put your hand out in front, a small circle, that’s my work envelope. If I want to get something higher or lower, I can’t get there by reaching based on the way the [spacesuit] shoulder and arm operates. You maybe have to go sideways or upside down.”

November 3, 2007 – Canadarm2 played a big role in helping astronauts fix a torn solar array.  The arm’s reach was extended by the Orbiter Boom Sensor System, and here, allowing astronaut Scott Parazynski analyses the solar panel while anchored to the boom. Credit: NASA
November 3, 2007 – Canadarm2 played a big role in helping astronauts fix a torn solar array. The arm’s reach was extended by the Orbiter Boom Sensor System, and here, allowing astronaut Scott Parazynski analyses the solar panel while anchored to the boom. Credit: NASA

Spacewalking is inherently a dangerous business. Many people remember a daring station-era spacewalk in 2007, when Scott Parazynski dangled on the end of a Canadarm2 extension to stitch together a torn — and live — solar array. For this spacewalk, a lot of procedures were put together on the fly.

NASA also has a computer program that can roughly simulate how the astronauts can get into various areas of the station, and this was extensively used before Parazynski’s spacewalk, Kimbrough said.

Kimbrough’s crew had a more messy problem as they worked to repair the broken solar array rotary joint (that controlled one of the station’s solar panel arrays) and do other station work. The grease guns the crew used in that mission periodically squirted way too much grease and covered everything. The work area, the spacesuits, the tools.

“It had to do with the thermal properties,” Kimbrough said. “It would go in between pretty hard, to not being so hard. So sometimes, the grease guns that were designed at the time leaked … they have been redesigned, a few modifications, and they’ve worked well since then.”

Kimbrough himself ran into a minor, but still surprising situation when at the end of a lengthy tether. It turned out that tether had a bit of zing to it. “I was working way out on the end of the truss, and it was nighttime and I felt somebody pulling me back and almost spinning me around. The force of it surprised me the most.”

Other astronauts had warned him about that ahead of time, Kimbrough said, but he didn’t realize how vehement the pull could be. “I was a believer after that,” he joked.

A ‘Shallow’ Lunar Eclipse Coming on April 25

The very early partial phase of the 2010 December solstice total lunar eclipse. This week's shallow eclipse will appear similar at its maximum. (Photo by author)

Eclipse season is upon us this week with the first eclipse of 2013, a brief partial lunar eclipse.

The lunar eclipse on April 25, 2013 is a shallow one, meaning only a paltry 1.47% of the lunar limb will be immersed in the dark umbra or inner shadow of the Earth. Observers can expect to see only a dark diffuse edge of the inner shadow nick the the Moon as is grazes the umbra.

A partial lunar eclipse this shallow hasn’t occurred since May 3rd, 1958 (0.9%) and won’t be topped until September 28th, 2034 (1.4%). This is the second slightest partial lunar eclipse for this century.

Another term for this sort of alignment is known as a syzygy, a great triple-letter word score in Scrabble!

A video simulation of the eclipse:

The eclipse will be visible in its entirety from eastern Europe & Africa across the Middle East eastward to southeast Asia and western Australia. The eclipse will be visible at moonrise from South America to Western Europe and occurring at moonset for eastern Australia and the Far East. The partially eclipsed Moon will be directly overhead just off the northeastern coast of Madagascar. The eclipse will not be visible from North America.

Two eclipse seasons occur each year when the nodal points of the Moon’s orbit intersect the ecliptic while aligned with the position of the Sun and the Earth’s shadow. The Moon’s orbit is inclined 5.15° degrees with respect to the ecliptic, which traces out our own planet’s path around the Sun. If this intersection occurs near New or Full Moon, a solar or lunar eclipse occurs.

The visibility region of Thursday's partial lunar eclipse.
The visibility region of Thursday’s partial lunar eclipse (Credit: NASA/GSFC/F. Espenak).

If the Moon’s orbit was not inclined to our own, we’d get two eclipses per lunation, one solar and one lunar.

2013 has 5 eclipses, 3 lunar and 2 annular. The minimum number of eclipses that can occur in a calendar year is 4, and the maximum is 7, as will next occur in 2038.

The 3 lunar eclipses in 2013 are this week’s partial eclipse on April 25th and two faint penumbral eclipses, one on May 25th and another on October 18th. There is no total lunar eclipse in 2013. The last one occurred on December 10th 2011, and the next one won’t occur until April 15th 2014, favoring the Pacific Rim region.

This eclipse will also set us up for the first solar eclipse of 2013, an annular eclipse crossing NE Australia (in fact crossing the path of last year’s total eclipse near Cairns) and the south Pacific on May 10th. The only solar totality that will touch the surface of the Earth in 2013 is  the hybrid eclipse on November 3rd spanning Africa and the South Atlantic with a maximum totality of 1 minute & 40 seconds.

Contact times for the April 25 shallow eclipse:

P1-The Moon touches the penumbra-18:03:41 UT

U1-The Moon touches the umbra-19:54:04 UT

Mid-Eclipse-20:08:37.5 UT

U4 -The Moon quits the umbra-20:21:04 UT

P4-The Moon quits the penumbra- 22:11:23 UT

The length of the partial phase of the eclipse is exactly 27 minutes, and the length of the entire eclipse is 4 hours, 7 minutes and 42 seconds.

This particular eclipse is part of saros series 112 and is member 65 of 72.

This saros cycle began in 859 C.E. on May 20th and will end in 2139 on July 12th with a penumbral lunar eclipse. One famous member of this series was 52.  This eclipse was one of many used by Captain James Cook to fix his longitude at sea on December 4th 1778. Christopher Columbus also attempted this feat while voyaging to the New World. It’s a fun project that anyone can try!

I also remember watching the last eclipse in this series from South Korea on April 15th 1995, a slightly better partial of 11.14%.

An occultation of the bright star Spica occurs just 20 hours prior as seen from South Africa across the southern Atlantic. This the 5th in a series of 13 occultations of the star by the Moon in 2013.

Occultation of Spica
The visibility region for the April 25th occultation of Spica. (Created by the Author using Occult 4.1.0.2).

The +2.8th magnitude star Zubenelgenubi (Alpha Librae) is occulted by the waning gibbous Moon just 15 hours after the eclipse for Australia and the South Pacific.

Another occultation of a bright star with potential this week is +4.7th magnitude Chi Virginis across North America on the morning of Wednesday, April 24th  centered on 4:24 UT.

Chi Virginis occultation
Visibility region for the occultation of Chi Virginis on April 24th. (Created by the author using Occult 4.1.0.2 software).

Also keep an eye out for +0.1 magnitude Saturn near the Full Moon. Saturn reaches opposition this weekend for 2013 on April 28th

Full Moon occurs near mid-eclipse at 20:00 UT/16:00 EDT on April 25th. Colloquial names for the April Full Moon are the Pink, Fish, Sprouting Grass, Egg, Seed, & Waking Moon.

Sure, the penumbral phases of an eclipse are subtle and may not be noticeable to the naked eye… but it is possible to see the difference photographically.  Simply take a photo of the Moon before it enters the Earth’s penumbra, then take one during the penumbral phase and then another one after.  Be sure to keep the ISO/f-stop and shutter speed exactly the same throughout. Also, this project only works if the eclipsed Moon is high in the sky throughout the exposures, as the thick air low to the horizon will discolor the Moon as well. Compare the shots; do you see a difference?

A penumbral eclipse would offer a good proof of concept test for hunting for transiting exoplanets as well, although to our knowledge, no one has ever attempted this.

Finally, calling out to all Universe Today readers in Madagascar. YOU may just be able to catch a transit  of the International Space Station in front of the Moon just as the ragged edge of the umbra becomes apparent on the limb of the Moon. Check CALSky a day or so prior to the eclipse for a refined path… it would be an unforgettable pic!

The position of the ISS on April 25th at 19:48UT, just minutes before the partial pahse of the eclipse begins. (Credit: Orbitron).
The position of the ISS on April 25th at 19:48UT, just minutes before the partial phase of the eclipse begins. (Credit: Orbitron).

And if any ambitious observer is planning to live stream the eclipse, let us know and we’ll add your embed to this post. We do not expect an avalanche of web broadcasts, but hey, we’d definitely honor the effort!  Slooh is usually a pretty dependable site for live eclipse broadcasts, and as of this writing seems to have broadcast scheduled in the cue.

Happy eclipse-spotting!