Observing Alert: Watch the Moon Cross the Hyades This Week

(Credit Tavi)

A photogenic grouping greets evening sky watchers this week providing a fine teaser leading up to a spectacular eclipse.

On the evening of Thursday, April 3rd headed into the morning of the 4th, the waxing crescent Moon crosses in front of the Hyades open star cluster.  This is the V-shaped asterism that marks the head on Taurus the Bull, highlighted by the brilliant foreground star Aldebaran as the bull’s “eye”.  Viewers across North America will have a ring-side seat to this “bull-fight” as the 20% illuminated Moon stampedes over several members of the Hyades in its path.

Starry Night
The passage of the Moon through the Hyades over a three hour span on the night of April 3rd (April 4th in Universal Time) comparing the North American locales of Tampa, Florida and Seattle, Washington. (Credit: Starry Night Education Software).

The brightest stars to be occulted are the Delta Tauri trio of stars ranging in magnitudes from +3.8 (Delta Tauri^1) to +4.8(2) and +4.3(3). Such occlusions – known in astronomy as occultations – are fun to watch, and can reveal the existence of close binary companions as they wink out behind the lunar limb. Several dozen occultations of stars brighter than +5th magnitude by the Moon happen each year, and the best events occur when the Moon is waxing and the stars disappear against its dark leading edge. We recently caught one such event last month when the Moon occulted the bright star Lambda Geminorum:

We are currently seeing the Moon cross the Hyades during every lunation until the year 2020, though it’s a particularly favorable time to catch the event in April 2014 as the Moon is a slender crescent. Notice that you can just make out the dark limb of the Moon with the naked eye? What you’re seeing is termed Earthshine, and that’s just what it is: the nighttime side of the Moon being illuminated by sunlight that is reflected off of the Earth. Standing on the Earthward side of the Moon, an observer would see a waning gibbous Earth about two degrees across. Yutu has a great view!

Credit Occult 4.0
The occultation footprint for Delta Tauri^1. Credit: Occult 4.0

The Moon will cross its descending node where its apparent path intersects the ecliptic on April 1st (no joke, we swear) at 2:30 Universal Time or 10:30 PM EDT on March 31st. The next nodal crossing now occurs in just two weeks, and the Earth’s shadow will be there to greet the Moon on the morning of April 15th in the first of four total lunar eclipses that span 2014 and 2015. The month of April also sees the Moon’s orbit at its least eccentric, a time at which perigee – the Moon’s closest point to Earth – is at its most distant and apogee – its farthest point – is at its closest. This currently happens near the equinoxes, through the nodes slowly travel across the ecliptic completing one revolution every 18.6 years. Perigee can vary from 356,400 to 370,400 kilometres, and apogee can span a distance from 404,000 to 406,700 kilometres.

Stellarium
Looking west from the US SE at about 10PM local on the evening of April 3rd. Credit: Stellarium.

We’re also headed towards a “shallow year” in 2015 when the Moon has the least variability in respect to its declination. This trend will then reverse, climaxing with a “Long Nights Moon” riding high in the sky in 2025, which last occurred in 2006. The Moon will inch ever closer to Aldebaran on every successive lunation now, and begins a series of occultations of Aldebaran on January 29th, 2015 through the end of 2018. Occultations of Aldebaran always occur near these shallow years, and will be followed by a cycle of occultations of Regulus starting in 2017. We caught an excellent daytime occultation of Aldebaran by the Moon from North Pole, Alaska during the last cycle in the late 1990s.

Photos by Author
The Moon passing between the Hyades and Pleiades in 2011 with Earthshine highlighted. Photos by author.

Now for the wow factor. Our Moon is 3,474 kilometres across and located just over one light second away. The Hyades star cluster covers about 6 ½ degrees of sky – about 7 times the size of the Full Moon – but is the closest open cluster to the Earth at 153 light years distant and has a core diameter of about 18 light years across. As mentioned previous, Aldebaran isn’t physically associated with the Hyades, but is merely located in the same direction at 65 light years distant.

The Hyades star cluster also provided early 20th astronomers with an excellent study in galactic motion. At an estimated 625 million years in age, the Hyades are slowly getting disbanded and strewn about the Milky Way galaxy in a process known as evaporation. The Hyades are also part of a larger stellar incorporation known as the Taurus Moving Cluster. Moving at an average of about 43 kilometres a second, the members of the Hyades are receding from us towards a divergent point near the bright star Betelgeuse in the shoulder of Orion. 50 million years hence, the Hyades will be invisible to the naked eye as seen from Earth, looking like a non-descript open cluster and providing a much smaller target for the Moon to occult at 20’ across. Astronomer Lewis Boss was the first to plot the motion of the Hyades through space in 1908, and the cluster stands as an essential rung on the cosmic distance ladder, with agreeing measurements independently made by both Hubble and Hipparcos and soon to be refined by Gaia.

Photographing and documenting this week’s passage of our Moon across the Hyades is easy with a DSLR camera: don’t be afraid to vary those ISO and shutter speeds to get the mix of the brilliant crescent Moon, the fainter earthshine, and background stars just right. The more adventurous might want to try actually catching the numerous occultations of bright stars on video. And U.S. and Canadian west coast observers are well placed to catch the Moon cross right though the core of the Hyades… a video animation of the event is not out of the question!

And from there, the Moon heads on to its date with destiny and a fine total lunar eclipse on April 15th which favors North American longitudes. We’ll be back later this week with our complete and comprehensive eclipse guide!

Stunning Astrophoto: Moon in the Lighthouse

The full Moon in this sequence was captured at the Cape Espichel lighthouse near Cabo Espichel, Sesimbra, Portugal on March 16, 2014. Credit and copyright: Miguel Claro.

The March full Moon, sometimes called the “Worm Moon” for signaling the coming of spring in the northern hemisphere. This artistically stunning image taken by astrophotopher Miguel Claro is a sequence of 93 images taken at 2-minute intervals as the Moon traveled across the sky and past the Cape Espichel lighthouse near Sesimbra, Portugal. Miguel tells us that the lighthouse originally opened in 1790, and by 1865 it was powered by olive oil, changing to regular fuel in 1886, and much later by electricity by about 1926. The lighthouse measures 32 meters high and lies at an altitude of 168m above the see level. Presently, its luminous range is 20 nautical miles, about 38 km out to sea on a clear night.

Miguel used a Canon 60D – 35mm at f/4 ISO500; 1/5 sec. The sequence was taken on March 16, 2014 between 19:16 and 20:42.

Here’s a closeup:

The Cabo Espichel lighthouse near, Sesimbra, Portugal and the full Moon on March 16, 2014. Credit and copyright: Miguel Claro.
The Cabo Espichel lighthouse near, Sesimbra, Portugal and the full Moon on March 16, 2014. Credit and copyright: Miguel Claro.

See more of Miguel’s work at his website.

You can check out other recent full Moon photos and more taken by our readers at our Flickr page.

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.

Zoom to the Moon’s North Pole with this Incredible New Gigapixel Map

A new interactive mosaic from NASA's Lunar Reconnaissance Orbiter covers the north pole of the moon from 60 to 90 degrees north latitude at a resolution of 6-1/2 feet (2 meters) per pixel. Close-ups of Thales crater (right side) zoom in to reveal increasing levels of detail. Image Credit: NASA/GSFC/Arizona State University

OMG – breathtaking! That was my reaction when I clicked on this incredible new interactive map of the moon’s north polar region. Be prepared to be amazed. It took four years and 10,581 images for the LROC (Lunar Reconnaissance Orbiter Camera) team to assemble what’s believed to be the largest publicly available image mosaic in existence. With over 650 gigapixels of data at a resolution of 2 meters per pixel, you’ll feel like you’re dropping in by parachute  to the lunar surface. 

The 91-km Karpinskiy Crater from the new interactive north pole mosaic. See image below for a zoomed-in view. Credit: NASA
Wide view of the 91-km Karpinskiy Crater from the new interactive north pole mosaic. See image below for a zoomed-in view. Credit: NASA/GSFC/Arizona State Univ.

When you call up the map, be sure to click first on the full-screen button below the zoom slider. Now you’re ready for the full experience. With mouse in hand, you’re free to zoom and pan as you please. Take in the view of Whipple Crater shadowed in polar darkeness or zoom to the bottom of Karpinskiy Crater and fly like a bird over its fractured floor.

In this photo, we come in for a closer look at the fracture or rill in Karpinskiy's floor. Notice the boulders on the cliff side. Credit: NASA
In this photo, we come in for a closer look at the fracture or rill in Karpinskiy’s floor. Notice the small, lighter-toned boulders on the cliff side. The images were all taken with the Lunar Reconnaissance Orbiter’s Narrow Angle Camera (NAC).  Credit: NASA/GFSC/Arizona State Univ.

The images are so detailed and the zoom so smooth, there’s nothing artificial about the ride. Except the fact you’re not actually orbit. Darn close though. All the pictures were taken over the past few years by NASA’s Lunar Reconnaissance Orbiter which can fly as low as 50 km (31 miles) over the lunar surface and resolve details the size of a desk.

Printed at 300 dpi (a high-quality printing resolution that requires you to peer very closely to distinguish pixels), the LNPM would be larger than a football field. Credit: NASA
Printed at 300 dpi – a high-quality printing resolution that requires you to peer very closely to distinguish pixels –  the mosaic map would be larger than a football field. Credit: NASA

There are 10 snapshots along the bottom of the map – click them and you’ll be swiftly carried directly to that feature. One of them is the lunar gravity probe GRAIL-B impact site.

The region the gigapixel map covers superimposed on the outline of the U.S. Credit: NASA
The region the gigapixel map covers superimposed on the outline of the U.S. Credit: NASA

To create the 2-D map, a polar stereographic projection was used in to limit mapping distortions. In addition, the LROC team used information from the LOLA and GRAIL teams and an improved camera pointing model to accurately project each image in the mosaic to within 20 meters. For more information on the project, click HERE.

OK, I’ve said enough. Now go take a look!

Surf’s Up on Titan! Cassini May Have Spotted Waves in Titan’s Seas

Cassini VIMS image of specular reflections in one of Titan's lakes from a flyby on July 24, 2012 (NASA/JPL-Caltech/SSI/Jason W. Barnes et al.)

It’s no surprise that Titan’s north polar region is covered with vast lakes and seas of liquid methane — these have been imaged many times by Cassini during its ten years in orbit around Saturn. What is surprising though is just how incredibly smooth the surfaces of these lakes have been found to be.

One would think that such large expanses of surface liquid — some of Titan’s seas are as big the Great Lakes — would exhibit at least a little surface action on a world with an atmosphere as dense as Titan’s. But repeated radar imaging has shown their surfaces to be “as smooth as the paint on a car.” Over the past several years scientists have puzzled over this anomaly but now they may have truly seen the light — that is, reflected light from what could actually be waves on Titan!

Seasonal winds may be finally kicking up waves in Titan's lakes. (Illustration © Ron Miller.)
Seasonal winds may be finally kicking up waves in Titan’s lakes. (Illustration © Ron Miller.)

Using data acquired during flybys of Titan in 2012 and 2013, planetary scientist Jason Barnes from the University of Idaho and a team of researchers from several other institutions including JPL, Cornell, and MIT, have identified what might be waves in the surface of Punga Mare, one of Titan’s biggest lakes.

For a sense of scale, Lake Victoria, the largest lake in Africa, could fit lengthwise across Titan’s 380-km (236-mile) -wide Punga Mare.

Read more: Titan’s North Pole is Loaded with Lakes

Variations in specular highlights in four pixels observed in the surface of Punga Mare by Cassini’s VIMS (Visible and Infrared Mapping Spectrometer) have been interpreted by the team as being the result of waves — or, perhaps more accurately, ripples, seeing as that they are estimated to be a mere 2 centimeters in height.

Still, based on what’s been observed thus far on Titan, that’s downright choppy.

If the Cassini observations interpreted by Barnes et al. are indicative of waves in Punga Mare, they could also explain previous specular variations seen in other bodies of liquid, like the smaller Kivu Lacus (top image).

Map of Titan's northern "Land o' Lakes" made from Cassini radar imaging passes (NASA/JPL/USGS)
Map of Titan’s northern “Land o’ Lakes” made from Cassini high-resolution radar imaging (NASA/JPL/USGS)

“If correct this discovery represents the first sea-surface waves known outside of Earth.”

– Jason W. Barnes et al.

Then again, wave action isn’t the only possible answer. Similar varied specular highlights could also be caused by a wet surface — like a methane mud flat. Further observations will be needed to rule out other possibilities and obtain a more accurate “surf forecast” for Titan.

The findings were presented by Jason Barnes at the 45th Lunar and Planetary Science Conference in Houston on March 17, 2014. Read the team’s abstract here, and read more in this article by Alexandra Witze on Nature News.

China’s Yutu Moon rover starts Lunar Day 4 Awake but Ailing

Chang’e-3/Yutu Timelapse Color Panorama This newly expanded timelapse composite view shows China’s Yutu moon rover at two positions passing by crater and heading south and away from the Chang’e-3 lunar landing site forever about a week after the Dec. 14, 2013 touchdown at Mare Imbrium. This cropped view was taken from the 360-degree timelapse panorama. See complete 360 degree landing site timelapse panorama herein and APOD Feb. 3, 2014. Chang’e-3 landers extreme ultraviolet (EUV) camera is at right, antenna at left. Credit: CNSA/Chinanews/Ken Kremer/Marco Di Lorenzo – kenkremer.com. See our complete Yutu timelapse pano at NASA APOD Feb. 3, 2014: http://apod.nasa.gov/apod/ap140203.htm

Chang’e-3/Yutu Timelapse Color Panorama
This newly expanded timelapse composite view shows China’s Yutu moon rover at two positions passing by crater and heading south and away from the Chang’e-3 lunar landing site forever about a week after the Dec. 14, 2013 touchdown at Mare Imbrium. This cropped view was taken from the 360-degree timelapse panorama. See complete 360 degree landing site timelapse panorama herein and APOD Feb. 3, 2014. Chang’e-3 landers extreme ultraviolet (EUV) camera is at right, antenna at left. Credit: CNSA/Chinanews/Ken Kremer/Marco Di Lorenzo – kenkremer.com.
See our complete Yutu timelapse pano at NASA APOD Feb. 3, 2014: http://apod.nasa.gov/apod/ap140203.htm[/caption]

KENNEDY SPACE CENTER, FL – China’s maiden moon rover Yutu awoke from her regular two week long slumber on Friday, March 14, to begin the 4th Lunar Day since the probes history making touchdown on the surface of Earth’s nearest neighbor in mid December 2013.

But the endearing robot is still ailing and suffering from mechanical control issues that popped up in late January 2014 according to Chinese space officials.

The Chang’e-3 mothership lander that deposited Yutu onto the pockmarked lunar surface also awoke two days earlier on Wednesday, March 12.

“Yutu and the lander have restarted their operations and are exploring as scheduled,” according to China’s State Administration of Science, Technology and Industry for National Defence (SASTIND), responsible for executing the Chang’e-3 mission.

Yutu rover drives around Chang’e-3 lander  – from Above And Below. Composite view shows China’s Yutu rover and tracks driving in clockwise direction around Chang’e-3 lander from Above And Below (orbit and surface).  The Chang’e-3 timelapse lander color panorama (bottom) and orbital view (top) from NASA’s LRO orbiter shows Yutu rover after it drove down the ramp to the moon’s surface and began driving around the landers right side, passing by craters and heading south on Lunar Day 1.   It then moved northwest during Lunar Day 2.  Arrows show Yutu’s positions over time.    Credit: CNSA/NASA/Ken Kremer/Marco Di Lorenzo/Mark Robinson
Yutu rover drives around Chang’e-3 lander – from Above And Below. Composite view shows China’s Yutu rover and tracks driving in clockwise direction around Chang’e-3 lander from Above And Below (orbit and surface). The Chang’e-3 timelapse lander color panorama (bottom) and orbital view (top) from NASA’s LRO orbiter shows Yutu rover after it drove down the ramp to the moon’s surface and began driving around the landers right side, passing by craters and heading south on Lunar Day 1. It then moved northwest during Lunar Day 2. Arrows show Yutu’s positions over time. Credit: CNSA/NASA/Ken Kremer/Marco Di Lorenzo/Mark Robinson

Yutu is China’s first ever Moon rover and successfully accomplished a soft landing on the Moon on Dec. 14, 2013, piggybacked atop the Chang’e-3 mothership lander.

However, “the control issues that have troubled Yutu since January remain,” says China’s government owned Xinhua news agency.

The hugely popular ‘Yutu’ rover is still suffering from an inability to maneuver its life giving solar panels. It is also unable to activate its six wheels and move around the surface – as I reported here.

At the time that Yutu’s 2nd Lunar sleep period began on Jan. 25, 2014, Chinese space officials had announced that the robot’s future was in jeopardy after it suffered an unidentified “ mechanical control anomaly” due to the “complicated lunar surface.”

360-degree time-lapse color panorama from China’s Chang’e-3 lander. This new 360-degree time-lapse color panorama from China’s Chang’e-3 lander shows the Yutu rover at five different positions, including passing by crater and heading south and away from the Chang’e-3 lunar landing site forever during its trek over the Moon’s surface at its landing site from Dec. 15-22, 2013 during the 1st Lunar Day. Credit: CNSA/Chinanews/Ken Kremer/Marco Di Lorenzo – kenkremer.com.  See our Yutu timelapse pano at NASA APOD Feb. 3, 2014: http://apod.nasa.gov/apod/ap140203.htm
360-degree time-lapse color panorama from China’s Chang’e-3 lander
This new 360-degree time-lapse color panorama from China’s Chang’e-3 lander shows the Yutu rover at five different positions, including passing by crater and heading south and away from the Chang’e-3 lunar landing site forever during its trek over the Moon’s surface at its landing site from Dec. 15-22, 2013 during the 1st Lunar Day. Credit: CNSA/Chinanews/Ken Kremer/Marco Di Lorenzo – kenkremer.com. See our Yutu timelapse pano at NASA APOD Feb. 3, 2014: http://apod.nasa.gov/apod/ap140203.htm

Earlier this month, China announced that “Yutu suffered a control circuit malfunction in its driving unit.”

“The control circuit problem prevented Yutu from entering the second dormancy as planned,” said Ye Peijian, chief scientist of the Chang’e-3 program, in an exclusive interview with Xinhua.

A functioning control circuit is required to lower the rovers mast and protect the delicate components and instruments mounted on the mast from directly suffering from the extremely harsh cold of the Moon’s recurring night time periods.

“Normal dormancy needs Yutu to fold its mast and solar panels,” said Ye according to CCTV, China’s state run broadcaster.

Fortunately, the panoramic camera, radar and other sciene instruments and equipment are functioning normally, says SASTIND.

Yutu even snapped at least a pair new images of the lander during Lunar Day 3.

See our mosaic of Yutu’s Lunar Day 3 lander image as well as our the complete 360 degree timelapse color panorama from Lunar Day 1 herein and at NASA APOD on Feb. 3, 2014 – assembled by Marco Di Lorenzo and Ken Kremer.

Mosaic of the Chang'e-3 moon lander and the lunar surface taken by the camera on China’s Yutu moon rover from a position south of the lander during Lunar Day 3.   Note the landing ramp and rover tracks at left.  Credit: CNSA/SASTIND/Xinhua/Marco Di Lorenzo/Ken Kremer
Mosaic of the Chang’e-3 moon lander and the lunar surface taken by the camera on China’s Yutu moon rover from a position south of the lander during Lunar Day 3. Note the landing ramp and rover tracks at left. Credit: CNSA/SASTIND/Xinhua/Marco Di Lorenzo/Ken Kremer

By reawakening on March 14, the 140 kg robot also survived for its three month design lifetime on the moon.

Yutu’s goal is to accomplish a roving expedition to investigate the moon’s surface composition and natural resources.

So far the 1200 kg Chang’e-3 lander is functioning as planned during its first three lunar days, says SASTIND.

“The lander’s optical telescope, extreme ultraviolet camera and lunar dust measurement device completed scheduled tasks and obtained a large amount of data,” says China’s government owned Xinhua news agency.

China is only the 3rd country in the world to successfully soft land a spacecraft on Earth’s nearest neighbor after the United States and the Soviet Union.

Stay tuned here for Ken’s continuing Chang’e-3, Orion, Orbital Sciences, SpaceX, commercial space, LADEE, Mars and more planetary and human spaceflight news. Learn more at Ken’s upcoming presentations at the NEAF astro/space convention on April 12/13.

Ken Kremer

Watch a Bright Star Disappear Behind the Moon Monday Night

Lambda Geminorum at 10:43 p.m. March 11 just two minutes before disappearing behind the moon as seen from Minneapolis, Minn. US. Stellarium

Ever dabbled in the occult? You’ll have your chance Monday night March 10 when the waxing gibbous moon glides in front of the star Lambda Geminorum for much of North America, occulting it from view for an hour or more. Occultations of stars by the moon happens regularly but most go unnoticed by casual skywatchers. Lambda is an exception because it’s one of the brighter stars that happens to lie along the moon’s path. Shining at magnitude +3.6, any small telescope and even a pair of 10×50 or larger binoculars will show it disappear along the dark edge of the moon. 

Map showing where the occulation of Lambda Gem will be visible. Credit: International Occultation Timing Assn. (IOTA)
Map showing where the disappearance (right half of tube-like figure) and reappearance of Lambda Gem will be visible. Credit: International Occultation Timing Assn. (IOTA)

With a telescope you can comfortably watch the star creep up to the moon’s edge and better anticipate the moment of its disappearance. The fun starts a few minutes before the impending black out when the moon, speeding along its orbit at some 2,280 mph (3,700 km/hr),  draws very close to the star. During the final minute, Lambda may seem to hover forever at the moon’s invisible dark limb, and then – PFFFT – it’s gone! Whether you’re looking through telescope or binoculars, the star will blink out with surprising suddenness because the moon lacks an atmosphere.

Disappearance and reappearance seen from Minneapolis, Minn. Monday night. I've lightened the moon so you can see the dark limb. You'll likely not see this edge in a telescope because of glare. Stellarium
Disappearance and reappearance seen from Minneapolis, Minn. Monday night. I’ve lightened the moon so you can see the dark limb. You’ll likely not see this edge in a telescope because of glare. Stellarium

If there was air up there, Lambda would gradually dim and disappear. Even without special instruments, early astronomers could be certain the moon had little if anything to protect it from the vacuum of space by observing occultations.

As the moon moves approximately its own diameter in an hour, you can watch Lambda re-emerge along the bright limb roughly an hour later, though its return will lack the drama and contrast of a dark limb disappearance. While occultations allow us to see how swiftly the moon moves in real time as well as provide information on its atmosphere or lack thereof, real science can be done, too.


Planets also are occasionally occulted by the moon. Time lapse of Venus’ disappearance on May 16, 2010

Observers along the occultation boundary in the southern U.S. can watch the star pop in and out of view as it’s alternately covered and uncovered by lunar peaks jutting from the moon’s limb. Before spacecraft thoroughly mapped the moon, careful timings made during these “grazing occultations” helped astronomers refine the profile of the moon’s limb as well as determine elevations of peaks and crater walls in polar regions. They can still be useful for refining a star’s position and motion in the sky.

The moon’s limb can also be used much like a doctor’s scalpel  to split unsuspected  double stars that otherwise can’t be resolved by direct observations. Take Lambda Gem for instance. We’ve known for a long time that it totes around a magnitude +10.7 companion star 10 arc seconds to its north-northeast,  but previous occultations of the star have revealed an additional companion only a few hundredths of an arc second away orbiting the bright Lambda primary. The star plays a game of hide-and-seek, visible during some occultations but not others. Estimated by some as one magnitude fainter than Lambda, keep an eye out for it Monday night in the instant after Lambda goes into hiding.


Lunar occultation and reappearance of Antares Oct. 21, 2009

I watched just such a  “two-step” disappearance of Antares and it fainter companion some years back. With brilliant Antares briefly out of view behind the moon’s limb, I easily spotted its magnitude +5.4 companion just 2.5 arc seconds away – an otherwise very difficult feat at my northern latitude.

Want to know more about things that disappear (and reappear) in the night? Make a visit to the International Occultation Timing Association’s website where you’ll find lists of upcoming events, software and how to contribute your observations. If you’re game for Monday night’s occultation, click HERE for a list of cities and times. Remember that the time show is Universal or Greenwich Time. Subtract 4 hours for Eastern Daylight, 5 for Central, 6 for Mountain and 7 for Pacific.  Wishing you clear skies as always!