Slender Moonspotting, Occultations, Daytime Planets and More

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One of nature’s grandest ‘occultations’ of all is coming right up this Friday, as the Moon passes in front of the Sun for viewers in the high Arctic for a total solar eclipse. And although 99.999+% percent of humanity will miss totality, everyone can trace the fascinating path of the Moon as it moves back into the evening sky this weekend.

As of this writing, it looks like the fickle March weather is going to keep us guessing right up to eclipse day. Fear not, as the good folks over at the Virtual Telescope Project promise to bring us views of the eclipse live.  Not only does this eclipse fall on the same day as the start of astronomical spring in the northern hemisphere known as the vernal (northward) equinox, but it also marks the start of lunation 1141.

Ever try hunting for the slender crescent Moon in the dawn or dusk sky? The sport of thin Moon-spotting on the days surrounding the New Moon can push visual skills to the very limit. Binoculars are your friend in this endeavor, as you sweep back and forth attempting to see the slim fingernail of a Moon against the low contrast background sky.  Thursday morning March 19th provides a great chance for North American observers to spy an extremely thin Moon about 24 hours prior to Friday’s eclipse.

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Projected locales for the first sightings of the slim crescent Moon on the evening of March 20th. Credit: Created by author.

Unfortunately, most of North America misses the eclipse, though folks on the extreme east coast of Newfoundland might see a partially eclipsed sunrise if the day dawns clear.

The Moon will first be picked up in the evening sky post-eclipse this weekend. On Friday evening, folks in the southern United States might just be able to spy a 15 hour old Moon with optical assistance if skies are clear.

As the Moon fattens, expect to see it at its most photogenic as Ashen light or Earthshine illuminates its nighttime side. What you’re seeing is sunlight from the Earth being reflected back in a reverse (waning gibbous) phase as seen from the earthward side of the Moon. The prominence of Earthshine can vary depending on the amount of cloud and snow cover currently turned moonward, though of course, if it’s cloudy from your location, you won’t see a thing…

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The universe smiles back: A skewed emoticon grouping of Venus, Mars and the Moon plus Earthshine on February 20th. Photo by author.

Watch that Moon over the coming weeks, as it has a date with destiny.

The Moon occults (passes in front of) two planets and one bright star in the coming week. First up is an occultation of Uranus on March 21st at around 11:00 UT/7:00 AM EDT. Sure, this one is for the most part purely academic and unobservable, as it occurs over central Africa in the daytime and is only 15 degrees east of the Sun. Still, if you can pick up the Moon on the evenings of March 20th or March 21st, you might just be able to spy nearby Uranus shining at +6th magnitude nearby before it heads towards solar conjunction on April 6th.

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The visibility footprint of the March 21st occultation of Mars by the Moon. Credit: Occult 4.1.

Next, the Moon occults Mars on March 21st at 22:00 UT/6:00 PM EDT for the southern Pacific coast of South America. North America will see an extremely close photogenic pairing of Luna and the Red Planet. This is one of seven occultations of a naked eye planet by the Moon for 2015, and the first of two for Mars for the year, the next falling on December 6th.

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The Moon pairs with Venus on the evening of March 22nd. Credit: Stellarium.

Next up, the Moon has a tryst with brilliant Venus, passing 2.8 degrees from the Cytherean world on March 22nd. Can you spy -4th magnitude Venus near the two day old Moon before sunset? This is the stuff that has inspired astronomically-themed flags and skewed emoticon ‘smiley face conjunctions’ of yore, including the close pairing of Mars, Venus and the Moon seen worldwide last month.

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The occultation of Aldebaran by the Moon on March 25th. Credit: Occult 4.1.

Next up, the 30% illuminated Moon occults the bright star Aldebaran for Alaskan viewers at dusk on March 25th. This is the third occultation of the star by the Moon in the ongoing cycle, and to date, no one has, to our knowledge, successfully caught an occultation of Aldebaran in 2015… could this streak be broken next week?

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The daytime Moon paired with Jupiter on March 30th. Credit: Starry Night Education software.

And speaking of daytime planet-spotting, Jupiter will sit only five degrees south of the waxing gibbous Moon on the evening of March 30th. Can you spy the giant planet near the daytime Moon in the afternoon sky using binocs? And finally, watch that Moon, as it heads for the third total lunar eclipse of the last 12 months visible from the Americas and the Pacific region on the morning of April 4th

More to come!

Half-Moon Makes Dramatic Pass at Uranus Tonight

The half-moon creeps up on the planet Uranus this evening. The two will be near each other all night in the constellation Pisces, but closest - less than one-third of a moon diameter apart - just before midnight (CST). The views are what you'll see in a pair of binoculars. The 4th magnitude star Delta Piscium is at top in the field. Source: Stellarium

Sunlight. Moonlight. Starlight. I saw all three for the first time in weeks yesterday. Filled with photons, I feel lighter today, less burdened. Have you been under the clouds too? Let’s hope it’s clear tonight because there’s a nice event you’ll want to see if only because it’s so effortless.

The half-moon will pass very close to the planet Uranus for skywatchers across North America this evening Sunday, Dec. 28th. Pop the rubber lens caps off those binoculars and point them at the Moon. If you look a short distance to the left you’ll notice a star-like object. That’s the planet!

Seattle, two time zones west of the Midwest, will see the two closest around 9:30 p.m. local time. Source: Stellarium
Seattle, two time zones west of the Midwest, will see the two closest around 9:30 p.m. local time. Source: Stellarium

You can do this anytime it’s dark, but the later you look the better because the Moon moves eastward and closer to the planet as the hours tick by. Early in the evening, the two will be separated by a couple degrees, but around 11:30 p.m. CST (9:30 p.m. PST) when the Moon reclines in the western sky, the planet will dangle like an solitary diamond less than a third of a lunar diameter away. When closest to the Moon, Uranus may prove tricky to see in its glare. If you hide the Moon behind a chimney, roofline or power pole, you’ll find it easier to see the planet.

The farther north you live, the closer the twain will be. Skywatchers in Japan, the northeastern portion of Russia, northern Canada and Alaska will see the Moon completely hide Uranus for a time. The farther west you are, the higher the Moon will be when they conjoin. West Coast states see the pair highest when they’re closest, but everyone will get a good view.

Binocular view from the desert city of Tucson around 10:45 p.m. local time tonight. Source: Stellarium
Binocular view from the desert city of Tucson around 10:45 p.m. local time tonight. You can see that the Moon is a little farther north of the planet compared to the view from Seattle. The 1,500 miles between the two cities is enough to cause our satellite, which is relatively close to the Earth, to shift position against the background stars. Source: Stellarium

When closest, the radically different character of each world can best be appreciated in a telescope. Pump the magnification up to 150x and slide both planet and Moon into the same field of view. Uranus, a pale blue dot, wears a permanent cover of methane-laced clouds where temperatures hover around -350°F (-212°C).

Though the moon will be lower in the sky, observers in the eastern U.S. and Canada will still see planet and moon only about 1/2 degree apart before moonset. Source: Stellarium
Though the Moon will be lower in the sky in the eastern U.S. and Canada when it’s closest to Uranus, observers there will still see planet and Moon only 1/2 degree apart shortly before moonset. Source: Stellarium

The fantastically large-appearing Moon in contrast has precious little atmosphere and its sunny terrain bakes at 250°F (121°C). And just look at those craters! First-quarter phase is one of the best times for Moon viewing. The terminator or shadow-line that divides lunar day from night slices right across the middle of the lunar landscape.

Shadows cast by mountain peaks and crater rims are longest and most dramatic around this time because we look squarely down upon them. At crescent and gibbous phases, the terminator is off to one side and craters and their shadows appear scrunched and foreshortened.

The day-night line or terminator cuts across a magnificent landscape rich with craters and mountain ranges emerging from the lunar night. Several prominent lunar "seas" or maria and prominent craters are shown. Credit: Christian Legrand and Patrick Chevalley / Virtual Moon Atlas
The day-night line or terminator cuts across a magnificent landscape rich with craters and mountain ranges emerging from the lunar night. Several prominent lunar “seas” or maria and prominent craters are shown. Credit: Christian Legrand and Patrick Chevalley / Virtual Moon Atlas

Enjoy the tonight’s conjunction and consider the depth of space your view encompasses. Uranus is 1.85 billion miles (2.9 billion km) from Earth today, some 7,700 times farther away than the half-moon.

The Top 101 Astronomical Events to Watch for in 2015

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Phew! It’s here.

Now in its seventh year of compilation and the second year running on Universe Today, we’re proud to feature our list of astronomical happenings for the coming year. Print it, bookmark it, hang it on your fridge or observatory wall. Not only is this the yearly article that we jokingly refer to as the “blog post it takes us six months to write,” but we like to think of it as unique, a mix of the mandatory, the predictable and the bizarre. It’s not a 10 ten listicle, and not a full-fledged almanac, but something in between.     

A rundown of astronomy for 2015: There’s lots of astronomical action to look forward to in the coming year. 2015 features the minimum number of eclipses that can occur, two lunars and two solars. The Moon also reaches its minimum standstill this coming year, as its orbit runs shallow relative to the celestial equator. The Moon will also occult all naked eye planets except Saturn in 2015, and will occult the bright star Aldebaran 13 times — once during every lunation in 2015. And speaking of Saturn, the rings of the distant planet are tilted an average of 24 degrees and opening to our line of sight in 2015 as they head towards their widest in 2018.

Finally, solar activity is trending downwards in 2015 after passing the sputtering 2014 maximum for solar cycle #24 as we now head towards a solar minimum around 2020.

Our best bets: Don’t miss these fine celestial spectacles coming to a sky near YOU next year:

– The two final total lunar eclipses in the ongoing tetrad, one on April 4th and September 28th.

– The only total solar eclipse of 2015 on March 20th, crossing the high Arctic.

– A fine dusk pairing of the bright planets Jupiter and Venus on July 1st.

– Possible wildcard outbursts from the Alpha Monocerotid and Taurid meteors, and a favorable New Moon near the peak of the August Perseids.

– Possible naked eye appearances by comet Q2 Lovejoy opening 2015 and comet US10 Catalina later in the year.

– The occultation of a naked eye star for Miami by an asteroid on September 3rd.

– A series of fine occultations by the Moon of bright star Aldebaran worldwide.

The rules: The comprehensive list that follows has been lovingly distilled down to the top 101 astronomical events for 2015 worldwide. Some, such as lunar eclipses, are visible to a wide swath of humanity, while others, such as many of the asteroid occultations or the sole total solar eclipse of 2015 happen over remote locales. We whittled the list down to a “Top 101” using the following criterion:

Meteor showers: Must have a predicted ZHR  greater than 10.

Conjunctions: Must be closer than one degree.

Asteroid occultations: Must have a probability ranking better than 90 and occult a star brighter than magnitude +8.

Comets: Must reach a predicted brightness greater than magnitude +10. But remember: comets don’t always read prognostications such as this, and may over or under perform at whim… and the next big one could come by at any time!

Times quoted are geocentric unless otherwise noted, and are quoted in Universal Time in a 24- hour clock format.

These events are meant to merely whet the appetite. Expect ‘em to be expounded on fully by Universe Today as they approach. We linked to the events listed where possible, and provided a handy list of resources that we routinely consult at the end of the article.

Got it? Good… then without further fanfare, here’s the top 101 astronomical events for 2015 in chronological order:

The path of Comet Q2 Lovejoy From January 1st to January 31st.
The path of Comet Q2 Lovejoy from January 1st to January 31st. Created using Starry Night Education software.

January

01- Comet C/2012 Q2 Lovejoy may reach naked eye visibility.

04- The Quadrantid meteors peak at 02:00 UT, favoring northern Europe with an expected ZHR of 120.

04- The Earth reaches perihelion at ~8:00 UT.

14- Mercury reaches greatest evening elongation 18.9 degrees east of the Sun at ~16:00 UT.

17- The moons Io and Europa cast a double shadow on Jupiter from 3:53 to 4:58 UT.

20- Mars passes 0.2 degrees from Neptune at ~20:00 UT.

24- A triple shadow transit of Jupiter’s moons occurs from 6:26 to 6:54 UT.

29- The Moon occults Aldebaran at ~17:31 UT for the Arctic, marking the first of 13 occultations of the star by the Moon in 2015.

The view at 6:40 UT.
The view at 6:40 UT on January 24th, as 3 of Jupiter’s moons cast shadows on to the Jovian cloud tops simultaneously. Created using Starry Night Education software.

February

01- Venus passes 0.8 degrees south of Neptune at ~17:00 UT.

05- Earth crosses through Jupiter’s equatorial plane, marking the middle of occultation and eclipse season for the Galilean moons.

06- Jupiter reaches opposition at ~18:00 UT.

18- A “Black Moon” occurs, in the sense of the third New Moon in a season with four.

22- Venus passes 0.4 degrees south of Mars at 5:00 UT.

24- Mercury reaches greatest morning elongation at 26.7 degrees west of the Sun at 19:00 UT.

25- The Moon occults Aldebaran for northern Europe at 23:26 UT.

Credit: Eclipse-Maps
The path of the only total solar eclipse of 2015, occurring on March 20th. Credit: Michael Zeiler/Eclipse-Maps.

March

01- Geostationary satellite & Solar Dynamics Observatory eclipse season begins on the weeks leading up to the March Equinox.

04- Venus passes 0.1 degrees north of Uranus at ~18:00 UT. This is the closest planet-planet conjunction of 2015.

05- A Minimoon occurs, marking the most distant Full Moon of 2015 at 18:07 UT, just 10 hours from apogee.

11- Mars passes 0.3 degrees north of Uranus at ~16:00 UT.

20- A total solar eclipse occurs over the Arctic centered on 9:47 UT.

20- The March northward equinox occurs at 22:45 UT.

21- The Moon occults Mars for South America at ~22:14 UT.

25- The Moon occults Aldebaran for northwestern North America at ~7:17 UT.

Stellarium
Neith lives… the close passage of Uranus near Venus on March 4th. Credit: Stellarium.

April

04- A total lunar eclipse occurs, centered on 12:01 UT and visible from eastern Asia, the Pacific and the Americas.

08- Mercury passes 0.5 degrees from Uranus at ~11:00 UT.

21- The Moon occults Aldebaran for northern Asia at ~16:57 UT.

22- The Lyrid meteors peak at 24:00 UT, favoring northern Europe with a ZHR of 18.

May

05- The Eta Aquarid meteors peak (time variable), with an estimated ZHR of 55.

07- Mercury reaches greatest evening elongation at 21.2 degrees east of the Sun at 4:00 UT.

19- The Moon occults Aldebaran for northern North America at ~2:53 UT .

20- Comet C/2014 Q1 PanSTARRS may reach binocular visibility.

21- Io and Ganymede both cast shadows on Jupiter from 00:04 to 00:33 UT.

21- Callisto and Europa both cast shadows on Jupiter from 13:26 to 13:59 UT.

23- Saturn reaches opposition at ~1:00 UT.

24- Asteroid 1669 Dagmar occults the +1st magnitude star Regulus at ~16:47 UT for the Arabian peninsula,

the brightest star occulted by an asteroid for 2015. 

28- Ganymede and Io both cast shadows on Jupiter from 02:01 to 04:18 UT.

30- Comet 19P/Borrelly may reach binocular visibility.

June

01- The International Space Station reaches full illumination as the June solstice nears, resulting in multiple nightly passes favoring  northern hemisphere observers.

04- Io and Ganymede both cast shadows on Jupiter from 4:54 to 6:13 UT.

05- Venus reaches greatest eastern (dusk) elongation for 2015, 45 degrees from the Sun at 16:00 UT.

10- Asteroid 424 Gratia occults a +6.1 magnitude star at ~15:10 UT for northwestern Australia.

15- The Moon occults Mercury for the South Indian Ocean at ~2:26 UT.

15- Moon occults Aldebaran in the daytime for the high Arctic at ~11:33 UT.

16- Comet C/2014 Q1 PanSTARRS may reach naked eye visibility.

21- The June northward solstice occurs at 16:38 UT.

24- Mercury reaches greatest (morning) elongation at 22.5 degrees west of the Sun at 17:00 UT.

Stellarium
Venus and Jupiter pair together low in the west on July 1st. Credit: Stellarium.

July

01- Venus passes 0.4 degrees from Jupiter at 9:00 UT, marking the closest conjunction of two naked eye planets for 2015.

02- Comet C/2013 US10 Catalina may reach binocular visibility.

06- Earth reaches aphelion at 13:00 UT.

06- Pluto reaches opposition at 15:00 UT, just a week prior to New Horizons’ historic flyby of the distant world.

12- The Moon occults Aldebaran for northeastern Asia ~18:17 UT.

19- The Moon occults Venus for the South Pacific at ~1:07 UT.

25- Asteroid 49 Pales occults a +6.6 magnitude star at 10:55 UT for Mexico.

28- The Delta Aquarids peak (time variable) with a predicted ZHR of 16.

31- A “Blue Moon” occurs, in the sense of the second Full Moon in a given month.

Credit:
The light curve of comet C/2013 US10 Catalina through its peak in 2015. Credit: Seiichi Yoshida’s Weekly Information About Bright Comets.

August

07- Mercury, Jupiter and Regulus pass within a degree of each other over the next few evenings.

08- The Moon occults Aldebaran for central Asia at ~23:45 UT.

13- The Perseid meteors peak from 06:30 to 09:00 UT, with a maximum predicted ZHR of 100 favoring North America.

19- Mars crosses the Beehive Cluster M44.

28- Asteroid 16 Psyche occults a +6.4 magnitude star at ~9:49 UT for Bolivia and Peru.

29- Supermoon 1 of 3 for 2015: The Moon reaches Full at 18:38 UT, 20 hours from perigee.

Lunar eclipse
The path of the Moon through the Earth’s shadow on September 28th. Credit: Fred Espenak/NASA/GSFC

September

01- Neptune reaches opposition at ~3:00 UT.

03- Asteroid 112 Iphigenia occults a +3rd magnitude star for Mexico and Miami at ~9:20 UT. This is the brightest star occulted by an asteroid in 2015 for North America.

02- Geostationary satellite and SDO eclipse season begins as we approach the September equinox.

04- Mercury reaches its greatest elongation for 2015, at 27 degrees east of the Sun at 8:00 UT in the dusk skies.

05- The Moon occults Aldebaran for northeastern North America at ~5:38 UT.

13- “Shallow point” (also known as the minor lunar standstill) occurs over the next lunation, as the Moon’s orbit reaches a shallow minimum of 18.1 degrees inclination with respect to the celestial equator… the path of the Moon now begins to widen towards 2025.

13- A partial solar eclipse occurs, centered on 6:55 UT crossing Africa and the Indian Ocean.

23- The September southward equinox occurs at 8:20 UT.

25- Mars passes 0.8 degrees from Regulus at ~4:00 UT.

28- A total lunar eclipse occurs centered on 2:48 UT, visible from the Pacific, the Americas and eastern Europe.

28- Supermoon 2 of 3 for 2015: The Moon reaches Full at 2:52 UT, approximately an hour from perigee. This marks the closest Full Moon of the year.

Credit
The path of the September 3rd occultation of a +3rd magnitude star by an asteroid over central Mexico and the Florida Keys. Credit: IOTA/Steve Preston.

October

01- Comet C/2013 US10 Catalina may reach naked eye visibility.

02- The Moon occults Aldebaran for the northern Pacific at 13:14 UT.

02- Io and Callisto both cast shadows on Jupiter from 12:26 to 13:35 UT.

08- The Moon occults Venus for Australia at ~20:32 UT.

11- The Moon occults Mercury for Chile at ~12:00 UT.

12- Uranus reaches opposition at ~3:00 UT.

16- Mercury reaches greatest elongation (morning) 18.1 degrees west of the Sun at 10:00 UT.

17- Mars passes 0.4 degrees from Jupiter at 22:00 UT.

18- Io and Ganymede both cast shadows on Jupiter from 10:45 to 12:10 UT.

21- The Orionid meteors peak (time variable) with a projected ZHR of 15.

25- Venus passes 1 degree from Jupiter ~19:00 UT.

25- Io and Ganymede both cast shadows on Jupiter from 12:37 to 14:51 UT.

27- Supermoon 3 of 3 for 2015: The Moon reaches Full at 12:06 UT, 23 hours from perigee.

29- The Moon occults Aldebaran for Europe at ~23:07 UT.

Credit
The Moon occults Aldebaran: the visibility footprint for North America. The dashed line denotes the area in which the event occurs during the daytime. Credit: Occult 4.1.0.11.

November

01- Io and Ganymede both cast shadows on Jupiter from 17:36 to 17:47 UT.

02- Venus passes 0.7 degrees south of Mars at 00:30 UT.

12- Will the 7 year “Taurid fireball meteor shower” produce?

18- The Leonid meteor shower peaks at 04:00 UT, with an estimated ZHR of 15 favoring Europe.

22- Are we in for a once per decade Alpha Monocerotids outburst? The 2015 peak arrives at 4:25 UT, favoring Europe… with a max ZHR = 400+ possible.

26- The Moon occults Aldebaran for North America at ~9:56 UT.

29- Comet C/2013 X1 PanSTARRS may reach binocular visibility.

Occultation
The daytime occultation of Venus by the Moon over North America on December 7th. Credit: Occult 4.1.0.11.

December

01- The International Space Station reaches full illumination as the December solstice nears, resulting in multiple nightly passes favoring the  southern hemisphere.

04- Mercury occults the +3.3 magnitude star Theta Ophiuchi for South Africa at 16:16 UT prior to dusk.

06- The Moon occults Mars for central Africa at ~2:42 UT.

07- The Moon occults Venus in the daytime for North America at ~16:55 UT.

14- The Geminid meteor shower peaks at 18:00 UT, with a ZHR=120 favoring NE Asia.

22- The December southward solstice occurs at 4:48 UT.

23- The Ursid meteor shower peaks at 2:30 UT with a ZHR variable from 10-50 favoring Europe and the Middle East.

23- The Moon occults Aldebaran for Europe and central Asia at ~19:32 UT.

29- Mercury reaches greatest evening elongation at 19.7 degrees east of the Sun at 00:01 UT.

 

Didn’t see your favorite event on the list? Let us know, and be sure to send in any images of these fine events to Universe Today’s Flickr forum.

Enjoy another exciting year of space and astronomy… we’ll be expounding on these events and more as 2015 unfolds.

Sources:

Occult 4.0

-Kevin McGill’s outstanding astronomical simulations.

-Greatest Elongations of Mercury and Venus.

Stellarium

Starry Night Pro

Orbitron

-Steve Preston’s asteroid occultation predictions for 2015.

-The USNO forecast of phenomena for 2015.

-Seiichi Yoshida’s Weekly Information About Bright Comets.

-Fred Espenak’s NASA Eclipse web page.

-The American Meteor Society’s 2015 predictions.

-The International Meteor Organization’s 2015 page.

-Fourmilab’s lunar perigee and apogee calculator.

 

Uranus Bland? Nope, It’s A Stormy Planet With Interesting Insides

A composite image of Uranus in two infrared bands, showing the planet and its ring system. Picture taken by the Keck II telescope and released in 2007. Credit: W. M. Keck Observatory (Marcos van Dam)

Sometimes first impressions are poor ones. When the Voyager 2 spacecraft whizzed by Uranus in 1986, the close-up view of the gas giant revealed what appeared to a be a relatively featureless ball. By that point, scientists were used to seeing bright colors and bands on Jupiter and Saturn. Uranus wasn’t quite deemed uninteresting, but the lack of activity was something that was usually remarked upon when describing the planet.

Fast-forward 28 years and we are learning that Uranus is a more complex world than imagined at the time. Two new studies, discussed at an American Astronomical Society meeting today, show that Uranus is a stormy place and also that the images from Voyager 2 had more interesting information than previously believed.

Showing the value of going over old data, University of Arizona astronomer Erich Karkoschka reprocessed old images of Voyager 2 data — including stacking 1,600 pictures on top of each other.

He found elements of Uranus’ atmosphere that reveals the southern hemisphere moves differently than other regions in fellow gas giants. Since only the top 1% of the atmosphere is easily observable from orbit, scientists try to make inferences about the 99% that lie underneath by looking at how the upper atmosphere behaves.

“Some of these features probably are convective clouds caused by updraft and condensation. Some of the brighter features look like clouds that extend over hundreds of kilometers,” he stated in a press release.

Voyager 2. Credit: NASA
Voyager 2. Credit: NASA

“The unusual rotation of high southern latitudes of Uranus is probably due to an unusual feature in the interior of Uranus,” he added. “While the nature of the feature and its interaction with the atmosphere are not yet known, the fact that I found this unusual rotation offers new possibilities to learn about the interior of a giant planet.”

It’s difficult to get more information about the inner atmosphere without sending down a probe, but other methods of getting a bit of information include using radio (which shows magnetic field rotation) or gravitational fields. The university stated that Karkoschka’s work could help improve models of Uranus’ interior.

So that was Uranus three decades ago. What about today? Turns out that storms are popping up on Uranus that are so large that for the first time, amateur astronomers can track them from Earth. A separate study on Uranus shows the planet is “incredibly active”, and what’s more, it took place at an unexpected time.

Summer happened in 2007 when the Sun shone on its equator, which should have produced more heat and stormy weather at the time. (Uranus has no internal heat source, so the Sun is believed to be the primary driver of energy on the planet.) However, a team led by Imke de Pater, chair of astronomy at the University of California, Berkeley, spotted eight big storms in the northern hemisphere while looking at the planet with the Keck Telescope on Aug. 5 and 6.

Infrared images of Uranus showing storms at 1.6 and 2.2 microns obtained Aug. 6, 2014 by the 10-meter Keck telescope. Credit: Imke de Pater (UC Berkeley) & Keck Observatory images.
Infrared images of Uranus showing storms at 1.6 and 2.2 microns obtained Aug. 6, 2014 by the 10-meter Keck telescope. Credit: Imke de Pater (UC Berkeley) & Keck Observatory images.

Keck’s eye revealed a big, bright storm that represented 30% of light reflected by the planet at a wavelength of 2.2 microns, which provides information about clouds below the tropopause. Amateurs, meanwhile, spotted a storm of a different sort. Between September and October, several observations were reported of a storm at 1.6 microns, deeper in the atmosphere.

“The colors and morphology of this [latter] cloud complex suggests that the storm may be tied to a vortex in the deeper atmosphere similar to two large cloud complexes seen during the equinox,” stated Larry Sromovsky, a planetary scientist at the University of Wisconsin, Madison.

What is causing the storms now is still unknown, but the team continues to watch the Uranian weather to see what will happen next. Results from both studies were presented at the Division for Planetary Sciences meeting of the American Astronomical Society in Tucson, Arizona today. Plans for publication and whether the research was peer-reviewed were not disclosed in press releases concerning the findings.

‘Frankenstein’ Moon: Tidal Forces From Uranus May Have Contributed to Miranda’s Bizarre Appearance

Uranus' Five Largest Moons
Uranus' five largest moons shown in increasing distance from the planet. Note there is incomplete coverage of Miranda and Ariel. Image credit: NASA/JPL

Miranda, the innermost of Uranus’ five moons, has a “Frankenstein”-like appearance: it looks as though it was pieced together from parts that didn’t quite fit together properly. Plus, it has incredibly diverse surface features including canyons up to 12 times deeper than Earth’s Grand Canyon, impact craters, cliffs, and parallel grooves called sulci.

Over the years, various hypotheses have been presented in an attempt to account for Miranda’s enigmatic appearance. First thought to be the result of a catastrophic impact, disintegration, and subsequent reassembly, scientists now believe that some of Miranda’s features might have been influenced by Uranus itself, and are the result of convection: thermally-induced resurfacing from tidal forces from the planet.

Miranda's Three Coronae
Three large, geometric-shaped features called coronae are visible on Miranda. To date, Venus and Miranda are the only bodies in our solar system on which coronae have been observed. Image Credit: NASA/JPL-Caltech

Miranda was discovered in 1948 by Gerard Kuiper. Although it is only 293 miles (471 kilometers) in diameter (approximately one-seventh that of Earth’s moon,) it has one of the strangest and most varied landscapes in our Solar System.

Central to the new research was analysis of three very large, geometric shaped features known as coronae, which are only found on one other planetary body. Coronae were first identified on Venus in 1983 by Venera 15/16 radar imaging equipment.

A leading theory about their formation has been that they form when warm, sub-surface fluids rise to the surface and form a dome. As the edges of the dome cool, the center collapses and warm fluid leak out its sides, forming a crown-like structure, or corona. Based on this premise, the question is then raised as to what mechanism/processes in Miranda’s past warmed its interior sufficiently to produce warm, sub-surface fluids that resulted in coronae formation. Scientists believe that tidal warming played an important role in the formation of the coronae, but the process by which this internal heating led to these features has remained unclear.

Extensive 3D computer simulations conducted by Brown University’s Noah P. Hammond and Amy C. Barr have produced results that are consistent with the three coronae seen on Miranda. In their paper titled, “Global Resurfacing of Uranus’s Moon Miranda by Convection,” Hammond and Barr summarize their results as follows:

“We find that convection in Miranda’s ice shell powered by tidal heating can generate the global distribution of coronae, the concentric orientation of sub-parallel ridges and troughs, and the thermal gradient implied by flexure. Models that account for the possible distribution of tidal heat ing can even match the precise locations of the coronae, after a reorientation of 60°.”

Using Saturn’s moon Enceladus as a baseline due to its similarity in size, composition, and orbital frequency to Miranda, original calculations estimate that as much as 5 GW of tidal dissipation power could be generated. Hammond and Barr’s simulation results indicate almost twice that amount of power would have been created:

“Simulations that match the thermal gradient from flexure have total power outputs of close to 10 GW , somewhat larger than the total power we predict could be generated during orbital resonance.”

Results from Hammond and Barr’s simulations provide a preliminary set of answers that strive to unlock the mysteries of Miranda’s bizarre appearance. Future simulations and studies into the complex nature of tidal heating will build upon these results to provide further insight into the enigmatic moon we call Miranda.

“Global Resurfacing of Uranus’s Moon Miranda by Convection,” was published online on 15 September 2014 in GEOLOGY, a journal of The Geological Society of America. You can read the abstract here.

Stalking Uranus: A Complete Guide to the 2014 Opposition Season

Uranus as seen through the automated eyes of Voyager 2 in 1986. (Credit: NASA/JPL).

It’s no joke… now is the time to begin searching the much-maligned (and mispronounced) planet Uranus as it reaches opposition in early October leading up to a very special celestial event.

Last month, we looked at the challenges of spying the solar system’s outermost ice giant world, Neptune. Currently located in the adjacent constellation Aquarius, Neptune is now 39 degrees from Uranus and widening. The two worlds had a close conjunction of just over one degree of separation in late 1993, and only long time observers of the distant worlds remember a time waaaay back in the early-1970s where the two worlds appeared farther apart than 2014 as seen from our Earthly vantage point.

Stellarium
Uranus rising to the east the evening of October 7th, just prior to the start of the October 8th lunar eclipse later the same evening. Created  using Stellarium.

In 2014, opposition occurs at 21:00 Universal Time (UT)/5:00 PM EDT on October 7th. If this date sounds familiar, it’s because Full Moon and the second total lunar eclipse of 2014 and the ongoing lunar tetrad of eclipses occurs less than 24 hours afterwards. This puts Uranus extremely close to the eclipsed Moon, and a remote slice of the high Arctic will actually see the Moon occult (pass in front of) Uranus during totality. Such a coincidence is extremely rare: the last time the Moon occulted a naked eye planet during totality occurred back during Shakespearian times in 1591, when Saturn was covered by the eclipsed Moon. This close conjunction as seen from English soil possibly by the bard himself was mentioned in David Levy’s book and doctoral thesis The Sky in Early Modern English Literature, and a similar event involving Saturn occurs in 2344 AD.

Credit:
The footprint of the October 8th occultation of Uranus. Credit: Occult 4.1.

We’re also in a cycle of occultations of Uranus in 2014, as the speedy Moon slides in front of the slow moving world every lunation until December 2015. Oppositions of Uranus — actually pronounced “YOOR-un-us” so as not to rhyme with a bodily orifice — currently occur in the month of September and move forward across our calendar by about 4 days a year.

Credit:
Uranus (lower left) near the limb of the gibbous Moon of September 11th, 2014. Credit: Roger Hutchinson.

This year sees Uranus in the astronomical constellation Pisces just south of the March equinoctial point. Uranus is moving towards and will pass within a degree of the +5.7 magnitude star 96 Piscium in late October through early November. Shining at magnitude +5.7 through the opposition season, Uranus presents a disk 3.7” in size at the telescope. You can get a positive ID on the planet by patiently sweeping the field of view: Uranus is the tiny blue-green “dot” that, unlike a star, refuses to come into a pinpoint focus.

The apparent path of Uranus from September 2014 through January 2015 across the constellation Pisces. The inset shows the tilt and orbit of its major moons across a 2′ field of view. Created by the author using Starry Night Education software.

Uranus also presents us with one of the key mysteries of the solar system. Namely, what’s up with its 97.8 degree rotational tilt? Clearly, the world sustained a major blow sometime in the solar system’s early history. In 2014, we’re viewing the world at about a 28 degree tilt and widening. This will continue until we’re looking straight at the south pole of Uranus in early 2030s. Of course, “south” and “north” are pretty arbitrary when you’re knocked back over 90 degrees on your axis! And while we enjoy the September Equinox next week on September 23rd, the last equinox for any would-be “Uranians” occurred on December 16th, 2007. This put the orbit of its moons edge-on from our point of view from 2006-2009 for only the third time since discovery of the planet in 1781. This won’t occur again until around 2049. Uranus also passed aphelion in 2009, which means it’s still at the farther end of its 19.1 to 17.3 astronomical unit (A.U.) range from the Sun in its 84 year orbit.

The moons of Uranus and Neptune as imaged during the 2011 opposition season. Credit: Rolf Wahl Olsen, used with permission.
The moons of Uranus and Neptune as imaged during the 2011 opposition season. Credit: Rolf Wahl Olsen, used with permission.

And as often as Uranus ends up as the butt (bad pun) of many a scatological punch line, we can at least be glad that the world didn’t get named Georgium Sidus (Latin for “George’s Star”) after William Herschel’s benefactor, King George the III. Yes, this was a serious proposal (!). Herschel initially thought he’d found a comet upon spying Uranus, until he realized its slow motion implied a large object orbiting far out in the solar system.

A replica... Credit:
A replica of the reflecting telescope that Herschel used to discover Uranus. Credit: Alun Salt/Wikimedia Commons image under a Creative Commons Attribution Share-Alike 2.0 license.

Spurious sightings of Uranus actually crop up on star maps prior to Herschel’s time, and in theory, it hovers juuusst above naked eye visibility near opposition as seen from a dark sky site… can you pick out Uranus without optical assistance during totality next month? Hershel and Lassell also made claims of spotting early ring systems around both Uranus and Neptune, though the true discovery of a tenuous ring system of Uranus was made by the Kuiper Airborne Observatory (a forerunner of SOFIA) during an occultation of a background star in 1977.

Credit: Ed Kotapish
A corkscrew chart for the moons of Uranus through October. Credit: Ed Kotapish/Rings PDS node.

Looking for something more? Owners of large light buckets can capture and even image (see above) 5 of the 27 known moons of Uranus. We charted the orbital elongations for favorable apparitions through October 2014 (to the left). Check out last year’s chart for magnitudes, periods, and maximum separations for each respective moon. An occulting bar eyepiece may help you in your quest to cut down the ‘glare’ of nearby Uranus.

When will we return to Uranus? Thus far, humanity has explored the world up close exactly once, when Voyager 2 passed by in 1986. A possible “Uranus Probe” (perhaps, Uranus Orbiter is a better term) similar to Cassini has been an on- and off- proposal over the years, though it’d be a tough sell in the current era of ever dwindling budgets. Plutonium, a mandatory power source for deep space missions, is also in short supply. Such a mission might take up to a decade to enter orbit around Uranus, and would represent the farthest orbital reconnaissance of a world in our solar system. Speedy New Horizons is just whizzing by Pluto next July.

All great thoughts to ponder as you scour the skies for Uranus in the coming weeks!

Power Up! Distant Uranus Sees A Storm Surge Of ‘Monstrous’ Proportions

Huge storms on Uranus were spotted by the Keck Observatory on Aug. 5 and Aug. 6, 2014. Credit: Imke de Pater (UC Berkeley), Pat Fry (University of Wisconsin), Keck Observatory

Who can imagine Uranus as a quiet planet now? The Keck Observatory caught some spectacular pictures of the gas giant undergoing a large storm surge a few days ago, which took astronomers by surprise because the planet is well past the equinox in 2007, when the sun was highest above the equator.

“We are always anxious to see that first image of the night of any planet or satellite, as we never know what it might have in store for us,” stated Imke de Pater, an astronomer at the University of California, Berkeley that led the research.

“This extremely bright feature we saw on UT 6 August 2014 reminds me of a similarly bright storm we saw on Uranus’s southern hemisphere during the years leading up to and at equinox.”

Astronomers say the brightest of the storms is “monstrous” and reminds them of a dissipated feature nicknamed the “Berg”, since it looked a bit like an iceberg.

These two pictures of Uranus -- one in true color (left) and the other in false color -- were compiled from images returned Jan. 17, 1986, by the narrow-angle camera of Voyager 2. Image credit: NASA/JPL
These two pictures of Uranus — one in true color (left) and the other in false color — were compiled from images returned Jan. 17, 1986, by the narrow-angle camera of Voyager 2. Image credit: NASA/JPL

The Berg, which might have been there when one of the Voyager spacecraft flew by in 1986, moved between the southern latitudes of 32 and 36 degrees between 2000 and 2005. After getting brighter in 2004, it moved towards the equator and got even stronger, where it remained until falling apart in 2009. (You can see pictures of it here.)

“The present storm is even brighter than the Berg. Its morphology is rather similar, and the team expects it may also be tied to a vortex in the deeper atmosphere,” Keck stated. Based on how bright the storm appears, researchers believe it must be reaching high into the atmosphere, perhaps approaching the tropopause (just below the stratosphere)

Source: Keck Observatory

Cassini’s View of Another Pale Blue Dot

Uranus as seen by Cassini on July 19, 2013 (NASA/JPL-Caltech/SSI)

When you hear the words “pale blue dot” you’re probably reminded of the famous quote by Carl Sagan inspired by an image of Earth as a soberingly tiny speck, as imaged by Voyager 1 on Feb. 14, 1990 from beyond the orbit of Pluto. But there’s another pale blue world in our Solar System: the ice giant Uranus, and its picture was captured much more recently by the Cassini spacecraft from orbit around Saturn on April 11, 2014.

Released today by the Cassini Imaging Team, the image above shows Uranus as a tiny blue orb shining far beyond the bright hazy bands of Saturn’s F ring.

“Do you relish the notion of being a Saturnian, and gazing out from the lofty heights of Saturn at the same planets we see here from the Earth?”
– Carolyn Porco, Cassini Imaging Team Leader

Uranus’ coloration is a result of methane high in its frigid atmosphere. According to the description on the CICLOPS site, “methane on Uranus — and its sapphire-colored sibling, Neptune — absorbs red wavelengths of incoming sunlight, but allows blue wavelengths to escape back into space, resulting in the predominantly bluish color seen here.”

This was also the first time Uranus had been imaged by the Cassini spacecraft, which has been in orbit around Saturn since 2004. In fact its ten-year orbital anniversary will come on July 1.

This image adds one more planet to the list of worlds captured on Camera by Cassini, which made headlines last fall when a glorious mosaic was released that featured a backlit Saturn in eclipse surrounded by its luminous rings, the specks of several of its moons, and the distant dots of Venus, Mars, and the Earth and Moon. Made from 141 separate exposures, the mosaic was captured on July 19, 2013 — known by many space aficionados as “the day the Earth smiled” as it was the first time the world’s population was alerted beforehand that its picture would be taken from over 900 million miles away.

Saturn — with its terrestrial spacecraft in tow — was about 28.6 AU away from Uranus when the image was acquired. That’s about  4.28 billion kilometers (2.66 billion miles). From that distance the glow of the 51,118-kilometer (31,763-mile) -wide Uranus is reduced to a mere few pixels (which required digital brightening by about 4.5x, as well.)

Read more on the Cassini Imaging Central Laboratory for Operations (CICLOPS) page here and in a news release from NASA’s JPL here.

Image credit: NASA/JPL-Caltech/SSI. Source: Carolyn Porco, CICLOPS Director

Astrophoto: Uranus at Opposition

Uranus, imaged from Italy on October 3, 2013, when the planet was at opposition. Credit and copyright: Giuseppe Petricca.

Last week, we asked if you were looking for an observing challenge: looking for planet Uranus when it reached opposition — where it is opposite the Sun the sky, meaning the planet rises as the Sun sets. Giuseppe Petricca from Italy took the challenge and ran with it. His skies over Sulmona, Abruzzo in Italy cleared, and not even 12 hours after the official time of opposition he got this shot using his new Toucam Pro II on a Newtonian 200/1000 on EQ5 unmotorized mount.

Nice!

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Uranus: A Guide to its 2013 Opposition

Credit:

Up for a challenge? Got a big 12” light bucket of a Dobsonian telescope and looking for something new to point it at? This week, as the Moon reaches New phase on October 4th and stays safely out of the late evening sky, why not check out Uranus and its retinue of moons. And yes, we’ve heard just about ALL the Uranus jokes —its pronounced yer-in-us, thank you very much — but feel free to attempt to pen an original if you must.

Now, back to astronomy. Uranus reaches opposition for 2013  on Thursday, October 3rd at 14:00 Universal Time. Opposition is the point in time that an outer planet rises as the Sun sets. In the case of Uranus, its opposition dates advance forward by about 4-5 days each year.

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The current location of Uranus in Pisces. Created by the author using Stellarium. (click to enlarge).

This also marks the start of the best time to hunt for the planet among the star fields of the constellation Pisces. Uranus will reach its maximum elevation above the southern horizon for northern hemisphere viewers for early October around local midnight. For observers south of the equator, Uranus will transit to the north. Incidentally, Uranus also currently sits near the equinoctial point occupied by the Sun during the March equinox, making viewing opportunities nearly equal for both hemispheres.

Uranus is 19.04 astronomical units distant during opposition 2013, or about 158 light minutes away. Shining at magnitude +5.8, Uranus presents a tiny blue-green disk just under 4” across at opposition.

Uranus currently lies six degrees SW of the +4.4 magnitude star Delta Piscium, on the border of the constellations Pisces and Cetus. Uranus will actually be crossing once again into the non-zodiacal constellation of Cetus later this year.

Discovered in 1781 by Sir William Herschel, Uranus has only completed 2 full orbits (2.75 to be precise) in its 84.3 year trips about the Sun. We can be thankful that William’s proposal to name the planet Geogium Sidus after his benefactor King George the III didn’t stick!

Starry Night Education
The path of Uranus into Cetus. Created by the author using Starry Night Education software.

At opposition, Uranus will be located at;

Right Ascension: 0h 40’

Declination: +3° 25’

Five of the 27 known moons of Uranus are also within the grasp of a moderate-sized backyard scope as well. The trick is to catch ‘em near greatest elongation, when they appear farthest from the “glare of Uranus” (hey, there’s a freebie for a snicker or two). An eyepiece equipped with an occulting bar, or simply nudging Uranus out of the field of view can also help.

With magnitudes ranging from +13 to +16, the moons of Uranus are similar in brightness to Neptune’s large moon Triton or the tiny world Pluto.

The five brightest moons of Uranus and their respective maximum elongations are:

Chart constructed by author.

And here’s a handy finder chart for the coming month, showing maximum elongations for each:

A corkscrew graph featuring the greatest elongations for the five brightest moons of Uranus. (Created by Ed Kotapish using PDS Rings Node).
A corkscrew graph featuring the greatest elongations for the five brightest moons of Uranus through October. (Created by Ed Kotapish using PDS Rings Node).

The first two moons were named Titania and Oberon by William’s son John after characters from William Shakespeare’s A Mid-Summer Night’s Dream. William discovered the first two moons of Uranus on the night of January 11th, 1787 using his 49.5” reflector. His scopes were so advanced for his day, that it wasn’t until over a half a century later that William Lassell discovered Umbriel and Ariel using the Liverpool Observatory’s 24” reflector in 1851.

Gerard Kuiper would later add tiny Miranda to the list, nabbing it with the McDonald Observatory’s 82” Otto Struve Telescope in 1948. We would then have to wait until Voyager 2’s 1986 flyby of Uranus in 1986 to add more. To date, Voyager 2 remains the only spacecraft to visit Uranus and Neptune.

The current convention established by the International Astronomical Union is to name the moons of Uranus after characters from the plays of Shakespeare or Alexander Pope’s Rape of the Lock.

There’s still a wide range of names in said literature to choose from!

It’s interesting to note that the orbits of the moons of Uranus are also currently tipped open about 25 degrees to our line of sight and widening. They were edge on in December 2007, and will be perpendicular to our Earthly view come 2029, after which they’ll head back to edge on in 2049. This is because Uranus and the orbits of its moons are tipped at a 97 degree angle relative to the planet’s orbit. This is why elongations for its moons are often quoted it terms of “north and south” of the planet, rather than the familiar east and west. Shadow transits of the moons can occur with about a year and a half during plane-crossing seasons, but they’re ~42 years apart and tough to spot on the tiny disk of Uranus!

October 4th Starry Night Education
An example of the orientation of Uranus’s moons on October 4th, with Oberon at greatest elongation. Note that Miranda is the tiny unlabeled moon with the interior orbit. (Created by the author using Starry Night Education software).

Uranus also reached aphelion in 2009 at 20.099 AU from the Sun —we’re still at the farther end of the spectrum, as oppositions of Uranus can range from 19.09 to 17.28 AU distant.

Uranus will rise earlier on each successive evening until it reaches quadrature at the end of the year on December 30th. At this point, it’ll be roughly due south at local sunset. Keep in mind, there’s also another ice giant worth hunting for in the adjacent constellation of Aquarius named Neptune.

So ignore those bad puns, and be sure to take out that 10” (scope, that is) and point it at Uranus!