Skywatching Archives

May 20, 2014December 23, 2015 by Bob King

How to See 209P/LINEAR, the Comet Brewing Up Saturday’s Surprise Meteor Shower

Comet 209P/LINEAR may still be faint but it's a beautiful object in this time exposure by Austrian astrophotographer Michael Jaeger. The stars appear as trails because the photographer followed the comet during the exposure.

As we anxiously await the arrival of a potentially rich new meteor shower this weekend, its parent comet, 209P/LINEAR, draws ever closer and brighter. Today it shines feebly at around magnitude +13.7 yet possesses a classic form with bright head and tail. It’s rapidly approaching Earth, picking up speed every night and hopefully will be bright enough to see in your telescope very soon.

As it approaches Earth in the coming nights, comet 209P/LINEAR will appear to move quickly across the sky, traveling from Leo Minor to southern Hydra in little over a week. All maps created with Chris Marriott's SkyMap software — As it approaches Earth in the coming nights, comet 209P/LINEAR will move quickly across the sky, traveling from Ursa Major to southern Hydra in just 10 days. When closest on May 28-29, the comet will cover 10 degrees per day or just shy of 1/2 degree per hour. All maps created with Chris Marriott’s SkyMap software

The comet was discovered in Feb. 2004 by the Lincoln Laboratory Near-Earth Asteroid Research (LINEAR) automated sky survey. Given its stellar appearance at the time of discovery it was first thought to be an asteroid, but photos taken the following month photos by Rob McNaught (Siding Spring Observatory, Australia) revealed a narrow tail. Unlike long period comets Hale-Bopp and the late Comet ISON that swing around the sun once every few thousand years or few million years, this one’s a frequent visitor, dropping by every 5.09 years.

This detailed map shows the comet's path from Leo Minor across the backside of the Sickle of Leo May 23-26. Hopefully it will be bright enough then to spot in an 8-inch or larger telescope. Click to enlarge and then print out for use at the telescope. — This detailed map shows the comet’s path from Leo Minor across the backside of the Sickle of Leo May 23-26. Hopefully it will be bright enough then to spot in an 8-inch or larger telescope. On May 25, it passes close to the colorful double star Gamma Leonis and a pair of NGC galaxies. Stars plotted to magnitude +9. Click to enlarge and then print out for use at the telescope.

209P/LINEAR belongs to the Jupiter family of comets, a group of comets with periods of less than 20 years whose orbits are controlled by Jupiter. When closest at perihelion, 209P/LINEAR coasts some 90 million miles from the sun; the far end of its orbit crosses that of Jupiter. Comets that ply the gravitational domain of the solar system’s largest planet occasionally get their orbits realigned. In 2012, during a relatively close pass of that planet, Jupiter perturbed 209P’s orbit, bringing the comet and its debris trails to within 280,000 miles (450,000 km) of Earth’s orbit, close enough to spark the meteor shower predicted for this Friday night/Saturday morning May 23-24.

Track of the comet through from May 27-29 through the dim constellation Sextans south of Leo. — Track of the comet from May 27-29 through Sextans to the Hydra-Crater border with positions shown every 3 hours. Times are CDT. Click to enlarge.

This time around the sun, the comet itself will fly just 5.15 million miles (21 times the distance to the moon) from Earth around 3 a.m. CDT (8 hours UT) May 29 a little more than 3 weeks after perihelion, making it the 9th closest comet encounter ever observed. Given , you’d think 209P would become a bright object, perhaps even visible with the naked eye, but predictions call for it to reach about magnitude +11 at best. That means you’ll need an 8-inch telescope and dark sky to see it well. Either the comet’s very small or producing dust at a declining rate or both. Research published by Quanzhi Ye and Paul A. Wiegert describes the comet’s current dust production as low, a sign that 209P could be transitioning to a dormant comet or asteroid.

Light curve for comet 209P/LINEAR predicts a maximum magnitude of around 11. Click for more information. Credit: Seiichi Yoshida — Light curve for comet 209P/LINEAR forecasts a maximum magnitude of around 11. Dates are shown along the bottom and magnitude scale along the side. Click for additional information. Credit: Seiichi Yoshida

Fortunately, the moon’s out of the way this week and next when 209P/LINEAR is closest and brightest. Since we enjoy comets in part because of their unpredictability, maybe a few surprises will be in the offing including a brighter than expected appearance. The maps will help you track down 209P during the best part of its apparition. I deliberately chose ‘black stars on a white background’ for clarity in use at the telescope. It also saves on printer ink!

A brand new meteor shower shooting 100 and potentially as many as 400 meteors an hour may radiate from the dim constellation Camelopardalis below the North Star Saturday morning May 24. Each is crumb or pebble of debris lost by 209P/LINEAR during earlier cycles around the sun. This map shows the sky facing north around 2 a.m. from the Saturday May 24 from the central U.S. Stellarium

We’re grateful for the dust 209P/LINEAR carelessly lost during its many passes in the 19th and early 20th centuries. Earth is expected to pass through multiple filaments of debris overnight Friday May 23-24 with the peak of at least 100 meteors per hour – about as good as a typical Perseid or Geminid shower – occurring around 2 a.m. CDT (7 hours UT).

If it’s cloudy or you’re not in the sweet zone for viewing either the comet or the potential shower, astrophysicist Gianluca Masi will offer a live feed of the comet at the Virtual Telescope Project website scheduled to begin at 3 p.m. CDT (8 p.m. Greenwich Time) May 22. A second meteor shower live feed will start at 12:30 a.m. CDT (5:30 a.m. Greenwich Time) Friday night/Saturday morning May 23-24.

SLOOH will also cover 209P/LINEAR live on the Web with telescopes on the Canary Islands starting at 5 p.m. CDT (6 p.m. EDT, 4 p.m. MDT and 3 p.m. PDT) May 23. Live meteor shower coverage featuring astronomer Bob Berman of Astronomy Magazine begins at 10 p.m. CDT. Viewers can ask questions by using hashtag #slooh.

A very exciting weekend lies ahead!

May 19, 2014December 30, 2015 by Nancy Atkinson

Dramatic Timelapse Shows Develpment of Supercell “Mothership” Storm Cloud in Wyoming

Yikes! The Mothership has returned to Wyoming a la “Close Encounters of the Third Kind!” Yesterday a gigantic storm cloud spun into a flying saucer shape in eastern Wyoming near Newcastle and a storm-chasing group called Basehunters captured it all on film. Luckily, by the end of the footage, the storm dissipates.

You can see some images from Twitter below:

Continue reading “Dramatic Timelapse Shows Develpment of Supercell “Mothership” Storm Cloud in Wyoming”

May 19, 2014December 23, 2015 by David Dickinson

Can You Say Camelopardalids? Observing, Weather Prospects and More for the May 24th Meteor Shower

It could be the best of meteor showers, or it could be the…

Well, we’ll delve into the alternatives here in a bit. For now, we’ll call upon our ever present astronomical optimism and say that one of the best meteor showers of 2014 may potentially be on tap for this weekend.

This is a true wild card event. The meteor shower in question hails from a periodic comet 209P LINEAR discovered in 2004 and radiates from the obscure and tongue-twisting constellation of Camelopardalis.

But whether you call ‘em the “209/P-ids,” the “Camelopardalids,” or simply the “Cams,” this weekend’s meteor shower is definitely one worth watching out for. The excitement surrounding this meteor shower came about when researchers Peter Jenniskens and Esko Lyytinen noticed that the Earth would cross debris streams laid down by the comet in 1803 and 1924. Discovered by the LIncoln Near-Earth Asteroid Research (LINEAR) automated all-sky survey located at White Sands, New Mexico, comet 209P LINEAR orbits the Sun once every 5.1 years. 209P LINEAR passed perihelion at 0.97 AUs from the Sun this month on May 6^th.

Looking north from latitude +30N at 7:00 UT on the morning of May 24th. Created using Starry Night.

The meteor shower peaks this coming U.S. Memorial Day weekend on Saturday, May 24^th. The expected peak is projected for right around 7:00 Universal Time (UT) which is the early morning hours of 3:00 AM EDT, giving North America a possible front row seat to the event. Estimates for the Zenithal Hourly Rate (ZHR) of the Camelopardalids run the gamut from a mild 30 to an outstanding 400 per hour. Keep in mind, this is a shower that hasn’t been witnessed, and it’s tough enough to forecast the timing and activity of known showers. It’s really a question of how much debris the 1803 and 1924 streams laid down on those undocumented passages. One possible strike against a “meteor storm” similar to the 1998 Leonids that we witnessed from Kuwait is the fact that the “Cams” have never been recorded before. Still, you won’t see any if you don’t try!

Cams — The orientation of the Earth, the day/night terminator, the Sun, Moon and radiant of the meteor shower on May 24th at 7:00 UT. Created by author.

Comet 209P/LINEAR passes 0.055 AUs — about 8.3 million kilometres — from the Earth on May 29^th, shining at +11^th magnitude and crossing south into the constellation of Leo Minor in late May. Interestingly, it also passes 0.8 degrees from asteroid 2 Pallas on May 26^th. Though tiny, comet 209P/LINEAR’s 2014 passage ranks as the 9^th closest recorded approach of a comet to the Earth.

The Moon is also at an ideal phase for meteor watching this coming weekend as it presents a waning crescent phase just 4 days from New and rises at around 4:00 AM local.

The expected radiant for the Cams sits at Right Ascension 8 hours and declination 78 degrees north in the constellation of Camelopardalis, the “camel leopard…” OK, we’ve never seen such a creature, either. (Read “giraffe”). Unfortunately, this puts the radiant just 20 degrees above the northern horizon as seen from +30 degrees north latitude here in Florida at 7:00 UT. Generally speaking, the farther north you are, the higher the radiant will be in the sky and the better your viewing prospects are. Canada and the northern continental United States could potentially be in for a good show. Keep in mind too, the high northern declination of the radiant means that it transits the meridian (crosses upper culmination) a few hours before sunset Friday night at 6 PM local; this means it’ll have an elevation of about 38 degrees above the horizon as seen from 30 degrees north latitude just after sunset. It may well be worth watching for early activity after dusk!

Weather — A look ahead at the cloud cover prospects for the morning of May 24th. Credit: NOAA.

Clouded out or live on the wrong side of the planet to watch the Camelopardalids? Slooh will be carrying a live broadcast of the event starting at 3:00 PM PDT/ 6:00 PM EDT/ 22:00 UT. Also, the folks at the Virtual Telescope Project will carry two separate webcasts of the event, one featuring the progenitor comet 209P LINEAR starting at 20:00 UT on May 22^nd and another featuring the meteor shower itself starting at 5:30 UT on May 24^th.

Observing meteors is fun and easy and requires nothing more than a good pair of “mark-1 eyeballs” and patience. And although the radiant may be low to the north, meteors can appear anywhere in the sky. We like to keep a pair of binocs handy to examine any lingering smoke trains left by bright fireballs. Counting the number of meteors you see from your location and submitting this estimate to the International Meteor Organization may help in ongoing efforts to understand this first time meteor shower. And capturing an image of a meteor is as simple as setting a DSLR on a tripod with a wide field of view and taking time exposures of the sky… something you can start practicing tonight.

P_20140518_110518 — Our humble meteor observing rig… (Photo by author).

Don’t miss what could well be the astronomical event of the year… I’d love to see a meteor shower named after an obscure constellation such as the #Camelopardalids trending. And we fully expect to start fielding reports of “strange rocks falling from the sky” this week, which the cometary dust that composes a meteor shower isn’t. In fact, Meteorite Man Geoffrey Notkin once noted that no confirmed meteorite fall has ever been linked to a periodic meteor shower.

Don’t miss the celestial show!

-Got pics of the Camelopardalids? Send ‘em to Universe Today. There’s a good chance that we’ll run an after-action photo-round up if the Cams kick it into high gear.

-Read more about the Camelopardalids here in a recent outstanding post by Bob King on Universe Today.

May 18, 2014December 23, 2015 by Bob King

If Pigs Could Fly – A Quick Guide to Solar Halos and Other Curiosities

A circumscribed halo encloses the more common 22-degree halo around the sun Saturday morning (May 17. Credit: Bob King

Call it a porcine occultation. It took nearly a year but I finally got help from the ornamental pig in my wife’s flower garden. This weekend it became the preferred method for blocking the sun to better see and photograph a beautiful pair of solar halos. We often associate solar and lunar halos with winter because they require ice crystals for their formation, but they happen during all seasons.

Nature keeps it simple. Light refracting through or reflecting from six-sided plate and column (pencil-shaped) ice crystals in high clouds is responsible for almost all halos and their variations.

Lower clouds, like the puffy cumulus dotting the sky on a summer day, are composed of water droplets. A typical cumulus spans about a kilometer and contains 1.1 million pounds of water. Cirrostratus clouds are much higher (18,000 feet and up) and colder and formed instead of ice crystals. They’re often the first clouds to betray an incoming frontal system.

Cirrostratus are thin and fibrous and give the blue sky a milky look. Most halos and related phenomena originate in countless millions of hexagonal plate and pencil-shaped ice crystals wafting about like diamond dust in these often featureless clouds.

This is the top end of a hexagonal column-shaped ice crystal. Light refracting (bending) through billions of these crystals spreads out to form a typical solar halo. Credit: Donalbein — This is the top end of a hexagonal column-shaped ice crystal. Light refracting (bending) through the 60-degree angled faces of millions of these crystals is concentrated into a ring of light 22 degrees from the sun. As light leaves the crystal, the shorter blue and purple wavelengths are refracted slightly more than red, tinting the outer edge of the halo blue and inner edge red. Credit: Donalbein with additions by the author

In winter, the sun is generally low in the sky, making it hard to miss a halo. Come summer, when the sun is much higher up, halo spotters have to be more deliberate and make a point to look up more often. The 22-degree halo is the most common; it’s the inner of the two halos in the photo above. With a radius of 22 degrees, an outstretched hand at arm’s length will comfortably fit between sun and circle.

Light refracted or bent through millions of randomly oriented pencil-shaped crystals exits at angles from 22 degrees up to 50 degrees, however most of the light is concentrated around 22 degrees, resulting in the familiar 22-degree radius halo. No light gets bent and concentrated at angles fewer than 22 degrees, which is why the sky looks darker inside the halo than outside. Finally, a small fraction of the light exits the crystals between 22 and 50 degrees creating a soft outer edge to the circle as well as a large, more diffuse disk of light as far as 50 degrees from the sun.

The sun on Dec. 6, 2013 with a 22-degree halo and two luminous canine companions or sundogs. Credit: Bob King — The sun on Dec. 6, 2013 with a 22-degree halo and two luminous canine companions or sundogs. Similar halos and ‘moondogs’ can be seen around a bright moon. Credit: Bob King

Sundogs, also called mock suns or parhelia, are brilliant and often colorful patches of light that accompany the sun on either side of a halo. Not as frequent as halos, they’re still common enough to spot half a dozen times or more a year. Depending on how extensive the cloud cover is, you might see only one sundog instead of the more typical pair. Sundogs form when light refracts through hexagonal plate-shaped ice crystals with their flat sides parallel to the ground. They appear when the sun is near the horizon and on the same horizontal plane as the ice crystals. As in halos, red light is refracted less than blue, coloring the dog’s ‘head’ red and its hind quarters blue. Mock sun is an apt term as occasionally a sundog will shine with the intensity of a second sun. They’re responsible for some of the daytime ‘UFO’ sightings. Check this one one out on YouTube.

An especially colorful sundog with a 'tail' from 2008. Credit: Bob King — An especially colorful sundog with a ‘tail’. Red light is bent less than blue as it emerges from the ice crystal, tinting the sundog’s inner edge. Blue is bent more and colors the outer half. If you look closely, all colors of the rainbow are seen. Credit: Bob King

Wobbly crystals make for taller sundogs. Like real dogs, ice crystal sundogs can grow tails. These are part of the much larger parhelic circle, a rarely-seen narrow band of light encircling the entire sky at the sun’s altitude formed when millions of both plate and column crystals reflect light from their vertical faces. Short tails extend from each mock sun in the photo above.

A couple hours after the flying pig image, the sun was beyond 50 degrees altitude. The circumscribed halo had vanished! Credit: Bob King — About 2 hours after the flying pig image, the sun climbed beyond 50 degrees altitude. The circumscribed halo vanished! Credit: Bob King

There’s almost no end to atmospheric ice antics. Many are rare like the giant 46-degree halo or the 9 and 18-degree halos formed from pyramidal ice crystals. Oftentimes halos are accompanied by arcs or modified arcs as in the flying pig image. When the sun is low, you’ll occasionally see an arc shaped like a bird in flight tangent to the top of the halo and rarely, to its bottom. When the sun reaches an altitude of 29 degrees, these tangent arcs – both upper and lower – change shape and merge into a circumscribed halo wrapped around and overlapping the top and bottom of the main halo. At 50 degrees altitude and beyond, the circumscribed halo disappears … for a time. If the clouds persist, you can watch it return when the sun dips below 29 degrees and the two arcs separate again.

Maybe you’re not a halo watcher, but anyone who keeps an eye on the weather and studies the daytime sky in preparation for a night of skywatching can enjoy these icy appetizers.

May 13, 2014December 23, 2015 by David Dickinson

14 Red Dwarf Stars to View with Backyard Telescopes

An artist's conception of a red dwarf solar system. Credit: NASA/JPL-Caltech.

They’re nearby, they’re common and — at least in the latest exoplanet newsflashes hot off the cyber-press — they’re hot. We’re talking about red dwarf stars, those “salt of the galaxy” stars that litter the Milky Way. And while it’s true that there are more of “them” than there are of “us,” not a single one is bright enough to be seen with the naked eye from the skies of Earth.

A reader recently brought up an engaging discussion of what red dwarfs might be within reach of a backyard telescope, and thus this handy compilation was born.

Of course, red dwarfs are big news as possible hosts for life-bearing planets. Though the habitable zones around these stars would be very close in, these miserly stars will shine for trillions of years, giving evolution plenty of opportunity to do its thing. These stars are, however, tempestuous in nature, throwing out potentially planet sterilizing flares.

Red dwarf stars range from about 7.5% the mass of our Sun up to 50%. Our Sun is very nearly equivalent 1000 Jupiters in mass, thus the range of red dwarf stars runs right about from 75 to 500 Jupiter masses.

For this list, we considered red dwarf stars brighter than +10^th magnitude, with the single exception of 40 Eridani C as noted.

The closest stars within 14 light years of our solar system. Credit: Wikimedia Commons, Public Domain graphic.

I know what you’re thinking… what about the closest? At magnitude +11, Proxima Centauri in the Alpha Centauri triple star system 4.7 light years distant didn’t quite make the cut. Barnard’s Star (see below) is the closest in this regard. Interestingly, the brown dwarf pair Luhman 16 was discovered just last year at 6.6 light years distant.

Also, do not confuse red dwarfs with massive carbon stars. In fact, red dwarfs actually appear to have more of an orange hue visually! Still, with the wealth of artist’s conceptions (see above) out there, we’re probably stuck with the idea of crimson looking red dwarf stars for some time to come.

Star	Magnitude	Constellation	R.A.	Dec
Groombridge 34	+8/11(v)	Andromeda	00h 18’	+44 01’
40 Eridani C	+11	Eridanus	04h 15’	-07 39’
AX Microscopii/Lacaille 8760	+6.7	Microscopium	21h 17’	-38 52’
Barnard’s Star	+9.5	Ophiuchus	17h 58’	+04 42’
Kapteyn’s Star	+8.9	Pictor	05h 12’	-45 01’
Lalande 21185	+7.5	Ursa Major	11h 03’	+35 58’
Lacaille 9352	+7.3	Piscis Austrinus	23h 06’	-35 51’
Struve 2398	+9.0	Draco	18h 43’	+59 37’
Luyten’s Star	+9.9	Canis Minor	07h 27’	+05 14’
Gliese 687	+9.2	Draco	17h 36’	+68 20’
Gliese 674	+9.9	Ara	17h 29’	-46 54’
Gliese 412	+8.7	Ursa Major	11h 05’	+43 32’
AD Leonis	+9.3	Leo	10h 20’	+19 52’
Gliese 832	+8.7	Grus	21h 34’	-49 01’

Notes on each:

Groombridge 34: Located less than a degree from the +6th magnitude star 26 Andromedae in the general region of the famous galaxy M31, Groombridge 34 was discovered back in 1860 and has a large proper motion of 2.9″ arc seconds per year.

Locating Groombridge 34. Created using Stellarium.

40 Eridani C: Our sole exception to the “10^th magnitude or brighter” rule for this list, this multiple system is unique for containing a white dwarf, red dwarf and a main sequence K-type star all within range of a backyard telescope. In sci-fi mythos, 40 Eridani is also the host star for the planet Richese in Dune and the controversial location for Vulcan of Star Trek fame.

Locating 40 Eridani. Created using Stellarium.

AX Microscopii: Also known as Lacaille 8760, AX Microscopii is 12.9 light years distant and is the brightest red dwarf as seen from the Earth at just below naked eye visibility at magnitude +6.7.

A 20 year animation showing the proper motion of Barnard's Star. Credit: Steve Quirk, images in the Public Domain. — A 20 year animation showing the proper motion of Barnard’s Star. Credit: Steve Quirk, images in the Public Domain.

Barnard’s Star: the second closest star system to our solar system next to Alpha Centuari and the closest solitary red dwarf star at six light years distant, Barnard’s Star also exhibits the highest proper motion of any star at 10.3” arc seconds per year. The center of many controversial exoplanet claims in the 20^th century, it’s kind of a cosmic irony that in this era of 1790 exoplanets and counting, planets have yet to be discovered around Barnard’s Star!

Kapteyn’s Star: Discovered by Jacobus Kapteyn in 1898, this red dwarf orbits the galaxy in a retrograde motion and is the closest halo star to us at 12.76 light years distant.

Lalande 21185: currently 8.3 light years away, Lalande 21185 will pass 4.65 light years from Earth and be visible to the naked eye in just under 20,000 years.

Lacaille 9352: 10.7 light years distant, this was the first red dwarf star to have its angular diameter measured by the VLT interferometer in 2001.

Struve 2398: A binary flare star system consisting of two +9^th magnitude red dwarfs orbiting each other 56 astronomical units apart and 11.5 light years distant.

Luyten’s Star: 12.36 light years distant, this star is only 1.2 light years from the bright star Procyon, which would appear brighter than Venus for any planet orbiting Luyten’s Star.

Gliese 687: 15 light years distant, Gliese 687 is known to have a Neptune-mass planet in a 38 day orbit.

Gliese 674: Located 15 light years distant, ESO’s HARPS spectrograph detected a companion 12 times the mass of Jupiter that is either a high mass exoplanet or a low mass brown dwarf.

Gliese 412: 16 light years distant, this system also contains a +15^th magnitude secondary companion 190 Astronomical Units from its primary.

AD Leonis: A variable flare star in the constellation Leo about 16 light years distant.

Gliese 832: Located 16 light years distant, this star is known to have a 0.6x Jupiter mass exoplanet in a 3,416 day orbit.

The closest stars to our solar system over the next 80,000 years. Credit: FrancescoA under a Creative Commons Attribution Share-Alike 3.0 Unported license.

Consider this list a teaser, a telescopic appetizer for a curious class of often overlooked objects. Don’t see you fave on the list? Want to see more on individual objects, or similar lists of quasars, white dwarfs, etc in the range of backyard telescopes in the future? Let us know. And while it’s true that such stars may not have a splashy appearance in the eyepiece, part of the fun comes from knowing what you’re seeing. Some of these stars have a relatively high proper motion, and it would be an interesting challenge for a backyard astrophotographer to build an animation of this over a period of years. Hey, I’m just throwing that out project out there, we’ve got lots more in the files…

May 12, 2014December 23, 2015 by Bob King

Saturn Disappears Behind the Full Flower Moon May 14 – Watch it Live

Simulation of the moon closing in on Saturn just prior to occultation. Credit: Gianluca Masi using SkyX software

Funny thing. Skywatchers are often just as excited to watch a celestial object disappear as we are to see it make an appearance. Early Wednesday morning (May 14) the Full Flower Moon will slip in front of Saturn, covering it from view for about an hour for observers in Australia and New Zealand. If you don’t live where the dingoes roam, no worries. You can watch it online.And no matter where you are on the planet, the big moon will accompany the ringed planet across the sky this Tues. night-Weds. morning.

Moon-Saturn occultation from Perth, Australia Feb. 22, 2014 captured by Colin Legg

Occultations of stars happen swiftly. The moon’s limb meets the pinpoint star and bam! it’s gone in a flash. But Saturn is an extended object and the moon needs time to cover one end of the rings to the other. Planetary occultations afford the opportunity to remove yourself from planet Earth and watch a planet ‘set’ and ‘rise’ over the alien lunar landscape. Like seeing a Chesley Bonestell painting in the flesh.

Saturn and the moon tomorrow night just before midnight as viewed from the Midwestern U.S. View faces south-southeast. Stellarium — Saturn and the moon Tuesday night (May 13) just before midnight as viewed from the U.S. Stellarium

As the moon approaches Saturn, the planet first touches the lunar limb and then appears to ‘set’ as it’s covered by degrees. About an hour later, the planet ‘rises’ from the opposite limb. Planetary occultations are infrequent and always worth the effort to see.

Seen from the northern hemisphere and equatorial regions, the nearly full moon will appear several degrees to the right or west of Saturn tomorrow night (May 13). As the night deepens and the moon rolls westward, the two grow closer and closer. They’ll be only a degree apart (two full moon diameters) during Wednesday morning twilight seen from the West Coast. Northern hemisphere viewers will notice that the moon slides to the south of the planet overnight.

Map showing the region where the occultation of Saturn will be visible. Click to get the times of Saturn's disappearance and reappearance for individual cities. Times are given in UT or Universal Time. Add 9.5 hours for Australian Central Standard Time. Credit: IOTA — Map showing the region where the occultation of Saturn will be visible. Click to get times of Saturn’s disappearance and reappearance for individual cities. Times shown are UT or Universal Time. Add 9.5 hours for Australian Central Standard Time. Credit: IOTA

Skywatchers in Australia will see the moon cover Saturn during convenient early evening viewing hours May 14:

* 8:09 p.m. local time from Adelaide

* 9:05 p.m. Brisbane

* 8:50 p.m. Melbourne

* 8:53 p.m. Canberra

* 8:56 p.m. from Sydney (More times and a map – click HERE)

Before the occultation, Saturn will shine close to the moon’s upper right and might be tricky to see with the naked eye because of glare.

Binoculars will easily reveal the planet, but a telescope is the instrument of choice. Even a small scope magnifying at least 30x will show Saturn and its rings hovering above the bright edge of the moon. Stick around. About an hour later, Saturn will re-emerge along the moon’s lower left limb.

Saturn and its moons Tuesday night May 13 around 10 p.m. CDT. Titan's the brightest and easiest. Iapetus ranges from magnitude +10 when it's west of Saturn and we see its bright hemisphere to magnitude +12 when it's west of the planet as it will be this week. Created with Meridian software — Saturn and its moons Tuesday night May 13 around 10 p.m. CDT. Titan’s the brightest and easiest moon to see at magnitude +8.5. Iapetus ranges from magnitude +10 when it’s west of Saturn and we see its bright hemisphere to magnitude +12 when it’s east of the planet. Created with Meridian software

Meanwhile, back in the western hemisphere, we’ll watch the nearly full Flower Moon make a close pass of the planet. If you’ve had difficulty finding the celestial ring bearer, you’ll have no problem Tuesday night. Take a look at Saturn’s wonderful system of rings in your telescope – they’re tipped nearly wide open this year. For even more fun, see how many moons you can spot. And don’t forget, you can watch it online courtesy of astrophysicist Gianluca Masi. His Virtual Telescope website will broadcast the occultation live starting at 10:15 Universal Time May 14 (6:15 a.m. EDT, 5:15 CDT, 4:15 MDT and 3:15 PDT).

May 9, 2014December 23, 2015 by Bob King

Observing Alert: See Mercury’s Best Evening Show of the Year

Mercury starts its best period of visibility in the evening sky for skywatchers at mid-northern latitudes this weekend. This map shows the sky facing northwest about 40 minutes after sundown. Bright Jupiter also provides a convenient sightline for locating Mercury. Stellarium

Don’t let furtive Mercury slip through your fingers this spring. The next two and a half weeks will be the best time this year for observers north of the tropics to spot the sun-hugging planet. If you’ve never seen Mercury, you might be surprised how bright it can be. This is especially true early in its apparition when the planet looks like a miniature ‘full moon’.

Mercury, like Venus, displays phases as it revolves around the sun as seen from Earth's perspective outside Mercury's orbit. Credit: Bob King — Mercury, like Venus, displays phases as it revolves around the sun as seen from Earth’s perspective outside Mercury’s orbit. Both Mercury and Venus appear largest when nearly lined up between Earth and sun at inferior conjunction. Planets not to scale and phases shown are approximate. Credit: Bob King

Both Venus and Mercury pass through phases identical to those of the moon. When between us and the sun, Mercury’s a thin crescent, when off to one side, a ‘half-moon’ and when on the far side of the sun, a full moon. This apparition of the planet is excellent because Mercury’s path it steeply tilted to the horizon in mid-spring.

We start the weekend with Mercury nearly full and brighter than the star Arcturus. Twilight tempers its radiance, but :

* Find a location with a wide open view to the northwest as far down to the horizon as possible.

* Click HERE to get your sunset time and begin looking for the planet about 30-40 minutes after sunset in the direction of the sunset afterglow.

* Reach your arm out to the northwestern horizon and look a little more than one vertically-held fist (10-12 degrees) above it for a singular, star-like object. Found it? Congratulations – that’s Mercury!

* No luck? Start with binoculars instead and sweep the bright sunset glow until you find Mercury. Once you know exactly where to look, lower the binoculars from your eyes and you should see the planet without optical aid. And before I forget – be sure to focus the binoculars on a distant object like a cloud or the moon before beginning your sweeps. I guarantee you won’t find Mercury if it’s out of focus.

Through a telescope, Mercury looks like a gibbous moon right now but its phase will lessen as it moves farther to the ‘left’ or east of the sun. Greatest eastern elongation happens on May 24. On and around that date the planet will be farthest from the sun, standing 12-14 degrees high 40 minutes after sundown from most mid-northern locales.

jjjjjjj — Mercury is even better placed on May 19 but fades and begins to drop back down toward the horizon late in the month. Stellarium

The planet fades in late May and become difficult to see by early June. Inferior conjunction, when Mercury passes between the Earth and sun, occurs on June 19. Unlike Venus, which remains brilliant right up through its crescent phase, Mercury loses so much reflective surface area as a crescent that it fades to magnitude +3. Its greater distance from Earth, lack of reflective clouds and smaller size can’t compete with closer, brighter and bigger Venus.

Mercury's path across the solar disk as seen from the Solar and Heliospheric Observatory (SOHO) on November 8, 2006. The transit was visible in eastern Europe and the eastern hemisphere. Credit: NASA. — When a planet crosses the disk of the sun it’s called a transit. Mercury’s path across the solar disk is seen from the Solar and Heliospheric Observatory (SOHO) on November 8, 2006. Credit: NASA.

Mercury’s 7-degree inclined orbit means it typically glides well above or below the sun’s disk at inferior conjunction. But anywhere from 3 up to 13 years in either November or May the planet passes directly between the Earth and sun at inferior conjunction and we witness a transit. This last happened for U.S. observers on Nov. 8, 2006; the next transit occurs exactly two years from today on May 9, 2016. That event will be widely visible across the Americas, Western Europe and Africa. After having so much fun watching the June 2012 transit of Venus I can’t wait.

May 8, 2014December 23, 2015 by David Dickinson

Interesting Prospects for Comet A1 Siding Spring Versus the Martian Atmosphere

Inbound: the Hubble Space Telescope images Comet 2013 A1 Siding Spring with its Wide Field Camera 3. Credit: NASA.

It may be the chance of a lifetime for planetary science.

This October, a comet will brush past a planet, giving scientists a chance to study how it possibly interacts with a planetary atmosphere.

The comet is C/2013 A1 Siding Spring, and the planet in question Mars. And although an impact of the comet on the surface of the Red Planet has long been ruled out, a paper in the May 2014 issue of Icarus raises the interesting possibility of possible interactions of the coma of A1 Siding Spring and the tenuous atmosphere of Mars. The study comes out of the Department of Planetary Sciences at the University of Arizona, the Belgian Institute for Space Aeronomy, the Institut de Planétologie et d’Astrophysique de Grenoble at the Université J. Fourier in France, and the Cooperative Institute for Research in Environmental Sciences at the University of Colorado in Boulder.

For the study, researchers considered how active Comet A1 Siding Spring may be at the time of closest approach on October 19^th, 2014.

Discovered early last year by Robert McNaught from the Siding Spring Observatory in Australia, Comet A1 Siding Spring created a stir in the astronomical community when it was found that it will pass extremely close to Mars later this year. Further measurements of its orbit have since ruled this possibility out, but its passage will still be a close one, with a nominal passage of 138,000 kilometres from Mars. That’s about one third the distance from Earth to the Moon, and 17 times closer than the nearest recorded passage of a comet to the Earth, Comet D/1770 L1 Lexell in 1780. Mars’ outer moon Deimos has an orbital distance of about 23,500 kilometres.

The passage of Comet 2013 A1 Siding Spring through the inner solar system. Credit: NASA.

And although the nucleus will safely pass Mars, the brush with its extended atmosphere might just be detectable by the fleet of spacecraft and rovers in service around Mars. At a distance of 1.4 Astronomical Units (A.U.) from the Sun during the encounter, the vast coma is expected to be comprised primarily of H₂O. At an input angle of about 60 degrees, penetration was calculated in the study to impinge down and altitude of 154 kilometres to the topside of the Martian ionosphere, in the middle of the thermosphere.

Such an effect should linger for just over 4 hours, well over the interaction period of Mars’ atmosphere with the coma of just over an hour, centered on 18:30 UT on October 19^th, 2014.

What kind of views might missions like HiRISE and MSL get of the comet remains to be seen, although NEOWISE and Hubble are already monitoring the comet for enhanced activity. The Opportunity rover is also still functioning, and Mars Odyssey and ESA’s Mars Express are still in orbit around the Red Planet and sending back data. But perhaps the most interesting possibilities for observations of the event are still en route: India’s Mars Orbiter Mission and NASA’s MAVEN orbiter arrive just before the comet. MAVEN was designed to study the upper atmosphere of Mars, and carries an ion-neutral mass spectrometer (NGIMS) which could yield information on the interaction of the coma with the Martian upper atmosphere and ionosphere. The NGIMS cover is slated for release just two days before the comet encounter. All spacecraft orbiting Mars may feel the increased drag effects of the encounter.

A simulation of Mars as seen from Comet A1 Siding Spring on closest approach. Created by the author using Starry Night Software.

Proposals for using Earth-based assets for further observations of the comet prior to the event in October are still pending. Amateur observers will be able to follow the approach telescopically, as Comet A1 Siding Spring is expected to reach +8^th magnitude in October and pass 7’ from Mars in the constellation Ophiuchus as seen from the Earth. Mars just passed opposition last month, but both will be low to the south west at dusk for northern hemisphere observers in October.

It’s also interesting to consider the potential for interactions of the coma with the surfaces of the moons of Mars as well, though the net amount of water vapor expected to be deposited will not be large.

UPDATE: Check out this nifty interactive simulator which includes Comet A1 Siding Springs courtesy of the Solar System Scope:

The H₂O coma of A1 Siding Spring is expected to have a radius of 150,000 kilometres when it passes Mars, just a shade over the nominal flyby distance.

“There is a more extended coma made up of H₂O dissociation products (such as hydrogen and hydroxide) that extends for ~1,000,000 kilometres,” researcher at the Department of Planetary Sciences at the University of Arizona and lead author on the paper Roger Yelle told Universe Today.

“Essentially, Mars is in the outer reaches of the coma. The main ion tail misses Mars but there will be some ions from the comet that do reach Mars. The dust tail just misses Mars, which is fortunate.”

The paper also notes that significant perturbations of the upper atmosphere of Mars will occur if the cometary production rate is 10^28 s-1 or larger, which corresponds to about 300 kilograms per second.

“The MAVEN spacecraft will make very interesting observations,” Roger Yelle also told Universe Today. “The comet will perturb primarily the upper atmosphere of Mars and MAVEN was designed to study the upper atmosphere of Mars. Also, it’s just such an incredible coincidence that the comet arrives at Mars less than one month after MAVEN does. MAVEN is nominally in its checkout phase then, and the main science phase of the mission was not scheduled to start until November 1^st. However, we are reassessing our plans to see what observations we can make. It’s all quite exciting, and we have to balance safety and the desire to make the best science measurements.”

It’s an unprecedented opportunity, that’s for sure… all eyes will be on the planet Mars and Comet A1 Siding Spring on October the 19^th!

May 8, 2014December 23, 2015 by Bob King

Star Trail Photo Hints at Hidden Polestars

A 45-minute time exposure of the southern sky taken in early May shows trailed stars. The fat, bright streak is the planet Mars. Credit: Bob King

A week ago I made a 45-minute time exposure of the southern sky featuring the planet Mars. As the Earth rotated on its axis, the stars trailed across the sky. But take a closer look at the photo and you’ll see something interesting going on.

The trails across the diagonal (upper right to lower left) are straight, those in the top third arc upward or north while those in the bottom third curve downward or south.

I've drawn part of the imaginary great circle in the sky called the celestial equator. Residents of cities on or near the Earth's equator see the celestial equator pass directly overhead. From mid-northern latitudes, it's about halfway up in the southern sky. From mid-southern latitudes, it's halfway up in the northern sky. Credit: Bob King — I’ve drawn part of the imaginary great circle in the sky called the celestial equator. Residents of cities on or near the Earth’s equator see the celestial equator pass directly overhead. From mid-northern latitudes, it’s about halfway up in the southern sky. From mid-southern latitudes, it’s halfway up in the northern sky. Credit: Bob King

I suspect you know what’s happening here. Mars happens to lie near the celestial equator, an extension of Earth’s equator into the sky. The celestial equator traces a great circle around the celestial sphere much as the equator completely encircles the Earth.

On Earth, cities north of the equator are located in the northern hemisphere, south of the equator in the southern hemisphere. The same is true of the stars. Depending on their location with respect to the celestial equator they belong either to the northern or southern halves of the sky.

Earth's axis points north to Polaris, the northern hemisphere's North Star, and south to dim Sigma Octantis. Illustration: Bob King — Earth’s axis points north to Polaris, the northern hemisphere’s North Star, and south to dim Sigma Octantis. Illustration: Bob King

Next, let’s take a look at Earth’s axis and where each end points. If you live in the northern hemisphere, you know that the axis points north to the North Star or Polaris. As the Earth spins, Polaris appears fixed in the north while all the stars in the northern half of the sky describe a circle around it every 24 hours (one Earth spin). The closer a star is to Polaris, the tighter the circle it describes.

Time exposure centered on Polaris, the North Star. Notice that the closer stars are to Polaris, the smaller the circles they describe. Stars at the edge of the frame make much larger circles. Credit: Bob King

Likewise, from the southern hemisphere, all the southern stars circle about the south pole star, an obscure star named Sigma in the constellation of Octans, a type of navigational instrument. Again, as with Polaris, the closer a star lies to Sigma Octantis, the smaller its circle.

Stars trail around the dim southern pole star Sigma Octantis as seen from the southern hemisphere. The two smudges are the Large and Small Magellanic Clouds, companion galaxies of the Milky Way. Credit: Ted Dobosz

But what about stars on or near the celestial equator? These gems are the maximum distance of 90 degrees from either pole star just as Earth’s equator is 90 degrees from the north and south poles. They “tread the line” between both hemispheres and make circles so wide they appear not as arcs – as the other stars do in the photo – but as straight lines. And that’s why stars appear to be heading in three separate directions in the photograph.

A view of the entire sky as seen from Quito, Ecuador on the equator this evening. The celestial equator crosses directly overhead while each pole star lies 90 degrees away on opposite horizons. Stellarium

In so many ways, we see aspects of our own planet in the stars above.

May 8, 2014December 23, 2015 by Bob King

Asteroid 2013 UQ4 Suddenly Becomes a Dark Comet with a Bright Future

Comet C/2013 UQ4, once thought to be an asteroid, now shows characteristics of a comet including a coma. This photo was made on May 7, 2014. Credit: Artyom Novichonok and Taras Prystavski

On October 23, 2013, astronomers with the Catalina Sky Survey picked up a very faint asteroid with an unusual orbit more like a that of a comet than an asteroid. At the time 2013 UQ4 was little more than a stellar point with no evidence of a hazy coma or tail that would tag it as a comet. But when it recently reappeared in the morning sky after a late January conjunction with the sun, amateur astronomers got a surprise.

On May 7, Comet ISON co-discoverer Artyom Novichonok, and Taras Prystavski used a remote telescope located in Siding Spring, Australia to take photos of 2013 UQ4 shortly before dawn in the constellation Cetus. Surprise, surprise. The asteroid had grown a little fuzz, making the move to comethood. No longer a starlike object, 2013 UQ4 now displays a substantial coma or atmosphere about 1.5 arc minutes across with a more compact inner coma measuring 25 arc seconds in diameter. No tail is visible yet, and while its overall magnitude of +13.5 won’t make you break out the bottle of champagne, it’s still bright enough to see in a 12-inch telescope under dark skies.

Wide field map showing the comet's movement from Cetus through Pisces and into Cepheus in July when it becomes circumpolar for skywatchers at mid-northern latitudes. It should reach peak brightness of 7th magnitude in early July. Created with Chris Marriott's SkyMap program — Wide field map showing the comet’s movement from Cetus through Pisces and into Cepheus in July when it becomes circumpolar for skywatchers at mid-northern latitudes. It should reach a peak brightness of 7th magnitude in early July. Click to enlarge. Created with Chris Marriott’s SkyMap program

The best is yet to come. Assuming the now renamed C/2013 UQ4 continues to spout dust and water vapor, it should brighten to magnitude +11 by month’s end as it moves northward across Pisces and into a dark morning sky. Perihelion occurs on June 5 with the comet reaching magnitude +8-9 by month’s end. Peak brightness of 7th magnitude is expected during its close approach of Earth on July 10 at 29 million miles (46.7 million km).

This should be a great summer comet, plainly visible in binoculars from a dark sky as it speeds across Cepheus and Draco during convenient viewing hours at the rate of some 7 degrees per night! That’s 1/3 of a degree per hour or fast enough to see movement through a telescope in a matter of minutes when the comet is nearest Earth.

Lightcurve showing the date on the bottom and magnitude along the vertical. Work by Artyom Novichonok and Taras Prystavski — Light curve showing C/2013 UQ4 brightening to a sharp peak in early July and then quickly fading. Created by Artyom Novichonok and Taras Prystavski

Come August, C/2013 UQ4 rapidly fades to magnitude +10 and then goes the way of so many comets – a return to a more sedentary lifestyle in the cold bones of deep space.

C/2013 UQ4 belongs to a special category of asteroids called damocloids (named for asteroid 5335 Damocles) that have orbits resembling the Halley-family comets with long periods, fairly steep inclinations and highly eccentric orbits (elongated shapes). Some, like Comet Halley itself, even travel backwards as they orbit the sun, an orbit astronomers describe as ‘retrograde’.

Evolution of a comet as it orbits the sun. Credit: Laboratory for Atmospheric and Space Sciences/ NASA

Damocloids are thought to be comets that have lost all their fizz. With their volatile ices spent from previous trips around the sun, they stop growing comas and tails and appear identical to asteroids. Occasionally, one comes back to life. It’s happened in at least four other cases and appears to be happening with C/2013 UQ4 as well.

Studies of the comet/asteroid’s light indicate that UQ4 is a very dark but rather large object some 4-9 miles (7-15 km) across. It’s estimated that C/2013 UQ4 takes at least 500 years to make one spin around the sun. Count yourself lucky this damocloid decided to spend its summer vacation in Earth’s skies. We’ll have more detailed maps and updates as the comet becomes more easily visible next month. Stay tuned.