David Dickinson, Author at Universe Today

October 9, 2013December 23, 2015 by David Dickinson

New Data: Will Comet ISON Survive its Close Perihelion Passage?

An analysis of the dust coma of comet ISON showing the evaporation of ice particles. (Credit: NASA/ESA J.-Y. Li (Planetary Science Institute and the Hubble ISON Imaging Science Team).

It’s the question on every astronomer’s mind this season, both backyard and professional: will Comet C/2012 S1 ISON survive perihelion?

Now, new studies released today at the American Astronomical Society’s 45^th Annual Division for Planetary Sciences meeting being held this week in Denver suggests that ISON may have the “right stuff” to make it through its close perihelion passage near the Sun. This is good news, as Comet ISON is expected to be the most active and put on its best showing post-perihelion… if it survives.

Researchers Matthew Knight of the Lowell Observatory and Research Scientist Jian-Yang Li of the Planetary Science Institute both presented a compelling portrait of the characteristics and unique opportunities presented by the approach of comet ISON to the inner solar system.

Jian-Yang Li studied ISON earlier this year using Hubble before it passed behind the Sun from our Earthly vantage point. Li and researchers were able to infer the position and existence of a jet coming from the nucleus of the comet, which most likely marks the position of one of its rotational poles.

“We measured the rotational pole of the nucleus,” Li noted in a press release from the Planetary Science Institute. The pole indicates that only one side of the comet is being heating by the Sun on its way in until approximately one week before it reaches its closest point to the Sun.”

Could we be in for a “surge” of activity from ISON coming from around November 20^th on?

Comet ISON as imaged from Aguadilla, (sp) Puerto Rico recently on october 6th. (Credit: Efrain Morales Rivera). — Comet ISON as imaged from Aguadilla, Puerto Rico recently on October 6th. (Credit: Efrain Morales Rivera).

Li also noted that the reddish color of the coma of ISON suggests an already active comet sublimating water ice grains as they move away from the nucleus. He also noted that time has been allocated to observe ISON using Hubble this week.

Next up, researcher Mathew Knight presented some encouraging news for ISON when it comes to surviving perihelion.

The findings were a result of numerical simulations carried out by Kevin Walsh and Knight, combined with a historical analysis of previous sun-grazing comets. Both suggest that comet nuclei smaller than 200 metres in diameter, with an average density or lower (for comets, that is) typically do not survive a close passage to the Sun.

Both researchers place the size of ISON’s nucleus in the range of 0.5 to 2 kilometres, comfortably above the 0.2 kilometre “shred limit” for its relative perihelion distance. ISON is not a technically Kreutz group sungrazer, though studies of the over 2,000 known Kreutz comets historically observed provide an interesting guideline for what might be in store for ISON. Four Kreutz comets, including C/2011 W3 Lovejoy and Comet C/1887 B1 partially survived perihelion to become “headless wonders,” while five, including Comet C/1965 S1 Ikeya-Seki — which ISON is often compared to — survived perihelion passage to become one of the great comets of the 20^th century.

ISON will pass inside the Roche limit of the Sun, which is a distance of 2.4 million kilometres (for fluid bodies) and will be subject to temperatures approaching 5,000 degrees Fahrenheit on closest approach.

ISON is a first time visitor to the inner solar system. Discovered on September 21^st, 2012 by Russian researchers Artyom Novichonok and Vitaly Nevsky participating in the International Scientific Optical Network, ISON will pass less than 1.2 million kilometres above the surface of the Sun on November 28^th, 2013.

One interesting but little discussed factor highlighted in today’s press release was the retrograde versus prograde rotation of the cometary nucleus. A fast, prograde spin of an elongated nucleus may spell doom for ISON, as tidal forces will rip it apart. A retrograde rotator, however, is very likely to survive the encounter.

Thus far, there are no solid indications that ISON is indeed a retrograde rotator, although there are tantalizing hints that beg for further observations.

Li notes that it’s tough to infer a bias for comets like ISON to be retrograde over prograde rotators, as we’ve only got five historical comets to go by similar to ISON, and the breakdown is thus about 50/50 for and against.

ISON’s possible survival would validate both studies and their methods and give us more refined predictions for future comets.

“We’ve never discovered a sungrazer this far out,” Knight told Universe Today. “The rotation of ISON depends on the pole position (from Li’s study) and in theory, if we could get enough images, a proper morphology (for ISON) would emerge.”

Comet ISON imaged on October 5th from Long Beach, California. (Credit: Thad Szabo @AstroThad).

The implications of this analysis is certainly good news for observers. If ISON survives perihelion, we would then have a brilliant dawn Christmas comet unfurling its tail off to the northeast in early December.

Of course, these findings are contrary to early cries of its demise, including the paper out of the Institute of Physics that has been circulating touting “The Impending Demise of ISON”. Read Universe Today editor Nancy Atkinson’s excellent synopsis on that, it’s a tale that just won’t seem to die.

And we’ve also done our skeptic’s duty of thoroughly debunking the mounting ISON lunacy, including its status as the harbinger for the “end of the world of the week,” as well as its inability to fulfill prophecy. But if we get a surge in ISON next month as researchers suggest, we fully expect the accompanying hype to crest as well.

The most recent observations put ISON at about +10^th magnitude as it currently crosses the constellation Leo, near Mars and Regulus in the morning sky. We recently did an observing post tracking its plunge to perihelion in late November, and we’ve been diligently hunting for ISON with binoculars every morning pre-dawn.

We’re glad to have some positive science to report on for ISON. Things are looking up for a fine show come early December!

-Read the PSI press release on JianYang Li’s findings as well as the original paper on ISON’s survival prospects by Matthew Knight.

October 8, 2013December 23, 2015 by David Dickinson

A Tale of a Lost Moon: Hubble Spies Neptune’s Moons and Its Rings

Neptune's system of moons and rings visualized. Credit: SETI

“That’s no moon…”

-B. Kenobi

But in this case, it is… a lost moon of Neptune not seen since its discovery in the late 1980’s.

A new announcement from the 45^th Meeting of the Division for Planetary Sciences of the American Astronomical Society being held this week in Denver, Colorado revealed the recovery of a moon of Neptune that was only briefly glimpsed during the 1989 flyby of Voyager 2.

The re-discovery Naiad, the innermost moon of Neptune, was done by applying new processing techniques to archival Hubble images and was announced today by Mark Showalter of the SETI institute.

Collaborators on the project included Robert French, also from the SETI Institute, Dr. Imke de Pater of UC Berkeley, and Dr. Jack Lissauer of the NASA Ames Research Center.

The findings were a tour-de-force of new techniques applied to old imagery, and combined the ground-based 10 meter Keck telescope in Hawaii as well as Hubble imagery stretching back to December 2004.

The chief difficulty in recovering the diminutive moon was its relative faintness and proximity to the “dazzling” disk of Neptune. At roughly 100 kilometres in diameter and an apparent magnitude of +23.9, Naiad is over a million times fainter than +8th magnitude Neptune. It’s also the innermost of Neptune’s 14 known moons, and orbits once every 7 hours just 23,500 kilometres above the planet’s cloud tops. Neptune itself is about 49,000 kilometres in diameter, and only appears 2.3” in size from Earth. From our Earthly vantage point, Naiad only strays about arc second from the disk of Neptune, a tiny separation.

“Naiad has been an elusive target ever since Voyager left the Neptune system,” Showalter said in a recent SETI Institute press release. Voyager 2 has, to date, been the only mission to explore Uranus and Neptune.

To catch sight of the elusive inner moon, Showalter and team applied new analyzing techniques which filtered for glare and image artifacts that tend to “spill over” from behind the artificially occulted disk of Neptune.

Other moons, such as Galatea and Thalassa — which were also discovered during the 1989 Voyager 2 flyby — are also seen in the new images. In fact, the technique was also used to uncover the as of yet unnamed moon of Neptune, S/2004 N1 which was revealed earlier this year.

Naiad is named after the band of nymphs in Greek mythology who inhabited freshwater streams and ponds. The Naiads differed from the saltwater-loving Nereids of mythology fame, after which another moon of Neptune discovered by Gerard Kuiper in 1949 was named.

It’s also intriguing to note that Naiad was discovered in a significantly different position in its orbit than expected. Clearly, its motion is complex due to its interactions with Neptune’s other moons.

“We don’t quite have enough observations to establish a refined orbit,” Mr. Showalter told Universe Today, noting that there may still be some tantalizing clues waiting to be uncovered from the data.

I know the burning question you have, and we had as well during the initial announcement today. Is it REALLY Naiad, or another unknown moon? Showalter notes that this possibility is unlikely, as both objects seen in the Hubble and Voyager data are the same brightness and moving in the same orbit. To invoke Occam’s razor, the simplest solution— that both sightings are one in the same object —is the most likely.

“Naiad is well inside Neptune’s Roche Limit, like many moons in the solar system,” Mr. Showalter also told Universe Today. Naiad is also well below synchronous orbit, and is likely subject to tidal deceleration and may one day become a shiny new ring about the planet.

The labeled ring arcs of Neptune as seen in newly processed data. The image spans 26 exposures combined into a equivalent 95 minute exposure, and the ring trace and an image of the occulted planet Neptune is added for reference. (Credit: M. Showalter/SETI Institute). — The labeled ring arcs of Neptune as seen in newly processed data. The image spans 26 exposures combined into an equivalent 95 minute exposure. The ring trace and an image of the occulted planet Neptune is added for reference. (Credit: M. Showalter/SETI Institute).

And speaking of which, the tenuous rings of Neptune have also evolved noticeably since the 1989 Voyager flyby. First discovered from the ESO La Silla Observatory in 1984, data using the new techniques show that the knotted ring segments named the Adams and Le Verrier have been fading noticeably.

“In a decade or two, we may see an ‘arc-less’ ring,” Showalter noted during today’s Division for Planetary Sciences press conference. The two ring segments observed are named after Urbain Le Verrier and John Couch Adams, who both calculated the position of Neptune due to orbital perturbations of the position of Uranus. Le Verrier beat Adams to the punch, and Neptune was first sighted from the Berlin Observatory on the night of September 23^rd, 1846. Observers of the day were lucky that both planets had undergone a close passage just decades prior, or Neptune may have gone unnoticed for considerably longer.

The rings of Neptune as seen from Voyager 2 during the 1989 flyby. (Credit: NASA/JPL).

Neptune has completed just over one 164.8 year orbit since its discovery. It also just passed opposition this summer, and is currently a fine telescopic object in the constellation Aquarius.

Unfortunately, there aren’t any plans for a dedicated Neptune mission in the future. New Horizons will cross the orbit of Neptune in August 2014, though it’s headed in the direction of Pluto, which is currently in northern Sagittarius. New Horizons was launched in early 2006, which gives you some idea of just how long a “Neptune Orbiter” would take to reach the outermost ice giant, given today’s technology.

This represents the first time that Naiad has been imaged from the vicinity of Earth, and demonstrates a new processing technique capable of revealing new objects in old Hubble data.

“We keep discovering new ways to push the limit of what information can be gleaned from Hubble’s vast collection of planetary images,” Showalter said in the SETI press release.

Congrats to Showalter and team on the exciting recovery… what other moons, both old and new, lurk in the archives waiting to be uncovered?

– Read today’s SETI Institute press release on the recovery of Naiad.

-Be sure to follow all the action at the 45th DPS conference in Denver this week!

October 8, 2013December 23, 2015 by David Dickinson

A Fine Pair of Lunar Occultations for North America This Weekend

Pi Sagittarii moments before it was occulted by the Moon on August 10th, 2011. (Photo by Author).

Heads up, North American residents: our Moon is about to blot out two naked eye stars on Friday and Saturday night.

Such an event is known as an occultation, an astronomical term that has its hoary roots in astronomy’s pseudoscience ancestor of astrology. An occultation is simply when one astronomical body passes in front of another from our line of sight. There’s nothing quite like watching a star disappear on the dark limb of the Moon. In a universe where events often transpire over periods of time longer than a human life span, occultations are abrupt affairs to witness.

Close double stars have also been teased out of occultation data, winking out in a quick, step-wise fashion. If an occultation such as the two this weekend occurs while the Moon is waxing towards Full, we get the added advantage of watching the action on the leading dark limb of the Moon during convenient early evening hours.

Beta Capricorni on the dark limb of the Moon Saturday night. (Created by the author using Starry Night).

First up is the occultation of the +3.9^th magnitude star Rho Sagittarii on Friday night, October 11^th. Central conjunction for this occultation occurs at 00:40 Universal Time (UT) early on the morning of the 12^th. The Moon will be at a 51% illuminated waxing gibbous phase, having passed First Quarter just prior to the start of the occultation at 7:02 PM EDT/23:02 UT on the 11^th. The sunset terminator line at the start of the occultation will bisect the central U.S., and observers east of the Mississippi will get to witness the entire event. The southern graze line will cross Cuba and Guatemala. Note that the Moon will also pass its most southern declination for this lunation just two days prior on October 9^th at 23:00 UT/7:00 PM EDT, at a declination of -19.6 degrees. This is one of the Moon’s most southern journeys for 2013, meaning that it will still ride fairly far to the south in the sky during this weekend’s occultations.

The occultation of Rho Saggitarii by the Moon for the night of October 11th. (rendered using Occult 4.1.02 software). — The occultation of Rho Sagittarii by the Moon for the night of October 11th. the dashed line indicates where the occultation will occur in the daytime; east of this region, the occultation occurs after sunset. (rendered using Occult 4.1.02 software).

Rho Sagittarii is an F-type star 122 light years distant. Stick around until February 23^rd, 2046, and you’ll get to see an even rarer treat, when the planet Venus occults the very same star. Just south of the Rho Sagittarii pair lies the region from which the Wow! Signal was detected in 1977.

The Moon moves at an average speed of just over a kilometre a second in its orbit about the Earth, and traverses roughly the apparent distance of its angular size of 30’ in one hour. The duration of occultations as seen from their center line take about an hour from ingress to egress, though its much tougher to watch a star reappear on the bright limb of the Moon!

And the night of Saturday, October 12^th finds the 62% illuminated waxing gibbous Moon occulting an even brighter star across roughly the same region. The star is +3.1 magnitude Beta Capricorni, which also goes by the Arabic name of Dabih, meaning “the butcher.” Dabih is also an interesting double star with a +6^th magnitude component 3.5’ away from the +3^rd magnitude primary. Dabih is an easy split with binoculars, and it will be fun to watch the two components pass behind the Moon Saturday night. This occultation also occurs the night of October 12^th which is traditionally Fall Astronomy Day. If you’re hosting a star party this coming Saturday night, be sure to catch the well-timed occultation of Beta Capricorni! The central conjunction for this event occurs at 01:27 UT on the morning of the 13^th, and North American observers east of the Rockies will get to see the entire event.

The occultation footprint of Beta Capricorni for the night of October 12th. (Rendered using Occult 4.1.0.2 software).

Beta Capricorni is 328 light years distant, putting the physical separation of the B component at about a third of a light year away from the primary star at 21,000 astronomical units distant. “Beta B” thus takes about 700,000 years to orbit its primary! It’s also amazing to think that those fusion-born photons took over three centuries to get here, only to be rudely “interrupted” by the bulk of our Moon in the very last second of their journey.

And be sure to keep an eye on the primary star as it winks out, as it’s a known spectroscopic triple star with unseen companions in respective 9 and 1374 day orbits. Dabih may just appear to “hang” on the jagged lunar limb as those close companions wink out in a step-wise fashion.

Both occultations are bright enough to watch with the naked eye, although a standard set of 10x 50 binoculars will provide a fine view. The ingress of an occultation is also an excellent event to catch on video, and if you’ve got WWV radio running audio in the background, you can catch the precise time that the star disappears from your locale.

Note: WWV radio is still indeed broadcasting through the ongoing U.S. government shutdown, though they’re operated by NOAA & the NIST.

The International Occultation and Timing Association is always interested in reports of occultations carried out by amateur astronomers. Not only can this reveal or refine knowledge of close double stars, but a series of occultation observations from precisely known locations can map the profile of the lunar limb.

Be sure to catch both events this U.S. Columbus Day/Canadian Thanksgiving Day weekend, and send those pics in to Universe Today!

Precise timings for the ingress and egress of each lunar occultations for major North American cities can be found at the following pages:

– Rho Sagittarii

– Beta Capricorni

October 3, 2013December 23, 2015 by David Dickinson

Is Iran REALLY Planning on Sending a Cat Into Space?

“I’m going where?”

No, this isn’t The Onion… as a concerned consumer of all that is space news, you have indeed arrived at the cyber-doorstep of Universe Today.

I’ll admit though, that we did do a double take about a week back when a peculiar claim came our way via the Iranian Space Agency. Yes, there is an Iranian Space Agency, and it’s kind of frightening that they remain open for business while NASA is largely shutdown.

In mid-September, senior Iranian space program official Mohammad Ebrahimi issued a statement that Iran will attempt another bio-capsule launch “within 45 days”. The unwilling occupant: a Persian cat.

Apparently, a rabbit, a mouse, and another “Space Monkey” were also in the running. Iran’s space program is shrouded in secrecy, and most launches are only announced after they’ve been conducted. This is a convenient political strategy for hiding launch failures that harkens back to the early days of the Cold War. You’re right in guessing that the Iranian Space Agency probably won’t hold a Tweetup for this one. Many western analysts see the Iran’s space effort as a thinly veiled attempt to develop its long range ballistic missile technology. Along with Israel, Iran remains the only Middle Eastern country with the proven technology to conduct indigenous satellite launches.

Iran has stated that it hopes to put an astronaut in orbit by 2019. The Pishgam (or “Pioneer” in Farsi) 2 bio-capsule launch could occur from a mobile launcher at Semnan Space Center as early as October 15^th. Satellite sleuths are also expecting activity at Semnan to pick up this month, with the possible launch of SharifSat atop a Safir 1-B rocket, and Iran’s Toulou satellite aboard a rumored new launch vehicle.

Iran successfully became a space-faring nation with the launch of its 27 kilogram Omid satellite on February 2^nd, 2009. It isn’t immediately clear if the upcoming launch will be an orbital launch or a sub-orbital ballistic shot. If Pisgam-2 achieves orbit, said “Space Cat” would become the first feline to circle the Earth. If recovery is attempted —again, Iran is always nebulous as to their intentions— it would also be the first time they’ve achieved a return from orbit.

But is “Space Cat” even a reality?

Iran has been caught red-handed before playing a shell game with the media in terms of its space program. Earlier this year, “Monkey-gate” erupted, as before-and-after images from the Pisgam-1 bio-capsule suborbital launch clearly showed two different monkeys before and after the flight:

Monkey business? Iran displayed a decidedly different looking monkey before, during, and after launch earlier this year! (Credit: Iran News Agency).

Clearly, Iran and other ‘Axis of Evil’ countries definitely need to sharpen their Photoshop, or at least their monkey-switching skills. Either said monkey launch never actually occurred, or (more likely), the unwilling Iranian space primate never survived the flight.

Perhaps this is why Iran decided on a feline occupant this time around, for possible ease of replacement?

PETA, the People for the Ethical Treatment of Animals, have also issued a statement concerning the impending launch of “Space Cat” by Iran, calling the action an “archaic experiment, a throwback to the primitive techniques of the 1950’s.”

NASA did entertain the idea of "Catronauts" early in the space program. (Credit: NASA). — NASA did entertain the idea of “Catronauts” early in the space program. (Credit: NASA).

The U.S. and the Soviet Union launched animals into space as a prelude to human spaceflight. On November 3^rd, 1957, Laika the dog became the first animal to orbit the Earth. Laika perished is space due to overheating, as did several unfortunate monkeys that were launched on the first US ballistic tests.

Russia still conducts the occasional launch of animals into space, including the Bion-1M “Space Zoo” mission earlier this year. The Bion missions allow for scientists to dissect the specimens afterwards to study the effects of a month in zero-g, something you can’t do with humans.

And the U.S. did once fly cats in zero-g aboard its Convair C-131 “Vomit Comet” aircraft, as can be seen in this bizarre video:

But the first cat in space was actually launched by France atop a Veronique AGI sub-orbital rocket 50 years ago this month on October 18^th, 1963. It would be ironic if Iran conducted it launch this month on the anniversary! The story goes the Felix, the original cat slated for the flight, escaped just prior to launch from the Sahara desert Hammaguir test site in Algeria, and was replaced by the “backup crew,” a female cat named Felicette. Felicette survived the 15 minute flight, reaching an apogee of 217 kilometres. A follow-up launch of a second cat six days later wasn’t so lucky.

Felicette (left) and Felix in publicity shots prior to launch. Note the cranial electrode (!) implants. (Credit: Marjorie-art Voila.net)

As always, Iran’s intentions for the future of its space program remain hidden. Their current launch capabilities remain limited, and are a far cry from being able to hoist a human into orbit anytime soon. If the launch of “Space Cat” does come to pass this month, it’ll be over protests from animal rights groups and the general public. Hey, didn’t the former Iranian president Mahmoud Ahmadinejad say earlier this year after “Monkey-Gate” that he was willing to be “The first Iranian to be sacrificed by the scientists of my country and go into space” as the first Iranian astronaut? Is he really going to let Space Cat upstage him?

Felix and Felicette where also commemorated on several African postage stamps. (Credit: Majorie-art.voila.net).

–Read a great synopsis of the history of felines in space from Heather Archulletta @Pillownaut.

October 1, 2013December 23, 2015 by David Dickinson

Uranus: A Guide to its 2013 Opposition

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 4^th 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 3^rd 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.

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!

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:

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 11^th, 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 30^th. 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!

September 26, 2013December 23, 2015 by David Dickinson

Bazinga: Mysterious Earth Orbiting Asteroid Turns Out to be Space Junk

The launch of Chan'ge-2 with 3rd stage (arrowed) now known as 2010 Q (Credit CALT).

Can’t find asteroid 2010 QW1 in the Minor Planet Database? No, the “Men in Black” didn’t secretly remove this Earth-orbiting asteroid from the listing… but recent top-notch detective work by astronomers did.

The mystery of this object all started back on August 23^rd of this year, when the PanSTARRS sky survey based on the summit of Haleakala on the island of Maui in Hawai’i spotted an asteroid that was given the provisional designation of 2013 QW1.

The object was in a wide-ranging orbit around the Earth, leading astronomers to wonder if it was a naturally captured asteroid or perhaps space debris from a previous launch. Either solution to the dilemma would be fascinating. Our large Moon keeps the Earth pretty well swept clear of debris, though a “second Moon,” however small, would be an interesting find. And if 2013 QW1 were to prove artificial, it just might be a piece of history.

The European Space Agency’s NEO Coordination Centre decided to take up the challenge. A call went out to track and observe the 2013 QW1, and a team led by Elisabetta Dotto of INAF-Observatorio di Roma & Maria Barucci & Davide Perna of the Observatoire de Paris managed to get time on the Italian Telescopio Nazaionale Galileo based at La Palma to obtain a spectrum of the object.

“It was a bit of a challenge, because the object was moving fast with respect to a typical NEO,” said Dr. Perna in a recent ESA press release.

The team used an instrument known as DOLORES to make the crucial measurements. DOLORES stands for the Device Optimized for LOw RESolution. The spectrum obtained in the early morning hours of August 25^th shows something much brighter than your typical asteroid, but is characteristic of a painted metallic object.

And thus, 2013 QW1 was removed from the ledger of NEO asteroids maintained by the IAU Minor Planet Center (MPEC). And the leading suspect? The third stage booster of a Chinese Long March 3C rocket that launched the Chang’e 2 spacecraft from Xichang, China on October 1^st, 2010.

Chang’e-2 entered lunar orbit 8 days after launch, and departed on June 8^th of the following year after studying and mapping the Moon. Chang’e-2 then went on to become the first spacecraft to directly reach the L2 Lagrange point 1.5 million kilometres beyond Earth from lunar orbit. The spacecraft also made the first flyby of NEO asteroid 4179 Toutatis on December 13^th of last year. The probe is estimated to continue functioning into 2014, and will be used to hone China’s ability to track objects in deep space.

The NORAD tracking identification assigned to the 3^rd stage booster that launched Chan’ge-2 is 2010-50B.

This sort of discovery is not without precedent.

The launch of Apollo 12, with the 2nd stage arrowed. (Credit: NASA). — The launch of Apollo 12, with the 3rd stage (arrowed) would one day be “asteroid Joo2E3”. (Credit: NASA).

On September 3^rd, 2002, amateur astronomer Bill Yeung discovered an asteroid tentatively designated J002E3. Subsequent studies revealed that the asteroid had a spectrum consistent with that of titanium oxide paint, a decidedly unasteroid-like coating for a space rock to sport. This was, however, a common veneer in use during the Apollo era, and it is now known that J002E3 is the S-IVB third stage booster that launched the second mission to land men on the Moon on November 14^th, 1969. Unlike other boosters, such as the one that launched Apollo 14, the Apollo 12 3^rd stage did not impact the Moon as part of seismic experiments. After a brief period as a “pseudo-moon” of the Earth, J002E3 was kicked out into solar orbit in June 2003 and may return to our neighborhood once again in the 2040s.

NASA’s Lunar Reconnaissance Orbiter has documented the lunar crash sites of these historic boosters. It’s of note that the Apollo 10 Lunar Module Snoopy remains discarded out in solar orbit as well, having been used as a dress rehearsal for the historic Apollo 11 landing. Apollo 10 never landed on the Moon. Efforts have been made by UK astronomer Nick Howes to recover it as well.

And there are more relics of the Space Age awaiting discovery. One of the first things we always check in the case of a pass by a newly discovered NEO closer than the Moon to the Earth is its history, to see if it matches up with any launches headed out beyond Earth orbit in the past.

And the upcoming Mars launches of MAVEN and India’s Mars Orbiter Mission in October & November will be the first to depart Earth orbit since 2011. These will give future generations of asteroid hunters new human-made space hardware to ponder.

The B612 Foundation’s asteroid-hunting Sentinel Space Telescope will also “up the game,” scouting for asteroids from a vantage point interior to the Earth’s orbit. Sentinel is slated for launch in 2016 atop a SpaceX Falcon 9 rocket.

And no, the fabled “Black Knight” satellite of UFO conspiracy buffs’ dreams is nowhere to be found.

What other fascinating relics of the Space Age lie are out there in the solar system, waiting to tell their tale?

September 23, 2013December 23, 2015 by David Dickinson

Comet ISON: A Viewing Guide from Now to Perihelion

Comet ISON, as seen on September 22, 2013 at 10:00 UTC (6:00 am EDT) from Yellow Springs, Ohio, using a QHY8 CCD camera and a home-made 16 inch diameter telescope. 15 minute exposure. Credit and copyright: John Chumack.

Perhaps you’ve read the news. This Fall, the big ticket show is the approach of Comet C/2012 S1 ISON. The passage of this comet into the inner solar system has been the most anticipated apparition of a comet since Hale-Bopp in 1997.

Many backyard observers will get their first good look at Comet ISON in the coming month. If you want to see this comet for yourself, here’s everything you’ll need to know!

A composite image of Comet ISON as seen from the Hubble Space Telescope on April 30th, 2013. (Credit: HubbleSite.org/Go/ISON).

Discovered on September 21^st, 2012 by Artyom-Kislovodsk and Vitaly Nevsky using the International Scientific Optical Network’s (ISON) 0.4 metre reflector, this comet has just passed out from behind the Sun from our Earthly vantage point this summer to once again become visible in the dawn sky.

Of course, there’s much speculation as to whether this will be the “comet of the century” shining as “bright as the Full Moon” near perihelion. We caught up with veteran comet observer John Bortle earlier this year to see what skywatchers might expect from this comet in late 2013. We’ve also chronicled the online wackiness of comets past and present as ISON makes its way into the pantheon as the most recently fashionable scapegoat for “the end of the world of the week…”

But now it’s time to look at the astronomical prospects for observing Comet ISON, and what you can expect leading up to perihelion on November 28^th.

Comet ISON imaged by Efrain Morales on September 22nd. (Credit: Efrain Morales/Jaicoa Observatory, used with permission). — Comet ISON as recently imaged by Efrain Morales on September 22nd. (Credit: Efrain Morales/Jaicoa Observatory, used with permission).

Advanced amateur astronomers are already getting good images of Comet ISON, which currently shines at around +12^th magnitude in the constellation Cancer. And although NASA’s Deep Impact/EPOXI mission is down for the count, plans are afoot for the Curiosity rover and the Mars Reconnaissance Orbiter to attempt imaging the comet when it makes its closest approach to the Red Planet on October 1^st at 0.0724 Astronomical Units (A.U.) or 10,830,000 kilometres distant. If MSL is successful, it would be the first time that a comet has been observed from the surface of another world.

Currently, ISON sits about a magnitude below the projected light curve, (see below) but that isn’t all that unusual for a comet. Already, there’s been increasing talk of “ISON being a dud,” but as Universe Today’s Nancy Atkinson pointed out in a recent post, these assertions are still premature. The big question is what ISON will do leading up to perihelion, and if it will survive its passage 1.1 million kilometres above the surface of the Sun on November 28^th to become a fine comet in the dawn skies in the weeks leading up to Christmas.

ISON is already starting to show a short, spikey tail in amateur images. Tsutomu Seki estimated it to be shining at about magnitude +11.1 on September 16th. Keep in mind, a caveat is in order when talking about the magnitudes of comets. Unlike stars, which are essentially a point source, the brightness of a comet is spread out over a large surface area. Thus, a comet may appear visually fainter than the quoted magnitude, much like a diffuse nebula. Although +6^th magnitude is usually the limit for naked eye visibility, I’ll bet that most folks won’t pick up ISON with the unaided eye from typical suburban sites until it breaks +4^th magnitude or so.

(Credit: NASA CIOC/Matthew Knight. used with permission). — The recent revised light curve projected for Comet ISON (Credit: NASA CIOC/Compiled by Matthew Knight of the Lowell Observatory).

The forward scattering of light also plays a key role in the predicted brightness of a comet. The November issue of Astronomy Magazine has a great article on this phenomenon. It’s interesting to note that ISON stacks up as a “9” on their accumulated point scale, right at the lower threshold of comet “greatness,” versus a 15 for sungrazing Comet C/1965 S1 Ikeya-Seki. Another famous “9” was Comet C/1996 B2 Hyakutake, which passed 0.1018 A.U. or 15.8 million kilometres from Earth on March 25, 1996.

ISON will pass 0.429 A.U. or 64.2 million kilometres from Earth the day after Christmas. Bruce Willis can stay home for this one.

Here is a blow-by-blow breakdown of some key dates to watch for as ISON makes its plunge into the inner solar system:

-September 25^th: ISON crosses the border from the astronomical constellation of Cancer into Leo.

-September 27^th: ISON passes 2 degrees north of the planet Mars.

The path of Comet ISON from October 1st to November 21st. The position of the Sun is shown on the final date. (Created by the Author using Starry Night Education software).

-October 1^st: The 12% illuminated waning crescent Moon passes 10 degrees south of Mars & ISON.

-Early October: ISON may break +10^th magnitude and become visible with binoculars or a small telescope.

-October 4th: New Moon occurs. The Moon then exits the dawn sky, making for two weeks of prime viewing.

–October 10th: ISON enters view of NASA’s STEREO/SECCHI HI-2A CAMERA:

The path of ISON as it enters the view of STEREO. Credit: NASA/ISON Observing campaign)

-October 16^th: ISON passes just 2 degrees NNE of the bright star Regulus, making a great “guidepost” to pin it down with binoculars.

-October 18^th: The Full Moon occurs, after which the Moon enters the morning sky.

-October 26^th: A great photo-op for astro-imagers occurs, as ISON passes within three degrees the Leo galaxy trio of M95, M96, & M105.

The position of Comet ISON on October 26th in Leo. (Created by the author in Stellarium). — The position of Comet ISON on October 26th in Leo near Mars and a trio of galaxies. (Created by the author in Stellarium).

-October 30^th: The 17% illuminated Moon passes 6 degrees south of ISON.

-Early November: Comet ISON may make its naked eye debut for observers based at dark sky sites.

-November 3^rd: A hybrid (annular-total) solar eclipse occurs, spanning the Atlantic and Central Africa. It may just be possible for well placed observers to catch sight of ISON in the daytime during totality, depending on how quickly it brightens up. The Moon reaching New phase also means that the next two weeks will be prime view time for ISON at dawn.

-November 5^th: ISON crosses the border from the astronomical constellation of Leo into Virgo.

-November 7^th: ISON passes less than a degree from the +3.6 magnitude star Zavijava (Beta Virginis).

-November 8^th: ISON passes through the equinoctial point in Virgo around 16:00 EDT/20:00 UT, passing into the southern celestial hemisphere and south of the ecliptic.

-November 14^th: ISON passes less than a degree from the 10^th magnitude galaxy NGC 4697.

-November 17^th: The Moon reaches Full, passing into the morning sky.

-November 18^th: ISON passes just 0.38 degrees north of the bright star Spica.

-November 22^nd: ISON crosses into the astronomical constellation of Libra.

-November 23^rd: ISON sits 4.7 degrees SSW of the planet Mercury and 4.9 SSW of Saturn, respectively.

Looking east before dawn on the morning of November 23rd. (Created by the author using Starry Night Education software). — Looking east before dawn on the morning of November 23rd. Note comet 2P/Encke nearby! (Created by the author using Starry Night Education software).

-November 25^th: ISON pays a visit to another famous comet, passing just 1.2 degrees south of short period comet 2P/Encke which may shine at +8^th magnitude.

-November 27th: ISON enters the field of view of SOHO’s LASCO C3 coronagraph.

-November 28^th: ISON reaches perihelion at ~18:00 PM EST/ 23:00 UT.

After that, all bets are off. The days leading up to perihelion will be tense ones, as ISON then rounds the Sun on a date with astronomical destiny. Will it join the ranks of the great comets of the past? Will it stay intact, or shatter in a spectacular fashion? Watch this space for ISON updates… we’ll be back in late November with our post-perihelion guide!

Be sure to also enjoy recently discovered Comet C/2013 R1 Lovejoy later the year.

Got ISON pics? Send ’em in to Universe Today!

September 19, 2013December 23, 2015 by David Dickinson

More ISON Craziness: Tales of Popes, a Prophet and a Comet

Comet Halley as seen from the Kuiper Airborne Observatory in 1986. (Credit: NASA).

There’s an astronomical tall tale from the Middle Ages that seems to get recycled as factual every time a “great” comet rolls around. This week, we thought we’d look at a story that just won’t die, as well as a new twist in comet conspiracy that’s rolling around ye’ ole ‘Net.

We’ve debunked the current craziness surrounding ISON recently, but apparently our work isn’t finished! Comets seem to bring ‘em out of the woodwork. Today, we’ll discuss how that old prophet of doom Nostradamus may have “predicted” Comet ISON being part of the ‘end times,’ but first, let’s look at an astronomical tale of the past. Did a pope really excommunicate the most famous of all comets?

The mid-15^th century was a trying time for Medieval Europe. The Black Death had decimated the population of Europe a century prior, and the armies of the Ottoman Turks were advancing from the east. A bright comet could only bear ill will in the minds of the superstitious.

Pope Callixtus III: the ecommunicator of comets? (Credit: Museo de la Catherdral de Valencia). — Pope Callixtus III: the excommunicator of comets? (Credit: Museo de la Cathedral de Valencia).

It was into this setting that Pope Callixtus III came into power in 1455. Callixtus was the first of two popes fielded by the Spanish Borgia family, which would later include his nephew Rodrigo who became Pope Alexander the VI, as depicted in the Showtime series The Borgias.

A fine the apparition of Halley’s Comet occurred in June and July 1456. Belgrade was to come under siege by the Ottoman Turks from July 4^th to 22^nd of that year, and the Fall of Constantinople on May 29^th, 1453 to Mehmed II was still fresh on everyone’s mind.

Astronomical signs and omens were a hot topic as well. The partial lunar eclipse of May 22nd, 1453 was seen by many to have fulfilled prophecy that an eclipse would mark the fall of Constantinople. Of course, there are from 4 to 7 eclipses that can be seen on any given year, and lunar eclipses are visible from the entire moonward facing side of the Earth. It’s not too tough to find one to fit any given bill of gloom and doom.

Keep in mind, Halley’s Comet wasn’t even identified in the 15th century as the same comet that was returning once every 75.3 years. That fact wouldn’t be uncovered until Edmund Halley successfully predicted the return of the comet that now bears his name on Christmas Day 1758.

Halley’s Comet would’ve been a spectacular sight in the early summer of 1456, unfurling a tail that was said to have been 60 degrees long and spanning the constellations of Cancer and Leo. The brilliant comet would’ve been a conspicuous object for up to three hours after sunset, and it’s certain that observers around the Mediterranean, including a Rome-based pope would’ve seen it.

A depiction of the passage of Comet Halley through the constellations of Cancer & Leo in 1456. (Wikimedia Commons image in the Public Domain).

But did the pope actually excommunicate the comet to assuage the fears of the European populace of an invasion from the east?

While a quixotic story, the idea that a pope could’ve banned a heavenly body from salvation is apocryphal as best. The Papal Bull issued by Callixtus III on June 29^th, 1456 called for prayers and penance and the ringing of church bells in light of the cruelty visited upon Eastern Europe by invaders from the east, but makes no mention of the comet. In fact, no primary source for the tale exists.

The story seems to have gotten its start with a historian named Platina, who wrote a biography of Callixtus III in 1471. Here we find the appearance of:

“A hairy reddish comet appearing for several days… Callixtus, in order to avert the wrath of God, ordered processions to be held…”

No out right excommunication per se, but the Pope and the comet were now forever linked in the eye of history.

The pitched Battle of Nandorfehervar during the 1456 Siege of Belgrade. (Wikimedia Commons scan in the Public Domain). — The pitched Battle of Nandorfehervar during the 1456 Siege of Belgrade. (Painting by Rubens in the Public Domain).

French mathematician and astronomer Pierre-Simon Laplace later gave the excommunication tale a boost in the late 18^th century, and further embellishment followed from astronomer François Arago writing in 1832.

Keep in mind, these are historical works written down some years after the fact, often translated from Latin to French to English—ideas such as LaPlace’s “conjurer la comete” can easily come across as to “exorcise” or “excommunicate” a comet. Also, political satire of popes, both alive and dead, was common after the start of the Protestant Reformation. Halley’s Comet also made a fine apparition in 1835, and Arago may have been looking for something to captivate the public with in anticipation.

But although this story was debunked over a century ago, it still makes its rounds. None other than Carl Sagan repeated the excommunication story in his book Comet (sorry Carl!) although he also notes that the tale is apocryphal. Although the story of the excommunication of Halley’s Comet has been debunked time and again, a search of the Internet reveals about an even split between the credulous and the skeptical.

But there is also a current mythos being born around Comet ISON, Pope Francis and Nostradamus on ye ole web. For the most part, it has to do with — you guessed it — the end of the world. As per the usual, great comets are harbingers of catastrophic events. Combine the words of Nostradamus with the fact that 2013 has been hyped as “The Year of the Comet,” along with Pope Benedict’s unusual resignation, and that equals The End of Time.

If you don’t believe me, search of Comet/ISON/Pope and see what turns up. The gist of the prophecy cites a quatrain stating that:

“the great star for seven days shall burn

So nakedly clear like two suns appearing

The large dog all night howling

While the great Pontiff shall change his territory.”

Of course, the quatrains of Nostradamus, like all prophecies, are suitably vague enough that they could be interpreted almost in whatever fashion suits the reader. And again, we’re looking at the old 16^th century French translated into modern English.

And like eclipses, there are a handful of comets every year. Most reach binocular visibility, and a few may go on to become visible to the naked eye. We’ve already had two comets that crossed this threshold this year, comet C/2011 L4 PanSTARRS and C/2012 F6 Lemmon.

Comet ISON as seen from the Hubble Space Telescope- no popes were harmed in the taking of this image! (credit: NASA/ESA/STScI/AURA). — Comet ISON as seen from the Hubble Space Telescope… no popes were harmed or forced to flee in the taking of this image. (credit: NASA/ESA/STScI/AURA).

And Comet ISON’s “greatness” is still very much in question. Its currently only at 12^th magnitude and probably won’t be a naked eye object until at least early November. And it certainly won’t have the appearance of a second Sun!

I’ll leave it to the armchair predictors of comet doom to decipher what “the large dog howling” even means. The chief logical fallacy evoked by the adherents of Nostradamus is what is known as retrofitting— it’s easy to take a cryptically predicted disaster and find an earthquake, eclipse, and yes, even a comet that falls roughly near the given date.

Of course, if ISON kicks into high gear, then we could really be in for a grand show, along with an accompanying upswing in comet hysteria. And thus, the tireless vigilance against comet-mania continues. Hey, we’re all after “link juice” and the almighty SEO, right? Of course, the real harm comes when something like the 1997 Heaven’s Gate mass suicide, inspired by rumors of an alien spacecraft following comet Hale-Bopp occurs.

Halleys March 9 2062 — Halley’s Comet as seen on the morning of March 9th, 2062. (Created by the author using Starry Night Education software).

In short, enjoy the show as ISON approaches, read the online tales of popes and comets past… but as rapper and surreptitious promoter of skepticism Chuck D of Public Enemy implores us, don’t believe the hype.

Maybe we’ll finally be an enlightened and rational species when Halley’s Comet pays us a visit again starting in the summer of 2061 through the spring of 2062!

-For an exhaustive look at the myth of the excommunication of Halley’s Comet, Read An Historical Examination of the Connection of Callixtus III with Halley’s Comet published in 1910.

-To see a (mostly) woo free version of the current Comet ISON versus Pope Francis mythos, (with quatrains) check out this article from news.com.au. Hey, we sift through woo so you don’t have to!

September 16, 2013December 23, 2015 by David Dickinson

The September Equinox: ‘Tis the Season to Spy the Zodiacal Light

The zodiacal light in the Nevada dawn. The plane of the ecliptic can be traced by Jupiter in Gemini & Mars in the Beehive cluster just below center. (Credit: Cory Schmitz, used with permission).

This week leading up to the September equinox offers you a fine chance to catch an elusive phenomenon in the pre-dawn sky.

We’re talking about the zodiacal light, the ghostly pyramid-shaped luminescence that heralds the approach of dawn. Zodiacal light can also be seen in the post-dusk sky, extending from the western horizon along the ecliptic.

September is a great time for northern hemisphere observers to try and sight this glow in the early dawn. This is because the ecliptic is currently at a high and favorable angle, pitching the zodiacal band out of the atmospheric murk low to the horizon. For southern hemisphere observers, September provides the best time to hunt for the zodiacal light after dusk. In March, the situation is reversed, with dusk being the best for northern hemisphere observers and dawn providing the best opportunity to catch this elusive phenomenon for southern observers.

The clash of the zodiacal light and the plane of our galaxy. (Credit: Cory Schmitz, used with permission).

Cory Schmitz’s recent outstanding photos taken from the Nevada desert brought to mind just how ephemeral a glimpse of the zodiacal light can be. The glow was a frequent sight for us from dark sky sites just outside of Tucson, Arizona—but a rarity now that we reside on the light-polluted east coast of the U.S.

In order to see the zodiacal light, you’ll need to start watching before astronomical twilight—the start of which is defined as when the rising Sun reaches 18 degrees below the local horizon—and observe from as dark a site as possible under a moonless sky.

The Bortle dark sky scale lists the zodiacal light as glimpse-able under Class 4 suburban-to-rural transition skies. Under a Class 3 rural sky, the zodiacal light may extend up to 60 degrees above the horizon, and under truly dark—and these days, almost mythical—Class 1 and 2 skies, the true nature of the zodiacal band extending across the ecliptic can become apparent. The appearance and extent of the zodiacal light makes a great gauge of the sky conditions at that favorite secret dark sky site.

The source of the zodiacal light is tiny dust particles about 10 to 300 micrometres in size scattered across the plane of the solar system. The source of the material has long been debated, with the usual suspects cited as micrometeoroid collisions and cometary dust. A 2010 paper by Peter Jenniskens and David Nesvorny in the Astrophysical Journal cites the fragmentation of Jupiter-class comets. Their model satisfactorily explains the source of about 85% of the material. Dust in the zodiacal cloud must be periodically replenished, as the material is slowly spiraling inward via what is known as the Poynting-Robertson effect. None other than Brian May of the rock group Queen wrote his PhD thesis on Radial Velocities in the Zodiacal Dust Cloud.

But even if you can’t see the zodiacal light, you still just might be able to catch it. Photographing the zodiacal light is similar to catching the band of the Milky Way. In fact, you can see the two crossing paths in Cory’s images, as the bright winter lanes of the Orion Spur are visible piercing the constellation of the same name. Cory used a 14mm lens at f/3.2 for the darker image with a 20 second exposure at ISO 6400 and a 24mm lens at f/2.8 with a 15 second exposure at ISO 3200 for the brighter shot.

The orientation of the ecliptic & the zodiacal band as seen from latitude 30 deg north in September, about 1 hour before sunrise. (Created by the author in Stellarium).

Under a truly dark site, the zodiacal light can compete with the Milky Way in brightness. The early Arab astronomers referred to it as the false dawn. In recent times, we’ve heard tales of urbanites mistaking the Milky Way for the glow of a fire on the horizon during blackouts, and we wouldn’t be surprised if the zodiacal light could evoke the same. We’ve often heard our friends who’ve deployed to Afghanistan remark how truly dark the skies are there, as military bases must often operate with night vision goggles in total darkness to avoid drawing sniper fire.

Another even tougher but related phenomenon to spot is known as the gegenschein. This counter glow sits at the anti-sunward point where said particles are approaching 100% illumination. This time of year, this point lies off in the constellation Pisces, well away from the star-cluttered galactic plane. OK, we’ve never seen it, either. A quick search of the web reveals more blurry pics of guys in ape suits purporting to be Bigfoot than good pictures of the gegenschein. Spotting this elusive glow is the hallmark of truly dark skies. The anti-sunward point and the gegenschein rides highest near local midnight.

And speaking of which, the September equinox occurs this weekend on the 22^nd at 4:44 PM EDT/20:44 Universal Time. This marks the beginning of Fall for the northern hemisphere and the start of summer for the southern.

The Full Harvest Moon also occurs later this week, being the closest Full Moon to the equinox occurring on September 19^th at 7:13AM EDT/11:13 UT. Said Moon will rise only ~30 minutes apart on successive evenings for mid-northern latitude observers, owing to the shallow angle of the ecliptic. Unfortunately, the Moon will then move into the morning sky, drowning out those attempts to spy the zodiacal light until late September.

Be sure to get out there on these coming mornings and check out the zodiacal light, and send in those pics in to Universe Today!

September 12, 2013April 26, 2016 by David Dickinson

Spotting Juno: NASA’s Jupiter-bound Spacecraft Gets a Boost from Earth on October 9th, 2013

An artist's conception of Juno's October 9th flyby of the Earth. (Credit: NASA/JPL -Caltech).

Psst! Live in South Africa and read Universe Today? Then you might just get a peak at the Juno spacecraft as it receives a boost from our fair planet on the evening of October 9^th, 2013.

Launched from Cape Canaveral Air Force Station on August 5^th, 2011 atop an Atlas 5 rocket in a 551 configuration, Jupiter-bound Juno is approaching the Earth from interior to its orbit over the next month. Its closest approach to the Earth during its October 9^th flyby will occur at 19:21 Universal Time (UT) which is 3:21 PM Eastern Daylight Saving Time. The spacecraft will pass 559 kilometres over the South Atlantic to a point 200 kilometres off of the southeastern coast of South Africa at latitude -34.2° south & longitude 34° east.

For context, this is just about 25% higher than the International Space Station orbits at an average of 415 kilometres above the Earth. The ISS is 108.5 metres across on its longest dimension, and we wouldn’t be surprised if Juno were a naked eye object for well placed observers watching from a dark sky site around Cape Town, South Africa. Especially if one of its three enormous 8.9 metre long solar panels were to catch the Sun and flare Iridium-style!

Two minutes before closest approach, Juno will experience the only eclipse of its mission, passing into the umbra of Earth’s shadow for about 20 minutes. Chris Peat at Heavens-Above also told Universe Today that observers in India are also well-placed to catch sight of Juno with binoculars after it exits the Earth’s shadow.

Juno passed its half-way mark to Jupiter last month on August 12^th when the “odometer clicked over” to 9.464 astronomical units. Juno will enter orbit around Jupiter on July 4^th, 2016. Juno will be the second spacecraft after Galileo to permanently orbit the largest planet in our solar system.

The passage of Juno through the Earth's shadow on October 9th, 2013. (Credit and Copyright: Heavens-Above, used with permission). — The passage of Juno through the Earth’s shadow on October 9th, 2013. (Credit and Copyright: Heavens-Above, used with permission).

Catching a flyby of Juno will be a unique event. Unfortunately, the bulk of the world will miss out, although you can always vicariously fly along with Juno with Eyes on the Solar System. Juno is currently moving about 7 km/s relative to the Earth, and will move slightly faster than the ISS in its apparent motion across the sky from west to east before hitting Earth’s shadow. This slingshot will give Juno a 70% boost in velocity to just under 12km/s relative to Earth, just slower than Pioneer 10’s current motion relative to the Sun of 12.1km/s.

At that speed, Juno will be back out past the Moon in about 10 hours after flyby. There’s a chance that dedicated imagers based along North American longitudes could still spy Juno later that evening.

Juno approaches the Earth from the direction of the constellation Libra and will recede from us in the direction of the constellation Perseus on the night of October 9^th.

The ground track covered by Juno as it passes by the Earth. (Credit & Copyright: Heavens-Above, used with permission).

There’s also a precedent for spotting such flybys previous. On August 18^th, 1999, NASA’s Cassini spacecraft made a flyby of the Earth at 1,171 kilometres distant, witnessed by observers based in the eastern Pacific region. Back then, a fuss had been raised about the dangers that a plutonium-powered spacecraft might posed to the Earth, should a mis-calculation occur. No such worries surround Juno, as it will be the first solar-powered spacecraft to visit the outer solar system.

And NASA wants to hear about your efforts to find and track Juno during its historic 2013 flyby of the Earth. JPL Horizons lists an ephemeris for the Juno spacecraft, which is invaluable for dedicated sky hunters. You can tailor the output for your precise location, then aim a telescope at low power at the predicted right ascension and declination at the proper time, and watch. Precise timing is crucial; I use WWV shortwave radio broadcasting out of Fort Collins, Colorado for ultra-precise time when in the field.

As of this writing, there are no plans to broadcast the passage of Juno live, though I wouldn’t be surprised if someone like Slooh decides to undertake the effort. Also, keep an eye on Heavens-Above, as they may post sighting opportunities as well. We’ll pass ‘em along if they surface!

Late Breaking: And surface they have… a page dedicated to Juno’s flyby of Earth is now up on Heavens-Above.

Juno is slated to perform a one year science mission studying the gravity and magnetic field of Jupiter as well as the polar magnetosphere of the giant planet. During this time, Juno will make 33 orbits of Jupiter to complete its primary science mission. Juno will study the environs of Jupiter from a highly inclined polar orbit, which will unfortunately preclude study of its large moons. Intense radiation is a primary hazard for spacecraft orbiting Jupiter, especially one equipped with solar panels. Juno’s core is shielded by one centimetre thick titanium walls, and it must thread Jupiter’s radiation belts while passing no closer than 4,300 kilometres above the poles on each pass. One run-in with the Io Plasma Torus would do the spacecraft in. Like Galileo, Juno will be purposely deorbited into Jupiter after its primary mission is completed in October 2017.

If you live in the right location, be sure to check out Juno as it visits the Earth, one last time. We’ll keep you posted on any live broadcasts or any further info on sighting opportunities as October 9^th draws near!

– Got pics of Juno on its flyby of the Earth? Send ’em in to Universe Today!

– You can also follow the mission on Twitter as @NASAJuno.