Comet ISON, photographed with a 3-inch (80mm) telescope on this morning Sept. 28 shows a circular green coma and short dust tail pointing northwest. Click to enlarge. Credit: Michael Jaeger
As NASA and the European Space Agency prepare their remote photojournalists – Mars Express, Mars Reconnaissance Orbiter and the Curiosity and Opportunity rovers – to capture photos of Comet ISON’s flyby of Mars early next week, amateur astronomers continue to monitor and photograph the comet from backyard observatories across the blue Earth. Several recent color photos show ISON’s bright head or nucleus at the center of a puffy, green coma. Green’s a good omen – a sign the comet’s getting more active as it enters the realm of the inner solar system and sun’s embrace.
Another great photo of the “greening” of Comet ISON taken on Sept. 24 with a 17-inch (43-cm) telescope. Click to enlarge. Credit: Damian Peach
Sunlight beating down on the comet’s nucleus (core) vaporizes dust-impregnated ice to form a cloud or coma, a temporary atmosphere of water vapor, dust, carbon dioxide, ammonia and other gases. Once liberated , the tenuous haze of comet stuff rapidly expands into a huge spherical cloud centered on the nucleus. Comas are typically hundreds of thousands of miles across but are so rarified you could wave your hand through one and not feel a thing. The Great Comet of 1811 sported one some 864,000 miles (1.4 million km) across, nearly the same diameter as the sun!
Among the materials released by solar heating are cyanogenand diatomic carbon. Both are colorless gases that fluoresce a delicious candy-apple green when excited by energetic ultraviolet light in sunlight.
Sounds like a plan. Newspaper clipping from 1910.
Cyanogen smells pleasantly of almonds, but it’s a poisonous gas composed of one atom each of carbon and nitrogen. Diatomic carbon or C2 is equally unpleasant. It’s a strong, corrosive acid found not only in comets but also created as a vapor in high-energy electric arcs. But nature has a way of taking the most unlikely things and fashioning them into something beautiful. If you’re concerned about the effects of cometary gas and dust on people, rest easy. They’re spread too thinly to touch us here on Earth. That didn’t stop swindlers from selling “comet pills” and gas masks to protect the public from poisoning during the 1910 return of Halley’s Comet. Earth passed through the tail for six hours on May 19 that year. Amazingly, those who took the pills survived … as did everyone else.
Comet ISON’s location and approximate appearance on October 1 seen from the Curiosity Rover. ISON will pass only 6.7 million miles (10.8 million km) from Mars on Tuesday Oct. 1. Stellarium
While Comet ISON is still too faint for visual observers to discern its Caribbean glow, that will change as it beelines for the sun and brightens. If you could somehow wish yourself to Mars in the next few days, I suspect you’d easily see the green coma through a telescope. The comet – a naked eye object at magnitude 2.5-3 – glows low in the northern sky from the Curiosity rover’s vantage point 4.5 degrees south of the Martian equator.
Comet Hale-Bopp shows off its bright dust tail and fainter, blue ion tail in early spring 1997. Credit: Bob King
I’ve noticed that when a comet reaches about 7th magnitude, the green coloration becomes apparent in 8-inch (20 cm) and larger telescopes. Bright naked eye comets often display multiple subtle colors that change chameleon-like over time. Dust tails, formed when sunlight pushes dust particles downwind from the coma, glow pale yellow. Gusty solar winds sweep back molecules from the coma into a second “ion” tail that glows pale blue from jazzed up carbon monoxide ions fluorescing in solar UV.
One of the highlights of seeing Comet L4 PANSTARRS through a small telescope was its brilliant, pea-like false nucleus glowing yellow from sunlit dust. The real comet nucleus – the actual comet – lies within the false nucleus and hidden by dust. Drawing: Bob King
During close encounters with the sun, millions of pounds of dust per day boil off a comet’s nucleus, forming a small, intensely bright, yellow-orange disk in the center of the coma called a false nucleus. Earlier this year, when Comet C/2011 L4 PANSTARRS emerged into the evening sky after perihelion, not only was its yellow tail apparent to binocular users but the brilliant false nucleus glowed a lovely shade of lemon in small telescopes.
With ISON diving much closer to the sun than L4 PANSTARRS, expect a full color palette in the coming weeks. While it may not be easy being green for Sesame Street’s Kermit the Frog, comets do it with aplomb.
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 21st, 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 28th.
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 +12th 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 1st 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 28th 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 +6th 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 +4th magnitude or so.
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 25th: ISON crosses the border from the astronomical constellation of Cancer into Leo.
-September 27th: 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 1st: The 12% illuminated waning crescent Moon passes 10 degrees south of Mars & ISON.
-Early October: ISON may break +10th 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:
-October 16th: ISON passes just 2 degrees NNE of the bright star Regulus, making a great “guidepost” to pin it down with binoculars.
-October 18th: The Full Moon occurs, after which the Moon enters the morning sky.
-October 26th: 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 near Mars and a trio of galaxies. (Created by the author in Stellarium).
-October 30th: 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 3rd: 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 5th: ISON crosses the border from the astronomical constellation of Leo into Virgo.
-November 7th: ISON passes less than a degree from the +3.6 magnitude star Zavijava (Beta Virginis).
-November 8th: 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 14th: ISON passes less than a degree from the 10th magnitude galaxy NGC 4697.
-November 17th: The Moon reaches Full, passing into the morning sky.
-November 18th: ISON passes just 0.38 degrees north of the bright star Spica.
-November 22nd: ISON crosses into the astronomical constellation of Libra.
-November 23rd: 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. Note comet 2P/Encke nearby! (Created by the author using Starry Night Education software).
-November 25th: ISON pays a visit to another famous comet, passing just 1.2 degrees south of short period comet 2P/Encke which may shine at +8th magnitude.
-November 27th: ISON enters the field of view of SOHO’s LASCO C3 coronagraph.
-November 28th: 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!
Comet Tempel 1 a minute after being struck by Deep Impact's impactor on July 4, 2005 (NASA/JPL-Caltech/UMD)
After almost 9 years in space that included an unprecedented July 4th impact and subsequent flyby of a comet, an additional comet flyby, and the return of approximately 500,000 images of celestial objects, NASA’s Deep Impact/EPOXI mission has officially been brought to a close.
The project team at NASA’s Jet Propulsion Laboratory has reluctantly pronounced the mission at an end after being unable to communicate with the spacecraft for over a month. The last communication with the probe was Aug. 8. Deep Impact was history’s most traveled comet research mission, having journeyed a total of about 4.7 billion miles (7.58 billion kilometers).
“Deep Impact has been a fantastic, long-lasting spacecraft that has produced far more data than we had planned,” said Mike A’Hearn, the Deep Impact principal investigator at the University of Maryland in College Park. “It has revolutionized our understanding of comets and their activity.”
Artist’s rendering of the Deep Impactor flyby spacecraft (NASA)
Launched in January 2005, the spacecraft first traveled about 268 million miles (431 million kilometers) to the vicinity of comet Tempel 1. On July 3, 2005, the spacecraft deployed an impactor into the path of comet to essentially be run over by its nucleus on July 4. This caused material from below the comet’s surface to be blasted out into space where it could be examined by the telescopes and instrumentation of the flyby spacecraft. Sixteen days after that comet encounter, the Deep Impact team placed the spacecraft on a trajectory to fly back past Earth in late December 2007 to put it on course to encounter another comet, Hartley 2 in November 2010, thus beginning the spacecraft’s new EPOXI mission.
“Six months after launch, this spacecraft had already completed its planned mission to study comet Tempel 1,” said Tim Larson, project manager of Deep Impact at JPL. “But the science team kept finding interesting things to do, and through the ingenuity of our mission team and navigators and support of NASA’s Discovery Program, this spacecraft kept it up for more than eight years, producing amazing results all along the way.”
The spacecraft’s extended mission culminated in the successful flyby of comet Hartley 2 on Nov. 4, 2010. Along the way, it also observed six different stars to confirm the motion of planets orbiting them, and took images and data of the Earth, the Moon and Mars. These data helped to confirm the existence of water on the Moon, and attempted to confirm the methane signature in the atmosphere of Mars. One sequence of images is a breathtaking view of the Moon transiting across the face of Earth.
This image of comet ISON C/2012 S1 from NASA’s Deep Impact/EPOXI spacecraft clearly shows the coma and nucleus on Jan. 17 and 18, 2013 beyond the orbit of Jupiter. Credit: NASA.
After losing contact with the spacecraft last month, mission controllers spent several weeks trying to uplink commands to reactivate its onboard systems. Although the exact cause of the loss is not known, analysis has uncovered a potential problem with computer time tagging that could have led to loss of control for Deep Impact’s orientation. That would then affect the positioning of its radio antennas, making communication difficult, as well as its solar arrays, which would in turn prevent the spacecraft from getting power and allow cold temperatures to ruin onboard equipment, essentially freezing its battery and propulsion systems.
Without battery power, the Deep Impact spacecraft is now adrift and silent, spinning out of control through the solar system.
Launch of Deep Impact aboard a Boeing Delta II rocket from Cape Canaveral AFS on Jan. 12, 2005 (NASA)
“Despite this unexpected final curtain call, Deep Impact already achieved much more than ever was envisioned. Deep Impact has completely overturned what we thought we knew about comets and also provided a treasure trove of additional planetary science that will be the source data of research for years to come.”
– Lindley Johnson, Program Executive for the Deep Impact mission
It’s a sad end for a hardworking spacecraft, but over the course of its 8 1/2 years in space Deep Impact provided many significant results for the science community. Here are the top five, according to the mission’s principal investigator Michael A’Hearn.
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-15th 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 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 4th to 22nd of that year, and the Fall of Constantinople on May 29th, 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 29th, 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. (Painting by Rubens in the Public Domain).
French mathematician and astronomer Pierre-Simon Laplace later gave the excommunication tale a boost in the late 18th 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 16th 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 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 12th 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.
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!
-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!
Water, ammonia, methanol and carbon dioxide could have come to Earth from cometary sources, according to a new study. Source: Lawrence Livermore National Laboratory
The energy of comets smashing into Earth billions of years ago could have generated life out of the building blocks of life that those extraterrestrial objects brought, according to new experiments published in a peer-reviewed study.
The finding comes after a team “shock compressed” an icy slush similar in composition to that found on comets, which are sometimes called “dirty snowballs” because they are a mixture of ice and rock. The compression, which researchers say is similar in intensity to comets hitting the Earth, generated amino acids – considered the basic bits of life.
“Our work shows that the basic building blocks of life can be assembled anywhere in the Solar System and perhaps beyond,” stated Zita Martins, a co-author of the paper who is with Imperial College London’s department of Earth science and engineering.
“However, the catch is that these building blocks need the right conditions in order for life to flourish. Excitingly, our study widens the scope for where these important ingredients may be formed in the Solar System and adds another piece to the puzzle of how life on our planet took root.”
An object entering a planet’s atmosphere. Credit: Imperial College London
Whether life arose on Earth, or was imported from other locations in the Solar System or universe, has been a hot-button topic for decades. Learning the answer not only has implications for our own planet, but also for understanding how likely it is that life exists in other Solar System planets and moons — not to mention moons or planets in other star systems.
The new experiment — which the researchers say uncovers evidence of a “cosmic factory” process for starting life — saw the team at the University of Kent and the Imperial College using a gas gun to send a projectile into an ice combination similar to what one would find a comet. After the impact, the researchers saw amino acids forming.
The work builds on research initially done by Nir Goldman, a scientist with the Lawrence Liverpool National Laboratory, who predicted the results based on simulations in the laboratory’s supercomputer. Goldman found that comets could have imported life’s building blocks (ammonia, methanol, carbon dioxide and water). Then, as they smashed into Earth, the energy produced could be enough to jump-start life.
The building blocks of proteins are molecules called amino acids. Most types of amino acids can exist in two different forms, one that is ‘left-handed’ and the other as ‘right-handed.’ Credit: NASA
“This process demonstrates a very simple mechanism whereby we can go from a mix of simple molecules, such as water and carbon-dioxide ice, to a more complicated molecule, such as an amino acid,” stated Mark Price, a co-author and physicist from the University of Kent.
“This is the first step towards life. The next step is to work out how to go from an amino acid to even more complex molecules such as proteins.”
You can read the research paper, which was published Sept. 15, on Nature Geoscience.
New Comet Lovejoy starts out slow but quickly gains speed as it crosses from near Orion in mid-September to Ursa Major in November, when it will be closest to Earth. Created with Chris Marriott's SkyMap software
Move over Comet ISON. You’ve got company. Australian amateur astronomer Terry Lovejoy, discoverer of three previous comets, including the famous, long-tailed sungrazer C/2011 W3 (Lovejoy), just added a 4th to his tally.
This new comet will add to a lineup of comets that should grace early November skies in the northern hemisphere: Comets ISON, Encke and now the new Lovejoy.
Comet C/2013 R1 Lovejoy photographed on Sept. 10. The comet is visible in larger amateur telescopes in September but may brighten to small scope visibility in November. Streak at right is a geostationary satellite. Credit: Michael Jaeger
The discovery of C/2013 R1 Lovejoy was announced on Sept. 9 after two nights of photographic observations by Lovejoy with an 8-inch (20 cm) Schmidt-Cassegrain reflector. When nabbed, the comet was a faint midge of about 14.5 magnitude crossing the border between Orion and Monoceros. Subsequent observations by other amateur astronomers peg it a bit brighter at 14.0 with a small, condensed coma.
Comet Lovejoy has a small, condensed coma (head) about 30 arc seconds across with a faint, short tail in this photo made on Sept. 8. Credit: Ernesto Guido and Nick Howes
Right now you’ll need a hefty telescope to catch a glimpse of Lovejoy’s latest, but come November the comet will glow at around 8th magnitude, making it a perfect target for smaller telescopes. At closest approach on the Nov. 23, Lovejoy will pass 38.1 million miles (61.3 million km) from Earth while sailing across the Big Dipper at a quick pace.
The comet is a faint 14th magnitude object just east of Orion’s Belt in the dim constellation Monoceros the Unicorn. The map shows its position tomorrow morning Sept. 11 just before the start of morning twilight. Stellarium
Mid to late November is also the time when Comet ISON, the current focus of much professional and amateur observation, will be at its brightest in the morning sky at around magnitude 2-3. Get ready for some busy nights at the telescope!
A graph showing the comet’s predicted magnitude (subject to change) in red versus the comet’s elongation or angular distance from the sun. You can see that it will up in a dark sky for a long time including around the time when it’s brightest. Credit: Ernesto Guido & Nick Howes
C/2013 R1 will whip by the sun on Christmas Day at a distance of 81 million miles (130.3 million km) and then return back to the deeps from whence it came.
The charts here give you a general idea of its location and path over the next couple months. As the comet crosses into small-scope territory in early November, I’ll provide maps for you to find it.
A graphic created by Stuart Atkinson showing the comet and planetary lineup that should be in the skies on November 9, 2013.
And as Stuart Atkinson noted on his website, Cumbrian Sky a great lineup should be in the northern hemisphere skies on November 9, 2013. From the left, Comet Encke will be magnitude 6, ISON should be at about magnitude 6 or 7; then Mars, followed by the new Comet Lovejoy, which will be still very faint at around magnitude 9, topped off by a bright Jupiter. The comets will not likely be of naked eye visibility, but this should be a great chance for astrophotographer to capture this lineup!
Comet Lovejoy is approaching the plane of the planets from “down under” (lower right). The diagram shows the comet’s position today. Like many comets, Lovejoy’s orbit is steeply inclined – in this case 62 degrees. Credit: NASA
Welcome to an exciting time for comet lovers, and congratulations Terry on another great discovery!
Spitzer image of an asteroid's surprise coma and tail (NASA/JPL-Caltech/DLR/NAU)
It’s a case of mistaken identity: a near-Earth asteroid with a peculiar orbit turns out not to be an asteroid at all, but a comet… and not some Sun-dried burnt-out briquette either but an actual active comet containing rock and dust as well as CO2 and water ice. The discovery not only realizes the true nature of one particular NEO but could also shed new light on the origins of water here on Earth.
JPL Near-Earth Object database map of 3552 Don Quixote’s orbit
Designated 3552 Don Quixote, the 19-km-wide object is the third largest near-Earth object — mostly rocky asteroids that orbit the Sun in the vicinity of Earth.
According to the IAU, an asteroid is coined a near-Earth object (NEO) when its trajectory brings it within 1.3 AU from the Sun and within 0.3 AU of Earth’s orbit.
About 5 percent of near-Earth asteroids are thought to actually be dead comets. Today an international team including Joshua Emery, assistant professor of earth and planetary sciences at the University of Tennessee, have announced that Don Quixote is neither.
An asteroid is coined a near-Earth object (NEO) when its trajectory brings it within 1.3 AU from the Sun and within 0.3 AU of Earth’s orbit. (IAU)
“Don Quixote has always been recognized as an oddball,” said Emery. “Its orbit brings it close to Earth, but also takes it way out past Jupiter. Such a vast orbit is similar to a comet’s, not an asteroid’s, which tend to be more circular — so people thought it was one that had shed all its ice deposits.”
Using the NASA/JPL Spitzer Space Telescope, the team — led by Michael Mommert of Northern Arizona University — reexamined images of Don Quixote from 2009 when it was at perihelion and found it had a coma and a faint tail.
Emery also reexamined images from 2004, when Quixote was at its farthest distance from the Sun, and determined that the surface is composed of silicate dust, which is similar to comet dust. He also determined that Don Quixote did not have a coma or tail at this distance, which is common for comets because they need the sun’s radiation to form the coma and the sun’s charged particles to form the tail.
The researchers also confirmed Don Quixote’s size and the low, comet-like reflectivity of its surface.
“The power of the Spitzer telescope allowed us to spot the coma and tail, which was not possible using optical telescopes on the ground,” said Emery. “We now think this body contains a lot of ice, including carbon dioxide and/or carbon monoxide ice, rather than just being rocky.”
This discovery implies that carbon dioxide and water ice might be present within other near-Earth asteroids and may also have implications for the origins of water on Earth, as comets are thought to be the source of at least some of it.
The amount of water on Don Quixote is estimated to be about 100 billion tons — roughly the same amount in Lake Tahoe.
“Our observations clearly show the presence of a coma and a tail which we identify as molecular line emission from CO2 and thermal emission from dust. Our discovery indicates that more NEOs may harbor volatiles than previously expected.”
– Mommert et al., “Cometary Activity in Near–Earth Asteroid (3552) Don Quixote “
The findings were presented Sept. 10 at the European Planetary Science Congress 2013 in London.
3552 Quixote isn’t the only asteroid found to exhibit comet-like behavior either — check out Elizabeth Howell’s recent article, “Asteroid vs. Comet: What the Heck is 3200 Phaethon?” for a look at another NEA with cometary aspirations.
A very zoomed-in image of Phaethon from NASA's STEREO spacecraft, showing a comet-like extension. Credit: Jewitt, Li, Agarwal /NASA/STEREO
Sometimes, putting things into categories difficult. Witness how many members of the general public are still unhappy that Pluto was reclassified as a dwarf planet, a decision made by the International Astronomical Union more than seven years ago.
And now we have 3200 Phaethon, an asteroid that is actually behaving like a comet. Scientists found dust that is streaming from this space rock as it gets close to the sun — similarly to how ices melt and form a tail as comets zoom by our closest stellar neighbor.
Phaethon’s orbit puts it in the same originating region as other asteroids (between Mars and Jupiter), but its dust stream is much closer to actions performed by a comet — an object that typically comes from an icy region way beyond Neptune. So far, therefore, the research team is calling Phaethon a “rock comet.” And after first proposing a theory a few years ago, they now have observations as to what may be going on.
Phaethon is not only an asteroid, but also a source of a prominent meteor shower called the Geminids. This shower happens every year around December when the Earth plows into the cloud of debris that Phaethon leaves in its wake. Astronomers have known about the Geminids’ source for a generation, but for decades could not catch the asteroid in the act of shedding its stuff.
That finally came with images of NASA’s twin sun-gazing Solar TErrestrial RElations Observatory (STEREO) spacecraft that were taken between 2009 and 2012. The researchers saw a “comet-like tail” extending from the 3.1-mile (five kilometer) asteroid. “The tail gives incontrovertible evidence that Phaethon ejects dust,” stated David Jewitt, an astronomer at the University of California, Los Angeles who led the research. “That still leaves the question: why?”
Time lapse-photo showing geminids over Pendleton, OR. Credit: Thomas W. Earle
The answer lies in just how close Phaethon whizzes past the sun. At perihelion, its closest approach to the sun, it only appears eight degrees (16 solar diameters) away from the sun in Earth’s sky. This close distance makes it all but impossible to study the asteroid without special equipment, which is why STEREO came in so handy.
When Phaethon reaches its closest approach of 0.14 Earth-sun distances, surface temperatures rise above an estimated 1,300 degrees Fahrenheit (700 degrees Celsius). It’ s way too hot for ice, as what happens with a comet. In fact, it’s probably hot enough to make the rocks crack and break apart. The researchers publicly hypothesized this was happening at least as far back as 2010, but this finding provided more evidence to support that theory.
“The team believes that thermal fracture and desiccation fracture (formed like mud cracks in a dry lake bed) may be launching small dust particles that are then picked up by sunlight and pushed into the tail,” a statement from the research team read.
“While this is the first time that thermal disintegration has been found to play an important role in the solar system,” they added, “astronomers have already detected unexpected amounts of hot dust around some nearby stars that might have been similarly produced.”
The results were presented at the European Planetary Science Congress on Tuesday. By the way, STEREO also caught Mercury behaving somewhat like a comet in results released in 2010, although that find was related to the planet’s escaping sodium atmosphere.
Read more about the research in the June 26 issue of Astrophysical Letters. A preprint version is also available on Arxiv.
This image of comet ISON C/2012 S1 from NASA’s Deep Impact/EPOXI spacecraft clearly shows the coma and nucleus on Jan. 17 and 18, 2013 beyond the orbit of Jupiter. Credit: NASA.
Disappointing news today from Dr. Mike A’Hearn, Principal Investigator of the EPOXI mission, which has been using the repurposed spacecraft from the Deep Impact mission to study comets. The spacecraft was going to take some much-anticipated images of Comet ISON, but apparently a communication problem has occurred and the images may have been lost or possibly never taken.
“We have not received any of our expected observations of comet ISON due to a spacecraft problem,” A’Hearn wrote in an update on the EXPOXI website. “Communication with the spacecraft was lost some time between August 11 and August 14 (we only talk to the spacecraft about once per week). The last communication was on August 8. After considerable effort, the team on August 30 determined the cause of the problem. The team is now trying to determine how best to try to recover communication.”
No additional information was provided about the cause of the problem, however.
The Deep Impact mission intentionally crashed an impactor into comet Tempel-1 on July 4, 2005. Since then, EPOXI — the name comes from two combined missions to re-use the observing spacecraft, the Extrasolar Planet Observations and Characterization (EPOCh) and the Deep Impact Extended Investigation (DIXI) — has gone on to study comet Hartley 2, performing a close fly-by in 2010, studied C/2009 P1 (Garradd) in 2012, and has continued to be used as a remote observatory for studying comets.
EPOXI took images of Comet ISON on January 17, 2013, showing that the comet’s brightness varied on a timescale of hours (see the video above). There was another observing window from mid-February to March 8, where the team took infrared images of the comet.
The additional observing window from early July to early September is the timeframe for which there was a communication problem, and A’Hearn didn’t specify if any early images were received from the spacecraft, although he said they had “not received any of our expected observations.”
We’ll provide more information when it becomes available.
Comet ISON shows a small, compact coma and short, faint tail in this photo made by Krisztian Sarneczky on Aug. 31, 2013. Credit: K. Sárneczky / Konkoly Observatory
OK, you’ve waited patiently for Comet ISON to brighten and reappear in the dawn sky. It has. Now you’re chomping at the bit for a look at it in your telescope. Before you set the alarm and venture into the night, let’s prepare for what to expect. The better you know your target, the easier it will be to find.
Astrophotographer Alfons Diepvens captured this view of ISON on Sept. 1, 2013 through his telescope. Tail length and direction are indicated. Click image to see more his photos of ISON and other recent comets. Credit: Alfons Diepvens
The latest brightness estimates from the amateur comet community place ISON around magnitude 13, bright enough to be within reach of 10-inch (25 cm) and larger telescopes. Alan Hale of Arizona, co-discover of Comet Hale-Bopp, was one of the first to see it. Through his 16-inch (41 cm) reflecting telescope on September 1, he noted the comet as a small object about 0.6 arc minutes across (1 arc minute = 1/30 the diameter of the full moon), brighter in the center and shining faintly at magnitude 13.1. Picture a small, dim patch of glowing mist and you’ve got the picture. Hale’s observing conditions were excellent though he did have to contend with light from the nearby crescent moon. Starting tomorrow morning, the moon will finally be out of the picture.
With the moon out of the sky, now is a great time to hunt for Comet ISON. This map shows the sky as you face east tomorrow morning Sept. 3 around 5 a.m. local time just before the start of morning twilight. The comet is near both Mars and the Beehive Cluster. Stellarium
A sharp-eyed observer under the best skies would expect to see a fuzzy object this faint in a telescope as small as 8-inches (20 cm). Most of us will need something a little bigger. A 10-12 incher (25-30 cm) should do the trick until the comet swells into the 11-12 magnitude range. But you’ll need more than a hefty scope. Key to spotting ISON are good charts, a steady atmosphere for sharp images (shaky air blurs faint objects into invisibility) and catching the comet at the right time. I also encourage you to use averted vision, a great technique for spotting faint sky objects. Instead of staring directly at the comet, look off to the side of its position. That way you allow the comet’s feeble photons to flood your eye’s rod cells, those most sensitive to dim light.
This tighter view shows the comet (on Sept. 3) in relation to the naked eye star Gamma Cancri and the pretty Beehive Cluster in Cancer the Crab. North is up, west to the right. Stellarium
While it now rises around 3-3:30 a.m. local time, you’ll get your best – or only – view once ISON has cleared the light-sucking thick air and haze so common near the horizon. The optimum viewing time occurs shortly before the start of morning twilight when the comet will be about 15 degrees high in the northeastern sky. At mid-northern latitudes,where twilight begins about 1.5 hours before sunrise, that’s around 5 a.m. Did I mention you’d lose a few hours sleep in your pursuit?
Comet ISON’s position plotted for 5 a.m. Central Daylight Time tomorrow through the 10th. Stars are shown to 12th magnitude. Click for larger version. Created with Chris Marriott’s SkyMap Pro program
Lucky for us comet hunters, ISON’s location is easy to find only a few degrees east of the 1st magnitude planet Mars and about 2 degrees north of the familiar Beehive Cluster or M44. The first map shows the general view to get you oriented. The second takes us in closer to show the comet’s relation to the Beehive Cluster, and the third provides a detailed telescopic view with stars plotted to about 12th magnitude. The comet positions on the detailed map are plotted for 5 a.m. CDT. Since ISON moves relatively slowly, those positions will be accurate for a time zone or two either way. If you live significantly farther east or west of the U.S. Central Time Zone, you can interpolate between the tick marks.
It’s good news for skywatchers from here on out as ISON continues to brighten and rise higher in the east with each passing night. A month from now, it should be visible in scopes as small as 6-inches (15 cm). Good luck in your comet quest!
