Posted on by Nancy Atkinson

Comet Tempel 1 Now in StardustNeXT’s Field of View

The first image of comet Tempel 1 taken by NASA's Stardust spacecraft is a composite made from observations on Jan. 18 and 19, 2011. The panel on the right highlights the location of comet Tempel 1 in the frame. On Valentine's Day (Feb. 14 in U.S. time zones), Stardust will fly within about 200 kilometers (124 miles) of the comet's nucleus. Image credit: NASA/JPL-Caltech

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It’s comet ahoy! for the Stardust spacecraft, which is on its way to a Valentine’s Day meetup with comet Tempel 1. The images above were taken on Jan. 18 and 19 from a distance of 26.3 million kilometers (16.3 million miles), and 25.4 million kilometers (15.8 million miles). On Feb. 14, Stardust will fly within about 200 kilometers (124 miles) of the comet’s nucleus and for the first time we’ll get a second closeup look at Tempel 1.

“We were there in 2005 with the Deep Impact spacecraft, said Stardust-NExT Project Manager Tim Larson, speaking on today’s 365 Days of Astronomy podcast, “and this is a golden opportunity. It’s the first time we’ve ever been able to revisit a comet on a second pass near the sun.”

Larson said this encounter will give provide important information about how the surface of the comets change with each passage near the sun and whether the changes in the comet are global or just specific to certain areas on the surface.

From the Deep Impact mission, we already know that comet Tempel 1 has a wide variety of features on its surface.

“We have found smooth areas that look like material flows,” Larson said,” there are rough, pitted areas, there are craters on the surface, which we don’t know if they’re impact craters or if they’re caused by material coming out from the inside of the comet. So this is a very interesting comet in terms of variety of terrain.”

NASA's Deep Impact probe hits Comet Tempel 1 (NASA)

The exciting part will be comparing ‘before and after’ images of Tempel 1.

The spacecraft will be able to take up to 72 images and store them on board. Larson said the images will be carefully timed to center them around the closest approach to the comet, providing the best possible resolution.

“We should be able to get around three dozen images that are at better than 80 meters per pixel resolution and our closest approach images should be down below 20 meters per pixel resolution,” he said. “That will be good enough to resolve a lot of the key features on the surface of the comet and start that process of comparison.”

Artists concept of the stardust spacecraft flying throug the gas and dust from comet Wild 2. Credit: NASA/JPL

The repurposed Stardust spacecraft that flew past comet Wild 2 and brought back samples has just enough fuel to carry out maneuvers for the upcoming Tempel 1 flyby.

Larson said the preparations in designing the flyby sequences and software are almost complete and are being tested, and now the team is eagerly looking at the daily optical navigation images.

“We’re tracking where the comet is relative to the spacecraft,” he said, “and that will feed into our trajectory correction maneuvers. We have three more of those left before we arrive at the comet, and those will be used to target the spacecraft to the desired flyby point.”

The TCMs will occur on January 31, February 7, and then the last fully designed TCM will occur on February 12, two days before arrival.

There are challenges to using a recycled spacecraft.

“The primary challenge is, first of all, designing a new mission that it can accomplish with the fuel that it has left,” Larson said. “And through some clever mission design using some carefully timed trajectory correction maneuvers and taking advantage of some Earth gravity assists, we were able to modify the trajectory of the spacecraft to get it close to Tempel 1. So that’s been the primary challenge, and along with that is conserving the fuel that we have on board and making sure that we have enough fuel left to finish off this mission. Beyond that, there have been a few challenges in terms of aging equipment on board the spacecraft, — the spacecraft will be 12 years old in early February, and it’s well beyond its design life. And although everything is generally healthy on board, we have had a couple of pieces of equipment that were starting to age, and starting to degrade slightly. So we switched over to backup equipment so we were on fresh, healthy equipment, and we still have functioning equipment as backups.”

The closest approach will occur at 8:30 pm Pacific Time on February 14, 2011, where the spacecraft will be about 200 kilometers (125 miles) away from the surface of the comet, which is the closest any spacecraft has been to the surface of a comet.

Posted on by Ken Kremer

Stardust NExT Targets Valentines Day Encounter with Comet Tempel 1

Stardust-NExT: 2 Comet Flybys with 1 Spacecraft. Stardust-NExT makes history on Valentine’s Day - February, 14, 2011 – by becoming the first spacecraft to visit 2 comets and gather science data: Comet Wild 2 in 2004 (left) and Comet Tempel 1 in 2011 (right). Artist renderings Credit: NASA. Collage: Ken Kremer. See video below of Jan 19, 2011 Media briefing from the Science Team about plans for the Temple 1 cometary encounter

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After a more than decade long journey of 6 billion kilometers, hopes are high for a celestial date in space between an icy comet and a thrusting probe on Valentine’s Day 2011. The rendezvous in space between NASA’s approaching Stardust-NExT spacecraft and Comet Tempel 1 takes place nearly on the exact opposite side of the Sun on Feb 14, 2011 at approximately 11:37 p.m. EST (8:37 p.m. PST).

The top science goal is to find out “how much the comet’s surface has changed between two close passages to the sun” since it was last visited in 2005, said principal investigator Joe Veverka of Cornell University, Ithaca, N,Y at a media briefing today, Jan 19, at NASA Headquarters. Indeed it’s the first time in history that a comet has been visited twice by space probes from Earth.

The lead scientists and engineers outlined the plans for the cometary flyby at the briefing. See a video of the entire briefing below.


Since the last visit in 2005, the comet has completed another orbit around the sun. “It will be the first time we’ll be able to see changes after a comet has passed through one perihelion,” explained Veverka. Tempel 1 belongs to the Jupiter family of comets and orbits between Mars and Jupiter.


Comet Tempel 1 suffered a cosmic collision during that first encounter with an emissary from Earth when NASA’s Deep Impact smashed a copper projectile directly into the comets nucleus. The blast created an impact crater and ejected an enormous cloud of gas and debris. Reflected light off the dust particles totally obscured the view of the crater and prevented any images from being taken. Researchers had hoped to determine the size of the crater. A lot of bets hinge on that determination.

“We have a chance to complete the Deep Impact experiment. We hope to see how big the impact crater is and what that tells us about the mechanical properties, ” said Veverka.

20 Jan. 2011 Position of STARDUST-NExT probe - Looking Down on the Sun.
This image shows the current position of the STARDUST-NExT spacecraft and the spacecraft's trajectory (in blue) around the Sun. Credit: NASA

With just over 3 weeks remaining, the craft is approximately 24.6 million kilometers (15.3 million miles) away from its encounter. Stardust-NExT will zoom past the nearly 6-kilometer-wide comet (3.7 miles) at a distance of approximately 200 kilometers (124 miles) and at a speed of 10 km/sec according to Tim Larson, the mission’s project manager from the Jet Propulsion Laboratory (JPL), Pasadena, Calif.

“The spacecraft is still working well 12 years after launch. This is a bonus mission with a scientifically desirable target which we can get close to,” said Larson.

“Everything will happen autonomously,” stated Larson. “The craft will be about 2 AU away from Earth at encounter. Since the round trip signals will take about 40 minutes there is no chance for any real time changes.”

Different features on Tempel 1 discovered by Deep Imapct in 2005. Credit: NASA

“Stardust-NExT will take 72 high resolution images during the close approach encounter. These will be stored in an onboard computer and relayed back to Earth starting about an hour later. It will take about 12 hours to get them all back.”

NASA says that after processing, the images are expected to be available at approximately 4:30 a.m. EST (1:30 a.m. PST) on Feb. 15.

“For the first time we’ll go back to see what happens to a comet since our last visit,” explained Pete Schultz, co-investigator of Brown University, Providence, R.I. “The comet has been out to the orbit of Jupiter and back to Mars and had several outbursts of gas and dust. In 2005 we saw old and new surfaces. So it has a complicated geologic history. We hope to resolve the crater and see ejecta. But there are many unknowns. What we see – whether its the crater or the other unseen side – all depends on the rotation of the comet nucleus.”

“The comet dynamics are complex and erratic, not inert,” said Steve Chesley, a co-investigator at JPL. “They are like a rocket with no one at the controls. The orbit can change. So it is a huge challenge to target a spacecraft for a flyby or rendezvous.”

Stardust successful original mission was to fly by Comet Wild 2 on Jan 2, 2004. It then returned cometary dust particle in a sample return canister to Earth on Jan. 19, 2006 which reentered the atmosphere at the highest speed ever and parachuted to a safe landing. Credit: NASA

Stardust-NeXT is a repurposed spacecraft. The Valentine’s Day encounter will be the last hurrah for the aging probe. Stardust was originally launched way back in 1999. It flew by Comet Wild 2 on Jan. 2, 2004 and collected cometary dust particles which were returned to Earth in a sample return capsule in Jan. 2006. Since then it has continued its solitary voyage through the void of the space.

The craft is nearly out of fuel and all movements consume fuel. It is totally dependent on the reaction control thrusters for navigating through space and pointing its camera and science instruments, said Larson.

“We are confident that we will have enough fuel to finish up this mission. It has been a big, big challenge to maintain a reserve supply. After the mission there won’t be much left that the spacecraft can do. The last trajectory correction maneuver is two days before arrival. That is also when we will take our last optical navigation images for targeting the spacecraft.”
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Only about a third of the surface of Tempel 1 was photographed by Deep Impact in 2005. “We’ll be looking at old territory and new and some overlap,” explained Veverka. “The science team is awfully excited and just can’t wait to see the pictures on Valentine’s day.”

“We have no idea how quickly the surface features change and whether its millions of years or days,” concluded Veverka.

“We expect new discoveries no matter what we see,” Larson summed up

Stardust-NExT Spacecraft & Comet Tempel 1. Artist rendering of Stardust-NExT spacecraft nearing Comet Tempel 1 for upcoming flyby on February, 14, 2011. Credit: NASA
See video and graphics below of Jan 19, 2011 Media briefing from the Science Team about plans for the cometary encounter
Planned imaging of Comet Tempel 1 by Stardust-NExT during flyby. Blue area is unseen and unmapped territory never imaged by Deep Impact during 2005 flyby. Bulls eye in yellow area is expected location of 2005 impact crater and expected new coverage. There is some overlap. Credit: NASA
Planned imaging of Comet Tempel 1 by Stardust-NExT during flyby. Blue area is unseen and unmapped territory never imaged by Deep Impact during 2005 flyby. Credit: NASA

Jan. 19, 2010: Science Team Media Briefing

The Stardust spacecraft has been repackaged for the Stardust-NexT mission. Stardust-NExT will rendezvous with Comet Tempel 1 on February 14, giving scientists an opportunity, for the first time, to search a comet’s surface for changes following its orbit around the sun. Mission scientists discussed the relevance of the mission at a briefing at NASA headquarters in Washington

Stardust successful original mission was to fly by Comet Wild 2 on Jan 2, 2004 and return cometary dust particle to earth in Jan. 2006. It is equipped with 3 science instruments. Credit: NASA

Posted on by Ken Kremer

35 Days to STARDUST-NeXT Valentines Day Flyby of Comet Tempel 1

Stardust-NExT Spacecraft & Comet Tempel 1. Artist rendering of Stardust-NExT spacecraft nearing comet Tempel 1.

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35 Days and Counting !

NASA’s re-purposed STARDUST- NeXT spacecraft is set to flyby Comet Tempel 1 at a distance of just 200 km on Valentine’s Day – February 14, 2011 at about 8:36 p.m. PST. The encounter marks the first time that a comet has been visited twice by probes from Earth. The revisit also provides the first opportunity for up-close observations of a comet both before and after a single orbital pass around the sun.

Comet Tempel 1 was first visited by NASA’s Deep Impact comet smashing mission in July 2005. Deep Impact delivered a 375 kg projectile into the path of Temple 1 that resulted in a high speed impact directly into the comet nucleus.

The cosmic collision of about 10.2 km/sec (22,800 miles/hour) ejected a cloud of debris that was studied by the Deep Impact spacecraft as well as an armada of orbiting and ground based telescopes. The impact crater itself was obscured by the debris cloud. The spacecraft did find the first evidence of surface ice on a comet instead of just inside a comet. Stardust NExT will take images and spectra of Tempel 1 and hunt for the impact crater.

Artists concept of NASA’s STARDUST- NeXT probe which will fly by Comet Tempel 1 on Feb. 14, 2011. Credit: NASA

According to the latest update posted at the STARDUST- NeXT mission website on Jan 6; “The spacecraft is healthy and began the New Year with a cold boot to clear a memory address latch-up that had occurred late in 2010. This cold boot clears the latched line and resets the memory to its factory settings.”

The reboot was completely successful and sets the probe up to accomplish the missions science objectives. On board optical navigation cameras were scheduled to take a new set of images on Jan. 6.

The update further states that the mission plan has now changed substantially to accommodate two new challenges. First the estimated fuel remaining on board is lower than expected. Second, the optical navigation cameras failed to detect the comet in the prior set of images in December.

10 Jan. 2011 Position of STARDUST-NeXT probe - Looking Down on the Sun. This image shows the current position of the STARDUST spacecraft and the spacecraft's trajectory (in blue) around the Sun. Credit: NASA

The optical cameras provide the key information to precisely navigate the probe to the comet. “Current estimates show that the comet may not be bright enough to detect with the Navcam until the latter half of January,” states the update.

As a result of the lower fuel estimate the remaining trajectory maneuvers (TCM’s) have been adjusted to January 31, February 7, and February 12. No science images will be taken until the last 7 days prior to the Feb 14 encounter.

Caption: Video of Comet Tempel 1 as NASA’s Deep Impact comet spacecraft delivers a projectile which smashed into the comet in July 2005. NASA’s STARDUST- NeXT probe is set to flyby Comet Tempel 1 on February, 14, 2011. The probe will collect numerous high resolution images of the coma and nucleus and hunt for the elusive 2005 impact crater.

The team states that these changes will provide “positive fuel margin through encounter …. and places the TCMs at times best able to accommodate late detection of the comet”.

The engineering team is building new approach sequences to accommodate these significant changes to the approach and Comet Tempel 1 encounter on Feb 14.

A briefing by the science team will be carried live on NASA TV on Jan. 19 at 2 PM EST

The Stardust spacecraft accomplished its original goal of flying through a dust cloud surrounding the nucleus of comet Wild 2 in Jan. 2004. The probe successfully gathered particles of cometary material during the flyby, The comet particles were returned to Earth aboard a sample return capsule which landed in the Utah desert in January 2006.

Comet particle tracks in aerogel returned to Earth by STARDUST in January 2006
Posted on by Nancy Atkinson

SOHO Finds Its 2000th Comet

Image Left: SOHO's 2000th comet, spotted by a Polish amateur astronomer on December 26, 2010. Credit: SOHO/Karl Battams. Image Right: In 15 years since it launched in December 1995, the SOHO spacecraft, has doubled the number of comets sighted in the three hundred years previously. Credit: NASA/ESA/Alex Lutkus

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From a NASA Press Release:

As people on Earth celebrate the holidays and prepare to ring in the New Year, an ESA/NASA spacecraft has quietly reached its own milestone: on December 26, the Solar and Heliospheric Observatory (SOHO) discovered its 2000th comet.

Drawing on help from citizen scientists around the world, SOHO has become the single greatest comet finder of all time. This is all the more impressive since SOHO was not specifically designed to find comets, but to monitor the sun.

“Since it launched on December 2, 1995 to observe the sun, SOHO has more than doubled the number of comets for which orbits have been determined over the last three hundred years,” says Joe Gurman, the U.S. project scientist for SOHO at NASA’s Goddard Space Flight Center in Greenbelt, Md.

Of course, it is not SOHO itself that discovers the comets — that is the province of the dozens of amateur astronomer volunteers who daily pore over the fuzzy lights dancing across the pictures produced by SOHO’s LASCO (or Large Angle and Spectrometric Coronagraph) cameras. Over 70 people representing 18 different countries have helped spot comets over the last 15 years by searching through the publicly available SOHO images online.

The 1999th and 2000th comet were both discovered on December 26 by Michal Kusiak, an astronomy student at Jagiellonian University in Krakow, Poland. Kusiak found his first SOHO comet in November 2007 and has since found more than 100.

“There are a lot of people who do it,” says Karl Battams who has been in charge of running the SOHO comet-sighting website since 2003 for the Naval Research Lab in Washington, where he also does computer processing for LASCO. “They do it for free, they’re extremely thorough, and if it wasn’t for these people, most of this stuff would never see the light of day.”

Battams receives reports from people who think that one of the spots in SOHO’s LASCO images looks to be the correct size and brightness and headed for the sun – characteristics typical of the comets SOHO finds. He confirms the finding, gives each comet an unofficial number, and then sends the information off to the Minor Planet Center in Cambridge, Mass, which categorizes small astronomical bodies and their orbits.

It took SOHO ten years to spot its first thousand comets, but only five more to find the next thousand. That’s due partly to increased participation from comet hunters and work done to optimize the images for comet-sighting, but also due to an unexplained systematic increase in the number of comets around the sun. Indeed, December alone has seen an unprecedented 37 new comets spotted so far, a number high enough to qualify as a “comet storm.”

LASCO was not designed primarily to spot comets. The LASCO camera blocks out the brightest part of the sun in order to better watch emissions in the sun’s much fainter outer atmosphere, or corona. LASCO’s comet finding skills are a natural side effect — with the sun blocked, it’s also much easier to see dimmer objects such as comets.

“But there is definitely a lot of science that comes with these comets,” says Battams. “First, now we know there are far more comets in the inner solar system than we were previously aware of, and that can tell us a lot about where such things come from and how they’re formed originally and break up. We can tell that a lot of these comets all have a common origin.” Indeed, says Battams, a full 85% of the comets discovered with LASCO are thought to come from a single group known as the Kreutz family, believed to be the remnants of a single large comet that broke up several hundred years ago.

The Kreutz family comets are “sungrazers” – bodies whose orbits approach so near the Sun that most are vaporized within hours of discovery – but many of the other LASCO comets boomerang around the sun and return periodically. One frequent visitor is comet 96P Machholz. Orbiting the sun approximately every six years, this comet has now been seen by SOHO three times.

SOHO is a cooperative project between the European Space Agency (ESA) and NASA. The spacecraft was built in Europe for ESA and equipped with instruments by teams of scientists in Europe and the USA.

For more information see the SOHO website. .

See SOHO realtime data.

Posted on by Mike Simonsen

Asteroid Scheila Sprouts a Tail and Coma

(596) Scheila, the asteroid with a tail. Image credit: Peter Lake

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When is an asteroid not an asteroid? When it turns out to be a comet, of course. Has this ever happened before? Why, yes it has. In fact it was just announced December 12, 2010 that the asteroid (596) Scheila has sprouted a tail and coma! This is likely a comet that has been masquerading as an asteroid.

Taken from New Mexico Skies between 8h15m and 11h45m UT. The image is a stack of 10 x 600 sec exposures using a 20 inch RCOS and STL11K camera. Scale is 0.91 asec/px.. Image courtesy of Joseph Brimacombe

See an animation by Joseph Brimacombe at this link.

Steve Larson of the Lunar and Planetary Laboratory (LPL), University of Arizona first reported that images of the minor planet (596) Scheila taken on December 11th showed the object to be in outburst, with a comet-like appearance and an increase in brightness from magnitude 14.5 to 13.4. The cometary appearance of the object was confirmed by several other observers within hours.

A quick check of archived Catalina images of Scheila from October 18, November 2 and November 11 showed Scheila to look star-like, which is what asteroids look like from Earth. They just happen to be moving across the field of view in contrast to the fixed background stars. The image taken by Catalina on December 3rd shows some slight diffuseness and an increase in overall brightness. So, it appears this event began on or around December 3rd.

Upon hearing the news, there was some speculation that this might be evidence of an impact event. Had something crashed into asteroid Scheila? It seems unlikely, and this is a story we have heard before.

The asteroid discovered in 1979 and named 1979 OW7 was lost to astronomers for years and then recovered in 1996. It was subsequently renamed 1996 N2. That same year it was discovered to have a comet-like appearance, and many believed this was the signature of an impact between two asteroids. After years of inactivity 1996 N2 sprouted a tail again in 2002. One collision between two asteroids was unlikely enough. The odds of it happening again to the same object were essentially zero. What we had was a comet masquerading as an asteroid. This object is now known by its cometary name 133P/Elst-Pizarro, named after the two astronomers who discovered its initial cometary outburst.

The 2002 outburst and the discovery of more active asteroids showing mass-loss led to a paper (Hsieh and Jewitt 2006, Science, 312, 561-563) introducing an entirely new class of solar system objects, Main Belt Comets (MBC). MBCs look like comets because they show comae and have tails but they have orbits inside Jupiter’s orbit like main belt asteroids.

The most likely cause of the mass loss activity in MBCs is sublimation of water ice as the surface of the MBC is heated by the Sun. This is suggested most strongly by the behavior of the best-studied example, namely 133P/Elst-Pizarro. Its activity is recurrent, and it is strongest near and after perihelion, the point in its orbit nearest the Sun, like other comets.

MBCs are interesting to astronomers because they appear to be a third reservoir of comets in our solar system, distinct from the Oort cloud and Kuiper belt. Since we know of no way for these other reservoirs to have deposited comets in the inner solar system, the ice in MBCs probably has a different history than the ice in the outer comets. This allows researchers to study the differences in the Sun’s proto-planetary disk at three separate locations. This might lead to information on the Earth’s oceans, one of the continuing lines of investigation by solar system scientists.

Now it seems we have another MBC to add to the sample. And Scheila will probably be getting a new name soon. Asteroid (596) Scheila was discovered Feb. 21, 1906, by A. Kopff at Heidelberg. The 113Km in diameter ‘asteroid’ was named after an acquaintance, an English student at Heidelberg. In the future it will be called XXXP/Lawson or something similar, and Kopff’s Scheila will become just another footnote in the history of astronomical nomenclature.

Posted on by Nancy Atkinson

Fizzy Comet Hartley 2 is Throwing Snowballs

This 3-D image shows the entire nucleus of Hartley 2 with jets and an icy particle cloud. Circles have been added to highlight the location of individual particles. Image Credit: NASA/JPL-Caltech/UMD/Brown

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As Jessica Sunshine said, Comet Hartley 2 might be the smallest of the five comets that our spacecraft have visited, but no doubt it is the most interesting, and for its size, the most active. Sunshine is the EPOXI mission deputy principal investigator, and she and her team have had the chance to analyze images from the Nov. 4 flyby of the comet. Closeup views yielded some big surprises: Hartley 2 is throwing snowballs.

“When we first saw all the specks surrounding the nucleus, our mouths dropped,” said Pete Schultz, EPOXI mission co-investigator at Brown University. “Stereo images reveal there are snowballs in front and behind the nucleus, making it look like a scene in one of those crystal snow globes.”

Estimates of the size of the largest particles ranges from a golf ball to a basketball.

Another surprise, which was noted almost immediately from the flyby images, were that the very active jets on the comet were powered by carbon dioxide. “This is the first time we’ve ever seen individual chunks of ice in the cloud around a comet or jets definitively powered by carbon dioxide gas,” said Michael A’Hearn, principal investigator for the spacecraft. “We looked for, but didn’t see, such ice particles around comet Tempel 1,” the comet that the Deep Impact spacecraft flew by in 2005.

Here are highlights from the press conference last week, along with some of the fantastic imagery of Comet Hartley 2.

Hartley 2 CO2 jet up close. Credit: NASA/JPL-Caltech/UMD/Brown
Comet Hartley 2 can be seen in glorious detail in this image from NASA's EPOXI mission. It was taken as the spacecraft flew by around 6:59 a.m. PDT (9:59 a.m. EDT), from a distance of about 700 kilometers (435 miles). The comet's nucleus, or main body, is approximately 2 kilometers (1.2 miles) long and .4 kilometers (.25 miles) at the 'neck' or most narrow portion. Jets can be seen streaming out of the nucleus. Image credit: NASA/JPL-Caltech/UMD
This image from the High-Resolution Instrument on NASA's EPOXI mission spacecraft shows part of the nucleus of comet Hartley 2. The sun is illuminating the nucleus from the right. A distinct cloud of individual particles is visible. This image was obtained on Nov. 4, 2010, the day the EPOXI mission spacecraft made its closest approach to the comet. Image Credit: NASA/JPL-Caltech/UMD
Infrared scans of comet Hartley 2 by NASA's EPOXI mission spacecraft show carbon dioxide, dust, and ice being distributed in a similar way and emanating from apparently the same locations on the nucleus. Water vapor, however, has a different distribution implying a different source region and process. Image Credit: NASA/JPL-Caltech/UMD
This zoomed-in image from the High-Resolution Instrument on NASA's EPOXI mission spacecraft shows the particles swirling in a 'snow storm' around the nucleus of comet Hartley 2. Scientists estimate the size of the largest particles ranges from a golf ball to a basketball. They have determined these are icy particles rather than dust. The particles are believed to be very porous and fluffy. Image Credit: NASA/JPL-Caltech/UMD
The motion of some icy particles in the cloud around Hartley 2, as seen by NASA's EPOXI mission spacecraft. A star moving through the background is marked with red and moves in a particular direction and with a particular speed, while the icy particles move in random directions. The icy particles are marked in green, blue and light blue. Image Credit: NASA/JPL-Caltech/UMD/Brown
This image shows the nuclei of comets Tempel 1 and Hartley 2, as imaged by NASA's Deep Impact spacecraft, which continued as an extended mission known as EPOXI. Tempel 1 is five times larger than Hartley 2. Visible jets are easily seen in images of Hartley 2, but required extensive processing to be seen in images of Tempel 1. Tempel 1 is 7.6 kilometers (4.7 miles) in the longest dimension. Hartley 2 is 2.2 km (1.4 miles) long. The Tempel 1 image was built up from more than 25 images captured by the impactor targeting sensor on July 4, 2005. The Hartley 2 image was obtained by the Medium- Resolution Imager on Nov. 4, 2010.
Posted on by Tammy Plotner

Dances With Comets – C/2010 V1 Ikeya Murakami

For those of you working on your Comet Hunter’s certificates – or for those who just love these travelers from the Oort Cloud – there’s a new partner in the morning sky. Say hello to C/2010 V1 Ikeya Murakami! If you’re familiar with how a comet looks and already know the steps, then let the easiness lure you out. However, if you’ve never danced with a comet before, then come inside and we’ll teach you the steps…

Our first teacher is John Chumack of Galactic Images who sent us the lead picture for this article. Not all comets jump right out of the sky at you, and some require you wait for just the precise moment in time to catch it. As John says, “I had a very short window to grab it. I could not take more shots due to Dawn rising fast! But I did get very nice details… and it is sporting a little red tail, and a great bow shock!” As you can read, even just a few moments are worth it and the clue here is that Comet Ikeya Murakami isn’t in the easiest of places for most observers. How about if we find out exactly where to look?

Follow the green brick road! This morning comet Ikeya Murakami would have been a same field object with Saturn and it’s headed toward Venus. How easy can it get? Simply aim your binoculars at Saturn and slowly follow the trajectory towards Venus. By November 30 Ikeya Murakami will be about 2 degrees north of the stunningly bright planet and also a same field object in most binoculars.

So, what would the comet be like to watch for awhile? First off, remember that what you will see in binoculars and a small telescope will resemble a small, unresolved globular cluster. It will be a faint fuzzy with a faint tail. More aperture will help, but the approaching Sun is the real culprit here. Comet C/2010 V1 Ikeya Murakami won’t be terribly bright, but you might catch other interesting things while you watch, too. Just ask the one and only Joe Brimacombe!

If you don’t catch C/2010 V1 Ikeya Murakami on the first try – don’t be disappointed… And try again! (the “Aqua” Man would.) But don’t wait too long because the Moon is going to be along soon, making morning skies even brighter. If you do catch it, be sure to share your impressions with us…

Cuz’ there ain’t nothin’ like a little dance before dawn.

Posted on by Nancy Atkinson

Hartley 2 in Motion: Stunning Morph Animation of Flyby Images

The folks from UnmannedSpaceflight.com have done it again. Daniel Machácek created this wonderful animation from just the five initial images of Hartley 2 that were released by the Deep Impact team immediately following its flyby on November 4, 2010, using Sqirlz Morph software. Time in the animation is five times faster than the actual speed of the flyby. Hartley 2 really does look like a flying bowling pin, except this one is 2km (1.25 miles) long and about .2 km in diameter. Thanks to Daniel for sharing his animation.

Posted on by Nancy Atkinson

First Close Images of Hartley 2: It’s a Peanut with Jets

Comet Hartley as seen by the EPOXI spacecraft at closest approach. Credit: NASA

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NASA’s Deep Impact spacecraft came within 700 kilometers (435 miles) of Comet Hartley 2 at 10:01 a.m. EDT (1401 GMT) today, imaging with several cameras. Here are the first pictures released of the closest approach.

The scientific team watched along with viewers online and on NASA TV as the images were returned to Earth, about an hour after the spacecraft made its closest approach. First impressions? It is a peanut with jets.

“This is a type of moment that scientists live for,” said JPL’s Don Yeomans, “to get new results in such a dramatic fashion. The images are clear, taken as spacecraft was approaching, then as it swung past and moved away.”

The Sun is off to right, and visible is the icy surface of the comet throwing dust and gas towards the Sun.


Another view of Comet Hartley 2 during EXPOXI close approach. Credit: NASA

More images will be coming down from the spacecraft and Yeomans said the scientists will be examining Hartley 2, looking for the origination spots of the jets. “Are the jets coming from the surface, or is it coming from well beneath where heat of Sun reaches into the comet? We’ll be looking for how many jets, or if possibly the whole comet outgassing. There is a single obvious jet coming off towards the Sun, but also you can see one at the 7 o’clock position, which was evident in previous images, too.”

Image of Hartley 2 as the EXPOXI spacecraft moved away from comet. Credit:NASA

The spacecraft uses several high-resolution instruments, and one camera can image the entire comet with a resolution of about seven meters (about 23 feet) per pixel. The spacecraft also acquired 199 medium-resolution images.

From previous images taken by EPOXI from a distance and radar images taken from the ground, scientists knew Hartley 2 was a bi-lobate comet, which means peanut- or pickle-shaped. But they didn’t know if it was a solid surface or a contact binary, where two smaller cometesimals were stuck together.

But, Yeomans said, these images show the comet is of a solid, one-piece construction.

EPOXI Principal Investigator Mike A’Hearn agreed. “Every time we go to a comet they are full of big surprises,” he said. “The comets we’ve seen up close all seem to work the same way, but they look very different so there must be some fundamental differences in the ways they work. It could be they came from different parts of the early solar system or that they evolved very differently. Finding out how the solar system formed is really what we want out of this.”

The discoverer of Hartley 2, Malcolm Hartley, was on hand at JPL for the closest approach. He found the comet 26 years ago as a smudge on photographic plates taken at the Siding Spring Observatory in Australia. “I was doing quality control of photographic plates and I noticed faint object with a telltale glow like a comet,” said Hartley, who still works at the same observatory. “It has been very interesting to be here, and it has been interesting for the science team and quite a challenge for the engineers. There’s going to be enough data downloaded to keep researchers busy for several years.”

See the EPOXI website for more images, and more will be coming down from the spacecraft over the next few days.

To see a “quick and dirty” animation of the flyby images, see this link provided by Doug Ellision of Unmanned Spaceflight.com (and JPL).

Posted on by Jon Voisey

Hartley 2 Spawns Meteor Shower

Universe Image Gallery

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The comet of the year for 2010 seems to be Hartley 2. Although this comet is receding from Earth now (its closest approach was in the latter half of October) and growing fainter, it seems to have left us with one last hurrah: The spawning a brief meteor shower.


Although other comets, such as 2009 R1 (McNaught) and 2P/Encke have passed earlier this year, none has presented an especially tempting target for amateur astronomers (both McNaught and Encke were too close to the Sun during perihelion to be easily observed). Additionally, Hartley is the target of a flyby of the Deep Impact probe bringing it further attention.

Meanwhile, observationally, the comet has been somewhat difficult to observe. I went out on October 17th to hunt for it with a 4″ telescope, but despite my best efforts, couldn’t find it. Although the comet was predicted to reach 5th magnitude, the growing nucleus has apparently become so diffuse, reaching over 1° in the sky, that it’s hard to spot. Undeterred, I attempted again this past weekend with my 8″ SCT. Again, my attempts were frustrated. Even a 15 second exposure with my camera barely brought out more than a smudge.

Yet that night we observed several bright meteors radiating from near Cassiopeia which is where Hartley had been a few weeks prior. We checked to ensure there weren’t any other annual meteor showers from that region. Sure enough, there weren’t, and we wondered if there might be a connection between Hartley’s passing and the meteors we witnessed.

Sure enough, just such a shower was a predicted possibility. Whether or not the shower would occur would depend on just how much dust Hartley had given off in the past and how diffuse the cloud had grown (on this pass and others) since its closest approach to Earth was still 12 million km. Although the meteors my friends and I witnessed were notable (around 2nd to 3rd magnitude) they came from the wrong direction. Meteors spawning from Hartley should have a radiant in Cygnus, the swan. But while ours may not have caught these “Hartley-ids”, others have been witnessing a far grander show in the past few nights that seem to come from the right direction.

In Seascape California, Helga Cabral caught a bright fireball. “I saw a bright white ball and tail, arcing towards the ocean. It was quite beautiful and it looked like it was headed out to sea and so picture perfect it could have been a movie!” A similar fireball was reported the same night near Boston, Massachusetts by Teresa Witham. The predicted peak of this shower occurs tonight so if you have a chance and clear skies, go out and look. As with most showers, there may be some stragglers just before and after so you may be able to catch some for the next few nights if conditions tonight aren’t favorable.

Meteors from Hartley 2 will have a relatively low velocity upon entering our atmosphere since the comet is traveling roughly in the same direction. As such, the expected velocity as it hits our planet is a mere 7 miles a second. The result of this is that they will likely travel slowly across the sky, taking perhaps as much as a few seconds. In contrast, the Leonid showers coming later this month have a relative velocity of 45 miles per second, which causes the meteors to streak across the entire sky in less than a second. The lower velocity for the Hartley-ids will also mean they won’t undergo as much frictional heating and will likely glow fainter shades of reds and yellows.