The Flight of Comet Hartley 2
The video of comet Hartley 2 was shot thanks to images taken by NASA's EPOXI probe on November 4, 2010.
The spacecraft and the comet found themselves at a speed of 12.3 kilometers per second (27.56 miles per hour) and the spacecraft was about 700 kilometers (435 miles) from the comet's core at the time. of the closest approach.
The video was processed using material from NASA, the American space agency.
This week a fairly bright comet is visible in the northeastern sky and makes its closest approach to Earth tomorrow (Oct. 20), though it may be difficult to spot without clear conditions well away from city lights.
For a few nights at mid-week, Comet 103P / Hartley 2 will be perfectly placed in the bright circle of stars that form the constellation Auriga.
This sky map shows where to look to spot the comet, weather and lighting conditions permitting. Binoculars or a small telescope are advised to obtain the best viewing conditions.
Rare comet encounter
Bright comets are rare, perhaps one every three to five years. It's impossible to tell far in advance how bright a comet may be.
Comet Hartley 2 was discovered by Australian astronomer Malcolm Hartley 24 years ago. Its only in the last few days that it has become bright enough to be spotted with binoculars or the naked eye.
This SPACE.com Comet Hartley 2 skywatching guide describes how to see the celestial event.
It is best viewed with 10x50 to 20x80 binoculars from a dark sky location. If using a telescope, choose the lowest magnification possible.
Like the famous Halley's Comet, Comet Hartley 2 is a periodic comet that follows a years-long loop around the sun. It takes 6.46 years to complete one circuit, compared with Halleys 75.3 years.
Comet's close approach
Unlike some comets, Hartley 2 never crosses the Earths orbit, so it is high in the night sky when it makes its closest approach. It will be closest to the Earth on Oct. 20 at 3 p.m. EDT (1900 GMT), and closest to the sun on Oct. 28.
At its closest, Comet Hartley 2 will be only 0.12 astronomical units (11 million miles, or 18 million km) from the Earth.
Because we are seeing this comet pretty much "head on" with the sun behind us, it has little or no detectable tail. It appears as a large diffuse glow in the sky. [New Photos of Comet Hartley 2]
On Nov. 4, this comet will have a visitor from Earth, when the probe Deep Impact does a flyby. It will pass only 435 miles (700 km) from Comet Hartley 2.
Comet Hartley 2 is a small Jupiter-family comet having an orbital period of 6.46 years. It was discovered by Malcolm Hartley in 1986 at the Schmidt Telescope Unit, Siding Spring Observatory, Australia. It has the perihelion near the Earth's orbit at 1.05 AU from the Sun. 
The comet passed within 0.12 AU (18,000,000 km 11,000,000 mi) of Earth on 20 October 2010,  only eight days before coming to perihelion (closest approach to the Sun) on 28 October 2010.  From northern latitudes, during early November 2010, the comet was visible around midnight without interference from the Moon. 
Despite its current close passage by Earth's orbit, the comet is not yet a known source of meteor showers. However, that could change. Dust trails from the recent returns of 103P / Hartley 2 move in and out of Earth's orbit, and the 1979-dust trail is expected to hit in 2062 and 2068. 
After the 2010 perihelion passage, not accounting for nongravitational forces, Hartley 2 is estimated to come back to perihelion around 20 April 2017. 
Observation by the Spitzer Space Telescope in August 2008 showed the comet nucleus to have a radius of 0.57 ± 0.08 kilometers (0.354 ± 0.050 mi) and a low albedo of 0.028.  The mass of the comet is estimated to be about 300 megatonnes (3.0 × 10 11 kg).  Barring a catastrophic breakup or major splitting event, the comet should be able to survive up to another 100 apparitions (
700 years) at its current rate of mass loss. 
Radar observations by the Arecibo Observatory during the comet's 2010 apparition revealed that the nucleus is highly elongated and rotates over an 18-hour period. The project manager of the EPOXI mission described its shape as "a cross between a bowling pin and a pickle". 
In 2011 Herschel Space Observatory detected the signature of vaporized water in the comet's coma. Hartley 2 contains half as much heavy water as other comets analyzed before, with the same ratio between heavy water and regular water as found in Earth's oceans.  
For many years, it was known that few comets produced more water vapor than it should by the redirection of nucleus of water ice. The flyby of Hartley 2 showed that many of the icy grains in the coma are driven out by the outgassing of carbon dioxide. It is believed that this is the source of much of the water coming from the comet.
Observations of Hartley 2 showed the importance of carbon-monoxide ice to carbon-dioxide ice in comets. After a reexamination, it was found that the abundances of carbon-monoxide ice and carbon dioxide ice show that short-period comets formed under warmer conditions, than the longer period comets. This shows that the short-period comets formed closer to the Sun, than the long-term comets. This discovery goes well with the measurements of Heavy Water in Hartley 2. 
The EPOXI mission flyby showed that the material being ejected from the comet is primarily composed of CO
2 gas. Michael A'Hearn, the science team leader for the EPOXI mission, stated "Early observations of the comet show that, for the first time, we may be able to connect activity to individual features on the nucleus". 
A University of Maryland-led study published in the 17 June issue of the journal Science described an analysis of the mission. Key findings from the mission include: (1) the smooth, relatively inactive waist of the peanut shaped comet has probably been re-deposited (2) Hartley 2 spins around one axis, but also tumbles around a different axis and (3) on its larger, rougher ends, the comet's surface contains glittering, blocky objects that are about 165 feet (50 meters) high and 260 feet (80 meters) wide (as big as a 16-story building). Moreover, these objects appear to be two to three times more reflective than the surface average.
"Hartley 2 is a hyperactive little comet, spewing out more water than other comets its size", said University of Maryland Astronomer Michael A'Hearn, who is lead author on the Science paper and principal investigator for the EPOXI and Deep Impact missions. "When warmed by the Sun, dry ice [frozen carbon dioxide] deep in the comet's body turns to gas jetting off the comet and dragging water ice with it."
It is now believed that some of the dust, icy chunks, and other material coming off the ends of the comet are moving slowly enough to be captured by even the weak gravity of the comet. This material then falls back into the lowest point — the middle.  
The Deep Impact spacecraft, which had previously photographed Comet Tempel 1, is now being reused by NASA to study Hartley 2. The initial plan was for a flyby of Comet Boethin. However, Boethin had not been observed since 1986, and its orbit could not be calculated with sufficient precision to permit a flyby, so NASA re-targeted the spacecraft toward Hartley 2 instead.  The spacecraft came within 435 miles (700 km) while moving at 27,500 miles per hour (44,300 km / h) on 4 November 2010.  The data from the flyby were transmitted back to Earth through NASA's Deep Space Network. 
The flyby was able to show that the comet is 2.25 kilometers (1.40 mi) long, and "peanut shaped". Some jets of material are being ejected from the dark side of the comet, rather than the sunlit side. Scientists involved in the EPOXI mission describe the comet as being unusually active, with mission scientist Don Yeomans stating that "It's hyperactive, small and feisty." 
NASA's scientists reported that the rays coming off the rough ends consist of hundreds of tons of fluffy ice and dust chunks - the largest particles are of golf ball to basketball-size - and they are ejected by jets of carbon dioxide.  The scientists also said that this is the first time that comet activity powered by sublimation of frozen carbon dioxide is observed as the comet nears the sun the CO
2 ice within the comet must be primordial, dating from the beginnings of the solar system. 
Malcolm Hartley has seen a whole lot of the universe over the last 40 years, but he'd never had a close-up view of a comet named after him.
›Browse version of image
-> Over the last 40 years, Malcolm Hartley has done just about every possible job for Siding Spring Observatory's UK Schmidt telescope in New South Wales, Australia. The British-born, Scottish-educated Hartley has logged time as the 1.2 meter (3.9 foot) telescope's observer, processor, copier, hypersensitization expert, and quality controller.
On the afternoon of March 16, 1986, Hartley's job was that last one - quality control. In that role, he was the first to view each 36-by-36 centimeter (14-by-14 inch) photographic glass plate after it had been exposed to the night sky. Checking for imperfections on one of the previous evening's 60-minute illuminations, Hartley came upon something that wasn't supposed to be there.
"Back then, the observations came in as negatives - stars and other objects in the sky appeared black on a clear background," said Hartley. "I noticed a dark haze around a trail. Trails indicate something that is traveling fast through the sky, but asteroids don't have a haze. So I thought it might be a comet."
Hartley double-checked his sighting a couple of nights later, then submitted his findings to the Minor Planet Center in Cambridge, Mass. A couple of days after that, the center issued a brief circular informing the astronomical world of the discovery of comet Hartley 2 .
"I was very happy for a couple of days," said Hartley. "Every scientist wants to discover something and it's a fantastic feeling. There was even a mention in the local paper, the Coonabarabran Times."
On the world's stage, having a comet named after you is certainly unique. But not so much in the small town of Coonabarabran - which they say comes from the local Aboriginal word for 'inquisitive person.' It is the closest town to the Warrumbungle Range and Siding Spring Mountain and the Anglo-Australian Observatory.
"There are several other colleagues at Siding Springs who have discovered comets," Hartley said. "Robert McNaught has discovered over 50, and I don't think he's ever been mentioned in the Times. It's a rural farming community, and while there are amateur astronomers in the area, finding comets is not really a big deal."
Hartley went on to discover or co-discover 10 comets with the UK Schmidt telescope, and with each, he would feel an initial rush of excitement. But in 2002, the Anglo-Australian Observatory retrofitted its Schmidt to perform multi-object spectroscopy, essentially halting all astrophotography with the telescope and ending any future possibility for comet discovery. Hartley, who never was directly tasked with finding comets, continued to work the telescope's galaxy surveys. Comets, it seemed, had become little more than a historical footnote in his career. That is, until he got a call from a science magazine.
"At the beginning of last year, a reporter emailed and said that the EPOXI mission changed its target and now it was going to go to Hartley 2," said Hartley. "I didn't even know Hartley 2 was one of the two comets under consideration."
Hartley 2 was definitely on NASA's very short list of potential comet targets. The only problem with Hartley 2 was it would take more than two years of extra deep-space cruising to get there. So the only other candidate on the short list, the similar-sized comet Boethin, was selected. That is, until it disappeared. Scientists theorize that comet Boethin had broken into non-traceable fragments. This situation left NASA's short list as a list of one - comet Hartley 2.
So Malcolm Hartley did what anybody would do who has a namesake comet that was just selected as a target for a NASA comet flyby, after the previous selection had disappeared. He thanked the reporter, logged off his computer and wondered what "his comet" would look like. Whatever that was going to be, Hartley was sure he would find out from the comfort of his living room. Then NASA called.
"I've never been involved with a space mission," said Hartley. "I had never visited JPL or any NASA facility for that matter. So this is all new to me. I am very grateful you have asked me to come and witness this. It is an experience very few people have had before."
Exactly once before - of all the approximately 3,800 known comets, four have been imaged closeup by spacecraft. And of those four, only Swiss astronomer Paul Wild (pronounced "Vilt") was alive to see his comet visited. And while Wild witnessed the launch of NASA 's Stardust spacecraft from Cape Canaveral, Fla., In 1999, he watched the close-up images of his comet from the comfort of his living room in 2003. (Wild passed away in 2008). Hartley will see his comet from JPL's mission control room.
"When I discovered the comet in 1986, I never envisaged that I would come to the location where the mission was run, to see it up-close and personal," said Hartley, who was a boy when JPL was starting up.
Not surprisingly, the 63-year-old astrophotographer also has some thoughts on the mission to his comet.
"You went to Tempel 1, but then you reconfigured the spacecraft for the extended mission," said Hartley. "That's pretty clever stuff that you've done. That's the kind of science that's really interesting. To be able to do something extra on top of the successful mission you mounted at Tempel 1, it's really special."
EPOXI is an extended mission that utilizes the already "in-flight" Deep Impact spacecraft to explore distinct celestial targets of opportunity. The term EPOXI is a combination of the names for the two extended mission components: the Extrasolar Planet Observations and Characterization (EPOCh), and the Hartley 2 flyby, called the Deep Impact eXtended Investigation (DIXI). For more information about EPOXI, visit: http://www.nasa.gov/epoxi and http://epoxi.umd.edu.
JPL, a division of the California Institute of Technology in Pasadena, manages the EPOXI mission for NASA.
|While the comet pueda ser un objetivo tentador para los telescopios, se le puede ver aquí con un seductor coma verdoso compartiendo seen with the nebulosa de emisión NGC 281 y las estrellas de la constelación de Casiopea el 2 de octubre.El perfil agujereado de la nebulosa definido por nubes de polvo en contraste a su rojizo resplandor sugieren un apodo más juguetón, the Pacman Nebula.|
|Photograph of comet Hartley 2 on the 28th of September of 2010 when it comes to 18 million millones of the Tierra.|
|Artistic concept of the Deep Impact probe.|
This video recoge the órbita of the comet alrededor del Sol y su trayectoria en el cielo.
El cometa transiting el doble cúmulo de Perseo.
Tránsito del comet por la constelación de Casiopea.
Encuentro de la nave EPOXI with Hartley 2.
Aproximación de EPOXI to comet Hartley 2.
The EPOXI ship observing a la Luna y a la Tierra.
Impressive gallery. I favor la segunda, pasandol el comet between el doble cúmulo de Perseo y la nebulosa del Corazón.
Una de las misiones espaciales mas emocionantes, was a compartido trabajo. entre los astrónomos aficionados viendo la llegada del cometa y los ingenieros de la nasa with the ship EPOXI, y no decepciono para nada el cometa. the EPOXI nos gift a de las imagenes mas claras de a comet. que al final de cuentas son restos del material original que form el sistema solar,
Y el vídeo final with el que cierras el articulo. es verdaderamente conmovedor, you - yo - Todos. estamos en esa hermosa esfera azul. hay que cuidarla!
Muchas gracias por este articulo. Muy bueno.
El cometa Hartley 2 from the dear
A NASA probe is approached at a distance of 700 kilómetros from the comet Hartley 2 para tomar fotografías and investigar de search the characteristics of this celestial cuerpo.
The llamada Deep Impact probe logro el mayor acercamiento posible al astro passing to one 44 mil kilómetros por hora a través de la cloud de gas y pulvo de la atmósfera que envuelve su núcleo.
According to NASA, to weigh the comet is relatively pequeño y holds only 2.2 kilómetros de largo es muy activo.
Los científicos esperan que la misión revele datos valiosos cómo los que consiguió hace cinco años when a proyectil disparado desde la nave se estrelló contra otro cometa, el Pempel 1, y pudo determine la existencia de al menos tres sectores con hielo en su núcleo.
The measurement of this probe, which took place on the 12th of January in 2005, is one of the most ambiciosas embodied for the agency espacial estadounidense.
Tim Larsen, manager of the project for the Observación y Caracterización de Planetas Extrasolares del Jet Propulsion Laboratory de la NASA, dijo que los científicos estaban "esperando lo inesperado".
"Cada vez que vuela por un comet estamos Amazidos con lo que vemos," dijo Larson. "Vemos cosas nuevas que nos obligan to plantear una gran cantidad de preguntas nuevas."
NASA cree important estudiar los cometas porque los astrónomos teorizan que this colección de gas, hielo, rocas y polvo formaron los planetas más lejanos de nuestro solar system hace unos 4,500 millones años. Algunos científicos dicen que los cometas originally llevaban un poco de agua y compuestos orgánicos that if transformaron en la vida de nuestro planeta.
If he trata de la quinta vez que an espacial ship he is suficiently seeks to photograph the core of a comet.
"This is a truly unique opportunity for acercamiento to have a direct comparison between those who are different and estudy who are characteristics that are in common and what are primordiales." dijo Larson.
El cometa Hartley 2 recibió su nombre de Malcolm Hartley, el astronomer who described it in 1986.
Comet Hartley 2 Fires Out Poison Gas as NASA Probe Nears
As a NASA spacecraft speeds toward its rendezvous tomorrow (Nov. 4) with Comet Hartley 2, the icy wanderer is putting on a show, blasting out gassy jets and coughing up loads of poisonous cyanide.
In less than 24 hours, the Deep Impact probe will cruise to within 435 miles (700 kilometers) of Hartley 2, marking just the fifth time that a comet has ever been observed up close. And the view should be interesting.
Last week, the spacecraft spotted two massive jets spewing from the comet's nucleus its core of ice and rock. Comet Hartley 2 also spat out huge quantities of cyanide over a week-long stretch in September, raising concentrations of the poisonous gas by a factor of five, researchers said. [Video of Comet Hartley 2 jets.]
"We're about to be surprised," said Mike A'Hearn of the University of Maryland, principal investigator of Deep Impact's mission, which NASA calls EPOXI. "This comet is unlike any we've visited before, and we don't know what we're going to find."
The encounter: How it should happen
Comet Hartley 2 is a small, active comet that orbits the sun once every 6 1/2 years. It was discovered in 1986 by Australian astronomer Malcolm Hartley. [Q&A with Comet Hartley 2 Discoverer]
The Deep Impact spacecraft has been chasing Hartley 2 for months, taking pictures and maneuvering to prepare for the close flyby, which is scheduled to take place at 10:01 a.m. EDT (1601 GMT) on Nov. 4.
Here's a brief rundown of how the flyby should proceed, if everything goes according to plan:
Later this evening (Nov. 3), about 18 hours before its closest approach, Deep Impact will begin the encounter phase of its mission. The probe will reorient itself so its three imagers two in the visible-light spectrum and one in the infrared can lock on Comet Hartley 2 for the next 24 hours-plus.
This maneuver will point the probe's high-gain antenna away from Earth, meaning Deep Impact won't be able to beam pictures home for a bit, researchers said. Instead, it will store the photos onboard in its two computers.
This lack of multitasking ability reflects the fact that Deep Impact is a recycled, repurposed spacecraft. It was originally designed to serve as a mother ship for NASA's Deep Impact mission, which intentionally crashed a probe into Comet Tempel 1 in 2005 to study the object's composition.
Soon after Deep Impact's closest approach with Hartley 2, mission scientists will reorient the probe so it can both track the now-receding comet and start beaming images to Earth.
The spacecraft will continue to take new photos while it sends its cache of comet close-ups home. The first few photos should reach researchers' computers about an hour or so after the rendezvous, scientists said. The complete data dump, however, will take a while.
"We will be waiting," A'Hearn said. "The best images won't reach Earth until many hours after the actual encounter." [The Best Comet Photos of All Time.]
Researchers should get some good looks at Comet Hartley 2. One of Deep Impact's cameras is so powerful that it can distinguish the size difference between a car and a pickup truck from 400 miles (645 km) away, mission scientists have said.
Data from the close approach will continue to download through Saturday (Nov. 6) but NASA will release preliminary results sooner than that. A news conference is scheduled for 4 p.m. EDT (2200 GMT) tomorrow (Nov. 4), just six hours after Deep Impact's closest approach to Hartley 2, agency officials said.
Post-encounter: Watching Hartley 2 speed away
Though Deep Impact will zoom by Comet Hartley 2 incredibly fast during the flyby at about 27,000 mph (43,548 kph) the spacecraft will be able to track the comet's tail end with just a slow swivel. The probe will turn about 1 degree per second, according to mission scientists one-sixth the rate at which a second hand makes its way around a clock face.
This anticipated ease of tracking is one reason mission planners chose to stay 700 kilometers away from the comet, rather than zip in for a closer, more detailed look.
Another reason: to keep Deep Impact away from the densest parts of Hartley 2's coma, the gassy, dusty cloud around its nucleus. Particles in the coma could damage Deep Impact's antenna if the probe gets too close.
"We've chosen 700 kilometers because we're balancing several desires and several threats here," explained EPOXI project manager Tim Larson, of NASA's Jet Propulsion Laboratory.
Deep Impact will continue photographing Hartley 2 for about three weeks as the comet speeds off into the dark reaches of space, Larson added. After that point, the spacecraft's comet-watching mission will be basically over.
What Comet Hartley 2 can reveal
Researchers hope Deep Impact's flyby past Hartley 2 can give them a good idea of the composition of the comet's icy nucleus. They are also eager to compare Hartley 2 to the four other comets that spacecraft have visited in the past.
Hartley 2, while just under a mile (1.5 km) across, is incredibly active. A close study of its spewing jets and gas clouds could yield clues about comet composition and behavior in general, researchers said.
"We saw outbursts in Comet Tempel 1, as well as many other things," A'hearn said. "We're trying to find out, are all of the new phenomena we saw at Tempel 1 universal across all comets, or are they special to Comet Tempel 1?"
Comets are leftovers from the solar system's formation 4.5 billion years ago, so studying them should give astronomers a better handle on how our cosmic neighborhood came to be, researchers said.
The 2005 kamikaze crash into Tempel 1 exposed what scientists think are primordial layers of matter dating back 4.5 billion years. EPOXI scientists hope an up-close look at Hartley 2 will reveal similar ancient material, perhaps providing key insights about our solar system's youth.
"That's the ultimate goal at the encounter," A'hearn said.
Video: Animation of the Comet Hartley 2. Enhanced Jets.