Earth to Lend Helping Hand to Comet Craft

NASA's Deep Impact/EPOXI spacecraft will fly past Earth this Sunday (June 27). Mission navigators have tailored this trajectory so the spacecraft can "hitch a ride" on Earth's gravity field, which will help propel the mission toward its appointment with comet Hartley 2 this fall. At time of closest approach to Earth, the spacecraft will be about 30,400 kilometers (18,900 miles) above the South Atlantic.

"Earth is a great place to pick up orbital velocity," said Tim Larson, the EPOXI project manager from NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This flyby will give our spacecraft a 1.5-kilometer-per-second [3,470 mph] boost, setting us up to get up close and personal with comet Hartley 2."

EPOXI is an extended mission of the Deep Impact spacecraft. Its name is derived from its two tasked science investigations -- the Deep Impact Extended Investigation (DIXI) and the Extrasolar Planet Observation and Characterization (EPOCh). On Nov. 4, 2010, the mission will conduct an extended flyby of Hartley 2 using all three of the spacecraft's instruments (two telescopes with digital color cameras and an infrared spectrometer).

The University of Maryland is the Principal Investigator institution. JPL manages EPOXI for NASA's Science Mission Directorate, Washington. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

Welcome Home, Hayabusa!

Hayabusa spacecraft reentry
The Hayabusa spacecraft breaks up in Earth's upper atmosphere
while its payload capsule (visible at far right) streaks on ahead.
This is one frame from a video; click above to see the whole thing.
NASA / Berman /Breitmeyer / Dantowitz / Kozubal

Welcome Home, Hayabusa!

In a thrilling tale of triumph over adversity, the Japanese probe Hayabusa slammed into Earth's atmosphere last night over Australia. The craft had suffered several crippling malfunction during its seven-year trip to and from asteroid Itokawa, the kind of misfortune that typically spells doom. Yet the brilliantly colored fireball that lit up last night's sky signaled a successful end to the mission.

There were actually two reentries. A few hours earlier a small capsule had separated from the main spacecraft; researchers hope that bits of Itokawa are sealed inside. The two were a few miles apart by the time they plunged through the atmosphere, with the capsule in the lead. Minutes later the capsule landed on target in the Woomera Protected Area, a desolate, 50,000-square-mile military test area about 500 miles northwest of Adelaide.

The main craft, which wasn't designed to survive, put on quite a show. It started breaking apart at an altitude of about 60 miles (90 km), each fragment seared to incandescence by atmospheric friction. Observers on the ground saw a range of vivid colors in the brilliant breakup, estimated to be magnitude –6. In less than 30 seconds, it was all over.

Best of all, I was there to see it! I'd traveled halfway around the world to work side-by-side with a NASA-led expedition of space researchers tracking the space spectacle. It's rare that a reentry happens at such high velocity (7½ miles per second versus the customary 5), so scientifically it was a big deal.

My six-person team was rare too. It included high-school students James Breitmeyer and Yiannis Karavas, both 17, and Brigitte Berman, 16. They attend the Dexter and Southfield Schools in Brookline, Massachusetts, where I teach part time. Over the past few months, Ronald Dantowitz begin_of_the_skype_highlighting end_of_the_skype_highlighting and Marek Kozubal from the schools' Clay Center Observatory helped these kids build tracking platforms crammed with high-end imaging cameras; ultraviolet, infrared, and visible light spectrographs; and an IMAX-quality high-definition video system for recording the reentry.

Most of this high-tech gear was aboard NASA's DC-8 research aircraft in Palmdale, California, alongside other instruments brought by researchers from Germany, the Netherlands, Japan, and several U.S. institutions. This airborne campaign had been orchestrated by Peter Jenniskens, a meteor specialist at the SETI Institute in California.

The plane then headed to Australia, and during Hayabusa's hypervelocity homecoming it followed a racetrack-shaped loop at an altitude of 41,000 feet near the landing zone. Breitmeyer, Berman, Dantowitz, and Kozubal carefully recorded the brightnesses and spectra of the sample capsule and pieces of the disintegrating main spacecraft as they plunged Earthward. In fact, the image shown above is from one of their cameras.

Meanwhile, Karavas and I were recording the brief but dramatic passage at ground level, from the mining town of Coober Pedy. Our images and spectra will be useful in calculating the exact trajectory of the incoming spacecraft. We gathered 12 gigabytes of data in under 3 minutes.

I'd seen the southern sky before — but never like this. The weather worries we'd had in the days beforehand evaporated when a cold front pushed through and delivered an impossibly transparent sky. The Milky Way stretched from horizon to horizon, with the starclouds of Sagittarius and Scorpius overhead, the Southern Cross and Coal Sack instantly recognizable, and the Magellanic Clouds hugging the horizon.

Now that the adrenaline rush from Hayabusa has come and gone, I'm hoping these vistas will still be in view later this evening, when I can set up my 80-mm f/5 refractor and do some much-anticipated stargazing.

Comet McNaught Brightening to Naked Eye Object

Skywatcher Michael Jäger of Stixendorf, Austria, took this photo of the
newfound comet McNaught C/2009 R1 on June 6, 2010, while the comet
was visible in the northeastern morning sky.
Credit: Michael Jäger

A recently discovered comet is surprising skywatchers by becoming brighter than predictions had first suggested and can now be seen with the unaided eye during the next few weeks. Comet McNaught, officially catalogued as C/2009 R1, was discovered by Australian astronomer Robert McNaught last September using the using the 0.5-meter Uppsala Schmidt telescope and a CCD camera. It's the 51st comet that bears McNaught's name.

Although initially an extremely faint object, enough observations of the newfound comet were made to allow Brian Marsden of the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, to calculate an orbit.

Comet McNaught is expected to pass closest to the sun (perihelion) on July 2, at a distance of 37 million miles (60 million km). This sky map shows where to look in order to spot the comet in the morning sky.

The comet is visible now for people with dark skies away from urban and suburban lighting. By mid-June it may be an easy skywatching target for most people.
Comets brighten when the get nearer to the sun, because solar radiation boils icy particles and dust off the comet's nucleus. A cloud of material called a head, or coma, and sometimes a tail form. It's all illuminated by reflected sunlight.

This recently discovered comet, McNaught C/2009 R1, should not be confused with another dazzling comet to bear McNaught's name – C/2006 P1 McNaught – which also put on a show for skywatchers in 2007 that was so stunning, it earned the moniker "Great Comet of 2007."

As comet McNaught approached the sun, amateur and professional astronomers worldwide watched with interest as it slowly increased in brightness.

When April began, the comet was estimated at magnitude +12. That's still about 250 times dimmer than the faintest star that one might see without any optical aid. But the comet started brightening more rapidly in the days and weeks that followed and it's now bright enough to be glimpsed with the naked eye in a dark clear sky.

The most recent "reliable" observation was made by Alexandre Amorim of Florianopolis, Brazil who saw the comet on June 6 using 10x50 binoculars and estimated the magnitude as +5.5. That's about as bright as the faintest star in the bowl of the Little Dipper (on this scale, smaller numbers represent brighter objects).

In the coming days, the comet is expected to continue to brighten as it gets closer to the sun.



When and where to see it
If you want to get a view of the comet, you'll have to get up early in the morning. Set your alarm clock for at least two hours before sunrise. For most people that will mean around 3:30 a.m. local time. The comet is currently moving through the constellation of Perseus, the Hero, which at that early hour will be low in the northeast part of the sky.

The comet will pass to the south of the second magnitude star, Mirfak around June 14. Both star and comet will be about 20-degrees above the northeast horizon (10-degrees is roughly equal to the width of your clenched fist held at arm's length; so the comet will be about "two fists" up from the horizon).

Don't expect anything spectacular just yet, however. The comet should appear as a dim and diffuse, circular patch of light. Binoculars or a small telescope will help to bring it out better; you might even make out a faint greenish color.

From the head of the comet, a narrow tail of gas extends. John Bortle, a well known comet observer, likens McNaught's appearance as resembling an "apple on a stick." "From the few rough magnitude estimates I have seen posted, it would appear that the comet is perhaps a magnitude brighter than had been anticipated, but whether this trend will continue is, as usual, anybody's guess," Bortle said.

After June 15, Comet McNaught will rapidly slide lower toward the north-northeast horizon, passing very close to the brilliant star Capella in the constellation Auriga around June 22 and a few mornings later very near to the second magnitude star Menkalinan.

By then, McNaught will be visible – albeit with some difficulty – both in the evening sky for a short while just after sunset very low above the north-northwest horizon and in the morning sky just before sunrise very low above the north-northeast horizon.



Comets are very unpredictable, but some astronomers say Comet McNaught might reach magnitude +2 by the end of June. If so, it won't rival the brightest stars in the sky, but it should be easy to spot and readily identifiable as a comet.

Jupiter Takes Another Hit!

Jupiter Takes Another Hit

More than a day after the impact, many observatories have had a chance to image Jupiter when the site was back in view (Jupiter has a rotation period of about 10 hours), and none have reported a new marking.

Not just one but two veteran planetary imagers caught the shots of a lifetime on June 3rd, when they both videorecorded a tiny, brilliant flare on Jupiter swelling and fading at 20:31 Universal Time. The flare brightened and faded in about two seconds. Its progress is recorded on many frames of each video.

The flare may have looked small from Earth, but it must have been titanic to be visible from Jupiter's distance — and on Jupiter's daylit side, no less. It was presumably the impact of a small asteroid or comet nucleus.

Veteran planetary imager Anthony Wesley, an amateur in Murrumbateman, Australia, was recording in red light at the lucky moment, intending to create another of his many excellent stacked-video color stills of Jupiter. He saw it happen on his monitor in real time. Watch his video. The meteor "doesn't seem to have left any mark, so it probably burned up in the upper atmosphere before it reached the cloud deck," suggests Wesley. "There were no visible remains at the impact point for the next half hour or so, until sunrise put an end to the imaging."

At the same moment, Christopher Go was imaging Jupiter several thousand miles away in the Phillipines. "Today was suppose to be a routine imaging run," he writes. "Seeing was perfect. And this was on the boring side of Jupiter. On my second image sequence using the blue filter, I luckily imaged an impact on Jupiter. I did not see this when it happened but Anthony sent an alert on this suspected impact and I was able to confirm this with my video." Go's video of the Jupiter impact provides ironclad confirmation of the event!

Jupiter's central meridian longitude at the time of the images was 34° (System II), but the site of the impact is at 343° (System II). There has been confusion about this on the internet. The latitude is 16° south.

This region was again turned toward Earth when Jupiter was up before dawn as seen from Europe and Africa on June 4th. Writes John H. Rogers of the British Astronomical Association: "This morning [the 4th] around 3:30 UT, observers in England, France and Italy looked for an impact spot but recorded nothing definite. However, the images were at low resolution (due to the low altitude and bright dawn sky), so the images do not exclude a smaller scar. Observations of this site over the next few days will be very important."

Wesley was already famous for discovering an impact on Jupiter last July 19 — by the dark mark it left behind — spurring astronomers around the world to study that serendipitous event from both the ground and space.

Coincidentally, Wesley made his latest find on the same day that the Hubble team analyzing his July 2009 impact announced that that strike was an asteroid, not a comet as in the great Jupiter splash of 1994.