ISON’s Ghost: ‘Comet of the Century’ is Now Ex-Comet

Sad news, comet fans: ISON is no more. It’s a vaporized husk of its former self. A sublimated dirty snowball. Comet ISON is an ex-comet and this time it’s not playing.

This sad turn of events is brought to you by the joint NASA/ESA Solar and Heliospheric Observatory (SoHO)’s LASCO instrument that gives a wide-angle view of the sun’s atmosphere (pictured above). For the duration of Comet ISON’s close approach to our nearest star, LASCO has been carefully tracking the comet’s progress. After many heart-stopping hours post-perihelion on Nov. 28, space experts nearly gave up hope — ISON had vanished from LASCO’s view, apparently not surviving the sun’s extreme tidal forces and powerful radiation.

But then, just as the U.S. was recovering from Thanksgiving turkey and wine, ISON re-energized; a component of its roasted nucleus had survived the turmoil and was brightening.

Unfortunately, the brightening was short-lived. Despite a couple of days of hope, Comet ISON’s nucleus has all but disappeared, leaving a ghostly wisp of dust behind.

The “Comet of the Century” is now, officially, the Turkey of the Century.

“Among experts, a consensus is building that the comet broke apart shortly before perihelion (closest approach to the sun),” writes Tony Phillips, NASA astronomer and curator of

Like the countless sungrazing comets that have come before it, ISON succumbed to the close solar pass. Although hopes were high that the comet would survive the plunge, no one really knew what ISON was going to do. As a “virgin” comet from the Oort Cloud (a hypothetical cloud of cometary objects approximately one light-year from the sun), this was ISON’s first visit to the inner solar system. With little information on the comet’s composition, cometary fragmentation was always a possibility.

All that remains of Comet ISON seems to be a fan-shaped debris field of small fragments of the once-mighty cometary nucleus, each shard frantically venting the remaining ices into space. Any hope of seeing a dazzling naked-eye comet just in time for Christmas is vaporizing faster than the sublimating ISON fragments that now litter interplanetary space.

Voyager interseller voyage.

After 36 years, Voyager 1 goes interstellar

The tireless Voyager I spacecraft, launched in the disco era and now more than 11 billion miles from Earth, has become the first man-made object to enter interstellar space, scientists said Thursday. Interstellar space, scientists now know with certainty, is dense with particles, and the place is literally hissing. Or maybe you could say it’s whistling in the dark.

“It’s almost a pure tone. Like middle C. But slightly varying, like your piano is not quite tuned right,” said Donald Gurnett, a University of Iowa physicist who has been working on the Voyager mission most of his adult life.

Gurnett is the lead author of a paper published Thursday in the journal Science that provides what seems to be the final, incontrovertible evidence that NASA’s Voyager I has crossed into a realm where no spacecraft has gone before.

Scientists have long thought that there would be a boundary out there, somewhere, where the million-mile-per-hour “solar wind” of particles would give way abruptly to cooler, denser interstellar space, permeated by charged particles from around the galaxy.

That boundary, called the heliopause, turns out to be 11.3 billion miles from the sun, according to Voyager’s instruments and Gurnett’s calculations.

Beyond the boundary, space is — perhaps counterintuitively — much denser with particles. There are 80,000 particles per cubic meter in the region where Voyager I is now, Gurnett said.

The sun’s hot ejecta — a plasma of charged particles — forms a vast bubble, known as the heliosphere. In the outer regions of the heliosphere, the particles are relatively few and far between, with just 1,000 particles per square meter in some regions, Gurnett said. But the heliosphere has an edge. Voyager I’s epochal crossing of the boundary, into the cooler, denser plasma, took place on Aug. 25, 2012, according to the new report.

This confirms earlier findings, published in three papers in Science in June, that Voyager I on that date in August 2012 had experienced a sudden drop in solar radiation and a spike in cosmic particles coming from all around the galaxy.

But the earlier data from the spacecraft had been somewhat ambiguous. The spacecraft continued to pick up magnetic signals that suggested it was still within the sun’s magnetic field. Ed Stone, the chief scientist for Voyager, suggested that Voyager I was flying through a transitional zone.

Now, however, scientists have a new set of measurements thanks in large part to a solar flare. On March 17, 2012, the sun ejected a huge mass of particles, and when those solar particles arrived at Voyager more than a year later, on April 9, they triggered oscillations in the charged particles of matter — the plasma — surrounding the spacecraft.

From the frequency of those oscillations — essentially the sound of space itself — the scientists could interpret the density of the plasma. That density, much higher than anything registered before in the outer solar system, offered compelling evidence that Voyager I had, in fact, entered the interstellar zone.

“For the first time we’ve actually measured the density of the plasma,” Stone said. He said he’s convinced by the new data that his spacecraft has fully penetrated interstellar space.

“It’s great. This is exploration. This is wonderful,” said Stone, who has overseen the Voyager project since the early 1970s.

The two Voyager spacecraft were launched in 1977. Voyager I flew by Jupiter and Saturn, the gravity of which helped slingshot the spacecraft toward the outer reaches of the solar system. Voyager I is now traveling at 38,000 miles per hour relative to the sun.

NASA Voyager.JPEG-0f145

Voyager II flew near Jupiter and Saturn and then went on to pass by Uranus and Neptune. It is not quite as far from the sun as its sister spacecraft.

Although Voyager I is now in interstellar space, it hasn’t technically left the solar system. That’s because of the Oort cloud — a region of comets in orbit around the sun.

“We’ll get to the inner edge of the Oort cloud in about 300 years,” Stone said. “Of course the spacecraft will not still be transmitting then.”

The spacecraft draws power from the radioactive decay of Plutonium 238, and Stone thinks the dwindling power supply will force engineers to start turning off instruments in 2020. Voyager I probably will go dark by 2025.

Stone said the spacecraft will pass through the far side of the Oort cloud in about 30,000 years.