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Rosetta’s Comet ‘Sweats’ Two Glasses Of Water A Second


ESA’s Rosetta spacecraft has found that comet 67P/Churyumov–Gerasimenko is releasing the equivalent of two small glasses of water into space every second, even at a cold 583 million kilometres from the Sun.

The first observations of water vapour streaming from the comet were made by the Microwave Instrument for Rosetta Orbiter, or MIRO, on 6 June, when the spacecraft was about 350 000 kilometres from the comet.

Since the initial detection, water vapour has been found every time MIRO has been pointed towards the comet.

“We always knew we would see water vapour outgassing from the comet, but we were surprised at how early we detected it,” says Sam Gulkis, the instrument’s principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, California, USA.

“At this rate, the comet would fill an Olympic-size swimming pool in about 100 days. But, as it gets closer to the Sun, the gas production rate will increase significantly. With Rosetta, we have an amazing vantage point to observe these changes up close and learn more about exactly why they happen.”

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Comet’s Brush With Mars Offers Opportunity, Not Danger


Comet Siding Spring will brush astonishingly close to Mars later this year – close enough to raise concerns about the safety of a fleet of spacecraft orbiting the Red Planet. But after observing Siding Spring through a satellite-mounted telescope, University of Maryland comet experts found that it poses little danger to the Mars craft. The spacecraft will be able to get an unprecedented close look at the changes happening to this “fresh” comet as it nears the sun – as well as any changes its passing may trigger in the Martian atmosphere.

Fresh comets like Siding Spring, which have never before approached the sun, contain some of the most ancient material scientists can study. The UMD astronomers’ observations are part of a two-year-long research campaign to watch how the comet’s activity changes during its travels.

“Comet Siding Spring is making its first passage through the inner solar system and is experiencing its first strong heating from the sun,” said UMD assistant research scientist Dennis Bodewits, lead researcher on the UMD astronomy team that used NASA’s Swift satellite to estimate the comet’s size and activity. “Comets like this one, which formed long ago and remained for billions of years in the icy regions beyond Pluto, still contain the primeval building materials of our solar system in their original state.”

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NASA Instruments On Rosetta Start Comet Science


Artist's impression. Image Credit: ESA/ATG Medialab

Artist’s impression. Image Credit: ESA/ATG Medialab

Three NASA science instruments aboard the European Space Agency’s (ESA) Rosetta spacecraft, which is set to become the first to orbit a comet and land a probe on its nucleus, are beginning observations and sending science data back to Earth.

Launched in March 2004, Rosetta was reactivated in January 2014 after a record 957 days in hibernation. Composed of an orbiter and lander, Rosetta’s objective is to arrive at comet 67P/Churyumov-Gerasimenko in August to study the celestial object up close in unprecedented detail and prepare for landing a probe on the comet’s nucleus in November.

Rosetta’s lander will obtain the first images taken from a comet’s surface and will provide the first analysis of a comet’s composition by drilling into the surface. Rosetta also will be the first spacecraft to witness at close proximity how a comet changes as it is subjected to the increasing intensity of the sun’s radiation. Observations will help scientists learn more about the origin and evolution of our solar system and the role comets may have played in seeding Earth with water, and perhaps even life.

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Rosetta’s Comet Wakes Up


It’s back! After comet 67P/Churyumov-Gerasimenko had disappeared behind the Sun and out of the Earth’s view last year in October, the target comet of ESA’s Rosetta mission can now be seen again. In the most recent image obtained by researchers from the Max Planck Institute for Solar System Research (MPS) in Germany and the European Southern Observatory (ESO) with the help of ESO’s Very Large Telescope on February 28th, 2014, the comet presents itself brighter than expected for the nucleus alone. This suggests that frozen ice is already beginning to vaporize and form a very thin atmosphere. In August, the spacecraft Rosetta will rendezvous with 67P/Churyumov-Gerasimenko and accompany it on its journey around the Sun until at least the end of 2015.

To obtain a measurable image of the comet from a distance of 740 million kilometers, the scientists superposed several exposures taken at slightly different times. Before, the images were shifted to compensate for the comet’s motion. The stars in the background therefore appear as broadly smudged lines. Subtracting the starry background then revealed the comet: a tiny dot in space.

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Subaru Telescope Detects Rare Form Of Nitrogen In Comet ISON

February 24, 2014 Leave a comment

A team of astronomers, led by Ph.D. candidate Yoshiharu Shinnaka and Professor Hideyo Kawakita, both from Kyoto Sangyo University, successfully observed the Comet ISON during its bright outburst in the middle of November 2013. Subaru Telescope’s High Dispersion Spectrograph (HDS) detected two forms of nitrogen–14NH2 and 15NH2–in the comet. This is the first time that astronomers have reported a clear detection of the relatively rare isotope 15NH2 in a single comet and also measured the relative abundance of two different forms of nitrogen (“nitrogen isotopic ratio”) of cometary ammonia (NH3). Their results support the hypothesis that there were two distinct reservoirs of nitrogen the massive, dense cloud (“solar nebula”) from which our Solar System may have formed and evolved.

Why did the team focus on studying these different forms of nitrogen in the comet? Comets are relatively small Solar System objects composed of ice and dust, which formed 4.6 billion years ago in the solar nebula when our Solar System was in its infancy. Because they usually reside in cold regions far from the Sun, e.g., the Kuiper belt and Oort cloud, they probably preserve information about the physical and chemical conditions in the early Solar System. Different forms and abundances of the same molecule provide information about their source and evolution. Were they from a stellar nursery (a primordial interstellar cloud) or from a distinctive cloud (solar nebula) that may have formed our Solar System’s star, the Sun? Scientists do not yet understand very well how cometary molecules separate into isotopes with different abundances. Isotopes of nitrogen from ammonia (NH3) may hold the key.

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Hyper Suprime-Cam Captures A Clear Image Of Comet ISON’s Long Tails

November 28, 2013 Leave a comment

Imaged by HSC

Imaged by HSC

During an intensive commissioning run, Hyper Suprime-Cam (HSC), mounted at prime focus on the Subaru Telescope, has successfully imaged the Comet ISON (C/2012 S1) as it journeys toward the Sun. Especially striking in the HSC image are the comet’s long tails, which span a distance more than twice the diameter of the full moon.

The observation took place in the early morning of November 5, 2013 in Hawaii during a test of non-sidereal tracking, which follows an object that moves at a different rate than the stars. Since Solar System objects such as comets and asteroids appear to move faster than more distant stars and galaxies, they require this special mode of telescope tracking, which allows observers to keep the target in view. An additional challenge for tracking Comet ISON was its low altitude of less than 30 degrees. Nevertheless, the commissioning team was able to capture a clear image of the comet and its tails, including their faint parts, which extend more than one degree away from the Sun. At the time of the observation, Comet ISON was 170 million kilometers from the Earth and 130 million kilometers from the Sun.

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Comet ISON Brightening Fast As Its Moment Of Truth Nears

November 21, 2013 Leave a comment

Comet ISON. Credit: Damian Peach / SkyandTelescope.com

Comet ISON. Credit: Damian Peach / SkyandTelescope.com

Comet ISON, anticipated by skywatchers for more than a year, is brightening fast just days from its fateful hairpin swing on November 28th around the broiling surface of the Sun. The comet is now a greenish-white fuzzy “star” in binoculars, low in the east-southeast at the beginning of dawn. Telescopic photos are showing it with a long, ribbony tail. The comet has flared with unexpected outbursts of gas and dust three times already this month.

“We might witness a nice, long-tailed comet visible to the naked eye that will leave millions of people with fond memories for a lifetime,” says Alan MacRobert, a senior editor of Sky & Telescope magazine. “Or maybe it will be a small comet for sky hunters using binoculars and a good map of its position. Or it might yet break up and vanish.”

It all depends on what happens to the comet’s tiny nucleus, its only solid part. A comet’s nucleus is a dirty iceball that’s just a pinpoint by astronomical standards — in this case less than a mile or two across. As it flies in from the cold outer solar system and warms in the heat of the Sun, some of its ice evaporates, releasing gas and dust that expands by thousands or even millions of miles to become the comet’s glowing head (“coma”) and tail.

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