Apr 16

Unique Fragment from Earth’s Formation Returns after Billions of Years in Cold Storage

Source: ESO Science Release eso1614

eso1614aArtist's impression of the unique rocky comet C/2014 S3 (PANSTARRS).
Image credits: ESO/M. Kornmesser

Astronomers have found a unique object that appears to be made of inner Solar System material from the time of Earth’s formation, which has been preserved in the Oort Cloud far from the Sun for billions of years. Observations with ESO’s Very Large Telescope, and the Canada France Hawai Telescope, show that C/2014 S3 (PANSTARRS) is the first object to be discovered on a long-period cometary orbit that has the characteristics of a pristine inner Solar System asteroid. It may provide important clues about how the Solar System formed.(Learn more)

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Jan 15

Science reveals Rosetta's research on comet 67P/Churyumov-Gerasimenko (67P)

Source: Science

Comet-67P-grand-viewLandscape on the smaller of the two lobes of Comet 67P/Churyumov-Gerasimenko
taken from a distance of  just 5 miles (8 km).
Image credit: ESA/Rosetta/MPS for OSIRIS Team

A series of scientific papers in journal Science published on January 23rd offers a complete, if preliminary, look at Rosetta’s comet. And what a wonderful and complex world it is.

Taylor & al. made an abstract of the articles that states that the surface of the comet shows evidence of many active processes and is highly complex. The solid nucleus is an object for which neither horizontal nor vertical variations are modest. He also says that the current comet shape model suggests that the mass is 1013 kg (about 100 million times the mass of the international space station), with a bulk density of ~470 kg/m3 (similar to cork, wood, or aerogel). The low mass and density values strongly constrain the composition and internal structure of the nucleus, implying a relatively fluffy nature, with a porosity of 70 to 80%". There is also some ideas about nucleus surface that appears rich in organic materials, with little sign of water ice.

It seems also that the coma produced by ices sublimating from the nucleus is highly variable, displaying large diurnal and possibly seasonal changes. (learn more)

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Jan 15

Don't miss comet Lovejoy

Source: Universe Today

Lovejoy-photo-chart-Orion_V4Comet Lovejoy’s nightly position among the winter stars through January 19.
Image credit: Bob King.

Beautiful New Year’s comet – Comet C/2014 Q2 Lovejoy – passed closest to Earth on January 7, 2015 and therefore (probably) now appears at its brightest in our sky. On January 7, it was 70.2 million km away and shining at an apparent magnitude of +4. Many across the globe have already seen this comet as it has brightened in recent weeks. Plus, the moon is no longer a hindrance. More good news. The comet has been moving northward on the sky’s dome. On January 9, it crossed over into the easy-to-find constellation Taurus (the Bull). Look to the photo above to try to spot it in the night sky. (learn more)

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Mar 14

Crashing Comets Explain Surprise Gas Clump Around Young Star

Source: ESO Science Release eso1408

Artist's impression of Beta Pictoris.
Image credits: NASA's Goddard Space Flight Center/F. Reddy

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in northern Chile have today announced the discovery of an unexpected clump of carbon monoxide gas in the dusty disc around the star Beta Pictoris. This is a surprise, as such gas is expected to be rapidly destroyed by starlight. Something — probably frequent collisions between small, icy objects such as comets — must be causing the gas to be continuously replenished. The new results are published today in the journal Science.(read more)

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Nov 13

Two Comets to Fly By Mercury on Nov. 18-19

Credits: NASA SCience News

On Nov. 18-19, two comets (ISON and Encke) are going to fly by the planet Mercury in quick succession. NASA's MESSENGER spacecraft will have a front-row seat for the rare double encounter.

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Aug 13

Comet ISON to fly by Mars

Source: NASA Science Casts

Comet ISON is heading for a Thanksgiving Day brush with the sun, but first it's going to pay a visit to the Red Planet. Mars rovers and satellites will have a ringside seat for the comet's close approach on Oct. 1st.

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Jun 13

ALMA Discovers Comet Factory

Source: ESO Science Release eso1325

Artist’s impression of the dust trap in the system Oph-IRS 48.
Image credits: ESO/L.Calçada.

Astronomers using the new Atacama Large Millimeter/submillimeter Array (ALMA) have imaged a region around a young star where dust particles can grow by clumping together. This is the first time that such a dust trap has been clearly observed and modelled. It solves a long-standing mystery about how dust particles in discs grow to larger sizes so that they can eventually form comets, planets and other rocky bodies. The results are published in the journal Science on 7 June 2013. (read more)

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Feb 13

A Possible Naked-eye Comet in March

Source: NASA

A comet falling in from the distant reaches of the solar system could become a naked-eye object in early March. This is Comet Pan-STARRS's first visit to the inner solar system, so surprises are possible as its virgin ices are exposed to intense solar heating for the first time.

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Apr 12

Herschel spots comet massacre around nearby star

Source: ESA

Herschel’s image of Fomalhaut.
Image credits: ESA/Herschel/PACS/Bram Acke, KU Leuven, Belgium.

ESA’s Herschel Space Observatory has studied the dusty belt around the nearby star Fomalhaut. The dust appears to be coming from collisions that destroy up to thousands of icy comets every day. (read more)


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Feb 12

Mission to Land on a Comet

Source: NASA Science Casts

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Jan 12

Comet Corpses in the Solar Wind

Source: NASA Science News

Comet C/2011 N3 fragments as it passes through the sun's atmosphere on July 6, 2011.
Credit: Solar Dynamics Observatory/K. Schrijver et al

A paper published in today's issue of Science raises an intriguing new possibility--the presence of abundant comet corpses in the solar wind. The new research is based on dramatic images of a comet disintegrating in the sun's atmosphere last July.(learn more)

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Jan 12

Some Comets Like it Hot

Source: NASA Science News

Astronomers are still scratching their heads over Comet Lovejoy, which plunged through the atmosphere of the sun in December and, against all odds, survived. The comet is now receding into the outer solar system leaving many mysteries behind.

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Dec 11

Comet Lovejoy Plunges into the Sun ... and Survives

Source: NASA Science News

Sungrazing Comet Lovejoy has shocked astronomers by surviving its "death plunge" into the sun. Must-see movies of the comet's passage through the sun's atmosphere are featured at Science@NASA.(read more)

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Oct 11

Comet storm in a nearby Star System

Source: NASA Science News and NASA News

Artist's impression of comet storm around Eta Corvi. Image credit: NASA.

NASA's Spitzer Space Telescope has detected signs of icy bodies raining down in an alien solar system. The downpour resembles our own solar system several billion years ago during a period known as the "Late Heavy Bombardment." (read more)

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Oct 11

Did Earth's oceans come from comets?

Source: ESA Press Release

Herschel observed comet Hartley 2  represented in its orbit on the left side and
the inset on the right side shows the image obtained with Herschel’s PACS instrument.
The two lines are the water data from HIFI instrument.
Image Credits: ESA/AOES Medialab; Herschel/HssO Consortium.

ESA's Herschel infrared space observatory has found water in a comet with almost exactly the same composition as Earth's oceans. The discovery revives the idea that our planet's seas could once have been giant icebergs floating through space.(read more)

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Oct 11

Draconid meteor outburst

Source: NASA Science News

Comet 21P/Giacobini-Zinner in Nov. 1998.
Image credits: N.A.Sharp/NOAO/AURA/NSF

Forecasters say Earth is heading for a stream of dust from Comet 21P/Giacobini-Zinner. A close encounter with the comet's fragile debris could spark a meteor outburst over parts of our planet on October 8th.(read more)

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Aug 11

Comet Garradd C2009 P1 passing M71

Source: YouTube

A fabulous video of Comet Garradd passing the globular cluster M71 done by Bareket observatory, Israel.

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Aug 11

Coming up: Comet Garradd

Comet Garradd (C/2009 P1) on August 2, 2011. Image credit: Peter Lake.

Comet Garradd is now getting brighter in the night sky and you can look for the fuzzy ball going from the constellation of Pegasus into the Summer Triangle (view map @Astro Bob). At a magnitude of about 9, it should be visible in a dark place with a small telescope or even binoculars. It will peak at February at a magnitude about 6 and shall pass closest to Earth in the beginning of March 2012 when it will be seen in the Little Dipper asterism.

Comet Garradd was discovered by G. J. Garradd (Siding Spring Observatory, Australia) on four images obtained on  August 13, 2009 . He was using the 0.5-m Uppsala Schmidt telescope and a CCD camera. The magnitude was given as 17.5-17.7 and the coma was described as circular and 15" across. The first confirmation was obtained by W. Robledo (El Condor Observatory, Cordoba) on August 14, 2009.

Upcoming Highlights (from Cometography)
# The comet will reach a maximum solar elongation of 149 degrees on 2011 August 8.
# After having moved northward since September 2010, the comet will attain a declination of +19.9 degrees on 2011 September 12 and will then turn southward.
# The southward motion will only continue until 2011 October 26, when the comet attains a declination of +18.7 degrees and will then resume a northward motion.
# The comet will reach a minimum solar elongation of 45 degrees on 2011 December 5.
# The comet will be closest to Earth on 2012 March 5 (1.27 AU).
# The comet will attain its most northerly declination of +70.7 degrees on 2012 March 11 and will move steadily southward for the remainder of the year.

# The comet will reach a maximum solar elongation of 112 degrees on 2012 March 17.

Gary W. Kronk's Cometography - C/2009 P1 (Garradd)
AstroSwanny's: garradd

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Jul 11

SOHO watches comet Hartley 2 fading away

Source:  arXiv

On November 4, 2010, NASA's EPOXI spacecraft went within 450 miles of Comet Hartley 2.  Designated officially as 103P/Hartley 2, the comet thus became the fifth comet with close-up images.

Hartley 2 is a short period comet that about six and a half years to orbit the Sun and is also a small comet with about 1.5 km in diameter.

But the Solar and Heliospheric Observer (SOHO), better known for its observations of the sun, also observed comet Hartley 2. Together, the two returned data about what appears to be an irregular comet, ejecting  chunks of ice and losing water at a very fast pace.

These findings were described in an article of the June 10, 2011 issue of the Astrophysical Journal Letters.

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Jul 11

A Pulsar and its mysterious tail

Source: Chandra

Image credit: X-ray: NASA/CXC/IUSS/A.De Luca et al; Optical: DSS

A spinning neutron star is tied to a mysterious tail - or so it seems. Astronomers using NASA's Chandra X-ray Observatory have found that this pulsar, known as PSR J0357+3205 (or PSR J0357 for short), apparently has a long, X-ray bright tail streaming away from it.

This composite image shows Chandra data in blue and Digitized Sky Survey data in yellow. The position of the pulsar at the upper right end of the tail is seen by mousing over the image. The two bright sources lying near the lower left end of the tail are both thought to be unrelated background objects located outside our galaxy.

PSR J0357 was originally discovered by the Fermi Gamma Ray Space Telescope in 2009. Astronomers calculate that the pulsar lies about 1,600 light years from Earth and is about half a million years old, which makes it roughly middle-aged for this type of object.

If the tail is at the same distance as the pulsar then it stretches for 4.2 light years in length. This would make it one of the the longest X-ray tails ever associated with a so-called "rotation-powered" pulsar, a class of pulsar that get its power from the energy lost as the rotation of the pulsar slows down. (Other types of pulsars include those driven by strong magnetic fields and still others that are powered by material falling onto the neutron star.)

The Chandra data indicate that the X-ray tail may be produced by emission from energetic particles in a pulsar wind, with the particles produced by the pulsar spiraling around magnetic field lines.

Other X-ray tails around pulsars have been interpreted as bow-shocks generated by the supersonic motion of pulsars through space, with the wind trailing behind as its particles are swept back by the pulsar's interaction with the interstellar gas it encounters.

However, this bow-shock interpretation may or may not be correct for PSR J0357, with several issues that need to be explained. For example, the Fermi data show that PSR J0357 is losing a very small amount of energy as its spin slows down with time. This energy loss is important, because it is converted into radiation and powering a particle wind from the pulsar.

This places limits on the amount of energy that particles in the wind can attain, and so might not account for the quantity of X-rays seen by Chandra in the tail.

Another challenge to this explanation is that other pulsars with bow-shocks show bright X-ray emission surrounding the pulsar, and this is not seen for PSR J0357. Also, the brightest portion of the tail is well away from the pulsar and this differs from what has been seen for other pulsars with bow-shocks.

Further observations with Chandra could help test this bow-shock interpretation. If the pulsar is seen moving in the opposite direction from that of the tail, this would support the bow-shock idea.

These results were published in the June 1st, 2011 issue of The Astrophysical Journal. The first author is Andrea De Luca of Institute of Advanced Study in Pavia, Italy (IUSS), the National Institute of Nuclear Physics (INFN) in Rome, and the National Institute for Astrophysics (INAF) in Milano.

The co-authors are M. Marelli of INAF, Milano and the University of Insubria in Italy; R. Mignani of University College London, UK and University of Zielona Gora, Poland; P. Caraveo of INAF, Milano; W. Hummel of ESO, Germany; S. Collins and A. Shearer of National University of Ireland; P. Saz Parkinson of University of California at Santa Cruz; A. Belfiore of University of California at Santa Cruz and University of Pavia; and, G. Bignami of IUSS, Pavia and INAF, Milano.

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