Saturday, November 20, 2010

Bright Sungrazing Comet on November 17-19, 2010

Only few days after the bright sungrazing comet of November 13/14, another new bright comet diving into the Sun has been discovered on Nov. 17 by Michal Kusiak using the images taken by SOHO spacecraft. This object too belong to the famous Kreutz-group, a family of sungrazing comets that are named after German astronomer Heinrich Kreutz who first studied them in the details. These comet fragments passes extremely close to the Sun at perihelion and usually they completely evaporated during such a close approach.

LASCO C2 Image - November 19, 2010

(Credit: SOHO)

C2 Movie (click on the thumbnail for a bigger version)

(Credit: SOHO)

We've had many bright Kreutz comets this year... A sign of a big one on its way?

Recently, different studies (Sekanina & Chodas 2007; Knight & Hearn 2008) have shown that the flow of Kreutz comets (correct of all systematic errors) increased. In the years since 1997 to 2002 for the Kreutz comet brighter that eighth magnitude has been calculated an average of about 83 new discoveries each year, while in the period 2003 - 2007 the average annual discovery rate risen to 125. This increase also applies to the findings of comets brighter than sixth magnitude where there was a increase in the flux of comets around 80%.

Sekanina and Chodas (2007) noted the increase in raw discoveries and suggested it may be “an early warning of another cluster of bright sungrazers approaching the Sun in coming decades.”

On November 18, 2010 the leading expert on Kreutz comets (reduced the observations of almost all of SOHO's ~1950 comets), Brian Marsden passed away after a prolonged illness. He will be remembered as contributing much to celestial mechanics and the dynamics and orbits of minor bodies of the solar system and as having an encyclopedic knowledge of the history of astronomy. Obituary on Sky & Telescope website and on mpec 2010-W10

by Ernesto Guido

Tuesday, November 16, 2010

Bright Sungrazing Comet on 13/14 November 2010

A new bright comet diving into the Sun has been discovered on Nov. 13th by Masanori Uchina using the images taken by SOHO spacecraft. This object belong to the famous Kreutz-group, a family of sungrazing comets that are named after German astronomer Heinrich Kreutz who first studied them in the details. These comet fragments passes extremely close to the Sun at perihelion and usually they completely evaporated during such a close approach.

Several sungrazing comets are discovered each year in SOHO images, many of them are very small and faint while sometimes some bigger and bright fragments arrive in the proximity of the Sun.

As expected, this sungrazing comet has not survived the close encounter with the sun.

C2 Image - November 14 ,2010

(Credit : SOHO)

C2 Movie (click to see a bigger version)

(Credit : SOHO & Spaceweather)

You can read more details about other recently 2010 bright SOHO comets here:

by Ernesto Guido

Monday, November 8, 2010

Evolution of the morphology of comet C/2010 V1

The recently discovered comet C/2010 V1 (Ikeya-Murakami) has been probably discovered thanks to an outburst. In fact IAUC 9183 reports that Kaoru Ikeya swept the comet's position also on Nov. 1, but did not see the comet down to mag 9-10, despite better conditions than on the 2nd. Moreover the evolution of its coma morphology is rapidly changing from night to night.

Here you can see our last image of this comet (stack of 10X30seconds exposures) obtained on 2010 Nov. 08.5, remotely from the GRAS Observatory (near Mayhill, NM) through a 0.25-m, f/3.4 reflector + CCD.

Below an animation showing the evolution of the morphology of comet C/2010 V1 (Ikeya-Murakami) starting from our first image dated Nov. 04 to the last image dated Nov. 08, 2010 (in the animation the image of Nov. 7 is not present due to cloudy sky):

by Ernesto Guido & Giovanni Sostero

Comet 103P/Hartley by EPOXI

As most of you already know, NASA's Deep Impact spacecraft (renamed EPOXI) successfully flew 700 kilometers away from comet 103P/Hartley on Thursday November 04, 2010. This comet is the fifth comet nucleus visited by a spacecraft (the other four are: Halley, Tempel 1, Borrelly and Wild 2).

"Early observations of the comet show that, for the first time, we may be able to connect activity to individual features on the nucleus," said EPOXI Principal Investigator Michael A'Hearn of the University of Maryland, College Park.

Below you can find the flyby images released until now.

Montage showing the comet approached by the spacecraft. The sun is to the right.

(Credit: NASA/JPL-Caltech/UMD )

Close-up view of comet 103P/Hartley taken by NASA's EPOXI

(Credit: NASA/JPL-Caltech/UMD )

Image showing jets and where they originate from the surface of comet

(Credit: NASA/JPL-Caltech/UMD )

Below an image montage showing all the five comet nucleus visited by a spacecraft. Comet 103P/Hartley is by far the smallest and has the most activity in relation to its surface area.

(Credit: NASA/JPL-Caltech/UMD )

The analysis of the data acquired is underway and more revelations about comet 103P/Hartley are expected.

Congrats to the all the EPOXI team for this spectacular flyby!!

by Ernesto Guido

Friday, November 5, 2010

Comet C/2010 V1 (Ikeya-Murakami)

The new bright morning comet announced yesterday has been officially designated C/2010 V1 (Ikeya-Murakami). The mpec 2010-V46 with the first and preliminary orbit has been issued and it shows the perihelion already on Oct. 18, 2010, at about 1.7 AU.

Today we performed again some follow-up of this bright object to obtain more astrometric measures that are important to compute a reliable orbit. Below you can see the image (stack of 10X20seconds exposures) obtained on 2010 Nov. 05.5, remotely from the GRAS Observatory (near Mayhill, NM) through a 0.25-m, f/3.4 reflector + CCD. It's still evident the strong central condensation and the elongation toward PA 295.

According to COCD webpage this is the 7th visual comet discovery for Ikeya (co-discoverer also of the famous 1965's sungrazer Comet Ikeya-Seki) and the 2nd for Murakami.

by Ernesto Guido & Giovanni Sostero

Thursday, November 4, 2010

New Bright Comet: "2010 V1"

IAUC nr.9175, issued on 2010, Nov. 03, announces the visual discovery of a new bright comet by two Japanese amateur astronomers, Kaoru Ikeya and Shigeki Murakami. The new comet has been designated "2010 V1". The orbit is still not available, it will be ready when more astrometric observations will be available.

This is the second visual comet discovery of 2010, after the discovery in March of comet C/2010 F4 by Don Machholz.

We performed some follow-up measurements of this object few hours ago, on 2010 Nov. 04.5, remotely from the GRAS Observatory (near Mayhill, NM) through a 0.25-m, f/3.4 reflector + CCD. Our stackings shows a coma diameter of nearly 2 arcminutes, elongated toward PA 295 and a strong central condensation.

This comet is currently at a solar elongation of only 32 degree with a ccd magnitude around 12 and a visual magnitude around 8.

Congratulations to Ikeya and Murakami for this discovery!!

by Ernesto Guido & Giovanni Sostero

Wednesday, November 3, 2010

Comet 103P/Hartley

Tomorrow November 04, at 13:50 UTC the Deep Impact spacecraft (renamed EPOXI for this extended mission) will have a close encounter with the comet 103P/Hartley. At closest approach (roughly 700 kilometers), the spacecraft imager named MRI (Medium Resolution Imager) will achieve about 7 meters per pixel, and the nucleus should appear about 170 pixels across. When EPOXI will reaches the comet, it will be nearly 1.1 astronomical units away from the Sun and only 0.15 astronomical units from Earth.

Comet 103P/Hartley was discovered by Malcolm Hartley in 1986 at the Schmidt Telescope Unit in Siding Spring, Australia. It belongs to the Jupiter family of comets (orbital period of 6.47 years) and it has a nucleus of about 2 km. So far only 4 comet nucleii have been explored by a spacecraft (Halley, Tempel 1, Borrelly and Wild 2), but comet 103P is unlike the others.

Discovery image (1986)

(U. K. Schmidt Telescope Unit, Siding Spring Observatory)

According to principal investigator Mike A'Hearn: "Comet Hartley 2 is smaller yet much more active than others comets. Although its core is only 2 km wide—about, a third the size of Tempel 1, it is spewing five times more gas and dust." The EPOXI team observed a strange activity on the comet in September: the abundance of CN in the comet's atmosphere jumped by a factor of five over an eight day period but there was no corresponding increase in dust. This was unexpected and never been seen in a comet before. In fact usually a gas surge is accompanied by a dust increment too.

(Credit: EPOXI)

To help the EPOXI team in their rendez-vous with the comet, the astronomical community (amateurs & professionals) are imaging the comet.

WISE spacecraft imaged the dust trail of 103P/Hartley on May 10, 2010. The dust trail (not to be confused with with the dust tail) is a "path of particles that the comet leaves during each of its trips through the inner solar-system". The extent of the trail seen in this view, behind the comet, is 1.8 million kilometers.

(Credit: WISE)

The comet was imaged on September 25, by the Hubble Space Telescope (HST). At the time of the Hubble observation, the comet was 1.153 astronomical units (172 million km) from the Sun and 0.218 astronomical units (32.6 million km) from Earth.

(Credit: NASA, ESA, and H. Weaver)

At the end of October 2010 (from 24 to 31 Oct.), the Arecibo planetary radar system was used to make images of comet 103P/Hartley. The radar delay-Doppler images obtained show the nucleus to be a highly elongated, bilobate object with a long-axis dimension of at least 2.2 km. The images give a preliminary rotation period estimate of 18.1 +/- 0.3 hours, although a less likely period of 13.2 hours cannot be ruled out.

(Credit: Arecibo - NAIC)

Below you can see a graph showing the preliminary results of the Italian Sezione-Comete /CARA regarding the trend of the Afrho parameter of 103P/Hartley in this apparation. For comparison in the graph there are also observations from the 1997/1998 apparition:

(Credit: CARA)

This is a list of all the observers who contributed to this graph with their observations: Paolo Bacci, Walter Borghini, Erik Bryssink, Dario Castellano, Gianni Galli, Ernesto Guido, Bernhard Hausler, Nick Howes, Rolando Ligustri, Herman Mikuz, Giannantonio Milani, Martino Nicolini, Carmen Perrella, Jure Skvarc, Giovanni Sostero, Roberto Trabatti.

Below you can see an image of 103P/Hartley imaged by N. Howes with the 2.0 meter Faulkes Telescope North (FTN) and processed by M. Nicolini using the Median Coma Model (MCM) developed by himself. The MCM filter creates an artificial coma, based on the photometry of the original image, and subtract the original image itself in order to highlight the internal zones of different brightness that are very close to the inner core and that would normally be hidden from the diffuse glow of the comet:

In the anti-solar direction (from bottom center right), we see the brightest part of the coma that extends to form the tail. But the most interesting thing is in the direction of sunlight (from the center to the top left) where there is obviously some sort of "jet" With a PA (Position Angle) of about 50 degrees.

On Oct. 26, the spacecraft's two cameras, a High-Resolution Imager (HRI), and a Medium-Resolution-Imager (MRI), caught two jets firing off the comet's surface over a 16-hour period.

While waiting for the exciting flyby of tomorrow here a recent image of 103P/Hartley imaged on October 11, 2010 by E. Guido & G. Sostero:

by Ernesto Guido