Friday, February 27, 2009

Changing geometry of comet C/2007 N3 (LULIN)

During the past few nights, we witnessed a dramatic change of the viewing geometry of comet C/2007 N3 (LULIN): its ion tail switched its position from North-West, and is currently hidden behind the coma. However this phenomena doesn't change that much the visibility of some details within the inner coma of the comet.

Here you can find an image obtained on 2009, Feb. 27 (details in caption):

Comparison with a similar image, obtained on 2009, Feb. 19 (details in caption):

shows the persistence of some asymmetries in the inner coma. In particular, a kind of "fan" toward PA 200 deg, with a second, similar structure (but less evident) in the opposite direction, toward PA 20 deg. It's not clear yet the explanation of this features; what we can say at the moment, is that they doesn't seem to be artefacts (i.e. artificially generated features using image processing softwares) and that they show no significant changes in spite of the significative change of our perspective angle.

by Ernesto Guido, Giovanni Sostero and Paul Camilleri

Tuesday, February 24, 2009

Comet Lulin at its best

Today, February 24th, comet C/2007 N3 (LULIN) is making its closest approach to Earth (0.41 A.U.) peaking at magnitude 5.0. After that Lulin is moving away from both Earth and the Sun, so it fades fairly quickly. 

Yesterday, Lulin was just 2 degrees south-southwest of Saturn. Below you can see our image showing the rendez-vous between the comet and the planet (click on it for a bigger version):

While here there is an animation showing the motion of the comet in 5 minutes (this week the comet is moving at over 5° per day):

Because of the particular geometry between Earth, comet and Sun we see the comet Lulin showing a nice sunward pointing dust tail (antitail) along with a ion tail. This diagram shows the geometry of Comet Lulin's tail and anti-tail (click on it for a bigger version):

Credit: Paolo Berardi

For more information and images please check also our past posts about this nice comet:

By Ernesto Guido & Giovanni Sostero

Friday, February 20, 2009

2008 TC3 Fragments Recovered!!!

According to an article appeared few hours ago on New Scientist website, a team of meteorite hunters, using data provided by NASA, has finally has found fragments of the asteroid 2008 TC3 plunged into the atmosphere above Sudan on 7 October 2008.

Here You can find some of the post appeared on this blog about 2008 TC3 story:

A photo of one of the fragments recovered can be seen in the slides of a presentation reported at a United Nations meeting discussing near-Earth object (NEO) impacts (slide number 19):

 (courtesy of P. Jennisken - SETI Institute)

It seems that the discovery team, including well-know meteorite expert Peter Jenniskens, has already submitted a study about the find to a scientific journal, but no more information are available at present.

UPDATE The paper "The recovery of asteroid 2008 TC3" by M. H. SHADDAD, P. JENNISKENS et al. is available here

by Ernesto Guido

Thursday, February 19, 2009

Coma asymmetry of comet C/2007 N3 (LULIN)

Few hours ago we imaged C/2007 N3 (LULIN) through a narrowband interferential filter, centered in the dust continuum (647nm, FWHM= 10nm). At these wavelengths, what we see is (nearly) only dust. Some image-processing show a curious asymmetry of the coma, as noticed before in some other comets.

Possible features in (about) PA 40 deg and PA 220 deg became visible, as well  (click on the image for a bigger version):

While here you can see an animation of the comet imaged without filter on 18 February 2009 (click on it for a bigger version):

by Giovanni Sostero, Ernesto Guido and Paul Camilleri

Wednesday, February 4, 2009

Comet Lulin disconnection event

Today we wanted to make some wide-field imaging of comet C/2007 N3 (LULIN), in search for large scale structural features. In our image (see below, details in the caption; click on it for a bigger version):

is clearly visible the characteristic dichotomy of this comet: a dusty anti-tail pointing toward the Sun (i.e. to South-East) and the highly structured ion (plasma) tail toward West,Northwest. This uncommon configuration, is due to the particular geometric circumstances occuring during these nights, with the comet seen nearly head-on as seen from Earth.

Moreover, we were lucky enough to capture an intriguing phenomena: in our images is clearly visible a nice disconnection event (DE) in the plasma tail of the comet (evidenced by a red circle in this rendition):

The DE indicates that the comet has recently passed through a disturbance in the magnetic field carried by the solar wind, that destroyed the original plasma tail, creating a new one. The separation of the two ion tails indentified by the DE, is visible in our image as a kind of elongated and diffuse "knot" along the plasma tail.

A 3x zoomed view of this feature is available here:

The "knot" is dragged tailward by the solar wind, and will dissipate soon. More events like this are expected in the near future, when comet LULIN will approah Earth. Comet aficionados, heads-up!

by Ernesto Guido, Giovanni Sostero and Paul camilleri