Thursday, December 15, 2011

Comet C/2011 W3 (Lovejoy) approaches the Sun

Australian amateur astronomer Terry Lovejoy discovered on Nov. 27.7 his third comet, designated C/2011 W3 (Lovejoy). On our previous post about this comet you can see our follow-up image and animation.

C/2011 W3 is a Kreutz sungrazer, 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. 

Many Kreutz sungrazer comets are observed each year by SOHO Sun-observing satellite. SOHO provides a constant view of the immediate solar vicinity and it has now discovered more than 2000 of new sungrazing comets, some just a few metres across. About 83% of the sungrazers found by SOHO are members of the Kreutz group, with the other being referred to as 'non-Kreutz' or 'sporadic' sungrazers (Meyer, Marsden, and Kracht 1 & 2 families).

Comet C/2011 W3 will probably be the brightest Kreutz-group comet that SOHO has ever observed. It will reach the perihelion on 2011 Dec. 16.02 when it will be it within 880,000 km of the center of the Sun (the comet will pass just 180,000 km from the Sun’s surface).

According to Karl Battams, the new comet Lovejoy:

1. The comet should enter the STEREO/SECCHI HI-1B images on Dec 11, and HI-1A on Dec 12
2. The comet will enter the SOHO/LASCO C3 field of view early on Dec 14
3. The comet will enter the STEREO/SECCHI COR-2 A & B fields of view early on Dec 15 (UT time), and the COR-1 fields later that day.

We downloaded "Secchi" spacecraft FITS of the Dec. 11 & 12, 2011, and played a little bit with them. Using the image processing algorythms (developed for the CARA collaboration by our fellow collaborator Martino Nicolini). On those images, it's already possible to appreciate a narrow tail, in excess of about  1 deg. Below you can see our renditions (click on the images for a bigger version):

While below you can see an animation showing comet Lovejoy in SECCHI HI-1B on December 11 & 12, 2011 (click on the thumbnail for a bigger version).

According to Dr. Matthew Knight (Lowell Observatory/JHU-APL), Comet Lovejoy was at approximately magnitude 2.0 as on the LASCO C3 images of 16:32UT, Dec 14, 2011). While the peak magnitude is still uncertain, C/2011 W3 could reach the peak brightness at mag -3 or -4 and the comet will probably not survive perihelion. If Comet Lovejoy gets as bright as magnitude -4 or -5, there is a tiny but non-zero chance that it could become visible in the sky next to the sun. But extreme care is needed due to the comet's small solar elongation angle and close proximity to the Sun in the sky.

Below you can see the comet on latest LASCO C3 data available (08:30UT of December 15, 2011). Click on it for a bigger version:

(Credit: SOHO)

Stay tuned for more updates coming soon!!

UPDATE - December 15 at 12UT

Thanks to Karl, new STEREO-B, SECCHI fits dated back to December 13, 2011 are available. In spite of the fact that the image scale factor is a little small, it's possible to appreciate the growing of a slight asymmetry of the coma (toward the north-east):

Below an animation of Dec. 11, 12 and 13 stackings (or click here to see it):

Comet Lovejoy looks to be around mag -1 now and only has ~12hrs left. The comet will reach LASCO C2 around 1500 - 1600UT of today.  The animation below shows the comet in the SOHO C3 field (click on the thumbnail for a bigger version):

(Credit: SOHO)

UPDATE - December 15 at 20UT

New STEREO-B, SECCHI fits dated back to December 14, 2011 are available. Below you can see our new image processing on the STEREO/SECCHI HI-1A FITS for Dec 14.5 (click on the image for a bigger version):

In the meantime, new SOHO C3 image dated Dec, 15 at 16:30UT is available (click on the image for a bigger version):

A new narrow tail is visible in these images. This extremely narrow features recalls the Na or Fe tails already featured on a few extremely bright comets close to the Sun, e.g.:  and

Matthew Knight of the Lowell Observatory and JHU-APL reports on Spaceweather website: "As of 16:30 UT on Dec. 15th, Comet Lovejoy has reached magnitude -3, possibly brighter. It is starting to saturate SOHO images even with narrow filters and shorter than normal exposure times." The comet is now brighter than Jupiter, but not quite as bright as Venus. If these developments continue apace, Comet Lovejoy could become visible to the naked eye in broad daylight before the end of Dec. 15th.

Again: extreme care is needed due to the comet's small solar elongation angle and close proximity to the Sun in the sky. Do not look at or near the sun through unfiltered optics; focused sunlight can seriously damage your eyes.

Comet Lovejoy's perihelion is roughly 5 hours from now, on Dec 16 at 00:30UT. Next SOHO images will be available after 22:20UT.

UPDATE - December 16 at 11UT

Surprisingly as it may seem, comet Lovejoy appears to have survived its close encounter with the sun. Video and images relased by the  NASA's Solar Dynamics Observatory (SDO) caught the comet reemerging on the other side of the Sun after its perihelion!!

SDO video showing the comet C/2011 W3 (LOVEJOY) flying towards the Sun:

While in the SDO video below you can see the comet incredibly emerging from perihelion:

Using the images taken from 04:39UT to 10:54UT by the SECCHI outer coronagraph (COR2) on the STEREO Ahead observatory on December 16, we have made this animation clearly showing what is left of the comet nucleus after the close approach with the Sun (at present no one can say how much of the comet's core remains intact). Click on the thumbnail for a bigger version:

Using images taken from SOHO C3 from 15:54 of December 15 to 09:30UT of December 16, we made this animation showing the comet on its course pre and after the perihelion. Click on the thumbnail for a bigger version:

Note how in the last frames the remnant of the pre-perihelion tail is still visible but completely disconnected from the comet:

(Credit: SOHO)

UPDATE - December 17 at 12UT

The missing SOHO C2 post-perihelion fits are now available. We just made this short animation showing the comet C/2011 W3 (Lovejoy) reemerging behind the solar disk after the perihelion on the first hours of December 16, 2011:

As we saw on the previous update, at first the emerging comet was missing its tail. Now on the latest C3 images, it is evident that tails are forming again (with the inclusion of the very narrow tail we saw just before the perihelion, possibly NA or Fe  related)  and that the comet is still very bright!!

In fact the comet has been succefully observed visually with a 10x50 binoculars by Alexandre Amorim from Brazil on Dec 17.34. He estimated the comet magnitude at -2.9. Here is its report:

C/2011 W3 (Lovejoy)
2011 Dec 17.34 UT: m1= -2.9*, Dia= <1', DC=9, tail= 0.2 in P.A. 240...10x50B...Alexandre Amorim(Florianopolis,Brazil)[comet alt. 4 deg, sun alt. -0.9 deg]

While below you can see a groud-based image taken at dawn by Jan Ebr with the FRAM remote telescope (0.3-m SCT) located in Argentina, Malargue:

UPDATE - December 19 at 15UT

Below you can see a beautiful image of the tail of comet C/2011 W3 (Lovejoy) taken on December 19, 2011 by FRAM team (Malargue, Argentina) with 200 mm telephoto lens piggybacked on the main telescope, using also a KAF-1603 camera (from FLI). Click on the image for a bigger version:

UPDATE - December 20 at 13UT

Thanks to Jakub Černý we had the chance to works on the FRAM team fits of December 17, 2011. We sorted and stacked the best V-filtered frames, and have done some image processing on it. Basically, it appears that, apart the two "tail branches", we have an asymmetric coma. In some treatement, there is the hint of a "curved jet" or "shell" (or whatever you would call it) in the inner coma, that appears to originate from the central condensation, developing in a "counterclockwise" direction. Obviously this stuff has to be confirmed in further images, to make sure it's not an artefact of my image processing. You can see below the result (click on the image for a bigger version):

On December 17, 2011 the comet has been imaged in daylight also by amateur astronomer Vincent Jacques of Breil-sur-Roya, France. Images and video below taken with an 80mm refractor at 80x + near IR filter and camera DMK21 from 09:00 UT to 13:00 UT.

(Credit: Vincent Jacques)

(Credit: Vincent Jacques)

Australian amateur astronomer Vello Tabur captured a 5-degree-long tail of comet Lovejoy on December 19.7 with a DSLR in the bright twilight.

(Credit: Vello Tabur)

Finally a new image by the FRAM team obtained on December 20, 2011 with a 30-cm Meade SCT F/10 (0.66x) located in Argentina, Malargue.

UPDATE - December 21 at 15UT

The comet has put on a great show for Southern observers. Amateur astronomer Colin Legg has been able to image (with a 5D2 digital camera) the beautiful tail of comet Lovejoy from the Mandurah Estuary on Western Australia around 3:30 WST of December 21, 2011. Below you can see his image and the stunning timelapse of his observing session.

While another observer (Grahame) from Australia  took the following image taken on December 21, 2011 at 0400 local time of Perth with canon 7D, 17-85mm lens, ISO 800 F4.5. Click on the image for a bigger version.

UPDATE - December 27 at 14UT

International Space Station Commander Dan Burbank captured spectacular images of Comet C/2011 W3 (Lovejoy) as seen from about 386 Km above the Earth’s horizon on Wednesday, Dec. 21.

(Credit : NASA)

Many beautiful images are arriving from observers in the Southern Hemisphere, you can find a very good selection here & here

Comet Lovejoy on 2011 Dec 23.7 UT, Michelago, NSW, Australia

(Credit: Vello Tabur)

by Ernesto Guido, Giovanni Sostero & Nick Howes

Tuesday, December 6, 2011

"Centaur" minor planet 2010 XZ78

2010 XZ78 is an object found on December 2010 by G96 professional survey and classified as a Centaur. To date, 17 total observations of 2010 XZ78 are present in the MPC database over interval: 2010 11 13.34 – 2011 01 08.25.

Centaurs, defined to have their perihelion outside of Jupiter (5.2 AU) and semimajor axis inside of Neptune (30.0 AU), have unstable orbits and have been extracted from the transneptunian objects (TNOs) population through perturbations by Neptune. So far only a few Centaurs have presented unambiguous evidence of cometary activity (see for example 174P/Echeclus). The first Centaur known to present cometary activity was Chiron.

We performed some follow-up of 2010 XZ78 on 2011 December 06, 2011 to lengthen the observational arc and to search for cometary activity. We found it roughly 2.2 arcminutes west of its nominal position. Stacking of 13 R-filtered exposures, 60-sec each, obtained remotely, from the Haleakala-Faulkes Telescope North on 2011, Dec. 6.4, through a 2.0-m f/10.0  Ritchey-Chretien + CCD, shows that this object has a stellar aspect, with its PSF profile being the same of the nearby field stars of similar brightness  (FWHM of 1.2").

Our image of 2010 XZ78:

by Giovanni Sostero, Nick Howes & Ernesto Guido

Monday, December 5, 2011

C/2011 W3 (LOVEJOY) - Kreutz Sungrazing Comet

Cbet nr.2930, issued on 2011, December 02, announces the discovery of a new comet (discovery magnitude 13) by Terry Lovejoy on three CCD images obtained each on Nov. 27.7 and 29.7 UT with a Celestron 8 0.20-m f/2.1 Schmidt-Cassegrain reflector (+ QHY9 camera). The new comet has been designated C/2011 W3 (LOVEJOY).

The comet appears to be a Kreutz sungrazer, 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. 

This is the first ground-Based discovery of a Kreutz Sungrazing Comet since 1970!!

We performed some follow-up measurements of this object remotely from the GRAS Observatory (Australia - MPC Code  E03) on 2011, December 04.7 through a 0.10-m f/5 reflector + CCD.

Our image of comet C/2011 W3 (LOVEJOY):

Below you can see an animation showing the fast movement of the comet in the sky. Each frame is a 30-second exposure. Click on the thumbnail for a bigger version.

M.P.E.C. 2011-X16 assignes the following preliminary orbital elements to comet C/2011 W3: T 2011 Dec. 15.99; e= 1.0; Peri. = 57.14; q = 0.005 AU; Incl.= 135.93

The comet is now rapidly brightening but seems intrinsically faint. It may not survive its close perihelion  (at 0.0058936AU, which is a little over 1.2 solar radii) passage on December 16th that will bring it within 880,000 km of the center of the Sun (comet C/2011 W3 will pass just 180,000 km from the Sun’s surface).

The following ephemeris (from Cbet 2930) assumes H = 14.0 and 2.5n = 8.  Note that the rate of brightness  increase is highly uncertain.

Date    TT        R. A. (2000) Decl.     Delta      r     Elong.    Mag
2011 12 06    15 35.96   -47 53.6    0.708    0.505    29.3   11.4
2011 12 07    15 53.78   -46 18.1    0.716    0.470    26.5   11.2
2011 12 08    16 10.34   -44 31.1    0.727    0.434    23.8   10.9
2011 12 09    16 25.59   -42 34.2    0.742    0.397    21.1   10.6
2011 12 10    16 39.54   -40 28.8    0.759    0.358    18.5   10.3
2011 12 11    16 52.22   -38 15.8    0.780    0.316    15.8   10.0
2011 12 12    17 03.68   -35 55.6    0.804    0.272    13.1   9.5
2011 12 13    17 13.96   -33 27.7    0.833    0.223    10.4   8.9
2011 12 14    17 23.07   -30 48.9    0.869    0.169     7.7   8.0
2011 12 15    17 30.86   -27 50.3    0.914    0.105     4.7   6.5
2011 12 16    17 32.18   -23 05.4    0.989    0.006     0.2  -3.4
2011 12 17    17 16.52   -25 17.7    0.919    0.104     4.9   6.4
2011 12 18    17 10.86   -27 27.6    0.873    0.169     7.8   8.0
2011 12 19    17 06.90   -29 31.8    0.835    0.223    10.5   8.9
2011 12 20    17 03.78   -31 35.1    0.802    0.271    13.0   9.5
2011 12 21    17 01.19   -33 39.8    0.771    0.316    15.4   9.9

Extreme care is needed due to the comet's small solar elongation angle and close proximity to the Sun in the sky.

Congrats to Terry Lovejoy his third comet discovery!! On comets-ml mailing list you can read the full discovery  story written by Terry himself.

By Ernesto Guido, Giovanni Sostero & Nick Howes

Thursday, December 1, 2011

Update on 2011 RC17

M.P.E.C. 2011-W34, issued on 2011 Nov. 22, 02:33 UT, announced the discovery by Leonid Elenin (H15 ISON-NM Observatory, Mayhill) of a new unusual minor planet, with the temporary designation of 2011 RC17. At that time, its preliminary orbital solution provided a comet-like orbit, with a= 6.3 AU, e= 0.53, Incl. = 11.3 deg, and a period of nearly 16 years.

At first we observed this object on 2011 Nov. 22.4, remotely, through the Haleakala-Faulkes Telescope North 2.0-m f/10.0 Ritchey-Chretien + CCD. On our stacking it appearance was stellar, however we wanted to secure more images about it, in order to obtain a higher S/N, to make sure about its nature.

Then, on 2011, December 1.4, we were able to obtain another observing session through the Siding Spring-Faulkes Telescope South 2.0-m f/10.0 Ritchey-Chretien + CCD.

Stacking of 16 R-filtered exposures, 60-sec each, showed that this object had a stellar aspect, with its PSF profile being the same of the nearby field stars of similar brightness (FWHM of 1.4").

Our image of this object (click on it for a bigger version):

by Nick Howes, Giovanni Sostero and Ernesto Guido