Electronic Telegram No. 2768 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: firstname.lastname@example.org (alternate email@example.com) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network COMET P/2011 NO1 L. Elenin (Lyubertsy, Russia) and I. Molotov (Moscow, Russia) report their discovery of an object with slight apparent cometary appearance on four 240-s unfiltered CCD exposures taken remotely with a 0.45-m f/2.8 astrograph at the ISON-NM observatory near Mayhill, NM, USA, on July 7.3 UT (discovery observation tabulated below). After posting on the Minor Planet Center's NEOCP webpage, several other CCD astrometrists have also commented on the object's cometary appearance. Stacked images taken by R. Holmes (Ashmore, IL, USA; 0.61-m f/4.0 astrograph; measured by S. Foglia and T. Vorobjov) on July 9.26 UT show a possible coma out to 8", while similar images taken on July 11.25 show an elongated shape 8" x 5" in shape extended in p.a. 247 deg; similar images from July 12.3 show the comet to be diffuse and of similar size (though no elongation mentioned). Foglia also adds that eight stacked 60-s images taken by P. Miller, P. Roche, A. Tripp, R. Holmes, R. Miles, L. Buzzi, and himself with the 2.0-m f/10 Ritchey-Chretien "Faulkes Telescope North" at Haleakala (and measured by Buzzi and Foglia) on July 13.6 show a diffuse coma of size 4" x 7", elongated in p.a. 244 deg. L. Buzzi (Varese, Italy, 0.38-m f/6.8 reflector; July 12.04-12.07) writes that stacked images taken in a hazy sky and at low altitude show the object to be diffuse, with the center of light difficult to measure. N. Howes, G. Sostero, and E. Guido report that thirteen stacked 20-s R-band images taken remotely with the 2.0-m f/10 Ritchey-Chretien "Faulkes Telescope South" at Siding Spring on July 12.5 in good seeing shows a coma about 2" in diameter, elongated toward the southwest, with a narrow 3" tail toward p.a. 250 deg. H. Sato (Tokyo, Japan) reports that images taken remotely with a 0.43-m f/6.8 reflector at Nerpio, Spain, in moonlight on July 14.0 show a diffuse coma 6" in diameter of red mag 18.6, with no tail visible. 2011 UT R.A. (2000) Decl. Mag. Observer July 7.30144 20 22 49.05 -19 39 34.9 19.5 Elenin This object was announced by T. Spahr as a minor planet on MPEC 2011-O09 while a CBET was being prepared to announce it as a comet, and he assigned the designation 2011 NO1 to it. The available astrometry, the following preliminary elliptical orbital elements by G. V. Williams, and an ephemeris appear on MPEC 2011-O10. T = 2011 Jan. 22.0172 TT Peri. = 264.0650 e = 0.775686 Node = 296.0592 2000.0 q = 1.244833 AU Incl. = 15.0324 a = 5.549505 AU n = 0.0753916 P = 13.07 years NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 July 19 (CBET 2768) Daniel W. E. Green
The object MG27A07 was discovered July 7th, during the course of a regular sky survey at our observatory, which became a year old on July 13th. The object’s rating (NEOR) was 100% and it was immediately placed on the NEOCP confirmation page. The speed of the new object was not high, on the order of 0.8 seconds of arc per minute, and in principle, nothing foreshadowed the discovery which eventually happened. It was necessary to continue observing.
July 8th, I again looked for this object, but didn’t see it on the images. Was it possible that the object was just an error on my part, and it didn’t really exist? Weather conditions the 7th were not the best; the object had appeared rather faint. Still, I remained certain of its existence. July 9th I again looked for the object. When I began the exposure, I saw on the NEOCP blog information that MG27A07 had been located by the American ARI Observatory (MPC code H21). Having taken my series, I also saw the object, but a little distance away from the position calculated from the observations of the first night. Later it turned out that in the new version of the program used at the observatory – CLT, error had crept in and inaccurate measurements were obtained. The calculations were done again by hand. By the way, as it came clear later, after correcting the orbit, MG27A07 was visible on several images from July 8th, but for the most part it was located on a starry background so that obtaining accurate measurements was not possible. But most important! After adding all 21 images from July 9th, the object looked like a comet! A coma was clearly visible. FWHM of the object was 5.8″, while at the same time, the average FWHM of the stars was no greater than 4.3″. This data was sent to the Central Bureau for Astronomical Telegrams, CBAT. On July 19 CBAT released a circular where the comet was assigned the designationP/2011 NO1.
Over the next several days, the cometary nature was confirmed by the ARI Observatory, and also by the 2-meter Faulkes Telescope South, FTS. I want to express my since gratitude for their work! Special thanks to all observers of T3 Project.
Preliminary orbital data say the comet is a short period comet with a period of about 13 years. At aphelion the comet goes out farther than the orbit of Saturn; at perihelion it comes in to 1.25 a.u. from the Sun and 0.38 a.u from the Earth orbit. For that reason the comet presents no danger to us. Closest approach to the Sun for this appartiion has already passed. This happened in the middle of January 2011. Because of its small elongation and its location in the southern sky, it went unnoticed, although it might have had a maximum brightness of about 16th magnitude. Now the comet is again receding from the Sun, and by Fall its brightness will fall below 21st magnitude. The next time the comet will return toward the Sun will be in 2024, but that is a different story.
Observations continue and more details will be published soon!
The new monthly MPC circular released – MPC 75355- 75550.
ISON-NM statistic for the previous month (June 9 – July 7):
Number of measurements: 5134
Measured objects: 1275
Discovered objects*: 5
Sky coverage: 485 sq. degrees
Observing nights**: 27
* – include new short-period comet P/2011 NO1
** – include partial nights
This has, undoubtedly, been one of the most eagerly-awaited comets in recent years. It was discovered back on December 10, 2010 by Leonid Elenin, an astronomer in Lyubertsy, Russia (affiliated with the Keldysh Institute of Applied Mathematics in Moscow), who is an accomplished observer of comets and who has in fact made several recoveries of expected periodic comets within the fairly recent past; this is his first comet discovery. Leonid was observing remotely with a 45-cm (18-inch) telescope (equipped with a CCD) at the International Scientific Optical Network observatory in New Mexico (not too far from where I live, incidentally), and at the time of his discovery the comet was a rather faint object between 19th and 20th magnitudes and was located 4.2 AU from the sun.
The first calculated orbits for Comet Elenin suggested it would remain a distant object, however it soon became clear that it was traveling on a remarkably low-inclination orbit (1.8 degrees) that would carry it quite close to both the sun and the earth. Furthermore, the geometry for forward scattering of sunlight — and thus an accompanying brightness enhancement — is quite favorable around that time. All this has led to a realization that Comet Elenin possesses at least the potential to become a relatively bright object — conceivably even a “Great Comet” — for a brief period of time around perihelion passage and its closest approach to Earth.
The SECCHI team requests to roll the Behind spacecraft by 135 degrees for two hours per day each day between Aug 1 (or late on Sep 31) and Aug 12 to observe comet Elenin as it flies within 0.05 AU of the spacecraft. Observations of the comet at a wide variety of phase angles will provide information about composition. There’s also a possibility that the in situ instruments on Behind will see the ion tail.
The requested two hours per day will include the roll and settle times, with the roll starting on an even hour boundary, and then back to nominal roll and settled on the next even hour boundary. A more detailed plan will be sent to APL (Applied Physics Laboratory of Johns Hopkins University).
The test of the roll maneuver to observe Comet Elenin from Behind is expected to be scheduled sometime in week 29 (July 18-24).