Comet on April 16, 1996
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Comets are basically frozen balls of ice and dust of approximate diameter 10 km. As they get near the sun and are heated, the cometary material is vaporized and thus releasing the entrapped dust and gas. Often times there are rapid changes in the appearance of the comet nucleus and coma as streams of dust and gas come off the nucleus. This can result in an asymmetric appearance as shown in the this most recent image taken at the NTT at ESO . Gas streaming off the comet nucleus forms the ion tail of the comet which points directly away from the sun due to interaction with the solar wind. This can be seen here in this recent image taken at La Silla with the 1-m telescope.
A cometary spectrum, shown below, generally reveals highly ionized emission lines of various C, CH and CN molecules which previously were stored in frozen form. Indeed, bombardment of the early earth by this material may have delivered many of the volatiles important to initiate chemical reactions in the early earth that synthesized amino acids. Hence, comets may really be your best friend and may have been the source of most of the earth's water.
Astronomical Headlines of the IAU Central Bureau for
Astronomical Telegrams
Jet Propulsion Laboratory (JPL)
Instituto de Astrofisica de Canarias
Laboratorio Nacional de Astrofisica (Brazil)
University of Melbourne (Australia)
Crni Vrh Observatory (Slovenia)
University of Hawaii (D. Jewitt - submm work)
Vereinigung der
Sternfreunde (VdS). In English and German.
Sky & Telescope (with charts showing the comet's
motion in the sky in March and April 1996).
Astronomy Magazine (with charts).
This comet will pass within 10 million miles of the earth at its closest which will cause some to claim this a near-miss or even some predictions that it will hit the earth. Well, we will know in a week. The orbit is highly inclined with respect to plane of the solar system as shown below:
The manifestation of this high inclination is the rapid movement in the sky of the comet from south to North. On March 25 the comet will be at its point of closest approach. Although cometary brightnesses are notoriously difficult to accurately predict, this one is being well-studied and is evolving fairly rapidly. It is estimated to reach an integrated magntiude of +1 by March 25. This is as bright as the brightest appearing stars in the sky. However, the comet is not point like but is well-resolved and hence this brightness is spread out over some area. As such, the comet is best viewed from a dark location. The full extent of the Coma (the region of ionized gas around the nucleus) will likely be 1--2 degrees. The dust tail, illuminated via reflected sunlight, will be 15--25 degrees but rather diffuse.
The path of the comet through the sky is shown here. On March 24 the comet will be relatively close to the bright red star Arcturus. It should not be difficult to see.
The empheremis or positional data is shown here: Note the very rapid movement of the comet, almost 10 degrees per day. This makes telescopic observations really, really difficult!
Date (UT) Hr R.A. J2000 Dec. 1996 Mar 21 00 14 52 14.69 +05 06 41.3 1996 Mar 21 02 14 52 07.77 +05 38 40.4 1996 Mar 21 04 14 52 00.63 +06 11 29.8 1996 Mar 21 06 14 51 53.24 +06 45 11.0 1996 Mar 21 08 14 51 45.61 +07 19 45.9 1996 Mar 21 10 14 51 37.71 +07 55 15.9 1996 Mar 21 12 14 51 29.55 +08 31 43.0 1996 Mar 21 14 14 51 21.10 +09 09 08.9 1996 Mar 21 16 14 51 12.35 +09 47 35.5 1996 Mar 21 18 14 51 03.30 +10 27 04.5 1996 Mar 21 20 14 50 53.92 +11 07 38.0 1996 Mar 21 22 14 50 44.21 +11 49 17.9 1996 Mar 22 00 14 50 34.14 +12 32 06.2 1996 Mar 22 02 14 50 23.70 +13 16 04.8 1996 Mar 22 04 14 50 12.86 +14 01 15.8 1996 Mar 22 06 14 50 01.62 +14 47 41.2 1996 Mar 22 08 14 49 49.95 +15 35 23.0 1996 Mar 22 10 14 49 37.83 +16 24 23.3 1996 Mar 22 12 14 49 25.23 +17 14 44.1 1996 Mar 22 14 14 49 12.13 +18 06 27.4 1996 Mar 22 16 14 48 58.51 +18 59 35.1 1996 Mar 22 18 14 48 44.32 +19 54 09.1 1996 Mar 22 20 14 48 29.54 +20 50 11.1 1996 Mar 22 22 14 48 14.13 +21 47 43.1 1996 Mar 23 00 14 47 58.06 +22 46 46.5 1996 Mar 23 02 14 47 41.29 +23 47 22.8 1996 Mar 23 04 14 47 23.77 +24 49 33.4 1996 Mar 23 06 14 47 05.46 +25 53 19.5 1996 Mar 23 08 14 46 46.30 +26 58 41.9 1996 Mar 23 10 14 46 26.23 +28 05 41.4 1996 Mar 23 12 14 46 05.21 +29 14 18.5 1996 Mar 23 14 14 45 43.15 +30 24 33.3 1996 Mar 23 16 14 45 19.98 +31 36 25.6 1996 Mar 23 18 14 44 55.63 +32 49 54.9 1996 Mar 23 20 14 44 30.00 +34 05 00.4 1996 Mar 23 22 14 44 02.99 +35 21 40.7 1996 Mar 24 00 14 43 34.50 +36 39 54.1 1996 Mar 24 02 14 43 04.40 +37 59 38.3 1996 Mar 24 04 14 42 32.56 +39 20 50.6 1996 Mar 24 06 14 41 58.84 +40 43 27.9 1996 Mar 24 08 14 41 23.05 +42 07 26.5 1996 Mar 24 10 14 40 45.01 +43 32 41.9 1996 Mar 24 12 14 40 04.51 +44 59 09.6 1996 Mar 24 14 14 39 21.31 +46 26 44.3 1996 Mar 24 16 14 38 35.13 +47 55 20.0 1996 Mar 24 18 14 37 45.67 +49 24 50.5 1996 Mar 24 20 14 36 52.56 +50 55 09.2 1996 Mar 24 22 14 35 55.39 +52 26 08.8 1996 Mar 25 00 14 34 53.70 +53 57 41.8 1996 Mar 25 02 14 33 46.93 +55 29 40.3 1996 Mar 25 04 14 32 34.44 +57 01 56.1 1996 Mar 25 06 14 31 15.47 +58 34 21.0 1996 Mar 25 08 14 29 49.12 +60 06 46.3 1996 Mar 25 10 14 28 14.34 +61 39 03.4 1996 Mar 25 12 14 26 29.84 +63 11 03.7 1996 Mar 25 14 14 24 34.05 +64 42 38.2 1996 Mar 25 16 14 22 25.10 +66 13 38.4 1996 Mar 25 18 14 20 00.62 +67 43 55.6 1996 Mar 25 20 14 17 17.69 +69 13 21.0 1996 Mar 25 22 14 14 12.60 +70 41 46.1 1996 Mar 26 00 14 10 40.59 +72 09 02.1 1996 Mar 26 02 14 06 35.47 +73 35 00.0 1996 Mar 26 04 14 01 49.04 +74 59 30.3 1996 Mar 26 06 13 56 10.25 +76 22 22.5 1996 Mar 26 08 13 49 23.86 +77 43 24.8 1996 Mar 26 10 13 41 08.40 +79 02 22.6 1996 Mar 26 12 13 30 52.83 +80 18 56.8 1996 Mar 26 14 13 17 51.14 +81 32 40.9 1996 Mar 26 16 13 00 53.49 +82 42 55.3 1996 Mar 26 18 12 38 12.31 +83 48 36.9 1996 Mar 26 20 12 07 04.52 +84 48 01.0 1996 Mar 26 22 11 23 46.77 +85 38 11.1 1996 Mar 27 00 10 24 56.84 +86 14 28.5 1996 Mar 27 02 09 12 26.42 +86 31 15.2 1996 Mar 27 04 07 57 54.11 +86 25 31.3 1996 Mar 27 06 06 54 50.42 +86 00 16.4 1996 Mar 27 08 06 07 37.09 +85 21 55.5 1996 Mar 27 10 05 33 37.48 +84 36 03.1 1996 Mar 27 12 05 08 59.18 +83 46 12.9 1996 Mar 27 14 04 50 41.90 +82 54 29.0 1996 Mar 27 16 04 36 44.95 +82 02 02.9 1996 Mar 27 18 04 25 49.99 +81 09 36.7 1996 Mar 27 20 04 17 05.67 +80 17 36.0 1996 Mar 27 22 04 09 57.59 +79 26 16.7 1996 Mar 28 00 04 04 02.11 +78 35 48.7 1996 Mar 28 02 03 59 02.57 +77 46 18.4 1996 Mar 28 04 03 54 46.95 +76 57 49.6 1996 Mar 28 06 03 51 06.37 +76 10 24.7 1996 Mar 28 08 03 47 54.19 +75 24 04.8 1996 Mar 28 10 03 45 05.29 +74 38 50.2 1996 Mar 28 12 03 42 35.73 +73 54 40.7 1996 Mar 28 14 03 40 22.38 +73 11 35.9 1996 Mar 28 16 03 38 22.76 +72 29 34.9 1996 Mar 28 18 03 36 34.86 +71 48 36.5 1996 Mar 28 20 03 34 57.04 +71 08 39.6 1996 Mar 28 22 03 33 27.95 +70 29 42.9 1996 Mar 29 00 03 32 06.47 +69 51 44.8 1996 Mar 29 02 03 30 51.67 +69 14 44.1 1996 Mar 29 04 03 29 42.75 +68 38 39.2 1996 Mar 29 06 03 28 39.05 +68 03 28.7 1996 Mar 29 08 03 27 39.99 +67 29 11.0 1996 Mar 29 10 03 26 45.07 +66 55 44.6 1996 Mar 29 12 03 25 53.87 +66 23 08.2 1996 Mar 29 14 03 25 06.02 +65 51 20.2 1996 Mar 29 16 03 24 21.20 +65 20 19.2 1996 Mar 29 18 03 23 39.13 +64 50 03.9 1996 Mar 29 20 03 22 59.55 +64 20 32.8 1996 Mar 29 22 03 22 22.25 +63 51 44.7
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