The rumor is running around the various astronomy sites and listservers that Comet C/2011 W3 Lovejoy might be daytime visible. Will it be? That is a very qualified maybe.
This sun-grazer comet was discovered just a few days ago, on November 27th, by Australian amateur astronomer Terry Lovejoy. The comet is a member of the Kreutz comet family, and like other members of the family it will approach the Sun quite closely, about 548,000 miles (882,000 km) from the Sun. Of course those distances are solar centric distances. Taking the radius of the Sun into account means that the comet will be a mere 115,000 miles (186,000 km) above the photosphere, hot indeed!
It becomes a valid question to ask if comet Lovejoy will even survive perihelion transit.
Passing that close to the Sun will mean that the volatile elements of the comet will be streaming off the comet at a fantastic rate, enough to dramatically brighten the comet. Below you will find the ephemeris for perihelion on Dec 16th (Dec 15th HST) from the Minor Planet Center. As you can note, the predicted magnitude is -8! This is bright enough to be seen in broad daylight. Thus the possibility of a daytime comet.
The catch is that the comet will be quite close to the Sun. Within 2° as the Sun and comet rise on the morning of the 15th here in Hawai’i. For observers in the islands the best chance to look is on the morning of the 15th, as perihelion will occur in the afternoon as the comet passed behind the Sun from our point of view.
Will it be visible? Maybe. It depends on the accuracy of the magnitude estimates, which are uncertain to say the least. It could be substantially dimmer, or even substantially brighter than forecast under such conditions. The proximity to the Sun also complicates the issue. It is worth a look, seeing a daytime comet is highly unusual.
If you do look please take a few simple precautions… Do NOT use any sort of optical aid this close to the Sun, the risk of permanent eye damage is too great. If it is bright enough the comet should be a naked eye object. It will greatly help to position yourself to put the Sun just behind some obstruction. A building, a streetlight, anything to block the Sun’s glare and aid in picking out the comet. On the morning of the 15th the comet will rise 2° behind the Sun, thus 2° lower in the sky.
Give it a try!
12 Date TT R. A. (2000) Decl. Delta r Elong. Phase m1 m22011 12 05 15 16 55.0 -49 16 23 0.7020 0.5385 31.9 104.4 10.5 16.7<br>2011 12 06 15 35 50.9 -47 54 07 0.7082 0.5050 29.3 107.4 10.3 16.8<br>2011 12 07 15 53 36.9 -46 18 58 0.7170 0.4704 26.6 110.4 10.0 16.8<br>2011 12 08 16 10 07.0 -44 32 30 0.7285 0.4344 23.9 113.4 9.7 16.9<br>2011 12 09 16 25 18.7 -42 36 14 0.7429 0.3970 21.2 116.2 9.3 16.9<br>2011 12 10 16 39 12.4 -40 31 31 0.7604 0.3576 18.5 119.0 8.9 16.9<br>2011 12 11 16 51 50.3 -38 19 18 0.7813 0.3161 15.9 121.7 8.5 16.9<br>2011 12 12 17 03 15.7 -35 59 57 0.8060 0.2716 13.2 124.2 7.9 16.9<br>2011 12 13 17 13 31.2 -33 32 42 0.8352 0.2233 10.5 126.5 7.1 16.7<br>2011 12 14 17 22 37.5 -30 54 29 0.8705 0.1691 7.7 128.3 6.0 16.4<br>2011 12 15 17 30 26.9 -27 55 51 0.9153 0.1048 4.8 128.7 4.0 15.5<br>2011 12 16 17 31 43.4 -23 03 22 0.9885 0.0057 0.2 42.0 -8.5 5.4<br>2011 12 17 17 17 12.6 -25 07 18 0.9135 0.1046 4.7 130.1 4.0 15.6<br>2011 12 18 17 11 57.9 -27 12 24 0.8656 0.1692 7.5 130.6 6.0 16.6<br>2011 12 19 17 08 21.5 -29 13 16 0.8260 0.2234 10.1 129.7 7.1 17.0<br>2011 12 20 17 05 34.5 -31 14 08 0.7912 0.2717 12.5 128.6 7.8 17.2<br>2011 12 21 17 03 19.7 -33 17 03 0.7597 0.3162 14.8 127.2 8.4 17.3