Comet 2011 L4 (PanSTARRS) is currently in the evening sky. In the past week or two it has been visible with the naked eye from the southern hemisphere, even from cities, so we are hoping for a similar show as seen from the UK. However, news stories that suggest that it may be easily visible this week are based on US information, as it will be slightly higher in the sky from the US than in the UK. But if you have a low, clear, western horizon and it is really clear, you may be in luck.
According to Jonathan Shanklin, Comet Section director, ‘Comet 2011 L4 is doing much better than the early indications suggested, though there is no immediately obvious reason why it should be significantly brighter than the mean light curve. It will be interesting to see if this behaviour continues, and if it does then the comet might be around 0 magnitude by the time the first visual observations are made from the UK in mid March.
Where to look
The chart above shows its positions in the evening sky looking due west during the second half of March and into April. Click on the chart for a larger version.
The brightness’s shown are only a guide, and refer to the total brightness of the comet, which of course is spread over an area of sky. Although magnitude 1 seems bright, even a star of this brightness would be hard to see against the twilight sky, and a comet would be less easily seen.
The horizon position is shown for Tuesday 12th March at 18.35, with the Sun 5º below the horizon as seen from the southern UK. The comet at this time is 7º above the horizon. As the month goes on, the comet gets higher and fainter, but will be farther from the Sun so it should be easier to see.
By the time the sky gets properly dark, at 20.16 on 25th March, for example, the comet will still be 5º above the horizon, though the nearly the full Moon on the opposite side of the sky will not be a help. Again, really good clear skies will make all the difference, and light pollution will be a problem from towns. Binoculars will help wherever you are.
A few days later, the comet will be getting close to the Andromeda Galaxy in the sky and could make a nice binocular and photographic target.
Further into April, the comet will be in Cassiopeia and possibly around 4th magnitude, so could still be visible with binoculars and the naked eye in good skies.
How many PanSTARRS?
There are many comets discovered by the PanSTARRS search team, which is why astronomers like to use its full designation of 2011 L4 (PanSTARRS).
What about Comet ISON?
It’s too soon yet to say whether Comet ISON, due to come close to the Sun at the end of November, will be as spectacular as some predictions suggest. Though it could become as bright as the Moon for a short period, at this time it will be very close to the Sun and will be very hard to observe. From the UK, the Sun will be low in the sky and usually there is a lot of haze around, making things even more difficult.
In early December the comet will be in the evening sky as seen from the UK, but on realistic predictions may be no brighter than Comet 2011 L4. So make the most of the latest Comet PanSTARRS!