ASASSN Sept 25, 2017 18:06:02 GMT
Post by nighthawk on Sept 25, 2017 18:06:02 GMT
A recently discovered comet will be visible in binoculars during the next couple of months. But when we say ‘visible’, don’t expect to see anything spectacular. If early images are anything to go by, this will be a faint blob rather than a mini version of Halley’s Comet.
The comet was discovered in July by an automated supernova search survey, the "All-Sky Automated Survey for Supernovae" (ASASSN) at Cerro Tololo Inter-American Observatory in Chile – hence the odd name, which caused consternation among those whose task it is to name a comet. (Note the spelling if you search online!) Its designation is C/2017 O1. When discovered it was 15th magnitude, but as it has neared the Sun it has brightened and is now around magnitude 9.
It is moving slowly through the stars of Taurus, and will remain there until the end of September, when it moves into Perseus and reaches its greatest brightness of about magnitude 7.5. So it will be visible in an increasingly accessible part of the sky for some time to come. Taurus and Perseus are rising in the east after midnight, and by October the comet will be well-placed in the evening sky around midnight, and visible earlier in the evening. The comet always remains beyond the orbit of Mars, and will not get close to us. It has an orbital period of around 3600 years, so won't be back in the vicinity of the Sun until the 57th century!
Although stars of magnitude 7 or 8 are easily visible in binoculars, a comet of this brightness is usually less easy to see as its brightness is spread out over a wider area and is not a point source. So fairly dark skies will be needed for the best views.
The chart at top shows the region through which Comet ASASSN travels, with the horizon as seen at about midnight BST in mid September. The area is easy to find, with the bright star Aldebaran and the well-known Pleiades or Seven Sisters cluster as signposts. Click on the chart to get a detailed track, with stars shown to magnitude 8. The maps were generated using the SkyMap program. For a table of predicted positions see below the Gallery.