On October 23, Comet Holmes was a faint comet. A large and very expensive amateur telescope, located far away from light pollution, was required to catch even a glimpse of it. But just 24 hours later, it was almost a million times brighter, and easily visible with the unaided eye - even from London!
While the stars all appear as points of light in the night sky, the comet appears noticeably larger and more diffused, even with the unaided eye (although, the comet currently has no tail).
You can find Comet Holmes throughout the night in the constellation of Perseus. Click on the sky map for a larger version (generated with Stellarium); the red line indicates the plane of our solar system, also the path that the Moon approximately moves along.
For the latest details, see SpaceWeather.com, which also has a frequently updated photo gallery of the comet.
But what has happened to Comet Holmes? Why did it suddenly brighten so much? Maybe part of the surface of the comet has cracked, and the newly exposed (water) ice beneath has been heated by the Sun and turned into a gas that now surrounds the nucleus of the comet.
Comet Holmes was originally discovered in 1892 by Edwin Holmes in London. His discovery was confirmed within days here at the Royal Observatory Greenwich. Holmes managed to discover the comet through a very similar event to what is currently occurring. In 1892, it suddenly brightened allowing Holmes to spot it, and it remained visible to the unaided eye for another 3 weeks until it faded away. 75 days later the comet once again brightened to unaided eye brightness!
But what will happen this time? Currently, the cloud of gas that surrounds the comet (which is making it appear so bright) continues to increase in size. The comet now appears larger in the sky than Jupiter, and some suggest that the cloud could appear as large as the Moon – although, if it did, the outermost gas would not be bright enough for us to see with the unaided eye.
So why not pop outside and see if you can spot it yourself?
Look towards the north to find Ursa Major – the back half of which is known as The Plough in the UK, a very familiar set of seven stars. The two front stars of the Plough point upwards towards Polaris, which is always due north. Just to the right of Polaris is the constellation of Cassiopeia, easy to spot thanks to its "W" shape. As you pan down from Cassiopeia, look for a triangle of stars... although, the bottom left of the triangle is Comet Holmes!
There are lots of other interesting (red!) objects in that area of sky, too. If you look up at 11pm (local time), you will notice that the Earth has moved around the Sun enough so that we can once again see the constellation of Orion. Betelgeuse, a red supergiant star, is visible at the top-left of Orion.
To the top-left of Betelgeuse is the very bright Mars, and to the top-right is the red giant star Aldebaran. Above Aldebaran is the cluster of seven stars known as the Pleiades, about the same size as the full Moon, and a beautiful sight through binoculars.
Above Mars is yet another red star, Capella. And coming full circle, above Capella is Comet Holmes.
Comet Holmes is currently over the north of our solar-system, between the orbits of Jupiter and Mars, and is heading towards the extreme of its elliptical orbit.
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