Comet 17P Holmes blazes away in this raw image from an observatory at PetitJeanMountain in Arkansas. The usually dim comet suddenly brightened by 400,000 times in less than 24 hours, and has now reached a magnitude (2.0) approaching the brightest stars and clearly visible to the naked eye.

Comets can undergo sudden mysterious outbursts in brightness. When Holmes was first discovered in 1892, it was at magnitude 4.0 – but was no brighter than magnitude 17 in mid-October of this year, making it 25,000 times fainter than the faintest star visible to the naked eye. Another mysterious feature of Holmes is the lack of a tail or other irregularity.

Comet Holmes will appear high in the northern night skies over the next few weeks, never rising or setting as it lurks in the constellation Perseus. Even while shining for human observers, the object still remains 151 million miles (243 million kilometers) away from Earth.

–Arkansas Sky Observatories/Clay Sherrod and SPACE.com Staff

Credit: Arkansas Sky Observatories/Clay Sherrod