So what is the largest object in the solar system? If you said the sun, you’re correct. Well, normally you would be — but not right now.
Measurements from the University of Hawaii Institute for Astronomy have determined that Comet 17P/Holmes, which underwent a dramatic outburst back in October, is now slightly larger than the sun, making it the largest object in the solar system. The comet’s dusty coma/atmosphere is now 1.4 million kilometers (0.9 million miles) wide, making it larger in area that the sun. The coma is continuing to expand at a regular rate.
Here is a link to more information and a comparison image.
Here is a sky map for November showing the position of the comet, which is still easily seen from your backyard.
Here is a Gallery from Spaceweather.com of comet images that have been taken by astronomers.