The excitement continues with a close encounter of the asteroid kind. Ceres and Vesta appear closer to each other in early July than they have since astronomers discovered them in the 19th century’s first decade. On the evening of July 1, just 19' separate them. The gap closes to 10' — one-third the Full Moon’s diameter — on the 4th and 5th. Although they glow brightly enough to spot through binoculars, you’ll get a real thrill from seeing both in the same telescopic field.
Ceres is the largest object in the main asteroid belt between the orbits of Mars and Jupiter. Its gravity molds it into a spherical shape, which is why astronomers also refer to it as a dwarf planet. Despite its size, Ceres typically is not the brightest object in the asteroid belt. Vesta’s surface reflects a greater percentage of the light that hits it than Ceres does, and because it orbits closer to the Sun than its sibling, Vesta also receives more light. Ceres shines at magnitude 8.4 in early July, some three times dimmer than magnitude 7.1 Vesta.
To find the pair, start at 3rd-magnitude Zeta (ζ) Virginis. During early July, both asteroids lie within 1.5° of this star. The finder chart below shows stars to magnitude 8.8, so you should be able to tell which points of light are Ceres and Vesta.
For those of you without optics, Slooh.com
will highlight the two events Thursday night, July 3, starting at 8 p.m. EDT (0h UT July 4), live from Slooh observatories located in the Northern and Southern Hemispheres. The Northern Hemisphere observatory is located off the west coast of Africa, at the Institute of Astrophysics of the Canary Islands, and the Southern hemisphere Observatory is located at the Pontificia Universidad Católica de Chile near Santiago. You can watch the live coverage below.