Dwarf planet Ceres and Vesta the brightest asteroid both reach opposition in April and are currently positioned close together in Virgo, just northeast of Spica (α Vir) and Mars. Both objects are visible in binoculars as they travel quickly against the "fixed" background stars; their movements can even be tracked on a night-by-night basis.

Discovery

On January 1, 1801, Italian Catholic priest and astronomer Giuseppe Piazzi discovered Ceres, originally believing it to be a comet. This new object between the orbits of Mars and Jupiter was initially classified as a planet and subsequently given its own planetary symbol. However with further discoveries all in the same region of the Solar System, the general term asteroids were coined to describe them. Much later in 2006, the International Astronomical Union (IAU) defined a new classification of dwarf planet of which Ceres is now a member. It has a diameter of 975 kilometres (610 miles) and can peak at apparent magnitude +6.7, beyond naked eye visibility but easy with binoculars.

Vesta was the fourth asteroid to be discovered on March 29, 1807 by German astronomer Heinrich Wilhelm Olbers. Despite being only the third largest body in the main asteroid belt - diameter 530 kilometres (330 miles) - Vesta is the brightest asteroid. It appears brighter than Ceres and the slightly larger Pallas since its approaches closer to Earth and has a much higher reflective surface. At favourable oppositions, the maximum apparent magnitude of Vesta is +5.1, putting it within naked eye visibility.

Location

This year Vesta reaches opposition on April 13th (mag. +5.8) with Ceres reaching opposition on April 15th (mag. +6.9). The pair have not been this close together in the night sky - during an opposition period - for hundreds of years. During April they are positioned about 16 degrees northeast of Spica (α Vir - mag. +1.0). The much brighter red-orange Mars (mag. -1.5) starts the month just north of Spica but then quickly moves out westwards due its retrograde motion. Like Mars, Ceres and Vesta are also currently moving retrograde but since they are more distant they don't travel as fast against the constellation backdrop.

During April, Ceres is positioned 2.5 degrees northeast of Vesta with the latter being about 3 times brighter. Theoretically Vesta can be seen with the unaided eye, but this requires very dark skies. The two objects are so close together that they can be seen in the same binocular field of view.

At opposition, Vesta and Ceres are 1.232 AU (approx. 184.3 million kilometres or 114.5 million miles) and 1.644 AU (approx. 245.9 million kilometres or 152.8 million miles) distant from Earth respectively. Later on July 5th, Ceres and Vesta will be separated by just 10 arc minutes but by then they will have faded to magnitudes +7.4 and +6.2 respectively.

Night sky positions of Ceres, Vesta and Mars during April 2014 - pdf format

Ceres Data Table - April 2014

Vesta Data Table - April 2014