Asteroid 2 Pallas reaches opposition in Vulpecula on 13 July

Asteroid 2 Pallas reaches opposition in Vulpecula on 13 July when it will appear at mag. +9.6. Pallas starts the month just over a degree northwest of the line-of-sight star pairing formed from mag. +4.8, 1 Vulpeculae and mag. +5.7, 1 Sagittae. If nothing else, Pallas remains steady in brightness, staying at mag. +9.6 all month long. Its apparent motion against the background stars has it tracking west, arcing more and more southwest as the month progresses. As it goes, it clips the northwest corner of Sagitta before finally ending up in Hercules, close to mag. +5.9 TYC 1592-988-1 at the end of July. Its starting location puts it not too far from the asterism Collinder 399, which is also known as Brocchi’s Cluster or more familiarly as the Coathanger Cluster due to the shape it forms.

As suggested by its prefix number, 2 Pallas was the second minor planet discovered. It was found by the German astronomer Heinrich Olbers on 28 March 1802. Olbers is probably best known for the Olbers’ paradox, which questions why the sky is dark if the Universe is truly infinite. Pallas’s discovery came relatively soon after the discovery of 1 Ceres on 1 January 1801 by Giuseppe Piazzi.

Pallas is a large main belt asteroid with a mean diameter of 512km. It contains an estimated 7% of the mass of the asteroid belt. It’s classified as a B-type asteroid. These are carbonaceous bodies showing minor variations in spectral colour and are slightly more reflective than the more common C-type objects.

Pallas takes 4.62 years to orbit the Sun, its solar distance varying between 3.42 and 2.13 AU. Its orbit is highly inclined, tilted by 34.8° to the plane of the asteroid belt. It’s the third largest body in the asteroid belt after dwarf planet Ceres and minor planet Vesta. At its brightest, Pallas can reach mag. +6.7.

2 Pallas begins July near Collinder 399, the Coathanger Cluster

3. NGC 7160

With direct vision, NGC 7160 appears as a tiny knot of stars that could be mistaken for a globular cluster, but averted vision reveals it to be a sparse, small (about 5 arcminutes across) oval cluster. Note two brighter stars near the centre, the brighter of which is the slightly variable contactbinary star, EM Cephei. Contact binaries are binary stars that are so close together that their outer layers meet.  SEEN IT 15x 70

4. U Cephei

Continue a line from Iota (ι) Cephei through Errai (Gamma (γ) Cephei) for a further 5.5° where, midway between two mag. +5.6 stars, you’ll find the eclipsing variable star, U Cephei. Its magnitude range is +6.8 to +9.2, a nine-fold variation in brightness, that makes the variability easy to detect. Its period of 2.5 days means that, if you observe an eclipse, you can repeat the observation five days later at the same time.  SEEN IT 10x 50