As the names of three of its four main stars show, Libra was once the claws of the Scorpion, but the Romans hived it off to form Libra, the Scales, allegedly because the Moon was in Libra when Rome was founded in 753 BC. The scales represent justice and balanced days and nights, referring to the fact that the autumnal equinox was in Libra at the time. Scorpius is an ancient constellation and represents the scorpion that attacked Orion, hence Scorpius cannot be in the sky at the same time as Orion. We cannot really appreciate Scorpius in the UK as most of the constellation is below 26 degrees south (see Canis Major for a discussion of this cut-off point), including its realistic stinger. I have seen it completely in southern Sinai and it is a splendid sight. In Havering it looks like an umbrella that has been blown inside out. Libra is more difficult to make out. Three of the stars in the quadrilateral it forms are third magnitude, but they are reduced to fourth magnitude by extinction.

Zubenelgenubi (Alpha Librae) is a very wide double with a lime-yellow magnitude 2.7 primary and a yellow 5.2 secondary; the separation is 231 arcseconds. Zubeneschamali, the brightest star in Libra, is sometimes considered to be green or at least green-tinged, in opposition to the theory that no stars can be green. Its magnitude is 2.6 (reduced by extinction to 2.9). The Methuselah Star (HD 140283) [1], in the north of the constellation, was seemingly formed just after the Big Bang—the current estimate for its age is 12 billion years, having been put as high as 14.5 billion years. A magnitude 7.2 star, it is in a sparse field and can be seen with binoculars.

Scorpius has two interesting Messier star clusters—M6 (the Butterfly Cluster) and M7 (Ptolemy’s Cluster)—which are too far south for us to observe. The globular cluster Messier 4 [2] is nominally the second brightest globular cluster we can see in Havering and the largest one. Unfortunately, it is just 1.3 degrees to the right (west) of Antares and is affected by its glare. Furthermore, extinction, even when it is at its highest in the sky, reduces its magnitude from 5.4 to 6.0. M4 is 12.2 billion years old and, at a distance of 6,033 light years, is our closest globular cluster. If you view it in a telescope with a field of view of at least one and a half degrees, you may be able to see Antares, M4 and NGC 6144, a globular cluster which is both dim (mag. 9.6 reduced to 10.2) and small. Antares is a red supergiant, and would be more impressive if it was higher in our sky. Its magnitude is reduced from 1.1 to 1.7 thanks to extinction, even when it is at its highest above the horizon. Halfway between Antares and Acrab lies Messier 80 [3], a globular cluster which lies between the other two globular clusters in brightness and size; it has a magnitude of 7.3 (reduced to 7.8). It is extremely old, with an age of 13.5 billion years, and it lies 32,600 light years away.

Scorpius has three lovely double stars. Acrab is a white and blue pair, with a comfortable separation of 13.4 arcseconds; the magnitudes are 2.6 and 4.5. A degree below Acrab is a pair of stars which form a very wide double, but lack official status. Omega1 and Omega2 Scorpii are 877 arcseconds apart and are magnitude 3.9 and 4.3; they are both white or white and yellow-white. One and half degrees to the east (left) of Acrab is Jabbah, which is a quadruple star. The primary (A) and the first companion (B) are a very tight pair of magnitude 4.4 and 5.3 stars with a separation of 1.4 arcseconds, which will require a fairly large telescope (127mm should be OK) and a high magnification. The next companion (CD) is much easier to resolve, with a separation of 41.3 arcseconds. Again, with a larger telescope and high magnification, one can split C (mag. 6.6) and D (mag. 7.2), which have a separation of 2.4 arcseconds. Amazingly all these stars are in a gravitationally bound system and they are all white.

Finally, there is Xi (or Ksi) Scorpii; a pair of extremely close (sep. 1.1 arcseconds) amber-yellow stars of equal brightness (mag. 4.84 and 4.86), which will require a large telescope (ideally 150mm or more) and a high magnification. The equal brightness means this pair is a good test of the ability of a telescope to split doubles. The orbital period is 46 years and it is closing. There is a third blue star (C), which is much wider, but still close (sep. 7.2); it is magnitude 7.3. Just 280 arcseconds away from Xi Scorpii to the south-east—and almost certainly in the same field of view—is a dimmer double, Struve 1999, comprised of almost equally bright tangerine-orange stars (mag. 7.4 and 8.0) with a reasonable separation of 11.9 arcseconds.

Double star images below are schematic representations.