A giant B star of magnitude 1.6. The name, of Latin origin, means female warrior.

The three stars Delta δ, Epsilon ε and Zeta ζ Orionis, forming the belt of the mythological figure of the constellation Orion.

Jewish astronomer and scholar, who lived in the first century CE. He is believed to have made the first known mention of Halley’s comet. The Mishna, a codification of Jewish oral law written approximately 200 CE, tells of Ben Hananiah referring to a star that appears every 70 years and induces navigational errors. Hananiah perfected the Jewish lunar calendar so that it is closely in synch with the solar year.

Comet Bennett.

An Italian/Dutch gamma- and X-ray satellite launched on 30 April 1996. Observations it made in 1997 led to the first optical identification of a gamma-ray burster.

English name for the constellation Coma Berenices.

A concept used in a convention for expressing time in dynamical calculations. The length of the Besselian year was originally defined as the period taken for the Sun’s right ascension to increase by 24 hours, and is almost equal to the length of a tropical year. In 1976, it was redefined as the length of the tropical year in 1900. The Besselian year is defined to commence at the instant when the Sun’s mean longitude is 280°. In practice, this falls close to the beginning of the calendar year. The simpler Julian year system is now usually preferred.

A type of giant B star that shows short-period variations in brightness and in its spectrum. These stars are variable because they pulsate. Their periods are under seven hours, and the light variation is no more than a tenth of a magnitude. The first such star to be discovered was Beta Cephei, and members of this class of variables are also known as Beta Cephei stars.

Beta Canis Majoris star.

Decay of a radioactive isotope resulting in the emission from the parent atomic nucleus of either an electron and an antineutrino, or a positron and a neutrino.

A member of a class of variable, binary stars of which Beta Lyrae is the prototype. Both members of the system are massive, but one has expanded to fill its Roche lobe. This causes material to flow towards the other star, which becomes surrounded by an obscuring accretion disc.

An electron or positron i.e. a particle with the same mass as an electron but opposite electric charge emitted from an atomic nucleus as a result of a nuclear reaction or in the course of radioactive decay.

A fourth magnitude A star, which is surrounded by a disc of material. Attention was focused on the star when it was found to be emitting strongly in the infrared. Optical observations confirmed the presence of the disc with a diameter about ten times the size of Pluto’s orbit round the Sun. It is believed that planetary systems, such as the solar system, form from such discs of matter around stars.

A highland region on the surface of Venus, dominated by two shield-shaped areas, Theia Mons and Rhea Mons, both of which rise to heights of over 4.5 kilometres 3 miles.

A red supergiant M star, one of the largest known. By means of speckle interferometry and other interference techniques, the star’s diameter has been measured directly and found to be about 1,000 times that of the Sun . The presence of large bright star-spots has also been revealed. Ultraviolet observations made with the Hubble Space Telescope showed Betelgeuse to be surrounded by an extended chromosphere. Its mass is about twenty times the Sun’s. The brightness varies irregularly between magnitudes 0.4 and 0.9 with a rough period of around five years.