The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 54 galaxies (including dwarf galaxies), with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy. The galaxies of the Local Group cover a diameter of 10 megalight-years (3.1 megaparsecs) (see 1 E+22 m for distance comparisons) and have a binary (dumbbell) distribution. The group is estimated to have a total mass of 1.29±0.14 ×10¹²M_☉ and has a velocity dispersion of 61±8 km/s. The group itself is part of the Virgo Supercluster (i.e. the Local Supercluster).

The two most massive members of the group are the Milky Way and the Andromeda Galaxy. These two spiral galaxies each have a system of satellite galaxies.

The other members of the group are gravitationally secluded from these large subgroups: IC10, IC1613, Phoenix Dwarf, Leo A, Tucana Dwarf, Cetus Dwarf, Pegasus Dwarf Irregular, Wolf-Lundmark-Melotte, Aquarius Dwarf, and Sagittarius Dwarf Irregular.

Carl Edward Sagan ( /ˈseɪɡɪn/; November 9, 1934 – December 20, 1996) was an American astronomer, astrophysicist, cosmologist, author, science popularizer, and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books. He advocated scientifically skeptical inquiry and the scientific method, pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI).

Sagan is known for his popular science books and for the award-winning 1980 television series Cosmos: A Personal Voyage, which he narrated and co-wrote. The book Cosmos was published to accompany the series. Sagan wrote the novel Contact, the basis for a 1997 film of the same name.

Carl Sagan was born in Brooklyn, New York, to a Ukrainian Jewish family. His father, Sam Sagan, was an immigrant garment worker from Kamenets-Podolsk, Ukraine; his mother, Rachel Molly Gruber, a housewife. Carl was named in honor of Rachel's biological mother, Chaiya Clara, in Sagan's words, "the mother she never knew." Sagan graduated from Rahway High School in Rahway, New Jersey, in 1951.

Victor Pemberton (born 10 October 1931) is a British writer and television producer.

Victor Pemberton's scriptwriting work included BBC radio plays, and television scripts for the BBC and ITV, including Doctor Who, The Slide and The Adventures of Black Beauty.

His television production work included the British version of Fraggle Rock (second series onwards), and several independent documentaries including the 1989 International Emmy Award-winning Gwen: A Juliet Remembered, about stage actress Gwen Ffrangcon-Davies.

In his earlier years Pemberton had several small screen acting roles. In addition to novelisations, he has written many nostalgic novels set in London, prompted by the success of his autobiographical radio drama series Our Family.

Pemberton grew up in Islington, London, and lived for many years in Essex. He now lives in Spain, where he continues to write novels.

Pemberton wrote the 1968 Patrick Troughton story Fury from the Deep (which he subsequently novelised for Target Books). The story, now missing from the BBC archives, was based on an earlier stand-alone radio serial he had written called The Slide, starring future Master actor Roger Delgado. It introduced the Doctor's trademark sonic screwdriver. He was also story editor of season five opener The Tomb of the Cybermen.

Deborah Watling (born 2 January 1948) is a British actress best known for her role as Victoria Waterfield, a companion of the Second Doctor in the BBC television series Doctor Who.

Watling was born at Fulmer, Buckinghamshire, the daughter of actors Jack Watling and Patricia Hicks. Her sister Dilys and her brother Giles are also actors. Beginning as a child actress, she had a regular role as the niece of Peter Brady in The Invisible Man (1958) television series. She was later cast for the lead role in Alice (1965), Dennis Potter's version of Alice's Adventures in Wonderland, for the BBC's The Wednesday Play, a small role in That'll Be the Day (1973) and as Norma Baker in the ITV series Danger UXB (1979).

Watling played Victoria in Doctor Who from 1967 to 1968, though owing to the BBC's wiping policy of the time, The Tomb of the Cybermen (1967) is the only serial she appeared in to still exist in its entirety. She also appeared in Dimensions in Time (1993) and Downtime (1995). She co-starred with Cliff Richard in the 1970s film Take Me High.