"lemniscate-oval vacuity" when first describing it, and subsequently referred to it simply as the "oval vacuity". The term lemniscate continued to be used to describe this portion of the nebula until popular astronomy writer Emma Converse described the shape of the nebula as "resembling a keyhole" in an 1873 Appleton's Journal article. The name Keyhole Nebula then came into common use, sometimes for the Keyhole itself, sometimes to describe the whole of the Carina Nebula (signifying "the nebula that contains the Keyhole"). The diameter of the Keyhole structure is approximately . Its appearance has changed significantly since it was first observed, possibly due to changes in the ionizing radiation from Eta Carinae. The Keyhole does not have its own NGC designation. It is sometimes erroneously called NGC 3324, but that catalogue designation refers to a reflection and emission nebula just northwest of the Carina Nebula (or to its embedded star cluster). Defiant Finger A small Bok globule in the Keyhole Nebula (at RA 10h44m30s, Dec −59°40') has been photographed by the Hubble Space Telescope and is nicknamed the "Carina Defiant Finger" due to its shape. In Hubble images, light can be seen radiating off the edges of the globule; this is especially visible in the southern tip, where the "finger" is. It is thought that the Defiant Finger is being ionized by the bright Wolf–Rayet star WR 25, and/or Trumpler 16-244, a bright blue supergiant. It has a mass of at least , and stars may be forming within it. Like other interstellar clouds under intense radiation, the Defiant Finger will eventually be completely evaporated; for this cloud the time frame is predicted to be 200,000 to 1,000,000 years. Trumpler 14 Trumpler 14 is an open cluster with a diameter of , located within the inner regions of the Carina Nebula, approximately from Earth. It is one of the main clusters of the stellar association, which is the largest association in the Carina Nebula. About 2,000 stars have been identified in . and the total mass of the cluster is estimated to be . Trumpler 15 Trumpler 15 is a star cluster on the north-east edge of the Carina Nebula. Early studies disagreed about the distance, but astrometric measurements by the Gaia mission have confirmed that it is the same distance as the rest of Carina OB1. Trumpler 16 Trumpler 16 is one of the main clusters of the Carina