Short answers, pulled from the story.
Michael E. Brown and the W. M. Keck Observatory's adaptive optics team discovered Hiʻiaka on the 26th of January 2005, observing from Mauna Kea, Hawaii. It was the first satellite ever found orbiting Haumea.
Hiʻiaka is named after a Hawaiian goddess who is the patron of hula and one of the daughters of the fertility goddess Haumea. The International Astronomical Union formally approved the name, along with Haumea and Namaka, on the 17th of September 2008.
Hiʻiaka has a volume-equivalent diameter of 370 kilometers, making it the sixth-largest known moon of any trans-Neptunian object. It ranks behind Charon, Dysnomia, Vanth, Ilmarë, and Actaea in size.
Hiʻiaka completes a slightly elliptical orbit around Haumea every 49.5 days, at a distance of about 49400 kilometers. It also rotates on its own axis every 9.68 hours, a period that is not tidally locked to Haumea.
Hiʻiaka has a very high geometric albedo of 0.74, notably higher than Haumea's own albedo of 0.51. Its surface is covered in crystalline water ice. Its deeper absorption features suggest that ice is fresher, purer, or made of larger grains than Haumea's.
Hiʻiaka is believed to be a fragment ejected from Haumea after a giant impact about 4.4 billion years ago. That impact happened within the solar system's first 77-82 million years. A competing explanation holds that Hiʻiaka instead formed roughly 80 million years later, through rotational fissioning as Haumea's spin accelerated.