Asplenium listeri outside the Christmas Island National Park. Asplenium listeri Asplenium listeri, commonly known as the Christmas Island spleenwort, is a species of fern in the Aspleniaceae family. It is endemic to Christmas Island, an Australian territory in the north-eastern Indian Ocean. Its specific epithet honours British zoologist and plant collector Joseph Jackson Lister, who visited the island on in 1887 and was the first to collect a specimen. The spleenwort is a small, terrestrial, lithophytic fern with shortly creeping rhizomes, and with fronds up to 90 mm long held in a crown. Found only on Christmas Island, the fern is known
A-type main-sequence star also occasionally sees Delta Leonis (A4 V) listed as a standard. There are no published A6 V and A8 V standard stars. A-type stars are young (typically few hundred million years old) and many emit infrared (IR) radiation beyond what would be expected from the star alone. This IR excess is attributable to dust emission from a debris disk where planets form. Surveys indicate massive planets commonly form around A-type stars although these planets are difficult to detect using the Doppler spectroscopy method. This is because A-type stars typically rotate very quickly, which makes it difficult to measure the small