Lorelai Gilmore's father is named Emily.
A pre-main-sequence star -LRB- also known as a PMS star and PMS object -RRB- is a star in the stage when it has not yet reached the main sequence .. star. star. main sequence. main sequence. main-sequence. Main sequence. Earlier in its life , the object is a protostar that grows by acquiring mass from its surrounding envelope of interstellar dust and gas .. protostar. protostar. After the protostar blows away this envelope , it is optically visible , and appears on the stellar birthline in the Hertzsprung-Russell diagram .. protostar. protostar. stellar birthline. stellar birthline. Hertzsprung-Russell diagram. Hertzsprung–Russell diagram. At this point , the star has acquired nearly all of its mass but has not yet started hydrogen burning -LRB- i.e. nuclear fusion of hydrogen -RRB- .. star. star. hydrogen burning. Proton-proton chain reaction. nuclear fusion. nuclear fusion. The star then contracts , its internal temperature rising until it begins hydrogen burning on the zero age main sequence .. star. star. main sequence. main sequence. hydrogen burning. Proton-proton chain reaction. zero age main sequence. zero age main sequence. This period of contraction is the pre-main sequence stage .. main sequence. main sequence. An observed PMS object can either be a T Tauri star , if it has fewer than 2 solar masses , or else a Herbig Ae / Be star , if it has 2 to 8 .. star. star. T Tauri star. T Tauri star. Herbig Ae / Be star. Herbig Ae / Be star. Yet more massive stars have no pre-main-sequence stage because they contract too quickly as protostars .. main-sequence. Main sequence. By the time they become visible , the hydrogen in their centers is already fusing and they are main-sequence objects .. main-sequence. Main sequence. The energy source of PMS objects is gravitational contraction , as opposed to hydrogen burning in main-sequence stars .. hydrogen burning. Proton-proton chain reaction. main-sequence. Main sequence. gravitational contraction. Kelvin-Helmholtz mechanism. In the Hertzsprung -- Russell diagram , pre-main-sequence stars with more than 0.5 first move vertically downward along Hayashi tracks , then leftward and horizontally along Henyey tracks , until they finally halt at the main sequence .. main sequence. main sequence. main-sequence. Main sequence. Pre-main-sequence stars with less than 0.5 contract vertically along the Hayashi track for their entire evolution .. main-sequence. Main sequence. Hayashi track. Hayashi track. PMS stars can be differentiated empirically from main-sequence stars by using stellar spectra to measure their surface gravity .. main-sequence. Main sequence. A PMS object has a larger radius than a main-sequence star with the same stellar mass and thus has a lower surface gravity .. star. star. main-sequence. Main sequence. stellar mass. stellar mass. Although they are optically visible , PMS objects are rare relative to those on the main sequence , because their contraction lasts for only 1 percent of the time required for hydrogen fusion .. main sequence. main sequence. hydrogen fusion. hydrogen fusion. During the early portion of the PMS stage , most stars have circumstellar disks , which are the sites of planet formation .. planet formation. planet formation