A Buchdahl star is a highly compact star for which the boundary radius [Formula: see text] obeys [Formula: see text], where [Formula: see text] is the gravitational radius of the star itself. A quasiblack hole is a maximum compact star, or more generically a maximum compact object, for which the boundary radius [Formula: see text] obeys [Formula: see text]. Quasiblack holes are objects on the verge of becoming black holes. Continued gravitational collapse ends in black holes and has to be handled with the Oppenheimer–Snyder formalism. Quasistatic contraction ends in a quasiblack hole and should be treated with appropriate techniques. Quasiblack holes, not black holes, are the real descendants of Mitchell and Laplace dark stars. Quasiblack holes have many interesting properties. We develop the concept of a quasiblack hole, give several examples of such an object, define what it is, draw its Carter–Penrose diagram, study its pressure properties, obtain its mass formula, derive the entropy of a nonextremal quasiblack hole and through an extremal quasiblack hole give a solution to the puzzling entropy of extremal black holes.

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广义相对论中的致密物体：从布赫达尔星到准黑洞

布赫达尔星是一颗高度致密的恒星，其边界半径 [公式：见正文] 服从 [公式：见正文]，其中 [公式：见正文] 是恒星本身的引力半径。准黑洞是最大致密恒星，或者更通俗地说是最大致密天体，其边界半径 [公式：见正文] 服从 [公式：见正文]。准黑洞是即将变成黑洞的物体。持续的引力坍缩在黑洞中结束，必须用奥本海默-斯奈德形式主义来处理。准静态收缩以准黑洞结束，应使用适当的技术进行处理。准黑洞，不是黑洞，是米切尔和拉普拉斯暗星的真正后代。准黑洞有许多有趣的特性。我们提出了准黑洞的概念，