You must be knowing about blackholes but i will tell you about WHITEHOLES

 A white hole , in general relativity, is a hypothetical region of spacetime which cannot be entered from the outside, but from which matter and light have the ability to escape. In this sense it is the reverse of a blackhole , which can be entered from the outside, but from which nothing, including light, has the ability to escape
 Like black holes, white holes have properties like mass , charge , and angular momentum . They attract matter like any other mass,but objects falling towards a white hole would never actually reach the white hole's event horizon
 the white hole event horizon in the past becomes a black hole event horizon in the future, so any object falling towards it will eventually reach the black hole horizon..

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