• Question: when a star blows up it becomes a black hole right? well how long does it take for black hole to disappear?

    Asked by 0mnomcookie to Evan on 19 Jun 2011.
    • Photo: Evan Keane

      Evan Keane answered on 19 Jun 2011:

      Good questions. You are kind of right. But there are 3 possibilities.

      1. Stars that are light (like the Sun) become white dwarfs when they die
      2. Stars that are heavier (like Betelgeuse) become neutron stars when they die
      3. Stars which are the heaviest (like this one http://apod.nasa.gov/apod/ap080617.html) become black holes when they die.

      Ok, so only some become black holes when the star blows up.

      Next question is how long they take to disappear. Well, black holes evaporate (they shrink) but VERY slowly. And actually they are very good at attracting other material, which makes them grow. This happens much quicker so the overall effect is that they either stay the same or grow, so they don’t really shrink and that means they never really disappear.

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