Black Hole Sans Donut Puzzles Astronomers

Anonymous Squonk writes: "This time, a telescope made news by not finding something. According to this Honolulu Star-Bulletin article, a black hole was found that did not contain the expected 'donut' of warm matter swirling around it. This discovery (or lack of discovery) may lead scientists to rethink what they know about the core of active galaxies."

Comments

Not necessarily

[Apotsy]

A black hole without the "doughnut" of hot matter is not in conflict with current theory, if it is massive enough. Read Kip Thorne's "Black Holes and Time Warps" and notice the description near the beginning of a hypothetical massive black hole called "Gargantua". It is so massive that its event horizon is far enough away from the center so that the tidal forces are not enough to produce the large, flattened disk of hot spiraling matter.

The article doesn't say, but perhaps the reason they are puzzled is because this black hole is thought to be far less massive than Thorne's hypothetical "Gargantua". Nonetheless, the lack of a so-called "doughnut" is not necessarily in conflict with current theory.

Gemini's website

[thesolo]

Is actually here: http://astra.hi.gemini.edu/gallery/science/m87/

Re:The diameter and mass figures seem screwy

[Anonymous Coward]

According to the Schwarzschild formula (Rs = 2GM/c^2), the radius of a black hole is about 3 kilometers per solar mass. So a 3 billion solar-mass black hole would have a radius of about 9 billion kilometers. That's about 50% larger than the radius of Pluto's orbit, hence the "approximately" in your quoted statement.

What you're neglecting is the fact that a black hole is not necessarily more dense than a star. In fact, a sufficiently large black hole is less dense! For instance, a black hole of ~100 million solar masses only has an average density near that of water. It's not just how dense it is, it's how much of it you've got. Take a bucket of water, and it won't form a black hole. Take 100 million solar masses worth of buckets of water all next to each other, and they will

(I got the last example from this nice page discussing black hole myths at the bottom.)