Re: Chandra and black hole abundance

From: Jeff Davis (
Date: Sun Jan 16 2000 - 21:20:38 MST

John K Clark writes:

>Chandra just discovered the closest known black hole to earth, it's
>1600 light years away. What would be really interesting is if it can find
>any mini black holes, those about as massive as a mountain and made in the
>first second of the Big Bang. Such a beast would be super hot but so tiny
>it would not be very bright, if one is found it would have be nearby and that
>would mean mini black holes are common.

If mini black holes were made in the big bang, and if they "evaporate"
(unless refueled!), they would have been most numerous right after the big

Then they would have floated around the universe, expanding or wasting
away, depending on the density of matter in their path. Something of a
scary image this. Interstellar/intergalactic "harvesters" sweeping up the
debris of the universe.

Though after eons, the vast majority of them may have disappeared, starved
by the ever-diminishing supply of fuel, yet in the early days they could
have been a real scourge. What happens when a mini black hole plunges into
an earth, or a jupiter, or yet more dramatically, a star? In the early
days of the universe, how very much more common an occurrance could this
have been? Could this be the explanation of the Fermi Paradox? Could this
be Robin's "Great Filter"? Would there be an x-ray afterglow of this
feeding frenzy? Some evidence coming to us from tens of billions of light
years back in time?

Could intelligent life and advanced civilizations only now have the
breathing room--the time to develop--because the rate of disruption of star
system evolution has been reduced below a certain crucial threshold? Could
gamma ray bursts, now something of a mystery, be a reminder of a
once-common cataclysm?

My peek at this situation came not from CHANDRA, but from

<The star splitter: Microlensing technique pioneered by
    NSF researchers finds black holes

EurekAlert 13 Jan 2000

< Two international teams of astronomers
    supported by the National Science Foundation (NSF) recently used
another "star splitter,"
    the technique of gravitational lensing, to examine another curiosity --
isolated black holes
    drifting among the stars in our galaxy

<In 1936 Einstein predicted what an observer would see if a
    very faint object with a strong gravitational field such as a black
hole passed in front of a
    faint star. The black hole's gravity would act like a powerful lens,
splitting the star's image
    into multiple images and making the star appear brighter.

<Already, the MACHO astronomers have noted 300
    instances of gravitational microlensing near the central regions of our
galaxy, each marking
    the passage of an unseen object in front of the star.

<Bennett and his collaborators examined two microlensing events,>

<calculations of the location and brightness of the stars and the mass of the
    objects passing in front led the teams to conclude the objects were
probably black holes
    drifting through space

Move over puny asteroid impacts! For a really bad hair day nothing matches
coming acropper of a derelict black hole.

                        Best, Jeff Davis

           "Everything's hard till you know how to do it."
                                        Ray Charles

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