Hypothetical black hole question

In article , Tegrof wrote:
a primordial black hole of aprox. 1 solar mass has only a 2 to 3 km
Schwarzschild radius. If it is light months away the lensing effect
would be over a very tiny solid angle. I suspect it would not be
detected over 300 years of observation.

Hmm, for comparison, Charon (1200km diameter) has had at least
one occultation in it's 28-year observed lifetime at a range of about 4
light hours. For solar-mass black hole a couple of light months away
.... I wouldn't discount the possibility of spotting the Einstein Ring
(is that a Niven-ism?). But for sure we'd have seen the gravitational
effects long since.

--
Aidan Karley,
Aberdeen, Scotland,
Location: +57d10' , -02d09' (sub-tropical Aberdeen), 0.021233
Written at Fri, 31 Mar 2006 10:48 +0100

jlb wrote:
I think our planetary orbits would display artifacts of such a mass
near our solar system - making it pretty easy to detect.

This looks right to me, depending on the distance. Interplanetary
spacecraft would be even better because they are tracked by round-trip
light time. One solar mass at 10000 AU would produce an extra
acceleration of 6E-3 m s^-2 (if I've calculated right). Of course it's
only the _tidal_ acceleration that could be detected, so divide by a
factor of order 10^4. That is still three orders of magnitude bigger
than the anomalous "Pioneer acceleration," so I'd expect it to be
detectable. If the mass is near the ecliptic plane, quite a few
interplanetary spacecraft (most notably the Pioneers) should show it.
If far from the plane, Ulysses might be the best one.

Hawking radiation is hopeless, as someone else pointed out, and we
would have to be awfully lucky to see a lensing event.

In summary:

Eliminate Hawking radiation, 1 solar mass is too big.

In the region 10,000 AU to the beginning of the so-called ort cloud
63,000 AU. It would be detectable and maybe inadvertently discovered
already by gravitational effects within our solar system. Less likely,
but maybe possible, is detection by occultation, an Einstein ring of a
star directly behind would only be between .2 and .3 seconds of arc and
very dim.

Detection much beyond 1 LY (63,000 AU) seems unlikely. Solid angle for
any occultation is too small and at 1 LY the gravitational effect is
only about 1 order of magnitude higher than Centauri system.

In article , Steve Willner
wrote:
If the mass is near the ecliptic plane, quite a few
interplanetary spacecraft (most notably the Pioneers) should show it.
If far from the plane, Ulysses might be the best one.

IF the mass is near the ecliptic.
Are there any statistics that would give the likelihood of
orbiting bodies having the same plane of rotation as their orbit. From
developmental considerations, one would *expect* the net angular
momentum vectors for the individual bodies and the system as a whole to
be more-or-less coincident, but has this actually been demonstrated?

--
Aidan Karley,
Aberdeen, Scotland,
Location: +57d10' , -02d09' (sub-tropical Aberdeen), 0.021233
Written at Tue, 04 Apr 2006 12:13 +0100

Maybe I'm not calculating right but I'm getting a much smaller value, 1
solar mass at 10,000 AU, I get ~ 6E-11 m/s^2.

1 solar mass ~ 2E30 kg
10,000 AU ^2 ~ 2E30 m^2

Conveinently left with ~ numeric value of G: 6E-11 with units m/s^2

Tegrof wrote:
Maybe I'm not calculating right but I'm getting a much smaller value, 1
solar mass at 10,000 AU, I get ~ 6E-11 m/s^2.

Looks right to me! Don't know what I did wrong earlier. And the
_tidal_ acceleration is another 3-4 orders of magnitude smaller,
depending on which planet or spacecraft one is talking about. Looks as
though 1 solar mass at 1000 AU should be detectable but not much
farther.

In message , Charles Francis
writes
Thus spake Tegrof
Could a primordial black hole of around a solar mass exist undetected
near our solar system. By near I mean somewhere between ort cloud and
nearest star--light months.

Essentially yes. It would only be detectable by the deflection of light
from objects behind it. Not easy to find.

I wonder. How often would Oort cloud objects collide with it? (if they
exist)
The impact of even a small object would make a nice explosion.
--
Mail to jsilverlight AT merseia DOT fsnet DOT co DOT uk is more likely to be
seen!

Would it? I tiny mass like a comet colliding with a 1 solar mass
black hole, I would guess it would be absorbed without any expression.
Shoemaker-Levy only made a few large holes in the atmosphere of Jupiter
...