Which Mysteries Might MACHOs and PLANCHOs Solve?

"Robert L. Oldershaw" wrote in news:mt2.0-
:

A new preprint by the MOA, uFUN, RoboNet, OGLE, ... collaborations
reports a "cold, low-mass planet of about 10 Earth masses.

http://arxiv.org/PS_cache/arxiv/pdf/...106.2160v1.pdf

# wget http://arxiv.org/PS_cache/arxiv/pdf/...106.2160v1.pdf
--2011-06-17 12:20:28--
http://arxiv.org/PS_cache/arxiv/pdf/...106.2160v1.pdf
Resolving arxiv.org... 128.84.158.119
Connecting to arxiv.org|128.84.158.119|:80... connected.
HTTP request sent, awaiting response... 403 Forbidden
2011-06-17 12:20:28 ERROR 403: Forbidden.

Better link:

http://arxiv.org/abs/1106.2160

Direct linking makes arXiv cry.

Ok, another planet observed via gravitational microlensing.

http://exoplanet.eu/catalog.php

As of today that makes the 13th discovered via microlensing, going back
to 2004. So this isn't exactly breaking news.


The relevance to the subject of this thread is the comment on page 24
that the new results support the previously reported results of Sumi
et al and also support the contention that there is a large and
previously undetected population of "failed Jupiter-cores". These
objects would have masses below the mass of Jupiter.

Far below. Ten Earth masses is ~0.01 M_jupiter. The results of Sumi, et.
al. report a population of ~10 Jupiter mass planets.

Neither population accounts for dark matter.


The race is on to discover the mass spectrum and distribution of
planets and unbound planetary-mass objects (UPMOs) using microlensing
techniques in addition to more conventional methods.

562 exoplanets isn't enough?


We seem to be entering a remarkable scientific period wherein many
previous assumptions in atomic, stellar and galactic physics can
finally be checked empirically.

For what value of 'finally'? Your theory has been excluded by the
various microlensing collaborations.



Robert L. Oldershaw
Major Thanks and Congrats to the Boston Bruins - Fantastic Series!

In article , "Robert L.
Oldershaw" writes:

Those who are following developments in the use of microlensing
experiments to search for MACHOs and UPMOs as dark matter constituents
will certainly want to carefully read:

arXiv:1106.3875v1 [astro-ph.CO] posted to arxiv.org on 20 Jun 2011

Note: I haven't read the paper yet, but will tomorrow.

This updated paper by MRS Hawkins reassesses "The case for primordial
black holes as dark matter".

Notable points raised by the paper a

1. Quasar microlensing is explained quite well by MACHO dark matter
models.

Well, a MACHO is a MAssive Compact Halo Object. The only question is
whether the microlensing objects are in galactic halos or not.

2. The leading candidate for the MACHOs is primordial stellar-mass
black holes.

According to the paper by Hawkins (who has been sounding this horn for a
couple of decades now) or does he cite additional references for this
claim?

Given Hawkins' arguments for stellar-mass primordial MACHOs and the
apparent discovery by Sumi et al of a huge population of unbound
planetary-mass objects in the Galaxy, it seems to me that primordial
ultracompact objects deserve at least equal status with WIMPs as
candidates for the constituents of the dark matter.

Status is determined by observations, not opinion.

With the LHC and microlensing collaborations both ramping up their
research activitites, I think we have a classic scientific showdown in
the making. Are WIMPs, axions, sterile neutrinos and/or sparticles
"just around the next corner"? Or is something quite a bit more
substantial lurking throughout the cosmos?

Of course, there could be more than one type of dark matter.

Phillip Helbig---undress to reply wrote
in :

[...]

Hawkins' arguments. He has been making the same arguments for nearly 25
years, and there's a nontrivial body of work that cites him and explains
why his model is wrong. Eg, Baganoff, et. al.

I expand on this a lot more in my response to Robert, but the basic problem
is that surveys specifically meant to find these object haven't found them
and he has not managed to convincingly explain why.

With the LHC and microlensing collaborations both ramping up their
research activitites, I think we have a classic scientific showdown in
the making. Are WIMPs, axions, sterile neutrinos and/or sparticles
"just around the next corner"? Or is something quite a bit more
substantial lurking throughout the cosmos?

Of course, there could be more than one type of dark matter.


So far, there's no evidence that there are multiple dark matter species.
Some folks have suggested various things like dark-sector charges, fifth
forces, multiple uncharged species, etc.

As far as I have seen, none of it has passed serious observational muster.
Only the ones that suggest DM can decay have tangible observational support
from PAMELA/FERMI observations.

On Wed, 22 Jun 11, "Robert L. Oldershaw" wrote:
arXiv:1106.3875v1 [astro-ph.CO] posted to arxiv.org on 20 Jun 2011
This updated paper by MRS Hawkins reassesses "The case for primordial
black holes as dark matter".

To model "dark matter" as being any form of matter at all, shows a
lack of imagination, in my view. "Dark matter" is just a placeholding
term for the gap between model and observation, which in this case is
about, what, 90% of the show? I prefer additional large dimension(s)
as an explanation, but whatever it may be, it's not likely to be
anything we know as "matter". What is more likely, quadrillions of
massive black holes, or just a lousy model.

...