|
|
The Question
(Submitted April 17, 1997)
Which scientists are currently on the forefront of Milky Way study and theories?
Where can I find their work?
The Answer
Boy. That is a very BIG question, because there is a tremendous
amount of research involving the Milky Way galaxy, and it involves almost
every aspect of theoretical and observational astronomy. Computational
astrophysicists study how and why spiral structure forms and endures, and
the dynamics of the globular clusters that surround the disk of the Milky
Way in a halo. Observers study star forming regions, map spiral arms,
measure abundances of elements in the interstellar medium, search for
dark matter, etc. So, I'm just going to pick my favorite at the moment,
which is the search for MAssive Compact Halo Objects (MACHOS), one possible
explanation for the dark matter that must exist in galaxies, including
the Milky Way. Basically, according to
careful observations, we know that up to 90% of the matter in galaxies
must be in the form of "dark matter" to account for the dynamics we
observe. On top of that, the dark matter appears to be distributed
in a spherical halo around the Milky Way, while the luminous matter is
located largely in the flat disk.
The basic idea behind the MACHO project is something called
"microlensing:" if a MACHO were to pass between us and a distant star,
the light would be bent around the MACHO by it's gravitational field
passing almost directly in front of the star (in other words, it would act
as a gravitational lens). The light curve that results would be independent
of the wavelength of the radiation (as opposed to many intrinsic brightness
changes), would not change the polarization, would be symmetric, and would
have a very distinctive shape. In searching for such microlensing events,
the MACHO project is taking long baseline, large field photometric data,
and analyzing each star. An early conclusion of the project was that up
to 50% of the dark matter in the Milky Way may be MACHOS in the halo with
masses ranging from the mass of Jupiter to one tenth the mass of the Sun.
An added benefit the large collection of data
on variable stars in the Large Magellanic Cloud (one target). For updates
on the project, and to learn about the science team, check out:
http://www.macho.mcmaster.ca/
As I said, there are many branches of study of the Milky Way. If
your interest is different, I suggest reading the material in our learning
centerhttp://imagine.gsfc.nasa.gov/
that relates to your interest. We
also include links to other learning centers and information sources.
Regards,
Padi Boyd,
for the "Ask an Astrophysicist" Team
|
