fed's research homepage

i'm working on it....

for a more technical description: a gzipped powerpoint presentation,
or staroffice presentation
probability distributions for LMC lign of sight in proper motion

probability distributions for Nelson et al 2003 survey

histograms for Nelson et al 2003 survey

my old distributions jpg or png weighted for the efficiency

white dwarfs are the latest phase of stellar evolution for the vast majority of stars in the sky: they are dieing stars that will cool down and eventually just turn off. often times they sit in their own ejecta, called planetary nebulae. the most part of the star has exploded in the outer space, leaving its colorful trace and a faint star in the center.

particularly old white dwarfs would turn blue, and would be hardly visible with the most sofisticated instruments, if at all.

key 2: dark matter

around 1950, a vary famous lady of astronomy: vera rubin, was able to discover, by the way the galaxy rotates, that most of the matter in it included must had not been seen yet. in fact only 10% or less of our galaxy is visible for us.

and the rest?

it's a round halo that surrounds us.

what is it made of?

we do not know yet: it could be exotic unknown matter, of different nature then the matter that we are familiar with and we know surrounds us, of which we and the astral objects such as stars and planets are made. Or it could be just the same, but for various reasons not quite visible.

key 3: how do we see what's too dark to be seen?

two are the ways to detect an object in space: by observing its electromagnetic emission or via its gravitational interaction with other celestial bodies.

bodies that are not bright enought at any wavelenght (that is they do not emitt any detectable kind of light, whether visible frequencies, lower ones - infrared, microwaves, radio... - or higher ones - ultraviolet, X-ray, Gamma-ray...) still can interect with the objects that surround them and that sit in their gravitational field.

if the bodies are close enought, the gravitational interaction determines their motion: like the sun and the planets surrounding it, or two binary stars that would rotate around one another.

but a mass can as well interact gravitatinally with the light: in fact, in einstain relativity, gravitation is not considered a force exterted by a massive body but a deformation of the space around it. that is: around a massive body the space is bent and the path that requires the minimum energy to go from one point to another (so called geodesic: minimize the energy is the reason why the natural motion in absence of force in euclidian space - and in the space as we are used to think of it - is a straight line) is no longer a straight line, but some curve, with curvature depending on the mass and the distance form the gravitational body.

a ray of light will respond as any other massive object to this deformation of the space, and, if the source of radiation lays behind a massive body, the emitted light will travel along the bent path around the object.

... the rest of the story will be updated soon.....

this page is maintained by federica

chapter 1: the dark universe

chapter 2: light up the dark