an inventory of the universe's mass & energy
updated 10/12/2008


type of
matter
or
energy
W, amount
(relative to that needed for flat geometry)


how we know
the amount


what it is
(or might be)


evidence for
what it is


where it is

Cosmic Microwave
Background photons
(CMB)


0.0001


direct measurement

photons left over
from the Big Bang
(there are 109 photons for every baryon)

discovered by
Penzias & Wilson
(Nobel Prize 1978)
COBE
WMAP
(Nobel Prize 2006)


everywhere

baryonic
bright matter
(stars, planets, people...)

the insignificant portion of the universe studied
by chemists & biologists





0.005



see it; count it by assigning a mass to a given luminosity



mostly stars,
but also interstellar medium,
planets, etc.



we see the light
it emits




concentrated in the disks of spiral galaxies;
toward centers of elliptical galaxies



baryonic 
dark matter

(baryonic = neutrons & protons
or matter like us)




.044

(+ 0.004)



Big Bang production of the light elements
D, He, Li
(1998)




1) MACHOs
(brown dwarfs, faint white dwarfs, neutron stars, black holes, planets)

  2) hot gas between galaxies
(mostly H II)


1) gravitational microlensing
(1995- )

2) absorption in the spectra of distant quasars

(May 2000)

x-ray emission from clusters of galaxies

1) haloes
of galaxies


2) within/betwen clusters of galaxies






non-baryonic 

dark matter







0.23

(+ .02)



a) rotation curves of
spiral galaxies: 

Vrot  remains constant
up to the visible edge of a galaxy
(1960s)


 
b) gravitational
macrolensing

(1995 -  )

gravitational lens
picture gallery


dark matter ring
discovered in early 2007 Hubble animation


c) degree of large-scale clustering of galaxies
(2000 - )

d) separation of light and dark matter during galactic collisions
(2006 - 2008)

(1)
bullet cluster from
APOD 8/24/06

bullet-cluster
animation/video
from Chandra 2006...
original article

(2) MACS cluster clash found by Chandra in mid-2008


particles with
existence evidence:
1) neutrinos



particles without
existence evidence: 

2) axions ??

3) neutralinos??

how we are looking:

the Search for Dark Matter
is a fairly old article, but the theory is still correct although the experiments have become much more sensitive (yet without detecting anything).... the first few pages should be easy to read...

 but then the article

becomes intense and not appropriate for small children as it discusses the experimental search techniques


Universe Reveals
its Dark Side










1) at least   some neutrinos (2?) have mass, but we can only measure mass differences between neutrino species

(Nobel Prize 2002)


2) discovered -- or maybe not ?

(Feb 2000)










haloes 

of galaxies




dark energy



0.73

(+ .04)


1) distant supernovae
are fainter than expected
(1999 - )

2) flat geometry of the universe requires something else besides matter


1) Einstein's
cosmological constant
??

2) quantum vacuum energy??


3) quintessence ??

4) novel behavior of matter??




none




everywhere

(total)

1.01 

(+ .02)

spatial anisotropies
in the CBR
(2000 - )