The mystery of the "missing mass" of the universe, one of the most fundamental riddles of modern astronomy and physics, continues to elude scientists as the new Hubble Space Telescope images have ruled out the simplest proposed explanation of "dark matter"--the unseen material whose gravitational influence on stars and galaxies can be measured.
Hubble Strike Out
For many years, astronomers have argued that the "missing" mass is simply a great many small, faint stars that telescopes on the ground have not been able to detect.
One of the main objectives for the $1.5 billion Hubble Space Telescope was to get above the filtering atmosphere to look for "red dwarf" stars, which were viewed as the most likely explanation for the missing dark matter.
Two independent teams have now ruled out red dwarfs as an explanation for the mysterious missing mass.
The existence of dark matter was proposed in 1932 by astronomer Jan Oort, who measured the motions of nearby stars in our Milky Way relative to the galactic plane. He found that the mass of the plane must be more than the mass of the material that can be seen.
A year later, Fritz Zwicky examined the dynamics of clusters of galaxies and found their movements similarly perplexing.
Over the years, many spiral galaxies were observed and found to be swirling too fast to be held together by the gravitational pull of the visible stars. If extra mass were not there exerting a pull, some of the stars would be flung away because they were moving so fast. But they're not.
Furthermore, in 1973 Jeremiah P. Ostricker and James Peebles showed persuasively that the flattened galactic disk should have pulled apart in much less time than the accepted age of the Milky Way.
The only reasonable way to explain the stability of the galaxy was a "halo" of dark matter that extended from beyond the Sun's orbit to about the center of the Milky Way.
The Red Dwarf Hope
Theory suggested that red stars, as small as 8% of the mass of the Sun and 100 times dimmer, could make up the halo. Observations of such small, faint objects from the ground would be ineffective, so the great hope was the NASA telescope launched in 1990 and subsequently repaired.
With the new Wide Field-Planetary Camera 2, a group led by John Bahcall of the Institute of Advanced Study in Princeton, NJ and Andrew Gould of Ohio State University began a survey, looking for the red dwarfs.
They found that the Milky Way has relatively few faint red stars, accounting for only 15% of the Milky Way's mass and no more than 6% of the mass required for the dark matter halo theory.
Meanwhile a separate team, led by Francesco Paresce of the Space Telescope Science Institute in Baltimore, MD, trained the telescope on a hole through the core of a globular cluster of galaxies called NGC 6397, expecting to see "wall-to-wall" red dwarfs; relatively few were found.
Neither team found stars less than 20% of the mass of the Sun. The very small stars simply don't exist. The death of red dwarfs presents a major challenge to those who try to explain smaller, unseen stars as the answer to the "missing" matter. This situation has left astronomers embarrassed to admit that they can't find over 90% of the mass of the universe.
WIMP's and MACHO's to the Rescue?
An alternative, which also remains purely conjectural, supposes the existence of bizarre particles or objects like "weakly interacting massive particles" (wimp's) and "massive compact halo objects" (macho's).
If explanations in terms of ordinary matter composed of baryons (protons, neutrons, etc.) prove impossible, the only remaining alternatives would involve revising our understanding of the laws of physics.
Non-baryonic particles exist, but they have low mass. Massive particles that are electrically neutral (wimp's) are purely hypothetical.
The National Science Foundation has funded an effort at the University of California, Berkeley, to capture evidence of wimp's. (By one theory, 26,000 wimp's are rapidly passing through each human body at any given moment.)
It is extremely important to realize that the our entire knowledge of the physical universe is embarrassingly incomplete and based on only about 5% of the known mass. We need to maintain a deep humility as we explore the current perceptions of the universe, and as we encounter the expansive conjectures of that speculative sphere of interest known as cosmology. (There are those who enjoy drawing "vast conclusions from half-vast data!")
It is even more important to adopt a deep intellectual humility as we approach those provocative "transitions" between the physical realms and the spiritual realms revealed in the Bible.
One of the most exciting discoveries is that the Designer of the Universe Himself has given us personal insight behind the scenes. And what an adventure it is to discover Him!
The Biblical account is replete with evidences of not only "extra-physical" reality, but the Bible further emphasizes that this realm beyond our perception is the domain of major warfare-- spiritual warfare.1
It is the mission of Koinonia House to develop and distribute materials which will help you to discover this real reality and the amazing treasure we have in the Bible--the inerrant Word of God Himself!
(See also the articles on "Missing Mass" in Personal UPDATE, February 1993, pp. 5-9, and January 1994, pp. 10-14.)