• For full details of graphics available/in preparation, see Menu -> Planners
 Mysterious dark matter detected infographic
Picture shows fiery lobes from a dying Sun-like star, the so-called “ant nebula” (Menzel 3, or Mz3), caught by the Hubble space telescope. Is this a white dwarf in the making?
GN12236EN
EN

SPACE

Mysterious dark matter detected

March 22, 2001 - Astronomers in the U.S. and Britain, writing in the journal Science, have detected "dark matter" for the first time. The discovery suggests that burnt-out white dwarf stars may account for up to half of the mysterious dark matter that holds the universe together.

When you look at a starry sky, what you see is only 5 percent of the Milky Way’s matter. Scientists said on Thursday they have found a bit of the other 95 percent in the form of white dwarfs or burned-out stars.

Astrophysicists have been struggling for 70 years to explain this unseen matter -- known as “dark matter” -- that makes up the missing mass of the universe. They proposed exotic creatures such as “wimps” (weakly-interacting massive particles), bizarre phenomena called “cosmic strings” and “machoes,” or massive compact halo objects.

Now, a detailed analysis of images of a selected region of the southern sky has revealed 38 previously unseen white-dwarf stars, believed to be part of an extensive halo of old stellar objects enveloping our Milky Way galaxy.

White dwarfs are only about the size of the Earth and are therefore not easy to detect. But these cosmic cinders can weigh half as much as the Sun -- a teaspoonful of white dwarf matter would outweigh an elephant on Earth. Nine out of 10 stars will end up as white dwarfs. According to research published in the current edition of the journal Science, these could provide some of the gravitational glue that holds the galaxies together.

What the new discovery now suggests is that these old, burnt-out stars may actually account for up to half of this exotic dark matter.

“Dark matter is probably the largest constituent of the universe and we are seeing it for the first time,” said researcher Ben Oppenheimer of the University of California-Berkeley. “Simply knowing our place in the universe and understanding the structure of the universe is an important issue. Our relation to the universe certainly depends on what’s in it.”

To directly detect these dim white dwarfs, Oppenheimer and his fellow researchers scoured 30-year-old photographic plates of regions of the southern sky that had recently been digitized at the Royal Observatory, Edinburgh, UK. Searching through about 10% of the data, the team found 92 suspicious objects.

Follow-up observations from the Cerro Tololo Observatory in Chile revealed that 38 of these targets were previously unseen white-dwarf stars within 450 light-years of Earth.

The oldest of the white dwarfs may be as old as the galaxy -- between 10 billion to 13 billion years old -- created only a few billion years after the theoretical Big Bang.b

Sources
PUBLISHED: 23/3/2001; STORY: Graphic News; PICTURES: NASA/ESA, Science, Reuters
Advertisement