In general, astronomers learn about the Universe by the electromagnetic radiation (or light) that we see from it.
The light we see is in the form of radio waves, infrared, optical, ultraviolet, X-ray, and gamma-ray emission.
But what if there is material in the Universe that does not glow? How will we ever know it is there? How can we
tell how much of it there is? How do we know what it is?
Such material is called "dark matter", and astronomers now believe that most of the material in the Universe is
made of this stuff. It is material that does not emit sufficient light for us to directly detect it, yet there
are a variety of ways that we can indirectly detect it.
The most common method involves the fact that dark matter has a gravitational pull on both the light and the
sources of light that we can see. From the effects of "extra" gravity that we detect, we infer how much mass must be present.
The Coma Cluster of galaxies
The image above shows one way this is done. Pictured here are two superimposed images of the Coma Cluster of galaxies.
The red areas are X-ray light seen by the Einstein satellite; the blue is visible light from a Palomar Sky Survey optical
image (made with ground-based telescopes at Caltech).
Scientists have used these observations and others to determine the amount of gravity required to hold together all the mass detected in the image. Surprisingly,
there is not nearly enough mass observed to explain the inferred gravity - somehow, there is undetected "missing mass." What could this "missing mass" be?
The kinds of materials that we experience every day are made of atoms, which are composed of protons, neutrons, and electrons.
We refer to this type of matter as "baryonic".
Is the dark matter in the Universe made of the same stuff that we are familiar with, i.e., is it baryonic?
Or is it something strange ... some kind of exotic new material, which we could call non-baryonic?
So far, it looks like there are both baryonic and non-baryonic types of dark matter. Some dark matter may be composed of regular matter (ie., baryonic), but simply not give off much light. Things like brown dwarf stars would be in this catagory.
Other non-baryonic dark matter may be tiny, sub-atomic particles which aren't a part of "normal" matter at all.
Dark Matter Movie from the Bolshoi Simulation
Video Credit: A. Klypin (NMSU), J. Primack (UCSC) et al., Chris Henze (NASA Ames), NASA's Pleiades Supercomputer
If these tiny particles have mass and are numerous, they could make up a large part of the dark matter we think exists.
If true, then it's possible that most of the matter in the Universe is of some mysterious form that we cannot yet even identify!
Super-Earth Discovered Orbiting Several Suns
Scientists at the University of Goettingen and the Carnegie Institution for Science in the U.S. Washington have discovered a potentially habitable planet,
located 22 light years away from Earth.
The super-Earth, named GJ 667Cc has the mass four and a half times that of our Earth and an orbit of 28.15 days.
The planet GJ 667Cc orbits a dwarf star of the class M, 22 light years away which corresponds to approximately 209 trillion kilometers.
Astrophysicist Resolves Paradox With Radio Millisecond Pulsars
Celestial objects known as pulsars are still full of secrets. It is takes time and many efforts to learn all their secrets. Previous studies reached
the paradoxical conclusion that some millisecond pulsars are even older than the universe itself. It was time to resolve this paradox.
Cosmic Vibrations From Neutron Stars
In the collision of neutron stars, the extremely compact remnants of evolved and collapsed stars, two light stars merge to one massive star.
The newly-born heavyweight vibrates, sending out characteristic waves in space-time. Model calculations at the Max Planck Institute for
Astrophysics now show how such signals can be used to determine the size of neutron stars and how we can learn more about the interior of these exotic objects.
Unknown Force "Intelligently" Put Together Miranda Moon - with video
What could melt this moon in this extremely cold region of the solar system?
Voyager 2 passed Miranda’s strange world at a distance of only 3,000 kilometers (1,800 miles) and
sent back to Earth very detailed images of its "tortured" surface.
Nothing like them has been seen anywhere else in the solar system! Did a type III civilization conduct some "experiments" on Miranda?