NASA Finds Direct Proof of Dark Matter

[CharlestonChad]

Erica Hupp
Headquarters, Washington
202-358-1237

Steve Roy
Marshall Space Flight Center, Huntsville, Ala.
256-544-6535

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998


Aug. 21, 2006
RELEASE: 06-297


NASA Finds Direct Proof of Dark Matter

Dark matter and normal matter have been wrenched apart by the tremendous collision of two large clusters of galaxies. The discovery, using NASA's Chandra X-ray Observatory and other telescopes, gives direct evidence for the existence of dark matter.

"This is the most energetic cosmic event, besides the Big Bang, which we know about," said team member Maxim Markevitch of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

These observations provide the strongest evidence yet that most of the matter in the universe is dark. Despite considerable evidence for dark matter, some scientists have proposed alternative theories for gravity where it is stronger on intergalactic scales than predicted by Newton and Einstein, removing the need for dark matter. However, such theories cannot explain the observed effects of this collision.

"A universe that's dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking," said Doug Clowe of the University of Arizona at Tucson, and leader of the study. "These results are direct proof that dark matter exists."

In galaxy clusters, the normal matter, like the atoms that make up the stars, planets, and everything on Earth, is primarily in the form of hot gas and stars. The mass of the hot gas between the galaxies is far greater than the mass of the stars in all of the galaxies. This normal matter is bound in the cluster by the gravity of an even greater mass of dark matter. Without dark matter, which is invisible and can only be detected through its gravity, the fast-moving galaxies and the hot gas would quickly fly apart.

The team was granted more than 100 hours on the Chandra telescope to observe the galaxy cluster 1E0657-56. The cluster is also known as the bullet cluster, because it contains a spectacular bullet-shaped cloud of hundred-million-degree gas. The X-ray image shows the bullet shape is due to a wind produced by the high-speed collision of a smaller cluster with a larger one.

In addition to the Chandra observation, the Hubble Space Telescope, the European Southern Observatory's Very Large Telescope and the Magellan optical telescopes were used to determine the location of the mass in the clusters. This was done by measuring the effect of gravitational lensing, where gravity from the clusters distorts light from background galaxies as predicted by Einstein's theory of general relativity.

The hot gas in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity. This produced the separation of the dark and normal matter seen in the data. If hot gas was the most massive component in the clusters, as proposed by alternative gravity theories, such a separation would not have been seen. Instead, dark matter is required.

"This is the type of result that future theories will have to take into account," said Sean Carroll, a cosmologist at the University of Chicago, who was not involved with the study. "As we move forward to understand the true nature of dark matter, this new result will be impossible to ignore."

This result also gives scientists more confidence that the Newtonian gravity familiar on Earth and in the solar system also works on the huge scales of galaxy clusters.

"We've closed this loophole about gravity, and we've come closer than ever to seeing this invisible matter," Clowe said.

These results are being published in an upcoming issue of The Astrophysical Journal Letters. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center, Cambridge, Mass. For additional information and images, visit:

http://www.nasa.gov/home/hqnews/2006/aug/HQ_06297_CHANDRA_Dark_Matter.html

 

[Bullypulpit]

Here is an optical image of the event from the Chandra X-ray observatory site:

<center><img src=http://chandra.harvard.edu/photo/2006/1e0657/1e0657.jpg></center>

Here is a link to the site:

<center><a href=http://chandra.harvard.edu/photo/slideshow/>X-RAY Highlights of CHANDRA</a>

 

[waltky]

possum thinks it's a spidey web from a space spidey...

Earth may be growing dark matter 'hairs'
Nov. 24, 2015 - "If we could pinpoint the location of the root of these hairs, we could potentially send a probe there and get a bonanza of data about dark matter," astrophysicist Gary Prézeau said.

Apparently, dark matter comes in hair form, and astronomers looking to find the mysterious strands may not have to peer all that far into space. According to new study by scientists at NASA, planet Earth may be sprouting dark matter hairs in all directions. Only about five percent of the universe is made up of ordinary or visible matter. The rest is dark energy and dark matter, of which we have no direct evidence. Astronomers can only infer the presence of dark energy and matter.

An illustration shows what dark matter hairs around Earth might look like.​

Astrophysicists have indeed done a lot of inferring over the years. In the 1990s, models suggested dark matter would band into long thread-like streams as it moved through space, interacting with ordinary matter. Now, scientists at NASA's Jet Propulsion Laboratory propose the existence of such streams in and around Earth. "When gravity interacts with the cold dark matter gas during galaxy formation, all particles within a stream continue traveling at the same velocity," Gary Prézeau, describing the formation of dark matter streams, said in a press release. Prézeau built a model to describe how these streams would behave as they approach and pass through Earth. The results suggest the streams would be bent and pulled into long, thin hairs, sprouting in all directions.

http://cdnph.upi.com/sv/b/i/UPI-654...34/Earth-may-be-growing-dark-matter-hairs.jpg[/img]
An illustration shows what dark matter hairs around Earth might look like.​

According to Prézeau, these hairs would be thickest at their roots and thinner at the tips. "If we could pinpoint the location of the root of these hairs, we could potentially send a probe there and get a bonanza of data about dark matter," Prézeau said. "Dark matter has eluded all attempts at direct detection for over 30 years. The roots of dark matter hairs would be an attractive place to look, given how dense they are thought to be," added Charles Lawrence, chief scientist for JPL's astronomy, physics and technology directorate. The new research was published this week in the Astrophysical Journal.

Earth may be growing dark matter 'hairs'

See also:

Research reveals how hypergiant star quickly sheds mass
Nov. 25, 2015 - "Massive stars live short lives," study author Peter Scicluna said.

VY Canis Majoris is one of the largest stars in the Milky Way, but it won't be for long. The stellar behemoth, a red hypergiant located 3,900 light-years from Earth, is quickly shedding mass, and now new observations are helping astronomers better understand how and why. VY Canis Majoris is dying. As it does so, it is constantly losing large amounts of dust and gas as it expands and expels mass. Eventually, the hypergiant will explode in a violent supernova, collapsing on itself and destroying much of the surrounding cloud of stellar material. The rest is sent out to into interstellar space where it will go on to form new stars and planets.

http://cdnph.upi.com/sv/b/i/UPI-2671448478276/2015/1/14484799528692/Research-reveals-how-hypergiant-star-quickly-sheds-mass.jpg
An image of the hypergiant. The star itself is obscured by the giant cloud of expelled stellar gas and dust. Portions of the VLT's SHERE instrument obscure the frame.[/CENTER]

Astronomers' latest observations confirm the role radiation pressure plays in pushing out the star's gas and dust into the surrounding cloud as it expands. Scientists have long assumed radiation pressure to be responsible for mass expulsion, but being a relatively weak force, scientists estimated expelled stellar particles would need to be rather large to be affected. The latest observations, made using the SPHERE instrument on the European Southern Observatory's Very Large Telescope, prove scientists estimated correctly -- the gas and dust particles expelled by the hypergiant are 0.5 micrometers across, 50 times bigger than most interstellar particles. The findings were shared in a new paper, published in the journal Astronomy & Astrophysics.

Currently, VY Canis Majoris is 30 to 40 times more massive than the sun and 300,000 times as luminous, but its impressive size won't last. "Massive stars live short lives," lead study author Peter Scicluna, an astronomer with the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan, said in a press release. "When they near their final days, they lose a lot of mass. In the past, we could only theorize about how this happened." "But now, with the new SPHERE data, we have found large grains of dust around this hypergiant," Scicluna added. "These are big enough to be pushed away by the star's intense radiation pressure, which explains the star's rapid mass loss."

[URL='http://www.upi.com/Science_News/2015/11/25/Research-reveals-how-hypergiant-star-quickly-sheds-mass/2671448478276/?spt=slh&or=4']Research reveals how hypergiant star quickly sheds mass[/URL][/quote]​