MONUMENTAL SOLAR SYSTEM CHANGES: Strange Space Winds Blows Through The Solar System; New Study Reveals That We Are Now In A Surprisingly Complex And Dynamic Part Of The Milky Way Galaxy; Interstellar Wind Stream Could Have Wide-Reaching Effects!

September 15, 2013 - SPACE - Shifting cosmic winds suggest that our solar system lives in a surprisingly complex and dynamic part of the Milky Way galaxy, a new study reports.

A view from the Earth and Sun from far above the North Pole. As an interstellar wind blows in from the
constellation Scorpio, the sun's gravity captures it and forms a tail. The slower wind (dark blue) is bent
stronger than its faster counterpa (NASA/GSFC/UNH)

Scientists examining four decades' worth of data have discovered that the interstellar gas breezing through the solar system has shifted in direction by 6 degrees, a finding that could affect how we view not only the entire galaxy but the sun itself.

"The shift in the wind is evidence that the sun lives in an evolving galactic environment," study lead author Priscilla Frisch of the University of Chicago told SPACE.com via email. 

The winds of changeCharged particles stream off the sun to form a huge invisible shellaround the solar system called the heliosphere. Outside of this shell lies the Local Interstellar Cloud (LIC), a haze of hydrogen and helium approximately 30 light-years across.

The LIC is wispy, featuring just 0.016 atoms per cubic inch on average. LIC gas tends to be blocked by the heliosphere, but a thin stream makes it past the sun's magnetic field at the rate of 0.0009 atoms per cubic inch (0.015 atoms per cubic cm), researchers said.

"Right now, the sun is moving through an interstellar cloud at a relative velocity of 52,000 miles per hour," Frisch said. "This motion allows neutral atoms from the cloud to flow through the heliosphere — the solar wind bubble — and create an interstellar 'wind.'"

In 2012, three papers citing measurements by NASA's Interstellar Boundary Explorer (IBEX) spacecraft showed that the wind has changed slightly over the past decade.

The sun is passing through a wispy cloud of interstellar gas known as the Local Interstellar Cloud. As the
sun moves through it, it sweeps up neutral interstellar helium into a cone behind it.
(NASA/Goddard/Adler/University of Chicago/Wesleyan University)

Frisch and her team were intrigued, and they began to wonder just how far back the difference extended. Studying data gathered by a number of spacecraft — IBEX, the joint European Space Agency/NASA Ulysses probe and several craft from the 1970s, including NASA's Mariner 10 and the Soviet research satellite Prognoz 6 — the team found that, over the course of 40 years, the wind had shifted by 6 degrees.

What's causing this change in direction? According to Frisch, it may be related to turbulence in the interstellar cloud around the solar system.

"Winds on Earth are turbulent, and other data show that interstellar clouds are also turbulent," she said. "We find that the 6-degree change is comparable to the turbulent velocity of the surrounding cloud on [the] outside of the heliosphere."

Wide-reaching effectsInterstellar winds stream in from the direction of the constellation Scorpius, almost perpendicular to the sun's path through the galaxy. As the winds interact with the sun, they create a distinctive feature.

"Helium is gravitationally focused to create a trail of helium known as the 'focusing cone' behind the sun as it moves through space," Frisch said.

The dense cone makes the particles easier to study as they pack in behind Earth's star.

The changing wind could have implications that go beyond understanding the region surrounding the solar system. It could also affect studies of the charged particles streaming off the sun.

"When we try to understand the past and present heliosphere, we can no longer assume that the heliosphere changes only because of the solar wind," Frisch said. "Now we have evidence that changes in the interstellar wind may be important."

The new study was published online Sept. 5 in the journal Science. - FOX News.

New Cosmic Ray Discovered

European astronomers have discovered a new source of cosmic rays emanating from the vicinity of the Arches cluster, near the center of the Milky Way. According to the researchers, these particles are accelerated in the shock wave generated by tens of thousands of young stars moving at a speed of around 700 000 km/h. What makes this discovery stand out is that their origin differs from that of the cosmic rays discovered exactly 100 years ago by Victor Hess, which originate in the explosions of supernovae. The findings were published in the journal Astronomy & Astrophysics. 

The discovery, made by researchers from the Centre national de la recherche scientifique (CNRS) and the Atomic Energy and Alternative Energies Commission (CEA), was made possible thanks to the European X-ray astronomy satellite XMM-Newton. This satellite is also unique as it is the biggest scientific satellite ever built in Europe; its telescope mirrors are among the most powerful ever developed in the world, and with its sensitive cameras it can see much more than any previous X-ray satellite. 
Cosmic rays were discovered by the Austrian physicist Victor Franz Hess 100 years ago when he noticed the existence of ionising radiation of extraterrestrial origin. When certain stars at the end of their lives explode and become supernovae, their matter is ejected at supersonic speed, generating shock waves that accelerate the particles. As a result, some atomic nuclei gain very high kinetic energy and enter the Earth’s atmosphere.

Low-energy cosmic rays – which are rays whose kinetic energy is less than half a billion electronvolts – are not easily detected in the region of our planet since the solar wind prevents them from entering our heliosphere. As a result, little is known about their chemical composition and flux outside the Solar System, although everything suggests they play a significant role in the Galaxy. For example, it has been suggested that by ionizing and heating the densest interstellar clouds they probably regulate the formation of stars. 

The astronomers began their research by studying the X-ray emission that should theoretically be generated by low-energy cosmic rays in the interstellar medium. They then looked for signs of this theoretical emission in X-ray data collected by XMM-Newton since its launch in 1999. By analysing the properties of the X-ray emission of interstellar iron recorded by the satellite, they found the signatures of a large fast ion population in the vicinity of the Arches cluster, about one hundred light years from the centre of the Milky Way. The astronomers estimate that the stars in this cluster are traveling together at a speed of approximately 700 000 km/h. The cosmic rays are in all likelihood produced in the high-speed collision of the star cluster with a gas cloud in its path. In this particular region, the energy density of the accelerated ions is around 1 000 times greater than that of cosmic rays in the neighbourhood of the Solar System. 
What makes this research stand out is that this is the first time that a major source of low-energy cosmic rays has been discovered outside the Solar System. It shows that the shock waves of supernovae are not the only objects that can cause mass acceleration of atomic nuclei in the Galaxy. As a result of these findings it should now be possible to identify new sources of ions in the interstellar medium, which may lead to a better understanding of the effects of these energetic particles on star formation.

Contacts and sources:

CORDIS

Astronomy & Astrophysics
http://www.aanda.org/ 
CNRS
http://www.cnrs.fr/