News: NASA’s Voyager 2 is Nearing Interstellar Space
On October 5, 2018, NASA announced that the Voyager 2 spacecraft, launched in 1997, has detected an increase in cosmic rays originating from outside of our solar system.
Cosmic rays:
despite their name, cosmic rays are not electromagnetic waves like radio waves, X-rays, visible light and Gamma rays. They are actual physical particles, which are moving very close to the speed of light.
Although most (about 90%) of cosmic rays are solitary protons (a hydrogen atom stripped of its orbiting electron), they can also be solitary electrons unbound to a nucleus, helium nuclei (2 protons and 2 neutrons bound together), or the nuclei of other heavier elements. A very, very small number of cosmic rays are speculated to be anti-particles, and this is an active area of research, though we have yet to observe any from orbiting telescopes.
Some cosmic rays are created by our sun through particle events and coronal mass ejections (a giant cloud of solar plasma drenched with magnetic field lines that is blown away from the Sun often during strong, long-duration solar flares and filament eruptions) On Earth, cosmic rays are also created on a small scale through lighting. The bulk of very high energy cosmic rays, however, come from elsewhere in the galaxy and universe, by the way of supernova explosions, and active galactic nuclei (from the incredible energies caused by friction, of accretion disks of matter orbiting and falling into the super-massive black holes in their centers of some galaxies).
The magnetic field around our solar system created by our sun protects us from most of the galactic cosmic rays, and the magnetosphere of the Earth caused by our planet’s metal core spinning inside the molten core deflects most of the remaining charged particles from reaching us on the surface of the Earth.
If a particular cosmic ray particle heads directly for us, as opposed to a glancing blow, or if it is a particularly powerful one (is larger, and hence more massive, or is travelling faster), it can overcome the defenses of our Sun and our planet, and impact the Earth. They are difficult to detect directly, but given how intensely powerful they are, we spot the secondary evidence of gamma rays, by measuring cascading showers of shattered atoms they cause when they enter our atmosphere and interact with air and moisture particles.
Gamma rays are harmful to humans by literally smacking the atoms which make up our DNA out of our cells. Life could likely not exist on the Earth if we were not protected by our magnetic fields. Gamma ray exposure leading to cancer remains one of the technical issues we still need to conquer to mount long-term exploration of Mars, the rest of our solar system and the stars.
Since late August of this year, two instruments on board Voyager 2 — the Cosmic Ray Subsystem, and the Low-Energy Charged Particle instruments — have detected a 5% increase in extra-solar cosmic rays.
Although this may be an anomaly, Voyager 1 went through this same increase 6 years ago as it passed through the heliosheath — the outermost layer of protection of our sun’s magnetosphere, and into interstellar space.
Voyager 2 is now 17.7 billion kilometers (118 AU) from the Sun, or, nearly 4 times the distance of the Sun to our further planet Neptune, and is travelling away from solar system at nearly 54,000 km/hr. Voyager 1 few out of the heliosheath, past the heliopause edge of our solar system and into interstellar space on Aug 25, 2012 when it was 18 billion km from the sun.
Although the progress of the Voyagers into interstellar space appears to be similar, if the measured rise in galactic cosmic rays for Voyager 2 is an indication that it is passing through the edge of the heliosheath, they went in different directions, so they will not necessarily pass through at the same distances. Voyager 1 travelling off above the plane of our solar system quite dramatically:
The correct trajectories are shown here, but their distances from the sun are not accurate.
Termination Shock:
The termination shock is the boundary marking one of the outer limits of the Sun’s influence, and is one boundary of the Solar System. It is where the bubble of solar wind. particles slows down so that the particles are traveling slower than the speed of sound.
Heliosheath:
The heliosheath is the region of the heliosphere beyond the termination shock. Here the wind is slowed, compressed and made turbulent by its interaction with the interstellar medium. Its distance from the Sun is approximately 80 to 100 astronomical units (AU) at its closest point.
Heliosphere:
The heliosphere. “Helio-” means having to do with the Sun… The heliosphere is the immense magnetic bubble containing our solar system, solar wind, and the entire solar magnetic field.
Heliopause:
The heliopause is about 123 astronomical units (AU; 18 billion km [11 billion miles]) from the Sun. The shape of the heliopause fluctuates and is influenced by a wind of interstellar gas caused by the Sun’s motion through space.
Bow Shock:
Bow shocks form the boundary between a magnetosphere (in this case heliosphere) and an ambient (or at least surrounding) magnetized medium. This occurs when the magnetic field of an astrophysical object interacts with the nearby flowing ambient plasma. For example, when the solar wind, flowing with a relative speed of order 400 km/s, encounters the magnetic field of Earth, a bow shape boundary forms. For Earth and other magnetized planets, it is the boundary at which the speed of the stellar wind abruptly drops as a result of its approach to the magnetopause (in this case heliopause). For stars, this boundary is typically the edge of the astrosphere (in the case of our sun, Helios in Greek, the heliosphere), where the stellar wind meets the interstellar medium.
The coming months will give us more evidence as to whether Voyager 2 has joined its slightly younger sibling, and is officially the 2nd man-made object to escape the radiation envelope of our solar system, and has entered interstellar space.
Below is an animation showing the trajectory of the Voyager spacecrafts away from our home planet, and star:
A infographic-video summary of this story can be seen here:
Originally published at news4starstuffs.com on October 6, 2018.
