The Sun
The
Sun [1] is
a giant fusion reactor busily engaged in the conversion of
hydrogen (at present approximately 70% by mass) to helium (at present
approximately 28%), a giver of life (electromagnetic radiation
translates into heat and light, both being instrumental in
photosynthesis) and the center of the Solar
System.
Its mass is approximately 99% of the Solar System's total, yet with a
diameter of 1,390,000 kilometers, a core temperature of 15,000,000
Celsius and a surface temperature of 5,500 Celsius [2] it is by
galactic standards fairly ordinary.Categorized as a Population 1 (heavy element-rich) yellow dwarf, it's at four and a half billion years old almost halfway through its main sequence. Eventually, upon exhausting its hydrogen, it will expand into a red giant enveloping the inner planets before ejecting its outer layers and forming a planetary nebula. At the center of this glowing shell of ionized gas will be a tremendously hot stellar core, a remnant which will eventually cool and become a white dwarf. Ultimately, its remaining heat having dissipated, all that will be left is a burned out ember, a black dwarf. [3]
[1] The Sun has been deified by many cultures throughout the course of human history: it was Helios the son of Hyperion and Theia to the Greeks, Sol to the Romans and Aten (or Aton) during ancient Egypt's 18th dynasty and the reign of Amenhotep IV (Akhenaten).
[2] The exception being sunspots, giant areas on the Sun's surface of reduced temperature (3,000 to 4,000 degrees Celsius). The visible manifestation of intense magnetic activity which inhibits heat transfer, they appear as dark blotches when compared to the surrounding photosphere.
[b] Our Sun’s magnetic cycle peaks every 22 years, sunspot activity every 11. Both events occurred in 2013. Coronal mass ejections (CMEs) more common during periods of increased solar activity trigger geomagnetic disturbances (GMDs) - high energy particles that can disrupt power lines. Since the 1970s the spider web of transmission lines that crisscross the industrialized world has grown enormously. NASA warns that these interconnected networks acting as antennas can be energized by solar flares that could blackout continents for months, full recovery taking years.
During
the last one and a half centuries there have been two massive CMEs. The
“Carrington Event” of 1859 caused the Northern Lights to appear as far
south as Hawaii, while a second GMD, in 1921, lit up skies in the
northern hemisphere as far south as the West Indies. Both flares caused
intermittent telegraph outages worldwide.We’ve come a long way since then, but today’s technology instead of being more resilient is much less so. Giant solar flares could easily fry the circuitry of satellites, banking machines, GPS, television, computers, radio the internet and more, and with nuclear reactors (remember Fukushima) failing along with the grid we could even revert (at lest temporarily) to a pre-electrical/electronic/industrial society. (In March of 1989 a 90 second solar blast left six million Canadians without power for nine hours, baked transformers in the United Kingdom and triggered irregularities in nuclear and non nuclear fueled facilities across the United States.)
On February 11, 2010, NASA launched a revolutionary eight hundred milion dollar spacecraft called the Solar Dynamics Observatory (SDO) into Earth orbit, where it will study our Sun from a circular geosynchronous vantage point of some 22,300 miles (36,000 km) using three very high tech instruments: the Helioseismic and Magnetic Imager (HMI), the Atmospheric Imaging Assembly (AIA) and the Extreme Ultraviolet Variability Experiment (EVE). The main goal of the mission is to get a better understanding of how the Sun works, thereby allowing more accurate forcasting of space weather and the disruptive solar storms which can pose a threat to astronauts and play havoc with satellites, communications, and electrical power grids.
In the Spring of 2011, two countries, the UK and the US announced plans to mandate “controlled power cuts” to protect the grid in the event of a massive power emergency. This islanding of the system is intended as a last resort to both limit the extent of the problem and safeguard equipment.
If the past is any indicator it’s not enough: In July of 2012 a terrifyingly close call, a solar event on the order of Carrington that missed us by a mere nine days. Should Earth have been in the line of fire the effects could have been catastrophic.
As humanity transitions from earthbound to spacefaring one thing is a given: increased knowledge is an imperative.
NASA's Parker Solar Probe began its journey sunward on August 12. 2018, carried aloft from Cape Canaveral by a Delta lV Heavy rocket, its stated mission to study our sometimes tempermental benefactor as never before.
"The only way we can do that is to finally go up and touch the Sun," said project scientist Nicola Fox. "We've looked at it, we've studied it from missions that are close in, even as close as the planet Mercury. But [its not enough] we have to go there."
Protected by a revolutionary carbon composite heat shield just 4 1/2 inches (11 centimeters) thick) the spacecraft, the size of a small car, will begin showing its stuff this fall when its first orbit brings it within 15.5 million miles (25 million kilometers) of the Sun, easily breaking the current record of 27 million miles (43 million kilometers) set by the Helios 2 spacecraft in 1976.
By the time it gets to its 24th orbit in 2025 it will be deep in the corona (the Sun's outer atmosphere, and birthplace of the solar wind) traveling at 430,000 mph (690,000 kph). The Sun's surface (photosphere) flashing by a mere 6 million kilometers (3.8 million miles) below.
How amazing is this? Fox put it this way: If the Sun and Earth were on opposite ends of a football field, Mercury would be at the Sun's 35-yard line, Helios 2 at the 29-yard line and the Parker probe at the 4-yard line.
[3] At present the universe is believed to be too young for black dwarfs to exist.