Just four days ago, we dodged a bullet ... figuratively. An asteroid named 2012 DA14 passed by the Earth at a distance of about 17,000 miles and traveling at 4.8 miles per second. That's over 10 times the speed of a bullet. Placing it inside the orbits of geosynchronous satellites, it was the closest approach to Earth by an object of that size which we have been able to track as it approached. A recently discovered asteroid (in 2012), it spans a width of about 160 feet. What could it do to us if it were to strike the Earth? Similar sized objects have targeted Earth in the past. The Tunguska blast of 1908 which leveled 200 square miles of forest in the remote Tunguska region of Siberia and Barringer Meteor Crater in Arizona, produced by an impact 50,000 years ago, were both caused by similar sized projectiles from space. Both of those locations were desolate regions at the time of impact. If such an object were to strike a populated area today, it would be devastating for hundreds of miles around the impact site but it would not be an extinction level event like it was for the dinosaurs. The rock that took out the dinosaurs and about two-thirds of the species on planet Earth at that time was about 6 miles across much, much larger than DA14.
Most of us are either unconcerned or just too busy to be bothered by those potentially hazardous asteroids lurking out in space mainly due to how rare it is to have a major impact. What most of us are unaware of are the much more common events that have affected us in the past and will continue to be a threat to us in the future. In reality, our fast paced, electronically dominated society is constantly under attack, even as you are reading this article. In the past, vast populated areas were virtually brought to a halt by these events and as we become more dependent on things like the Internet, cell phones, communication satellites and all those high tech devices, the effects of future attacks may prove to be even worse. No, we're not talking about hackers or anything of an earthbound nature. What we are talking about is the source of most of our energy on this planet our Sun.
The Sun is a powerhouse that has been providing us with energy for billions of years. The Sun's energy is responsible for our everyday survival but the benefits are not completely free. The Sun also generates hazards that until the onset of technology went mostly unnoticed. On the surface of this great ball of hot plasma there are storms brewing. These storms come and go in somewhat of an irregular fashion, caused by twisted magnetic fields that can sometimes erupt in a fury of particles blasted out into space and can travel at a million miles per hour. We call them coronal mass ejections or CMEs. If one of these blasts is pointed at us, we could be in trouble. CMEs can induce a current in power lines and electronic devices resulting in power outages, power surges, and can damage electrical systems in orbiting satellites and here on Earth. They can also be a danger to astronauts in orbit as they would be exposed to large amounts of radiation from the highly energetic particles. Created out of necessity, there is a group that constantly monitors the Sun and its activities. The NOAA Space Weather Prediction Center keeps a close eye on solar events and is the "early warning system" when it comes to the Sun. They give us up to the minute solar weather coverage and are able to provide timely notices of potentially dangerous solar events. Although these events are generally not a direct danger to life on Earth, the effects of a large CME could make it difficult for us technology dependent folks.
The frequency of solar storm activity on the Sun increases and decreases over an 11-year cycle. During this cycle, sunspots - those dark spots which appear randomly on the surface of the Sun (see Figure 1) and are the source of the flares?- will appear to increase in number as we approach the peak of the cycle in 2013 (this year). It's not an exact science but for the most part, the 11-year cycle has been fairly regular in the past.
The period of low sunspot activity called the solar minimum lasted longer than expected this time around and the folks from the Space Weather Prediction Center and the Marshall Space Flight Center are actually predicting a milder solar maximum for this cycle (see Figure 2). Even if that prediction holds, we still have to keep a wary eye. The Sun has surprised us in the past and it will surely do the same in the future.
Although CMEs have the potential to cause havoc in our high tech world, there is one benefit for those of us who appreciate the beauty of the natural world. As a CME strikes the magnetic field surrounding Earth, is causes the field to become distorted and stretched to the point of breaking. When this happens, energy is carried by the magnetic field lines to the north and south magnetic poles and transforms into one of the most beautiful phenomenon I have ever had the pleasure to see the auroras. In the north we call them Aurora Borealis and in the south they are called the Aurora Australis. Whatever you call them, they are mesmerizing displays of light that look like colorful, wispy clouds which are constantly changing shape. A definite "bucket list" item if you've never seen them and you don't need a tablet or cell phone to enjoy the view.
Beyond this column, local astronomers are anxious to share our love of the sky with you. Check out the Adirondack Public Observatory web site at apobservatory.org for events. Listen for me on North Country Public Radio about once a month during "The Eight O'clock Hour" or email firstname.lastname@example.org.