by alan knight
“You’re an astronomy organization, don’t you only hold events at night?” ”What does our Sun have to do with the Stars?” “I had no idea you could star gaze during the day!”
Often SCAS members will hear comments and questions such as those above. Traditionally optical astronomy has been a night-time only event, discounting lectures. Until recently, telescopes for daytime viewing, such as the Hydrogen Alpha telescope, have been so outrageously priced that daylight viewing events were considered cost prohibitive. Now with the cost of these amazing instruments becoming somewhat reasonable and solar-safe filters for normal night use telescopes coming down in price, our move to Sun gazing has become a matter of course.
While amateur astronomers have always had a fairly solid grasp on the processes of our Sun, a star, visitors to our events are playing catch up. The fact that many people never considered our Sun a star tells us we have a generous amount of room for basic education concerning stars. One might say we have an opportunity to shed a little light on the subject.
In our solar system, the Sun is the top dog, making up 99.86% of the mass of our solar system. Nothing is bigger. The Sun is so large we could fit 1.3 million Earths inside our local star (insert jaw drop here). Yeah that’s big. And yet our local star is considered average in size. The largest star we know of, VY Canis Majoris, is up to 2100 times the size of our Sun. If you placed multiple Earths side by side, it would take 109 pale blue dots to span the diameter of our Sun. Consider Jupiter: it would take a mere 11.2 Earths to stretch across the face of the gas giant. To place this in terms slightly more comprehendible, you hop in your private 747 jet airliner and fly to the Sun at 540 MPH at an average distance of 93,000,000 miles (that trip alone would take 7,175 days). With an equatorial circumference of 2,715,000 miles, once at the Sun it would take you 209.4 days to complete one journey around it. The Sun is BIG.
How about that amazing sunrise. First let’s put this in accurate terms: the sun does not rise, nor does it set. We simply rotate towards and away from the Sun. Some of our self-centered geocentric terms will simply be with us forever I suspect. The light that warms our planet, gives us sunburns and helps plants grow is old. Not just 8.26 minutes old, the time it takes for light to travel from the Sun to the Earth, but potentially a million years old plus 8.26 minutes. What? Photons born at the core of our Sun travel a tedious path just to escape the grips of its creator, bouncing off electrons, being absorbed, re-emitted, more bouncing, more absorption and so on. Astrophysicists have calculated the average photon travels no more than 1 centimeter in the core of the Sun before it has some kind of interaction. That interaction could very well bounce the photon back towards the core. After all of that bouncing around the photon finally clears the surface of the Sun and is on its way to Earth… maybe. Keep in mind that for every 500,000,000 photons emitted by the Sun only one hits Earth.
It’s cloudy and I still got sunburned, how? Those photons we spoke of, not only do they arrive at Earth in the visible spectrum, they also arrive at wavelengths outside of the range we can see. The visible spectrum is generally regarded as 390nm to 700nm (656.28nm ring any bells?). Ultraviolet or UV has a range of 400nm to 10nm. It is true that on a cloudy day the amount of UV radiation is reduced, but make no mistake, UV is still getting through the clouds and over time will burn your skin. Now before we write off UV as being completely bad for you, consider that UV is the trigger for your body to naturally produce vitamin D, which helps strengthen bones. Some UV is good for us, just not too much. And in case you wanted to know, UVA has a wavelength of 400 – 315nm while UVB has a wavelength of 315 – 280nm. UVA is not absorbed by our ozone layer while UVB is mostly absorbed.
Could the Sun harm us now? Although this question is not asked too frequently, it still is a very valid and important query that should be addressed. The answer: Yes. In 1859 the Earth was assaulted by an X class solar storm which has been titled The Carrington Event. North America and Europe were not heavily invested in electricity and its infrastructure at the time. This single fact was the determining factor for the Carrington Event not being as devastating as it would be now. At the time, telegraph lines arced and burned. Some telegraph operators reported being shocked by their telegraph key. If a storm of that same magnitude hit Earth today, it would likely cause severe damage to our technology-based society. Satellite communications would be inoperative as satellite operators shut down the communications relays in an attempt to save them from destruction. Power companies would need to shut transformer stations off or lose them. In the United States alone there are more than 300 massive transformers that govern the electrical grid, a single transformer takes months to assemble. If any of these transformers were destroyed, areas of the United States would be without power for the same amount of time it takes to manufacture the transformer, in essence months.
Consider all of the technology that surrounds us that requires electricity to operate: cell phone communications, refrigeration at home and at grocery stores, pumps for water, waste water, fuel, traffic lights, hospitals, fire and police. Certainly several of these entities have backup generators, but when you cannot refuel them the generator becomes useless. Several factors go into how devastating such an event would be, such as location of impact and infrastructure in that area. It is estimated that an event such as this could cost the United States upward of $2.6 trillion to recover from. Unfortunately our technology based society has not developed far enough to combat the effects of a massive CME strike. Companies in the power distribution industry are working towards “hardening” transformer facilities against such an assault, but they are not there yet. Consider life without electricity for nine months, how difficult life could become.
Will our Sun last forever? About 4.6 billion years ago, the switch was turned on, through thermonuclear fusion. Since then the Sun has been steadily turning Hydrogen into Helium at a rate of 600,000,000 tons per second. To refine that number, the Sun converts 595,000,000 tons of Hydrogen into Helium per second, the remaining 5,000,000 tons is converted to more exotic elements including light. I know, another one of those hard to fathom numbers. The average car weighs 4,000 pounds, plug that average in and the Sun would be burning 300,000,000 cars per second. In 2010 there were an estimated 1.015 billion vehicles in the world. Simple enough, the Sun would consume every car in the world in 3.383 seconds.
With our local star being mid-life we can expect another 5 billion years from it, after that all bets are off. If Earth’s inhabitants survive over the next 5 billion years, Earth will no longer be the place to call home. After the Sun consumes all of its Hydrogen, it then moves on to burning Helium. During this phase the Sun swells into a Red Giant with a diameter 100 times that which it is now. Mercury and Venus, see ya! Gone as the expanding Sun engulfs these inner planets. Earth, might or might not get consumed as the Sun expands, however it really doesn’t matter as the proximity to the Red Giant and its heat will leave the Earth little more than a scorched ember. Even that process really has no bearing on us as the Sun’s solar output increases by 10% every billion years. We’ll have long left Earth (or should have) before the end of the Sun life cycle. Our atmosphere will simply be too hot to sustain life. If we could somehow survive until our star ballooned into a Red Giant, our entire sky would be fill with the Sun, quite a sight, I image. Once the Sun burns all of its fuel and can no longer generate the temperatures needed to fuse heavier elements past carbon, it collapses into a white dwarf.
The average size of a white dwarf is comparable to that of Earth, except the star still has the mass of the Sun. Gravity on our white dwarf will be roughly 350,000 times what it is on Earth. For the sake of argument let’s say we somehow manage to survive the red giant to white dwarf phase on a Europa Moon base. Discounting technology, what little heat our now white-dwarf star gave off, would all but disappear, leaving our solar system extremely cold.
The questions above are just a small sample of what our guests bring to us at outreach events. It’s wonderful to know people do want to understand a little more than they knew before visiting with us. Whether our visitors have questions or simply wish to look through the telescopes makes no difference, we are connecting with our community and providing a valuable service, a service we are certainly ready to fulfill.