The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do.
– Galileo Galilei [via Wise Old Sayings]
The Sun, our Sun. Nourishing our planet and warming us. Taking care of us like a loving parent.
The Sun has always captivated us. Many ancient civilizations worshipped the Sun. It is justified because none of us would exist without it. Nowadays Sun worship means something a little different.
But our awe of the Sun continues. Now we seek to advance our knowledge with science. And once again, it is justified because we continue to exist because of it. It is our lifeblood.
Many of us know a bit about the Sun. We know it can warm us. We know it can burn us. We know it helps our food grow. And its light takes 8 minutes to reach us. We know that we orbit around it instead of the other way around.
Despite everything that we know, I would venture to say most of us take it for granted. It’s easy to regard it as a burning ball in the sky that comes up during the day. We don’t give it a thought and go about our day. Unless we planned an outdoor activity that day and then we curse the clouds.
That is the reason for this article. The Sun has many more mysteries to uncover yet is so vital to our existence. Consider this article my way of saying thank you to the Sun.
Before I delve into more advanced information, here is a little primer…
Age: 4.5 billion years old
Diameter: 860,000 miles diameter (about 110 Earths)
Distance: 93 million miles away from Earth
Composition of mass: 75% Hydrogen and 25% Helium with about .1% made up of other elements
Layers: From the center out, the core, the radiative zone, the convective zone, the photosphere, the chromosphere, and the outermost layer, the corona.
State of Matter: Plasma (not a solid, liquid, or gas)
Hottest part of the Sun: The core at 28 million degrees Fahrenheit
Energy created by: Fusion (the fusing of Hydrogen to create Helium, plus mass and energy)
Now on to the 10 things you may not know about our Sun.
1. Sun terminology (from our romantic perspective)
Sunrise and Sunset – The moment the upper edge, or limb, of the Sun is at the horizon.
Transit – The instant when the Sun appears highest in the sky. Also known as solar noon.
Twilight – There are 3 types of twilight: civil, nautical, and astronomical. The time before sunrise and after sunset when the sky is still illuminated by the Sun. The different types differ by the number of degrees below the horizon the center of the Sun is. For civil, nautical, and astronomically it is 6, 12, 18 degrees sequentially.
For civil twilight, during good weather terrestrial objects will be clearly distinguished. For nautical twilight, the general outlines of ground objects will be distinguishable. For astronomical twilight, sky illumination is so faint that it is practically imperceptible.
Dawn and Dusk – Once again, there is a civil, nautical, and astronomical version. Dawn is the moment twilight begins in the morning. Likewise, dusk is the moment twilight ends in the evening.
If you want to look at times for your location. Refer to the U.S. Naval Observatory Astronomical Applications Department Complete Sun and Moon Data page.
It is easy to forget that what we witness is just because of our perspective here on Earth. The Sun appears to move relative to the Earth. Of course, it is the Earth that rotates.
2. What is heliophysics and why we need it
Heliophysics is a big word. It is the science related to Sun-Earth connections. The field encompasses space physics, astrophysics, and climate studies. Essentially, the goal is to better understand how the Sun affects the Earth and our solar system.
If you want the full laundry list of what the studies include, here it is: cosmic rays, particle acceleration, aurorae, space weather, radiation, dust, magnetic reconnection, magnetohydrodynamics, solar activity and stellar cycles, aeronomy and space plasmas, magnetic fields and global change, and the interactions of the solar system with our galaxy.
You may think that we know all there is to know about the Sun. Wrong! Many unanswered questions still remain. Why is the corona hotter than the photosphere? Why and how does the Sun vary? and more.
Why are these questions important, you ask? Because what happens in the Sun directly impacts us. Here on Earth, we experience the consequences of Sun storms through:
• Aurora borealis, the northern lights, and aurora australis, the southern lights
• Communication disruptions
• Radiation hazards to orbiting astronauts and spacecraft
• Current surges in power lines
• Orbital degradation
• Corrosion in oil and gas pipelines
There are ongoing initiatives to address these issues. Many thanks to the scientists and engineers who are hard at work to enlighten our current understanding.
3. The next total solar eclipse
As I am sure you are aware, an eclipse is when the sight of a celestial body is obscured by a shadow cast by another body. So a solar eclipse is when the Sun is obscured because the Earth passes through the moon’s shadow.
In this case, a picture is worth a thousand words. The image on right shows a total and partial eclipse.
There are 3 types of solar eclipse: partial, annular, and total.
The total eclipse is when the entire Sun is obscured. Partial eclipses obscure any part, but not all, of the Sun. Annular are special cases of partial and are concentrically aligned such that only an outer ring of the Sun is not obscured by the shadow.
Annular eclipses happen because the moon orbits in an elliptical pattern and is sometimes closer to the Earth and sometimes a little farther away.
We are at a special time in the life of our solar system that allows us to see eclipses. The Sun is about 400 times farther away from us than the moon. Coincidentally, the diameter of the Sun is about 400 times larger than the moon. That allows the Sun to be obscured while we can still see the corona. Slowly, the moon is moving farther away from the Earth and the shadow will not be the same.
Total solar eclipses don’t occur often. For any given place on the planet, a total eclipse will occur only every 375 years on average. So, you are lucky if you get to see one in your lifetime.
As it turns out, there will be a total solar eclipse crossing the United States in 2017. What an opportunity! From what I have read, experiencing a full eclipse escapes words. It sounds otherworldly. I have already planned on making a trek to be able to see it for myself. Here’s hoping for cloudless skies across the nation on August 21, 2017.
To learn the details about the coming eclipse you can visit the NASA Solar Eclipse page or the U.S. Naval Observatory Astronomical Applications Department 2017 Solar Eclipse page. These sites have loads of information to help you decide if you want to see it as well.
4. Current programs and missions
As I mentioned, there are ongoing efforts to know more about heliophysics. From the NASA Science Plan, there are currently 3 research objectives in the heliophysics area. They are:
1. Open the Frontier to Space Environment Prediction: To deepen our understanding of the physical processes happening in our solar system so we are better able to manage future events.
2. Understand the Nature of Our Home in Space: To understand how the variations of the Sun and planets affect humans and our civilization.
3. Safeguard the Journey of Exploration: To enable forecasting of space conditions for the safety of human and robotic missions.
Did you know that anyone can submit a proposal for future missions? Of course, they must abide by the specific rules and align with identified goals and objectives. But it is possible to get your ideas put into action. How cool would that be?
(If you want to become a citizen scientist, see related: Have some time? Volunteer online)
There are programs that align with the mentioned research objectives. One of the programs is called Life with a Star or LWS. This project aims to understand how human life and society are influenced by the Sun.
Another project is Solar Terrestrial Probes (STP). The program puts the tools into place to gather data that can lead to further understanding.
Alongside these programs there are missions. These flight missions range from balloons, sounding rockets, airplanes, interplanetary probes to flagship observatories. The sky’s the limit, literally. Take a look at the NASA information on past, present, and future NASA missions.
5. What we see isn’t always what we get
Light comes in many different wavelengths. Spectrometers can see many wavelengths at the same time. This tells us what kind of light and how much of it is coming from the Sun. It doesn’t provide images, only data, but it can inform us as to which tools to use to get images for specific events.
The light is measured in Angstroms (Å). Each wavelength can give us different kinds of information about the Sun.
The image below is a picture of the Sun in different wavelengths. Note that:
• images of the photosphere in visible light (third in the top row) and 4500 Å (first in second row) highlight the sunspots well
• images of the corona at 171 Å (fourth in the second row) the magnetic arcs or coronal loops are highlighted
There is definitely more there than meets the eye. Like a mother with her children, I can’t pick a favorite.
6. Space weather? Yup, and it’s a doozy
The solar wind is one aspect of solar weather. It comes from the corona of the Sun and travels around 1 million miles per hour.
The solar wind is not constant however. It varies based on activity within the corona such as coronal holes and streamers. These variations buffet the Earth’s magnetic field and can cause storms in the Earth’s magnetosphere.
Just like wind on the Earth, the solar wind can carry things in it and interact with other winds. Also like the wind on Earth, it is constantly monitored. You can look up the current solar weather conditions such as wind, flare, sunspots at SpaceWeather.com.
See the video below for a look at what this looks like.
7. We all like a routine, even the Sun
Did you know that the Sun has its own regular cycle of activity? It does.
The “solar cycle” lasts for 11 years. It is based on the changing magnetic field and results in different levels of Sun activity. The activity being sunspots, flares and the like. Peak activity time is called the solar maximum while the lowest activity level is the solar minimum.
• Sunspots are seen as dark spots. The spots are concentrated areas of magnetic flux. They are cooler than the surrounding area which is why they appear dark.
• Flares are sudden, hot release of built of energy from a localized area. The energy is in the form of electromagnetic radiation, energetic particles, and mass motions.
• Storms are areas of increased activity with solar flares and coronal mass ejections.
8. Make up your magnetic mind already
Once again, the Sun and the Earth share something else in common. Magnetic changes.
Coinciding with the solar cycle mentioned above, the magnetic poles switch every 11 years or so. The poles don’t change like a flip of the switch. It is long and complicated. The Sun’s polar magnetic fields weaken, go to zero and then emerge again with the opposite polarity. These changes in the magnetic poles can influence our weather here on Earth.
Since the solar cycle occurs somewhat frequently, scientists have been able to witness several flips over the course of the past few decades.
Perhaps this can inform us of how a pole reversal would work on Earth. We don’t really know the repercussions of that. It is an interesting question because it is our magnetic field that protects us from a lot of the radiation from the Sun.
Magnetic flips on Earth average about every 250,000 years. We are overdue as it has been twice that long since Earth has seen a reversal of polarity. We know all of this because of sediment on the bottom of the oceans.
The video below shows the chaotic change take place on the Sun. The dark pink color presents negative and the green line represent positive.
9. Tantrums of the Sun
Sunspots aren’t the only solar events. There is a lot of turbulent activity on the Sun. If the Sun were a human we would say that it was continuously throwing a tantrum.
We know about the hotbed of activity on a molecular level, but many events are on a much grander scale, the scale of the Earth or larger.
I used the SOHO glossary from NASA to help define the terms. The image below displays how it these events.
- Coronal Mass Ejection: A huge magnetic bubble of plasma that erupts from the Sun’s corona and travels through space at high speed. The big daddy of them all. (biggest image marked CME)
- Flare: Rapid release of energy from a localized region on the Sun in the form of electromagnetic radiation, energetic particles, and mass motions. More localized. (biggest image marked Fl)
- Filament: A structure in the corona consisting of cool plasma supported by magnetic fields. Filaments are dark structures when seen against the bright solar disk, but appear bright when seen over the solar limb, Filaments seen over the limb are also known as prominences. (top left image marked F)
- Plage: Bright areas seen near sunspots in the chromosphere. Seen in H-alpha light. From the French forbeach. (top left image marked P)
- Prominence: A structure in the corona consisting of cool plasma supported by magnetic fields. Prominences are bright structures when seen over the solar limb, but appear dark when seen against the bright solar disk. Prominences seen on the disk are also known as filaments. (middle left image marked Pr)
To better understand the magnitude of a coronal mass ejection, take a look at this video from NASA/SDO/STEREO/ESA/SOHO/Wiessinger. The music makes it all the more intense.
10. The future of the Sun and us
Where do we and the Sun go from here? Well, all good things must come to an end. We eventually must part ways with our Sun.
Withstanding our own self-destruction and other random acts of nature (comets, gamma ray bursts, stars passing close by) the way for the human race to survive in the long term is to leave Earth.
The Earth will either be swallowed up by the expanding red giant Sun or be flung out of the solar system by changing gravitational forces. With all the things that can happen before that, we should plan on making a graceful exit on our own terms. Perhaps joining other life in the universe.
As for the future of the Sun, it still has a while to go. What will come of the Sun in the future…
• in 5.4 billion years: hydrogen exhaustion and turn into a red giant
• in 6.4 billion years: white dwarf
• in ~10 quadrillion years: black dwarf (in theory, it remains to be proven/seen)
Whatever comes of the Sun, it gave us our beginnings. I hope that we part on favorable terms.
Shedding any light on it?
Sorry, I really like puns. Did this article illuminate anything for you? It is so easy to take the Sun for granted, but it is responsible for all that we have ever encountered. It is everything.
Hopefully, this information will help you better appreciate the power of the Sun. It is hard to image all the activity when the scale is so beyond anything that we can reference. So overwhelming.
Next time you step out, rain or shine, take a moment to think about the wonder of the Sun. Then put on your sunglasses and enjoy the light.
Do you have any other information to share with the community? Let us all know in the comments.
Berman, Bob. The Sun’s Heartbeat: And Other Stories from the Life of the Star That Powers Our Planet. New York: Little, Brown, 2011. Print.
Chromospheric Features from Marshall Space Flight Center
Coincidence that sun and moon seem same size? from EarthSky
Cooper, Christopher, David N. Spergel, and Madhulika Guhathakurta. Our Sun: Biography of a Star. New York: Race Point, 2013. Print.
Definitions from SunriseSunset
Evidence from Binary Research Institute.org
Heliophysics from NASA Science
Infographic: Types of Solar Eclipse from TimeandDate
Living With a Star Program from Goddard Space Flight Center
NASA Goddard from YouTube
Our Star the Sun from SOHO
Science Plan For NASA’s Science Mission Directorate 2007–2016 from NASA Science
Solar Astronomy Resources from Stanford Solar Center
Solar Flares from Marshall Space Flight Center