So, you like astrophotography. You spend money and time to photograph the many wonders of the universe to try to get the best images you can.
But do you really know what it is that you are photographing?
We are so often caught up in technical details, all worried about using the right equipment and technique, that we may forget the very nature of what we are trying to capture.
Today we introduce a new type of article, to uncover together the nature of the things that keep us up all night.
But let’s begin with a target that is very special to us, the only target that keeps astrophotographers busy photographing in the daytime.
What Kind Of Star Is The Sun?
If you like technical jargon, the Sun is cataloged as a G-Type main-sequence star.
For the rest of us, the Sun is a fairly bright star. Actually, it is brighter than about 85% of the star population in the Milky Way, which consists of red dwarfs.
Red dwarfs being the “lightest” and cooler type of stars.
But where does the Sun come from?
Where Does The Sun Come From? A Sneak Peek Into Our Star’s Past
Our story begins some billions of years ago, in a cold, quiet and boring corner on the inner rim of the Orion arm of the Milky Way, about 26,000 light-years away from the galactic center, in one of the many interstellar molecular clouds scattered throughout our galaxy.
And nothing really happens here, until …
Meanwhile, a nearby massive star that kept burning hydrogen and helium for hundreds of millions of years is about to have a bad day.
Iron is beginning to be created inside the star’s core, but Iron cannot be fused inside the core of a star.
As the star cannot fuse the Iron, the nuclear reactions in its core slows down.
In just a single day, the star that shone bright for millions or billions of years collapses on itself under its own gravity.
The outer layers of the star fall back on the dense nucleus with such a tremendous force that they rebound outwards in what is known as a supernova explosion.
An explosion so power to briefly outshine its own entire galaxy.
Most of the star’s material is ejected into space with incredible speed and energy and is now rushing towards our placid molecular cloud.
And like a rock thrown in a pond, when the ejected material from the supernova explosion hits our cloud, it sends a series of shockwaves across it, setting things in motion.
Gravity will do the rest. Our Sun is born.
The remaining matter will create the rest of the Solar system: planets, asteroids, and comets, all orbiting the newly born star.
If you want to know more about stars, don’t miss this Stars 101 video from National Geographics.
But nothing is eternal, and the Sun, the solar system, and the life in it are born with an expiration date already set.
Where Is The Sun Going?: A Sneak Peek Into Our Star’s Future
Today the Sun has already shone for about 4.6 billion years now, having happily fused hydrogen and helium for about half of his lifetime.
One day, the Sun too will begin exhausting the hydrogen in its core and it will expand hundreds of times, becoming a red giant.
It will grow so large that its surface will possibly encompass Earth’s orbit, destroying Mercury, Venus, and our planet in the process.
At the end of its life, the Sun will not go supernova: it is not massive enough. Instead, it will shed its outer layers into space, creating a planetary nebula.
Now, all that remains of our once glorious Sun is a white dwarf at the core of the planetary nebula, about the size of Earth.
As white dwarfs can no longer fuse elements in their core, they shine from the residual heat from their heydays, when they were stars.
Eventually, after a time longer than the current age of the universe (13.7 billion years, give or take), they will cool enough to stop glowing, thus turning into a black dwarf.
The future looks dim for our Sun. Literally.
What Is The Sun Made Of?
Like all stars, the Sun too is a giant ball of plasma mostly made of hydrogen and helium.
In a plasma atoms are stripped naked of their electrons and the whole thing is like a superheated soup of free electrons and positively charged atomic nuclei.
How Powerful Is The Sun?
The Sun is not burning and is not a giant ball of fire. Instead, what powers the Sun are nuclear reactions taking place deep down in its core.
We on Earth managed to split heavy atoms to produce energy in a process called nuclear fission.
But the Sun is playing a whole different game: it is so powerful that it fuses together lighter atomic elements to create heavier ones, in a process called nuclear fusion.
We just started to achieve nuclear fusion in our labs, but should we be able to master nuclear fusion, we will solve our energy problem.
In its core, the Sun is currently fusing about 600 million tons of hydrogen into helium every second, converting 4 million tons of matter into energy every second as a result.
How much energy is that? Oh, well, just about that of a trillion 1 megaton bombs all going off at once, or enough to power our entire civilization for almost 500,000 years.
How Hot Is The Sun?
Inside its core, the temperature reaches a staggering 15 million degrees Kelvin, while at its surface, the photosphere, the Sun settles for a more modest 6000K.
Due to a mechanism not yet fully understood, the temperature of the corona, the aura of plasma that surrounds the Sun and that can be photographed during a total solar eclipse, is about 1-2 million degrees, much hotter than the photosphere.
Funny enough, my oldest child, who is 8, enlightened me today with a surprising fact: lightning can heat the air they pass through to 50,000 degrees Fahrenheit (5 times hotter than the surface of the Sun). Luckily for us, this lasts for just a split second.
How Far Is The Sun?
Pretty close, actually: only about 150 million km.
Here’s an interesting fact. The Sun is so dense that a photon produced in the core will take about 100 000 to 170 000 years to reach the surface due to it being absorbed, re-emitted, and scattered backwards during its perilous journey towards the surface.
But once at the photosphere, the photon will take a mere 8-minutes to zoom past us, about 4.6 hours to get to Pluto, and 4 years to reach our next closest star: Proxima Centauri.
How Big Is The Sun?
Not as much as you would think.
Sure, compared to Earth the Sun is huge.
It has a mass of 1.9885×1030 kg (about 333 times the mass of Earth) and has a diameter of about 4.4 million km, 109 times larger than that of our planet.
It is so big and massive that it contains 98% of the mass of the entire Solar System. Yet, it is a puny little star compared to some of the giants that live beyond the Solar System.
Check out this awesome video comparing the Sun to other celestial bodies out there.
Now, we all know that all planets orbit the Sun, right? Wrong!
When you do the math, the center of gravity for the Sun-Jupiter system falls outside the Sun, meaning that both the Sun and Jupiter are orbiting around a point in space.
Earth vs Sun: How Many Earths Can Fit In The Sun?
1.300.000 Earths can fit inside the Sun.
Are There Spacecraft Around The Sun?
The Parker Solar Probe will come as close as 6.16 million km to the Sun, well within the orbit of Mercury, and about seven times closer than any spacecraft has come before.
Looking for more amazing Sun facts? Check out this Sun 101 video from National Geographic
Can I Photograph The Sun?
You should have understood by now the Sun is a powerful beast. Burning mirrors were used to set things on fire by collecting and concentrating sunlight in a point. Solar cookers do the same to cook your food.
Telescopes, lenses, and binoculars work by collecting and focusing the light on your eye’s retina or camera sensor. The risk of destroying your camera, or worse, getting blinded for life is real.
Solar photography is no joke. You need a filter, and you need a full aperture filter made for solar observation and photography. These filters are placed in front of your lens or telescope and filter out the UV and IR radiation, as well as greatly dimming the Sun brightness.
Note that these filters sit in front of the optical instrument, before sunlight gets focused by the instrument. You should NEVER EVER use a solar filter that goes on the eyepiece: the sunlight will be concentrated and focused on it by the instrument, and the risk of cracking the filter is real. You do not want to be looking at the Sun through your telescope when the filter cracks.
Finally, NEVER leave an instrument pointed at the Sun unattended, particularly with kids around.
You are living in a blessed time, where the Moon sits at a distance from us that is just right to appear in the sky as large as the Sun, and this is why we can enjoy total solar eclipses.
But the Moon is receding from us at a rate of about 4cm/year. In a few hundreds of thousands of years from now, the Moon will look noticeably smaller than the Sun, and our distant descendants will never get to witness a total solar eclipse.
In terms of gear, whatever works on the Moon, works on the Sun, plus the solar filter.
The photo above is the first photograph of the Sun: a daguerreotype made by French physicists Hippolyte Fizeau and Léon Foucault. It was taken on April 2, 1845, when photography was in its infancy.
Nowadays, with a classic DSLR, mirrorless, or planetary camera, you can easily photograph the Sun in white light, using just a telephoto lens or a telescope fitted with a solar filter.
With this setup, you can safely photograph sunspots, solar eclipses, and planetary transits with ease.
If you want to get the most out of solar photography, though, you need a specialized (and expensive) solar telescope: with that you can photograph solar flares and coronal ejecta.
Finally, solar activity is not constant with time, but rises and sets in cycles of 11 years. At the time of this article, we just entered the 25th solar cycle, and solar activity is finally going up and it is expected to peak in 2025.
For us astrophotographers, this means we can photograph sunspots and flares more frequently.
If you are interested in checking the solar activity in real-time, you can check the website of NASA’s SOHO mission.
The Sun is our star.
Powerful, beautiful, it makes a great target for astrophotography too.