An extreme stellar outburst from a star (Source: NASA, ESA and D. Player (STScI)
In the past couple of years, scientists have been better able to understand how the Sun's behavior influences Earth, and we will understand it even better thanks to the successful deployment of NASA's Parker Solar Probe. As of now, we've seen several instances of the going-ons of the Sun affecting us in minor to moderate ways; We look to other stars similar to the Sun to understand how the Sun might evolve and how it will consequently impact the future of our planet, and of course, how it will affect life on Earth.
A Rundown on The Sun:
Our Sun is classified as a main-sequence yellow-dwarf (G2V) star. It's currently about halfway through its estimated 10 billion year lifespan, which means it is roughly 4.6 billion years old, and as far as stars go, it's pretty boring and predictable. It's not a red dwarf — a type of star that has so little mass and burns so slowly that they might outlive the universe itself — or a hypergiant — the largest, most energetic, and unpredictable type of star in the universe. It's literally right in between, which is a good thing for us, as it means stars like ours are stable enough for planets in the so-called Goldilocks zone where temperatures are not too hot or not too cold for the evolution of human-like life to take place.
Inside the Sun's core, it is extremely hot, roughly believed to reach temperatures exceeding 27,000,000 degrees Fahrenheit (or 15,000,000 degrees Celsius). The temperatures are hot enough and the Sun is massive enough to sustain the process of nuclear fusion within the core. Therefore, it fuses lighter elements such as hydrogen into heavier elements, up to and including oxygen — a key element that plays a singular role in our continued existence here on Earth.
As previously reported, "The energy produced in the core is what powers the Sun, and produces the heat, light, and radiation the Sun emits. This energy is also an important part of keeping the balance between the Sun and the intense gravitational pull exerted in the Sun's core. One day, there won't be enough energy to counteract the gravitational pull, so the Sun will eventually contract — increasing both the pressure and temperature of the Sun's core. As the amount of helium builds up in the core, the temperature of the fusion reactions will increase in order to counteract the increasing density, which is the beginning of the end."
"This extra energy will result in the Sun first growing brighter, and then the outer layers will swell up, whereby the Sun's atmosphere will increase to something like 200 times its current size, creating a red giant and putting it right in Earth's path."
In the middle of all of that gas shed off into space will be an object roughly the size of Earth, but with approximately half the Sun's mass, known as a white dwarf. These objects are extremely luminous and compact, but not particularly conducive to enabling life on nearby planets... at least not in the inner solar system. For a brief time, the frozen wastelands in the outer solar system — such as Europa and Titan — may become habitable, but life on Earth, if Earth isn't already swallowed up by the expanding Sun, that is, would be toast.
Ch-Ch-Ch Changes
We know it will be a long time until the Sun swallows Earth, but that doesn't mean Earth won't be affected by the Sun's behavior as the star ages. One star scientists are studying to get a glimpse of our Sun's past, present and future is a star located approximately 111 light-years from Earth, known as EK Draconis (after the Draco constellation it resides on the border of). It's a G-type yellow dwarf star just like the Sun. Estimations of its age vary. While some estimates suggest it's older than the Sun, most put it between 50 and 150 million years old — which if true would give us a glimpse at how the Sun may have looked 4.5 billion years ago. Despite the discrepancy in age, it checks off all the boxes for being considered a Sun-like star. Looking back through time and peering upon the star allows us to see how the Sun might have behaved when it was still in its infancy.
A new paper suggests main-sequence stars like our Sun and EK Draconis may not be as stable as we previously thought. The report describes what an international team of astronomers observed coming from EK Draconis: a huge coronal mass ejection significantly bigger than anything our Sun has ever been known to churn out.
What are coronal mass ejections (CME's), you might be asking? Well, they are extremely energetic bursts of highly magnetized plasma and radiation that occur due to instabilities in the Sun's massive magnetic field. They are capable of ejecting "flares" that release what would be equivalent energy to 20 million nuclear bombs within moments.
When one occurs, it's believed that extremely hot gases, known as plasma, bubble up and become all twisted out of shape when the Sun's magnetic field gets "kinks" in it. Ultimately, these superheated gases, which contain massive amounts of charged particles, are shed in the billions of tons from the surface of the Sun. Additionally, the bubbles of gaseous material can travel at speeds as slow as 250 kilometers per second (km/s) to as fast as near 3000 km/s. Sometimes this phenomenon can occur several times a day; sometimes — when the Sun isn't exhibiting much activity — one forms every 5 days or so.
It's semi-rare for a stream of charged particles to hit Earth head-on, but when it does actually happen, it can ignite geomagnetic storms that affect our space-based instruments and tools. According to EarthSky, "The shock wave of charged particles compresses the Earth’s dayside magnetic field while the nightside gets stretched out. Like an elongated rubber band, the terrestrial magnetic field eventually snaps back with the same amount of energy as a bolt of lightning."
"The onslaught of charged particles and the temporary restructuring of the Earth’s magnetic field has observable effects. Auroral lights, usually only seen near the poles, can drift to lower latitudes and become more brilliant. The disturbance of the magnetic field can also expose Earth to deadly cosmic rays. The atmosphere still provides enough protection for everyone on the ground. But astronauts in space may receive lethal doses of radiation. During a solar storm in 1989, cosmonauts aboard the Mir space station received their maximum yearly radiation dose in just a few hours!"
So What Was Observed on EK Draconis?
The paper, which was published in the December 9 issue of the journal Nature Astronomy, is the culmination of more than 32 nights of observation between the winter and spring of 2020. Astronomers from the University of Colorado aimed two satellites — NASA’s Transiting Exoplanet Survey Satellite (TESS) and Kyoto University’s SEIMEI Telescope — at the star system in hopes of witnessing a CME, and witness a CME they did!
On April 5th of 2020, the star was noted as having generated a superflare. Just half an hour later, a truly spectacular CME was spotted spewing from the star's surface at speeds exceeding 994,194 miles (1.6 million kilometers) an hour, making it roughly ten times larger and more powerful than any CME we've ever seen come from a Sun-like star ever before.
Rendering of EK Draconis ejecting a CME as two nearby planets orbit Source: National Astronomical Observatory of Japan
The press release notes, "Recent research, however, has suggested that on the sun, this sequence of events may be relatively sedate, at least so far as scientists have observed. In 2019, for example, Notsu and his colleagues published a study that showed that young sun-like stars around the galaxy seem to experience frequent superflares — like our own solar flares but tens or even hundreds of times more powerful."
"Such a superflare could, theoretically, also happen on Earth’s sun but not very often, maybe once every several thousand years. Still, it got Notsu’s team curious: Could a superflare also lead to an equally super coronal mass ejection?"
“Superflares are much bigger than the flares that we see from the sun,” Notsu said. “So we suspect that they would also produce much bigger mass ejections. But until recently, that was just conjecture.”
"It may also not bode well for life on Earth: The team’s findings hint that the sun could also be capable of such violent extremes. But don’t hold your breath — like superflares, super coronal mass ejections are probably rare around our getting-on-in-years sun."
"Still, Notsu noted that huge mass ejections may have been much more common in the early years of the solar system. Gigantic coronal mass ejections, in other words, could have helped to shape planets like Earth and Mars into what they look like today."
“The atmosphere of present-day Mars is very thin compared to Earth’s,” Notsu said. “In the past, we think that Mars had a much thicker atmosphere. Coronal mass ejections may help us to understand what happened to the planet over billions of years.”