These extreme UV light images from the Solar Dynamics Observatory shows the Sun at solar minimum (left, Dec. 2019) compared to the current solar maximum. Image Credit: NASA/SDO
For most of human history, the Sun appeared stable. It was a stoic stellar presence, going about its business fusing hydrogen into helium beyond our awareness and helping Earth remain habitable. But in our modern technological age, that facade fell away.
We now know that the Sun is governed by its powerful magnetic fields, and as these fields cycle through their changes, the Sun becomes more active. Right now, according to NASA, the Sun is at its solar maximum, a time of increased activity.
The earliest datable sunspot drawings based on Johannes Kepler's solar observations with camera obscura in May 1607.
Johannes Kepler is probably most well known for developing the laws of planetary motion. He was also a keen solar observer and in 1607 made some wonderful observations of our nearest star using a camera obscura. His drawings were wonderfully precise and enabled astronomers to pinpoint where the Sun was in its 11-year cycle. Having taken into account Kepler’s location and the location of sunspots, a team of researchers have identified the Sun was nearing the end of solar cycle-13.
Image of a solar flare (bright flash) obtained by NASA’s Solar Dynamics Observatory on Oct. 2, 2014, with a burst of solar material erupting being observed just to the right of the solar flare. (Credit: NASA/SDO)
Two recent studies published in The Astrophysical Journal discuss findings regarding solar flare properties and a new classification index and the Sun’s magnetic field, specifically what’s called solar magnetic reconnection. These studies hold the potential to help researchers better understand the internal processes of the Sun, specifically pertaining to solar flare activity and space weather. Here, Universe Today discusses these two studies with both lead authors regarding the motivation behind the studies, significant results, and implications on our understanding regarding solar flares and space weather.
Sunspot region 3590 which is located at a fairly high latitude produced two impulsive X-class events. The first solar flare peaked yesterday at 23:07 UTC with a maximum X-ray flux of X1.9 and the second solar flare peaked today at 06:32 with a maximum observed X-ray flux of X1.7. Both events caused a brief strong R3 radio blackout at the day-side of our planet.
The Sun is heading toward solar maximum (which is likely to be about a year away) and as it does, there will be more sunspots, solar flares and coronal mass ejections. Over the last 24 hours there has been three, yes three X-class flares, the first peaking at X1.9, the second 1.7 and the final one a mighty 6.3. Flares of this magnitude caused radio blackouts, disruption to mobile phones and radio transmissions.
Image of the Sun from Solar Orbiter (left Feb 2021 and right Oct 2023)
The solar cycle has been reasonably well understood since 1843 when Samuel Schwabe spent 17 years observing the variation of sunspots. Since then, we have regularly observed the ebb and flow of the sunspots cycle every 11 years. More recently ESA’s Solar Orbiter has taken regular images of the Sun to track the progress as we head towards the peak of the current solar cycle. Two recently released images from February 2021 and October 2023 show how things are really picking up as we head toward solar maximum.
Computer simulation of magnetic structures in solar-like conditions. Image: Jörn Warnecke
It’s almost impossible to over-emphasize the primal, raging, natural power of a star. Our Sun may appear benign in simple observations, but with the advanced scientific instruments at our disposal in modern times, we know differently. In observations outside the narrow band of light our eyes can see, the Sun appears as an enraged, infuriated sphere, occasionally hurling huge jets of plasma into space, some of which slam into Earth.
Jets of plasma slamming into Earth isn’t something to be celebrated (unless you’re in a weird cult); it can cause all kinds of problems.
Stone causeway atop Mount Tlaloc, Mexico. Credit: Ben Messiner/UCR
Pre-Columbian Mexico (or Mesoamerica) hosted one of the largest civilizations and populations in the world. The most well-known and dominant of these civilizations (prior to the arrival of the Conquistadors) were the Aztecs (or Mexica). Their empire, known as the Triple Alliance, was centered around Lake Texcoco and consisted of the major cities Tenochtitlan, Texcoco, and Tlacopan. In addition to engineering massive temples, aqueducts, canal systems, and estuaries, the Aztecs are renowned for being accomplished astronomers and agronomists.
At the height of their power, the Aztec Empire supported a population of up to 3 million in the Valley of Mexico, and many of their largest cities had populations exceeding 100,000. This was not easy, given that the region is characterized by arid springs followed by winter monsoons. According to recent research by the University of California Riverside (UCR), the Aztecs used mountain alignments as a solar observatory to create an accurate agricultural calendar. This allowed their farmers to produce enough food to feed one of the most densely-populated regions on Earth.
Sunspots are one of the ways we can measure the activity level of the Sun. Generally, the more sunspots we observe, the more active the Sun is. We’ve been tracking sunspots since the early 1600s, and we’ve long known that solar activity has an 11-year cycle of high and low activity. It’s an incredibly regular cycle. But from 1645 to 1715 that cycle was broken. During this time the Sun entered an extremely quiet period that has come to be known as the Maunder Minimum. In the deepest period of the minimum, only 50 sunspots were observed, when typically there would be tens of thousands. We’ve never observed such a long period of quiet since, and we have no idea why it occurred.
A (nearly) naked Sol... more the norm than the exception these days. Credit: NASA/SDO AIA 512/1600 imager.
A (nearly) naked Sol… more the norm than the exception these days. Credit: NASA/SDO AIA 512/1600 imager.
Have you been keeping an eye on Sol lately? One of the top astronomy stories for 2018 may be what’s not happening, and how inactive our host star has become.
The strange tale of Solar Cycle #24 is ending with an expected whimper: as of May 8th, the Earthward face of the Sun had been spotless for 73 out of 128 days thus far for 2018, or more than 57% of the time. This wasn’t entirely unexpected, as the solar minimum between solar cycle #23 and #24 saw 260 spotless days in 2009 – the most recorded in a single year since 1913. Cycle #24 got off to a late and sputtering start, and though it produced some whopper sunspots reminiscent of the Sol we knew and loved on 20th century cycles past, it was a chronic under-performer overall. Mid-2018 may see the end of cycle #24 and the start of Cycle #25… or will it?
The story thus far… and the curious drama that is solar cycle #24. Credit: David Hathaway/NASA Marshall Spaceflight Center.
One nice surprise during Cycle #24 was the appearance of massive sunspot AR 2192, which popped up just in time for the partial solar eclipse of October 23rd, 2014. Several times the size of the Earth, the spot complex was actually the largest seen in a quarter century. But just as “one swallow does not a Summer make,” one large sunspot group couldn’t save Solar Cycle #24.
The partial eclipse of the Sun, October 23, 2014, as seen from Jasper, Alberta, shot under clear skies through a mylar filter, on the front of a 66mm f/6 apo refractor using the Canon 60Da for 1/8000 (!) sec exposure at ISO 100. The colors are natural, with the mylar filter providing a neutral “white light” image. The big sunspot on the Sun that day is just beginning to disappear behind the Moon’s limb. The mylar filter gave a white Sun, its natural colour, but I have tinted the Sun’s disk yellow for a more pleasing view that is not just white Sun/black sky. Image credit and copyright: Alan Dyer/Amazing Sky.net
The Sun goes through an 11-year sunspot cycle, marked by the appearance of new spots at mid- solar latitudes, which then slowly progress to make subsequent appearances closer towards the solar equator, in a pattern governed by what’s known as Spörer’s Law. The hallmark of a new solar cycle is the appearance of those high latitude spots. The Sun actually flips overall polarity every cycle, so a proper Hale Cycle for the Sun is actually 11 x 2 = 22 years long.
A big gaseous fusion bomb, the Sun actually rotates once every 25 days near its equator, and 34 days at the poles. The Sun’s rotational axis is also tipped 7.25 degrees relative to the ecliptic, with the northern rotational pole tipped towards us in early September, while the southern pole nods towards us in early March.
An animation of massive susnpot AR 2192 crossing the Earthward face of Sol from October 17th to October 29th, 2014. Credit: NASA/SDO.
What’s is store for Cycle #25? One thing’s for certain: if the current trend continues, with spotless days more the rule than the exception, we could be in for a deep profound solar minimum through the 2018 to 2020 season, the likes of which would be unprecedented in modern astronomy.
Fun fact: a similar dearth of sunspots was documented during the 1645-1715 period referred to as the Maunder Minimum. During this time, crops failed and the Thames River in London froze, making “frost fairs” along its frozen shores possible. Ironically, the Maunder Minimum also began just a few decades after the dawn of the age of telescopic astronomy. During this time, the idea of “spots on the Sun” was regulated to a controversial, and almost mythical status in mainstream astronomy.
Keeping Vigil on a Tempestuous (?) Star
We’ve managed to study the last two solar cycles with unprecedented scrutiny. NASA’s STEREO-A and -B spacecraft (Only A is currently active) monitors the farside of the Sun from different vantage points. The Solar Dynamics Observatory (NASA SDO) keeps watch on the Sun across the electromagnetic spectrum. And our favorite mission, the joint NASA/European Space Agency’s SOHO spacecraft, has monitored the Sun from its sunward L1 Lagrange vantage point since it launched in 1995—nearly through one complete 22 year Hale Cycle by mid- 2020s. Not only has SOHO kept a near-continuous eye on Sol, but it’s also discovered an amazing 3,398 sungrazing comets as of September 1st, 2017… mostly due to the efforts of diligent online amateur astronomers.
A guide to features on the Sun. The left view in Calcium-K shows the photosphere and is similar to a standard whitelight view, and the right view shows features in the chromosphere in hydrogen-alpha. Credit: Paul Stewart Instagram: @Upsidedownastronomer/annotations by Dave Dickinson
…and did you know: we can actually model the solar farside currently out of view from the Earth to a high degree of fidelity thanks to the advent of powerful computational methods used in the nascent field of solar helioseismology.
Unfortunately, this low ebb in the solar cycle will also make for lackluster aurora in the years to come. It’s a shame, really… the relatively powerful cycles of the 1970s and 80s hosted some magnificent aurorae seen from mid-latitudes (and more than a few resulting blackouts). We’re still getting some minor outbursts, but you’ll have to venture “North/South of the 60” to really see the aurorae in all of its splendor over the next few years.
But don’t take our word for it: get out there and observe the Sun for yourself. Don’t let this discourage you when it comes to observing the Sun. Even near its minimum, the Sun is a fascinating target of study… and unlike most astronomical objects, the face of the Sun can change very quickly, sometimes erupting with activity from one hour to the next.
We like to use a Coronado Personal Solar Telescope to monitor the Sun in hydrogen-alpha for prominences and filaments: such a scope can be kept at the ready to pop outside at lunch time daily for a quick look. For observing sunspots and the solar photosphere in white-light, you’ll need an approved glass filter which fits snugly over the aperture end of your telescope or camera, or you can make a safe solar filter with Baader Safety Film.
Safe ways to observe the Sun: a homemade whitelight filter (left) and a Coronado PST solar telescope (right). Images by author.
Does the sunspot cycle tell the whole picture? Certainly, the Sun most likely has longer, as yet undiscovered cycles. For about a century now, astronomers have used the Wolf Sunspot Number as calculated mean average to describe the current state of activity seen on the Sun. An interesting study calls this method into question, and notes that the direction and orientation of the heliospheric current sheet surrounding the Sun seems to provide a better overall depiction of solar activity.
Other mysteries of the Sun include: just why does the solar cycle seem baked in at 11 years? Why don’t we ever see spots at the poles? And what’s in store for the future? We do know that solar output is increasing to the tune of 1% every 100 million years… and a billion years from now, Earth will be a toasty place, probably too warm to sustain liquid water on its surface…
Which brings us to the final point: what role does the solar cycle play versus albedo, global dimming and climate? This is a complex game to play: Folks have literally gone broke trying to link the solar cycle with terrestrial human affairs and everything from wheat crops to stock market fluctuations. Many a climate change-denier will at least concede that the current climate of the Earth is indeed changing, though they’ll question human activity’s role in it. The rather ominous fact is, taking only current solar activity into account, we should be in a cooling trend right now, a signal in the data that anthropogenic climate change is working hard against.
See for yourself. You can keep track of Sol’s daily activity online: our favorite sites are SpaceWeather, NOAA’s space weather/aurora activity page, and the SOHO and SDO websites.
Be sure to keep tabs of Sol, as the next solar minimum approaches and we ask the question: will Cycle #25 occur at all?
Well, we’re finally emerging from our self-imposed monastic exile that is editing to mention we’ve got a book coming out later this year: The Universe Today Ultimate Guide to Viewing the Cosmos: Everything You Need to Know to Become an Amateur Astronomer, and yes, there’s a whole chapter dedicated to solar observing and aurora. The book is up for pre-order now, and comes out on October 23rd, 2018!
Artists impression of a Super-Earth, a class of planet that has many times the mass of Earth, but less than a Uranus or Neptune-sized planet. Credit: NASA/Ames/JPL-Caltech
Red dwarf stars have proven to be a treasure trove for exoplanet hunters in recent years. In addition to multiple exoplanets candidates being detected around stars like TRAPPIST-1, Gliese 581, Gliese 667C, and Kepler 296, there was also the ESO’s recent discovery of a planet orbiting within the habitable zone of our Sun’s closest neighbor – Proxima Centauri.
And it seems the trend is likely to continue, with the latest discovery comes from a team of European scientists. Using data from the ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) and HARPS-N instruments, they detected an exoplanet candidate orbiting around GJ 536 – an M-class red dwarf star located about 32.7 light years (10.03 parsecs) from Earth.
According to their study, “A super-Earth Orbiting the Nearby M-dwarf GJ 536“, this planet is a super-Earth – a class of exoplanet that has between more than one, but less than 15, times the mass of Earth. In this case, the planet boasts a minimum of 5.36 ± 0.69 Earth masses, has an orbital period of 8.7076 ± 0.0025 days, and orbits its sun at a distance of 0.06661 AU.
Artist’s impression of a system of exoplanets orbiting a low mass, red dwarf star. Credit: NASA/JPL
The team was led by Dr. Alejandro Suárez Mascareño of the Instituto de Astrofísica de Canarias (IAC). The discovery of the planet was part of his thesis work, which was conducted under Dr Rafael Rebolo – who is also a member of the IAC, the Spanish National Research Council and a professor at the University of Laguna. And while the planet is not a potentially habitable world, it does present some interesting opportunities for exoplanet research.
As Dr. Mascareño shared with Universe Today via email:
“GJ 536 b is a small super Earth discovered in a very nearby star. It is part of the group of the smallest planets with measured mass. It is not in the habitable zone of its star, but its relatively close orbit and the brightness of its star makes it a promising target for transmission spectroscopy IF we can detect the transit. With a star so bright (V 9.7) it would be possible to obtain good quality spectra during the hypothetical transit to try to detect elements in the atmosphere of the planet. We are already designing a campaign for next year, but I guess we won’t be the only ones.”
The survey that found this planet was part of a joint effort between the IAC (Spain) and the Geneva Observatory (Switzerland). The data came from the HARPS and HARPS-N instruments, which are mounted on the ESO’s 3.6 meter telescope at the La Silla Observstory in Chile and the 3.6 meter telescope at the La Palma Observatory in Spain. This was combined with photometric data from the All Sky Automated Survey (ASAS), which has observatories in Chile and Maui.
The research team relied on radial velocity measurements from the star to discern the presence of the planet, as well as spectroscopic observations of the star that were taken over a 8.6 year period. For all this, they not only detected an exoplanet candidate with 5 times the mass of Earth, but also derived information on the star itself – which showed that it has a rotational period of about 44 days, and magnetic cycle that lasts less than three years.
Artist’s depiction of the interior of a low-mass star, such as the one seen in an X-ray image from Chandra in the inset. Credit: NASA/CXC/M.Weiss
By comparison, our Sun has a rotational period of 25 days and a magnetic cycle of 11 years, which is characterized by changes in the levels of solar radiation it emits, the ejection of solar material and in the appearance of sunspots. In addition, a recent study from the the Harvard Smithsonian Center for Astrophysics (CfA) showed that Proxima Centauri has a stellar magnetic cycle that lasts for 7 years.
This detection is just the latest in a long line of exoplanets being discovered around low-mass, low-luminosity, M-class (red dwarf) stars. And looking ahead, the team hopes to continue surveying GJ 536 to see if there is a planetary system, which could include some Earth-like planets, and maybe even a few gas giants.
“For now we have detected only one planet, but we plan to continue monitoring the star to search for other companions at larger orbital separations,” said Dr. Mascareño. “We estimate there is still room for other low-mass or even Neptune-mass planets at orbits from a hundred of days to a few years.”
The research also included scientists from the Astronomical Observatory at the University of Geneva, the University of Grenoble, The Astrophysical and Planetological Insitute of Grenoble, Institute of Astrophysics and Space Sciences in Portugal, and the University of Porto, Portugal.
