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.
An artists concept of the Solar Orbiter spacecraft studying the Sun. Credit: ESA.
On April 10th, ESA’s Solar Orbiter made its closest flyby of the Sun, coming to within just 29% of the distance from the Earth to the Sun. From this vantage point, the spacecraft is performing close-up studies of our Sun and inner heliosphere. This is basically uncharted territory, as we’ve never had a spacecraft this close to the Sun.
One of the goals of the mission is to figure out why the Sun’s corona — its outer atmosphere — is so hot. The corona can reach temperatures of 2 million degrees C, vastly hotter than its 5,500 C surface. A new paper based on Solar Orbiter data, may offer some clues.
You’ve probably never seen our Sun look like this before. This bizarre image of old Sol is made from data produced by three different space telescopes, each observing the Sun at a different wavelength.
A moderate solar flare erupts on the sun July 8, 2014 in this image from NASA's Solar Dynamics Observatory. Credit: NASA/SDO
Using data from the Solar Dynamics Observatory, scientists have discovered new clues that could help predict when and where the next solar flare might blast from the Sun.
Researchers were able to identify small flashes in the upper layers of the corona – the Sun’s atmosphere – found above regions that would later flare in energetic bursts of light and particles released from the Sun. The scientists compared the flashes to small sparklers before the big fireworks.
NASA has created a video based on 133 days of observations by the Solar Dynamics Observatory. The hour-long video is a captivating look at four months of the Sun's approximately 10 billion year lifetime. Image Credit: NASA/Goddard Space Flight Center/SDO
NASA’s Goddard Space Flight Center has released an hour-long time-lapse video that shows 133 days of the Sun’s life. The video shows the Sun’s chaotic surface, where great loops of plasma arch above the star along magnetic field lines. Sometimes the looping plasma reconnects to the star, and other times it’s ejected into space, creating hazardous space weather.
X9.3 Flare blasts off the Sun. Image credit: NASA/GSFC/SDO
Since it launched in 2010, the Solar Dynamics Observatory has helped scientists understand how the Sun’s magnetic field is generated and structured, and what causes solar flares. One of the main goals of the mission was to be able to create forecasts for predicting activity on the Sun.
Using mission data from the past 10 years, SDO scientists have now developed a new model that successfully predicted seven of the Sun’s biggest flares from the last solar cycle, out of a set of nine.
I think we all do sometimes. It’s easy to take for granted. The Sun is that glowing thing that rises in the morning and sets in the evening that we don’t generally pay attention to as we go about our day. However, there are these rare moments when we’re reminded that the Sun is truly a STAR – a titanic living sphere of hydrogen smashing plasma a million times the volume of Earth. One of those rare moments for me was standing in the shadow of the 2017 solar eclipse. We had driven down from Vancouver to Madras, Oregon to watch this astronomical freak of nature. A moon hundreds of times smaller than the Sun, but hundreds of times closer, covers the face of the Sun for the majesty of a STAR to be revealed; the fiery maelstrom of the Sun’s atmosphere visible to the naked eye.
Do you wonder how astronomers find all those exoplanets orbiting stars in distant solar systems?
Mostly they use the transit method. When a planet travels in between its star and an observer, the light from the star dims. That’s called a transit. If astronomers watch a planet transit its star a few times, they can confirm its orbital period. They can also start to understand other things about the planet, like its mass and density.
The planet Mercury just transited the Sun, giving us all an up close look at transits.
On June 5th, 2012, the NASA/JAXA Hinode mission captured these stunning views of the transit of Venus. Credit: JAXA/NASA/Lockheed Martin
Venus and Mercury have been observed transiting the Sun many times over the past few centuries. When these planets are seen passing between the Sun and the Earth, opportunities exist for some great viewing, not to mention serious research. And whereas Mercury makes transits with greater frequency (three times since 2000), a transit of Venus is something of a rare treat.
In June of 2012, Venus made its most recent transit – an event which will not happen again until 2117. Luckily, during this latest event, scientists made some very interesting observations which revealed X-ray and ultraviolet emissions coming from the dark side of Venus. This finding could tell us much about Venus’ magnetic environment, and also help in the study of exoplanets as well.
For the sake of their study (titled “X-raying the Dark Side of Venus“) the team of scientists – led by Masoud Afshari of the University of Palermo and the National Institute of Astrophysics (INAF) – examined data obtained by the x-ray telescope aboard the Hinode (Solar-B) mission, which had been used to observe the Sun and Venus during the 2012 transit.
Artist’s impression of the Hinode (Solar-B) spacecraft in orbit. Credit: NASA/GSFC/C. Meaney
In a previous study, scientists from the University of Palermo used this data to get truly accurate estimates of Venus’ diameter in the X-ray band. What they observed was that in the visible, UV, and soft X-ray bands, Venus’ optical radius (taking into account its atmosphere) was 80 km larger than its solid body radius. But when observing it in the extreme ultraviolet (EUV) and soft X-ray band, the radius increased by another 70 km.
To determine the cause of this, Afshari and his team combined updated information from Hinode’s x-ray telescope with data obtained by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory (SDO). From this, they concluded that the EUV and X-ray emissions were not the result of a fault within the telescope, and were in fact coming from the dark side of Venus itself.
They also compared the data to observations made by the Chandra X-ray Observatory of Venus in 2001 and again in 2006-7m which showed similar emissions coming from the sunlit side of Venus. In all cases, it seemed clear that Venus had unexplained source of non-visible light coming from its atmosphere, a phenomena which could not be chalked up to scattering caused by the instruments themselves.
Comparing all these observations, the team came up with an interesting conclusion. As they state in their study:
“The effect we are observing could be due to scattering or re-emission occurring in the shadow or wake of Venus. One possibility is due to the very long magnetotail of Venus, ablated by the solar wind and known to reach Earth’s orbit… The emission we observe would be the reemitted radiation integrated along the magnetotail.”
Collected images of Venus 2012 transit of the Sun, taken in June of 2012 by NASA’s Solar Dynamics Observatory (SDO). Credit: NASA/SDO, AIA
In other words, they postulate that the radiation observed emanating from Venus could be due to solar radiation interacting with Venus’ magnetic field and being scattered along its tail. This would explain why from various studies, the radiation appeared to be coming from Venus’ itself, thus extending and adding optical thickness to its atmosphere.
If true, this finding would not only help us to learn more about Venus’ magnetic environment and assist our exploration of the planet, it would also improve our understanding of exoplanets. For example, many Jupiter-sized planets have been observed orbiting close to their suns (i.e. “Hot Jupiters“). By studying their tails, astronomers may come to learn much about these planets’ magnetic fields (and whether or not they have one).
Afshari and his colleagues hope to conduct future studies to learn more about this phenomenon. And as more exoplanet-hunting missions (like TESS and the James Webb Telescope) get underway, these newfound observations of Venus will likely be put to good use – determining the magnetic environment of distant planets.
A composite image of the May 9, 2016 transit of Mercury across the face of the Sun, as seen by the Solar Dynamics Observatory. Credit: NASA's Goddard Space Flight Center/SDO/Genna Duberstein
On May 9, 2016, Mercury passed directly between the Sun and Earth. No one had a better view of the event than the space-based Solar Dynamics Observatory, as it had a completely unobstructed view of the entire seven-and-a-half-hour event! This composite image, above, of Mercury’s journey across the Sun was created with visible-light images from the Helioseismic and Magnetic Imager on SDO, and below is a wonderful video of the transit, as it includes views in several different wavelenths (and also some great soaring music sure to stir your soul).
Mercury transits of the Sun happen about 13 times each century, however the next one will occur in only about three and a half years, on November 11, 2019. But then it’s a long dry spell, as the following one won’t occur until November 13, 2032.
