Many of us are feeling the full force of the sun this month — long days, morning glare and heat, heat, heat! You might think that’s because Earth is closer to the sun during northern summer but just the opposite is true. Earth reaches aphelion in 2020 — its most distance point from the sun — at 6:34 a.m. CDT tomorrow morning, July 4. The planet is a little more than 3 million miles farther from the sun right now compared to last Jan. 5th.
Seasonal heat has little to do with distance. Instead, the tilt of Earth’s axis inspires the seasons. Cycles abound in our solar system including the solar cycle that tracks the sun’s slow rise in activity like flares, sunspots and energetic outbursts. After reaching a peak the sun’s settles back down to minimum again when it’s can often go “spotless” for weeks or months at a time. A full cycle from minimum to minimum takes about 11 years.
The most recent solar cycle, dubbed Cycle 24, began with a December 2008 minimum, peaked in April 2014 and bottomed out this past spring. We’re currently still holding at minimum though sunspots of Cycle 25 have been showing up over the past few months. Minimum usually means very few chances to see the aurora at mid-latitudes in case you were wondering why that well has been so dry this year.
From its orbit in space around the Earth, SDO has made 425 million high-resolution images of the Sun, amassing 20 million gigabytes of data over the past 10 years.
As of June 2020 NASA’s orbiting Solar Dynamics Observatory (SDO) has been watching the sun from space for over a decade. To celebrate this achievement NASA Goddard recently gathered 10 years of images of the sun taken in deep ultraviolet light by SDO turned them into a time-lapse movie about an hour long. Each second of the video represents one day.
It’s fun to watch the slow rises from minimum to maximum (spring 2014) and subsequent decline to minimum again. Use the slider to sample parts of the video if you don’t feel like sitting through the whole thing. Ultraviolet light reviews the sun’s incredible magnetic texture. The bright, yellow loops you see are lines of magnetism extending outward from sunspots and sunspot groups that reverberate with powerful magnetic energy. Sometimes that energy gets transformed into flares that can blast clouds of particles into space. Arriving at Earth they can instigate displays of the northern and southern lights.
Dealing with the full energy of a star just 93 million miles away takes work. Eventually we reach the end of day when the sun sets. Twilight begins and we can stretch out into the night.