Did you know we’re watching the Sun 24/7 from space?
We use a whole
fleet of satellites to monitor the Sun and its influences on the solar
system. One of those is the Solar Dynamics
Observatory. It’s been in space for eight years, keeping an eye on the Sun
almost every moment of every day. Launched on Feb. 11, 2010, this satellite
(also known as SDO) was originally designed for a two-year mission, but it’s
still collecting data to this day — and one of our best ways to keep an eye on
To celebrate another year of SDO, we’re sharing some of our
favorite solar views that the spacecraft sent back to Earth in 2017.
March: A long spotless
For 15 days starting on March 7, SDO
saw the yolk-like spotless Sun in visible light.
The Sun goes through a natural 11-year cycle of activity
marked by two extremes: solar maximum and solar minimum. Sunspots are dark
regions of complex magnetic activity on the Sun’s surface, and the number of
sunspots at any given time is used as an index of solar activity.
- Solar maximum = intense solar activity and more
- Solar minimum = less solar activity and fewer
This March 2017 period was the longest stretch of spotlessness since the last solar minimum in April 2010 – a sure sign that the solar cycle is marching on toward the next minimum, which scientists expect in 2019-2020. For comparison, the images on the left are from Feb. 2014 – during the last solar maximum – and show a much spottier Sun.
June: Energized active
A pair of relatively small but frenetic
active regions – areas of intense and complex magnetic fields – rotated
into SDO’s view May 31 – June 2, while spouting off numerous small flares and
sweeping loops of plasma. The dynamic regions were easily the most remarkable
areas on the Sun during this 42-hour period.
July: Two weeks in the
life of a sunspot
On July 5, SDO watched an active region rotate into view on
the Sun. The satellite continued
to track the region as it grew and eventually rotated across the Sun and
out of view on July 17.
With their complex magnetic fields, sunspots are often the
source of interesting solar activity: During its 13-day trip across the face of
the Sun, the active region — dubbed AR12665 — put on a show for our Sun-watching
satellites, producing several solar flares, a coronal mass ejection and a solar
energetic particle event.
August: An eclipse in
While millions of people in North America experienced a
total solar eclipse on Aug. 21, SDO
saw a partial eclipse from space. SDO actually sees several
a year from its perspective – but an eclipse on the ground doesn’t necessarily
mean that SDO will see anything out of the ordinary. Even on Aug. 21, SDO saw
only 14 percent of the Sun blocked by the Moon, while most US residents saw 60
percent blockage or more.
September: A spate of
In September 2017, SDO saw a
spate of solar activity, with the Sun emitting 31 notable flares and
releasing several powerful coronal mass ejections between Sept. 6-10. Solar
flares are powerful bursts of radiation, while coronal mass ejections are
massive clouds of solar material and magnetic fields that erupt from the Sun at
One of the flares imaged by SDO on Sept. 6 was classified as
X9.3 – clocking in at the most powerful flare of the current solar cycle. The
current cycle began in December 2008 and is now decreasing in intensity,
heading toward solar minimum. During solar minimum, such eruptions on the Sun
are increasingly rare, but history has shown that they can nonetheless be
September: A trio of
distinct solar active regions with towering arches rotated into SDO’s view
over a three-day period from Sept. 24-26. Charged particles spinning along the
ever-changing magnetic field lines above the active regions trace out the
magnetic field in extreme ultraviolet light, a type of light that is typically
invisible to our eyes, but is colorized here in gold. To give some sense of
scale, the largest arches are many times the size of Earth.
December: A curling
SDO saw a small prominence arch up
and send streams of solar material curling back into the Sun over a 30-hour
period on Dec. 13-14. Prominences are relatively cool strands of solar material
tethered above the Sun’s surface by magnetic fields.
An elongated coronal hole — the darker area near the center
of the Sun’s disk — looked
something like a question mark when seen in extreme ultraviolet light by SDO
on Dec. 21-22. Coronal holes are magnetically open areas on the Sun that
allow high-speed solar wind to gush out into space. They appear as dark areas
when seen in certain wavelengths of extreme ultraviolet light.
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