SolarDynamicsObservatory - Blog Posts

A Year on the Sun Through Our Satellite’s Eyes

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 our star.

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 stretch

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 sunspots

Solar minimum = less solar activity and fewer sunspots

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 regions

 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 space

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 lunar transits 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 solar activity

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 incredible speeds.

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 intense.

September: A trio of tempests

Three 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 prominence

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.

 December: Solar question mark

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.

For all the latest on the Solar Dynamics Observatory, visit nasa.gov/sdo. Keep up with the latest on the Sun on Twitter @NASASun or at facebook.com/NASASunScience.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com 

The Moon Just Photobombed NASA’s Solar Dynamics Observatory

On May 25, 2017, the moon photobombed one of our sun-watching satellites by passing directly between the satellite and the sun.

The Solar Dynamics Observatory, or SDO, orbits Earth and watches the sun nearly 24/7 — except when another body, like the moon, gets in the way. These lunar photobombs are called transits, the generic term for when any celestial body passes in front of another.

Transits are one way we detect distant worlds. When a planet in another star system passes in front of its host star, it blocks some of the star’s light so the star appears slightly dimmer. By monitoring changes in a star’s light over time, scientists can deduce the presence of a planet, and even determine what its atmosphere is like. This method has been used to discover thousands of planets, including the TRAPPIST-1 planets.

SDO sees lunar transits about twice a year, and this one lasted about an hour with the moon covering about 89 percent of the sun at the peak of its journey across the sun’s face.

When they’re seen from Earth, we call lunar transits by another name: eclipses.

Solar eclipses are just a special kind of transit where the moon blocks all or part of our view of the sun. Since SDO’s view of the sun was only partially blocked, it saw a partial eclipse. Later this year, on Aug. 21, a total eclipse will be observable from the ground: The moon will completely block the sun’s face in some parts of the US, creating a total solar eclipse on a 70-mile-wide stretch of land, called the path of totality, that runs from Oregon to South Carolina.

Throughout the rest of North America — and even in parts of South America, Africa, Europe and Asia — the moon will partially obscure the sun, creating a partial eclipse. SDO will also witness this partial eclipse.

Total solar eclipses are incredible, cosmic coincidences: The sun is about 400 times wider than the moon, but it also happens to be 400 times farther away, so the sun and moon appear to be the same size in our sky. This allows the moon to completely block the sun when they line up just right.

Within the path of totality, the moon completely obscures the sun’s bright face, revealing the comparatively faint corona — the sun’s pearly-white outer atmosphere.

It’s essential to observe eye safety during an eclipse. You must use proper eclipse glasses or an indirect viewing method when any part of the sun’s surface is exposed, whether during the partial phases of an eclipse, or just on a regular day. If you’re in the path of totality, you may look at  the eclipse ONLY during the brief moments of totality.

A total solar eclipse is one of nature’s most awe-inspiring sights, so make your plans now for August 21! You’ll also be able to see the eclipse cross the country that day through the eyes of NASA – including views of the partial eclipse from SDO – on NASA TV and at nasa.gov.

Learn more about the August eclipse — including where, when, and how to safely see it — at eclipse2017.nasa.gov and follow along on Twitter @NASASun.