2015-01-19 17:49:07 UT: 100 million SDO/AIA images on orbit

The Atmospheric Imaging Assembly (AIA) is a prime instrument on NASA's Solar Dynamics Observatory (launched on February 11, 2010; observing the Sun in science mode since May 1, 2010). AIA comprises four telescopes that take 16-megapixel images of the Sun in four channels simultaneously, alternating between two complementary sets of channels, and thereby providing eight distinct views every 12 seconds. It sees our neighboring star in the light of ionized helium, iron, and carbon, and in the ultraviolet and visible "white light" continuum. AIA's channels include He II (304Å), Fe XVIII (94Å), C IV (1600Å), white light (4500Å), Fe IX (171Å), Fe XIV (211Å), Fe XII/XXIV (193Å), Fe XI (335Å), Fe XX/XXIII (131Å). For more information about AIA, visit the AIA home page.

AIA's images add over a petabyte of data to the SDO mission archive each year. It is a unique instrument, observing everything in the solar atmosphere, all the time (with interruptions only when calibrations need to be taken or when Earth or Moon briefly obstruct AIA's view). The results are streams of images, movies, scientific studies, and media attention.

On Monday, January 19, 2015, around 17:50 UT, AIA took its 100-millionth on-orbit image of the Sun (and its basic 'level-0' data archive then exceeded 100 billion MB). For the NASA "news" click here.

Below are links to sites with more AIA information and images, and a select set of highlights from its 5-year mission to explore the Sun, its explosive nature, and the consequences throughout the solar system, including all forms of space weather.

SDO is frequently in the news:

A few web links to AIA images and scientific discoveries:

  1. AIA's home page for background information and many links to what it does, how to access and use its observations, and what it discovered.
  2. SunToday for images and daily summary movies of the Sun on any day since April 16, 2011.
  3. A list of month-long AIA movies.
  4. A compilation of highest-rated solar flares, eruptions, and active regions.
  5. A listing of AIA-related scientific publications from the NASA/ADS search engine.
  6. SDO at NASA/GSFC.


100,000,000: The 100-millionth on-orbit exposure by AIA (left) in the Fe XII 193Å channel, and (right) embedded in a 3-color set (red, green, and blue represent 211Å, 193Å, and 171Å, repectively).

SDO & AIA: An artist's conception of the Solar Dynamics Observatory (by NASA) with the four parallel AIA telescopes visible on top.

Colorful complement: AIA images the Sun in 10 different channels (as shown here on 21 October 2010), going from the solar surface (in 'white light') to the extreme ultraviolet emitted by the transparent corona (from 171Å to 131Å, covering temperatures from some 5700 K to over ten million K.

Spectacular eruption: A massive explosion rocked the Sun on 7 June 2011, as a large eruption lifted an enormous amount of cool, dark material into the hotter corona. The event is shown here in a combination of three false-color images seen at 06:52:00 UT, with 211Å, 193Å, and 171Å represented in red, green, and blue respectively. A full-Sun image taken a little earlier at 06:35:36 UT, also showing the associated flare is here). Most of the cooler material eventually fell back into the Sun, heating up to a million degrees or more from the gravitational energy of the fall. Scientists studying the falling material concluded that we were seeing a small-scale version of what happens as stars form and collect gases by their gravity. AIA allowed us to study a process involved in stellar creation in greater detail than could be seen anywhere else in the universe. (See also this Science paper.)

One of the largest sunspot groups: A group of sunspots, including the largest sunspot seen in the last 25 years, appeared on the Sun on October 22, 2014. This large feature was visible at the solar surface, or photosphere, from Earth without a telescope. Above the sunspot group, a brightly glowing solar corona (observed in AIA's 193Å channel, showing the glow of gases at temperatures around 1.5 million Kelvin) is shaped by the magnetic field that makes the sunspots.

Coronal loops over a sunspot group: When AIA images are sharpened a bit, such as this AIA 171Å channel image, the magnetic field can be readily visualized through the bright, thin strands that are called "coronal loops". Loops are shown here in a blended overlay with the magnetic field as measured with SDO's HMI underneath. Blue and yellow represent the opposite polarities of the magnetic field. The combined images were taken on 24 October 2014, 23:50:37 UT. Another such image can be found here as published on the Astronomy Picture of the Day web site.

Flare and eruption: This image combines three channels (or colors) observed by AIA, showing a flare (in red) and associated eruption (in blue) that occurred on 29 August 2014. We use false colors to represent the extreme ultraviolet images that AIA captures. The red color shows the AIA 131Å channel that is sensitive to hot gases, above 10 million degrees. The green color - representing the 171Å channel - has its peak sensitivity around one million degrees. The blue color shows the 304Å channel, which is sensitive to very much cooler gases, with temperatures around 20,000 Kelvin.

Great sensitivity: AIA enables us to observe the corona at high resolution and at multiple "colors", which represent temperatures of the glowing gas in the corona. In the image on the left, blue shows material about 1 million degrees, green about 1.5 million, and red is 2 million degrees or even more. All temperatures occur along our line of sight, with different temperatures at different depths in the corona. AIA is also very precise and very sensitive to small changes; so, in the image on the right, we removed everything that was not changing from one exposure to the next, showing only where the ongoing solar flare and coronal mass ejection (explosion) deformed the coronal gas and magnetic field. In the case of this eruption (on 7 March 2012, around 01:06 UT) we see that the eruption affects over half the Sun (with a diameter of almost a million miles) and reaches into the corona up the the very edges of AIA's field of view. These deformations, including many wave phenomena, tell us more about the Sun's ever-changing corona: see, for example, this review.

Running waves: AIA's sensitivity has enabled the discovery of a new, fast-moving type of waves that shake the Sun's corona. The image on the left (taken on 30 May 2011) shows an active region where a moderate flare lights up a ridge. The image on the right shows a difference between this exposure and a previous one, highlighting only what has changed between the two times. We see a wave appear in the difference, with alternating bright and dark bands running towards the upper left corner. Only AIA's rapid cadence could reveal that this type of wave can run at speeds exceeding 2000 km/s. (see, for example, this study)

Eruptions: AIA imaged this eruption on 11 February 2011, revealing that its gases had a wide range of temperatures existing side by side, from a few tens of thousands of Kelvin to at least ten million Kelvin.

Death of a comet: On 6 July 2011, AIA observed, for the first time ever, a comet plunging into the Sun's corona. The comet (probably just 10 to 50 meters in diameter at first; compared to the solar diameter of 1.4 million kilometers) was hardly visible against the glow of the background corona (moving through the dashed box), but image enhancements (shown as insets) revealed the irregularly glowing tail of the dying comet. (see this Science paper)

Venus transit: On June 5 & 6, 2012, AIA observed a rare transit of Venus. We see Venus cross in front of the Sun twice, eight years apart, about every 100 years and the next such transit will be 10 & 11 December, 2117. This image (taken in the 171Å channel, showing the solar coronal glow from gases at temperatures near 1 million Kelvin) is a composite of slices, put together to show the track of Venus across the Sun. (Courtesy NASA/GSFC visualization studio). This observation, by the way, helped us learn not only about the Sun and Venus but about our satellite instrument, enabling us to determine the scale of our images with remarkable accuracy (0.60000 +/- 0.00007 arcsec/pixel).

A partial eclipse: SDO orbits the Earth in such a way that its view of the Sun is almost always unobstructed; but, a few times a year, the Moon gets in the way. This image (taken on 22 November 2014) shows the Moon's disk partially blocking our view of the solar corona (in the 193Å channel). If you look carefully, you can see that the edge of the Moon is not a perfect circle: AIA's image quality allows you to spot lunar mountains along the edge.

Colorful Sun: The power of AIA lies in its ability to image all of the solar atmosphere all the time. This composite image (made by NASA/GSFC's visualization studio) reveals some of the potential of that: the solar atmosphere has many different temperatures side by side, shaped by the magnetic field, and AIA's filters allow us to pick apart the glow from the solar atmosphere to reveal (shown in false color) that each temperature shows a completely different view. Only when combined, do all of these images show us the solar outer atmosphere in all its detail. For another type of such a colorful image, see Astronomy Picture of the Day.

Hunting for the magnetic field: All of the Sun's variability (including flares and coronal mass ejections that drive space weather) are powered by the magnetic field. We cannot directly observe that but we can compute it from observations by AIA's sister instrument, HMI. This overlay shows how computed magnetic field lines resemble the shapes in the Sun's atmosphere that are created by glowing gases that are tied to the elusive magnetic field.

Comet Lovejoy as solar probe: On 15 December 2011, comet Lovejoy raced through the solar corona. AIA observed it coming into and leaving the Sun's corona. The image on the left shows the comet faintly high above the solar edge (center-left). The image on the right is a computer generated model of the solar magnetic field and the trajectory of the comet, showing the magnetic field lines that it touched on its path. The AIA images showed gases evaporating off the comet, briefly outlining the magnetic field, and enabling scientists to better understand the Sun's outer atmosphere. (see this Science paper, or this paper in Physics Today)

Looking through the Earth's atmosphere: SDO's orbit is designed to have an uninterrupted view of the Sun most of the time but there are two intervals each year when the Earth briefly moves in the way. In this image, AIA's view is partially blocked by the Earth (left), partially unblocked way above Earth's atmosphere (right), with a zone in between where the EUV light that makes AIA's images is mostly absorbed by the Earth's atmosphere.

Intiating a coronal mass ejection: AIA imaged the early phase of a coronal mass ejection on 21 October 2010, revealing that its gases had a wide range of temperatures existing side by side, from some tens of thousands of Kelvin to well over a million Kelvin.

Image collage: Shaped to resemble one of the very first images taken by AIA after SDO's launch, this large collage (the original is 11,929x12,000 pixels) presents a sampling of the many views of the Sun collected by AIA.

Solar coverage: SDO/AIA images and scientific discoveries have resulted in many "cover" images of journals and magazines. This image shows a small selection of covers placed on a 3-color composite of images taken at the time of the 100,000,000-th image (which is embedded in the green channel of this image); a 12000x12000 pixel version (42MB JPEG) and a 40in x 40in (300dpi; 375MB pdf) are available.
Last modified: Wed Feb 4 10:56:45 PST 2015