We Just Can’t Get Enough Sun

After hunkering down to survive D.C.’s “snowpocalypse” this past week, I was definitely ready for some sun.


—Image courtesy United Launch Alliance/Pat Corkery via NASA

Luckily, NASA obliged me with Thursday’s launch of their latest space probe, the Solar Dynamics Observatory.

The SDO is a semi-autonomous craft that will orbit Earth, taking continuous observations of the sun in an attempt to better understand how and why our star is so stormy.

The overall goal is to someday be able to predict sun storms the way we predict weather on Earth, so we can be prepared for solar flares and other events that might knock out electrical stuff or fry satellites.

NASA, which has definitely shown eagerness to embrace social media and new technologies, revealed at a press briefing today that the SDO will stream data into an app for the iPhone, called 3D Sun.

It’s a cool little widget that sends you the probe’s most recent pic of the sun overlaid with current features such as axial tilt and sunspots, along with a news feed on what the probe has seen lately.

But wait. The 3D Sun app has been available since last year, streaming data from another NASA sun probe, STEREO.

And don’t we also have TIMED, SOHO, RHESSI, TRACE, and Hinode—all currently orbiting sun probes that NASA has a hand in operating?

Just how much sun can one space agency handle?

Of course, even if the target is the same, every mission is unique—each of these fine craft is equipped with instruments that study different aspects of the sun-Earth interaction.

And I can see why the sun would be such a hot topic for NASA.

Clearly, if we ever hope to understand stars that are light-years away—and how those stars might influence other planets—we’d better get a handle on what’s going on with the closest star to Earth.

Not to mention that whatever we learn about the sun has a direct impact on life on Earth right now, from the strength of aurorae to long-term climate events.

So let’s take stock of what all those previous sun probes have been doing, and what the SDO now brings to the party, with a sunny little time line:

December 1995: SOHO


Comet Bradfield, as seen by SOHO in 2004

—Image courtesy NASA/ESA

The Solar and Heliospheric Observatory is a joint project between NASA and the European Space Agency with mission control at Goddard Space Flight Center in Maryland. Its suite of 12 instruments was designed to answer three main questions: 1) what are the structure and workings of the sun’s deep interior; 2) why does the sun’s atmosphere have a bright upper layer, or corona, and why is it unexpectedly hot; and 3) what drives the solar wind?

SOHO also has a proven track record spotting previously unseen comets—it’s found several hundred so far, and even witnessed one get vaporized not too long ago.

April 1998: TRACE


—Image courtesy NASA

The Transition Region and Coronal Explorer was designed as a companion to SOHO, a smaller satellite with the targeted mission of watching the sun’s upper atmosphere up close and looking for connections between plasma structures (coronal holes and coronal mass ejections) and the sun’s magnetic field.

It’s kind of like having a biologist looking at an animal’s skin and teeth under a microscope while another watches the same animal’s behavior in the wild: Little changes on the surface can have big impacts.

December 2001: TIMED


—Image courtesy NASA

Meanwhile, the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite is hard at work studying how the sun affects the upper reaches of Earth’s atmosphere, a region believed to be a gateway for solar energy reaching our planet.

Its four instruments are collecting data on chemical and temperature changes in Earth’s upper atmosphere, energy flow in and out, and the speed and direction of winds.

February 2002: RHESSI


—Image courtesy NASA

The Reuven Ramaty High Energy Solar Spectroscopic Imager is another SOHO companion, this one focused on the particle physics of solar flares. The instrument uses high-resolution imaging and spectroscopy (how different atoms emit and absorb light) to find out how high-energy particles get accelerated in the flares.

Aside from adding to sun science, this probe is also looking at high-energy sources elsewhere in the universe, such as the Crab Nebula and gamma-ray bursts.

September 2006: Hinode


—Image courtesy NASA/MSFC

Meaning “sunrise” in Japanese, Hinode (hee-NO-day) is primarily a JAXA mission that has support from NASA and the U.K. Launched just over ten years after SOHO, Hinode was billed at the time as the “next generation” of solar observatories. It carries optical, x-ray, and extreme ultraviolet imagers all trained on figuring out how energy is made and moved from the lower atmosphere to the corona. The probe also watches for clues to how energy stored in the sun’s magnetic field gets released, and how that influences the heliosphere.

Technically, the sun’s atmosphere encompasses our whole solar system, since the sun sends charged particles—solar wind—streaming in all directions for millions of miles. The heliosphere is the entirety of the sun’s upper atmosphere, which means one of Hinode’s jobs is looking at how magnetic changes on the sun’s surface ultimately affect, for example, Saturn.

October 2006: STEREO


Break out the 3D glasses…

—Image courtesy NASA

Perhaps the most aptly named solar probe, STEREO is actually two spacecraft positioned to offer images of the sun, that’s right, in stereo. Just as two eyes gives us depth perception, STEREO’s twin craft give astronomers their first-ever 3D pictures of the sun and its storms.

STEREO specifically looks at coronal mass ejections, eruptions of energy from the sun’s surface that are so powerful they can blow up to ten billion tons of solar atmosphere out into space. Coronal mass ejections can trigger solar storms, which carry significant risks to satellites, spacewalking astronauts, and even power grids on Earth.

February 2010: SDO


—Image courtesy NASA

And so finally we come to SDO. The newest probe’s mission is to look at how solar activity starts and evolves, based on changes in the sun’s magnetic field. Its three instruments will take oodles of data simultaneously, offering some of the highest resolution pictures of surface action on the sun.

Although at first blush SDO seems to do much of what SOHO and STEREO have been doing, the technology is updated and the amount of data collected will be ginormous. By way of comparison, NASA notes that SOHO takes one image every 12 minutes. STEREO takes one image every 3 minutes. But SDO will take one image every 0.10 of a second. The instrument also has the specific goal of finding out why the sun has an 11-year cycle of activity.

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