Satellites Orbit the Sun to Better Predict Solar Storms

The project, called STEREO for Solar TErrestrial RElations Observatory, began in 2006 when two satellites were launched into unique orbits around the sun, one slightly ahead of Earth’s orbit (where we will be in three months) and the other trailing slightly behind (where we were three months ago). The rocket used to launch the spacecraft wasn’t able to place them into the exact orbits, so NASA scientists used the moon’s gravity to move the satellites where they needed to be to capture images of all sides of the sun.

The sun is halfway through its star life

	At 4.6 billion years old, the sun is about halfway through its life as a star. Eventually, its gravity will overwhelm it and it will collapse.

The sun is a star that emits radiation in the form of heat and light which sustains life on Earth. Scientists estimate that the sun is about 4.6 billion years old, which puts it about halfway through its estimated total lifespan of 10 billion years.

All stars, including the sun, are held together by the force of their own gravity. Gravity continually tries to collapse the star, but the pressure caused by exploding gases and nuclear reactions within the star counteracts gravity and keeps the star intact. 

A star dies when it no longer produces enough nuclear reactions at its core to counteract the force of gravity. This process happens over billions of years as the star’s core gradually uses up the gases necessary to produce energy-emitting reactions. 

The most abundant gases in the sun's core are hydrogen and helium. Through the process of nuclear fusion, the hydrogen particles are converted to helium at very high heat, producing energy. The core temperature of the sun is about 27 million degrees Fahrenheit, and the pressure at the sun’s core is 340 billion times the pressure on Earth at sea level. That pressure and heat make ideal conditions for intense nuclear reactions to take place that provide heat and light to Earth.

Magnetic storms on the sun could damage electrical grids

	The Northern and Southern lights, seen most often near Earth's two poles, are a result of solar magnetic activity.

The sun’s powerful magnetic fields go through phases, some of which can affect life on Earth. For example, coronal mass ejections, or CMEs, often shoot matter and electromagnetic radiation in Earth’s direction as a result of shifts in the sun’s magnetic fields. 

Although CMEs can’t physically be seen or felt by humans on Earth, they can cause serious damage to satellites and other objects in space and can even give astronauts and airline passengers high doses of radiation. They also can cause electrical failures on Earth due to their intense blast of magnetic force. Because many of today’s power systems operate at top capacity, some scientists believe that a large CME storm could damage or snap power lines across a large area by overloading the system.

The sun’s magnetic activity is also responsible for the aurora borealis, or northern lights phenomenon. (In the Southern hemisphere, the same phenomenon is called aurora australis.) In 1859, an enormous CME caused such massive magnetic fluctuations in the Earth's magnetosphere -- the magnetic field surrounding the planet -- that people living as far south as Cuba witnessed the northern lights phenomenon. Compasses and telegraph systems also failed as a result of that CME storm.

How will STEREO help?

	This image shows a CME. or a coronal mass ejection, that shoots electromagnetic radiation out from the sun.

Before they made a complete picture of the sun, scientists could only guess when CMEs and other solar storms might happen. Only one side of the sun is ever visible from Earth, and it takes 12 days for the other side to come into view. Now, instead of waiting to see what the “far side of the sun” looks like, scientists can analyze the sun’s surface in real time to try to pinpoint the timing of a CME.

This is especially important now because many scientists believe the sun is entering a phase of especially turbulent magnetic activity called solar max. The sun goes through phases that last about 11 years, during which the probability of CMEs and other solar activities is either heightened or lessened. The sun is currently finishing a period of lessened solar activity and entering a period when CMEs and other “solar weather” events are more likely. 

Here on Earth, scientists also are looking for ways to lessen the effects of CMEs. These methods include building a smarter power grid that won’t overload as easily, and adjusting long airline routes so they don’t fly as close to the poles where the most magnetic activity and radiation occurs.