NASA - National Aeronautics and Space Administration

When it comes to astronomy, the star nearest the Earth is somewhat of a paradox. Our sun is one object in the sky that everyone can see, but no one can look at. The sun is the brightest object in the sky. It's easy to find, but it's so bright that you can't look directly at it without harming your vision. But, there is a lot to be gained from studying the sun. Its closeness to Earth gives us a front-row view at how stars function. The sun's behavior has a direct impact on conditions on Earth. Fortunately, today we have the SOHO spacecraft. This spacecraft does what people can't -- it stares at the sun.

Image to left: This image of the sun was taken by the SOHO spacecraft. Credit: NASA

SOHO stands for Solar & Heliospheric Observatory. It is a very complex spacecraft that is designed to study the sun. NASA is not working on this project alone, though. The European Space Agency is also taking part in the project. It was launched by NASA in December 1995. Scientists from Europe and the United States are working together to study the data that SOHO sends back to Earth.

Image to right: The SOHO spacecraft keeps an eye on the sun 24 hours a day, 365 days a year. Credit: NASA

Most satellites orbit around the Earth, but SOHO is different. It orbits around the sun, like a planet or comet. Its orbit is located at a point where it feels the same pull of gravity from the sun as it does from the Earth. SOHO's orbit is about 1.5 million kilometers away from the Earth. From this location, SOHO has a non-stop view of the sun. This lets it keep a constant eye on the sun. This gives scientists a better idea of the how stars behave. It also gives them advanced warning of solar events that could affect Earth. Solar storms can interfere with electricity grids and communications on Earth. Plus, the advance warning can prevent astronauts from being exposed to the high doses of radiation that can be created by solar activity.

The SOHO spacecraft is made up of two main sections. The service module contains the power, guidance and communications systems. The payload module is where the science equipment is held. SOHO carries a dozen instruments to study the sun. Each one studies a different aspect of the sun. Telescopes look at the sun in a wide range of the light spectrum. Other instruments measure solar wind and the amount of radiation put off by the sun. There are also instruments to study the sun's atmosphere, or corona. Like Earth's atmosphere, the corona has its own weather. SOHO has observed explosions, shock waves, and tornado-like storms there. There are even tools to let scientists study what is happening beneath the surface of the sun.

SOHO's mission was only planned to last for three years. But the mission was so successful that NASA and ESA decided to extend it until at least 2007. This will let SOHO study an entire 11-year solar cycle. The mission hasn't been perfect though. Since its launch, the spacecraft has suffered a few problems that have interrupted its mission. Luckily, scientists have been able to fix these problems and return SOHO to its normal operations each time.

Image to left: This image of the sun shows the corona, the outer layer of the sun. Credit: NASA

SOHO has also made new discoveries about our star. Complex currents of gas flowing beneath the layers of the sun have been seen by SOHO. It has also discovered that the patterns of the sun's magnetic fields can go through rapid changes. So, what is SOHO's most important accomplishment? It holds the extraordinary record of nine years of almost constant solar observation.

SOHO is even helping people who can't see the sun to learn about it in a new book. The new book is titled "Touch the Sun." It lets students who are blind and visually impaired "see" images of the sun and solar activity. The images have raised textures over the pictures to allow students to feel the images. The book uses images taken by SOHO and other solar observatories.

The sun is a fascinating star. Even though humans have been watching it for thousands of years, it still finds new ways to surprise us. We still have a lot to learn about the sun, though. That's why SOHO is keeping an eye on it.


Related Resource

Get in Touch With the Sun's Wild Side
+ View site

Published by NASAexplores
David Hitt