Welcome to Learning English, a daily 30-minute program from the Voice of America.

I'm Katie Weaver.

And I'm Mario Ritter Jr.

This program is designed for English learners.

So we speak a little slower slower and we use words and

phrases especially written for people learning English.

On today's program, Katie has a story about a scientific misunderstanding about a distant planet in our

own solar system. Jill Robbins and John Russell explain verb tenses on everyday grammar.

Then, Jill returns with Andrew Smith for the lesson of the day.

But first...

In 1781, German-born British astronomer William Herschel made Uranus the first planet discovered with a telescope.

But 243 years later, we still do not know much about this cold planet, the third largest in our solar system.

And some of what we thought we knew about it turns out to be

untrue. Much of the knowledge about Uranus was collected when NASA's robotic spacecraft, Voyager 2,

flew past it in 1986.

But scientists have since learned that the craft visited at a time of unusual conditions.

An intense solar wind event at the time led to misleading observations about Uranus, and especially its magnetic field.

The solar wind is a high-speed flow of charged particles coming from the sun.

The researchers took a second look at eight months of data from around the time of Voyager 2's visit,

and found that it flew near Uranus just a few days after the solar wind had reduced the planet's magnetosphere to about 20% of its usual size.

A magnetosphere is an area of space surrounding a planet that is controlled by the planet's magnetic field.

The magnetosphere protects the planet from solar and cosmic particle radiation.

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