Today Earth passes between the sun and Jupiter, placing Jupiter opposite the sun in our sky. Astronomers call this event an opposition of Jupiter. The 2011 opposition is Jupiter’s closest until 2022.

The giant planet is now lighting up this late October night from dusk until dawn. It will remain close and bright throughout November. Although it’ll dim slightly, more people will notice Jupiter next month, because it will appear in the east already as the sun is setting in the west.

Why is Jupiter closer at some oppositions than others? It’s because Jupiter’s orbit, like Earth’s orbit, isn’t perfectly round. This year, in 2011, Jupiter happens to swing to perihelion — its closest point to the sun during its 12-year orbit. At perihelion, Jupiter is nearly 50 million miles closer to the sun than when it’s at aphelion — its most distant point. That’s why Jupiter is closer to us than usual at this year’s opposition. In fact, Jupiter won’t come this close to Earth again until the year 2022.

Jupiter comes to opposition every 13 months or so, as Earth takes this long to travel once around the sun relative to Jupiter. Jupiter’s closest approach to Earth for the year always falls on or near this planet’s opposition date. In 2011, Jupiter came nearest to Earth on October 27, at 19 hours Universal Time (2 p.m. Central Daylight Time). Then Jupiter was only 369 million miles away.

However, Earth flies in between the sun and Jupiter tomorrow, on October 29 at 2:00 Universal Time. That is 9:00 p.m. Central Daylight Time tonight, on October 28. When it is opposite the sun, astronomers say that Jupiter is in opposition. The king planet now rises in the east at sunset, and sets in the west at sunrise. At midnight, Jupiter climbs highest in the sky.

Whereas Jupiter shines all night long tonight, you'll have to catch the moon, Venus and Antares shortly after sunset

And, because it’s opposite the sun around now, you can see Jupiter at any time of night. For example — as today’s chart shows — you can see it in the south at midnight tonight, when the sun is below your feet. At dawn tomorrow, you’ll see Jupiter low in your western sky. At opposition, Jupiter shines at its brightest in our sky.

You would need at least 80 Jupiters — rolled into a ball — to be hot enough inside for thermonuclear reactions to ignite. In other words, Jupiter is not massive enough to shine as stars do. But Jupiter is the largest planet in our solar system. So when the sun goes down on this late October night, you might — if you’re fanciful enough — imagine bright Jupiter as a tiny sun all night long.

Jupiter’s greatest distance from us will come when Jupiter is behind the sun from Earth in May 2012. Let’s see … closest in late October … farthest a bit more than six months later in middle May 2012. You might see that Jupiter’s distance from us, as well as its location in our sky, is being driven primarily by Earth’s year-long orbit around the sun.

That’s because Earth travels around the sun in an orbit that’s much closer to the sun than Jupiter’s far-out orbit. Our orbit is smaller, and we move faster in orbit than does the solar system’s king planet. Earth travels at a speed of about 18 miles per second in orbit, in contrast to about 8 miles per second for Jupiter.

Be sure to look for Jupiter tonight, in front of the constellation Aries, a beautiful site to behold on this the night of Jupiter’s opposition. And remember, this opposition of Jupiter counts as extra special — Earth’s closest encounter with Jupiter until the year 2022!