Go outside tonight and you may get your best view of the planet Mars in years.
Tonight marks the "opposition" of Mars, when the Earth passes between Mars and the sun, bringing the two planets toward their closest approach within their orbits — something that only happens every 26 months.
That will make Mars look like an unusually bright orange dot in the sky — almost 10 times brighter than the brightest stars, NASA says.
Mars should be easy for you to spot with the naked eye even in the city. If you have a backyard telescope, you may even be able to see details such as one of the planet's polar ice caps, the U.S. space agency says.
The relative closeness of Mars will make it appear bigger than usual. But the geometry of Mars relative to the sun also makes a difference, reports the astronomy news site EarthSky: "Mars's disk not only covers more area of sky, but Mars's surface reflects the light of the sun most directly back to Earth."
Tonight's celestial event is called "opposition" because the alignment of Earth between Mars and the sun will make them appear at opposites sides of the sky.
This diagram shows the slightly elliptical orbits of Earth (blue) and Mars, with the positions of Mars (red) at its biannual oppositions marked. You can see that some oppositions are closer than others. (Duk Han Lee/CBC; Sydney Observatory)
If the two planets had perfectly circular orbits around the sun, then they would be at their closest to each other tonight. But because the orbits are slightly elliptical, they will be closest – just 92 million kilometres apart — on the night of April 14.
On that night, NASA ScienceCast says "the full moon will be gliding by the Red Planet in the constellation Virgo providing a can't-miss landmark in the midnight sky."
But that's not all — the full moon is expected to turn blood red during a total lunar eclipse visible throughout the western hemisphere.
Mars's slightly elliptical orbit, which brings it closer to the sun at some times of its year than others, is also the reason why it comes closer to Earth during some oppositions than others. This year's Mars opposition is the closest since December 2007.
Because Mars and the Earth orbit at different speeds when they aren't in opposition, they can be quite far apart — sometimes even on opposite sides of the sun.
If you miss Mars tonight or on April 14, don't worry – the Red Planet will appear relatively big and bright all month long.
The next Mars opposition will take place in May 2016.
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