Mercury is rising. Because Mercury never strays far from the Sun, skywatchers get only a few chances each year to see the planet. This week marks one of its brief appearances. This week, the innermost planet will jump out of the glare of the sun and become visible in the western sky at sunset. The view will improve each night this week as Mercury climbs higher in the sky. Mark these dates on your calendar: May 21st and May 22nd. On those nights Mercury and Venus will be in conjunction, about 1 degree apart. That's a little less than the width of a fingertip held at arm's length. Given clear skies, it'll be hard to miss Venus, as it is the third-brightest celestial body to light up the heavens, after the Sun and Moon, respectively. Luckily, Venus is our ticket to catching Mercury.