As we head toward the final days of November, skywatchers spy pretty planetary and lunar pairings and a mythical hunter, while anxiously waiting to learn of the fate of comet ISON as it rounds the sun.
Moon and Regulus. In the hours before sunrise on Tuesday, November 26, look for the last quarter moon to fill the southeast sky. Perched to its upper right is the bright blue-white star Regulus, the brightest member of the constellation Leo (the lion).
Despite being 78 light years away, Regulus ranks as the 21st brightest star in the entire sky. A true stellar giant, it weighs in with about four times the mass of our sun and has surface temperatures that are roughly double, which means it is burning its gas fuel at a fast and furious pace.
So while its estimated age is only a few hundred million years old, it is probably already becoming elderly and will likely die before it reaches a billion years in age. That may sound like an incredibly long time, but compare it to our own sun’s lifetime, which is estimated to be as much as 10 billion years long.
Mercury and Saturn. As dawn approaches on Tuesday, November 26, you can glimpse two naked-eye planets, Mercury and Saturn very low in the southeast sky from around the globe.
The pair of worlds will appear separated by only one degree, equal to the width of two full moons side by side in the sky. Easily fitting into the view of binoculars and telescopes, Mercury will appear hanging below the brighter Saturn.
And that faint little star to the planetary pair’s upper right? That is 77 light-year distant Zubernelgenubi, the lead star in the zodiacal constellation Libra (the scales). It’s name is derived from Arabic meaning the “southern claw of the scorpion,” referring to ancient Babylonian times when astronomers considered this star part of the Scorpius constellation.
Moon and Mars. In the early morning hours of Wednesday, November 27, the waning crescent moon forms a stunning pair with the ruddy colored Mars. The celestial duo will appear only about five degrees apart, equal to the span of your three middle fingers at arm’s length.
It’s kind of amazing to think that this orange point of light is actually another world some 254 million kilometers away, and that both NASA and India have orbiters now heading towards the red planet.
ISON Perihelion. On Thursday, November 28, comet ISON makes it closest approach to the sun (perihelion). While skywatchers wait anxiously to see if the icy visitor survives its scorching encounter—passing less than 1.1 million kilometers above the sun’s surface—NASA’s solar probes are watching all the action from space. So while the next few days Comet ISON is too close to the glare of the sun to see, STEREO-A spacecraft is continually monitoring it along with Earth, Mercury, and even Comet Encke.
Moon and Planet Line-up. Set your alarms early for Sunday, December 1, when the razor-thin crescent moon appears sandwiched in between Mercury and Saturn. The dawn sky show will play out in the very low southeast and is best seen from a vantage point that has no obstruction towards the horizon.
Winter Orion Rises. By mid-evening on Sunday, December 1, look towards the southeast sky for the winter season’s most celebrated constellation—Orion, the hunter. It’s stellar pattern is one of the easiest to recognize for novice skywatchers thanks to the perfect alignment of three equally bright stars in a row, which marks the belt of Orion. Meanwhile, to the upper left of the belt, is the bright orange star Betelgeuse, which marks the left shoulder of the legendary hunter. Rigel marks the right knee of the stellar character below right of the trio.