This November all the planetary action centres around dawn. As the month begins, early risers will be treated to several stunning conjunctions featuring Venus, Mars, Jupiter and the Moon. And toward month’s end, the Moon occults Aldebaran, the brightest star in Taurus.
Venus, Mars and Jupiter in the morning
The month begins with events already underway. On November 1, Venus, Mars and Jupiter are all located in southern Leo, roughly 35° above the east-southeast horizon at the break of dawn. The three planets are easy to spot: Venus and Jupiter are by far the brightest star-like objects in the sky. Venus is the brighter of the two; Jupiter sits about 5° to its upper left, and Mars is the faint, rust-coloured “star” just one degree to the immediate left of dazzling Venus. In fact, though Venus currently shines 250 times brighter than Mars, the Red Planet is easy to see none-the-less.
But don’t get caught off guard: The planetary show unfolds rapidly during the first week of the month. Both Mars and the faster moving Venus are heading toward the horizon as they leave Jupiter and Leo behind: Venus overtakes Mars on the 2nd. By November 3, both planets have moved into Virgo and are in close conjunction, just ⅔ of-a-degree apart! Use binoculars to accentuate Mars’ ruddy hue against Venus’s dazzling white light.
Meanwhile, the Moon has been waiting in the wings and is about to enter the scene. At dawn on November 6, the waning lunar crescent will pass 3 degrees to the right of Jupiter… another spectacular pairing. See if you can spot the ghostly light of earthshine reflected on the otherwise dark part of the lunar face. The next morning, November 7, the Moon will pass less than 2 degrees to the right of Venus and 2 ½ degrees to the lower right of Mars, forming a spectacular celestial triangle. Set against the twilight glow of dawn, this conjunction promises one of the best astronomical photo-ops of the year: Try not to miss it!
The diminishing lunar crescent will continue to slide toward the horizon over the following days, until it completely vanishes in the Sun’s glare on November 10. A day or two before, look for a heavenly line consisting of (from top to bottom) Jupiter, Mars, Venus and the Moon. Following the 10th, and for the rest of the month, all three planets will remain visible with Venus rushing toward the horizon, leaving Mars behind. By month’s end, the planetary trio will be more-or-less evenly spread out above the southeast horizon.
The Moon occults Aldebaran
This year marks the start of a cycle of 49 lunar occultations of Aldebaran. Between 2015 and 2018, once each 27.3-day sidereal month, the Moon will pass in front of the V-shaped Hyades cluster occulting a few stars along the way. Since the Hyades contains hundreds of stars, it’s not surprising that several would be occulted; but the majority are faint telescopic objects invisible to the naked eye. There are some exceptions though, Aldebaran being one of them.
In reality, Aldebaran, a +0.8 magnitude orange giant representing the firey eye of Taurus, isn’t actually part of the Hyades: it sits about 65 light years away, roughly mid way between Earth and the more distant blue stars of the cluster. Aldebaran is also the brightest star that the Moon can occult—bright enough to see on the lunar limb, though binoculars certainly help to bring it out against the Moon’s glare. Here’s how to observe this month’s occultation…
On November 26, just before 5:39 A.M. EST, the Moon will begin moving in front of Aldebaran as viewed from southwestern Quebec. However, since the exact time is highly dependent on one’s precise location, it’s important to get a head start and not wait until the last possible minute to observe the event. Begin around 5:30… The Moon will be shining in the west, among the stars of the Hyades, nearly 30 degrees above the horizon, just to the right of Orion. Orange-hued Aldebaran will be near the upper left limb of the lunar orb, at the 10-o’clock position.
Since the Moon orbits Earth at about 1 km/sec from west to east, it moves a distance approximately equal to its own diameter each hour with respect to the background stars. By about 5:38, as seen from Montreal, the lunar limb will “contact” Aldebaran and then proceed to occult the star within a minute or so. Since the Moon’s centre will move along a path slightly above and to the right of Aldebaran, the star will not be occulted by the full lunar diameter and will therefore not remain hidden for a full hour; it will emerge on the opposite lunar limb about 50 minutes later, at around 6:30 A.M., just as dawn breaks. Meanwhile, the Hyades will have descended to within 10 degrees of the horizon, but the occultation will be over by then—about 40 minutes before sunrise—perfect timing!
Clear skies to all!