But this is just a prelude to the main event March 4.That evening, our satellite occults the 1st-magnitude star Aldebaran in Taurus the Bull. Observers across most of the United States, except for those within shouting distance of the Canadian border or in the northern half of New York and New England, can see this event. With Aldebaran bright and the Moon only about 45 percent lit, binoculars will deliver nice views. Of course, a telescope’s more-stable platform yields the best looks.
The occultation begins after 11 p.m. EST on the East Coast and after 7 p.m. PST on the West Coast. Exact times depend on your location (visit www.lunar-occultations.com/iota/iotandx to get accurate predictions). With a telescope, center your field of view on Aldebaran. You probably won’t see the Moon’s dark limb lurking just west of the star. But as Luna’s orbital motion carries our satellite to its stellar rendezvous, Aldebaran will vanish suddenly. It will remain hidden for up to an hour or more (again, it depends on your location) before snapping back into view. The star returns at the bright limb, which makes the reappearance much harder to view.
Jupiter pokes above the eastern horizon around 9 p.m. local time in early March and during evening twilight by month’s end. This early rising time foreshadows the planet’s imminent arrival at opposition, the peak of its yearlong apparition, which will occur in April’s first week. And this means our view of the gas giant in March is close to perfection.
Jupiter brightens from magnitude –2.3 to –2.5 during March. Only the Moon and Venus outshine the solar system’s largest planet. Jupiter appears against the backdrop of Virgo the Maiden, approximately 5° from 1st-magnitude Spica. The constellation’s brightest star pales in comparison, however, appearing less than 5 percent as bright as the planet.
The approach of opposition also means that Jupiter is pulling closer to Earth and thus looming larger when viewed through a telescope. The planet’s equatorial diameter swells from 42" to 44" this month. Its polar diameter is 6 percent smaller, however, a difference noticeable even through small instruments.
But the first thing you’ll notice as you focus on Jupiter is its richly detailed atmosphere. The planet’s cloud tops resolve into a series of alternating bright zones and darker belts. Turbulence at the edges of these bands triggers more-subtle features. They show up under good observing conditions, typically after Jupiter climbs 30° above the horizon some three hours after it rises. You get sharper views then because the light travels through less of Earth’s atmosphere.
Whenever you have Jupiter centered in the field, you can’t help but notice up to four pinpricks of light hovering nearby. These are the Galilean satellites: Io, Europa, Ganymede, and Callisto, in order of their orbital distances. Because they circle the planet at different rates, their relative positions change constantly.