The Moon and Planets

For most of this week, the moon will be visible every evening — waxing fuller while it travels eastwards. When the nearly full moon rises on Wednesday, February 28, it will sit only about 2 degrees above the bright star Regulus in Leo (the Lion). During the evening, the moon’s eastward orbital motion will carry it past the star, with closest approach shortly after 1 am EST. Observers in the northeastern tip of Russia, northern North America, Greenland, Svalbard, the western edge of Europe, and the Azores will get to see the moon pass over (or occult) Regulus.

(Above: On the night of February 28, 2018, the nearly full moon will pass close to Regulus, the brightest star in Leo. Shown here at midnight, the moon’s eastward orbital path is shown in yellow.)

Thursday evening brings the final full moon of winter. The March full moon, known as the Worm Moon, Crow Moon, Sap Moon or Lenten Moon, always shines among or near the stars of Leo. Full moons always rise in the east as the sun sets, and set in the west at sunrise. And winter moons always climb to a high position in the night sky. For the warmer months of the year, full moons will not get as high at night because the noontime sun is moving higher. The two objects sit on the opposite ends of the ecliptic, which acts like a celestial teeter-totter.

Grab your binoculars and look for the many ray systems sprayed across the full moon’s face. The rays are straight lines composed of material that has been thrown radially outwards by objects that slammed into the moon long ago. The rays are enhanced when the moon is lit face-on, as it is around the full phase. Impacts on the light-coloured lunar highland rocks tended to spread white rays over the surrounding darker mare regions — but sometimes the inverse happens. Some ray systems are enormous — spanning half the moon’s disk! The rays emanating from the crater Tycho, the “jewel” at the Lady-in-the-Moon’s throat, is a fine example.

(Above: Some of the lunar ray systems visible in binoculars and telescopes on a full moon.)

There will always be a crater where the rays converge because that’s where they originated. But the distribution of the rays isn’t always circular. Objects that struck the moon at a shallow angle only threw material in front of them, making the ray system asymmetrical. One of the best examples of this is the ray system for the crater Proclus. The smallish crater and ray system, visible in binoculars, are located at the lower left edge of Mare Crisium, the round grey basin near the moon’s upper right edge (northeast on the moon). The Proclus rays only extend toward the right-hand side of the crater towards Crisium.

(Above: The object that formed the bright crater Proclus (at centre) arrived at a shallow incline from the lower left, producing an non-uniform ray system in front of it that included round Mare Crisium and environs. Image by Philipp Salzgeber http://www.salzgeber.at/astrophotography/lunar/moon-and-jupiter/)

Finally, next Sunday evening will see the moon land a palm’s width to the left of the bright star Spica in Virgo (the Maiden).

Bright Venus continues to emerge from the western evening twilight this week. You can look for it very low above the western horizon after sunset, particularly between about 6:10 and 6:40 pm local time. During this week Mercury will climb towards Venus. Tonight (Sunday) it will sit about four finger widths below, and slightly to the right of Venus. For next weekend, Mercury will reach a position one finger width to the right of Venus — with the best viewing time about 6:30 pm local time. In a telescope, both planets will show nearly full disks because they are on the far side of the sun from Earth.

(Above: At the end of this week, Mercury’s climb away from the sun will carry it to a position only 1 degree to the right of the bright planet Venus, as shown here for 6:30 pm local time on Saturday, March 3, 2018. Night Sky Chart made via Star Walk 2 iOS and Star Chart for Android.)

The rest of the bright planets are still in the pre-dawn sky. Extremely bright Jupiter rises first, just after midnight local time. By 6 am local time, it reaches its highest elevation (about three fist diameters) above the southern horizon. Next week, Jupiter begins rising before midnight!

(Above: Shown for 6 am local time, the morning parade of planets begins shortly after midnight when bright Jupiter rises, followed by dimmer reddish Mars, and finally medium-bright yellowish Saturn. The asteroid Vesta will sit a palm’s width above Mars all week. Night Sky Chart made via Star Walk 2 iOS and Star Chart for Android.)

Dimmer, reddish Mars rises next at about 2:30 am local time. Mars is sitting 2.5 fist diameters to the east (left) of Jupiter this week. It is pulling away from Jupiter and gradually approaching Saturn. The yellowish ringed planet rises about 3:45 am local time, putting it a comfortable height of 1.5 fist diameters above the southeastern horizon just before the dawn sky begins to brighten. The teapot-shaped constellation of Sagittarius (the Archer) is directly below it — as it will be all year. This week, the large asteroid Vesta will sit 6° (a palm’s width) above Mars. You’ll need binoculars or a small telescope to see it.

Astronomy Skylights for this week (from February 25th, 2018) by Chris Vaughan.

Keep looking up to enjoy the sky! I love getting questions so, if you have any, send me a note.