On the morning of February 18, we’ll have an opportunity to observe a rare phenomenon: an “eclipse” of Mars!
Sure, we’re all familiar with solar eclipses, where the Moon blocks out our daytime star, but the Moon can also come between us and a distant star or pass in front of a planet in the Solar System. In astronomy, this phenomenon is known as an occultation.
The Moon orbits the Earth in approximately 27 days and 8 hours, moving its own apparent diameter in just over an hour with respect to the background stars. However, the duration of an occultation depends, among other things, on how the Moon is blocking the celestial object in question. If only the top or bottom edge of the Moon passes in front of the star or planet, the occultation will be short-lived. But if the celestial body slips behind the middle of the Moon’s disc, the occultation will last longer.
The February 18 occultation of Mars will occur during the day. Early risers (or night owls, as the case may be) can spot the Red Planet to the left of the waning Moon, low on the southeastern horizon after 4 a.m. As the night draws to a close, the duo will rise up and draw ever closer to each other.
From Montreal, the occultation starts at 7:38 a.m., nearly two hours after sunrise. If the sky is clear, you’ll be able to locate the Moon with the naked eye, about 20 degrees above the southern horizon, but you may need a small telescope to view Mars just before or after the occultation. (Be careful not to point your optical instruments directly at the Sun!) The phenomenon ends at 8:59 a.m., when Mars reappears on the other side of the lunar disc.
Two other occultations involving bright stars will occur a few days earlier. The evening of February 5, the star Tejat Prior, or Propus (Eta Geminorum), disappears at 7:45 p.m. behind the dark limb of the waxing gibbous Moon and reappears on the lit side at 8:57 p.m. A few hours later, its neighbour Tejat Posterior (Mu Geminorum) gets occulted between 12:24 and 1:20 a.m. on the morning of February 6.
Planets in the morning sky
Three planets are visible in the February morning sky: Mars, Jupiter and Saturn. One by one, they climb above the southeastern horizon as night draws to a close.
The Red Planet is the first to rise around 4 a.m. Located in the constellation Ophiuchus early in the month, it joins its two sidekicks in Sagittarius beginning on February 11. This constellation is easy to find since it forms the famous Teapot in the sky. Mars will shine above the Teapot’s lid, moving from right to left as the days go by. The Moon will of course be right next to the planet on February 18, a few hours before the occultation.
Located to the left of the Teapot’s handle is brilliant Jupiter, which rises just before 6 a.m. at the beginning of the month, then increasingly earlier with each passing day. For its part, Saturn will be visible to the lower left of the Sagittarius Teapot. The planet rises around 6:30 a.m. in early February, then shortly before 5 a.m. by month’s end.
The Moon can serve as a guidepost to locate these planets: The thin lunar crescent will hang to the right of Jupiter on February 19, then slightly lower and to the right of Saturn the next day.
Venus and Mercury in the evening
Dazzling Venus dominates the early evening sky. The planet can be spotted due southwest in the minutes following sunset and remains visible until 8:30 p.m. On the evening of February 27, the thin crescent Moon will lie to its immediate left.
Finally, Mercury makes a nice foray into the evening sky during the first half of February. Try spotting it in the glow of twilight approximately 30 minutes after the Sun sets. It will appear above the west-southwestern horizon, but much lower than Venus.