The Night Sky This Month: February 2017

Hyginus Rille
Image credit: Onjala Observatory © by Franz Hofmann & Wolfgang Paech

February brings the opportunity to observe Orion and the more than dozen winter time constellations that surround it, as well as the planet Venus looking stunningly bright shortly after sunset, and a little above it to its left Mars.

Constellations

The constellation Orion rises in the east during the evening, and is seen towards the south around 00:00 before traveling onwards towards the west. This beautiful constellation contains 2 of the night sky’s brightest stars, namely the blue-white Rigel (7th), and the orange-red Betelgeuse (9th).

Orion depicts a giant hunter from Greek mythology, and surrounding him can be seen a number of other beautiful constellations depicting animals, including his hunting dogs Canis Minor (east) and Canis Major (south-east) chasing Lepus (south) the hare; while to Orion’s north-west, the giant is seen battling the ferocious bull Taurus. To Orion’s north lies Auriga, and to its north-east is Gemini, while further east the lionesque constellations of Leo rises to prominence as the night progresses.

Moon

Lunar observers have two great opportunities to observe Hyginus Rille in February, when favourable illumination on the 3rd and 17th of the month highlights this object of much debate among scientists. At issue is the uncertainty that surrounds the origin of the 11-km-wide crater that bisects the rille (fissure) called the Hyginus crater. One school of thought, for instance, proposes that the crater is the result of a meteor impact, just like most of the other craters on the Moon, while another holds that the crater formed when a lava tube (the rille) collapsed.

On February 10th/11th, a penumbral lunar eclipse can be seen in which only the outer shadow of the Earth creates a dark shading on the Moon’s surface. For observers in North America, the Moon will darken significantly on the 10th, with the mid-point of the eclipse occurring at about 7:44 PM Eastern Standard Time. Observers in Europe, Africa, and western Asia, on the other hand, will have to wait until the 11th for the event to be visible during the wee hours before dawn.

Phases

First Quarter: 4th
Full Moon: 11th
Last Quarter: 18th
New Moon: 26th

Planets

– Mercury can be found low on the south-eastern horizon just before dawn, to the lower left of the planet Saturn. Although this little planet is best seen during the middle of the month, when it will brighten to about magnitude -1.2, its small angular diameter of just 5 seconds of arc will make it impossible to discern any sort of detail on its disc.

Venus and Mars in Feb 2017– Venus is still dominating the western sky, and during February it will brighten to magnitude -4.8, which is about as bright as it gets. Keen-eyed observers will even be able to spot the planet during the late afternoon, and under dark skies. On February 4th, Venus will reach its highest elevation of 33 degrees just before sunset, with its brightness remaining fairly constant throughout the month. In fact, the planet will be too bright to discern any detail in its cloud cover, so be sure to use ultraviolet filters to observe or image the planet.

– Mars can be observed in the constellation Pisces to the upper left of Venus, with a separation of just 5.4 degrees on the first day of the month, increasing to about 12 degrees towards the end of February as Venus descends towards the western horizon. The month also sees Mars dimming somewhat from magnitude +1.1 to magnitude +1.3 as its angular diameter decreases from 5.1 to 4.6 seconds of arc, making it unlikely that any surface detail will be visible on its surface.

– Jupiter can be found about 3.5 degrees above the star Spica in the constellation Virgo at the start of February. During the first days, the “Giant Planet” rises over the eastern horizon at about 00:30, but rises progressively earlier until it ascends at about 22:45 at the month’s end. The planet’s angular diameter will also increase somewhat during the month, while its brightness will increase from magnitude -2.1 to magnitude -2.3. Note that Jupiter will stop moving eastwards on the 6th of February in order to start its retrograde motion westwards, which will continue for several months thereafter.

– Saturn is now a morning object in the southern reaches of the constellation Ophiuchus, shining at magnitude +0.5 when it rises at about 08:00 UT. By the month’s end, the planet will rise at about 06:30 UT, but note that while the planet will never rise higher than about 18 degrees or so over the southeastern horizon, it might be possible to get a glimpse of its ring system through the atmosphere by using an Atmospheric Dispersion Corrector.

Meteor Showers

February is known as the start of the “fireball” season, although none of the meteor showers on displays are expected to be particularly significant during the month. In fact, most will likely produce less than 1 meteor per hour. Nonetheless, the list includes the February Epsilon Virginids (Jan 29/Feb 9), Alpha Centaurids (Jan 28/Feb 21), Alpha Coronae Borealids (Jan 27/Feb 5), and February Eta Draconids (Feb 2-5).

Deep Sky Objects

While comets are not exactly deep sky objects, one comet is expected to swing by Earth during the first two weeks of the month, namely Comet 45P/Honda-Mrkos-Pajdusakova, which passed around the Sun in December 2016. It is now expected to pass Earth within 8 million miles as it swings out back into the solar system, so look for the comet in the constellations Aquila and Hercules a few days before and after the 11th, when it is expected to reach naked-eye visibility. Keen-eyed observers should be able to see the comet as a small, fuzzy, but distinctly moving object as it races across the constellations day by day.

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