March 2018

Welcome to SkyEye, your guide to this month's celestial events.

The Calendar

Date Body Event
1 Moon occultation of Regulus: visible from northeastern Asia, northern North America, Greenland, Iceland, and northern and western Europe
2 Moon full
4 Neptune conjunction
5 Mercury, Venus 1.4° apart
9 Jupiter stationary point: direct → retrograde
Moon last quarter
10 Mercury perihelion
11 Moon apogee
14 Moon descending node
15 Mercury greatest elongation east (18.4°)
17 Moon new
20 Mars 0.8° north of NGC 6530, an open star cluster within M8, the Lagoon Nebula
Earth equinox
22 Mercury stationary point: direct → retrograde
Moon occultation of Aldebaran: visible from visible from northeastern Asia, northwestern North America, Greenland, Iceland and northern Europe
24 Moon first quarter
Mars west quadrature
26 Moon perigee
27 Moon 1.8° south of Praesepe (also known as the Beehive Cluster)
Moon ascending node
28 Moon occultation of Regulus again: visible from north Asia, northwestern North America and northern Europe
29 Venus, Uranus 0.1° apart
Saturn west quadrature
31 Moon full

The Solar System

The word planet is derived from the Greek word for 'wanderer'. Unlike the background stars, planets seem to move around the sky, keeping mostly to a narrow track called the ecliptic, the path of the Sun across the stars. Dwarf planets and small solar-system bodies, including comets, are not so constrained, often moving far above or below the ecliptic.

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Sun AquariusPisces

The solar south pole is most inclined toward the Earth early this month.

Mercury AquariusPisces

The closest planet to the Sun begins the month rising higher in the western sky after sunset. On the fifth day it has a close encounter with Venus, appearing less than 1.5° north of the brighter planet. By mid-month, it is falling towards the horizon and soon disappears for southern hemisphere observers. Views of this elusive planet are better in the nothern hemisphere, with Mercury staying above the horizon until late into the month. Mercury reach greatest elongation east on 15 March and changes direction, direct to retrograde, on 22 March.

Venus AquariusPiscesAries

The evening star is best seen from the northern hemisphere as it rises rapidly above the western horizon after sunset. It's getting higher in the sky as seen from the southern hemisphere too but not to the same extent. On 5 March, Venus appears just south of fellow inferior planet Mercury. It has another planetary close encounter on 29 March when it passes 0.1° south of Uranus. Optical aids will be necessary to spot sixth-magnitude Uranus next to bright Venus in the twilight.

Earth and Moon

On 20 March, Earth reaches equinox. The word equinox means 'equal night' so that on this day, the (centre of the) Sun spends an equal amount of time above and below the horizon everywhere on the planet.

The second Full Moon this month is often called a Blue Moon. It is the second Blue Moon to occur this year, the first happening in January. The first-magnitude star Regulus is occulted twice this month, on 1 March and again on 28 March. Aldebaran in the constellation Taurus also falls victim to the Moon on 22 March.

Mars OphiuchusSagittarius

The red planet passes less than a degree north of the open star cluster NGC 6530 on 20 March. West quadrature, that instant when Mars appears 90° away from the Sun, occurs on 24 March. Due to its southerly declination, the red planet is most easily seen from equatorial and southern latitudes.

Jupiter Libra

Now rising around midnight, Jupiter is still difficult to see from the northern hemisphere as it remains low in the sky. On 9 March the gas giant reaches a stationary point and reverses direction, going into retrograde.

Saturn Sagittarius

Still a morning sky object for northern hemisphere observers, the ringed planet now rises just before midnight for viewers in the south. At west quadrature on 29 March, the interplay of shadows - disk, rings, satellites - in the Saturnian system are at their most pronounced.

Uranus Pisces

This greenish-coloured planet is getting increasingly difficult to see in the evening twilight as it approaches conjunction with the Sun next month. It has an extremely close encounter with Venus on 29 March.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system but potential observers won't get much joy this month. Neptune is at solar conjunction on the fourth day and lost to view in the glare of the Sun.

The Celestial Sphere

Constellations are patterns of stars in the sky. The International Astronomical Union recognises 88 different constellations. The brightest stars as seen from the Earth are easy to spot but do you know their proper names? With a set of binoculars you can look for fainter objects such as nebulae and galaxies and star clusters or some of the closest stars to the Sun.

Descriptions of the sky for observers in both the northern and southern hemispheres are available for the following times this month. Subtract one hour from your local time if summer (daylight savings) time is in effect.

Local Time Mid-month Northern Hemisphere Equator Southern Hemisphere
1730 hours (1830 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
1930 hours (2030 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
2130 hours (2230 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
2330 hours (0030 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
0130 hours (0230 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
0330 hours (0430 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
0530 hours (0630 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S