2018 Planetary Positions
Venus (magnitude –3.9) shines brightly in the west-northwest during evening twilight and just after. It's nearly as high
as it will get all this spring and summer. In a telescope (look early!) Venus is a little disk 12 arc seconds wide and slightly
gibbous: 87% sunlit. Venus is currently traveling through Gemini.
Jupitier is at opposition this week: exactly so on May 8th. It's the brightest point in the sky after Venus sets below
the opposite horizon. Jupiter is now as bright and big (44.8 arcseconds across its equator) as it will appear this year.
It's highest in the south, presenting the sharpest views in a telescope, around midnight or 1 a.m. daylight-saving time.
By dawn it's very low in the west-southwest.
Saturn glows steadily in the south-southwest at nightfall. Antares, less bright, twinkles 12° to Saturn's lower right. Saturn is currently retrograde
in expansive Sagittarius!
Uranus in Aries is hidden in the glow of dawn.
Distant Neptune can be found among the background stars of Pisces.
With a telescope, trying to resolve Neptune into a disk will be a troublesome task. You are going to need at least a four-inch instrument with a magnification of no less than
200-power, just to turn Neptune into a tiny blue dot of light.
Denser than the other gas giants, Neptune probably has ice and molten rock in its interior, although rotational data imply that these heavy materials are spread out rather
than concentrated in a small core. The atmosphere is swept by winds moving at up to 2,300 feet per second, the fastest found on any planet. At the equator, the winds blow
westwards (retrograde) and beyond latitude 50 degrees they become eastwards. Temperature measurements show that there are cold mid-latitude regions with a warmer equator and pole.
Neptune's thirteen known moons include Nereid, with the most eccentric orbit of any planetary satellite, seven times as distant from the planet at its farthest compared with its closest approach; and
Triton, the only large moon in the solar system with a retrograde orbit, which is an orbit in the opposite direction to that of Neptune's.
The dwarf planet Pluto lies in northern Capricorn and is highest above the southern horizon just before dawn. Search for it under a dark,
moonless sky. Pluto glows atmagnitude+14, and as a result, it is a challenge to spot. An 8-inch telescope on a perfect night brings Pluto to
the edge of visibility. For a direct view, however, you will want touse at least a 10- inch scope.
Mercury (magnitude 0) is having a very low, poor apparition deep in the glow of sunrise. Using binoculars, look
for it 15 or 20 minutes before sunrise barely above the east horizon. Nothing else there is as bright. Mercury
is currently speeding through Aries!
Mars and Saturn rise late at night, around 1:30 a.m. and midnight, respectively (daylight-saving time). They're on opposite
sides of Sagittarius, shining at magnitudes –0.5 and +0.3, respectively, with Mars on the lower left. Saturn is above the
Teapot. By early dawn they're higher in the south.