Earth--Day and Night Regions

Earth--Day and Night Regions

Planetary Positions

Saturday, March 31, 2012

Night Sky this Month--April 2012

The Night Sky This Month (April 2012)

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Key Stars

The stars of the Winter Triangle (Sirius, Betelgeuse and Procyon) are
low in the evening twilight throughout April. The Plough asterism, or
Big Dipper, is best placed for observation this month, being overhead
at 10 P.M. local daylight time. Brilliant Arcturus (Alpha Bootis) and
Spica (Alpha Virginis) are in the southeast. Regulus (Alpha Leonis)
remains high in the southwest while Vega (Alpha Lyrae), one of the
stars of the Summer Triangle, makes its appearance in the northeast.

The Planets


Mercury reaches its greatest elongation on the 18th, when it lies 27
degrees west of the Sun. Early risers may catch a brief view of the
planet in the pre-dawn sky, about 30 minutes before sunrise and only 5
degrees above the eastern horizon. Binoculars could prove useful for
spotting it against the bright twilight.


Venus, the dazzling Evening Star, outshines all the other stars and
planets in the night sky and is in good view in the west as darkness
begins to fall. It begins the month only 1 degree below the Pleiades
star cluster and slowly moves eastward with each passing day. By April
30, the planet sits just 3 degrees south of second-magnitude Beta
Tauri, also known as Elnath, El Nath, or Alnath.


By mid-evening, as Venus and Jupiter set in the west, Mars stands
two-thirds of the way from the southeastern horizon to the zenith. It
spends the month floating 5 degrees or less from Regulus (Alpha
Leonis), a slightly dimmer star with which it contrasts beautifully.
Through a telescope, the Red Planet's disk will appear no bigger than
12" across, still rather small even at high magnifications.


If you have a clear, flat horizon, look for Jupiter lying low in the
west after sunset. This is your last chance to spot the planet during
the current apparition. By the end of the month, Jupiter will
disappear into the evening twilight and then slip behind the Sun at
conjunction on May 13. Afterwards, in mid-June, Jupiter will emerge
from the dawn twilight and be visible in the morning sky before


Saturn rises at the end of evening twilight as April begins. It shines
high in the southeast, among the stars of Virgo the Maiden and close
to brilliant Spica, by midnight. The ringed planet reaches opposition
and peak visibility on the 15th, rising then around sunset. Opposition
is about when a superior planet attains its maximum apparent size and


Uranus is lost in the glow of sunrise and very difficult to spot. It
will return to view in mid-May, low in the morning sky.


Distant Neptune can be found among the background stars of Aquarius,
low in the east before dawn's first light. The planet glows dimly at
magnitude +7.9, much too faint to be viewed with the unaided eye,
lying at a mean distance from the Sun of 2.8 billion miles.


The dwarf planet Pluto lies in northern Sagittarius and is highest
above the southern horizon just before dawn. Search for it under a
dark, moonless sky. Pluto glows at magnitude +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 to use at least a 10-inch scope.

Bright Asteroids

6 Hebe

The main-belt asteroid 6 Hebe lies within 1.5 degrees of Algieba
(Gamma Leonis), and tracks westwards until mid-month. Soon after this,
it completes its retrograde loop and starts heading eastward. Glowing
at about 10th-magnitude, Hebe looks like an ordinary field star and is
highest above the southern horizon around 10 P.M. local daylight time.

Bright Comets

C/2009 P1 Garradd

Comet Garradd has been observable in northern skies for over a year
now. Despite the fact that it is currently receding from both the Sun
and Earth, it still glows around 7th-magnitude and remains a nice
sight throughout binoculars and small telescopes. In early April,
Garradd slides through the background stars of the constellation Ursa
Major, but by mid-month it passes the border into neighboring Lynx.
For observers located at mid-northern latitudes comet Garradd is
circumpolar, meaning that it never sets and can be viewed all night.

Meteor Showers

The Lyrids

This year, astronomers predict that the shower will climb to a sharp
peak in the predawn hours of April 22. However, activity begins on
April 16 and continues until about the 25th. The radiant is located in
a region of the sky between the constellations Lyra and Hercules, and
is overhead around 5 A.M. local daylight time. With New Moon arriving
on April 21, conditions could hardly be better.

The Eta Aquarids

The Eta Aquarids first appear around April 19, and some can be seen
until May 28. The shower's peak occurs around May 5, when up to 20 or
30 meteors can be seen each hour from a dark-sky site. Throughout
April, the shower's radiant is found in western Aquarius - close to
Beta Aquarii - and moves daily a little to the northeast. The radiant
never gets very high in the sky before dawn, so your observing time is

Sky Events

April 3 - Venus is 0.4 degree south of the Pleiades star cluster at
8:18 A.M. EDT.

April 6 - Full Moon at 2:19 P.M. EDT.

April 7 - The Moon is 1.4 degrees south of Spica (Alpha Virginis) at
1:24 A.M. EDT. The Moon is at perigee, the point in its orbit when it
is nearest to Earth.

April 13 - Last Quarter Moon at 5:50 A.M. EDT.

April 15 - Saturn is at opposition, exactly opposite the Sun in the
sky as seen from the Earth.

April 18 - Mercury is at greatest western elongation, 27.5 degrees
west of the Sun in the morning sky.

April 21 - New Moon at 2:18 A.M. EDT.

April 22 - The Lyrid meteor shower is at peak activity. The Moon is at
apogee, the point in its orbit when it is farthest from Earth.

April 24 - The Moon is 6.3 degrees south of Venus at 9:21 P.M. EDT.

April 28 - Astronomy Day! Established to promote astronomy to the
general public.

April 29 - First Quarter Moon at 4:58 A.M. EDT.

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