What's Up in the Night Sky?

April 2016 - Vol. 20, No. 4

Astra's Star Gate

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

As the days lengthen in the northern hemisphere, the stars of the Winter Triangle fade into evening's dusk. The "Big Dipper" asterism (Ursa Major) is well placed for viewing this month since it is almost directly overhead. Follow the curve of its handle to Arcturus (Bootes) and continue on the curve to Spica (Virgo). Regulus (Leo) is on the ecliptic (the path traced by the planets and Moon), just W. of overhead. Further W., on the ecliptic, find the Gemini Twins, Castor and Pollux, and finally the Pleiades asterism of Taurus.

MERCURY is well placed in the evening sky this month appearing best for northern observers. This apparition is the best placed for northern observers this year. The fleet footed planet will reach perihelion on the 5th. VENUS still in the morning sky, will be dropping toward the horizon, with an occultation by the Moon on April 6. MARS befor midnight, moving into the ecliptic constellation Ophiuchus. It will start a retrograde motion in the sky after mid-month (Apr. 17). The red planet will be in opposition on May 22 and thus begins prime viewing time for Astra's favorite planet after Earth. JUPITER still in Leo, will be in conjunction with the moon on April 18. SATURN rises before midnight this month. The outer planet NEPTUNE appears in the morning skyin Aquarius.

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times. Unfortunately some of these events may occur during daylight hours in your area.

DATE EVENT
05 Venus .7 deg S. of Moon, occultation from north Africa, Europe, northern Middle East, and northwest Asia.
07 Moon at perigee.
09 Extreme 18.6 year tide. You can read about this cycle from the National Oceanographic Centre published in the UK.

For asteroid buffs, the Moon will occult the asteroid Vesta at 4 UT, This may be observed from Indonesia, Malaysia, northwestern Australia, the Phillippines and Hawaii.

14

Aldebaran 0.3 deg S. of the Moon occultation from Hawaii, USA, Northern Mexico, southern Canada, northern Carribbean and the Azores.

15 Look for the Moon about 5 deg S. of the Beehive cluster.
18 Jupiter 2 deg N. of Moon.
21 Moon at apogee.
22 Lyrid meteor peak, The shower is estimated to contain 20 meteors at peak, this year the Moon is full and will interfere with observing.
25 On this night, the Moon, Mars, Saturn and Antares will be together in the sky forming an interesting sight. The Moon will be a few days past full so it will dominate the scene.
26 Juno at opposition. A large asteroid, Juno is the third one that was discovered. (September 1, 1804)

Lunar Almanac for April 2016

Phases of the Moon Phase and Date(s) Best viewed before local midnight
new moon New
07
Deep Space Objects
first quarter moon 1st. Qtr
14
Planets & Moon
full moon Full
22
Moon
last quarter moon Last Qtr
30
Deep Space & Planets

Topic of the month: Jupiter, King of the Night Sky

August 24, 2016In recognition of Jupiter reaching opposition this month, the night sky features the giant planet. Jupiter may be the amateur astronomers favorite planet to observe, due to the fact that so many interesting features can be seen in the outer atmosphere of this massive planet. It contains the lion's share of the mass of the solar system outside of the Sun, 2.5 times all other planets combined. It is over 5 times further from the Sun than planet Earth. It spends 10 months in the sky every 13 months. It takes the giant planet 11.86 years to return to the same spot in the sky, so that it spends about a year in each constellation of the zodiac. When it reaches opposition this year, the disk will appear over 44" in diameter.

The four largest moons of Jupiter are called Galilean moons because they were discovered by Galileo with the small telescope he first pointed at the heavens. It became obvious to Galileo that the small stars he observed by the planet were actually satellites like our own moon. Over the course of an evening, he could tell that they orbited the giant planet. Eager to share his discovery, he published Starry Messenger. But in Galileo's day, the pope decreed that no object in the heaven orbited any other object but God's perfect creation, mother Earth. The four Gallilean moons may be observed at opposition by a star gazer with a steady hand through a pair of binoculars. Slight surface color variations have been reported by observers. The four giant moons are not the only satellites of Jupiter, to-date we have discovered that the giant planet has 67 companion satellites

The planet is made of hydrogen gas and does not have a surface like Earth or Venus. Instead, observers on Earth see the only the outer layers of clouds in the planet's atmosphere. The planet rotates in an incredible 9 hours and 51 minutes at the equator, with speeds at the poles being somewhat less. This means that features rotate very quickly across the surface. Serious observers who make sketches plan on drawing the surface features in 10 minutes. Astronomers track features by imagining a central line stretching from pole to pole, called the central meridian. As features cross this line, they are said to be transiting the meridian. And what a variety of features can be seen! Prominent bands mark the North and South Equatorial Belts (NEB and SEB respectively) and these can be seen in even small telescopes. Unless of course Jupiter pulls one of its usual, unusual tricks and one of these belts disappears temporarily. Other features appear as white, red or bluish ovals. Every night the disk of our giant neighbor holds its own surprises! One feature that has been considered permanent is a great storm that has been called the Great Red Spot (GRS) It was first identified in 1664 and was estimated to be 36,000 km in length in 1880, but today it covers 15,000 km. There is speculation that the GRS is not as permanent as once thought and may dissipate, especially as the dark red color turned to an orangish pink. Observations this year, however, finds the GRS once again becoming a bright cherry color. Always mysterious, Jupiter can still surprise us.

 

--See You Under the Stars!
Astra for Astra's Almanac

The star chart above was generated by Stellarium, a free open source planetarium program. This image was created by Dawn Jenkins, using Stellarium and a graphic editing program to format the image for this web page. The second image above was created by Thuvan Dihn and licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. It has been modified as allowed under the license by Dawn Jenkins and may be distributed as stated on the Wikimedia Commons website.

This installment of "Whats Up?" is ©2015 by Dawn Jenkins for Astra's Stargate. View Ron Leeseburg's Farewell Issue for information on where to find information such as is presented in this almanac.