This is a special two-week edition of the Griffith Observatory Sky Report for the period ending Wednesday, April 18, 2012. Here is what’s happening in the skies of Southern California:
Venus, the brightest planet, appears at its highest in the evening sky on Wednesday, April 4, when it 44½ degrees above the west-northwest horizon at sunset. On following dates, it will move lower and closer to the sun, a motion culminating ultimately in a rare transit across the face of the sun on the afternoon of June 5. Through a telescope, Venus now shows a crescent phase. Venus is still brightening, and can be seen in broad daylight with the unaided eye. Between the 4th and the 18th, Venus is due south within a couple of minutes of 3:50 p.m., and is less than 10 degrees south of the zenith, the distance spanned by a clenched fist seen at arms length from the point directly overhead. The brilliant-white planet sets at 11:10 p.m.
Jupiter, the second brightest planet, is less than half as high as Venus when the sky grows dark, and by mid-month will be hard to see against the twilight as it moves closer to the sun. Jupiter’s setting time moves from 9:31 p.m. on the 4th to 8:52 p.m. on the 18th.
The moon changes phase from waxing gibbous to full on the 6th. It then wanes through gibbous phase to last-quarter on the 13th and appears crescent through the 18th. On the 7th, moonrise occurs just as night is falling, and the time of moonrise advances from 10:03 p.m. to 4:40 a.m. between the 8th and 18th.
The orange planet Mars stays about 5 degrees to the east of Leo the Lion’s brightest star, Regulus, and appears high in the southeast as darkness falls. The planet fades slowly following its close approach to earth last month, but remains significantly brighter than Regulus and has a distinctive orange hue. Through a telescope, the planet’s disk shrinks from 12 to 11 arcseconds, large enough to make out some detail when our air is steady. The best time to look is when the planet is highest in the south, which happens about 4 minutes earlier each successive night, changing from 10:30 p.m. to 9:30 p.m. between the 4th and the 18th.
Saturn, the ringed planet, is visible all night long, and is directly opposite the sun on the 15th. Saturn is then closest to earth (8.7 AU or 811 million miles), and the image that we observe is already 72 minutes old. Through a telescope, the planet’s rings appear tilted 14˚ in our direction and span 43 arcseconds, while the equatorial diameter of the planet measures 19 arcseconds. The full moon is near Saturn on the 6th. The planet is to the left of Spica, the brightest star of Virgo the maiden. The planet outshines the star, and has a golden hue compared to Spica’s blue-white appearance.
Early-risers can find the planet Mercury about 5 degrees above the eastern horizon 30 minutes before sunrise starting on April 10. The waning crescent moon is 7 degrees above Mercury on the morning of Wednesday, April 18. The innermost planet displays a crescent phase visible through a telescope.
The International Space Station should make an early morning passage high above Los Angeles on April 8. The brilliant ISS should burst out of earth’s shadow at 5:03 a.m., 51 degrees high in the west-northwest. A minute later it sweeps nearly overhead, 82 degrees high in the southwest, then sinks to the southeast horizon at 5:07 a.m. The space station should make an evening appearance on the following evening, April 9. The ISS will cross the sky from southwest to northeast between 8:37 p.m. and 8:42 p.m., and is 67 degrees high in the west-southwest at 8:40 p.m. For updated times, visibility from other locations, or for other satellites, generate customized predictions on heavens-above.com.
Free public viewing of the sun during the day and of the moon, planets, and other celestial objects at night, is available in clear weather five days a week (Wednesday-Sunday) through Griffith Observatory’s telescopes before 9:30 p.m. Check our website for our special spring break schedule. The next public star party of the Los Angeles Astronomical Society and the Sidewalk Astronomers is scheduled for Saturday, April 28.
From Griffith Observatory, I’m Anthony Cook, and I can be reached at firstname.lastname@example.org.