Monday, April 24
For those who like to observe during the quiet predawn hours, Saturn offers a visual treat this week. The ringed planet rises around midnight local daylight time and climbs some 30° high in the south by the time morning twilight begins. It shines at magnitude 0.3 against the backdrop of northwestern Sagittarius, where it appears nearly stationary relative to the background stars. Take a look at Saturn through binoculars and you’ll also see the open star clusters M21 and M23 as well as the spectacular Lagoon (M8) and Trifid (M20) nebulae less than 4° to its east. When viewed through a telescope, the planet shows a 18"-diameter disk surrounded by a stunning ring system that spans 40" and tilts 26° to our line of sight.
Tuesday, April 25
Look west after darkness falls tonight and you’ll witness the beginning of the winter sky’s decline. By 9:30 p.m. local daylight time, the lower tier of bright winter stars and constellations barely clears the horizon. From mid-northern latitudes, Sirius in Canis Major, Aldebaran in Taurus, and the three belt stars of Orion the Hunter all hang about 10° high. Still, a higher tier of winter stars remains prominent. Look for Capella in Auriga, Castor and Pollux in Gemini, and Procyon in Canis Minor to keep winter on your mind and in the sky for several weeks to come.
Wednesday, April 26
Although Jupiter reached opposition and peak visibility earlier this month (on the 7th), it remains a stunning sight nearly all night. It appears about 30° above the southeastern horizon during evening twilight and climbs highest in the south shortly after 11 p.m. local daylight time. Shining at magnitude –2.4, the giant planet is the night’s brightest celestial object with the exception of Venus, which doesn’t rise until morning twilight commences. Jupiter resides among the background stars of Virgo, 9° northwest of that constellation’s brightest star, 1st-magnitude Spica. When viewed through a telescope, the gas giant’s disk spans 44" and shows incredible detail in its cloud tops.
New Moon occurs at 8:16 a.m. EDT. At its New phase, the Moon crosses the sky with the Sun and so remains hidden in our star’s glare.
Thursday, April 27
With an age of 4.5 billion years, “young” might not seem an appropriate word to describe our Moon. But tonight, you have an exceptional opportunity to see what astronomers call a “young Moon” — a slender crescent visible in the early evening sky. With New Moon having occurred yesterday morning, only 4 percent of our satellite’s disk appears illuminated after sunset tonight. (Tomorrow evening, a 9-percent-lit lunar crescent hangs noticeably higher in the sky.) You should notice an ashen light faintly illuminating the Moon’s dark side. This is “earthshine,” sunlight reflected by Earth that reaches the Moon and then reflects back to our waiting eyes.
The Moon also reaches perigee, the closest point in its orbit around Earth, today. Our satellite lies just 223,275 miles (359,327 kilometers) away from us at 12:15 p.m. EDT.