The Sky This Month – April 2017

The planet Jupiter (credit: NASA)

The planet Jupiter (credit: NASA)

1 April. Mercury reaches its greatest eastern elongation at 19° from the Sun. In the northern hemisphere, the speedy little planet is at its highest altitude of the year. Look for Mercury low over the western horizon about half an hour after sunset. The planet shines at a respectably bright magnitude -0.2 and, in a telescope, reveals a half-lit disk. Slightly fainter and much redder Mars lies about a fist’s-width above Mercury. Over the next week, you will see Mercury plunge back towards the horizon as it quickly makes its way around the Sun.

3 April. First Quarter Moon, 18:39 UT

5-6 April. Look towards Jupiter rising in the east or southeast well after sunset. Tonight, the planet comes close to the star theta (θ) Virginis, so close that the star might appear as a 5th moon of the planet. Theta is a little brighter than Jupiter’s four bright moons, and it’s a little further away even at closest approach. Still, this event is worth a few moments of contemplation in a telescope or binoculars.

Mercury and Mars in the western sky after sunset on April 1, 2017.

Mercury and Mars in the western sky after sunset on April 1, 2017.

7 April. The planet Jupiter reaches opposition. This means it rises in the east as the Sun sets in the west. The planet is now as close and bright as it will get all year. This year, the planet is slightly less bright than at past oppositions because it’s near aphelion, its farthest point from the Sun. Still, Jupiter’s brightness peaks at magnitude -2.5 this month, far brighter than any star, and it has an apparent diameter of 44″. Grab your binoculars and watch the moons dance around the planet from night to night. Or grab your telescope and power up to see the perpetual storms and fine detail nestled in the cloud bands of this great planet. There’s always something to see on or around Jupiter, and this month and the next few months is the best time to see it.

10 April. That bright star near the nearly-full Moon? Yep, that’s Jupiter.

11 April. Full Moon, 06:08 UT

16 April. The waning gibbous Moon comes within three finger widths of the planet Saturn in the southwestern sky in the early morning hours. The straw-colored planet rises before midnight and slowly grows in size and brightness on the way to its mid-June opposition. The planet lies well south this year on the ecliptic in the constellation Sagittarius and starts retrograding (moving westward) on April 6. Its position favors southern stargazers this year. But all telescopic observers will see a fine presentation of the rings tilted at a dramatic 26° from edge-on.

If you want to learn more about how to see Jupiter, have a look at the Cosmic Pursuits ‘Observer’s Guide to the Planet Jupiter’ at this link.

Saturn rises in the southeast well after midnight in mid-April 2017. The planet lies in western Sagittarius and retrogrades (moves westward) from April 6 until mid June.

Saturn rises in the southeast well after midnight in mid-April 2017. The planet lies in western Sagittarius and retrogrades (moves westward) from April 6 until mid June.

18 April. The planet Mars comes within just 4º the Pleiades in the western sky after sunset.

19 April. Last Quarter Moon, 09:57 UT

22 April. The Lyrid meteor shower peaks tonight. With a maximum of 10-20 meteors per hour, it’s not the best meteor shower of the year, but if you’re out after midnight, it’s well worth a look. The Lyrids appear to trace their paths back to a radiant about 10º southwest of the bright blue-white star Vega, which northern stargazers can see rising in the northeast by 10 p.m. in mid April.  The radiant lies in the constellation Hercules, but the shower was named before the constellation boundaries were formalized in the early-20th century. The Lyrid meteors are sandgrain-sized pieces of dust and ice left over from the periodic Comet C/1861 Thatcher which last crossed Earth’s orbit on April 20, 1861.  The comet returns to Earth every 415 years, so the Lyrids have been observed for thousands of years.

A few Lyrid meteors in 2007. Credit: Phillip Chee/Flickr.

A few Lyrid meteors in 2007. Credit: Phillip Chee/Flickr.

23 April. Venus is back! After plunging rapidly towards the horizon last month in the evening sky, the planet passed to the other side of the Sun and now appears as the “Morning Star”. Look for it before sunrise low in the east. Today, the planet is joined by a slender crescent Moon.

26 April. New Moon, 12:16 UT

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