Night Sky Guide: April to June 2013

Author: Kelly Whitt

Two comets are visible in April, with Comet Panstarrs lingering after its big March appearance and Comet Lemmon moving from the Southern Hemisphere into the Northern Hemisphere. Both comets will occupy the same region of sky but at different times. Comet Panstarrs passes through Pisces moving from left to right in March at sunset in the west. Comet Lemmon passes through Pisces moving from right to left in late April at sunrise in the east. Comet Panstarrs may return in 110,000 years to our part of the solar system while Comet Lemmon could return in 11,000 years.

Comet Panstarrs as seen in March 2013
Credit: John Chumack

Comet Panstarrs’ biggest event in April will be on the 3rd when it passes a few degrees from the Andromeda Galaxy, M31. Soon it will dim as it zips away from the center of the solar system. Comet Lemmon’s big event will be on April 17 when it appears three degrees from Mercury. Comet Lemmon is expected to shine at about 4-5th magnitude. It becomes a Northern Hemisphere object after April 19.

Saturn is rising in Libra in the east-southeast in the evening. April 28 brings Saturn’s opposition, when it rises and sets opposite the Sun in our sky, remaining visible all night. On April 25, Saturn will lie to the upper left of the Full Moon.

On the date of Full Moon, April 25, a partial lunar eclipse will grace the night sky, with maximum eclipse occurring at 20:07 UT. The Moon enters the penumbral shadow but only skims the edge of the umbral shadow, making the Moon seem merely dim. This eclipse is best suited for observers in Eastern Africa, the Middle East, and India, although many others will also get a view of it as well.

April's meteor shower is called the Lyrids, and it occurs between April 19 and 24 with the peak overnight on April 21. Emanating from the constellation Lyra, the comet responsible for this shower is named Thatcher. The April Lyrids' Zenithal Hourly Rate (ZHR, or expected meteors per hour) is 12.

The Moon passes close to Spica on April 24 and appears to Jupiter’s upper left on April 14. Jupiter starts the month high in the west at sunset, still in the constellation Taurus. Venus is climbing away from the Sun every night, heading toward a conjunction with Jupiter in May.

May begins with the Eta Aquarid meteor shower, one of the better showers of the year with a ZHR of 45. The peak of activity will be over the weekend of May 4/5. Eta Aquarids get their name because they appear to come from the constellation Aquarius near the star Eta. This shower is one of two annual showers whose source is Halley's Comet.

An annular solar eclipse is slated for May 9 and 10 over Australia and the Pacific Ocean. An annular eclipse occurs when the Moon is too far from Earth to completely block the Sun, and therefore a ring, or annulus, appears around the Moon. Annular eclipses are not safe to be viewed without eye protection. The partial phase begins on May 9 at 22:22 UT, with the annular event beginning May 10 at 00:22 UT. Maximum eclipse occurs May 10 at 00:25 UT and the annular phase ends at 00:28 UT. The partial phase of the eclipse wraps up on May 10 at 2:30 UT.

The real action in May for stargazers will be the planetary trio. Start watching the movements of the planets with a challenge on May 10 just after sunset. Can you spot a young crescent Moon two degrees from Venus as they set in the west-northwest? It will be easier the next night, May 11, when the Moon has risen higher and is between Jupiter and Venus.

Jupiter and Venus met in 2010. This month's meeting will include Mercury.
Credit: ESO

Notice in mid-May, as Venus begins to close the distance with Jupiter, that Mercury suddenly enters the race. Mercury is moving faster than Venus and will bypass the planet just before they reach Jupiter. On May 23, Mercury begins to overtake Venus as the pair come within two degrees of each other, with Mercury shining at magnitude -1 and Venus at -3.9. May 24 is when the planetary trio officially begins as the three planets move within five degrees of each other. Mercury and Venus are still less than two degrees apart on this date. On May 25 the three planets are less than three degrees apart, with Jupiter to the upper left, Mercury to the right, and Venus below. May 26 finds the three planets still within three degrees of each other with their positions shifted slightly as Mercury has moved higher. On May 27, Jupiter and Venus will be side by side with Mercury just above. On May 28, Venus will be one degree to the upper right of Jupiter, with Mercury continuing above. The last night of the planetary trio occurs on May 29, as the three are in a line and still within five degrees. Mercury will be highest and will have dimmed since the beginning of the trio event to magnitude -0.5. Venus is next at magnitude -3.9, and Jupiter is below at magnitude -1.9. The three stretch apart thereafter and Mercury continues to dim as it climbs higher.

A few other noteworthy events in May include the Moon near Spica on May 21, near Saturn on May 22, and a Full Moon on May 25. A penumbral lunar eclipse occurs on the date of the Full Moon, but because the Moon only brushes the outer edge of the penumbra, no change to the lunar disk will be visible to stargazers.

As June opens, the planets that formerly formed a trio will be nearly evenly spaced with Mercury a little more than four degrees above Venus, which is a little more than four degrees above Jupiter. It seems that the planetary show is coming to an end. But wait! Even though Jupiter begins dropping to set with the Sun, Venus and Mercury are not done. First spot the crescent Moon to the left of Venus and Mercury on June 10. Then Mercury's movement begins to slow and Venus catches up to the innermost planet, putting the pair back to within about two degrees of each other from June 18-20. Venus, still at magnitude -3.9, will be to the right of Mercury, which will have dimmed to magnitude 1.3. Mercury heads back down toward the horizon in late June as Venus continues upward, entering the Beehive Cluster in Cancer in early July.

The third meteor shower of the quarter is the quietest and is known as the June Lyrids. The shower occurs over the weekend of June 15/16. June’s Lyrids only have a ZHR of 9.

The Moon passes close to Spica and Saturn on June 18, before heading toward its “Supermoon” status on the weekend of June 22/23. Both nights at moonrise the Moon should appear about 99-percent full. The Supermoon term is not one invented by astronomers but one that has gained status with the media and is therefore the buzzword that people will be talking about. Astronomers call it a Perigee Moon when the Moon reaches its closest to Earth (at 11:09 UT on June 23) while reaching full stage (which, in June, is just a few minutes later, at 11:32 UT. That's 7:09 a.m. EDT and 7:32 a.m. EDT). Therefore June's Full Moon will be the closest and largest of the year.

A Supermoon is also known as a Perigee Moon
Credit: Wojtek Wozniak

The Solstice, heralding summer in the Northern Hemisphere and winter in the Southern Hemisphere, is on June 21 at 5:04 UT. For most of the Earth’s population, warmer and shorter nights await, allowing stargazers to enjoy the outdoors into the evenings as the Milky Way arches overhead.

If you're confused by any of the astronomy terminology used on this page take a look at our: explanation of astronomy basics. Also, do visit our section on CCD Imaging to see what other amateur enthusiasts have managed to capture with their equipment. If there are any amateur astrophotographers out there who would like to exhibit their images on Astronomy Today do contact us.

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