The month of April is named after aprilis, which means aperture or opening. That is what this part of the northern hemisphere will be doing as it warms up consistently, and a hint of green will return toward the end of this first full month of spring.

There will be plenty of interesting highlights this month as we open ourselves to what the spring skies have to offer us. There will be a very close conjunction of Saturn and Mars in the morning sky, and then a nice conjunction of the slender waxing crescent moon with Venus and the Pleiades in Taurus by the middle of April. To top it off, the first good meteor shower since the Geminids last year will happen on Sunday night the 22nd, which is also Earth Day. They are called the Lyrids and are caused by Comet Thatcher.

SKY GUIDE: This chart represents the sky as it appears over Maine during April. The stars are shown as they appear at 10:30 p.m. early in the month, at 9:30 p.m. at midmonth and at 8:30 p.m. at month's end. Jupiter is shown in its midmonth position. To use the map, hold it vertically and turn it so that the direction you are facing is at the bottom. Sky chart prepared by George Ayers

Mars has been approaching Saturn fairly rapidly each morning. The red planet will finally appear to catch and then overtake the ringed planet on the second day of this month in Sagittarius and then continue eastward into the next constellation, Capricorn. They will be just over one degree apart when that happens. Then, keep watching as a last-quarter moon joins the pair on April 7. The best time to see this would be about an hour before sunrise as dawn begins to break.

I was able to see the nice morning lineup of three bright planets and three bright stars along with a waning crescent moon about an hour before sunrise last month. The earth shine reflected back to us from the moon added a nice three-dimensional sense of depth to this lovely string of celestial pearls suspended over the Atlantic Ocean as dawn was breaking. A similar sequence will occur again in the morning sky this month, but Mars and Saturn will have switched places from our perspective in their constant motions around the sun.

Then, continue along this string and you will encounter Antares, an orange supergiant in Scorpius that is 700 times the size of our own sun. Its very name means “rival of Mars,” and it is about the same brightness and color as Mars is now. If you could place Antares where our sun is in the sky, its outer surface would engulf our solar system out to beyond the orbit of Mars around our sun.

Jupiter begins the month rising three hours after sunset, but ends the month rising just a half-hour after sunset. The king of the planets continues to get a little brighter and closer, and bigger each evening and is getting very close to its best for the year. That is called opposition and will happen in early May. Notice that Jupiter is already tracing its retrograde or westward loop in our sky in Libra now. That westward motion will not end until two months after its opposition.

Mercury has left Venus in the evening sky and switched back to the morning for most of this month. However, it will be a low appearance for our first planet as it only rises about an hour before sunrise and never escapes the twilight low on the eastern horizon. Mercury is now moving from inferior conjunction with the sun to its greatest western elongation at 27 degrees west of the sun by the end of the month. Through a telescope, you can watch it get more illuminated even as it gets smaller in our sky.

Venus continues to get higher and set later in our evening sky as the month progresses. Our sister planet will not reach its highest point for this appearance until June, when it will not set until 10 p.m. Notice that a slender waxing crescent moon will join Venus in the evening sky on April 17 and then continue into Taurus past the Pleiades and the bright orange giant star Aldebaran in the Hyades star cluster, which marks the face of Taurus the bull.

The Lyrid meteor shower peaks on Sunday morning the 22nd, which is also Earth Day. If you wait until the last quarter moon sets around midnight on the 21st, you could see about 10 to 15 meteors per hour. That is not a great rate, but it is better than the background rate of three or four per hour on any clear night of the year without a particular shower taking place.

All of the Lyrids will appear to emanate from the constellation of Lyra the Harp, close to its border with Hercules. Caused by Comet Thatcher, this is the oldest recorded meteor shower. It was first recorded 2,700 years ago in China. The Lyrids are caused by tiny, sand grain-sized pieces of this comet entering our upper atmosphere at about 70 miles high at around 35 miles per second. They are the second-fastest meteors after the Leonid Shower in November. There is an outburst of nearly 100 meteors per hour about every 30 years, but one is not expected this year. Its parent comet has a long orbit around the sun of 415 years, and its last close pass was in 1861.

APRIL HIGHLIGHTS

April 1: In 1997, Comet Hale-Bopp made its closest approach to the sun, which is also called perihelion. This was a great comet that hung around for almost a year and covered nearly a quarter of the sky when it was at its best. The year before, another once-in-a-lifetime comet made a close approach to Earth. That one was called Comet Hyakutake.

April 2: Mars will hover just one degree below Saturn this morning in Sagittarius, one hour before sunrise. Then, continue scanning to the west to see the nearly full moon and then Jupiter hanging in Libra the Scales.

April 7: Watch the waning gibbous moon directly above Saturn and Mars one hour before sunrise in the eastern sky. Then watch it the next morning and you will see that it is 12 degrees farther east, or to the left of this pair of close planets. The Compton Gamma Ray observatory was launched on this day in 1991. Part of a whole family of four great space telescopes, this one studied the sky in the most energetic of all wavelength of light, gamma rays. It did discover about one new gamma ray burst randomly appearing in our sky each day during its nine-year life in orbit. Those are extremely powerful events caused by neutron star mergers or hyper novae explosions. NASA had to deorbit this wonderful space telescope on June 4, 2000, after gathering great data and helping us make new discoveries, and expanding our knowledge of the invisible gamma ray universe after one of its three gyroscopes failed.

April 8: Last-quarter moon is at 3:19 a.m.

April 11: In 1986, Halley’s Comet made its closest approach to Earth. I saw it several times during that apparition, first spotting in on Nov. 8, 1985, exactly 329 years after his birth.

April 12: In 1961, Yuri Gagarin became the first human to orbit the earth. John Glenn became the first American to orbit less than one year later, on Feb. 20, 1962.

April 15: New moon is at 9:58 p.m.

April 17: Watch the waxing crescent moon directly below Venus this evening. Then watch the moon just below Aldebaran in the Pleiades the next evening.

April 18: Saturn rises in the east at around 1 a.m. Saturn is now at aphelion, the farthest it has been from the sun since 1959 at just over one billion miles away.

April 22: The Lyrid meteor shower peaks this morning. The moon passes directly below the Beehive open star cluster in Cancer the crab this evening. First-quarter moon is at 5:47 p.m.

April 25: The Hubble Space Telescope was deployed on this day in 1990. It is still operating efficiently, more than one million great pictures later.

April 29: Full moon is at 8:59 p.m. This is also called the Pink, Fish, Grass or Egg Moon.

April 30: Frances Wright was born in 1897. She was a Harvard astronomer who taught celestial navigation to naval officers and wrote three books on celestial navigation.

Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.

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