SKY GUIDE: This map represents the night 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 mid-month, and at 8:30 p.m. at month’s end. Venus and Mars are shown at their mid-month positions. 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 Seth Lockman

The month of April is named after the word aprilis, which means aperture or to open. That is what this part of the earth in the northern hemisphere will start to do later this month, the first full month of spring. The grass will start to get green, some flowers will come out and some trees will blossom and begin to sprout tender young green leaves once again as the cycle of life continues and nature springs forth again in rebirth.

The heavens above are also changing as they do on a regular basis regardless of the seasons, The reappearance of certain constellations along with the loss of others are associated with spring in the northern hemisphere. The winter hexagon is sinking lower into the western sky even as Vega in Lyra at the top of the summer triangle will reappear once again low in the eastern sky by 10 p.m. Virgo climbs higher along the ecliptic as Corvus the Crow and Crater the Cup also rise higher below Virgo and just above Hydra the mythical water snake, the largest constellation in the whole sky covering 102 degrees whose head is in the northern celestial sphere and whose tail stretches all the way into the southern sky.

Now that the nights are getting shorter and warmer, it will become more inviting to go outside and partake in the many highlights being offered in the sky this month. We will have a nice planetary trio of Mercury, Venus, and Mars in our western sky at dusk, Saturn in the morning sky, and the first good meteor shower since the Geminids way back on Dec. 13. That will be the Lyrids, on April 22, which is also Earth Day. Caused by Comet Thatcher, you can expect 15 meteors per hour from a dark sky site. That is near the new moon this month, so the conditions will be favorable as long as it is clear.

Venus will climb a little higher each night and set a little later. It will be just a few degrees to the left of the Pleiades star cluster in Taurus on April 11. The Pleiades is an open star cluster consisting of about 500 stars located about 400 light years away. So the next time you look at this little star cluster, also known as the Seven Sisters, or Subaru in Japanese, remember that the light you are now seeing actually left its source about the same time that Galileo first pointed his telescope into the sky in 1609.

Then look about 15 degrees below brilliant Venus and the Pleiades and you will spot Mercury. It is at its greatest elongation from the sun that night on April 11 and it will shine at magnitude minus 0.2. That is 4 magnitudes, or about 40 times fainter, then Venus just above it. Mercury will set about an hour after sunset. Only one week later our first planet will be much lower in our sky and it will be 5 times fainter.

Watch as a slender waxing crescent moon appears just above Mercury and below the Pleiades on April 21, and then shows up just above the Pleiades and below Venus on Earth Day, April 22. The moon appears to travel 13 degrees eastward through the constellations each day. It will be about 7 degrees above Venus on April 23.

Mars is well past its prime of late last year, but it is still a fairly bright orange object, brighter than most stars at 1.2 magnitude. Look for it moving in direct or eastward motion through Gemini and setting around midnight. The waxing crescent moon will join Mars just below Castor and Pollux, the mortal and immortal twins in Gemini, on April 25.

You can see Saturn low in the eastern morning sky before sunrise, but it will not get much higher and brighter until May and June. We now lost Jupiter into the sun’s glare in the evening sky after its wonderful close conjunction with Venus one month ago. Jupiter will reappear low in our eastern morning sky by the middle of May.

The annual Lyrid meteor shower is created by the earth passing through the debris trail of Comet Thatcher which orbits the sun every 415 years with its next expected return in 2283. All of these meteors will appear to emanate from a point in the sky in Lyra to the right of Vega near Hercules. That is called the radiant. You should look just above and below the radiant to see the most meteors, but you can see them anywhere in the sky and trace them back to this point.

APRIL HIGHLIGHTS

April 1: In 1997, Comet Hale-Bopp was at perihelion. That was a once-in-a-lifetime comet that was visible in our sky for a whole year, stretching across nearly a quarter of our sky when it was at its best.

April 2: The waxing gibbous moon is near Regulus this morning low in the western sky in Leo.

April 5: Full moon is at 11:36 p.m. This is also called the Pink, Grass, Egg or Fish moon.

April 7: In 1991, the Compton Gamma Ray telescope was launched. That was part of a whole family of four types of space telescopes that would look at the sky in a wide range of wavelengths from gamma rays, X-rays, visible light and infrared light.

April 10: The waning gibbous moon is near Antares in Scorpius tonight.

April 11: Venus is near the Pleiades tonight. Halley’s Comet was at perigee in 1986. It will next return in 2062.

April 12: Yuri Gagarin became the first human to orbit the earth in 1961. John Glenn became the first American to orbit about a year later, on Feb. 20, 1962.

April 13: Last quarter moon is at 4:13 a.m.

April 14: Mars is near a bright star in Gemini tonight.

April 16: The moon is just below Saturn this morning low in the east-southeastern sky just before sunrise.

April 19: New moon is at 11:14 p.m. A rare hybrid partly annular and partly total solar eclipse will occur over Australia and Indonesia.

April 22: The moon is near Venus and the Pleiades tonight. The Lyrid meteor shower peaks tonight into the morning of April 23.

April 25: The Hubble Space Telescope was deployed in 1990 by the Space Shuttle Discovery. That was STS 31. The whole space shuttle program would end in July of 2011 with STS 135. The HST is still working fairly well 33 years and over 1.5 million great images later.

April 27: First quarter moon is at 4:21 p.m. It will be just 4 degrees above the Beehive star cluster in Cancer tonight.

April 30: Frances Wright, an American astronomer who taught celestial navigation to naval officers at Harvard and wrote three books on that subject was born in 1897

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