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 midmonth, and at 8:30 p.m. at month’s end. 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 for the Latin word aprilis, which means to open. That is what some buds and flowers will be starting to do later this month. Look for many other terrestrial signs of spring, including the spring peepers, skunk cabbages, and some early bird species returning to New England. Much more of that will happen next month, but it is interesting to try to catch the first signs this month, the first full month of spring.

We can also open our own views to the sky much more this month as it will get warmer even as the nights are already getting shorter. There will be several great highlights to entice us outside at night this month beyond just the warmer weather. These include a very close conjunction of Venus and Jupiter, all the planets visible and bunched fairly close together in the morning sky except Mercury – which makes its best appearance for the year later this month in the evening sky – the first good meteor shower since January, and another comet which might even become brighter than NEOWISE was in July 2020.

On the last morning of this month, Venus and Jupiter, our two brightest planets, will form their closest conjunction from our perspective until 2039. They will be less than half a degree apart, which is the width of the full moon. Your index finger at arm’s length covers about one degree of the sky.

You could fit both of these planets into the same field of view in a telescope, which would also enable you to see the four large Galilean moons, Ganymede, Io, Callisto, and Europa. Notice that Venus is just over six times brighter than Jupiter. The Juno mission that NASA launched to this planet in August of 2011 and arrived on July 4, 2016 has already completed its scheduled 35 highly elliptical orbits of 53 days each last summer, but it was extended to September of 2025. This ingenious little spinning solar-powered spacecraft is the fastest craft humans have ever created. It is constantly zipping around Jupiter at 42 miles per second, just over twice as fast as the earth is orbiting the sun. Juno has discovered many new things about this planet already and will most likely discover much more in the next three years.

Juno has to plunge through the powerful plasma torus of charged particles trapped in the planet’s strong magnetic fields for a few minutes each orbit. It also plunges through the even more powerful fields of the flux tube that connects Jupiter with Io, but it has not been damaged by that because it is diffuse enough. Io is the most volcanically active place in our whole solar system. It constantly pumps out one ton of particles every second, most of which get trapped in this flux tube.

Saturn and Mars will also form a very close conjunction in the morning sky on April 4. They will both rise around 5 a.m., closely followed by Jupiter. Then keep watching as Venus and Mars continue to trek eastward through Capricorn, while distant Saturn barely moves. Then the waning crescent moon will pass near all of these planets low in the morning sky from April 24 through April 27. Notice that orange Mars and golden Saturn are about the same brightness and they are each about 100 times fainter than brilliant Venus to the left of the pair.

That leaves Mercury as the lone evening planet since the other four bright planets have long since migrated to the morning sky after gracing our evening skies for much of last year. It will make its best appearance for the whole year later this month and it will be just a few degrees to the right of Uranus in Aries below the Pleiades on April 17, but you would need binoculars to see that.

The first good meteor shower since the Jan. 4, Quadrantids, will happen on Friday, April 22, which is also Earth Day. The first Earth Day didn’t start until 1970, just after we obtained our first comprehensive and distant view of Earth on our way to and back from the moon. That new perspective of our precious planet also sparked some very necessary and overdue legislation like the Clean Air and Clean Water Act. In contrast, Comet Thatcher was discovered back in 1861 and has probably been creating these meteors in its debris trail that we pass through on this same day every year since long before that date.

You can expect about 18 meteors per hour from the Lyrids from a good dark sky sight on the night of Friday, April 22. A nearly last quarter moon will rise around midnight, spoiling the show somewhat, but don’t give up. I saw 21 Geminids with the moon still up on Dec. 13 of last year. Comet Thatcher only orbits the sun once every 415 years. They will all emanate from their radiant in Lyra, just to the right of the bright star named Vega, which was the star Carl Sagan wrote about in his book “Contact.”

There is another very promising comet now in our skies that could potentially become brighter than NEOWISE was in July of 2020. NEOWISE reached about first magnitude, or 100 times brighter than the faintest object you can see with the unaided eye. It also sported a nice tail stretching over 10 degrees of the sky below the Big Dipper, making it the brightest comet since Hale-Bopp in 1997.

APRIL HIGHLIGHTS

April 1: New moon is at 2:24 a.m. In 1997, Comet Hale-Bopp, a very bright once-in-a-lifetime comet, made its closest approach to the sun. Comet Hyakutake became nearly as bright just one year earlier, also qualifying as a once-in-a-lifetime comet.

April 4: Mars passes half a degree south of Saturn this morning.

April 6: The moon passes near the dwarf planet Ceres this morning in Taurus this morning.

April 7: The Compton Gamma Ray observatory was launched in 1991. This was one of a family of four great space telescopes, each designed to study the skies in a different wavelength. Compton discovered about one extremely powerful gamma ray burst every day during its nine short years of work. The Hubble Space Telescope is still working 32 years after its own launch having given us nearly two million great images that completely revolutionized our understanding of the cosmos.

April 9: First quarter moon is at 2:48 a.m.

April 11: In 1986 Halley’s Comet reached perihelion with the sun. I first saw his comet on Nov. 11, 1985, exactly 329 years after Edmund Halley’s birth in 1656.

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

April 16: Full moon occurs at 2:55 p.m. This is also called the Pink, Fish, Grass or Egg Moon.

April 22: The Lyrid meteor shower peaks today, Earth Day.

April 23: Last quarter moon is at 7:56 a.m.

April 24: The moon passes 5 degrees south of Saturn this morning.

April 25: In 1990 the Hubble Space Telescope was launched.

April 26: The moon passes near Venus this morning.

April 27: The moon passes near Jupiter this morning.

April 29: Mercury is at greatest eastern elongation at 21 degrees east of the sun this evening.

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