The month of April is named for aprilis, which means opening. That is what part of the northern hemisphere of the earth is starting to do this month. Our hemisphere has now tilted more towards the sun as the days will continue to get longer and longer until the summer solstice.
There are many interesting highlights to enjoy this month as our long, cold and snowy winter finally begins to soften its grip on us and our part of the earth begins to reawaken once again in its endless cycles. There will be nice conjunctions of the moon with Venus, and then with Jupiter, a Mercury and Mars conjunction, Venus giving us a grand tour of the constellation of Taurus, the Lyrid Meteor Shower, and a total lunar eclipse.
That is quite a full month of exciting highlights, but every month has unique happenings that will never happen exactly the same way again. There are certainly patterns to observe, like the moon passing fairly close to each of the planets each month because they are all on the same path though the sky, called the ecliptic, and all the meteor showers occurring at the same time each year, and the saros cycles of similar characteristics of lunar and solar eclipses, but each individual event is always different and very interesting to watch, enjoy, and understand.
Brilliant Venus continues to brighten in our sky as it catches up with Earth in its faster orbit around the sun. It will start this month 78 percent illuminated by the sun, but it will be only 68 percent illuminated by the end of April. As our sister planet travels through Taurus this month, climbing a little higher each evening, it will nicely draw attention to some interesting features and lead you on an educational and enlightening tour of this familiar constellation. It will start with the Pleiades, also known as the seven sisters or Subaru in Japanese, an open cluster of about 500 stars located about 400 light years away and about 100 million years old, then the Hyades, and open cluster of about 200 hundred stars about 130 lights years away and about 600 million years old, or eight times younger than our sun, and then the orange giant star called Aldebaran, which marks the fiery eye of Taurus the Bull. This orange, spectral type K5 star is about 65 light years away, twice as close as the Hyades that is seems to belong to, and fully 40 times the diameter of our sun. If you could place Aldebaran in our own sky, it would cover 20 degrees, or two fists at arm’s length, and it would almost include the orbit of Mercury. Aldebaran means follower in Arabic, since it seems to be following the Pleaides, and it is one of the four royal stars of ancient Persia. The other three are Regulus, Antares, and Fomalhaut. They are all equally impressive and entirely unique. The first exoplanet directly visible in telescopes was discovered around Fomalhaut seven years ago.
The Hyades star cluster is actually related to the Beehive cluster in Cancer, also known as M44. The motions of the stars in these two clusters can be traced back to a common origin in the sky, almost like tracing individual meteors back to one point during a shower, called the radiant. They have other factors in common, like age, metallicity (heavier elements present) and proper motion through our galaxy. The Hyades form a giant oblate spheroid in space, similar to the shape of the earth, most of which fits into a diameter of about 20 light years across.
As a nice bonus, the slender waxing crescent moon will also travel through Taurus, albeit at a much quicker pace, from the 19th through the 22nd, which is also Earth Day. Notice that Mars and Mercury will form a close conjunction very low in the western sky during that time 45 minutes after sunset.
Jupiter will end its retrograde motion towards the Beehive on April 8, stopping five degrees short of this relative of the Hyades cluster. Then the King of the planets will resume its normal eastward or prograde motion in relation to the fixed background of stars for the next eight months, heading back into Leo. Be aware that Jupiter is heading for a great conjunction with Venus on July 1.
Saturn continues to rise a little earlier each evening and it will be rising by 9:30 by the end of April. It will reach opposition on May 22 when it will rise exactly at sunset. Notice that the ringed planet is already in retrograde motion, having ended its direct motion on March 14, which was also the once in a century Pi day when the date and time reflects the first 10 digits of this irrational number, and Albert Einstein’s birthday.
The Lyrid meteor shower peaks on the morning of Wednesday the 22nd. Caused by Comet Thatcher, which only orbits the sun once every 415 years, this shower is not usually too spectacular, only producing about 20 meteors per hour under good conditions. However, there are always exceptions and any reason is a good one for getting out under the stars to enjoy and try to understand their vast beauty and power.
The third total lunar eclipse of this very rare tetrad of four total lunar eclipses that also fall on important Jewish holidays will happen on Saturday morning, April 4. This is only the eighth such tetrad in the past 2,000 years. We are not well placed here on the East coast to see much of this rare event, but we can catch a little of it just before the moon sets in the morning as the sun rises. It will only have entered the penumbral shadow at that point, so you will need binoculars to discern any change at all on the face of the moon. We also missed the total solar eclipse that happened just a few hours before spring started. It occurred at a super moon and was very spectacular over the Faroe and Svalbard Islands, located halfway between Norway and the North Pole.
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April 4: Full moon is at 8:05 a.m. EDT. This is also called the Grass, Egg, Pink, or Fish Moon. The total lunar eclipse will happen today just before sunrise.
April 8: Saturn will be close to the waning gibbous moon this morning.
April 10 to 12: Venus will be close to the Pleiades in Taurus.
April 11: Halley’s Comet was closest to Earth on this day in 1986. Last quarter moon is at 11:44 p.m.
April 12: Yuri Gagarin became the first human in space on this day in 1961.
April 16: Wilbur Wright was born on this day in 1867. It was only 66 years after the Wright Brother’s made their first very tentative powered flight in 1903 that we traveled all the way to the moon.
April 18: New moon is today at 2:57 p.m.
April 19: Mercury and Mars are visible close together low on the western evening horizon. You may need binoculars to see them.
April 20: The slender waxing crescent moon joins Venus by the Pleiades this evening.
April 22: The Lyrid Meteor Shower peaks tonight.
April 23: Max Planck was born on this day in 1858. He was one of the founders of quantum mechanics that completely redefines what really happens at the very small scale of the universe. The shortest distance in the known universe is called the Planck length, which is 10 to the minus 35 meters. The shortest amount of time, 10 to the minus 43rd second, is called the Planck time. That is the time it takes light to travel the width of a proton. That is also as far back as any humans can possibly see after the instant on the Big Bang.
April 24: On this day in 1970 China becomes the fifth nation to launch a satellite.
April 25: The Hubble Space Telescope was deployed on this day in 1990. First quarter moon is at 7:55 p.m. EDT.
April 30: Mercury makes its best evening apparition of this year this week and next.
— Bernie Reim is an amateur astronomer and teaches astronomy lab courses at the University of Southern Maine.
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