The month of April is named after aprilis, or aperture, which means opening, which is what our hemisphere is now doing as it slowly tilts more and more toward the sun and approaching the summer solstice.
There will be more than the usual share of celestial highlights this month as the earth below our feet is waking up once again. Mars will reach opposition, the moon will occult some of the stars in the Hyades cluster, the Lyrid meteor shower will happen, the two biggest and brightest asteroids will reach their oppositions, there will be an annular solar eclipse over Antarctica and there will be a total lunar eclipse visible for us right here.
Mars has doubled in brightness throughout the month of March, and it will reach its opposition on April 8. It will become as bright as the brightest star in the whole sky, which is Sirius in Canis Major at minus 1.4 magnitude. Covering 15 arc seconds of the sky, the red planet will get nearly as large as our other next-door neighbor, Venus.
Mars will rise at sunset in Virgo and not set until the sun rises. This will be its best opposition since 2007, but not nearly as good as the one on Aug. 27, 2003, which was its closest opposition in nearly 60,000 years. Mars was four times as bright back then and almost twice as large as it will get this month. The next really good and close opposition of Mars will happen on July 27, 2018.
The two largest and brightest asteroids, Ceres and Vesta, will reach their own oppositions on April 15 and 13, respectively. Vesta will even get bright enough to see without any optical aid and will reach 5.8 magnitude in Virgo, near Mars, this month. Then keep watching this pair until they get less than 1 degree apart on July 1, still in Virgo.
As you look for these two large asteroids safely orbiting in the belt between Mars and Jupiter, remember that the mass of just these two asteroids makes up about one-third of the mass of all the millions of asteroids in the belt. The four biggest asteroids make up about half the mass of all the asteroids. Be aware that there is a little man-made spacecraft orbiting between these two asteroids right now. Named Dawn, this unique spacecraft has a Xenon ion-propulsion drive that is 10 times more efficient than conventional chemical propellants. Dawn has already explored Vesta and it will reach Ceres by July of next year. Water vapor has already been detected on Ceres. Both of these asteroids could have become full-fledged planets if it weren’t for the inhibiting effects of Jupiter’s gravity.
The annual Lyrid meteor shower will peak on Tuesday morning, April 22. There will be only around 20 meteors per hour, and the moon will interfere after it rises around midnight.
The thin waxing crescent moon will occult several of the stars in the Hyades cluster, which makes up the face of Taurus the Bull, on the evening of Thursday, April 3. Use binoculars to watch the moon move in real time as it approaches and then covers up several of these stars.
Since we are in an eclipse season again, there will be an unusual annular solar eclipse visible over a tiny patch of Antarctica on April 29. The centerline will pass just south of Earth. Australia and parts of Indonesia will see a partial solar eclipse.
The last dramatic highlight of this April, which will be visible for us right here in New England, will be a total lunar eclipse. We haven’t had one visible for this part of the country since 2011. The moon will enter the umbra of Earth’s shadow at 1:58 a.m. and be completely engulfed in our shadow by 3:07 a.m. The total phase of this eclipse will end at 4:25 a.m. and the partial part of the eclipse will not end until 5:33 a.m.
That is technically what will happen, but actually experiencing such an event is quite another story. If you have never witnessed a total lunar eclipse before, an excellent way to better picture what is really going on as the moon slowly descends into our shadow is to remember what you are seeing as these subtle and ever-changing colors slowly unfold before your eyes.
You are really seeing the reflection of all the sunsets and sunrises on Earth taking place at the same time. The atmosphere of Earth acts like a giant lens in space, bending the sunlight back onto the moon and changing its color. The exact color will tell you volumes about the nature of our detailed structure of our atmosphere at the time. The darker the red, the more dust and/or pollution is in our atmosphere. The moon completely disappeared for a while during a total lunar eclipse in December 1991 due to all the volcanic ash and dust from Mt. Pinatubo, which erupted in the Philippines in June of that year.
Saturn begins the month rising around 10:30 p.m. and will end the month rising at 8:30 p.m., approaching its own opposition on May 10 when it will rise at sunset and remain in our sky all night long, like Mars will be doing on April 8. The ringed planet is in retrograde, or westward motion with respect to the fixed background of stars now in the constellation of Libra. It makes a great sight through telescopes because its rings are tilted open at 22 degrees and it is still getting brighter and larger in our sky as it keeps approaching Earth.
Venus rises a couple of hours before sunrise now in the eastern sky and shines at a brilliant minus 4.2 magnitude, which is 3 magnitudes or 16 times brighter than Mars. Venus is getting smaller in our sky but more illuminated by the sun as it drifts farther away from Earth.
Jupiter is still high and bright in the constellation of Gemini in the Winter Hexagon, but it is slowly fading as it travels farther away. It will be at eastern quadrature, 90 degrees east of the sun, on April 1. The king of the planets is moving in its normal, eastward motion now toward the constellation of Cancer. Watch the moon passing directly below Jupiter on the evenings of April 5 and 6.
• April 1. Comet Hale-Bopp’s closest approach to the sun was on this day in 1997.
• April 2. The first photograph ever of the sun was taken on this day in 1845.
• April 3. The waxing crescent moon will pass directly in front of several of the stars in the Hyades cluster in Taurus this evening.
• April 5. On this day in 1973 the Pioneer 11 spacecraft was launched. It stopped transmitting its signal back in late 1995. It is now more than 10 billion miles away, beyond the heliopause that marks the outer boundary of the influence of the solar wind into space.
• April 7. First-quarter moon is at 4:31 a.m.. On this day in 1991 the Compton Gamma Ray Observatory was deployed, about one year after the Hubble Space Telescope. The Compton telescope discovered about one powerful gamma ray burst from beyond our own galaxy per day. It was guided to crash over the Pacific Ocean about nine years later, on June 4, 2000.
• April 8. Mars is at opposition in the constellation of Virgo near the bright star named Spica.
• April 11. On this day in 1986 Halley’s Comet made its closest approach to Earth.
• April 12. On this day in 1961 the Russian Yuri Gagarin became the first human in space.
• April 13. The brightest asteroid, Vesta, is at opposition tonight in Virgo near Mars. At 5.8 magnitude it may even be visible without binoculars, but you should use binoculars to find it.
• April 15. Full moon is at 3:42 a.m. This is also called the pink, sprouting grass, egg or fish moon.
Ceres will be at opposition in Virgo today, but you will need binoculars to see it at magnitude 7.
A total eclipse of the moon will be visible, peaking at 4 a.m.
• April 16. Wilbur Wright was born on this day in 1867. The Wright brothers’ first heavier-than-air craft was flown in December 1903. It took us less than 66 years after that to get all the way to the moon.
• April 22. Last-quarter moon is at 3:52 a.m. The Lyrid meteor shower peaks this morning.
• April 23. Max Planck was born on this day in 1858. The smallest units of time and space possible in this universe were named after him. They are the Planck length and the Planck time.
• April 25. The Hubble Space Telescope was deployed on this day in 1990. It is still going strong 24 years later.
• April 28. Jan Oort was born on this day in 1900. The Oort cloud of comets was named after him.
• April 29. New moon is at 2:14 a.m. An annular solar eclipse will happen over Antarctica.