The Moon Sends a Happy Easter and Passover, Limited Lyrids, and Peering at Polar Objects!
Happy Easter and Pesach (Passover)!
Easter Sunday and Paesach (Passover) have an astronomical connection to the moon, with the Jewish Passover pre-dating the Christian Easter. Some believe that the full moon allowed for safer travelling by religious pilgrims of the time.
In 325 AD the Council of Nicaea determined that Easter should be observed on the Sunday following the first full moon that occurs after the vernal equinox, officially known as the Paschal Full Moon. The council fixed the equinox at March 21, but the astronomical timing of the equinox actually varies a little bit, and even occurs a full day early on Leap Years. This year, the equinox took place on March 20 at 6 pm EDT, and the full moon occurred that same day, at 9:43 pm EDT!
So why is Easter being observed on April 21 in 2019, instead of Sunday, March 24 (the Sunday after March’s full moon)? It’s because, as I stated above, the Council of Nicea fixed the equinox on March 21 — and that was the day AFTER the full moon this year.
In an added twist, if the post-equinox full moon falls on a Sunday, the following Sunday becomes Easter. The earliest that Easter can ever occur is March 22, which last happened in 1818, and won’t happen again until 2285! If a full moon happens before March 21, Easter will be delayed by a full lunar month, plus up to six days — on April 25. That will happen in 2038.
Passover is celebrated from the 15th through the 22nd of the Hebrew month of Nissan in the Jewish lunar calendar. It began with sundown last Friday night, which coincided with the first full moon after the spring equinox. In years when that full moon occurs early, Jewish religious leaders delay Passover by a month to ensure that spring-like weather conditions (warmer temperatures and flowers in bloom) have arrived in Israel. Last year’s Passover began about three weeks earlier, on March 27. The earliest that Passover can occur in our Gregorian calendar is March 25, which will next happen in 2089.
In Western Christianity, Easter sometimes precedes Passover by several weeks. The Eastern Orthodox Church uses the older Julian Calendar, and schedules Easter using the precise moment of the astronomical equinox and full moon as measured in Jerusalem (where the crucifixion and resurrection occurred). This ensures that Easter always occurs after Passover, since Jesus had traveled to Jerusalem to observe Passover. This year, Orthodox Easter will be observed on Sunday, April 28.
Lyrids Meteor Shower
The annual Lyrids meteor shower, derived from particles dropped by comet C/1861 G1 (Thatcher), runs from April 16 to 25 every year and peaks before dawn on Monday morning. This shower can produce up to 18 meteors per hour, with occasional fireballs. True Lyrids will appear to be travelling away from a point in space (the shower’s radiant) near the bright star Vega, which will be high in the eastern sky before dawn. Unfortunately, a bright, gibbous moon will wash out all but the brightest meteors this year.
You can start watching as soon as it’s dark. Even when the peak number occurs before dawn, some meteors will still be visible before midnight, too. Don’t bother to watch the radiant, since any meteors near it will have very soft trails. Bring a blanket and a chaise to avoid neck strain. And remember that binoculars and telescopes will not help; their fields of view are too narrow to see the long meteor trails. If you have friends or family along, don’t look at each other while chatting. Keep your eyes to the skies!
The Moon and Planets
After Friday’s full phase, the moon will wane and rise later (after midnight) with each passing day this week. As it moves into the latter stages of its monthly orbit around the Earth, the moon will become visible in the eastern predawn sky and will pay a visit to some of the bright planets that currently reside there.
When the bright planet Jupiter rises in the southeastern sky at about 12:15 am local time on Tuesday morning, it will be positioned 3 finger widths to the lower left of the waning gibbous moon. The moon and planet will cross the sky together for the rest of the night, eventually moving to a point in the lower southwestern sky at sunrise. The duo will make a lovely photo opportunity when composed with an interesting foreground landscape! Jupiter will follow the same schedule, even after the moon moves away from it.
In the southeastern pre-dawn sky on Thursday morning, the almost last quarter moon will land less than 3 finger widths to the right of yellowish Saturn, which will rise after 2 am local time. If you are outside a little earlier, look for the Teapot-shaped stars of Sagittarius (the Archer) positioned about a fist’s diameter to the lower right of the ringed planet and moon. The pairing will fit nicely into the field of view of binoculars, and make another nice photograph. Half a day later, at 13:00 GMT, observers in Eastern Australia and New Zealand will see the moon pass over (See what I did there?), or occult, Saturn.
On Friday evening, the moon will officially reach its last quarter phase, when it will be half illuminated, on its western (our left-hand) side. Remember that phases of the moon are controlled by the angle in space made by the three objects — sun, Earth, and moon. The rotation of the Earth, and who gets to see the phases when they happen, is on a separate schedule.
Mars will continue to be easily visible for an hour after dusk every evening this week. But the later spring sunsets mean that Mars will set in the west just before midnight local time. Once the sky has darkened, look for Mars as a medium-bright, reddish pinpoint of light sitting less than one-third of the way up the western sky. Mars has been slowly shrinking in size and brightness as we increase our distance from it little-by-little. The bright reddish star Aldebaran will be sitting about a palm’s width below Mars this week. Don’t confuse them — it’s brighter than Mars.
On Friday evening, Mars’ orbital motion will carry it closely past a clump of three open star clusters (NGC 1746, 1750, and 1758). If your sky is dark enough, your binoculars might show a concentration of stars just to Mars’ lower left. A backyard telescope will show them better, but your optics will probably flip or invert the view — so check all around Mars for them. The best time to view should fall around 10 pm local time, when the sky is darker and Mars is higher.
During this week, the very bright planet Jupiter will rise over the southeastern horizon a little bit after midnight local time. By 6 am, Jupiter will remain visible in the lower part of the brightening sky, over the south-southwestern horizon. Starting next Sunday, Jupiter will begin to rise before midnight — on its way to become a prime target for star parties this summer! Yellowish Saturn will be sitting about 2.5 outstretched fist diameters to the left of Jupiter from 2 am local time until dawn. It, too, will add to your summer stargazing fun!
Mercury and Venus are together in the eastern sky just before sunrise this week, but they are surrounded by the dawn twilight, making much dimmer Mercury a challenge to find. Venus will rise at about 5:30 am local time. To help you find Mercury, Venus will be positioned about four finger widths to the upper right of the swift innermost planet. Both planets are swinging towards the sun and will soon disappear in solar conjunction.
Observing Ideas for This Week
Here’s an easy target in the northern sky. Polaris marks the tip of the handle of the Little Dipper, the asterism we also know as the constellation Ursa Minor (the Little Bear). In late April after dusk, the rest of the Little Dipper extends sideways to the right from Polaris, and curves strongly upwards towards the Big Dipper.
The magnitude 2.06 star at the outer edge of the Little Dipper’s bowl (and closest to the Big Dipper) is slightly dimmer than Polaris and fairly easy to see. This medium-cool, reddish star is named Kochab. The other five stars of the constellation may be too dim to see from the city, but binoculars will reveal them. Don’t forget that Polaris has a dimmer companion star tucked in close to it. A backyard telescope can see them both. As the sky rotates due to Earth’s spin, that little star revolves around Polaris.
The two dippers flank the tail of the long and winding constellation of Draco (the Dragon). It really looks like a dragon when you follow its stars!
Shortly after the sun sets in the west, the very bright star Arcturus will appear in the eastern sky, heralding the summer stargazing season. Arcturus is the fourth brightest star in the entire sky. Its name means “bear watcher” because the star follows Ursa Major around the northern sky. (The word Arctic, home of the polar bears, comes from the same root, the Greek word arktos.)
Four globular star clusters, spherical balls of millions of stars, populate the sky above Arcturus. At visual magnitude 6.2 and within reach of binoculars, Messier 3 is the brightest, and sits nearly 12 degrees (a generous fist’s diameter) above Arcturus. The dimmer NGC 5466, sometimes called the Snowglobe Cluster, sits less than a palm’s width to the upper left of Arcturus. Another bright globular designated Messier 53 sits 1.5 fists to the upper right of Arcturus and only a finger’s width below the star Diadem, the brightest star in Coma Berenices (Berenice’s Hair). NGC 5053, the dimmest of the four globulars, is located 1 finger’s width below Messier 53.
Above those globular clusters is the realm of the spring galaxies, in Virgo (the Maiden.) But that’s another story…
Astronomy Skylights for the week of April 21st, 2019 by Chris Vaughan.
Keep looking up, and enjoy the sky when you do. I love questions and requests — so, send me some!