Constellations, planets, Lyrids show off in April

April is always a good time to spot most of the famous constellations in one night in the islands. April has the added bonus of being able to catch all five of the naked-eye planets for at least part of the month. The Lyrid meteor shower returns on April 21 and 22, this year with good dark skies.

Planets a plenty

In late March and early April you’ll find Mercury shining like a fainter, but still striking, substitute for now-vanished Venus. Look west around 7 p.m. from today through April 5 (around 7 p.m.) and you’ll find Mercury shining in the western sky, about 10 degrees (about the width of your palm, held at arm’s length) above the west horizon. It fades a little, night by night, but even by April 5 it’s still shining at a bright 0.9 magnitude. Here in late March and early April you’ll have about an hour to spot Mercury before it sets just before 8 p.m.

They say one person in a thousand sees Mercury and knows they’re seeing it, and this will be the best time this year to join the club! Helping matters: there are no other bright stars or planets near Mercury during this early spring dusk appearance; so if you spot a bright dot low in the west between 7 and 8 p.m., from late March through April 5, and if that dot does not land at the airport, you are seeing Mercury.

Once we lose Mercury around April 10, the only planet left in the west in Mars. What Mars lacks in brightness, it gains in consistency; it acts and looks much the same all month. The planet emerges in the west around 7:30 p.m., about 20 degrees above the west horizon, and sets around 9 p.m. all month. Mars is already down to 1.45 magnitude, not brighter than an average bright-ish star.

What does change about Mars as the month goes on: the backdrop. From April 19 through 22, it will be just to the left of the famous Pleiades cluster, which will make it easier to make sure you’ve found the planet Mars (i.e. find the Pleiades and look left for the faint orange dot). Look for a very slender crescent moon just below Mars on April 27 and just above Mars on April 28.

Jupiter is officially in opposition on April 7; on that day there is a straight line between the sun, earth and Jupiter. A planet in opposition rises in the east at dusk, is high overhead at midnight and sets at dawn in the west. It will be particularly bright this month.

At the start of April, Jupiter rises in the east at 7 p.m. just as it gets dark, is due south at 1 a.m. and sets in the east at dawn. By the middle of the month it’s about a quarter of the way up in the east at dusk, high overhead at midnight, and down in the east around 5:45 a.m. By April 30, the king is about one-third of the way up in the east at dusk, is high overhead at 11 p.m. and sets by 4:45 a.m.

Jupiter pops out dramatically; at minus 2.5 magnitude, it’s 25 times brighter than the blue-white star Spica, which is just under a palm’s width to Jupiter’s left.

Look for the just-about full moon next to Jupiter on April 9 and 10.

In early April, Saturn rises in the south-southeast at midnight and is due south by dawn. By end of the month Saturn rises by 10:15 p.m., is due south at 3:45 a.m., and is about halfway down the western sky at daybreak. The planet shines at 0.5, as bright as a good bright star, and has a distinctive yellow-white hue.

Since Saturn is not as brilliant as Venus or Jupiter, it does not pop out like those two planets do. A good guide this year is Scorpius the Scorpion, known here as Maui’s Fishhook; if you find that big bold constellation first, Saturn is to the left of the Scorpion. Saturn is in fact about 20 degrees (the width of two palms) to the left of the bright, ruddy star Antares, the heart of the Scorpion.

Venus is visible in the eastern sky before dawn. By the end of April, Venus rises by 4 a.m. and is about 20 degrees above the eastern horizon by dawn. Since Venus just passed between the Earth and the sun, it’s still really close to us and therefore bright.

Other April events

>> Lyrid meteor shower: The best viewing times for the Lyrids will be from 12:01 a.m. to dawn early on April 21 and 22. The shower is active from April 16 to 25. While not one of the strongest showers, the Lyrids can produce up to 20 meteors per hour. Last year, the Lyrids coincided with a bright moon; this year, the conditions are the best viewing conditions for any meteor shower of this spring or summer. The moon, a slender, waning crescent, will provide very little interference this year.

To look for the shower, find a dark location and get comfortable; search the skies anytime from 12:01 a.m. to dawn, early on April 21 or 22. The constellation of Lyra, where the shooting stars seem to radiate from, rises in the east just before midnight; but keep an eye on the entire sky, since meteors can appear from any direction.

As with all meteor showers, the viewing is better after midnight, since after midnight your part of earth is facing into the cloud of comet or asteroid debris whose particles hit our atmosphere and burn up from friction. The Lyrids come from the debris of Comet C/1861 G Thatcher.

Hawaii Sky Map: April 2017 by Honolulu Star-Advertiser on Scribd

Mike Shanahan is director of education, exhibits and planetarium at Bishop Museum. Click here for more information.