Skywatch April 2017

Skywatch April 2017

April is always a good time to spot most of the famous constellations in one night in the islands; April 2017 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.


Your best chance to see Mercury this year

You probably still remember the brilliant light of Venus as it shone in the west at dusk these last many months; in fact Venus was our evening ‘star’ all the way from summer 2016 through St. Patrick’s Day 2017. Venus is now gone from the evening sky. That said, in late March and early April you’ll find Mercury shining like a fainter, but still striking, substitute. Look west around 7 p.m. from March 26 (when this article runs) through April 5 (around 7 p.m.) and you’ll find Mercury shining in the western sky, about ten degrees (about the width of your palm, held at arm’s length) above the west horizon. On March 26 it shines brightly at minus 0.7 magnitude; 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 go and land at the airport; you are seeing Mercury.


After April 5, Mercury appears both lower in the west at dusk, and dimmer, night by night; by April 9 it’s dropped down to second magnitude and barely emerges from dusk at 7:30 p.m. before it sets at 7:45 p.m.  After April 9, it’s gone.



Mars – not much of an evening star!

Once we lose Mercury around April 10, the only planet left in the west in Mars; but by April the red planet has faded so much that it won’t pop out at all at you.


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.  Mars starts off April against the faint stars of Aries the Ram.  However, on 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 king of the evening

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. A planet is generally brightest as well at opposition; Jupiter shines at minus 2.4 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 1/3 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.


Saturn comes around the evening sky

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 already back

Venus left our evening skies in mid-March and in fact passed between the earth and the sun on March 25. The planet was only off-view for about two weeks and is visible in the eastern sky before dawn by April 1. Venus is barely visible in early April, rising in the east around 5:40 a.m. a few minutes before dawn’s early glow wipes it out. 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, shining at around minus 4.5 magnitude.



Other April events 

Lyrid meteor shower

Every year, the longest drought between regular, repeating meteor showers is from early January (the Quadrantids) till mid-April (the Lyrids). The drought is over as of April 21 and 22, with the return of the Lyrid shower.

The best viewing times for the Lyrids will be from 12:01 am to dawn early on April 21, and from 12:01 am to dawn early on April 22, Hawai‘i Standard Time. The shower is active from April 16 – 25. While not one of the strongest showers, the Lyrids can produce up to twenty 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.


Easter Sunday

Easter is April 16 this year; Easter occurs on the first Sunday after the first full moon after the first day of spring.


April Sky Map – Southern Cross Watch

| Bishop Museum

Like all of our monthly maps, the April star map is good for 10 p.m. on April 1, 9 p.m. mid-month, and 8 p.m. on April 30.

As shown on the map, you can see the Southern Cross rising in the south southeast at ‘map time’; that is, 10 pm as April’s start, 9 p.m. mid-month, 8 p.m. by April 30.

In early April, the Cross will be due south just after midnight, and will set at 3 a.m. Mid-month, after rising at 9 p.m., the Cross will be due south at 11:30 p.m. and will set at 2 a.m.; by April 30, after rising at 8 p.m., look for the Southern Cross due south at 10:30 p.m. and down by 1 a.m.

The constellation hugs the horizon during its five-hour passage above the south horizon in the islands; make sure you have a flat horizon such as the sea to view it.

Moon phases (Hawaiian Time zone):

First Quarter: April 4
Full: April 11
Third Quarter: April 19
New: April 26


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2017-06-05T12:04:17+00:00Monthly Astronomy Article|