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June is a great month for astronomy in the Hawaiian islands.
As usual, June is the last chance to see the Southern Cross from the islands until December. In addition, and special to June, Jupiter and Venus will appear to draw closer night by night in the western evening sky through the month, heading for a beautifully close gathering of the two brightest celestial dots on the last day of the month.
Throughout June, look for Venus appearing in the west about 20 minutes after sunset. Shining at minus 4.4 magnitude, Venus looks as bright as an airplane. Throughout June, as it gets dark enough to see it, Venus will be about athirdofthewayupinthe west. The planet sets around 10p.mthroughoutthe month.
Like Venus, Jupiter will also appear in the western sky at dusk. Jupiter will be more than halfway up the western sky as it gets dark, and will be about 20 degrees above brighter Venus. That’s the width of two palms held at arm’s length.
In early June, Jupiter sets in the west at 11:30 p.m., about 90 minutes after Venus. Jupiter shines at minus 2 magnitude, 10 times dimmer than Venus but brighter than any other dot in the sky.
Each evening in June, Jupiter will seem a little lower in the sky at full darkness; by mid-month it will be halfway up in the sky, and only about 10 degrees above Venus. By the end of the month, side-by-side with Venus, Jupiter will be only about a third of the way up in the west at dusk and will set by 10 p.m.
Our June star map shows the positions of Jupiter and Venus in the middle of the month. In the real sky, the pair will be farther apart in early June, and of course closer together at the end of June.
Particular nights to note include:
>> June 19: On this evening, look west at dusk and you will see a slender crescent moon just below Venus, as Jupiter blazes 5 degrees above Venus.
>> June 20: On this night, the moon will be a bigger crescent and will have moved up to the left of Jupiter, the upper planet of the pair.
From June 21 to 30, as the two planets draw closer in the sky, you should be able to tell a change in their positions from each night. The twoplanetswillremainclose to each other in July, so if you miss this close gathering on June 30, there will be lots of nights still to catch the gathering. However, the two planets will be lower in the sky with every July dusk, and both will vanish into the sun’s light by early August.
OTHER PLANETS
Saturn is visible all of June in the early evening sky. In early June the planet emerges about one-quarter of the way up in the southeast as it gets dark, is halfway up in the south around midnight and sets in the west-southwest as day breaks. By the end of the month, Saturn appears halfway up in the southeast at dusk, is due south at
10 p.m. and sets in the west-southwest at 3:15 a.m. The planet shines nicely at 0.05 magnitude, and has a white color, tinged ever so slightly with yellow.
One big help in finding Saturn this year: The planet is in the claw of Scorpius, the Scorpion.
Mercury rises in the eastnortheast just before dawn in the second half of June but the window of visibility is narrow; it comes up just after 4:30 a.m. and is lost in the breaking day at 5:15 a.m.
ALOHA, CRUX
Every year in the Hawai-ian islands, June is the last month to catch the Southern Cross in the evening sky. Hawaii the only state that has a good shot at seeing the entire Cross; it never rises above the horizon in most of the continental U.S.
Our Bishop Museum June 2015 star map, which shows the Southern Cross in the south-southwest, is good for 10 p.m. at the start of June, 9 p.m. in the middle, and 8 p.m. (first darkness) at the end of the month. If you go Cross-hunting in early June at, say, 8 p.m., the Cross will be due south at 8 p.m., when it first gets dark this time of year.
The Southern Cross’ official astronomical name is Crux (Latin for “cross”). In Hawaiian, it’s known as Hanaiakamalama (“cared for by the moon”).
The biggest help in Cross-finding are the two really bright stars low in the south, Alpha and Beta Centauri. Both of these stars are much brighter than any of the Cross’ stars. Alpha Centauri is in fact the thirdbrightest star in the sky; Beta Centauri, to its right, is also brilliant. These two stars pop right out, like two eyes looking down at you.
Once you have found Alpha and Beta Centauri, just go right about two times the distance between the pair of bright stars and you come to Gacrux, the top star in the Cross.
Gacrux also is the second-brightest star in the Cross and a good place to start with that constellation. Once you’ve found the top star, look down to pick out Acrux, which marks the bottom of the long part of the Cross.
Acrux is the only firstmagnitude star in the Cross and it needs to be, since it’s the one most often lost in the haze down near the horizon.
Once you’ve found the long part of the Cross, find the crossbar. The left side of the crossbar is marked by the second-magnitude star Becrux (also charmingly called "Mimosa"); it stand out well.
The real challenge is finding the star that marks the right side of the crossbar: That one, called Delta Crucis, is only third magnitude, and you’ll probably need to spend some time scanning that part of the sky to pick Delta Crucis out.
Once you find Delta Crucis, though, you know you’ve joined the club of people who see the Southern Cross and know they’re seeing it.
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