Skywatch June 2017

Skywatch June 2017

This June provides a great chance to see the solar system’s biggest planets, Jupiter and Saturn, throughout most of the evening. June is also the final time each month to catch the Southern Cross.

June Star Map and its wonders

Since many of the great sights of our June sky are seen clearly on our June 2017 sky map, I’ll use that map as our point of reference was we discuss how to find Jupiter, Saturn, the Southern Cross, and Scorpius (Maui’s Fishhook).

As with all of our monthly star maps, the June map is good for 10 p.m. early in the month, 9 p.m. in the middle of the month, and 8 p.m. at the end of the month.

As our June 2017 star map shows, Jupiter and Saturn are well-placed for viewing in the mid-evening sky.

Jupiter

At map-time, look for the bright white dot of Jupiter about halfway up in the southwestern sky. Jupiter is the brightest dot in the June 2017 evening sky. Jupiter shines at minus 2.25 magnitude, much brighter than any star, so it will pop out easily. Blueish-white star Spica, about ten degrees (the width of your palm at arm’s length) to the left of Jupiter, shines respectably at 0.96 magnitude, but Jupiter outshines it by 20 times.

In even a small telescope, Jupiter appears as a disc with four bright dots. These dots are the ‘Galilean moons’ that Galileo discovered with his new-fangled telescope in January 1610. If you come to our ‘Stars and Guitars’ program in the planetarium on Saturday, June 3 (8 p.m.), we do open the observatory after the planetarium show, and we should get a good view of Jupiter and its four bright moons if the skies are clear. Reservations: https://www.bishopmuseum.org/stars-guitars/

In early June, Jupiter will set in the west at 2:30 a.m.; by the end of the month, it sets by 1 a.m.

Saturn

If you return to our star map, Saturn is rising in the southeast at map time (which again is 10 p.m. in early June, 8 p.m. in late June). The planet is about 20 degrees above the southeast horizon, which is about the width of two palms held at arm’s length. Saturn has a distinctive yellow-white color. While it’s nowhere near as bright as Jupiter, Saturn does shine nicely at 0 magnitude. This makes Saturn about 2.5 times brighter than the star Antares in the Scorpion, the first-magnitude star to the right of Saturn. That said, the somewhat-dimmer Antares can be your guide to find Saturn, because Antares is at the heart of the constellation of Scorpius. Scorpius (Maui’s fishhook) pops out easily in the sky. Antares is the only first-magnitude star in the Scorpion, and has a distinctive orange hue. Once you’ve found Antares, look left about the width of two of your palms, and the bright whitish-yellow light that is somewhat brighter than Antares is Saturn.

Saturn is in opposition on June 15. When a planet is in opposition, there is a straight line between the sun, the earth in the middle, and the planet. During opposition, a planet rises at sunset, is high at midnight and sets at dawn. This is also the time when the planet is nearest to earth (though in Saturn’s case it’s still almost a billion miles away), and shines most brightly.

In early June, Saturn will be due south by 1:30 a.m. and will work its way down the western sky in the wee small hours of the morning; by daybreak, Saturn will be low in the west. By the end of the month, look for Saturn due south at 11:30 p.m.; it will set in the west at 4:45 a.m., just as the first light of dawn starts to break. In  these early hours of the morning you can still use the Scorpion and Antares to find Saturn; but if you go looking for the them after midnight, please note that Saturn will be above Antares, rather than to the left of Antares, as is the case earlier in the evening.

Saturn’s rings are perhaps the most beautiful telescope sight of all. Centuries after they were first spotted in a telescope, the most common comment from first-time Saturn viewers that the “rings don’t look real.” The rings should be more striking than usual this season. The rings are tilted 27 degrees to our line of sight this summer, the best ‘tilt’ since 2003; this means that the rings are exceptionally well-angled for good telescope viewing.

We might be able to catch Saturn in our observatory telescope after the ‘Stars and Guitars’ program on Saturday June 3, though that we’ll be lucky if we do, since the ringed planet will just be clearing the hills of Kalihi at 9 p.m. in early June. We do expect great telescope views of Saturn after the next ‘Stars and Guitars’ show on Saturday July 1, as long as the weather cooperates. Our ‘Stars and Guitars’ planetarium program happens rain or (moon) shine, but our telescope is weather-dependent! Reservations: https://www.bishopmuseum.org/stars-guitars/

Star map constellations

 

In addition to featuring good views of Jupiter Saturn, the June star map shows you how to find many well-known constellations, including the Southern Cross.

The Southern Cross

On the June map (good for 10 p.m. in early June, 8 p.m. at the end), the Southern Cross, or ‘Crux,’ is low in the south, and indeed is just about to set. To locate Crux, make sure you have a flat horizon, such as the sea, to view it. The bright stars Alpha and Beta Centauri, to the left of the cross, are just rising at map-time and can be an invaluable guide. These two brilliant stars are called ‘The Southern Pointers.” Find them, look right, and they’ll point you to the top star in the Cross, Gacrux.

This map gives you a good idea of what the Cross looks like, and where to find the southern pointer stars of Alpha and Beta Centauri. That said, if you want the best shot at seeing the Southern Cross in June, I’d suggest going out about 8:15 p.m. early in the month, as darkness is just setting in. At about 8:15 p.m. in early June Crux will be due south, and will be at its highest point in the sky.  This is still not very high – a mere six degrees from the bottom star to the horizon – but your odds of catching it are best when the cross is due south. Even by 8:15 p.m. in early June the Southern Pointers will have risen, so they can serve as a handy guide to finding the Southern Cross itself.

By June 15, the Cross will no longer be exactly south at 8:15 p.m., but rather a little to the right of due south; but the odds of seeing it will still be better than when the Cross is about to set, as depicted on our June map.

I have seen the Cross as late in the year as July 4, under ideal weather conditions; but for all intents and purposes we lose Crux by the end of June every year in the Islands. From the start of July to the end of November we can’t see it at all; the Southern Cross returns to the morning sky around December 1.

Other constellations on the map

As discussed above, the constellation of the Scorpion, or Maui’s Fishhook, is rising in the southeast on our map, and will be our constant companion all summer.

Our map shows the star Arcturus in the exact top of the sky, or the zenith.  The star is known as Hokule‘a in Hawaiian, ‘the star of gladness’; one reason for its significance in the island is that Hokule‘a passes almost exactly overhead as viewed from the latitude of Hawai‘i. You can also see the Big Dipper in the north, its cup pointing to the North Star and its handle pointing to Arcturus.

The summer triangle is just rising in the northeast by map time; the stars Vega, Altair and Deneb, pulled from three separate constellations to make a big triangle in the sky.

Other sky events in June:

Venus lights up the hours before dawn

Throughout June, Venus rises in the east just after 3 a.m. as is about 1/3 of the way up in the east at daybreak. Venus shines at minus 4.3 magnitude, many times brighter than even Jupiter.

Mars and Mercury: for all intents and purposes, neither is really visible in the June sky.

June 20

Summer begins on June 20 at 12:35 a.m. Hawai‘i Standard Time (22:35 on June 20 Universal Time).  This is the longest day for the northern hemisphere and the shortest for the southern hemisphere.

Moon phases (Hawaiian Time zone):

First Quarter: June 1
Full: June 9
Third Quarter: June 17
New: June 24
First Quarter: July 1

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