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Night Sky

Jupiter

June 2010 Night Sky

—Charlie Christmann

These side by side images of Jupiter taken by Australian astrophotographer Anthony Wesley show the SEB in August 2009, but not in May 2010. Individual images: Aug. 4, 2009 and May 8, 2010.

June is a great month to go outside and stargaze. Please, be courteous and turn off your outside lights to keep your night sky dark for everyone.

 Last month I wrote about the moons of Saturn. Well, I planned to write about the moons Neptune and Uranus, but I will interrupt that series for an interesting current development.

Striped Planet

Jupiter is a giant ball of gas and liquid with little, if any, solid surface. Instead, the planet’s surface is composed of dense red, brown, yellow, and white clouds. The clouds are arranged in light-colored areas called zones and darker regions called belts that circle the planet parallel to the equator. Jupiter’s atmosphere is composed of about 86 percent hydrogen, 14 percent helium, and tiny amounts of methane, ammonia, phosphine, water, acetylene, ethane, germanium, and carbon monoxide.

These chemicals formed colorful layers of clouds at different heights. The highest white clouds are made of crystals of frozen ammonia. Darker, lower clouds of other chemicals occur in the belts. At the lowest levels that can be seen, there are blue clouds. Yellow and brown stripes noticeably streak the white background along two bands in the northern and southern hemisphere. These are the equatorial belts. The Great Red Spot (GRS) floats along the lower edge of the southern equatorial belt. While there are other equatorial belts, they are more difficult to see without a powerful telescope.

Now, something wonderful is happening on Jupiter. “This is a big event,” says planetary scientist Glenn Orton of NASA’s Jet Propulsion Lab. It’s a development that is changing the appearance of the planet. The southern equatorial belt has all but disappeared.

 In any size telescope or even in large binoculars, Jupiter has always included two broad equatorial belts with the red spot embedded in the southern belt. Now, when the GRS comes into view, it’s floating almost entirely in a sea of white clouds. Looking at Jupiter today reveals only the northern equatorial belt.

Jupiter’s atmosphere is mysterious. No one knows why the Great Red Spot is red, or why it has raged the hundreds of years since Galileo first observed the planet. Nor is there a theory to explain why the twin equatorial belts are brown. And now, there seems to be only conjecture as to the disappearance of the southern belt.

But this isn’t the first time the southern belt has faded away. Most recently, it faded from 1973 to 1975, 1989 to 1990, and again in 1993 and 2007. In all but 2007, the belt faded completely to the average backyard telescope. Now in 2010, it has almost disappeared again. “Jupiter with only one belt is almost like seeing Saturn when its rings are edge-on and invisible for a time—it just doesn’t look right,” wrote Bob King of Duluth, Minnesota, in a May 10 entry of his blog, “Astro Bob.”

One hypothesis is that ammonia cirrus clouds have formed on top of the belt, hiding it from view. On Earth, the analogy would be the high altitude wispy cirrus clouds made of ice crystals. On Jupiter, the same sort of clouds can form, but the crystals are made of ammonia instead of water.

Another educated guess as to the reason is due to some sort of climate change happening with the giant planet. Last year, astronomers announced that Jupiter’s Great Red Spot appeared to be shrinking. In 2008, other red spot-like storms, but smaller than the great spot, showed changes as well, while activity in the southern equatorial belt also appeared to slow down. Jupiter will randomly grow a new storm or spot. Some of these even dramatically change color between white and red over time. No one knows how long the strip will be gone from Jupiter. But if you have a backyard telescope, keep watching. Perhaps you will be the first to see the southern equatorial belt return.

Jupiter shines in the eastern sky before dawn. Just look for the “morning star”—it’s really just Jupiter.

The Planets and the Moon

Mercury is in the eastern morning sky. Look around 5 a.m. for the elusive planet. Use binoculars 30 minutes before sunrise on the 11th. You can find Mercury seven degrees to the lower right of a waxing crescent Moon.

Venus is the evening star bright in the west northwest after sunset. It sets about 11 p.m. this month. Be impressed on the 14th by a Venus–two-day-old Moon conjunction. Venus will be just above the Moon, with Castor and Pollux to the right of Venus. That same evening, find a dramatic lineup stretching from the northwestern horizon toward the southwest; in order, you’ll see the Moon, Regulus, Mars, and Saturn.

Mars is higher up in the west than Venus after sunset. It sets about 1 a.m., early this month. On the 16th, the Moon closes in on Mars and Regulus for a conjunction.

Jupiter is the morning star. Find it shining brightly high in the east southeast before sunrise. On the 6th, look for Jupiter six degrees to the lower right of the Moon. On the morning of the 8th, about 90 minutes before sunrise, get out your binoculars and telescopes. Jupiter and blue-green Uranus will be separated by only 0.4 degrees.

Saturn is high in the southwest after sunset. On the 18th, you can find the Moon and Saturn together in the head of Virgo.

The Moon is new at 5:15 a.m. on the 12th and full at 5:30 a.m. on the 26th. On the 26th, get up early to see a partial lunar eclipse. The maximum will occur at 5:38 a.m., when 58 percent of the Moon will be in shadow.

You can celebrate the start of summer on the 21st. The Summer Solstice occurs at 5:48 a.m.

 

     

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