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The Honolulu Advertiser
Posted on: Sunday, May 27, 2007

Autumn symbol Virgo is high in spring's sky

By Carolyn Kaichi
Bishop Museum

Use this map by holding it over your head so that its northern horizon points toward the northern horizon on the Earth. This illustration represents the sky at about 10 p.m. in early June, 9 p.m. in mid-June and 8 p.m. in late June.

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Perched high in the springtime sky after dark is the large, sprawling constellation of Virgo. Only one brilliant star stands out in this second-largest constellation, making it somewhat difficult to imagine the maiden in this group of stars. One way to find Virgo is the "starline" method of starting with the curvature of the Big Dipper's handle.

Start with the famous mnemonic: follow the Dipper handle's "arc to Arcturus," the distinctly orange star in the path as you continue the curve through the sky. Generally referred to as the fourth-brightest star in the sky, Arcturus is also known as Hokule'a here in Hawai'i.

From Arcturus, "speed on to Spica," the brightest star in Virgo, symbolizing the stalks of wheat Virgo carries in her arms during the autumn harvest.

But why is a constellation associated with harvest time prominent in the night sky right now? Remember that the sun slowly progresses through the constellations of the zodiac throughout the year, and the autumn equinox, the point where the sun passes from the northern sky to the southern sky, happens around Sept. 22. At that time, the sun is traveling through Virgo, although you can never really see the constellation then because it's daytime.

Virgo also symbolizes fertility, and it is in this region of space that you can see part of the great family of galaxies that includes the Milky Way. Almost all the pinpoints of light you can see with your eyes are individual stars (or the five visible planets) that reside in our little corner of our galaxy called the Milky Way.

The farthest object you can see with the naked eye (depending on the darkness of your sky) is the Andromeda galaxy, a little over 2 million light years away. Andromeda is the closest large galaxy to us. But Andromeda and the Milky Way are only part of a group of around 2,000 gravitationally-connected galaxies known as the Virgo Cluster, stretching more than 50 million light years away. Binoculars can resolve some of the fuzzy spots of the larger and closer galaxies, each with billions of stars like our own. The Virgo Cluster is only part of another larger supercluster of stars, one of many superclusters that make up the known universe.

That's a lot to wrap your mind around. To try to get a sense of this magnitude, imagine our entire solar system (our sun plus the planets) shrunk down to the size of a quarter. The sun would be microscopic and the planets even smaller. At this scale, our quarter-sized solar system is lost in a Milky Way galaxy the size of the Mainland, with the next microscopic "star" two soccer fields away.

Now take the whole "Milky Way-Mainland U.S.A." and shrink that down to the size of a compact disc. At this scale the Andromeda galaxy would be another CD eight feet away. Scatter billions of those CDs around a 10-mile radius and you've got everything we can see in the entire universe. Just in case you're wondering, I don't make this stuff up — this information comes courtesy of our friends at NASA via the Harvard-Smithsonian Center for Astrophysics.

SPACE TRAFFIC

June is expected to see some interesting arrivals and departures to and from our planet. The space shuttle Atlantis is scheduled to launch on June 8 now that repairs have been completed following damage from a hailstorm. In addition to delivering parts and continuing the construction of the international space station Alpha, the mission includes a crewmember swap of two American astronauts. Sunita Williams has been on board the station since December 2006 and will be replaced by Clayton Anderson, who is scheduled to remain until October.

Another fascinating mission to watch is called Dawn, which is to launch on the last day of June. This spacecraft will make an eight-year, 3.2-billion-mile journey to the asteroid belt — the region of space between Mars and Jupiter. During its mission, scientists will study both the brightest asteroid, Vesta, and the largest asteroid, the "dwarf planet" Ceres, to understand the origins of our solar system and the processes of planet formation.

The asteroid belt consists of at least 90,000 cataloged asteroids, ranging from small rocks to Ceres, one-quarter the diameter of our moon. Scientists believe the asteroids would have accumulated into another planet if Jupiter's mass had not interfered with that process billions of years ago when the planets were forming.

Vesta, the brightest asteroid, is just bright enough to be seen with the unaided eye under good viewing conditions.

It also happens to be in the evening sky this month, about eight degrees (approximately the span of four fingers held up at arm's length) slightly north and to the west of Jupiter.

THE PLANETS

Mercury: Mercury appears low and relatively bright in the western sky after sunset for the first half of June. By the third week, the little planet starts to sink lower in the west as it heads back toward the morning sky; by June 20 it will be challenging to see it at all.

Venus: Venus stays up late all month, setting after 10 p.m. in early June, and about 20 minutes earlier at the end of the month. It starts off in Gemini and slowly moves through Cancer toward Leo during the month. Watch Venus and Saturn move closer together throughout June, to their closest point on June 30. On June 17, a thin crescent moon will be close to the right of Venus.

Mars: Mars is now starting to rise in the early morning hours around 2:30 a.m. and by the end of the month around 45 minutes earlier. As the Earth starts to catch up with the outer planet, it continues to get brighter and easier to find. Mars is in a fairly dark area of the sky in the constellation Pisces, with no bright stars around it to compete with its reddish glow.

Jupiter: This is Jupiter's month for opposition — it rises opposite the sunset on June 5. Jupiter is easy to see even nested next to the large, bright constellations of the season like Scorpius. It remains in the sky until dawn for most of the month.

Saturn: Saturn has a close encounter with both the moon and Venus this month. The crescent moon closes in on the ringed planet on June 18, a day after meeting up with Venus. On June 30 and into the first day of July, Saturn and Venus appear as a planetary couple, then Saturn quickly descends into the west in the following days.

Questions? Contact Carolyn Kaichi at 847-8203 or hokupaa@bishopmuseum.org.