Idaho Skies

June 2008

Vol. 5 No. 6

Idaho Skies is a column for beginning amateur astronomers and those interested in astronomy. Suggestions about the column are gladly accepted by the columnist, at paul.verhage@boiseschools.org

This month look for the star Spica, the lucida of Virgo the Maiden. The easiest way to find Spica is to begin at Ursa Major (the Big Dipper) and follow the curve of the tail (handle) away from the body of the bear (or bowl). The first bright star you run into is pale orange Arcturus (you made an arc to Arcturus). Now continue traveling in a straight line to Spica (drive a spike to Spica). Spica is named (in Latin) after an ear of wheat. The Sun passes close to Spica in the autumn, when the grain is typically harvested.

Spica is 260 light years away. So the light you see tonight left in 1748, or 28 years before the signing of the Declaration of Independence. Spica is a blue hot star, 11 times more massive and almost 4 times hotter than our Sun. Its diameter is about 8 times larger than our Sun. In visible light, Spica is over 2,000 times brighter than the Sun. But if you include its ultraviolet radiation, Spica is over 13,000 times brighter than out Sun. So be sure to wear SPF 10,000,000 sunscreen when sun tanning (Spica tanning?) near this star.

A companion star orbits Spica. The two stars are large, but not twins of each other, and they are separated from each other by 1/8^th the distance between the Earth and the Sun. Their mutual gravity causes the stars to orbit each other in just 4 days and raises tides in each other. The tides give each star a slightly egg-shape.

Spica appears as the brightest star one third of the way above the south-southwest horizon early on June nights.

June 1 – 7

Five years ago on the 2^nd, the spacecraft, Mars Express left earth on a Russian rocket booster. Mars Express, Europe’s first interplanetary space mission was built around satellite components traditionally used on many earth orbiting spacecraft. The result is that Mars Express was a reliable, but cheap and quickly built spacecraft. Mars Express has been returning data since it entered Martian orbit on Christmas day, 2003. The spacecraft is currently returning high resolution images of the Martian terrain, maps of its mineralogical make-up, photographs of weather phenomenon, and radar scans of the planet’s subsurface.

One of the most interesting experiments is MARSIS, the radar subsurface scanner. MARSIS consists of two 44 foot long radio antennas protruding from the spacecraft. Its transmissions bounce radio signals off the Martian ionosphere and surface. Because the radio waves penetrate the ground, MARSIS is capable of detecting ice and meteor craters hidden beneath the Martian surface.

A spectrometer onboard Mars Express has discovered methane gas seeping out of the Martian surface. This source of methane could be active volcanism or buried microorganism. Either source would be a surprise as neither is expected to be occurring on Mars currently.

Mars Express carried a passenger to Mars, the Beagle 2 lander. Built with cost cutting in mind, the Beagle 2 entered the Martian atmosphere two days after its release from Mars Express but was never heard from again.

Launched 25 years ago on the 2^nd and 6^th, the Venera 15 and 16 were Soviet-built 5 ton spacecraft sent to Venus. It took 4 months for the pair of spacecraft to cross the gulf between Earth and Venus and both successfully entered into Venusian orbit in October 1983. Each 16 foot tall spacecraft carried a synthetic aperture radar (SAR) antenna 4.5 feet wide and 20 foot across. Radio pulses transmitted by the antenna penetrated the clouds of Venus and bounced off its surface. The reflected signals were received by the spacecraft, but only after each had traveled some distance. The physical displacement between transmission and reception enabled the spacecraft to produce higher resolution images of the surface than their antennas could do stationary. Due to the synthetically larger looking antenna, this technique of creating high resolutions images is called synthetic aperture radar. The SAR of Venera 15 and 16 produced terrain maps of the surface with a resolution between 0.6 to 1.2 miles from a 620 to 40,000 mile high orbit. Together they mapped 25% of the Venusian surface during their 8 month lifetime.

On the 3^rd, the moon is at perigee, or at its closest to earth this month. This month the moon is a measly 221,985 miles away. A 747 jumbo jet would only need two weeks to fly to the moon on the night of the 3^rd.

Also on the 3^rd, the moon is new. Tonight the coasts will experience larger than typical tides because the moon lines up with the sun (the definition of New Moon) and is at perigee (its closest to earth) on the same day.

Just as it gets dark on the 6^th, look low in the west for the thin crescent moon. Just 7 lunar diameters to its upper left is the Beehive star cluster. Both the moon and the cluster will fit neatly together within your binocular’s field of view.

On the 7^th, the moon passes within 5 lunar diameters of Mars. Mars appears as the orange colored star to the moon’s upper right. While the moon makes a great binocular object, Mars will just appear as a bright orange star near the moon.

June 8 – 14

Here’s a helping hand to locate Saturn. The ringed-world forms a small celestial triangle with Regulus and the moon on the 8^th. The grouping is small enough that all three will fit within your binoculars. Their orientation is illustrated in the diagram below.

The moon reaches the first quarter phase on the 10^th. Even in binoculars, the half moon provides great views of craters and mountains along its terminator, or boundary between day and night. Look in the lunar north for mountain ranges and in the lunar south for craters.

June 10^th is the 5^th anniversary of the launch of the Mars Exploration Rover-A (MER-A) more commonly known by the name Spirit. Since landing on Mars on January 4^th, 2004, Spirit has traveled over six miles as it has explored Bonneville Crater and the Columbia Hills. The specification for Spirit called for it to operate for a minimum of 90 days. So far, Spirit has functioned for over 1,400 days.

Its extended lifetime has given Spirit the chance to make discoveries impossible for a stationary lander. For example, some of the rocks around Spirit’s landing site show alteration by water. However, the water may have come from volcanic steam rather than flowing liquid water. Since Spirit has one bad wheel, it drives best when driving backwards and dragging its stuck wheel. One benefit of the bad wheel is that Spirit churns up a lot of Martian soil. This led to the discovery of a patch of Martian soil white with salt. That’s more evidence of water in the Martian past. The salt was most likely deposited in an ancient hot spring, the exact location where life is plentiful on Earth.

Another of Spirit’s discoveries is dust devils. Over time, dust settles on Spirit’s solar array. As more dust accumulates, it blocks more sunlight and reduces the ability of the array to produce power. Dust devils have winds strong enough to clear a lot of the dust off the array, raising their energy output. Like its twin, Spirit has also discovered a meteorite on the Martian surface.

Since the rover is closer to the Martian arctic than its twin rover Opportunity, Spirit spends each Martian winter parked with its array tipped towards the south and the low sun. Spirit is showing signs of aging, a bad wheel, a worn out rock grinder, and failed and failing spectrometers. However, JPL continues to nurse the rover to get the most science possible out of it.

June 15 – 21

The moon reaches the apogee of its orbit on the 16^th. Today the moon will be its greatest distance from earth at 252,418 miles away. That puts the moon 30,433 miles farther from the earth this week than two weeks ago when the moon was at perigee. That’s more than a 12% increase in the moon’s distance from two weeks ago.

The lucida of Scorpius the Scorpion, Antares, is 1 degree above the moon on the night of the 16^th. Look for the pair just after it gets dark. In your binoculars, Antares will have a pale orange color.

The moon is full on the 18^th. The full moon in June is often called the Rose Moon. Its bright white light will erase all the fainter star you normally see from the sky.

Got Jupiter? The king of the planets is only 5 degrees to the left of the moon on the 19^th. The pair will rise at 11 PM and by early morning, the position of Jupiter with respect to the moon will have rotated to above the moon. At a separation of five degrees, both are visible in your binoculars at the same time. And if you hold the binoculars steady, the largest satellites of Jupiter will be visible. How about that, our moon and Jupiter’s moons visible together in binoculars.

The sun reaches the solstice on the 20^th at 5 PM. That means summer begins for the northern hemisphere. Today the day is its longest and the night its shortest. Also at solstice, the sun reaches its greatest angle above the horizon.

June 22 – 30

The most distant planet in our solar system is Neptune and the moon will help you locate it on the morning of the 23^rd. This will be difficult to see, as Neptune will be a faint star close to the bright gibbous moon. At 3:00 AM on the 23^rd, put the moon in your binoculars or small telescope (set to low power). Now push the moon just outside the field of view and close to the moon’s right you’ll see a pair of faint stars and Neptune below (in a telescope the image will be upside down). Neptune will be slightly brighter than the star pair and you’ll need dark skies to see it.

The moon is at last quarter on the 26^th. This means you won’t be able to go moon watching until after midnight or early in the morning.

Earth received a wake up call 100 years ago on the 30^th. June 30, 1908 started out as just another day for the Tungus people in Siberia. At 7:14 AM, they saw the sky split in two as a great meteor, glowing brighter than the sun, fell from the sky. This meteor didn’t go out with the whimper like most meteors, the tremendous heat of its reentry vaporized the space rock and it exploded some 5 miles above the ground. The 50 foot diameter meteoroid or comet exploded with the force of a 10 to 15 megaton nuclear bomb. For the first time, humanity had witnessed an explosion as powerful as a hydrogen bomb. People over one hundred miles away where knocked off their feet and their windows shattered by the explosion. The explosion was felt like a magnitude 5 earthquake to people near the blast.

It wasn’t until 1927 that Russian Leonid Kulik lead an expedition to find the crater. However, Kulik didn’t discovered the expected crater. Instead, he found that 830 square miles of trees had been knocked over and set on fire. Pictures taken of the forest look eerily like Hiroshima did after the dropping of the first atomic bomb in 1945. Burned trees in the center of the destroyed forest stood upright and stripped of their bark. Trees away from the center were tipped over and pointing away from the epicenter of the explosion.

No crater or meteorite fragments are found at Tunguska. Instead, tiny melted glass spheres litter the soil, the left over from the explosion of an extraterrestrial visitor 100 years ago. Events like Tunguska occur naturally and programs like Space Watch scan the skies to make sure we’re never surprised again.

This Month’s Sources

The Royal Society of Canada, Observer’s Handbook 2008

Kaler, James, Stars: Spica, <www.astro.uiuc.edu/~kaler/sow/>

Night Sky Explorer (software)

Chronology of Space Exploration, http://www.solarviews.com/eng/craft1.htm

Wikipedia, Venera 16, 3 December 2007, 13 April 2008, <http://en.wikipedia.org/wiki/Venera_16>

Wikipedia, Venera 15, 20 January 2008, 13 April 2008, <http://en.wikipedia.org/wiki/Venera_15>

Wikipedia, Mars Express, 4 April 2008, 14 April 2008, <http://en.wikipedia.org/wiki/Mars_Express>

Wikipedia, Tunguska Event, 9 April 2008, 15 April 2008, <http://en.wikipedia.org/wiki/Tunguska_event>

ESA, Mars Express, 11 October 2005, 16 April 2008, <http://www.esa.int/esaMI/Mars_Express/SEMNS75V9ED_0.html>

Wikipedia, MER-A, 13 April 2008, 14 April 2008, <http://en.wikipedia.org/wiki/MER-A>

Dark Skies and Bright Stars,

Your Interstellar Guide