Astronomy News for the Month of September 2007


  This news letter is provided as a service by
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 Excerpts from JPL mission updates are provided as a public service as part
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In this Newsletter...

Background screen credits:NGC5775 -Imaged March 21/22, 2001 using the 16" Kitt Peak Visitors Center telescope as part of the Advanced Observing Program.


01

The Moon

Phases

Apogee/Perigee

Moon/Planet Pairs

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The Planets & Dwarf Planets

Planetary Reports generated by "TheSky" software. These reports provide predicted data for the planets for the first of each month for the current year. The rise and set times for the Sun and the Moon for each day of the month are also included in the reports.

(All times are local unless other wise noted.)
Planetary Highlights for September - Jupiter dominates the evening skies this month followed shortly by two other gas giants, Neptune and Uranus. Mars dominates the early morning hours and Venus returns to the morning sky. A partial solar eclipse will be visible for observers south of the border, specifically, South America and Antarctica.
Mercury - Has returned to the evening sky this month, though it will still be buried in the evening twilight glow. Mercury will be at greatest eastern elongation (26° above the western horizon) on the 29th. Mercury sets about 8:09 pm on the 1st and about 7:30 pm by month's end. Mercury shines at magnitude -0.1 on the 15th and dims slightly to magnitude 0.0 on the 30th.
Venus - Has returned to the morning sky this month. Venus reaches greatest brilliance (magnitude -4.8) on the 23rd. Venus rises about 4:59 am on the 1st and about 3:28 am month's end shining at magnitude -4.8. Venus is in the constellation of Leo.
Earth - The Autumnal equinox occurs at 5:51 am EDT on the 23rd.
Mars - Rises at 11:53 pm on the 1st and about 10:56 pm by month's end. Mars is in the constellation of Taurus and shines at magnitude 0.1.
Jupiter - Dominates the evening sky this month. Jupiter sets at 11:39 pm on the 1st and about 9:54 pm by month's end. Jupiter can be found low in the southern sky in the constellation of Scorpius and shines at magnitude -2.1.
Saturn - Has returned to the morning sky this month though remains low on the eastern horizon and may be difficult to spot until later in the month. Saturn rises around 5:42 am on the 1st and about 4:02 am by month's end. Saturn shines at magnitude 0.7. Saturn is in the constellation of Leo.
Uranus - Is at opposition on the 8th, rising about the same time the Sun sets. Uranus is at its best for the year. Uranus rises about 7:46 pm on the 1st and about 5:45 pm by month's end. Uranus is in the constellation of Aquarius and shines at a magnitude of 5.7.
Neptune - Still precedes Uranus by about an hour and is visible in the evening sky. Neptune rises at 6:35 pm on the 1st and about 4:46 pm by month's end. Neptune is in the constellation of Capricornus and shines at magnitude 7.8.

Dwarf Planets

Ceres - Rises about 10:18 pm on the 1st and about 8:24 pm by month's end. Ceres is in the constellation of Taurus. Ceres shines at magnitude 9.0.
Pluto - Sets about 1:09 am on the 1st and about 11:07 pm by month's end. Pluto is in the constellation of Sagittarius. Pluto shines at magnitude 14.0. As always, good luck at spotting this one.

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Astronomical Events

Meteor Showers

  • Aurigid Outburst may occur on the morning of the 1st. "This month's minor Alpha Aurigid meteor shower may give some observers a brief blast of activity. According to SETI Institute meteor expert Peter Jenniskens, Earth will run into the dust trail from C/1911 N1 (Kiess), a long-period comet. The encounter will create a 2-hour meteor outburst peaking at 4:36 A.M. PDT September 1.

    The timing favors western North America and Hawaii. A waning gibbous Moon (76-percent lit) will wash out all but the brightest meteors.

    Comet Kiess released the dust trail when it last rounded the Sun in 83 B.C. Jenniskens predicts as many as 3 Aurigid meteors a minute during the outburst.

    The meteors appear to radiate from a point near the bright star Alpha Aurigae (better known as Capella), hence the shower's name." (Astronomy Magazine, September 2007, p. 65)

    For more information about Comets and Meteor Showers, visit Gary Kronk's Comets & Meteor Showers webpage.

  • Comets

  • For information, orbital elements and ephemerides on observable comets, visit the Observable Comets page from the Harvard-Smithsonian Center for Astrophysics.

    For more information about Comets and Meteor Showers, visit Gary Kronk's Comets & Meteor Showers webpage.


  • Eclipses

  • A partial solar eclipse occurs on the 11th. The Moon's shadow will fall over Antarctica and South America.
  • Ocultations

    IOTA Logo

  • More information on occultations can be found by clicking the IOTA logo.
  • Asteroids

    (From west to east)
    • Vesta is in the constellation of Scorpius.
    • Pallas is at opposition on the 2nd in the constellation of Aquarius.
    • Urania is at opposition on the 3rd in the constellation of Aquarius.
    • Thyra is at opposition on the 5th in the constellation of Pegasus.
    • Flora is in the constellation of Taurus.
    • Eunomia is in the constellation of Gemini.
    • Information about the Minor Planets can be found at the Minor Planet Observer website.

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    Planetary/Lunar Exploration Missions

    (Excerpts from recent JPL mission updates)
    Cassini - August 2, 2007 - Cassini Finds Possible Origin of One of Saturn's Rings

    "PASADENA, Calif. -- Cassini scientists may have identified the source of one of Saturn's more mysterious rings. Saturn's G ring likely is produced by relatively large, icy particles that reside within a bright arc on the ring's inner edge.

    The particles are confined within the arc by gravitational effects from Saturn's moon Mimas. Micrometeoroids collide with the particles, releasing smaller, dust-sized particles that brighten the arc. The plasma in the giant planet's magnetic field sweeps through this arc continually, dragging out the fine particles, which create the G ring."

    Cassini Imaging Team

    For the latest mission status reports, visit Cassini Mission Status webpage. The speed and location of the spacecraft along its flight path can be viewed on the "Where is Cassini Now?" webpage.

    New Horizons - August 13, 2007 - Meet the New Horizons Pluto Pals!

    "New Horizons wasnÕt the only voyage launched on January 19, 2006 - this week we welcome the "Pluto Pals" to the New Horizons team, five kids who were born on the same day our spacecraft embarked on its historic journey the outer solar system. The idea for the club came to New Horizons Principal Investigator Alan Stern last year as he scanned news coverage of the spacecraftÕs launch. "I saw a fantastic Florida Today image of two boys watching the launch," he said. "It made me think it would be fun to follow some children who would grow up during our 9 1/2-year trip to Pluto." This past January - just as the spacecraft was about to take its own cautious first steps through the Jupiter system - Stern and the New Horizons Education and Public Outreach team put out a call for those who were born or turned 10 on launch day. Five toddlers were selected and you can see their "photo albums " on the New Horizons Web site at http://pluto.jhuapl.edu/education/plutoPals/."

    For more information on the New Horizons mission - the first mission to the ninth planet - visit the New Horizons homepage: http://pluto.jhuapl.edu/ for more information about the mission.

    Pack Your Backpack

    Calling all explorers! Tour JPL with our new Virtual Field Trip site. Stops include Mission Control and the Rover Lab. Your guided tour starts when you select a ÓfaceÓ that will be yours throughout the visit. Cool space images and souvenirs are all included in your visit.

    Past, Present, Future and Proposed JPL Missions - http://www.jpl.nasa.gov/missions

    Visit JPL's mission pages for current status.

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       Mars Missions

    Mars Global Surveyor

    Every six months, a new suite of MGS MOC data are archived with the NASA Planetary Data System (PDS).

    Information about how to submit requests is online at the new Mars Orbiter Camera Target Request Site, at http://www.msss.com/plan/intro"

    Newly-released MOC images can be seen in the MOC Gallery, a website maintained by Malin Space Science Systems, the company that built and operates MOC for the Jet Propulsion Laboratory and NASA.

    Visit the MGS pages at http://mars.jpl.nasa.gov/mgs/index.html. There are over 200,000 images of Mars from the MGS, check out the newest MGS images of the surface of Mars.

    Mars Odyssey Orbiter - No new news since May 02, 2007 - Sharp Views Show Ground Ice On Mars Is Patchy And Variable

    "Using observations by NASA's Mars Odyssey orbiter, scientists have discovered that water ice lies at variable depths over small-scale patches on Mars.

    The findings draw a much more detailed picture of underground ice on Mars than was previously available. They suggest that when NASA's next Mars mission, the Phoenix Mars Lander, starts digging to icy soil on an arctic plain in 2008, it might find the depth to the ice differs in trenches just a few feet apart. The new results appear in the May 3, 2007, issue of the journal Nature."

    "A simulated fly-through using the newly assembled imagery is available online.

    The fly-through plus tools for wandering across and zooming into the large image are at http://themis.asu.edu."

    Mars Odyssey THEMIS Images
    Thermal Emission Imaging System (THEMIS) website: http://themis.asu.edu/

    August 20-24, 2007

    The following new images from the Mars Odyssey spacecraft are now available:

    The Odyssey data are available through a new online access system established by the Planetary Data System at: http://starbrite.jpl.nasa.gov/pds/"

    Visit the Mars Odyssey Mission page.

    Mars Exploration Rover Mission (Spirit and Opportunity) - August 30, 2007

    Spirit Status: Spirit Slowly Emerges from Blanket of Dust - sol 1295-1302, August 30, 2007

    "Spirit remains healthy as the rover slowly picks up more solar energy. The dust storms appear to be over, at least for now, and the skies are slowly clearing. Unfortunately, what energy Spirit has gained from cleaner skies has been offset by losses to dustier solar arrays. Still, Spirit has the energy, about 325 watt-hours, to finally be roving again.

    Tau, a measure of atmospheric dustiness, declined slightly. As of Sol 1299 (Aug. 29, 2007), the Sun was at about 8 percent of its full brightness, an increase of a little more than 2 percent compared with five sols earlier. Dust on the rover's solar arrays increased by about 3 percent and only about 59 percent of the sunlight hitting the arrays gets through to make electricity.

    But rather than getting a 1-percent boost in solar power, the rover has been just about breaking even. The reason is that Tau measures direct sunlight but there's also scattered sunlight and it, too, increased by about 1 percent.

    Much of the dust previously seen on the turret has blown or fallen off. Dust contamination remains a concern, particularly for the microscopic imager, where some of the dust clumps visible in earlier images have fallen out or moved out of the line of sight.

    On Sol 1296 (Aug. 25, 2007), Spirit resumed driving to "Home Plate" and more specifically, to a location with gentle slopes and few rocks known as "the on-ramp." This drive was a turn-in-place, given Spirit's frozen right front wheel, to get the rover pointed in the right direction.

    After two sols of remote sensing with emphasis on characterizing whatever dust had accumulated on the panoramic camera, Spirit's handlers decided to have the rover retrace its tracks to assess what dust contamination might be present on the miniature thermal emission spectrometer. To do this, they needed to measure a known target.

    With a blanket of dust everywhere, scientists needed a way to distinguish dust on targets of scientific interest from dust on the optics. The best target for that was "Gertrude Weise," a patch of nearly pure-silica soil uncovered by Spirit's wheels. Rover planners decided to have the rover drag its wheels through it again to scrape off newly acquired dust and expose the same pure silica as before. Differences between old and new measurements would be due to dust on the instrument itself; once that signature was known, it could be subtracted from future measurements.

    The first drive to Gertrude Weise was a little short and didn't uncover the silica as hoped. Spirit's handlers planned a second drive on Sol 1300 (Aug. 30, 2007), during which the rover was to scuff the soil with a half-turn of the left front wheel, then scuff it more by locking both left and right front wheels and driving them backward across Gertrude Weise. They then planned to have the rover back up some more to take images and move toward the Home Plate on-ramp.

    Spirit was expected to resume the long-awaited trek to Home Plate on sol 1303 (Sept. 2, 2007)."

    Opportunity Status: Brightening Skies Bolster Opportunity - sol 1256-1265, Aug 23, 2007

    "Opportunity is healthy and remains perched near the rim of "Victoria Crater." The rover was on a low-power schedule that alternated between a 3-sol plan and a 4-sol plan.

    Tau (atmospheric opacity) has begun to stabilize this week at around 3.7, resulting in solar array energy between 230-240 watt hours. Therefore in the upcoming week, the team will return to nominal planning.

    The rover conducted a lot of what engineers call "runout science." This includes: panoramic camera wide-range tau measurements, navigation camera tau measurements, navigation camera cloud measurements, panoramic camera soria (imaging a rough, rocky area near the rover), front hazard avoidance camera images, rear hazard avoidance camera images, navigation camera images, panoramic camera sky spot, panoramic camera dust monitoring on the mast, miniature thermal emission spectrometer target calibration and panoramic camera high-sun surveys."

    Landing sites

    Visit the Mars Exploration Rover page.

    Mars Reconnaissance Orbiter - August 29, 2007 -
    HiRISE Camera Returns New View of Dark Pit on Mars
    And Adds 930 More Images to NASA Space Mission Archive

    By Lori Stiles, University Communications

    "The High Resolution Imaging Experiment (HiRISE) has confirmed that a dark pit seen on Mars in an earlier HiRISE image really is a vertical shaft that cuts through lava flow on the flank of the Arsia Mons volcano. Such pits form on similar volcanoes in Hawaii and are called "pit craters."

    The HiRISE camera, orbiting the red planet on NASA's Mars Reconnaissance Orbiter, is the most powerful camera ever to orbit another planet. It is operated at The University of Arizona in Tucson. HiRISE Principal Investigator Alfred McEwen of the UA's Lunar and Planetary Laboratory and his team released the new image of the dark pit on Arsia Mons and several other stunning images today on the HiRISE Web site, http://hirise.lpl.arizona.edu. New HiRISE images are released on the site every Wednesday."

    More information about the mission is available online at http://www.nasa.gov/mro.

    Mars Missions Status

    New Mars missions are being planned to include several new rover and sample collection missions. Check out the Mars Missions web page and the Mars Exploration page.

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    Links and Other Space News

    (If you have a link you would like to recommend to our readers, please feel free to submit it.)

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    Astronomical Lexicon

    Definitions of astronomical terms. Many of the astronomical terms used in this newsletter are defined here.

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    UT Logo

    Read the Universe Today Newsletter by clicking on the logo.

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    Acknowledgments and References

    Much of the information in this newsletter is from Astronomy® Magazine (Kalmbach Publishing), JPL mission status reports, the Internet, "Meteor Showers - A descriptive Catalog" by Gary W. Kronk, Sky & Telescope web pages, and other astronomical sources that I have stashed on my bookshelves.

    The author will accept any suggestions, constructive criticisms, and corrections. Please feel free to send me any new links or articles to share as well. I will try to accommodate any reasonable requests. Please feel free to send questions, comments, criticisms, or donations to the email address listed below. Enjoy!

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