[astronomyed] December (January) "Planetary Wonderings" Focus: WISE

  • From: Mary-Frances Bartels <ki0dz@xxxxxxxx>
  • To: astronomyed@xxxxxxxxxxxxx
  • Date: Tue, 05 Jan 2010 20:32:52 -0500

Planetary Wonderings
Focus:  Wide-field Infrared Survey Explorer
By Mary-Frances R. Bartels, NASA Solar System Ambassador

Launched December 14, WISE is NASA’s latest mission to study the universe in the infrared portion of the electromagnetic spectrum.  Infrared has been discussed previously in this column (most notably Nov. ’06 and Jun. ‘09), particularly as it pertains to the Spitzer Space Telescope mission.  Questions that might come to mind is --- why launch yet another infrared mission?  What is the difference between the WISE and Spitzer missions?

While Spitzer is indeed an infrared telescope, it is not a mapping mission like WISE.  Whereas Spitzer is examining small portions of the sky in great detail, WISE will scan the entire sky in less detail (lower resolution and sensitivity).  To accomplish its mission Spitzer is in a heliocentric orbit behind Earth, so thermal radiation from our planet will not interfere with its observations.  On the other hand, WISE is in a polar orbit around Earth that allows it to see the entire sky in just six months.  As one can see, Spitzer is not really a predecessor to WISE, but rather more of an adjunct to it.  More accurately, WISE’s true predecessors are the Infrared Astronomical Satellite (IRAS) launched in 1983 and COBE/DIRBE launched in 1989.  WISE should improve on those surveys by a factor of 500 for IRAS and 500,000 for COBE/DIRBE.

The WISE mission will operate for seven to 10 months at which time its coolant will be exhausted.  The nature of observing infrared light demands that the telescope be cooler than the objects it is viewing.  So, it is cooled by solid hydrogen in a “thermos” called a cryostat to temperatures between 7 K (-447 °F/-266 °C) and 32 K (-402 °F/-241 °C) depending on the instrument; contrast this to the liquid helium that was used to cool Spitzer to 5.5 K.  For reference, the temperature of the universe (cosmic microwave background radiation) is about 2.7 K.

The mission will catalog hundreds of millions of previously unknown objects from the universe’s most luminous galaxies to its coolest stars, those too cool or dusty to be seen in visible light.  WISE is also expected to discover hundreds of thousands of asteroids, hundreds of which pass close to Earth’s path.  Objects discovered by WISE can be further explored by future missions.

Resource of the Month:  Do you use social media?  If so, you may follow the latest in NASA’s solar system exploration on Facebook, Twitter, YouTube, and more.  For more information visit http://www.jpl.nasa.gov/social/ .  Those curious about NASA’s overall presence on social media are invited to see http://www.nasa.gov/collaborate/index.html .

Activity of the Month:  Learn about and observe Messier objects with binoculars.   Checking out M-objects is an activity easily done by beginning and advanced astronomers alike.  One does not need a telescope to see Messier objects; indeed some are even visible with the naked eye.  Because of their positions in the sky, a common time of the year to try to see most of these clusters, galaxies, and nebulae at one time is around the vernal equinox.  The Astronomical League offers a certificate and pin for those that successfully observe at least 50 of the 110 M-objects.  Information may be found at http://astroleague.org/al/obsclubs/binomess/binomess.html .  Participation requires membership in an astronomy club that is part of the League.  The website has a search box where one may enter a zip code and get a list of nearby clubs.  A search for central Ohio revealed three clubs: the Mid-Ohio Observers Group in Reynoldsburg, the Richland Astronomical Society in Caledonia, and Astronomy for Youth in Mansfield. 

Suggestions, questions, corrections, and comments about “Planetary Wonderings” are welcomed and may be directed to stargazer @ keeplookingup.net (remove spaces).  Past columns may be found at www.KeepLookingUp.net (click on “Planetary Wonderings” on the right side of opening screen) and at //www.freelists.org/archives/astronomyed/ (columns from Jan. 2007 to the present).

Remember to keep looking up!

Sources (not already mentioned):

JPL WISE emails dated June 10, November 17, December 9, and December 14

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