[Spitzer-news] Spitzer Telescope Sees Trail of Comet Crumbs

spitzer-news at lists.ipac.caltech.edu spitzer-news at lists.ipac.caltech.edu
Wed May 10 12:41:58 PDT 2006

In this issue:

1) Spitzer Telescope Sees Trail of Comet Crumbs 
2) Spitzer Spies the Remnants of a Shy Star
3) Spitzer Scientist To Give Prestigious Darwin Lecture
4) NASA's Spitzer Space Telescope a Cosmic Success!



NASA's Spitzer Space Telescope has snapped a picture of the bits and
pieces making up Comet 73P/Schwassman-Wachmann 3, which is continuing to
break apart on its periodic journey around the sun. The new infrared
view shows several chunks of the comet riding along its own dusty trail
of crumbs. 

"Spitzer has revealed a trail of meteor-sized debris filling the comet's
orbit," said Dr. William T. Reach of NASA's Spitzer Science Center at
the California Institute of Technology, Pasadena. Reach and his team
recently observed the comet using Spitzer. The picture can be viewed at

Comet 73P/Schwassman-Wachmann 3 consists of a collection of fragments
that file along like ducks in a row around the sun every 5.4 years. This
year, the bunch will pass by Earth beginning on May 12 before swinging
by the sun on June 6. The fragments won't get too close to Earth, about
7.3 million miles, or 30 times the distance between Earth and the moon,
but they should be visible through binoculars in the countryside night

The icy comet began falling apart in 1995 during one of its tropical
trips to the sun. Astronomers believe that its crusty outer layer
cracked due to the heat, allowing fresh ice to evaporate and split the
comet apart.  

During the past six weeks, amateur and professional astronomers have
been watching the comet fall apart before their telescopes' eyes.
Spitzer viewed the broken comet from its quiet perch up in space May 4
to May 6, covering a portion of the sky that allowed it to spot 45 of
the 58 known fragments. 

The observatory's infrared view also provides the first look at the
dusty trail left by the disintegrating comet after it splintered apart
in 1995. The trail is made up of comet dust, pebbles and rocks that
occasionally rain down on Earth in what is called the Tau Herculid
meteor shower. From May 19 to June 19, as Earth passes through the
outskirts of the trail, only a weak meteor shower is expected, with just
a few "shooting stars" visible in the night sky. A larger meteor shower
might occur in 2022 if Earth crosses near the comet's wake as predicted.

Spitzer's infrared eyes were able to see the dusty comet bits lining the
trail because the dust is warmed by sunlight and glows at infrared
wavelengths.  Most of the dust particles, specifically the
millimeter-sized nuggets, had never been seen before. Reach said that
these particles probably represent the natural deterioration of the
comet over the years, a process commonly observed in intact comets.

The comet dust also adds up to more evidence for the "icy dirtball"
theory of comets. In recent years, more and more astronomers are coming
to think of comets not as snowballs coated in dust, but as dirtballs
crusted with ice. 

"By measuring the brightness and extent of the debris trail, we are
trying to find out whether most of the comet's mass disintegrates into
vapors from evaporating ice, the house-sized chunks seen in images from
the Hubble Space Telescope, or the meteor-sized debris seen in the
Spitzer images," said Reach.

Reach and his team will continue to study the Spitzer data for clues to
how the comet broke up. Their infrared data will tell them the sizes of
the major fragments, which might indicate whether the comet did, as
believed, crack under the thermal stress.

Comet 73P/Schwassman-Wachmann 3 should be dimly visible through
binoculars on a clear night between the Cygnus and Pegasus
constellations from May 12 to May 28. For more information about viewing
the comet or the meteors, visit
http://science.nasa.gov/headlines/y2006/24mar_73p.htm .  None of the
comet's fragments pose a danger to Earth. For more information, see
http://www.nasa.gov/mission_pages/hubble/Comet_73P.html . 

Members of Reach's team include: Dr. Michael Kelley of the University of
Minnesota, Twin Cities; Dr. Carey M. Lisse of the Johns Hopkins
University's Applied Physics Laboratory, Laurel, Md.; Dr. Mark Sykes of
Planetary Science Institute, Tucson, Ariz.; and Dr. Masateru Ishiguro of
the Institute of Space and Astronautical Science, Japan.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer
Space Telescope mission for NASA's Science Mission Directorate,
Washington. Science operations are conducted at the Spitzer Science
Center at the California Institute of Technology. Spitzer's multi-band
imaging photometer, which made the observations, was built by Ball
Aerospace Corporation, Boulder, Colo.; the University of Arizona,
Tucson; and Boeing North American, Canoga Park, Calif. The instrument's
principal investigator is Dr. George Rieke of the University of Arizona.

For more information about NASA and agency programs on the Web, visit
http://www.nasa.gov/home/ . 




Big stars usually aren't shy about anything, not even death. At the end
of their lives, they throw explosive tantrums, called supernovae,
flinging abundant amounts of hot gas and radiation into space. Remnants
of this cosmic fury can last for several thousands of years and be
easily detected by most telescopes used by professional astronomers. 

But, not all stars like attention. Thirty light-years away in the
Cepheus constellation, astronomers think they've found a massive star
whose death barely made a "peep." Remnants of this shy star's supernova
would have gone completely unnoticed if the infrared eyes of NASA's
Spitzer Space Telescope hadn't accidentally stumbled upon it.

"This source is really trying to avoid detection," said Dr. Patrick
Morris of NASA's Herschel Science Center at the California Institute of
Technology in Pasadena, Calif. He is the lead author of a paper on the
discovery, which was published in the April 2006 Astrophysical Journal

So, what makes this lone star so unusual? Morris suspects that it sits
away from the mobs of stars that occupy the main disk of our Milky Way
galaxy. Our galaxy's disk is a crowded and dusty place, whereas the
regions above and below are comparatively dust free. It is this dust
that allows exploding stars to be readily detected. Expelled material
violently collides with surrounding dust, giving off bright light of
various wavelengths. The putative supernova remnant discovered by
Spitzer did not have enough dust around it to amplify its final death

In fact, when Morris and his team first found this object, the thought
that it could be a supernova remnant did not immediately cross their
minds. The object was completely invisible to previous all-sky surveys
taken by radio and X-ray telescopes. It did not even show up in
visible-light images. Team members thought that the object was most
likely a planetary nebula, or a star whose outer layers are gently
puffed off in its last stages of life. 

"There are various flavors of planetary nebulas; however, these objects
normally have a bright star in the middle, a lot of dust, and a big
range of chemistry. Our object shows none of this," said Morris.

For two years the team sifted through astronomical archives, literature,
and additional Spitzer data in hopes of determining what the source
could be. After months of comparing Spitzer's observations of the source
to many examples from other object classes, Morris' team carefully ruled
out the possibility that the source could be anything other than a
supernova remnant. 

The team was further inclined to believe this theory when they found
traces of oxygen in the region with Spitzer's infrared spectrograph.
Many known supernova remnants are surrounded by oxygen gas released from
the cores of their aging stars. 

Morris is currently planning to conduct deep radio observations of the
object to confirm that it is indeed a supernova remnant. If his
suspicions are correct, it will be the first supernova remnant ever to
be discovered solely by its infrared properties. At 25 times the mass of
our sun, the object will be among the three smallest and youngest
remnants in the Milky Way.




Dr. Michael Werner, project scientist of NASA's Spitzer Space Telescope,
has been selected to give the Royal Astronomical Society's distinguished
2006 George Darwin Lecture. Werner will be following in the footsteps of
the late Dr. Lyman Spitzer, the telescope's namesake, who was asked to
present the George Darwin Lecture in 1975. The lecture will be given at
4 p.m. local time Friday, May 12, at the Lecture Theatre of the
Geological Society of London.

Werner, who also serves as the chief scientist for astronomy and physics
at NASA's Jet Propulsion Laboratory, has worked on Spitzer since 1977.
The observatory, which launched in 2003, was originally conceived as a
Shuttle-attached payload and eventually grew into a self-sustaining
observatory, exploring hidden cosmic objects from dusty comets to
distant galaxies. 

Spitzer made a name for itself in March of 2005 when astronomers using
the telescope announced they had directly detected the light from
planets outside our solar system. Before that point, scientists were
unable to study extrasolar planets directly. Throughout Spitzer's
journey, various other discoveries have been made, such as alien
asteroid belts and the makings of miniature solar systems.

Werner's lecture, titled "The Spitzer Space Telescope: Probing the
Universe with Infrared Eyes," will cover scientific highlights from the
first 30 months of the mission. 

The George Darwin lecture is named after the esteemed astronomer who
studied tidal forces involving the sun, moon and Earth. George Darwin
was the son of Charles Darwin.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer
Space Telescope mission for the agency's Science Mission Directorate.
Science operations are conducted at the Spitzer Science Center at
Caltech. JPL is a division of Caltech.

For additional information about Spitzer on the Web, visit
http://www.spitzer.caltech.edu/spitzer .




Self-help books and grade school teachers have been promoting this tip
for decades: To keep success in sight, make a list of goals. 

Before launch, astronomers and engineers working on NASA's Spitzer Space
Telescope applied this tip to astronomy when they developed a list of
basic goals for the mission to accomplish. The list was referred to as
Level 1 Mission Requirements, and Spitzer's "mission success" was to be
measured on the telescope's ability to effectively accomplish every

On April 27, 2006, Spitzer officially satisfied the last open goal on
the Level 1 Mission Requirement list, which required the telescope to
obtain spectacular infrared images of the cosmos for at least two and a
half years. 

"The Spitzer Space Telescope continues to shine as a crowning jewel in
NASA's Great Observatory program. We now enjoy the satisfaction of
having successfully completed all of the Level 1 Requirements. Our focus
is lifted beyond the horizon in wonderment as to what additional new
science will be realized as we move beyond the requirement to the
completion of the mission," says Spitzer project manager, Robert Wilson. 

Later this month, on May 29, 2006, Spitzer will celebrate another
milestone, it's 1000th day in space. Thanks to an innovative group of
engineers and astronomers, expectations are high that the telescope will
continue to uniquely probe the infrared universe beyond its ultimate
pre-launch goal of five years. 



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