Topic Name: Chance encounter with comet nets surprising results
Category: Solar cells
Research persons: Professor Thomas Zurbuchen, Professor George Gloeckler, Michael. R. Combi
Location: Department of Aerospace Engineering, 2429A Space Research Building 2143, United States
Comets are made of the most primitive stuff in the solar system.
As hunks of rock and ice that never coalesced into more planets, they give
researchers clues to the evolution of solar systems.
So a chance encounter between
spacecraft Ulysses and Comet McNaught's ion tail has scientists in the University of Michigan's College of
Engineering marveling at a stroke of luck and some surprising data.
The NASA/European Space Agency spacecraft is on a mission to
study the sun's polar regions, and it carries an instrument run by U-M
professors. In February, it flew through McNaught's ion tail 160 million miles
from the comet's core.
Instrument readings showed there was "complex chemistry" at
play, said U-M space science professor George Gloeckler, second author of a
paper on the findings published Oct. 1 in Astrophysical Journal.
Gloeckler is the principal investigator on the Solar Wind Ion
Composition Spectrometer (SWICS) aboard Ulysses, which measured the composition
and speed of the comet tail and solar wind. The solar wind consists of
high-speed streams of plasma that emanate from the sun's outer atmosphere. Not
only did SWICS detect unexpected ions in the comet tail, it found that the tail
had a major impact on the surrounding solar wind.
For the first time at a comet, researchers detected O3+ oxygen
ions (atoms of oxygen with a positive charge because they have five electrons
instead of eight). This suggests that the solar wind ions, originally missing
most of their electrons, picked up some of their missing electrons when they
passed through McNaught's atmosphere. The comet served as a source of electrons,
said Michael Combi, a U-M space science professor who is an author of the paper.
SWICS also found that even at 160 million miles from the comet's
nucleus, the tail had slowed the solar wind to half its normal speed. The solar
wind would usually be about 435 miles per second at that distance from the sun,
but inside the comet's ion tail, it was less than 249 miles per second.
"This was very surprising to me," Combi said. "Way past the
orbit of Mars, the solar wind felt the disturbance of this little comet. It will
be a serious challenge for us theoreticians and computer modelers to figure out
In 1996, Ulysses passed through the tail of comet Hyakutake and
measurements indicated its tail didn't slow the solar wind at all.
The interaction between comets' tails and the solar wind has
been studied for decades. A comet's ion tail always points away from the sun,
whether the body is traveling toward or away from the sun along the comet's
elliptical orbit. It was this finding that eventually led in 1958 to the
discovery of solar wind. The magnetism and velocity of the solar wind are so
strong it pushes the comet's tail forward.
Solar wind is blamed for the lack of an atmosphere on Mars and
for geomagnetic storms that can cut out power on Earth. It is a major component
of space weather, which scientists study because if affects satellites and
humans in space.
As for what these observations say about the origins of the
solar system, scientists don't know just yet.
"The composition of comets tells us about conditions
approximately 4.5 billion years ago when the solar system was formed," Gloeckler
said. "Here we got a direct sample of this ancient material which gives us the
best information on cometary composition.
"We're still in the process of figuring out what it tells us,"
he said. "We're contributing part of the whole puzzle."
Space science professor Thomas Zurbuchen, a U-M author of the
paper, likened Ulysses' pass to putting your hand in the waters of Lake Michigan
and pulling out a fish.
"That's a pretty unlikely thing," Zurbuchen said. "And that is a
lot like what happened when we caught the tail of a comet that happened to pass
very near the sun.
"The benefits of such an observation are important," he said.
"They constrain the interactions of such comets with the sun, including how the
comets lose mass. They also examine the question of how a sudden injection of
neutral and cold material interacts with hot solar-like plasmas. That occurs in
other places of the universe and we were able to study it right here."
The paper is called "Encounter of the Ulysses Spacecraft with
the Ion Tail of Comet McNaught." Astrophysical Journal is the same journal that
published Eugene Parker's paper on the discovery of solar wind in 1958.
The Department of Atmospheric, Oceanic and Space Sciences is
part of the University of Michigan College of Engineering, which is ranked among
the top engineering schools in the country. Michigan Engineering boasts one of
the largest engineering research budgets of any public university, at more than
$130 million. Michigan Engineering has 11 departments and an NSF Engineering
Research Centers. Within those departments and the center, there is a special
emphasis on research in three emerging areas: nanotechnology and integrated
microsystems; cellular and molecular biotechnology; and information technology.
Michigan Engineering is seeking to raise $110 million for capital building
projects and program support in these areas to further research discovery.
Michigan Engineering's goal is to advance academic scholarship and market
cutting-edge research to improve public health and well-being.
About solar system:
The Solar System or solar system[a] consists of the Sun and the
other celestial objects gravitationally bound to it: the eight planets, their
165 known moons, three dwarf planets (Ceres, Pluto, and Eris and their four
known moons), and billions of small bodies. This last category includes
asteroids, Kuiper belt objects, comets, meteoroids, and interplanetary dust.
In broad terms, the charted regions of the Solar System consist of the Sun, four
terrestrial inner planets, an asteroid belt composed of small rocky bodies, four
gas giant outer planets, and a second belt, called the Kuiper belt, composed of
icy objects. Beyond the Kuiper belt lies the scattered disc, the heliopause, and
ultimately the hypothetical Oort cloud.
In order of their distances from the Sun, the planets are Mercury, Venus, Earth,
Mars, Jupiter, Saturn, Uranus, and Neptune. Six of the eight planets are in turn
orbited by natural satellites, usually termed "moons" after Earth's Moon, and
each of the outer planets is encircled by planetary rings of dust and other
particles. All the planets except Earth are named after gods and goddesses from
Greco-Roman mythology. The three dwarf planets are Pluto, the largest known
Kuiper belt object; Ceres, the largest object in the asteroid belt; and Eris,
which lies in the scattered disc.
About Researchers & Contact:
Department of Aerospace Engineering
Department of Atmospheric, Oceanic and Space Sciences
ADDRESS: 2429A Space Research Building 2143
PHONE: (734) 647-6835
FAX: (734) 615-9723
PERSONAL WEBPAGE: http://www-personal.engin.umich.edu/~thomasz/
Specializations & Research Interests
Developing new flight hardware to measure composition of plasmas in heliosphere
Exploring and fabricating new particle detectors technologies suitable for
future space missions
Developing and investigating new theoretical models for all major phenomena in
solar atmosphere and its expansion into the heliosphere as the solar wind
- Solar wind acceleration
- Formation and properties of solar wind magnetic field
- Propagation and acceleration of energetic particles
Developing and experimentally investigating new theoretical concepts and models
for interstellar heliospheric neutral gas and dust behavior and subsequent
ionization to form so-called pickup ion population
Developing new theoretical concepts and experimental exploration methods of
interaction between heliosphere and local interstellar medium
Ph.D., M.S., University of Bern
Honors, Awards and Accomplishments
Recipient, Presidential Early Career for Scientists and Engineers (PECASE) Award
Recipient, Young Researcher Award, Swiss National Science Foundation
Leading data analysis of active missions and of hardware development efforts,
Solar and Heliospheric Research Group.
Participant, development and calibration of several flight instruments (IND, ACE
Led UV suppression tests of flight sensors, developing database for random
scattering of UV in particles detectors.
Leading many data analysis projects finding new applications for composition
data, most recently as method to trace matter through the magnetosphere
Author or Coauthor, 20+ articles in refereed journals on solar and heliospheric
Participant, NASA Science and Technology definition team defining mission to the
Regular reviewer, major journals and proposals for NASA and NSF
Invited speaker, several international conferences and colloquia in many leading
Universities and Research Institutions
Session Chair and Conference Organizer for five Conferences
Institute for Physical Science and Technology
Department of Physics
Research Interests: Professor Gloeckler has contributed to the field of space
plasma physics through pioneering discoveries and the invention of instruments
carried on satellites and deep space probes, including the two Voyagers, Ulysses
and Cassini. His research combines measurements of the properties of matter in
the universe with careful interpretations that address a complex range of
questions relating to solar activity, planetary systems, and formation and
evolution of objects in the universe.
Office: CSS 3201
Eddress: gg10 at umail.umd.edu
Michael. R. Combi
Research Professor and Distinguished Research Scientist
Department of Atmospheric, Oceanic and Space Sciences
University of Michigan
For more information: