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 NMNH
Mineral Sciences Curator Dr. Timothy J. McCoy recently had an asteroid
named for him in recognition of his research in meteoritics, the study
of meteorites.
The asteroid is now known as Asteroid 4259 McCoy. It was discovered by Dr. Bobby Bus at Cerro Tololo, Chile,
in 1988. The official citation
for this naming is:
Timothy
J. McCoy (b. 1964) is a curator of the national meteorite collection at
the Smithsonian’s National Museum of Natural History in Washington, DC. His research has been crucial for
understanding the complex heating and melting events on the parent body of
the acapulcoite and lodranite meteorites.
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What’s in a name?
Asteroids are named through a detailed process, overseen by the
Smithsonian Astrophysics Observatory's Minor Planets Center. Once an asteroid is discovered,
multiple observations are needed to determine its orbit. The asteroid then receives a provisional designation, and
then a number. The person who
discovered the asteroid then proposes a name for it. Finally, the name is approved by the
International Astronomical Union. In the past, asteroids have been named for mythological features and
characters, pets, even famous musicians - such as the Beatles - but
increasingly they are being named for scientists like Dr. McCoy who have
made significant contributions to scientific fields related to asteroids. Of
the15,000 numbered asteroids, approximately one half of them are named, and
only a few thousand are named after people.
Asteroid 4259 McCoy joins three other stellar bodies named for
important Smithsonian staff - - Former Secretary I. Michael Heyman, Under
Secretary Dennis J. O’Connor, and former Under Secretary Constance Newman
also have asteroids named in their honor.
What’s
the difference between an asteroid and a meteorite?
Asteroids are bodies of rock and iron, usually 10-50 km in diameter, in
stable orbits around our solar system’s star, the Sun. Even with the most powerful
Earth-based telescopes, asteroids appear as just points of light, like
stars. Most of the
asteroids in our solar system are in a belt between the orbits of the
planets Mars and Jupiter. If
not for the powerful gravitational pull exerted by the massive planet
Jupiter, the hundreds of thousands of asteroids probably would have joined
together to become a planet during the formation of our solar
system.
 Meteorites
are pieces of asteroids. They
break off of asteroids during chance collisions with other asteroids
and can spend millions of years orbiting the sun before they fall
to Earth. As a meteorite
is entering the atmosphere, it is called a “meteor” or by
the better known term “shooting star”.
Meteorites range in mass from less than a gram to more than
50 tons. The largest meteorite, estimated to weigh more than 60 tons
and found in 1920, remains where it fell in Namibia. NMNH has the
largest and most important museum collection of meteorites in the
world. Over 20,000 specimens
from 10,000 different meteorites are in the collection.
To learn more about our collections and research in mineral
sciences,
click here.
Many of these meteorites were recovered in Antarctica by an
effort sponsored by the Smithsonian, NASA and the National Science
Foundation.
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Monument Draw Acapulcoite meteorite
showing areas of accumulated, melted metals.
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Dr.
McCoy’s Research
“Meteorites
are relics from the dawn of the solar system.
Asteroids are the source of
meteorites - when you look at them, you are really looking at the birth of
the solar system. In studying meteorites, I’m working on understanding how
the solar system originated”, says Dr. McCoy.
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His research is significant because he identified the stages that
meteorites undergo as they are transformed by radioactive heating. Asteroids formed out of materials
from the solar nebula, the cloud of gas and dust that produced the planets
and Sun. Meteorites
from these first, primitive asteroids are called “chondrites”. As asteroids are heated by the
early sun and by the radioactive elements they contain, lighter minerals
rise to the surface to form a crust, while denser, metallic minerals sink
to the center to form a core, the same type of differentiated structure as
the Earth. Dr. McCoy
discovered meteorites that record the first stages of melting and
differentiation that transform chondritic asteroids into differentiated
asteroids. Acapulcoite
meteorites (named for a meteorite that fell in Acapulco, Mexico in 1976)
record the first stage in the heating and melting process. The Monument Draw acapulcoite
meteorite, shown above, shows large veins of metal formed
as melted material began to accumulate into larger veins and migrate through the
asteroid. Lodranite
meteorites (named for a meteorite which fell in Lodran, India in 1868) are
residues, the materials left behind after melted metals migrate away. If this process proceeds to its
final stage, a planet like Earth is produced, with its differentiated
crust, mantle, and core.
Dr.
McCoy is continuing his research into the structure of asteroids by
participating in NASA’s Near Earth Asteroid Rendezvous (NEAR) mission. This mission, which is currently
orbiting asteroid 433 Eros for a year, is mapping the geology, mineralogy
and chemical composition of the surface of the asteroid. This data should provide an even
better view of how meteorites are related to one another on a body the
size of an asteroid. In
the fall of 2000, look for an exhibit on the NEAR mission and its
relationship to meteorites in the Constitution Avenue lobby of the Natural
History Museum.
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