Suspected Protoplanet May Really be a Distant Star
Donald Savage
Headquarters, Washington, DC
(Phone: 202/358-1547)
Nancy Neal
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-0039)
Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone: 410/338-4514)
RELEASE: 00-58
Follow-up observations of an unusual object initially
suspected to be the first directly detected planet outside our
solar system have shown that the object is too hot to be a planet.
Astronomers now believe it is more likely that the strange
object is a background star whose light has been dimmed and
reddened by interstellar dust, giving the illusion that it is in
the vicinity of the double star system in which it was initially
believed to have been a planet.
NASA’s Hubble Space Telescope photographed the mysterious
object, called TMR-1C, in 1997. The picture shows a bright dot at
the end of a long streamer of reflective dust stretching 135
billion miles (225 billion kilometers) back to the binary star
located 450 light-years away in the constellation Taurus the bull.
A light year is about 6 trillion miles.
In 1998, astronomer Susan Terebey of the Extrasolar Research
Corp., Pasadena, CA, reported her observation at a scientific
meeting as a possible young and hot “protoplanet” several times
the mass of Jupiter. Because of its potential importance and the
compelling nature of the image, NASA also released the picture to
the public with the caution that future observations would be
critical in verifying whether or not this object actually is a
planet.
Tereby initially proposed that the object had been ejected
from a double star system via a “slingshot” effect (interaction
with one of the stars or another giant planet). Since then
she has conducted follow-up observations with the 10-meter Keck
telescope in Mauna Kea, HI, to test her hypothesis.
Now, in results to be published in the May Astronomical
Journal, Tereby reports, “The new data do not lend weight to the
protoplanet interpretation and the results remain consistent with
the explanation that TMR-1C may be a background star. Although
the Hubble image is striking, there is the alternate possibility
that TMR-1C is an unrelated background star, seen, by chance,
projected close to the young star system. Finding a clearer
answer is difficult for an object as faint as TMR-1C.”
To better understand the nature of this faint object, Tereby
used the Keck telescope to measure TMR-1C’s temperature by
dissecting its light through spectroscopy. Much like the way a
prism disperses sunlight to make a colorful rainbow, a spectrum
breaks apart the light from the observed object. The relative
amounts of red and blue light help tell the object’s temperature.
Tereby and colleagues then constructed models of dust-
obscured objects to compare with the spectrum of TMR-1C and found
a corresponding temperature of greater than 4400 degrees
Fahrenheit (2700 degrees Kelvin) for TMR-1C. This is hotter than
the predicted temperatures of young giant planets.
“However the models are not yet reliable at such young ages,
so this test by itself is not conclusive,” Tereby cautions. “The
idea remains alive and well that there may be runaway planets and
brown dwarfs (small stars that failed to sustain nuclear fusion)
which formed via ejection from multiple star systems. Theoretical
models by several groups support this idea, and new searches —
including ours — are finding many new candidates in star-forming
regions. However at this time there is no strong evidence that
TMR-1C itself is a protoplanet.”
– end –
EDITOR’S NOTE: The Hubble image of TMR-1C and the initial press
release (from May 28, 1998) are available at:
