EMBARGOED UNTIL: 2 pm (EDT), July 10, 2003

Don Savage
NASA Headquarters, Washington
(Phone: 202/358-1547; E-mail: )

Nancy Neal
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-0039; E-mail: )

Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone: 410/338-4514; E-mail: )

Barbara Kennedy
Penn State University, University Park, PA
(Phone: 814/863-4682; E-mail: )

Michelle Cook
University of British Columbia, Vancouver, Canada
(Phone: 604/822-2048; E-mail: )

Tim Stephens
University of California, Santa Cruz, CA
(Phone: 831-459-2495; E-mail: )

Stuart Walpert
University of California, Los Angeles, CA
(Phone: 310-825-2585; E-mail: )

PRESS RELEASE NO.: STScI-PR03-19

HUBBLE HELPS CONFIRM OLDEST KNOWN PLANET

NASA's Hubble Space Telescope precisely measured the mass of the oldest
known planet in our Milky Way galaxy. At an estimated age of 13 billion
years, the planet is more than twice as old as Earth's 4.5 billion
years. It's about as old as a planet can be. It formed around a young,
sun-like star barely 1 billion years after our universe's birth in the
Big Bang. The ancient planet has had a remarkable history because it
resides in an unlikely, rough neighborhood. It orbits a peculiar pair of
burned-out stars in the crowded core of a cluster of more than 100,000
stars. The new Hubble findings close a decade of speculation and debate
about the identity of this ancient world. Until Hubble's measurement,
astronomers had debated the identity of this object. Was it a planet or
a brown dwarf? Hubble's analysis shows that the object is 2.5 times the
mass of Jupiter, confirming that it is a planet. Its very existence
provides tantalizing evidence that the first planets formed rapidly,
within a billion years of the Big Bang, leading astronomers to conclude
that planets may be very abundant in our galaxy.

To see and read more about the oldest known planet, click on:
http://hubblesite.org/news/2003/19

-end-

The Space Telescope Science Institute (STScI) is operated by the
Association of Universities for Research in Astronomy, Inc. (AURA), for
NASA, under contract with the Goddard Space Flight Center, Greenbelt,
MD. The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency (ESA).


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http://hubblesite.org/newscenter/archive/2003/19/text

Oldest Known Planet Identified


Full press release text:

Long before our Sun and Earth ever existed,
a Jupiter-sized planet formed around a
sun-like star. Now, 13 billion years later,
NASA's Hubble Space Telescope has
precisely measured the mass of this farthest
and oldest known planet. The ancient planet
has had a remarkable history because it has
wound up in an unlikely, rough neighborhood.
It orbits a peculiar pair of burned-out stars
in the crowded core of a globular star cluster.

The new Hubble findings close a decade of speculation and
debate as to the true nature of this ancient world, which takes
a century to complete each orbit. The planet is 2.5 times the
mass of Jupiter. Its very existence provides tantalizing
evidence that the first planets were formed rapidly, within a
billion years of the Big Bang, leading astronomers to conclude
that planets may be very abundant in the universe.

The planet now lies in the core of the ancient globular star
cluster M4, located 5,600 light-years away in the summer
constellation Scorpius. Globular clusters are deficient in
heavier elements because they formed so early in the universe
that heavier elements had not been cooked up in abundance in
the nuclear furnaces of stars. Some astronomers have
therefore argued that globular clusters cannot contain planets.
This conclusion was bolstered in 1999 when Hubble failed to
find close-orbiting "hot Jupiter"-type planets around the
stars of the globular cluster 47 Tucanae. Now, it seems that
astronomers were just looking in the wrong place, and that
gas-giant worlds orbiting at greater distances from their stars
could be common in globular clusters.

"Our Hubble measurement offers tantalizing evidence that
planet formation processes are quite robust and efficient at
making use of a small amount of heavier elements. This
implies that planet formation happened very early in the
universe," says Steinn Sigurdsson of Pennsylvania State
University.

"This is tremendously encouraging that planets are probably
abundant in globular star clusters," says Harvey Richer of the
University of British Columbia. He bases this conclusion on
the fact that a planet was uncovered in such an unlikely place,
orbiting two captured stars - a helium white dwarf and a
rapidly spinning neutron star - near the crowded core of a
globular cluster, where fragile planetary systems tend to be
ripped apart due to gravitational interactions with neighboring
stars.

The story of this planet's discovery began in 1988, when the
pulsar, called PSR B1620-26, was discovered in M4. It is a
neutron star spinning just under 100 times per second and
emitting regular radio pulses like a lighthouse beam. The
white dwarf was quickly found through its effect on the
clock-like pulsar, as the two stars orbited each other twice
per year. Sometime later, astronomers noticed further
irregularities in the pulsar that implied that a third object was
orbiting the others. This new object was suspected to be a
planet, but it could also be a brown dwarf or a low-mass star.
Debate over its true identity continued through the 1990s.

Sigurdsson, Richer, and their co-investigators settled the
debate by at last measuring the planet's actual mass through
some ingenious celestial detective work. They had exquisite
Hubble data from the mid-1990s, taken to study white dwarfs
in M4. Sifting through these observations, they were able to
detect the white dwarf orbiting the pulsar and measure its
color and temperature. Using evolutionary models computed
by Brad Hansen of the University of California, Los Angeles,
the astronomers estimated the white dwarf's mass. This in
turn was compared to the amount of wobble in the pulsar's
signal, allowing the astronomers to calculate the tilt of the
white dwarf's orbit as seen from Earth. When combined with
the radio studies of the wobbling pulsar, this critical piece of
evidence told them the tilt of the planet's orbit, too, and so the
precise mass could at last be known. With a mass of only 2.5
Jupiters, the object is too small to be a star or brown dwarf,
and must instead be a planet.

The planet has had a rough road over the last 13 billion years.
When it was born, it probably orbited its youthful yellow sun
at approximately the same distance Jupiter is from our Sun.
The planet survived blistering ultraviolet radiation, supernova
radiation, and shockwaves, which must have ravaged the
young globular cluster in a furious firestorm of star birth in its
early days. Around the time multi-celled life appeared on
Earth, the planet and star were plunging into the core of M4.
In this densely crowded region, the planet and its sun passed
close to an ancient pulsar, formed in a supernova when the
cluster was young, that had its own stellar companion. In a
slow-motion gravitational dance, the sun and planet were
captured by the pulsar, whose original companion was ejected
into space and lost. The pulsar, sun, and planet were
themselves flung by gravitational recoil into the less-dense
outer regions of the cluster. Eventually, as the star aged it
ballooned to a red giant and spilled matter onto the pulsar.
The momentum carried with this matter caused the neutron
star to "spin-up" and re-awaken as a millisecond pulsar.
Meanwhile, the planet continued on its leisurely orbit at a
distance of about 2 billion miles from the pair (approximately
the same distance Uranus is from our Sun).

It is likely that the planet is a gas giant, without a solid
surface like the Earth. Because it was formed so early in the
life of the universe, it probably doesn't have abundant
quantities of elements such as carbon and oxygen. For these
reasons, it is very improbable the planet would host life. Even
if life arose on, for example, a solid moon orbiting the planet, it
is unlikely to have survived the intense X-ray blast that
would have accompanied the spin-up of the pulsar.
Regrettably, it is unlikely that any civilization witnessed and
recorded the dramatic history of this planet, which began at
nearly the beginning of time itself.

The full team involved in this discovery is composed of Brad
Hansen (UCLA), Harvey Richer (UBC), Steinn Sigurdsson
(Penn State), Ingrid Stairs (UBC), and Stephen Thorsett
(UCSC).

Release Date: 2:00PM (EDT) July 10, 2003
Release Number: STScI-2003-19