Steve Roy

Marshall Space Flight Center January 14, 2000

Huntsville, AL

Phone: 256-544-6535

Dr. Wallace Tucker

Chandra X-ray Observatory Center

Cambridge, MA

Phone: 617-496-7998

Barbara Kennedy

Penn State PIO

University Park, PA

Phone: 814-863-4682


Dr. Gordon Garmire

Penn State University

University Park, PA

Phone: 814-865-1117


Dr. Eric Feigelson

Penn State University

University Park, PA

Phone: 814-865-0162


CXC PR: 00-06

Chandra Finds X-ray Star Bonanza in the Orion Nebula

NASA’s Chandra X-ray Observatory has resolved nearly a thousand faint X-ray-emitting stars in a single
observation of young stars in the Orion Nebula. The discovery — the richest field of X-ray sources ever
obtained in the history of X-ray astronomy — will be presented on Friday, January 14, at the 195th
national meeting of the American Astronomical Society in Atlanta, Georgia.

The Orion region is a dense congregation of about 2,000 very young stars formed during the past few
million years. The discovery of such a wealth of X-ray stars in the closest massive star-forming region to
Earth (only 1,500 light years away) is expected to have a profound impact on our understanding of star
formation and evolution.

“We’ve detected X-rays from so many fantastic objects, such as very young massive stars and stars so
small that they may evolve into brown dwarfs,” said Gordon Garmire, Evan Pugh Professor at Penn State
University, University Park. “Chandra’s superb angular resolution has resolved this dense cluster of stars
with arcsecond accuracy and unsurpassed sensitivity.”

Garmire leads the team using Chandra’s ACIS detector, the Advanced CCD Imaging Spectrometer,
conceived and developed for NASA by Penn State University and the Massachusetts Institute of

The brilliant Orion region has awed humankind for millennia. The most massive and brightest of these
nascent stars are in the Orion Trapezium, which illuminates the Orion Nebula, also known as Messier 42.
The Trapezium and its luminous gas can be seen with the unaided eye in the winter sky in the “sword” of
the Orion constellation.

Young stars, such as those found in Orion, are known to be much brighter in X-rays than middle-aged
stars such as the Sun. The elevated X-ray emission is thought to arise from violent flares in strong
magnetic fields near the surfaces of young stars. The Sun itself was probably thousands of times
brighter in X-rays during its first few million years.

Although the enhanced magnetic activity of young stars has been known for some time, the physical
causes and evolution of the activity are poorly understood, according to Dr. Eric Feigelson, professor of
astronomy and astrophysics at Penn State.

“With hundreds of stars observed simultaneously, possessing a wide range of properties such as mass
and rotation rates, we hope the Orion observation will help unravel the astrophysical principles underlying
this phenomenon,” Feigelson said. “X-ray astronomy now penetrates as deeply into the clouds as the
best infrared and optical telescopes, permitting us to study high-energy processes during the earliest
phases of star formation.”

“This Chandra image is a milestone in the field of X-ray astronomy and very gratifying to me personally,”
said Garmire. “Chandra’s sensitivity is 20 times better than achieved with the best previous X-ray

A number of the ACIS X-ray sources in the Orion observation have special importance. Several are
associated with a distinct cluster of higher-mass stars deeply embedded within the murky Orion
Molecular Cloud, including the infrared-luminous Becklin-Neugebauer object.

“This is the first time X-ray astronomy has resolved individual massive stars still embedded in their natal
cloud,” said Dr. Leisa Townsley, research associate in astronomy and astrophysics at Penn State.

At least three ACIS sources are associated with cluster members with masses so small (roughly 1/20th
of the Sun’s mass), that they will evolve into brown dwarfs rather than true stars.

“They more closely resemble proto-Jupiters than proto-stars,” said Dr. Yohko Tsuboi, visiting research
scholar in astronomy and astrophysics at Penn State. “Over a dozen X-ray sources have no known
counterpart, even in the most sensitive Hubble Space Telescope or infrared studies. These too may be
very low-mass stars.”

The ACIS team studying the Orion X-ray source includes Profs. Feigelson and Garmire and research
scientists Patrick Broos, Leisa Townsley, and Yohko Tsuboi at Penn State; Steven Pravdo at the Jet
Propulsion Laboratory; and Lynne Hillenbrand at the California Institute of Technology.

NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. TRW, Inc.,
Redondo Beach, CA, is the prime contractor for the spacecraft. The Smithsonian’s Chandra X-ray Center
controls science and flight operations from Cambridge, MA.

To follow Chandra’s progress or download images visit the Chandra sites at:



A Web site associated with this press release,
provides high-resolution digital images (JPEG, TIFF and PostScript formats) and hypertext links to images
of the Orion Nebula at non-X-ray wavelengths plus related material.


Chandra Image of the Orion Nebula Star Cluster

This X-ray image shows about a thousand X-ray emitting young stars in the Orion Nebula star cluster.
The X rays are produced in the multimillion degree upper atmospheres of these stars. At a distance of
about 1800 light years, this cluster is the closest massive star forming region to Earth. It is well-known in
the night sky because it illuminates the Orion Nebula. The region shown in this image is about 10 light
years across. The bright stars in the center are part of the Trapezium, an association of very young
stars with ages less than a million years. The dark vertical and horizontal lines, and the streaks from the
brightest stars are instrumental effects.

Image made with the Advanced CCD Imaging Spectrometer (ACIS)

Credit: NASA/PSU