Strong stellar gusts spotted in nearby massive star
Posted: July 25, 2001

A dramatic infrared image released by the Gemini Observatory sheds new light on the early stages of the formation of giant stars in our galaxy. The image, taken by the Gemini North telescope on Hawaii's Mauna Kea, reveals remarkable details in a nebula of gas and dust expelled from a young star named AFGL 2591. This expulsion is a common feature in the formation of stars similar in size to the Sun, but it is far less common in their massive counterparts.

Infrared image of a young star named AFGL 2591. Photo: Gemini Observatory/National Science Foundation/C. Aspin
"Almost everything in this set of infrared images would be invisible with an optical telescope, since it is occurring within a dense molecular cloud of gas and dust," says Gemini scientist Colin Aspin, who made the observation. "Gemini's unparalleled sensitivity and resolution in the infrared allows us to move beyond simply detecting such structures to being able to study them in great detail."

"These images only hint at the potential for a large, ground-based telescope to 'see' through the veil of material that surrounds young stars," says Wayne Van Citters, acting director of the National Science Foundation (NSF) Astronomical Sciences Division. NSF is the executive agency for the international Gemini partnership.

AFGL 2591 is located within the Milky Way more than 3,000 light-years from Earth, in the constellation of Cygnus. Over the course of the last few thousand years, it has created a vast expanding nebula larger than 500 times the diameter of our solar system. The star is at least 10 times the size of the Sun, and over 20,000 times as bright, but perhaps only one million years old.

The wispy white and blue structure in the expanding nebula to the right of the young star is a huge outflow of gas and dust driven by the infall of material onto the star's surface. Gemini scientists believe that the outflow is likely occurring symmetrically around the star - a second giant-sized expanding nebula to the left of the star is hidden from view by a dense and extensive disk (or torus) of material encircling AFGL 2591.

"We strongly suspect the outflow occurs on both sides of the star in a bipolar structure, because we detect faint traces of gas at that location which indicate interactions between the outflowing gas and the material forming the parent molecular cloud," says Aspin, a scientific staff member at the Gemini Observatory International Headquarters in Hilo, HI.

"A unique feature of this object is a series of four distinct rings of nebulosity. These rings suggest that the expulsion of the material is not constant with time, but rather has occurred several times over the lifetime of the object," he adds. "Studying the structure and velocity of these rings, and their relation to the infalling material, will allow us to better understand why such features are created and what functions they serve."

This false-color image of a young star named AFGL 2591 shows some high-resolution details in the expanding outflow of gas and dust around the massive star that are not fully visible in the color version of the image. AFGL 2591 is located within the Milky Way more than 3,000 light-years from Earth, in the constellation of Cygnus. Photo: Gemini Observatory/National Science Foundation/C. Aspin
This striking image is part of a series of early images taken with the Gemini Near Infrared Imager (NIRI) instrument during its commissioning on the Gemini North telescope. Once fully operational later this year, NIRI will be the prime near-infrared instrument on Gemini North.

The Gemini Observatory is an international collaboration that has built two identical 8-meter telescopes.

The telescopes are located at Mauna Kea, Hawaii, (Gemini North) and Cerro Pachon in central Chile (Gemini South), and hence provide full coverage of both hemispheres of the sky. Both telescopes incorporate new technologies that allow large, relatively thin mirrors under active control to collect and focus both optical and infrared radiation from space. Gemini North recently began science operations and Gemini South is scheduled to begin scientific operations in August 2001.

The Gemini Observatory is managed by the Association of Universities for Research in Astronomy (AURA), Inc. under a cooperative agreement with the National Science Foundation (NSF).

The other Gemini partnership research agencies include: the UK Particle Physics and Astronomy Research Council (PPARC), the Canadian National Research Council (NRC), the Chilean Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT), the Australian Research Council (ARC), the Argentinean Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) and the Brazilian Conselho Nacional de Pesquisas Cientificas e Tecnologicas (CNPq).