ALMA and Webb Unveil the Hidden Heart of the Butterfly Nebula

The James Webb Space Telescope (JWST) has captured unprecedented details of the Butterfly Nebula (NGC 6302), a planetary nebula located about 3,400 light-years away in the constellation Scorpius. To gain a complete view of this complex object, astronomers combined Webb’s infrared observations with data from the Atacama Large Millimeter/submillimeter Array (ALMA), whose ability to trace cold gas and dust provides essential context to Webb’s images.

While Webb revealed the hot central star and the intricate ionized gas structures within the nebula, ALMA traced the cold molecular gas and dust forming the dense torus at its core. This combination shows how the torus shapes the bipolar “wings” of the nebula and explains why the central star remained hidden for so long. Together, JWST and ALMA provide a comprehensive view of both the hot and cold components of the Butterfly Nebula, offering new insights into the final stages of stellar evolution.

The synergy between the two observatories also uncovered surprising chemistry in the Butterfly Nebula. Webb detected complex carbon-based molecules in an environment expected to be oxygen-rich, while ALMA data revealed large crystalline dust grains in the central torus. These findings challenge existing models of how molecules and dust form and survive in such extreme conditions.

By combining their complementary strengths, ALMA and Webb are reshaping our understanding of how dying stars enrich the interstellar medium with gas, dust, and heavy elements. These observations demonstrate the power of international collaboration between ground- and space-based facilities, advancing our knowledge of stellar evolution and the cosmic cycle of matter.

Additional information

This text was adapted from the original news note released by the European Space Agency (ESA) James Webb Space Telescope (JWST) website.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF), and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan, and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of ALMA's construction, commissioning, and operation.

Webb is the largest, most powerful telescope ever launched into space. Under an international collaboration agreement, ESA provided the telescope’s launch service, using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also provided the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.

Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).

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