Spitzer Captures Echo Of Dead Star's Rumblings

Jun 09, 2005
Spitzer Captures Echo Of Dead Star's Rumblings

An enormous light echo etched in the sky by a fitful dead star was spotted by the infrared eyes of NASA's Spitzer Space Telescope.
The surprising finding indicates Cassiopeia A, the remnant of a star that died in a supernova explosion 325 years ago, is not resting peacefully. Instead, this dead star likely shot out at least one burst of energy as recently as 50 years ago.

Image: Cassiopeia A: Death Becomes Her. Credit: NASA/JPL-Caltech/O. Krause (Steward Observatory)

"We had thought the stellar remains inside Cassiopeia A were just fading away," said Dr. Oliver Krause, University of Arizona, Tucson. "Spitzer came along and showed us this exploded star, one of the most intensively studied objects in the sky, is still undergoing death throes before heading to its final grave," he added.

Infrared echoes trace the dusty journeys of light waves blasted away from supernova or erupting stars. As the light waves move outward, they heat up clumps of surrounding dust causing them to glow in infrared light. The echo from Cassiopeia A is the first witnessed around a long-dead star and the largest ever seen. It was discovered by accident during a Spitzer instrument test.

"We had no idea that Spitzer would ever see light echoes," said Dr. George Rieke of the University of Arizona. "Sometimes you just trip over the biggest discoveries."

A supernova remnant like Cassiopeia A typically consists of an outer, shimmering shell of expelled material and a core skeleton of a once-massive star, called a neutron star. Neutron stars come in several varieties ranging from intensely active to silent. Typically, a star that has recently died will continue to act up. Consequently, astronomers were puzzled the star responsible for Cassiopeia A appeared to be silent so soon after its death.

The new infrared echo indicates the Cassiopeia A neutron star is active and suggests it may be an exotic, spastic type of object called a magnetar. Magnetars are like screaming dead stars, with eruptive surfaces that rupture and quake, pouring out tremendous amounts of high-energy gamma rays. Spitzer may have captured the "shriek" of such a star in the form of light zipping away through space and heating up its surroundings.

"Magnetars are very rare and hard to study, especially if they are no longer associated with their place of origin. If we have indeed uncovered one, then it will be just about the only one for which we know what kind of star it came from and when," Rieke said.

Astronomers first saw hints of the infrared echo in strange, tangled dust features that showed up in the Spitzer test image. When they looked at the same dust features again a few months later using ground-based telescopes, the dust appeared to be moving outward at the speed of light. Follow-up Spitzer observations taken one year later revealed the dust was not moving, but it was lit up by passing light.

A close inspection of the Spitzer pictures revealed a blend of at least two light echoes around Cassiopeia A, one from its supernova explosion, and one from a hiccup of activity that occurred around 1953. Additional Spitzer observations of these light echoes may help pin down their enigmatic source.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate. Science operations are conducted at the Spitzer Science Center, California Institute of Technology, Pasadena, Calif. Krause was lead author with Rieke of a study about the discovery appearing this week in the journal Science.

Source: NASA

Explore further: Russian, American ready for a year in space

add to favorites email to friend print save as pdf

Related Stories

Telescope to seek dust where other Earths may lie

Jan 22, 2015

The NASA-funded Large Binocular Telescope Interferometer, or LBTI, has completed its first study of dust in the "habitable zone" around a star, opening a new door to finding planets like Earth. Dust is a ...

Recommended for you

Russian, American ready for a year in space

6 hours ago

The Russian astronaut heading off for a year in space says he'll miss the natural landscapes on Earth. His American counterpart jokes he won't miss his twin brother.

Galaxy clusters collide—dark matter still a mystery

12 hours ago

When galaxy clusters collide, their dark matters pass through each other, with very little interaction. Deepening the mystery, a study by scientists at EPFL and the University of Edinburgh challenges the ...

Using 19th century technology to time travel to the stars

16 hours ago

In the late 19th century, astronomers developed the technique of capturing telescopic images of stars and galaxies on glass photographic plates. This allowed them to study the night sky in detail. Over 500,000 ...

Image: The colors of sunset over the ISS

18 hours ago

ESA astronaut Samantha Cristoforetti took these images from the International Space Station during her six-month mission. The Progress cargo ship and Soyuz crew spacecraft reflect sunlight as our star sets ...

Feud on Earth but peace in space for US and Russia

21 hours ago

Hundreds of kilometres below on Earth, their governments are locked in a standoff over Ukraine—but up in space, Russian cosmonauts and American astronauts are still working together side by side.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.