Infrared echoes give NASA's Spitzer a supernova flashback

Oct 01, 2008
Cassiopeia A is among the best-studied supernova remnants. This image blends data from NASA's Spitzer (red), Hubble (yellow), and Chandra (green and blue) observatories. Credit: NASA/JPL-Caltech/STScI/CXC/SAO

Hot spots near the shattered remains of an exploded star are echoing the blast's first moments, say scientists using data from NASA's Spitzer Space Telescope.

Eli Dwek of NASA's Goddard Space Flight Center in Greenbelt, Md. and Richard Arendt of the University of Maryland, Baltimore County, say these echoes are powered by radiation from the supernova shock wave that blew the star apart some 11,000 years ago. "We're seeing the supernova's first flash," Dwek says.

Other Spitzer researchers discovered hot spots near the Cassiopeia A supernova remnant and recognized their importance as light echoes of the original blast. Dwek and Arendt used Spitzer data to probe this hot dust and pin down the cause of the echoes more precisely.

Six knots of silicate dust near the remnant show temperatures between -280° and -190° Fahrenheit. Although this might seem frigid by Earthly standards, such temperatures are downright hot compared to typical interstellar dust.

Writing in the October 1 issue of The Astrophysical Journal, the scientists show that the only event that could make the grains this hot is the powerful and short-lived pulse of ultraviolet radiation and X-rays that heralded the death of the star. The flash was a hundred billion times brighter than the sun but lasted only a day or so.

"They've identified the precise event during the demolition of the star that produces the echo we see," says Michael Werner, the Project Scientist for Spitzer at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Light from the explosion reached Earth in the 17th century, but no one noticed. The Spitzer find gives astronomers a second chance to study the supernova as it unfolds.

Although the explosion originally escaped detection, its aftermath -- a hot, expanding gas cloud known as Cassiopeia A (Cas A, for short) -- is one of the best-studied supernova remnants. The blast zone lies 11,000 light-years away in the constellation Cassiopeia.

When a massive star runs out of nuclear fuel, its core collapses into a superdense, city-sized object called a neutron star. As the neutron star forms, it stiffens and rebounds. This triggers a mammoth shock wave that blows the star's outer layers to smithereens. The exiting shock creates a high-energy flash that precedes the supernova's rise in visible light.

Evidence for a flash associated with this "shock breakout" existed only in computer simulations until January 9, 2008. That's when NASA's Swift satellite detected a 5-minute-long X-ray pulse from galaxy NGC 2770. A few days later, a new supernova -- designated SN 2008D -- appeared in the galaxy.

The infrared echoes from Cas A arise from dust clouds about 160 light-years farther away than the remnant. The supernova's initial radiation pulse expands through space at the speed of light, then encounters the clouds and heats their dust grains. The dust, in turn, reradiates the energy at infrared wavelengths.

The breakout radiation took 160 years to reach the clouds and, once heated, the dust's infrared energy had to make up the same distance. This extra travel time results in a 320-year offset between the supernova's initial outward-moving flash and arrival of the dust's infrared echo at Earth. The researchers plan to use the echoes to paint an intimate portrait of the explosion, the star, and the immediate environment.

Light from the Cas A supernova first reached Earth in the late 1600s, but no one back then reported seeing a new star. On August 16, 1680, the English astronomer John Flamsteed might have seen the supernova without recognizing it. He recorded a faint naked-eye star near the position of Cas A, but none exists there now.

Source: NASA's Goddard Space Flight Center

Explore further: Image: Multicoloured view of supernova remnant

add to favorites email to friend print save as pdf

Related Stories

Image: Multicoloured view of supernova remnant

31 minutes ago

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make ...

Two spiral galaxies in the process of merging

Dec 12, 2014

At this time of year, there are lots of gatherings often decorated with festive lights. When galaxies get together, there is the chance of a spectacular light show as is the case with NGC 2207 and IC 2163

10 facts about the Milky Way

Dec 04, 2014

The Milky Way Galaxy is an immense and very interesting place. Not only does it measure some 100,000–120,000 light-years in diameter, it is home to planet Earth, the birthplace of humanity. Our Solar System ...

Chandra's archives come to life

Oct 22, 2014

Every year, NASA's Chandra X-ray Observatory looks at hundreds of objects throughout space to help expand our understanding of the Universe. Ultimately, these data are stored in the Chandra Data Archive, ...

Image: The Pillars of Creation

Oct 01, 2014

The Pillars of Creation (seen above) is an image of a portion of the Eagle nebula (M16) taken by Hubble Space Telescope in 1995. It soon became one of the most iconic space images of all time. The Eagle nebula ...

Cygnus OB2: Probing a nearby stellar cradle

Nov 08, 2012

(Phys.org)—The Milky Way and other galaxies in the universe harbor many young star clusters and associations that each contain hundreds to thousands of hot, massive, young stars known as O and B stars. ...

Recommended for you

Image: Multicoloured view of supernova remnant

10 hours ago

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make ...

Ultra-luminous X-ray sources in starburst galaxies

10 hours ago

Ultra-luminous X-ray sources (ULXs) are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. ULXs are rare. Most galaxies (including ...

When a bright light fades

10 hours ago

Astronomer Charles Telesco is primarily interested in the creation of planets and stars. So, when the University of Florida's giant telescope was pointed at a star undergoing a magnificent and explosive death, ...

Image: Horsehead nebula viewed in infrared

10 hours ago

Sometimes a horse of a different color hardly seems to be a horse at all, as, for example, in this newly released image from NASA's Spitzer Space Telescope. The famous Horsehead nebula makes a ghostly appearance ...

The Milky Way's new neighbour

11 hours ago

The Milky Way, the galaxy we live in, is part of a cluster of more than 50 galaxies that make up the 'Local Group', a collection that includes the famous Andromeda galaxy and many other far smaller objects. ...

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.