White Dwarfs & Planetary Nebulas

R Aquarii, All Wavelengths

Credit: X-ray: NASA/CXC/SAO/R. Montez et al.; Optical: Data: NASA/ESA/STScI, Enhanced processing by Judy Schmidt (CC BY-NC-SA). X-ray/Optical composite processing by CXC/N. Wolk & K.Arcand; Sonification: NASA/CXC/SAO/K.Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)

The system called R Aquarii unfolds dramatically through the eyes of NASA’s Chandra X-ray Observatory (purple) and Hubble Space Telescope (red and blue). The spectacular structures outlined in the Hubble data are old notes, or in other words, evidence from outbursts generated by a pair of stars buried at the center of the image. X-rays from Chandra reveal how a jet from one of these stars — a cool stellar ember known as a white dwarf — is banging into the material surrounding it. This high-powered flow creates shock waves, similar to sonic booms from planes that move faster than the speed of sound. The other player with the white dwarf in this interstellar duet is a red giant star. As they orbit each other, the white dwarf pulls material from the red giant onto its surface. Over time, enough of this material accumulates and triggers an explosion. Astronomers have seen such outbursts over recent decades and this dynamic chorus will likely go on for millennia to come.

There are some objects in space that are so photogenic that their images get circulated far beyond the regular confines of the astronomical community. NASA’s Hubble Space Telescope helped bring attention to the Cat’s Eye when its striking first image was released in 1994. Since then, Hubble has returned to the Cat’s Eye while other telescopes that detect different kinds of light — including NASA’s Chandra X-ray Observatory — have also observed it.

Cat's Eye Nebula (NGC 6543)
Credit: X-ray: NASA/CXC/RIT/J.Kastner et al.; Optical: NASA/STScI

What is the Cat’s Eye? It is officially categorized as a planetary nebula, a misleading label that stuck from its origins in the 19th century. Because these objects look like planets through small telescopes, astronomers named them “planetary nebulas”.

Today, astronomers know these objects have little to do with planets. They are, in fact, a stage toward the end life of stars like our Sun. After the star uses most of its fuel, it puffs off its outer layers while the core shrinks to a stellar nub. Winds and radiation from the star’s core — known as a white dwarf — push and energize the discarded material, sometimes creating spectacular structures. The Cat’s Eye, also known more formally as NGC 6543 and apparently the name of a Stephen King movie from 1985, is a planetary nebula about 3,200 light years from the Earth in the direction of the Draco constellation.

Planetary Nebulas: NGC 6302, IC 418, NGC 3242, NGC 7662, NGC 7027, and NGC 2371.
Credit: X-ray: NASA/CXC/RIT/SAO/J.Kastner; Optical: NASA/ESA/AURA/STScI/Univ. Washington, B.Balick

Sometimes the names of objects are deeply misleading. For example, starfish are not actually fish (they are echinoderms) and guinea pigs are not related to pigs in any way (they are rodents). Similarly, planetary nebulas have nothing to do with planets. They were misnamed when scientists looking through small telescopes in the 19th century thought that these objects looked like planets.

Today, astronomers know that a planetary nebula actually represents a phase that stars like our Sun experience after they use up much of their fuel. After cooling and expanding through a “red giant” phase when it begins to expel its outer layers, such a star leaves behind a type of dense and smaller star called a white dwarf. The previously jettisoned shells of gas remain for a relatively short time in cosmic terms — tens of thousands of years — before dissipating into space. Meanwhile they are illuminated and energized by the white dwarf at the center of the system. This will happen to our Sun, but not for another 5 billion years or so.

White Dwarf KPD 0005+5106
Credit: Illustration: NASA/CXC/M. Weiss; X-ray (Inset): NASA/CXC/ASIAA/Y.-H. Chu, et al.

A team of scientists used NASA's Chandra X-ray Observatory and ESA's XMM-Newton to investigate some unusual X-ray activity of a white dwarf star, as reported in our latest press release. The data suggest this white dwarf is blasting a companion object, which is either a low-mass star or planet, with waves of heat and radiation while pulling it apart through gravitational force.

Most stars, including the Sun, will become "white dwarfs" after they begin to run out of fuel, expand and cool into a red giant, and then lose their outer layers. This evolution leaves behind a stellar nub that slowly fades for billions of years. An artist's illustration shows a white dwarf as the blue-white sphere near the center.

More Information
Sonification Credit: NASA/CXC/SAO/K. Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)

This latest installment from our data sonification series features three diverse cosmic scenes. In each, astronomical data collected by NASA's Chandra X-ray Observatory and other telescopes are converted into sounds. Data sonification maps the data from these space-based telescopes into a form that users can hear instead of only see, embodying the data in a new form without changing the original content.

IC 4593
Credit: X-ray: NASA/CXC/Columbia Univ./A. Johnson et al.; Optical: NASA/STScI

On Earth, amethysts can form when gas bubbles in lava cool under the right conditions. In space, a dying star with a mass similar to the Sun is capable of producing a structure on par with the appeal of these beautiful gems.

As stars like the Sun run through their fuel, they cast off their outer layers and the core of the star shrinks. Using NASA's Chandra X-ray Observatory, astronomers have found a bubble of ultra-hot gas at the center of one of these expiring stars, a planetary nebula in our galaxy called IC 4593. At a distance of about 7,800 light years from Earth, IC 4593 is the most distant planetary nebula yet detected with Chandra.

This new image of IC 4593 has X-rays from Chandra in purple, invoking similarities to amethysts found in geodes around the globe. The bubble detected by Chandra is from gas that has been heated to over a million degrees. These high temperatures were likely generated by material that blew away from the shrunken core of the star and crashed into gas that had previously been ejected by the star.

Chandra Archive Collection: A Montage of Light From Space
Credit: NASA/CXC/SAO, NASA/STScI, NASA/JPL-Caltech/SSC, ESO/NAOJ/NRAO, NRAO/AUI/NSF, NASA/CXC/SAO/PSU, and NASA/ESA

Humanity has "eyes" that can detect all different types of light through telescopes around the globe and a fleet of observatories in space. From radio waves to gamma rays, this "multiwavelength" approach to astronomy is crucial to getting a complete understanding of objects in space.

This compilation gives examples of images from different missions and telescopes being combined to better understand the science of the universe. Each of these images contains data from NASA's Chandra X-ray Observatory as well as other telescopes. Various types of objects are shown (galaxies, supernova remnants, stars, planetary nebulas), but together they demonstrate the possibilities when data from across the electromagnetic spectrum are assembled.

For decades, astronomers have known about irregular outbursts from the double star system V745 Sco, which is located about 25,000 light years from Earth. Astronomers were caught by surprise when previous outbursts from this system were seen in 1937 and 1989. When the system erupted on February 6, 2014, however, scientists were ready to observe the event with a suite of telescopes including NASA’s Chandra X-ray Observatory.

In biology, "symbiosis" refers to two organisms that live close to and interact with one another. Astronomers have long studied a class of stars – called symbiotic stars – that co-exist in a similar way. Using data from NASA’s Chandra X-ray Observatory and other telescopes, astronomers are gaining a better understanding of how volatile this close stellar relationship can be.

R Aquarii (R Aqr, for short) is one of the best known of the symbiotic stars. Located at a distance of about 710 light years from Earth, its changes in brightness were first noticed with the naked eye almost a thousand years ago. Since then, astronomers have studied this object and determined that R Aqr is not one star, but two: a small, dense white dwarf and a cool red, giant star.