A Surprisingly Bright Superbubble

This composite image shows a superbubble in the Large Magellanic Cloud (LMC), a small satellite galaxy of the Milky Way located about 160,000 light years from Earth. Many new stars, some of them very massive, are forming in the star cluster NGC 1929, which is embedded in the nebula N44, so named because it is the 44th nebula in a catalog of such objects in the Magellanic Clouds. The massive stars produce intense radiation, expel matter at high speeds, and race through their evolution to explode as supernovas. The winds and supernova shock waves carve out huge cavities called superbubbles in the surrounding gas. X-rays from NASA's Chandra X-ray Observatory (blue) show hot regions created by these winds and shocks, while infrared data from NASA's Spitzer Space Telescope (red) outline where the dust and cooler gas are found. The optical light from the 2.2-m Max-Planck-ESO telescope (yellow) in Chile shows where ultraviolet radiation from hot, young stars is causing gas in the nebula to glow.

A long-running problem in high-energy astrophysics has been that some superbubbles in the LMC, including N44, give off a lot more X-rays than expected from models of their structure. These models assume that hot, X-ray emitting gas has been produced by winds from massive stars and the remains of several supernovas. A Chandra study published in 2011 showed that there are two extra sources of N44’s X-ray emission not included in these models: supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls. The Chandra observations also show no evidence for an enhancement of elements heavier than hydrogen and helium in the cavities, thus ruling out this possibility as a third explanation for the bright X-ray emission. Only with long observations making full use of the capabilities of Chandra has it now become possible to distinguish between different sources of the X-rays produced by superbubbles.

Image credit: X-ray: NASA/CXC/U.Mich./S.Oey, IR: NASA/JPL, Optical: ESO/WFI/2.2-m

Caption credit: Harvard-Smithsonian Center for Astrophysics

Hubble Watches Star Clusters on a Collision Course

Astronomers using data from NASA's Hubble Space Telescope caught two clusters full of massive stars that may be in the early stages of merging. The 30 Doradus Nebula is 170,000 light-years from Earth. What at first was thought to be only one cluster in the core of the massive star-forming region 30 Doradus has been found to be a composite of two clusters that differ in age by about one million years.

The entire 30 Doradus complex has been an active star-forming region for 25 million years, and it is currently unknown how much longer this region can continue creating new stars. Smaller systems that merge into larger ones could help to explain the origin of some of the largest known star clusters. The Hubble observations, made with the Wide Field Camera 3, were taken Oct. 20-27, 2009. The blue color is light from the hottest, most massive stars; the green from the glow of oxygen; and the red from fluorescing hydrogen.

Image Credit: NASA, ESA, and E. Sabbi (ESA/STScI)

Saturday Space Sight: A Celestial Swan and Butterfly

This image from the Hubble Space Telescope shows planetary nebula NGC 7026. Located just beyond the tip of the tail of the constellation of Cygnus (The Swan), this butterfly-shaped cloud of glowing gas and dust is the wreckage of a star similar to the sun.

Planetary nebulae, despite their name, have nothing to do with planets. They are, in fact, a relatively short-lived phenomenon that occurs at the end of the life of mid-sized stars. As a star’s nuclear fuel runs out, its outer layers are puffed out, leaving only the hot core of the star behind.  As the gaseous envelope heats up, the atoms in it are excited, and it lights up like a fluorescent sign.

Fluorescent lights on Earth get their bright colors from the gases with which they are filled. Neon signs, famously, produce a bright red color, while ultraviolet lights (black lights) typically contain mercury. The same is true for nebulae: their vivid colors are produced by the mix of gases present in them.

This image was produced by the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. A version of it was entered into the Hubble’s Hidden Treasures Competition by contestant Linda Morgan-O’Connor. Hidden Treasures is an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public.

Image Credit ESA/NASA

Uncovering the Veil (Nebula)

The Veil Nebula, left behind by the explosion of a massive star thousands of years ago, is one of the largest and most spectacular supernova remnants in the sky.

The image was taken with Hubble's Wide Field Planetary Camera 2 in November 1994 and August 1997.

Image Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: J. Hester (Arizona State University)

Within the Realm of a Dying Star

The NASA/ESA Hubble Space Telescope has been on the forefront of research into the lives of stars like our sun. At the ends of their lives, these stars run out of nuclear fuel in a phase that is called the preplanetary or protoplanetary nebula stage. This Hubble image of the Egg Nebula shows one of the best views to date of this brief, but dramatic, phase in a star’s life.

During the preplanetary nebula phase, the hot remains of an aging star in the center of the nebula heat it up, excite the gas and make it glow over several thousand years. The short lifespan of preplanetary nebulae means there are relatively few of them in existence at any one time. Moreover, they are very dim, requiring powerful telescopes to be seen. This combination of rarity and faintness means they were only discovered comparatively recently. The Egg Nebula, the first to be discovered, was first spotted less than 40 years ago, and many aspects of this class of object remain shrouded in mystery.

At the center of this image, and hidden in a thick cloud of dust, is the nebula’s central star. While scientists can’t see the star directly, four searchlight beams of light coming from it shine out through the nebula. Researchers hypothesize that ring-shaped holes in the thick cocoon of dust, carved by jets coming from the star, let the beams of light emerge through the otherwise opaque cloud. The precise mechanism by which stellar jets produce these holes is not known, but one explanation is that a binary star system, rather than a single star, exists at the center of the nebula.

The onion-like layered structure of the more diffuse cloud surrounding the central cocoon is caused by periodic bursts of material being ejected from the dying star. The bursts typically occur every few hundred years.

This image is produced from exposures in visible and infrared light from Hubble’s Wide Field Camera 3.

Image Credit: ESA/Hubble, NASA

A New View of the Tarantula Nebula

To celebrate its 22nd anniversary in orbit, the Hubble Space Telescope released a dramatic new image of the star-forming region 30 Doradus, also known as the Tarantula Nebula because its glowing filaments resemble spider legs. A new image from all three of NASA's Great Observatories--Chandra, Hubble, and Spitzer--has also been created to mark the event.

The nebula is located in the neighboring galaxy called the Large Magellanic Cloud, and is one of the largest star-forming regions located close to the Milky Way. At the center of 30 Doradus, thousands of massive stars are blowing off material and producing intense radiation along with powerful winds. The Chandra X-ray Observatory detects gas that has been heated to millions of degrees by these stellar winds and also by supernova explosions. These X-rays, colored blue in this composite image, come from shock fronts--similar to sonic booms--formed by this high-energy stellar activity.

The Hubble data in the composite image, colored green, reveals the light from these massive stars along with different stages of star birth, including embryonic stars a few thousand years old still wrapped in cocoons of dark gas. Infrared emission data from Spitzer, seen in red, shows cooler gas and dust that have giant bubbles carved into them. These bubbles are sculpted by the same searing radiation and strong winds that comes from the massive stars at the center of 30 Doradus.

Image Credits: X-ray: NASA/CXC/PSU/L.Townsley et al.; Optical: NASA/STScI; Infrared: NASA/JPL/PSU/L.Townsley et al.