Eta Carinae

Eta Car is a massive star, but it's not as bright as it used to be. Now visible only in binoculars or a small telescope, Eta Carinae has a history of spectacular flaring and fading behavior.
In fact, in April of 1843 Eta Car briefly became second only to Sirius as the brightest star in planet Earth's night sky, even though at a distance of about 7,500 light-years, it is about 800 times farther away. Surrounded by a complex and evolving nebula, Eta Carinae is seen near the center of this false-color infrared image, constructed using data from the Midcourse Space Experiment satellite, which mapped the galactic plane in 1996.
In the picture, wispy, convoluted filaments are clouds of dust glowing at infrared wavelengths. Astronomers hypothesize that Eta Car itself will explode as a supernova in the next million years. Massive Eta Car is considered a candidate for a hypernova explosion and the potential source of future gamma-ray bursts.
Image from NASA

Z Camelopardalis

This composite image shows Z Camelopardalis, or Z Cam, a double-star system. The Z Cam system features a collapsed, dead star, called a white dwarf, and its companion star, as well as a ghostly shell around the system. The massive shell provides evidence of lingering material ejected during, and swept up by, a powerful explosion that occurred a few thousand years ago.
The image combines data gathered from the far-ultraviolet and near-ultraviolet detectors on NASA's Galaxy Evolution Explorer on Jan. 25, 2004. The orbiting observatory first began imaging Z Cam in 2003.
Z Cam is the largest white object in the image, located near the center. Parts of the shell are seen as a wispy, yellowish feature below and to the right of Z Cam, and as two large, whitish, perpendicular lines on the left.
Z Cam was one of the first known recurrent dwarf nova, meaning it erupts in a series of small, hiccup-like blasts, unlike classical novae, which undergo a massive explosion.
Image credit: NASA/JPL-Caltech

Red Rectangle

This intriguing image of the intriguing ladder-like structures surrounding a dying star reveals startling new details of one of the most unusual nebulae known in our Milky Way. Cataloged as HD 44179, this nebula is more commonly called the "Red Rectangle" because of its unique shape and color as seen with ground-based telescopes.
This Hubble Space Telescope image reveals a wealth of new features in the Red Rectangle that cannot be seen with ground-based telescopes looking through the Earth's turbulent atmosphere.
Hubble's sharp pictures show that the Red Rectangle is not really rectangular, but has an overall X-shaped structure, which arises from outflows of gas and dust from the star in the center. The outflows are ejected from the star in two opposing directions, producing its peculiar shape. Also remarkable are straight features that appear like rungs on a ladder, making the Red Rectangle look similar to a spider web, a shape unlike that of any other known nebula.
The star in the center of the Red Rectangle is one that began its life as a star similar to our sun. It is now nearing the end of its lifetime, and is in the process of ejecting its outer layers to produce the visible nebula. The shedding of the outer layers began about 14,000 years ago. Eventually, the star will have become smaller and hotter and begin to release a flood of ultraviolet light into the surrounding nebula; at that time, gas in the nebula will begin to fluoresce, producing what astronomers call a planetary nebula.
Image credit: NASA, ESA, Hans Van Winckel (Catholic University of Leuven, Belgium), and Martin Cohen (University of California, Berkeley)

A Red Supergiant's Light Echo

This Hubble Space Telescope image of the star V838 Monocerotis reveals dramatic changes in the illumination of surrounding dusty cloud structures. The effect, called a light echo, unveiled never-before-seen dust patterns when the star suddenly brightened for several weeks in early 2002.
A light echo is light from a stellar explosion echoing off dust surrounding the star that produces enough energy in a brief flash to illuminate surrounding dust. The star presumably ejected the illuminated dust shells in previous outbursts. Light from the latest outburst travels to the dust and then is reflected to Earth.
The phenomena is similar to that of a nova. A typical nova is a normal star that dumps hydrogen onto a compact white-dwarf companion star. The hydrogen piles up until it spontaneously explodes by nuclear fusion -- like a titanic hydrogen bomb -- exposing a searing stellar core with a temperature of hundreds of thousands of degrees Fahrenheit.
By contrast, V838 Monocerotis did not expel its outer layers. Instead, it grew enormously in size. Its surface temperature dropped to temperatures that were not much hotter than a light bulb. This behavior of ballooning to an immense size, but not losing its outer layers, is very unusual and completely unlike an ordinary nova explosion.
The outburst may represent a transitory stage in a star's evolution that is rarely seen. The star has some similarities to highly unstable aging stars called eruptive variables, which suddenly and unpredictably increase in brightness.
V838 Monocerotis is located about 20,000 light-years away from Earth in the direction of the constellation Monoceros, placing the star at the outer edge of our Milky Way galaxy.
Image credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

Solar Plasma Filaments

Hinode, a collaborative mission of the space agencies of Japan, the United States, United Kingdon and Europe, captured these very dynamic pictures of our sun's chromosphere on Jan. 12, 2007. Taken by Hinode's Solar Optical Telescope, this image of the sun reveals the filamentary nature of the plasma connecting regions of different magnetic polarity. The chromosphere is a thin layer of solar atmosphere sandwiched between the visible surface, photosphere and corona.