Hubble reveals the Ring Nebula’s true shape

The Ring Nebula's distinctive shape makes it a popular illustration for astronomy books. But new observations by NASA's Hubble Space Telescope of the glowing gas shroud around an old, dying, sun-like star reveal a new twist.

"The nebula is not like a bagel, but rather, it's like a jelly doughnut, because it's filled with material in the middle," said C. Robert O'Dell of Vanderbilt University in Nashville, Tenn. He leads a research team that used Hubble and several ground-based telescopes to obtain the best view yet of the iconic nebula. The images show a more complex structure than astronomers once thought and have allowed them to construct the most precise 3-D model of the nebula.
"With Hubble's detail, we see a completely different shape than what's been thought about historically for this classic nebula," O'Dell said. "The new Hubble observations show the nebula in much clearer detail, and we see things are not as simple as we previously thought."

The Ring Nebula is about 2,000 light-years from Earth and measures roughly 1 light-year across. Located in the constellation Lyra, the nebula is a popular target for amateur astronomers.

Previous observations by several telescopes had detected the gaseous material in the ring's central region. But the new view by Hubble's sharp-eyed Wide Field Camera 3 shows the nebula's structure in more detail. O'Dell's team suggests the ring wraps around a blue, football-shaped structure. Each end of the structure protrudes out of opposite sides of the ring.

The nebula is tilted toward Earth so that astronomers see the ring face-on. In the Hubble image, the blue structure is the glow of helium. Radiation from the white dwarf star, the white dot in the center of the ring, is exciting the helium to glow. The white dwarf is the stellar remnant of a sun-like star that has exhausted its hydrogen fuel and has shed its outer layers of gas to gravitationally collapse to a compact object.

O'Dell's team was surprised at the detailed Hubble views of the dark, irregular knots of dense gas embedded along the inner rim of the ring, which look like spokes in a bicycle wheel. These gaseous tentacles formed when expanding hot gas pushed into cool gas ejected previously by the doomed star. The knots are more resistant to erosion by the wave of ultraviolet light unleashed by the star. The Hubble images have allowed the team to match up the knots with the spikes of light around the bright, main ring, which are a shadow effect. Astronomers have found similar knots in other planetary nebulae.

All of this gas was expelled by the central star about 4,000 years ago. The original star was several times more massive than our sun. After billions of years converting hydrogen to helium in its core, the star began to run out of fuel. It then ballooned in size, becoming a red giant. During this phase, the star shed its outer gaseous layers into space and began to collapse as fusion reactions began to die out. A gusher of ultraviolet light from the dying star energized the gas, making it glow.

The outer rings were formed when faster-moving gas slammed into slower-moving material. The nebula is expanding at more than 43,000 miles an hour, but the center is moving faster than the expansion of the main ring. O'Dell's team measured the nebula's expansion by comparing the new Hubble observations with Hubble studies made in 1998.

The Ring Nebula will continue to expand for another 10,000 years, a short phase in the lifetime of the star. The nebula will become fainter and fainter until it merges with the interstellar medium.

Studying the Ring Nebula's fate will provide insight into the sun's demise in another 6 billion years. The sun is less massive than the Ring Nebula's progenitor star, so it will not have an opulent ending.

"When the sun becomes a white dwarf, it will heat more slowly after it ejects its outer gaseous layers," O'Dell said. "The material will be farther away once it becomes hot enough to illuminate the gas. This larger distance means the sun's nebula will be fainter because it is more extended."

In the analysis, the research team also obtained images from the Large Binocular Telescope at the Mount Graham International Observatory in Arizona and spectroscopic data from the San Pedro Martir Observatory in Baja California, Mexico.

New Telescope Set for Launch May 11 from New Mexico05.10.13

NASA will launch a new telescope designed to observe distant galaxies on a suborbital sounding rocket at 1 a.m. EDT, May 11, from the White Sands Missile Range in New Mexico.

The observations will be conducted using the FORTIS (Far-ultraviolet Off Rowland-circle Telescope for Imaging and Spectroscopy) spectro/telescope developed at the Johns Hopkins University in Baltimore.

Stephan McCandliss, principal investigator for the mission, said, “The goal of FORTIS is to explore the mysteries of escaping of ultraviolet radiation from the dusty confines of galaxies, using a new type of spectro/telescope with more than six times the sensitivity of our previous experiments. FORTIS can acquire spectra from forty-three individual targets simultaneously, and autonomously, within an angular region as large as the diameter of the moon (1/2 degree).”

FORTIS is to fly on a Black Brant IX suborbital sounding rocket to an altitude of about 173 miles, providing approximately 360 seconds of exo-atmospheric observation time for FORTIS. The experiment will land via parachute approximately 50 miles from the launch site where it will be recovered. The total mission time is approximately 900 seconds from launch to landing.

Milky Way Black Hole Snacks on Hot Gas

The Herschel space observatory has made detailed observations of surprisingly hot gas that may be orbiting or falling towards the supermassive black hole lurking at the center of our Milky Way galaxy. Herschel is a European Space Agency mission with important NASA participation.

"The black hole appears to be devouring the gas," said Paul Goldsmith, the U.S. project scientist for Herschel at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This will teach us about how supermassive black holes grow."

Our galaxy's black hole is located in a region known as Sagittarius A* -- or Sgr A* for short -- which is a nearby source of radio waves. The black hole has a mass about four million times that of our sun and lies roughly 26,000 light-years away from our solar system.

Even at that distance, it is a few hundred times closer to us than any other galaxy with an active black hole at its center, making it the ideal natural laboratory to study the environment around these enigmatic objects. At Herschel's far-infrared wavelengths, scientists can peer through the dust in our galaxy and study the turbulent innermost region of the galaxy in great detail.

The biggest surprise was the hot gas in the innermost central region of the galaxy. At least some of it is 1,832 degrees Fahrenheit (around 1,000 degrees Celsius), much hotter than typical interstellar clouds, which are usually only a few tens of degrees above absolute zero, or minus 460 degrees Fahrenheit (minus 273 degrees Celsius).

The team hypothesizes that emissions from strong shocks in highly magnetized gas in the region may be a significant contributor to the high temperatures. Such shocks can be generated in collisions between gas clouds, or in material flowing at high speeds.

Using near-infrared observations, other astronomers have spotted a separate, compact cloud of gas amounting to just a few Earth masses spiralling toward the black hole. Located much closer to the black hole than the reservoir of material studied by Herschel in this work, it may finally be gobbled up later this year.
Spacecraft, including NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the Chandra X-ray Observatory, will be waiting to spot any X-ray burps as the black hole enjoys its feast.

Hubble Sees the Remains of a Star Gone Supernova

These delicate wisps of gas make up an object known as SNR B0519-69.0, or SNR 0519 for short. The thin, blood-red shells are actually the remnants from when an unstable progenitor star exploded violently as a supernova around 600 years ago. There are several types of supernovae, but for SNR 0519 the star that exploded is known to have been a white dwarf star — a Sun-like star in the final stages of its life.

SNR 0519 is located over 150 000 light-years from Earth in the southern constellation of Dorado (The Dolphinfish), a constellation that also contains most of our neighboring galaxy the Large Magellanic Cloud (LMC). Because of this, this region of the sky is full of intriguing and beautiful deep sky objects.

The LMC orbits the Milky Way galaxy as a satellite and is the fourth largest in our group of galaxies, the Local Group. SNR 0519 is not alone in the LMC; the NASA/ESA Hubble Space Telescope also came across a similar bauble a few years ago in SNR B0509-67.5, a supernova of the same type as SNR 0519 with a strikingly similar appearance.

Tis the Season -- for Plasma Changes at Saturn

Researchers working with data from NASA's Cassini spacecraft have discovered one way the bubble of charged particles around Saturn -- known as the magnetosphere -- changes with the planet's seasons. The finding provides an important clue for solving a riddle about the planet's naturally occurring radio signal. The results might also help scientists better understand variations in Earth's magnetosphere and Van Allen radiation belts, which affect a variety of activities at Earth, ranging from space flight safety to satellite and cell phone communications.

The paper, just published in the Journal of Geophysical Research, is led by Tim Kennelly, an undergraduate physics and astronomy major at the University of Iowa, Iowa City, who is working with Cassini's radio and plasma wave science team.

In data collected by Cassini from July 2004 to December 2011, Kennelly and his colleagues examined "flux tubes," structures composed of hot, electrically charged gas called plasma, which funnel charged particles in towards Saturn. Focusing on the tubes when they initially formed and before they had a chance to dissipate under the influence of the magnetosphere, the scientists found that the occurrence of the tubes correlates with radio wave patterns in the northern and southern hemisphere depending upon the season. This seasonal effect is roughly similar to the way Earth's northern lights appear more frequently in the spring and autumn months.

Radio emissions have been used to measure Jupiter's rotation period reliably, and scientists thought it would also help them determine Saturn's rotation period. To their chagrin, however, the pattern has varied over the visits by different spacecraft and even in radio emissions originating in the northern and southern hemispheres. The new results could help scientists hone in on why these signals vary the way they do.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the mission for the agency's Science Mission Directorate in Washington. The radio and plasma wave science team is based at the University of Iowa, Iowa City, where the instrument was built. JPL is a division of the California Institute of Technology, Pasadena.