Expelled outer layers of white dwarf glowing brightly in the infrared
Space news (astrophysics: planetary nebula; Helix Nebula) – 650 light-years from Earth toward the constellation Aquarius –
This composite image shows a visually stunning planetary nebula labeled “The Eye of God” more serious observers call the Helix Nebula (NGC 7293). Planetary nebula are the remains of a dying star much like our own Sol, only 5 billion years in the future. At this time the Sun will run out of hydrogen to use as its fuel source for the fusion process and will start using helium to create heavier carbon, nitrogen, and oxygen. Once it runs out of helium to fuse, it will die and expel its outer gas layers, leaving a tiny, hot core called a white dwarf. An Earth-sized core so dense a teaspoon full would weigh more than a few black rhinos.
First discovered in the 18th century, planetary nebula like the Helix Nebula emit across a similar, broad spectrum from ultraviolet to infrared. The image shown at the top uses a combination of ultraviolet radiation collected by NASA’s Galaxy Evolution Explorer ((GALEX in blue(0.15 to 2.3 microns)) and infrared light detected by their Spitzer Space Telescope ((red(8 to 24 microns) and green(3.6 to 4.5 microns)) and Wide-field Infrared Survey Explorer ((WISE in red(3.4 to 4.5 microns)) showing the subtle differences observed in the different wavelengths of light emitted by ghostly celestial objects like NGC 7293 and NGC 6369 (The Little Ghost).
Astronomers have studied planetary nebulae like the Helix Nebula and M2-9 (Wings of a Butterfly Nebula) as much as any recorded during the human journey to the beginning of space and time. The remnant of a rapidly evolving star near the end of its lifespan, the white dwarf star is a tiny, barely perceptible point of light at the center of the nebula in this composite image. Thousands of planetary nebula have been detected within a distance of about 100 million light-years of Earth and astronomers estimate about 10,000 exist in the Milky Way. Making planetary nebula a relatively common celestial mystery observed as we trace our roots to their beginning.
In the embers of once vibrant white dwarf stars in the central bulge of the galaxy
Space news (December 08, 2015) – Looking through a cosmic keyhole 26,000 light-years away in Sagittarius –
Astronomers trying to understand the formation and evolution of the Milky Way by studying the first stars to be born in the galaxy have a problem. The stars within the central bulge of the galaxy formed first according to stellar theory. Unfortunately, the light from these suns is blocked by massive clouds of gas and dust, which makes studying their role in the formation and evolution of the Milky Way difficult.
In order to view the central bulge of the galaxy, astronomers looked through a small keyhole in the sky, called the Sagittarius Window. Making it possible to study the formation and evolution of the Milky Way and galaxies as a whole by comparison. A view giving us a look into the very heart of the galaxy and the blueprints nature uses to construct these island universes.
Current astronomical theory believes the central bulge of the Milky Way grew first, followed by the relatively quick birth of the stars making up the rest of the galaxy. Peering deep into the heart of the central bulge, astronomers have discovered a family of 70 ancient white dwarf stars, they believe are the smoldering remnants of once-vibrant suns that inhabited the core long ago. Ancient stars scientists are studying to uncover clues to the processes that formed the Milky Way and by relation the family of galaxies in the cosmos. Marking the deepest, most detailed archeological study of the central bulge of the Milky Way and by extension its formation and evolution.
These ancient white dwarf stars hold the keys to opening the door to better understanding the history of the Milky Way. To gaining knowledge and facts concerning 12 billion-year-old suns that existed when the galaxy was young. Knowledge and facts giving astronomers clues to the early years and evolution of the Milky Way and the billions of island universes in the cosmos.
“It is important to observe the Milky Way’s bulge because it is the only bulge we can study in detail,” explained Annalisa Calamida of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, the science paper’s lead author. “You can see bulges in distant galaxies, but you cannot resolve the very faint stars, such as the white dwarfs. The Milky Way’s bulge includes almost a quarter of the galaxy’s stellar mass. Characterizing the properties of the bulge stars can then provide important information to understanding the formation of the entire Milky Way galaxy and that of similar, more distant galaxies.”
“The Hubble survey also found slightly more low-mass stars in the bulge, compared to those in the galaxy’s disk population. This result suggests that the environment in the bulge may have been different than the one in the disk, resulting in a different star-formation mechanism,” Calamida said.
Astronomers have only looked at about 70 of the hottest white dwarfs Hubble can pick out of at least 70 thousand stars in the small area of the bulge of the Milky Way they looked at. White dwarf stars detected by making extremely precise measurements of the motion of over 240,000 stars they detected over a decade of viewing as part of the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Precise measurements astronomers used to determine which stars are disk stars or suns inhabiting the bulge of our galaxy. Stars that inhabit the bulge move at a different rate than suns in the disk of the galaxy as compared to our Sun. Extremely hot white dwarfs are also slightly bluer relative to stars like our own sun and they become fainter and cooler as they age. Facts that allowed Hubble’s Advanced Camera for Surveys to pick out 70 of the brightest white dwarf stars inhabiting the bulge of the Milky Way.
“Comparing the positions of the stars from now and 10 years ago we were able to measure accurate motions of the stars,” said Kailash Sahu of STScI, and the study’s leader. “The motions allowed us to tell if they were disk stars, bulge stars, or halo stars.”
“These 70 white dwarfs represent the peak of the iceberg,” Sahu said. “We estimate that the total number of white dwarfs is about 100,000 in this tiny Hubble view of the bulge. Future telescopes such as NASA’s James Webb Space Telescope will allow us to count almost all of the stars in the bulge down to the faintest ones, which today’s telescopes, even Hubble, cannot see.”
The team’s going back to work
This team of intrepid astronomers and scientists now plan to increase the sample size of the white dwarfs currently being studied. This will be done by analyzing additional parts of the SWEEPS field of study, which they hope to use to get more precise measurements of the exact age of the bulge of the Milky Way. They’ll also take a look at the possibility the star formation processes used to create the bulge billions of years ago, could be slightly different than current star formation processes at work in the younger disk of the galaxy.
You can learn more about the Hubble Space Telescope here.
Twin iridescent jets of gas stream outward from a binary planetary nebula at over 1 million kilometers (621,400 miles) an hour.
Space news (September 24, 2015) –
First recorded flying across the constellation Ophiuchus – about 2,100 light-years from Earth – by Rudolph Minkowski in 1947, the Twin Jet Nebula (PN M2-9), or Wings of a Butterfly Nebula, is a remarkably complex and stunningly beautiful 1,200-year-old bipolar planetary nebula.
A bipolar nebulacomposed of an average star between 1 to 1.4 solar masses nearing the end of its life cycle and a smaller white dwarf between 0.6 to 1.0 solar masses that orbit a common center of mass. The Twin Jet Nebula gets its name from the shape of its two lobes, which look like butterfly wings to many viewers.
Astrophysicists think the shape of the wings (lobes) is mainly due to the unusual motion of the larger star and white dwarf around their common center of mass. Orbiting each other in around 100 years, the smaller white dwarf is thought to have stripped gas away from its larger companion star, which then formed an expanding ring of material around the starsfar too small to be seen by Hubble.
This disk of material was then stretched into the shape of two lobes resembling two butterfly wings, rather than a uniform sphere, due to the unusual motion of the two stars around their center of mass. The faint patches of blue within the wings, starting near the binary star system and extending outward horizontally, are twin jets of gas streaming outward at over 1 million kilometers an hour.These jets slowly change their orientation, precessing across the lobes (wings) as the two stars orbit each other.
Astrophysicists are now taking a closer look at the Twin Jet Nebula, and other bipolar nebulae, to try to determine if such systems always contain two stars orbiting a common center of mass. Currently, astronomers are discussing this possibility, and other scenarios possibly leading to the birth and growth of similar celestial objects and other phenomena.
Two astronomers working with NASA’s Hubble Space Telescope and the ESO’s New Technology Telescope also recently conducted a study of 130 planetary nebulae. Dr. Brian Rees and Dr. Albert Zijlstra of the University of Manchester in the United Kingdom found the long axis of many bipolar planetary nebulae studied all line up along the plane of the Milky Way. This alignment could have something to do with the magnetic field of the bulge at the center of our galaxy they think. You can read the abstract here.