While this starry vista seems tranquil, the events that shaped the Pencil Nebula were nothing but quiet. Stars are born and stars die and when they do, they create amazing stellar landscapes. A star, perhaps a massive one, exploded to sculpt this beautiful starry scene that resembles an exotic bird head or a strangely shaped ray of light.
Explore the fine filaments, bright knots, and nebulous remnants of the Pencil Nebula; just a tiny piece of the Vela Supernova remnant. What shapes or stories do you see? Leave a note in the comments below.
The oddly shaped nebula, also known as NGC 2736, makes up the bright edge of this piece of the remnant. The wispy red filaments look much like a witch’s broom. The new image from the Wide Field Imager on the MPG/ESO 2.2-meter telescope at ESO’s La Silla Observatory in Chile. These glowing wisps of gas and dust are the result of the cataclysmic death of a star more than 11,000 years ago.
A supernova is a violent end to a star’s life. The blast is the result of either the death of a high-mass star or explosion of a white dwarf in a close double star system. The Vela supernova remnant is a vast expanding shell of gas. And as this shell expands it slams into the calm gas and dust surrounding it. This shockwave compresses the gas and causes the nebulae begin to glow. Those little filaments show the many shokwaves moving through the area. At first, as gas molecules are squished together, these regions are heated to millions of degrees but quickly cool as the shockwave passes. Enough lingering heat remains for observers on Earth to view the strange structures created from the shockwave’s interaction with the calm surrounding cloud.
Different colors within the nebula allow astronomers to map temperatures within the cloud of gas. Some regions glow hotly and are dominated by ionized oxygen atoms. These areas show with a blue light. Redder areas are cooler ionized hydrogen clouds.
The Pencil Nebula was discovered by British astronomer John Herschel in 1835. He described it as “an extraordinary long narrow ray of excessively feeble light.” The nebula is also called Herschel’s Ray. The ray of light is about three-quarters of a light year across. The nebula is rolling through the surrounding nebula at about 650,000 kilometers per hour (about 404,000 miles per hour). The Pencil Nebula is close too, only about 800 light-years from Earth toward the constellation of Vela, the sails of Jason’s mythical ship the Argo. This means that over the span of a human life, the starry face of the Pencil Nebula change as it moves against the background of stars.
An expanding translucent bubble is all that remains of a star in this combinded image from NASA’s Chandra X-ray Observatory and other observatories.
Explore the bumps, ribbons and sheets throughout this image of SN 1006. What stories or images do you see? Leave a note in the comments below.
In the spring of 1006, night-time observers in China, Japan, Europe, the Arab world and the Americas documented a new light in the sky. To this day the supernova of 1006 is the brightest stellar event in recorded history. Reports from China and Arab astronomers report the star was more than twice as big as Venus and objects cast shadows. While this new “guest star” glowed for months, ancient observers had no way of knowing that a star had exploded. This was a different type of supernova. Instead of a massive star collapsing and exploding, a white dwarf star captured mass from a companion star. When enough material lands on the surface of a white dwarf it becomes unstable and explodes. White dwarf stars are the burned out cores of stars that were once like our Sun. After billions of years fusing hydrogen atoms in the core, the star runs out of fuel. When this occurs, the star puffs off its outer layers and all that remains is the white-hot core. In this case, the white dwarf probably orbited a much larger red giant star.
SN 1006 is found about 7,000 light-years from Earth toward the constellation Lupus, the Wolf. The remnant of the supernova of 1006 was not found until 1965 when astronomers using found that a previously known radio source was surrounded by a large shell. We now know that the shell extends for about 65 light-years. The shell is so large that the Hubble Space Telescope can image only parts of the supernova remnant.
Explore the red and churning bubble in this image. What stories or images do you see? Leave a comment below.
The star that created Puppis A exploded about 3,700 years ago. Perhaps humans on Earth saw this new bright star in the sky. If they did, they left no record of it. Supernovae, like the Crab Nebula, form when stars many times more massive than our Sun reach the end of their life. These huge stars burn through their hydrogen fuel within just a few million years. When the fuel runs out, the star expands. But gravity pulls the star back together. This heats the star to a point where a runaway fusion reaction occurs. It becomes unstable and the star explodes. So much energy in heat and light is released in this explosion that for short periods of time, the star can outshine an entire galaxy. All that remains is a dense and tiny neutron star surrounded by an expanding cloud of gas and dust. Our Sun is not heavy enough to end this way. It will reach the end of its life in about 4 billion years and become a planetary nebula.
Explore the red dusty cloud. If we hopped in our starship and zipped off at the speed of light, it would take about 100 years to cross this gas cloud. The expanding shockwave from the explosion slams into the quiet dust surrounding the star and heats up the dust enough to cause it to glow. Ultraviolet radiation from the hot neutron star also excites atoms within the cloud causing it to glow. The green colored gas in the image is cool dust left over from a much earlier supernova explosion. This explosion occurred about 12,000 years ago and was even closer to Earth.
Puppis A is one of the brightest X-ray objects in the night sky. It is about 6,500 light-years from Earth toward the large constellation of Puppis. Puppis is the poop deck of the mythical ship used by Jason and the Argonauts. It was part of a larger constellation known as Argo Navis. Nicolas Louis de Lacaille broke the constellation into three parts in 1752; Puppis, Carina, the keel, and Vela, the sails.
Supernovae explode with an energy that can outshine an entire galaxy. But just as quickly the star fades from view leaving an expanding bubble of star guts and in the case of Cassiopeia A, a light echo.
About 11,000 years ago, toward the constellation Cassiopeia, the Queen, a massive supergiant star exploded in the Milky Way, our home galaxy. Supernova happen at the end of these giant stars’ lives. Stars about ten times more massive than our Sun burn through their hydrogen fuel quickly, within only tens of millions of years. They burn super hot and when the fuel runs out they collapse. Collapsing stars become even hotter and as the outer layers of the star heat up a runaway nuclear reaction can occur. The star explodes. The light from the explosion can be brighter than the entire galaxy. The explosion creates and scatters elements necessary for life on Earth, such as carbon and iron. It also spreads heavier elements such as gold, silver and uranium.
Zoom into the bright yellow cloud of dust. This is the bubble of material blown away from the star. As the edge of the bubble moves through interstellar space it heats up gas. The shockwave slams into the calm space at about 18,000 kilometers per second (11,000 miles per second) or about six percent the speed of light. In 11,000 years since the explosion, the expanding ball has expanded about 21 light-years.
Light travels much faster than the expanding bubble of gas and dust left over from the star. WISE, with its infrared eyes, detected infrared echoes of the brilliant flash as the light and heat ripple outward through surrounding star clouds. Look to the upper right for a curtain of orange in the cooler, greenish nebula. These orange echoes are remnants of heat generated when light from the explosion reached this part of the nebula.
Light from this explosion, traveling at more than six trillion miles per year, finally reached Earth in about 1667 AD. We have no record of it. European astronomers didn’t report it, Chinese astronomers didn’t record it. Scientists think that thick dust surrounding the star blocked most of the light, making it a dim supernova. Astronomers discovered the remnant in 1947. When they used new radio telescopes to scan the sky, Cas A was the brightest source they could see.
Supernova remnant Cassiopeia A glows with many colors in this composite image from NASA’s Great Observatories.
Zoom into the jumbled strands of colors. What stories or pictures do you see? Leave a note below.
Cassiopeia A, or Cas A, is the remnant of a star that exploded. Supernovae are the ultimate end of stars that are about ten times more massive than our Sun. When stars this big run out of hydrogen fuel, they quickly expand. Their great gravity however pulls the material back in toward the star where it heats up very fast creating a runaway nuclear fusion reaction. The star becomes unstable and explodes.
As you explore the image, look for the different colors offered by images of each observatory. Astronomers used to think that the explosion scattered material evenly around the star. But knots and filaments show that material was ejected at different times and speeds. Spitzer imagery shows reddish warm dust in the outer shell of the supernova with a comfortable temperature of about 80 degrees Fahrenheit (10 degrees Celsius). Hubble Space Telescope imagery shows a fine yellow filament structure of warmer gases. Chandra imagery shows superhot gas in blues and greens. The hot gas was created when material ejected at high speed during the explosion slammed into the calm gas and dust surrounding the star. Look for the turquoise dot near the center of the image. This may be the neutron star created during the supernova. A neutron star is the hot and super-dense core of an exploded star. Some scientists believe that a black hole resides at the center of the remnant.
Cas A lies about 11,000 light-years from the Earth toward the constellation Cassiopeia. Astronomers believe first light from the supernova reached Earth about 300 years ago. But no one on Earth seems to have seen it. Historians think that John Flamsteed may have noticed the star in 1680. Astronomers theorize that the massive star had ejected a dense bubble of dust that blocked light from the explosion. Scientists discovered the supernova in the 1940s because it is one of the brightest radio sources in the sky. No supernovae have been visible in the Milky Way since.