Neutron stars are created when a massive star runs out of fuel and collapses. As the star collapses, the density becomes so immense that protons and electrons are squeezed tightly together to form neutrons. The end result is a star only 20 km across but weighing 1 1/2 times more than our sun and made up mostly of neutrons.
When a star explodes, it leaves behind a debris field of stellar material and high-energy particles known as a supernova remnant. Astronomers use Chandra to study these remnants that can produce intense X-ray radiation for thousands of years. Supernova remnants are responsible for seeding cloud that formed our Sun, planets, and ultimately us with elements like nitrogen and oxygen.
Long before astronomers found evidence that black holes existed, these exotic objects have captured imaginations. In the 21st century, scientists not only have proof that black holes are real, they continue to make startling discoveries both about individual black holes examples and about their populations across the Universe.
Remember the line from the children's saying that goes: "Starlight, star bright, first star I see tonight"? Looking at the light from stars is exactly how astronomers can learn about them.
Supernovas are the remnants of catastrophic explosions, and they are among the favorite targets of scientists who use Chandra, for good reason too. Supernovas and their remnants have proven to be extremely important in understanding topics ranging from the birth of our Solar System to the history and composition of the Universe itself.
In 3C321, a jet from a black hole in one of the galaxies is pummeling its neighbor galaxy, the first time this type of galactic violence has ever been seen. The jet could bring big trouble for any planets in its path, but could also trigger a burst of star formation in its wake.
X-ray telescopes like Chandra are not like the telescopes you find in backyards or at the local observatory. In addition to being above the Earth's atmosphere, they need to have special mirrors to detect the X-rays that pass through most objects.
Clusters of galaxies are the largest structures in the Universe that are held together by gravity. Because of their immense size and mass, galaxy clusters are extremely useful as tools to probe a variety of questions about the Universe as a whole as well as properties of the clusters themselves.
How the Chandra X-ray Observatory fits into the modern astronomer's toolkit. Chandra is one of NASA's "Great Observatories." The Great Observatories were four missions selected by NASA to explore different types of radiation and really tackle the biggest questions in astronomy.
Like the Milky Way, Sombrero is a spiral galaxy. However, we see Sombrero edge-on from our vantage point from Earth, rather than the face-down perspective that is more familiar.
NASA's Chandra X-ray Observatory, in orbit since 1999, studies the high-energy Universe, where black holes, exploding stars, and mysterious matter hold sway.
Of the estimated three hundred billion stars in our galaxy, Eta Carinae may well be the biggest and brightest of them all. Weighing in at 150 times the mass of our Sun, it is five million times as luminous!
The star that dominates our daytime sky and provides the heat and light to support life on Earth is, of course, the Sun. In astronomical terms it is very close, 150 million kilometers (93 million miles), so we can study its properties in great detail. Light from the Sun takes just over eight minutes to reach the Earth. For comparison, light from the next nearest star takes four years to reach us.
Cassiopeia A is the 300-year-old remnant created by the supernova explosion of a massive star. Each Great Observatory image highlights different characteristics of the remnant.
Four hundred years ago, the famous astronomer Johannes Kepler (best known as the discoverer of the laws of planetary motion), was startled by the sudden appearance of a "nova" of "new star" in the western sky, rivaling the brilliance of the nearby planets. Although the nova was new to the night sky, the event was actually the death of an old star, now called a supernova.
The Large Magellanic Cloud, known as the LMC, is a nearby satellite galaxy of our own Milky Way. At a distance of around 160,000 light-years, the LMC is the third closest galaxy to us. But the LMC is more than just a nice little sidekick.
![Chapter 6: Kepler\](http://img.youtube.com/vi/sEGRmToykSY/2.jpg "Chapter 6: Kepler\")
