How many nebula

As these clumps get larger, their gravity increases. Gravity continues to pull in matter from the nebula until one or more of the clumps reach critical mass. The clumps are forming protostars. As gravity squeezes even tighter, the core temperature eventually reaches 18 million degrees. At this point, nuclear fusion begins and a star is born. The solar wind from the star will eventually blow away all of the excess dust and gas. Sometimes other smaller clumps of matter around the star may form planets.

This is the beginning of a new solar system. Several nebulae have been found to be stellar nurseries. The Eagle Nebula, and the Orion Nebula are both sites of active star formation. There are a few nebulae that can be seen with the naked eye and many more that can be detected with a good pair of binoculars. A telescope is required to bring our fine details. Unfortunately, the human eye is not sensitive enough to bring out the rich colors of most nebulae.

It is the photograph that does the most justice to these incredible objects. Until recently, time exposures on film were the best way to bring a nebula's true colors. Today, digital photography has simplified the process. New tools like the Hubble space telescope are giving us views of nebulae that have never been seen before.

Areas of active star formation have been identified in many galaxies that were once thought to be inert. Perhaps the most well known nebulae is the Orion Nebula, also known as M It is one of the very few that can be seen with the naked eye. It is a bright emission nebula over 30 light-years in diameter.

The nebula is illuminated by a group of stars at its center known as the trapezium. Another popular favorite is the Lagoon Nebula, M8. It is much larger than the Orion Nebula, reaching over light-years across the heavens. The Trifid Nebula, M20, is one of the most colorful.

This reflection nebula contains a combination of elements that render it in rich hues of red, blue, and pink. Dark lanes of dust divide it into three distinct parts, giving rise to its name. One of the most famous planetary nebulae is the Ring Nebula, M This is a beautiful object that resembles a circular rainbow around a small central star.

Another popular planetary nebula is the Dumbbell Nebula, M Its unmistakable bow tie shape gives it its name.

The Crab Nebula, M1, is probably the best known supernova remnant. Some nebulae more than one nebula come from the gas and dust thrown out by the explosion of a dying star, such as a supernova. Other nebulae are regions where new stars are beginning to form. For this reason, some nebulae are called "star nurseries. These towers of cosmic dust and gas make up part of the Eagle Nebula.

These so-called Pillars of Creation are part of an active star-forming region within the nebula. In this image of the Carina Nebula, you can spot tiny yellow and white dots inside pink dust clouds. Those tiny dots are newly-formed stars! Nebulae are made of dust and gases—mostly hydrogen and helium. Hustak, L. Frattare, M. Robberto and M. Stars are born in clouds of gas and dust. One such stellar nursery is the Orion Nebula , an enormous cloud of gas and dust many light-years across.

Turbulence from deep within these clouds creates high density regions called knots. These knots contain sufficient mass that the gas and dust can begin to collapse from gravitational attraction. As it collapses, pressure from gravity causes the material at the center to heat up, creating a protostar.

One day, this core becomes hot enough to ignite fusion and a star is born. Not all of the material in the collapsing cloud ends up as part of a star — the remaining dust can become planets, asteroids or comets … or it may remain as dust.

Scientists running three-dimensional computer models of star formation predict that the spinning clouds of collapsing gas and dust may break up into two or three distinct blobs. This would explain why the majority the stars in the Milky Way are paired or in groups of multiple stars. Astrophysicists have used detailed observations and computer simulations to understand the lifecycles of stars, their chemistry, the nuclear processes within them and the nature of the gas and dust — called the interstellar medium or ISM — out of which stars form.

Hubble probes the intricate complexity of these environments, and it has unveiled stars and planetary systems in the making. The chemical makeup of stars, revealed through spectroscopy , depends on the material in which they originate.

In the early universe, stars were formed from matter that lacked most elements except for hydrogen and helium. The other chemical elements have been and still are being created in the interior of stars through nuclear fusion processes. That new material is eventually recycled into subsequent generations of stars and planets.

Most stars form in multiple star systems, though this formation process is not completely understood. The groupings of stars that form together can vary from a few stars to many hundreds or thousands. The stars in each cluster have a variety of masses. The most massive stars are rare, while the least massive stars are the most numerous. Hubble has probed star clusters of all sizes and uses spectroscopy to determine the detailed chemistry in star cluster members.

By taking precise observations of star cluster members, scientists using Hubble can determine their luminosities intrinsic brightnesses and temperatures. This helps refine our understanding of star formation, stellar evolution and the physics of the theoretical models used to explain these phenomena.