There are many differences between galaxies and nebulae, but perhaps the most notable is the central core of a galaxy, the point around which all matter contained within its boundaries rotates.
This article looks at the differences between nebulae and galaxies in terms of composition, size, and comparisons to other celestial bodies.
Nebula vs Galaxy (Explained)
What is a Nebula?
A nebula is a large, diffuse cloud of dust and ionized gases, along with basic elements like hydrogen. Gravity slowly pulls these clouds together into dense masses.
Nebulae can be created by the collapse of a dying star, or the explosion of a nova or supernova.
However, they can also develop over time without explosions, as gas and dust come together.
Nebulae are often called stellar nurseries.
The gas draws together into denser and denser sections, and eventually new stars are born within those clouds.
Is a Nebula Bigger Than A Solar System?
Nebulae are diffuse clouds, often several hundred light-years across.
The size varies across nebulae, but planetary nebulae are often smaller than others, and the smallest may well be similar in size to a solar system.
On average, nebulae are larger than a solar system, but there are possible exceptions out there.
How Do Nebulae Compare to Stars and Planets?
In terms of size, even a small nebula covers much more area than a star or a planet.
In point of fact, new stars are often formed by the condensing of large nebulae into a smaller, more compact mass until ignition of the fusion process occurs.
Most nebulae have to be huge, in order to condense enough material to live up to their nickname of ‘stellar nurseries’.
It’s been theorized, based on the observed densties of nebulae, that a nebula the size of a planet – at standard nebula density rather than star-formation densities – would weigh only a few kilograms.
Are There Different Types of Nebulae?
There are debates as to how nebulae are classified, with between 2 and 5 different classifications suggested.
The most basic classifications are dark and bright nebulae.
These classifications are determined by whether or not they show a certain level of luminosity.
The most common nebulae classifcations are the following:
Planetary nebulae: Usually formed by the collapse of a star at the end of its life cycle. They’re often circular in shape, illuminated by the remnants of the star at the center.
Emission nebulae: High temperature gases excite particles, which then give off radiation and cause the nebula to glow. They’re usually highly luminous.
Reflection nebulae: These nebulae reflect the light of nearby celestial systems, and are usually areas of star formation.
Dark nebulae: Blocks the light from nearby celestial formations, creating a darker patch in the sky.
Supernova Remnants: These can be classified as a subsection of planetary nebulae, created specifically from the explosion of a supernova. They are usually illuminated by remnants of their star.
How Big is a Nebula?
The size of a nebula varies wildly, based on how they were formed, age, amount of available material, activity, and other factors.
Some nebulae are tiny, barely a light year across.
These are usually planetary nebula, created by the collapse of the central star of a solar system.
The largest identified nebula is the Tarantula Nebula, which is thought to be 1,800 light-years across.
It’s also one of the most active star-formation centers recorded.
What is a Galaxy?
Galaxies are generally formed around a supermassive black hole.
The supermassive black hole creates a gravitational center that draws the dust clouds, stars and stellar formations of nearby areas into an orbital position around the central mass.
Galaxies can also be created by collisions between stellar formations.
Dense clouds of matter come together and develop a gravitational center.
Galaxies generally contain billions and billions of stars, and solar systems, as well as interstellar dust, dark matter and gases.
Is A Galaxy Bigger than a Solar System?
Galaxies are the second largest celestial formation in existence. Only the universe is larger.
Most galaxies contain hundreds or thousands of solar systems.
Are There Different Types of Galaxies?
There are three major classifications of galaxies, determined by the shape.
Elliptical: Older galaxies with older stars and very little dust, gas and very little new star formation occuring. They maintain a disk-like shape, circular or oval.
Spiral: They can be divided into barred and regular spirals, and they show distinct arms showing the rotation of the galaxy. These galaxies are usually newer and more active, with plenty of star formation.
Irregular: Irregular galaxies are the oldest classification of galaxies, formed in the earliest ages of the universe. They have very little dust or stars, and come in a variety of shapes.
How Big is a Galaxy?
Galaxies come in a range of sizes.
Our galaxy is thought to be roughly 100,000 light-years across, which is more or less average for a galaxy of its type.
Most galaxies are calculated to measure between 3,000 and 300,000 light-years.
The size depends on the amount of material available and the strength of the gravitational core.
Is a Nebula Bigger Than A Galaxy?
The average size of a galaxy is bigger than the average size of nebulae.
In fact, many galaxies contain nebulae of all types, and possess several times the overall mass.
However, not all galaxies are larger than all nebulae.
There’s a great variety in size among both celestial formations, making an exact comparison dependent on which two bodies you compare.
Are Nebulae and Galaxies Larger than Globular Clusters?
Globular clusters are collections of stars, often found in and around galaxies.
In comparison, globular clusters are always smaller than galaxies, though they may possess a similar shape.
On average, globular clusters have less than a thousandth of the mass and size of a galaxy.
When compared to a globular cluster, nebulae tend to fall into two groups.
Planetary nebulae are almost always smaller than globular clusters.
The other four classifications of nebulae vary more in size, and may be smaller, larger, or the same size as a globular cluster, depending on the amount of material present in each.
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