Comets are some of the fastest matter in our solar system. But how fast do comets travel?
Comets travel at various speeds depending on where they are in their orbit. When close to the Sun they move much faster than when distant from it. Continue reading to discover more about how fast comets travel.
Not all comets are equal. For instance, Halley’s Comet travels at a leisurely speed of approximately 35,000 mph (56,327 km).
Regardless of how fast they are traveling, they are always an awe-inspiring sight.
With this in mind, this article will explore everything you need to know about how fast comets travel.
Let’s get started.
Where do Comets Originate?
There are two sources of material from which comets are made. The first area is from the Kuiper Belt. The Kuiper Belt is a donut-shaped ring of icy objects extending from Neptune’s orbit to about 50 AU from the Sun. It lies in the same plane as the other objects in the solar system.
The second source of comets is the Oort Cloud. The Oort Cloud is much further out than Pluto’s orbit (think in the range of 10s of thousands of AU to about 100 thousand AU). Unlike the Kuiper Belt, the Oort Cloud occupies a sphere around the solar system.
It’s important to remember that these bodies of icy material are the leftovers from the solar system’s formation.
So you might ask why comets leave these regions and begin orbiting closer to the Sun. It’s a good question. We believe that collisions between objects in these regions result in small parts breaking off larger bodies. These smaller objects can then be launched into new orbits by gravitational perturbations. In the case of the Kuiper Belt, Neptune provides the trigger. This also explains why comets are often inclined to that of the solar system.
Scientists have identified two populations of comets: short-period comets and intermediate- and long-period comets. The short-period comets are thought to be derived from the Kuiper Belt. They have an orbit period of fewer than 20 years.
The intermediate- and long-period comets are derived from the Oort Cloud. Intermediate-period comets have a period of between 20 and 200 years. While long-period comets can have an orbit period of more than 70,000 years. Halley’s Comet is an example of an intermediate-period comet.
The Speed Of Comets
As mentioned, comets are small celestial bodies that travel around the Sun. They are composed of ice and dust and are said to be leftovers from the solar system’s formation.
When they are close to the Sun, comets are usually very bright and can even be seen by the naked eye.
Comets typically travel at speeds of around 100,000 miles per hour (160,934.4 km) or 27 miles per second (43.452288 km).
While we have detailed how fast they can travel, we should mention how slow they travel. Like all comets, Halley’s Comet’s speed is dictated by their position in their orbit. Closest to the Sun they travel at their highest speed. Conversely, they are slow when they are far from the Sun. At aphelion (i.e. when farthest from the Sun), Halley’s Comet travels at approximately 2000 miles per hour. This compares to 123,000 miles per hour (198,000 km/hr, Halley’s Comet) when closest to the Sun (at perihelion).
Why Do Comets Travel So Fast?
A comet’s speed is determined by its elliptical orbit. Comets usually have highly elliptical orbits. However, comets will always return to the Sun – even if they spend thousands of years in the outer Solar System.
The tightly elliptical orbits are the reason why comets travel so fast. The Sun’s gravity helps to propel the comets to move faster when they are close but slow down when they are far away.
Therefore, the reason why comets travel so fast is because of the Sun’s gravity.
The relative speed of a comet is a function of where it is located in its orbit. They move faster when close to the Sun and slowest when further away. The orbit speed is described in Kepler’s Second Law.
What Are Comets Made Of?
Comets have been described as ‘dirty snowballs’. They are composed of ices and dust. Common materials existing as ice are carbon dioxide, carbon monoxide, water, methane and ammonia. As comets contain ice their origin is thought to be from the outer part of the solar system.
Comets have low densities. This is because they are not solid and contain plenty of space between clumps of material. In essence, they are rubble piles held together by gravity.
A comet comprises a nucleus, hydrogen envelope, coma, plasma tails, and dust.
As mentioned earlier, the nucleus of a comet is a loosely bound collection of ice and rock (and dust). Far from the Sun, this is the only part of a comet present. However as it gets closer to the Sun, the parts of the comet exposed to the Sun begin to heat.
Due to the heating sublimation begins. Sublimation is the process of turning ice directly into a gas. This process releases gas and dust into space. From this, several features result.
The nucleus of a comet is typically approximately 6 miles (10 km) across or less.
Coma
As sublimation progresses, it forms a fuzzy luminous ball around the nucleus. This is called a coma and it forms a sphere about 625,000 miles (100 million km) in diameter.
Tails
As previously stated comets are comprised of ice and dust. The two components give rise to two distinct tails. In most circumstances, they point in different directions due to the forces that act on them.
The gases released form electrically charged particles called ions. Being electrically charged these particles are influenced by the electrically charged solar wind. The result is a straight blue tail pointing away from the Sun. The blue color results from emissions from carbon-containing molecules.
The solar wind does not affect the dust released as the particles are not charged. They are affected by what is called the radiation pressure. This is a weak force from light hitting the small particles. While this tail also points away from the Sun, it is often curved.
That said, you should remember that most comets are too small or faint to be seen with the naked eye. Therefore, you could need a telescope.
As comets travel, they leave a trail of debris. This material is what causes meteor showers. Meteor showers occur when the frequency of shooting stars increases. For example, the Perseid meteor showers occur each year between August 9th and 13th when the Earth travels through the orbit of the Comet Swift-Tuttle comet.
Hydrogen Envelope
As water ice melts, it releases water. The water molecule then breaks apart. The hydrogen absorbs radiation from the Sun which excites it. When it returns to its unexcited state ultraviolet light is released.
Neither our eyes nor Earth-based telescopes can detect this light. This is because our eyes can not detect it and the atmosphere absorbs the ultraviolet light. However, space-based telescopes have observed the hydrogen envelope.
The hydrogen envelope forms a sphere of up to 6.2 million miles (10 million kilometers) in diameter. As its name suggests, it is made up of hydrogen atoms.
Like the coma, the hydrogen envelope becomes larger as the comet approaches the sun.
Final Thoughts
Don’t blink or you may just miss a comet!
Comets can travel up to 1 million miles per hour (1,609,344 km/hr) making them one of the fastest celestial materials in the solar system.
In addition to their immense speed, they are incredibly beautiful. Therefore, keep your eyes peeled on a clear night to see if you can spot one.
The closer a comet is to the Sun, the clearer it becomes to the naked eye. The Sun’s sunlight is reflected from the comet’s tail.
Hi, my name is Jason Anderson, and I am a Physics Professor. Ever since I was a kid, I’ve been fascinated with space, the universe, the moon, you name it. I spent hours and hours at the planetarium close to my hometown, wondering what else could be out in the universe.
Since then, I’ve been an avid stargazer and astronomer, and love nothing more than spending my time charting stars, observing planets, and finding constellations.
This is why I decided to start Telescope Guru. I only wish to share this fun pastime with the world. With this site, I hope to answer all of your questions relating to astronomy, telescopes, and stargazing.