Comets are not new celestial bodies. In fact, they were observed by humans in ancient times. The brightest ones stand out among other objects in the sky, as they are unlike any other and possess unique characteristics. One way to identify them is by their appearance as patches of light, often blurry, leaving a trail or a kind of light trail behind them.
You can also read: 4 KEY ASPECTS TO UNDERSTANDING ASTEROIDS
That trail left by comets is precisely what makes them so captivating, shrouding them in magic and mystery. Comets are delicate, small bodies with irregular shapes, formed from a mixture of hard substances and frozen gases. Their main structure consists of a nucleus made of ice and rock. This nucleus is surrounded by a nebulous atmosphere called the coma. If you'd like to learn more about the characteristics of comets , I invite you to read the article.
In 1949, the American astronomer Fred Whipple described the nucleus as containing almost all of the comet's mass, likening it to a "dirty snowball" composed of a mixture of ice and dust. Furthermore, to understand comets better, it's essential to explain that most of the gases ejected to form the coma are fragmented or radical molecules.
The aforementioned molecules are composed of the most common elements in space: carbon, oxygen, nitrogen, and hydrogen. The head of a comet, which of course includes its diffuse coma, can be larger than the planet Jupiter. However, the solid part of most comets has a volume of only a few cubic kilometers. For example, the dust-obscured nucleus of Halley's Comet is approximately 15 by 4 kilometers in size. If you would like to learn more about the origin of these celestial bodies, you can consult our page on the origin of comets.
Orbits and periods of Comets
Comets have orbits that deviate significantly from those predicted by Newton's laws . One reason for this behavior is that escaping gases create a jet propulsion effect, which slightly displaces a comet's nucleus from its trajectory. Furthermore, short-period comets, observed over many orbits, tend to fade over time, as might be expected. If you're interested in learning more about the various laws that govern the universe, you can consult our article on the laws of the universe.
Furthermore, the existence of comet groups demonstrates that cometary nuclei are solid units. However, comet orbits are generally much more elongated than the orbits of planets. At one extreme, they can bring comets close to the Sun, and at the other, they can take them beyond the orbit of Pluto. A peculiar characteristic is that when comets approach the Sun and heat up, their gases evaporate. If you want to learn more about celestial phenomena, you can consult this article on space phenomena.
Once these gases evaporate , scientists observe that they release solid particles, forming what we know as the coma. Interestingly, as the stars move away again, they cool, the gases freeze, and the tail disappears. You might also be interested in reading: 4 Fundamental Theories About the Origin of the Universe Since Antiquity
As explained above, it appears that the tail is activated by the Sun's heat and deactivates again once the comet moves away from the star. Furthermore, with each pass, comets lose material, which is what ultimately leaves only the rocky nucleus. It's worth noting that some asteroids are estimated to be the bare nuclei of comets. If you'd like to learn more about this phenomenon, feel free to read our article on comet speed.
Comet Periods
When we talk about the orbits of comets, it's essential to understand their orbital periods. At Journey to the Cosmos , we explain that comets don't have a single orbital period. Among the various comets, some have short orbital periods, while others have long ones. Some never go beyond Jupiter's orbit, while others travel far enough away that they eventually leave the Solar System and never return. If you want to learn more about the nature of celestial bodies, you can visit our article on shooting stars.
An example of a comet with a short orbital period is Comet Encke , which approaches Earth every three years and three months. However, it can only be seen with a good telescope. On the other hand, Halley's Comet visits us every 76 years, and Comet Rigollet does so much less frequently, every 156 years; however, these are even brighter. If you would like to learn more about how comets have been studied over time, there is a relevant article summarizing comets in the sky.
3 Comets that will soon approach Earth
The Universe holds many surprises and cosmic wonders that we on Earth always want to appreciate. Many of these discoveries pass by unnoticed because we don't know when to look at the sky or because we haven't prepared beforehand for a clear night in a location without light pollution. And although in some cases we won't be able to see them with the naked eye, it's always important to know when these space objects will pass near our planet. For more interesting facts about space, don't miss our article on space curiosities.
For this reason, it's essential to know which luminous rocky bodies, or comets, will be approaching our planet Earth and crossing our skies. And of course, in this article, Journey to the Cosmos mentions three comets you might see. If you want to learn more about comets and their composition, check out our article on the composition of comets.
Comet 46P/Wirtanen
The year 2018 brings with it the approach of an impressive event that could gain some notoriety. This will occur when comet 46P/Wirtanen makes its closest approach to the Sun, possibly making it visible to the naked eye at magnitude 3 in both the Northern and Southern Hemispheres.
This is good news for us, since a magnitude of less than 8,5 is required to be visible with good binoculars and less than 5 to be visible to the naked eye, while on the other hand the availability of small telescopes opens our eyes to many other beautiful celestial bodies and unexpected visitors from the vast Universe.
This comet, called 46P/Wirtanen, will become the Christmas comet of 2018, a magnificent event worthy of being shared with family or on a romantic date. It will make a close approach to Earth and will be the subject of special observation by NASA as it passes by on December 16, 2018, although it will be visible beforehand. However, that date is important because it will reach 8% of the Earth-Sun distance (0,0777 AU), according to their records.
Assasin Comet
This comet is notable for its strikingly vibrant green color, which can be attributed to the emission of diatomic carbon. Comet Asassn, scientifically known as C/2017 O1, reached a magnitude of 8,5, according to the Cometography team . This makes it visible with binoculars. You can also learn more about this phenomenon in our article on the mysteries of space.
What's fantastic about this comet is that it has begun to develop a small dust tail, starting around the end of July. Images taken by astronomical teams confirm that it is growing an increasingly longer dust tail. And although this surprising space visitor is currently being studied, it is estimated that it will make its closest approach to Earth on October 18, 2017.
Comet Asassn will make its closest approach to the Sun (0,72 AU), reaching 72% of the Earth-Sun distance. This will occur just four days after its perihelion, its closest point to the Sun, which will be on October 14th, when it will be 1.51 AU from Earth. The orbit was plotted by the Astronomical Telegram Center CBET 414.
Comet 21P/Giacobini-Zinner
This comet has been studied by various teams of astronomers internationally. NASA describes comet 21P/Giacobini-Zinner as a small comet, with a diameter of approximately 2 kilometers, orbiting the Sun every 6,6 years. Its last closest approach to the Sun, or perihelion, was on February 11, 2012. This indicates that its next passage by our planet will be in 2018. If you are interested in learning more about different types of comets, visit our article on different types of comets.
This comet is expected to reach magnitude 13 during May, when it can be observed in the Northern Hemisphere at dusk, midnight, and in the early morning. However, its resolution could increase to magnitude 11 during June and magnitude 8 during July. It will be during this time that it can be seen with binoculars near the constellation Cygnus. Finally, August 2018 will be the best month for viewing this comet, as it will be visible at magnitude 7 when it passes near the constellation Perseus.
Perhaps you should read: DETAILS ABOUT METEOROIDS AND THE LATEST NEWS
A clear night sky , surrounded by family or loved ones, is the perfect occasion to appreciate the divine creation of the Universe and its beauty. Three upcoming comets offer you the opportunity to make this moment even more special.
