November is traditionally considered not the best month for astronomy observations. And it’s not hard to understand why. The sky is often overcast, and the cold nights don’t make it comfortable for observers either. But this does not mean that nothing interesting happens in November in the sky. One of the main events of the month is the Leonid Meteor Shower. Yes, it doesn’t make much of an impression now. But in the future, the Leonids may make a loud statement again.
“The Day of Judgement”
On the night of 12-13 November 1833, North Americans from the East Coast to the Rocky Mountains witnessed something truly incredible. A storm of shooting stars coming from the Leo constellation literally covered the Earth. The sky in every direction was filled with trails of light. In Boston, the frequency of meteor impacts was estimated to be about half that of flakes of snow in a moderate snowstorm. According to one estimate, more than 240,000 shooting stars appeared in the sky in nine hours.
Not surprisingly, the event was reflected in Native American legends and slave songs, while some preachers claimed that it was a sign from God indicating the imminent approach of the Day of Judgement. Despite the fact that the meteor storm was observed only in North America, it was widely discussed in Europe. The event became an important catalyst that contributed to a significant increase in interest in the meteor showers.
In November 1866 and 1867, the Earth was again covered by the meteor showers. They were more modest than the event in 1833, but at their peak they still produced several thousand shooting stars per hour. The Italian astronomer Giovanni Schiaparelli (the same one who later “discovered” the Martian canals) guessed that this phenomenon was connected with the recently discovered Comet Tempel-Tuttle. Its orbital period was about 33 years, which coincided with outbursts of activity of the meteor shower, which was called the Leonids. Further observations confirmed this assumption.
Over the next hundred years, the Leonids did not particularly please observers. In 1899 and 1933, the peak number of meteors was only a few hundred per hour. But in 1966, the Leonids made a loud statement again. On 17 November, a full-fledged meteor storm of about 30,000 meteors per hour could be seen in North America.
The next major peak of Leonid activity occurred in 1999-2001. Some experts expressed concern that they could cause significant damage to the ISS and satellites in Earth orbit. The fact is that the orbit of Comet Tempel-Tuttle is inclined to the ecliptic at an angle of almost 173°, meaning that it rotates in the direction almost opposite to the motion of the major planets. As a result, the dust particles it ejects collide with the Earth on a “collision course” and enter the atmosphere at a speed of 71 km/s, making them more dangerous due to their higher kinetic energy.
Fortunately, these fears were not justified. The Leonids did not cause any damage to the ISS, and their activity was significantly lower than in 1966, ranging from two to five thousand meteors per hour. However, on the eve of the next Leonids, the station’s crew still receives additional warnings.
When to watch the Leonids
The Leonids are observed between 6 and 30 November. This year, the peak of their activity will be on the night of 16-17 November. The radiant of the stream (the point of departure of the meteors) is located in the Leo constellation. Observations should start after midnight, when the radiant of the stream rises above the horizon. It will be located in the northeast. To find it in the sky, it is best to use one of the mobile astro apps or planetarium programs, such as Stellarium or Starwalk.
It is worth noting that since the last surge in 1999-2001, the Leonid activity has been steadily declining. In recent years, the ZHR (zenith hourly number) for this shower has not exceeded 15. It determines how many meteors per hour an observer can see in an “ideal” sky if the radiant is at its zenith. Naturally, the actual number of shooting stars that can be seen will be less.
Unfortunately, the peak of the Leonid will fall almost on a full moon in 2024. The lunar disc will be 98% illuminated, which will make observing it much more difficult. So, this year, don’t expect any special “show”.
But what about the future? Do we have a chance of seeing a meteor storm in the early 2030s, when the Comet Tempel-Tuttle returns to the Sun?
So far, astronomers have made rather conservative predictions in this regard. It should be understood that the Leonids do not occur when passing through “fresh” cometary ejecta, but when the Earth passes through older clusters of material left over from its previous visits. For example, the 1966 storm was caused by passing through a stream of dust left over from the 1899 perihelion.
Unfortunately, the calculations do not paint a very optimistic picture at the moment. It seems that the Earth will not encounter dense clouds of debris until 2099. Therefore, when the comet returns in 2031 and 2064, there will be no meteor storms. But at least we can count on a few good displays of Leonid activity in 2033 and 2034, when the ZHR should exceed 100.
But this is only a forecast. Time will tell what the real activity of Leonid will be and whether they will be able to surprise us again.
