One Night Only, a New Meteor Shower that May Be Spectacular?
Posted by Bruce Betts
22-05-2014 16:36 CDT
Ladies and Gentleman, Boys and Girls: One night only, May 23/24, the challenger -- Comet 209P/LINEAR dusty debris vs. the champion--planet Earth, smackdown! Be there!
Alright, it won’t be much of a fight since all the comet debris will burn up high in the Earth’s atmosphere, but as it does so, it still could make for a spectacular event to watch. A new meteor shower, the Camelopardalids, will be peaking Friday night/Saturday morning (May 23/24, 2014) just after midnight Pacific time. If you are in the U.S. or southern Canada, you are likely well positioned to see what may (or may not) be a spectacular show. In either case, scientists will learn about a comet’s history and you can have a fun night looking at the sky.
Meteor showers happen when Earth passes through the debris shed from a comet. When that debris (usually dust and sand sized) hits the Earth’s atmosphere at tens of kilometers per second, it heats up due to friction and glows, making a streak across the sky we call a meteor.
The debris comes from Comet 209P/LINEAR which was discovered in 2004. Esko Lyytinen and Peter Jenniskens looked at the comet’s orbit and expected orbital evolution and predicted this week’s shower. Their orbital predictions have been confirmed by others as well, including Jeremie Vaubaillon who calculated that all dust trails of the comet created between 1803 through 1924 will be in Earth's path for the 2014 encounter. What no one knows for sure, because we don’t have the data needed to predict, is how many meteors will there be per hour: a few, tens, hundreds, or even thousands, which would qualify it as a meteor “storm.”
The Tale of a Comet
“Keep your expectations low…but don’t miss it.”
I talked to co-predictor of the shower Peter Jenniskens from the SETI Institute, and he had the following sage advice about the shower, “Keep your expectations low…but don’t miss it.” From him, I learned many other interesting things about this unusual celestial show, including the following:
- This meteor shower is unusual. This will be the first time Earth will pass through that comet’s orbit at this time of year, AND this will be the only time we are predicted to pass through dense debris clouds near the comet itself. The comet itself will pass through this same region on May 29. Debris clouds, since they come from material shed from the comet itself, tend to concentrate near the comet in its orbit and gradually spread out. Since this debris cloud represents material shed in about the last two hundred years of passes in towards the Sun, it has not spread out much and may remain quite dense. The comet’s orbit evolves naturally over time, bringing Earth through this comet orbit for the first time this year. We will continue to pass through this comet and debris orbit until 2044 when they evolve out beyond Earth’s orbit. However, only in 2014 will we pass so close to the comet and thus so close to the debris cloud that makes for many happy meteors. So…don’t miss it. In future years, there will likely be only a wee bit to no shower. More broadly, this type of pass from a member of this family of comets doesn’t happen often…
- This comet is a Jupiter family comet, meaning it goes out to near the orbit of Jupiter on the outer part of its orbit. Thus, Jupiter family comets have orbital periods of only a few to many years – 5.1 years in the case of this comet. That means they come towards the Sun every few years, and that means their ices sublimate (turn from ice to gas) regularly under the increased heat. And, that means they end up not very productive in terms of additional gas and associated dust output, which could be a bad sign for our meteor shower potential. No matter what, Peter says that the results will provide good science, providing insight into the dust output of this comet over the last couple hundred years and from that, insight into the nature of the Jupiter family of comets.
- Because they have such frequent visits to the inner solar system, Jupiter family comets actually provide 85% of the material in the ‘zodiacal cloud,’ not a terrifying undead swarm as it may sound, but instead a pancake shaped cloud of dust in the inner solar system that can be seen from dark sites as a faint diffuse glow along the ecliptic (path of the Earth’s orbit) in the night sky. This makes what we learn from our friend Comet 209P/LINEAR even more significant.
- Because we are passing through the debris of the last couple hundred years that, as mentioned, hasn’t had time to spread out much, the peak of the meteor shower will be much shorter (a couple hours?) than ones we are usually familiar with (often spread over days due to more debris over longer time in more stable orbits).
- Even if there are not a lot of meteors, the meteors there are may be particularly beautiful due to two factors. The one we are certain of is the relative speed at which they will hit the atmosphere: 19.4 km/s, which, though amazingly fast by human standards, is slow by meteor shower standards, meaning the meteors will appear to glide rather than streak across the sky, to use rather non-technical terms. Secondly, which is more uncertain, Quanzhi Ye (who as an 18 year old was a Planetary Society Shoemaker NEO Grant winner) and Paul A. Wiegert looked at the activity of the comet on its last orbit and found that some of the particles ejected are relatively large, which still means pretty small particles that will burn up high in the atmosphere, but the increase in size means they will look brighter doing it.
- The estimated size of this comet just went up considerably in the last couple weeks due to the better observing geometry allowing for better observations. The comet is now estimated to be between 1.9 and 4.9 km, which, Peter says, makes it a garden variety Jupiter family comet.
Another note: the comet pass by Earth will be the 9th closest comet pass on record (counting only those with reliable orbits), but still more than 21 Earth-Moon distances. However, due to its low output of dust and gas making for a small coma/tail, the comet itself is predicted to be very dim, requiring a good amateur telescope to be able to see it.
When and From Where to Look
The meteor shower peak is predicted to be about 07:20 UT (00:20 PDT) on Saturday May 24, so shortly after midnight Pacific time on the night that starts on Friday May 23. If you are going to devote only a small amount of time to this endeavor, your best bet is to focus on the time around that peak time, perhaps an hour before and after if you have the time and patience. More time will increase your chances, particularly due to uncertainties. Because of the timing, the expected sharpness of the peak, and the meteors coming from roughly the north, the United States and some of Canada are the favored locations for observing. The Moon is not up until later in the night, making for incredibly lucky dark sky conditions.
The Camel Leopard: Where to Look in the Sky
Meteor showers are named after the constellation that contains the radiant of the shower. The radiant is where the meteors appear to emanate from: if you draw a line back along the meteors, all of the lines will meet at a point. It is an effect of us (Earth) moving through a discrete cloud of stuff. This shower’s radiant will be in a rather dim constellation that makes up for it with a really long name, Camelopardalis, which is not too far from the North Star, the Big Dipper, and rest of the gang up by the North celestial pole. (Random Space Fact: Camelopardalis comes from Latin derived from Greek for giraffe, which was a compound of camel leopard, so named because the giraffe had the long neck of a camel and the spots of a leopard.) What this location means for the North America observers that are favored by the time of the event is that you can look most anywhere in the sky. Ideal is often said to be 45 degrees away from the radiant, but probably more important is to find the darkest place you can, don’t have a light in your eyes, and look at the darkest patch of sky you can.
How Good Will the Shower Be?
In terms of science, the shower should be great. In terms of how many meteors people will see, it is uncertain because of how little we know about how much dusty stuff got kicked off the comet in the last couple hundred years. Predictions range from tens to thousands per hour, with most in the 50 to 200 per hour range from a dark site. For comparison, the best “normal” meteor shower of the year is usually the Geminids with a peak of about 100 per hour from a dark site.
We’ve got a dark sky due to lack of moonlight and a pass through a hopefully high density debris relatively near the comet itself, weighed against the Jupiter family comets being notoriously low producers of dust (we think). The only way to find out the answer to how many meteors will there be will be to watch the event itself, or find out from someone else, but that is not nearly as fun. If you can’t watch your own sky due to location or clouds, some groups are broadcasting live web feeds including Planetary Society Shoemaker NEO Grant winner Gianluca Masi. He has teamed with several observers in the U.S. and Canada to have images online at his Virtual Telescope page. Several sites will also post near real time updates on the shower in the hours around the peak including the SETI Institute Meteor Showers page and links therein.