A question about meteor showers

[Ags]

The Lyrids (for example) originate from the long period comet C/1861 G1 Thatcher. As we cross the orbit of the comet's debris, does that mean we will at some point collide with the comet itself? The same applies to the parent body of every other meteor shower.

[Leo S]

Good question

The answer is probably "no" in the case of the vast majority of meteor showers.

We can get a meteor shower if the parent body comes close to crossing Earth's orbit, but does not actually cross it. This is because forces like gravity (usually from the likes of Jupiter and Saturn) and solar radiation pressure can push meteoroids/whole dust streams into orbits where they do cross Earth's orbit.

Parent bodies like this are classed as Near Earth Objects (NEOs), but not necessarily Potentially Hazardous Objects (PHOs) as far as I'm aware.

If you think about it, even if a PHO does cross Earth's orbit, the sizes of both orbits that are involved are so huge, there is lots of room for an object to miss Earth, and most of the time they will (in the case of large objects).

But things are not always quite so simple!

Enter the Taurids, a meteor shower with a few key differences to other showers, that make it potentially quite problematic for us. The Taurids are the result of a giant comet that broke up many thousands of years ago, which has created a debris field of commentary fragments that span a significant part of their orbit (unlike other showers - each of these can be considered a small parent body), and evidence has been mounting that there are MANY significantly large fragments contained within what we now call the Taurid Meteoroid Complex. I outlined some of the main features of the Taurids/TMC here, if you scroll down to the last post:

 

[Leo S]

Just a little bonus factoid relating to the Tairids. A few years back there was some research that suggested that the zodiacal light is caused mainly by dust belonging to the TMC.

[Leo S]

Just to add a little more...

I want to stress, that the likelihood of an impact with a parent body (PB)/larger fragments is extremely low in many cases, because even though orbits may cross, the PB orbits have a relatively high inclination with respect to Earth's orbit.

For example, if the orbit of a PB is at 90 degrees to Earth's orbit, the time the PB actually spends in Earth's orbit is as low as it can get, meaning it has much less chance (effectively 0) of impact. If on the other hand, the inclination of the PB's orbit with respect to Earth's is 0 degrees, then the chance of impact can be 100% (if orbit size also matches)!

The Taurids of course fall into the latter category, with an orbit that has a very low inclination, making the probability of impacts much higher due to this and the fact that there are many sizable fragments, not just one single PB.

Apart from the Taurid Complex there are not many showers with orbits like this thankfully, but there is one other (which I completely forgot to mention in my earlier reply), the Virginid Complex, which also has a very low inclination, and crosses Earth's orbit in two places, just like the Taurid Complex. It's another one that needs more research, but looks like it's less of a danger than the Taurids.

Also, regarding the Taurid Complex, just to put some more flesh on the bone, here is a paper worth reading:

 

Abstract:

"Using the Secular Light Curve (SLC) formalism (Ferrín, 2010), we have catalogued 88 probable members of the Taurid Complex (TC). 51 of them have useful SLCs and 34 of these (67%) exhibit cometary activity. This high percentage of active asteroids gives support to the hypothesis of a catastrophe that took place during the Upper Paleolithic (Clube and Napier, 1984), when a large short-period comet, arriving in the inner Solar System from the Kuiper Belt, experienced, starting from 20 thousand years ago, a series of fragmentations that produced the present 2P/Encke comet, together with a large number of other members of the TC. The fragmentation of the progenitor body was facilitated by its heterogeneous structure (very similar to a rubble pile) and this also explains the current coexistence in the complex of fragments of different composition and origin. We have found that (2212) Hephaistos and 169P/NEAT are active and members of the TC with their own sub-group. Other components of the complex are groups of meteoroids, that often give rise to meteor showers when they enter the terrestrial atmosphere, and very probably also the two small asteroids that in 1908 and 2013 exploded in the terrestrial atmosphere over Tunguska and Chelyabinsk, respectively. What we see today of the TC are the remnants of a very varied and numerous complex of objects, characterized by an intense past of collisions with the Earth which may continue to represent a danger for our planet."

Others can be found with this search.

 

Edited Wednesday at 19:23 by Leo S