Explanation: You couldn't see Comet Leonard’s extremely long tail with a telescope -- it was just too long. You also couldn't see it with binoculars -- still too long. Or with your eyes -- it was too dim. Or from a city -- the sky was too bright. But from a dark location with a low horizon -- your camera could. And still might -- if the comet survives today's closest encounter with the Sun, which occurs between the orbits of Mercury and Venus. The featured picture was created from two deep and wide-angle camera images taken from La Palma in the Canary Islands of Spain late last month. Afterwards, if it survives, what is left of Comet Leonard's nucleus will head out of our Solar System, never to return.
<<Autotomy (from the Greek auto-, "self-" and tome, "severing", αὐτοτομία) or self-amputation, is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude a predator's grasp or to distract the predator and thereby allow escape. [Note: not to be confused with Autonomy (from the Greek auto-, "self" (see auto-) and nomos "custom, law"): the capacity to make an informed, uncoerced decision.] Some animals have the ability to regenerate the lost body part later. Autotomy has multiple evolutionary origins and is thought to have evolved at least nine times independently in animalia.
Some lizards, salamanders and tuatara when caught by the tail will shed part of it in attempting to escape. In many species the detached tail will continue to wriggle, creating a deceptive sense of continued struggle, and distracting the predator's attention from the fleeing prey animal. In addition, many species of lizards have elaborately colored blue tails which have been shown to divert predatory attacks toward the tail and away from the body and head. Depending upon the species, the animal may be able to partially regenerate its tail, typically over a period of weeks or months. Though functional, the new tail section often is shorter and will contain cartilage rather than regenerated vertebrae of bone, and in color and texture the skin of the regenerated organ generally differs distinctly from its original appearance. However, some salamanders can regenerate a morphologically complete and identical tail. Some reptiles such as the crested gecko do not regenerate the tail after autotomy.
The technical term for this ability to drop the tail is caudal autotomy. In most lizards that sacrifice the tail in this manner, breakage occurs only when the tail is grasped with sufficient force, but some animals, such as some species of geckos, can perform true autotomy, throwing off the tail when sufficiently stressed, such as when attacked by ants. Caudal autotomy in lizards takes two forms. In the first form, called intervertebral autotomy, the tail breaks between the vertebrae. The second form of caudal autotomy is intravertebral autotomy, in which there are zones of weakness, fracture planes across each vertebra in the mid-part of the tail. In this second type of autotomy the lizard contracts a muscle to fracture a vertebra, rather than break the tail between two vertebrae.Sphincter muscles in the tail then contract around the caudal artery to minimize bleeding. Another adaptation associated with intravertebral autotomy is that skin flaps fold over the wound at the site of autotomy to readily seal the wound, which can minimize infection at the autotomy site. Caudal autotomy is prevalent among lizards; it has been recorded in 13 of approximately 20 families.>>
Re: APOD: Comet Leonard's Long Tail (2022 Jan 03)
Posted: Mon Jan 03, 2022 6:02 pm
by Sundown
Hello,
I was just wondering why, if there is no air in space to move around or didipate it(like a contrail), is the tale not straight for all those miles? Is it because of Solar Wind?
Re: APOD: Comet Leonard's Long Tail (2022 Jan 03)
Posted: Mon Jan 03, 2022 6:52 pm
by neufer
Sundown wrote: ↑Mon Jan 03, 2022 6:02 pm
I was just wondering why, if there is no air in space to move around or dissipate it (like a contrail),
is the tail not straight for all those miles? Is it because of Solar Wind?
The ion tail is affected by the solar wind, magnetic fields & coronal mass ejections.
Sundown wrote: ↑Mon Jan 03, 2022 6:02 pm
I was just wondering why, if there is no air in space to move around or dissipate it (like a contrail),
is the tail not straight for all those miles? Is it because of Solar Wind?
The ion tail is affected by the solar wind, magnetic fields & coronal mass ejections.
This answer is unsatisfying to me. What other comet tails have been like this one, all whiffs of smoke-like in appearance and not straight? This one seems to be pretty unusual. My google-fu isn't turning up much at all. It almost looks like this comet has entered the (earth's) atmosphere and its tail is acting like an long-lived contrail! I'd guess that the discontinuous gas and dust outbursts are contributing to the crooked appearance... somehow. Hmm, what would the tail look like if the output was continuous? Would it's overall shape still be the same, just not... discontinuous?
Sundown wrote: ↑Mon Jan 03, 2022 6:02 pm
I was just wondering why, if there is no air in space to move around or dissipate it (like a contrail),
is the tail not straight for all those miles? Is it because of Solar Wind?
The ion tail is affected by the solar wind, magnetic fields & coronal mass ejections.
This answer is unsatisfying to me. What other comet tails have been like this one, all whiffs of smoke-like in appearance and not straight? This one seems to be pretty unusual. My google-fu isn't turning up much at all. It almost looks like this comet has entered the (earth's) atmosphere and its tail is acting like an long-lived contrail! I'd guess that the discontinuous gas and dust outbursts are contributing to the crooked appearance... somehow. Hmm, what would the tail look like if the output was continuous? Would it's overall shape still be the same, just not... discontinuous?
A very straight ion tail is pretty unlikely. We normally see them because in most comet images the scale is such that we're only looking at a few degrees, not tens of degrees. The longer the tail, the more buffeted it will be. This comet experienced a significant outburst, which created a very long tail. The length of the tail is what is unusual, not its structure.
neufer wrote: ↑Mon Jan 03, 2022 6:52 pm
The ion tail is affected by the solar wind, magnetic fields & coronal mass ejections.
This answer is unsatisfying to me. What other comet tails have been like this one, all whiffs of smoke-like in appearance and not straight? This one seems to be pretty unusual. My google-fu isn't turning up much at all. It almost looks like this comet has entered the (earth's) atmosphere and its tail is acting like an long-lived contrail! I'd guess that the discontinuous gas and dust outbursts are contributing to the crooked appearance... somehow. Hmm, what would the tail look like if the output was continuous? Would it's overall shape still be the same, just not... discontinuous?
A very straight ion tail is pretty unlikely. We normally see them because in most comet images the scale is such that we're only looking at a few degrees, not tens of degrees. The longer the tail, the more buffeted it will be. This comet experienced a significant outburst, which created a very long tail. The length of the tail is what is unusual, not its structure.
Let's compare:
Other comet tails compared with Comet Leonard
Ok, those 4 comet tail examples of yours all look pretty straight, and not at all curvy like today's APOD. But you're saying that the reason is essentially that they are all showing a much shorter length of tail than what's shown of Comet Leonard's? That perhaps only the green dashed line part of Leonard is comparable in angular length to the others? If so, I guess that makes sense, though I'm still left looking for the curvy tail of another comet comparable to Leonard's. I take it they are rare.
Re: APOD: Comet Leonard's Long Tail (2022 Jan 03)
Posted: Tue Jan 04, 2022 5:45 pm
by MoonRockMan
Is there a possibility that the Earth may sweep through the tail at some point?
Comet Leonard's Long Tail
