Starship Asterisk*

Chris Peterson wrote:

Spif wrote:
So what I'm wondering is, what are the odds? Whatever nudged this comet initially must have been pretty severe to divert it from a presumably stable orbit way out there and subsequently aim it almost directly at the sun? That must have been a huge deflection.

Not sure what you mean by "what are the odds". There may be billions of bodies in the Oort cloud, so the chance that any one of them will be perturbed into the inner system is small. But such perturbations are common, happening every few years. So in that sense, the odds are high.

Bodies that distance from the Sun are bound only very lightly. While their orbits may be seen as stable, they need only the slightest perturbation- just a few meters per second- to reach escape velocity. Nothing more than a close pass from another small body, a chance positioning of the planets, or even the position of a nearby star can be enough to generate the necessary delta-v. So these bodies are very easily deflected into highly eccentric orbits that pass close to the Sun. It isn't a large deflection at all.

neufer wrote:While it takes only a small deflection to nullify an Oort cloud object's angular momentum...
how does the angular momentum get canceled out almost completely?

This will be the first pass of Comet ISON (C/2012 S1) and it has an eccentricity ~ 1.0000021.

ta152h0 wrote:I am not a person who was given the appreciation of art as my mother ( RIP ) tried so hard to do so I always question how art and science can benefit each other. Science to art is easy but the reverse may be questionable. This APOD makes the latter more plausible.

http://en.wikipedia.org/wiki/Eusebio_Francisco_Kino wrote:
<<Eusebio Francisco Kino, (10 August 1645 – 15 March 1711) was a Jesuit priest whose Exposisión astronómica de el cometa (Mexico City, 1681) on the Great Comet of 1680 is among the earliest scientific treatises published by a European in the New World. This publication was later the subject of a sonnet by the noted colonial nun and poetess of New Spain, Sor (Sister) Juana Inés de la Cruz.

Kino's was the son of Franz Kühn (or Francesco Chini) and he was educated in Innsbruck, Austria. He taught mathematics in Ingolstadt, he received Holy Orders as a priest on 12 June 1677. Although Kino wanted to go to the Orient, he was sent to New Spain. Due to travel delays while crossing Europe, he missed the ship on which he was to travel and had to wait a year for another ship. While waiting in Cadiz, Spain, he wrote some observations, done during late 1680 and early 1681, about his study of a comet (later known as Kirch's comet), which he subsequently published upon arriving in Mexico.

Father Kino enjoyed making model ships out of wood. His knowledge of maps and ships led him to believe that Mexican Indians could easily access Baja California by sea, a view taken with skepticism by missionaries in Mexico City. When Kino proposed and began making a boat that would be pushed across the Sonoran Desert to the Mexican west coast, a controversy arose, as many of his co-missionaries began to question Kino's faculties. However, Kino was able to prove that Baja California is not an island by leading an overland expedition there.

Kino opposed the slavery and compulsory hard labor in the silver mines that the Spaniards forced on the native people. In 1965, a statue of Kino was donated to the United States Capitol's National Statuary Hall collection, one of two statues representing Arizona. In John Steinbeck's novel, The Pearl, it is implied the protagonist is named after the missionary.>>

Stinky Old Man wrote:

ta152h0 wrote:I am not a person who was given the appreciation of art as my mother ( RIP ) tried so hard to do so I always question how art and science can benefit each other. Science to art is easy but the reverse may be questionable. This APOD makes the latter more plausible.

Earth without art is literally just "eh"

Anthony Barreiro wrote:
If we're looking southwest during evening dusk on Saturday 28 December, 1680, the light of the Moon, approaching first quarter, would account for the shadows on the snow-covered ground. The comet is conjuncting Venus! (This conjunction might account for the popularity of cross-staffs). The stars don't match up very well, but maybe Verschuier just put some random stars in for effect. According to his wikipedia article he was known for painting ships and landscapes, maybe he just wasn't very careful about creating a star chart.

• The cross-staffs might make more sense if it was 'Eerste Kerstdag' the 25th of December.

http://www.jwwerner.com/history/Comet.html wrote:

[b][color=#0000FF]The Great Comet of 1680 as seen from Nuremburg.[/color][/b]

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This is what the first Dutch settlers of Esopus, New York, saw in the sky over 300 years ago! Excerpt from The History of Kingston, by Marius Schoonmaker, 1888, at page 70:

On the 9th of December 1680, there appeared an extraordinary comet, which caused very great consternation throughout the province, with forebodings of dreadful happenings and divine punishments. It is described, in a letter dated January 1st, 1681, as having "appeared in the Southwest on the ninth of December last, about two o'clock in the afternoon, fair sunshine weather, a little above the sun, which takes its course more northerly, and was seen the Sunday night [Dec. 15, NS], right after about twilight, with a very fiery tail or streamer in the west, to the great astonishment of all spectators, and is now seen every night with clear weather. Undoubtedly, God threatens us with dreadful punishments if we do not repent." The letter then suggested the propriety of proclaiming a day of humiliation and prayer.
...........................................................................
One more “first hand” account of the Comet as seen from Scotland! Attributed to The Reverend Robert Law(approx 1624-1689). Law was a minister during the tumultuous “Restoration Period” of Scottish history and author of The Memorable Things that Fell Out within this Island of Brittain from 1638 to 1684.): ‘December 10 [Dec. 20, NS], being Fryday, 1680, after sun-sett, there appeared in the west a comet, having a large broad and great streamer coming from it, the lyke was never seen or read of, and continued till the 16th or 17th day of January, growing smaller and smaller to it’s end;’

geckzilla wrote:I'm glad I live in the 2000's instead of the 1600's, but still... to be able to see comets over a city. For all that we've gained, we've still lost a little.

Nitpicker wrote: Aye, how we've gained since the Late Heavy Bombardment:
http://en.wikipedia.org/wiki/Late_Heavy_Bombardment

Ann wrote:Aye, but imagine being alive (however briefly) at that time and see spectacular comets and asteroids painting fantastic light tracks in the sky!!!

Ann wrote:
Aye, but imagine being alive (however briefly) at that time and see spectacular comets and asteroids painting fantastic light tracks in the sky!!!

• 1681: The last dodo bird is killed.
  
  1681: July 1 – Oliver Plunkett, Roman Catholic Primate
  of Ireland, falsely convicted of treason, is hanged,
  drawn and quartered at Tyburn, London.
  
  1681: October 28 – A London woman is publicly flogged
  for the crime of "involving herself in politics."

neufer wrote:1681: October 28 – A London woman is publicly flogged for the crime of "involving herself in politics."

Chris Peterson wrote:

neufer wrote:
While it takes only a small deflection to nullify an Oort cloud object's angular momentum...
how does the angular momentum get canceled out almost completely?

How are you figuring that the (orbital) angular momentum of the comet has changed significantly?

Chris Peterson wrote:

neufer wrote:
This will be the first pass of Comet ISON (C/2012 S1) and it has an eccentricity ~ 1.0000021.

To be clear, it is likely this body remains in a closed solar orbit.

Hence, a perihelion velocity increase of just 47 millimeters per second (= 188 m/s/4000)
is all that is required to reach escape velocity

In the case of a sungrazer this tiny (47mm/s) perihelion velocity increase could come either from:

• 1) strong cometary (tail) jets near perihelion from a rotating cometary nucleus and/or
  
  2) a gravitational assist near perihelion from a Sun moving at ~13m/s in the anti-Jupiter direction.

neufer wrote:

Chris Peterson wrote:To be clear, it is likely this body remains in a closed solar orbit.

Your figuring is wrong on that matter.

Chris Peterson wrote:

neufer wrote:

Chris Peterson wrote:To be clear, it is likely this body remains in a closed solar orbit.

Your figuring is wrong on that matter.

I didn't do any figuring. I'm simply noting that only a few percent of comets with osculating eccentricities greater than 1 as they neared perihelion actually were in hyperbolic solar escape orbits. The odds are that this one will also be elliptical once it is well pass perihelion.

The effects you mention can add energy to the orbit, but they can also remove it. In addition, there are other effects such as Yarkovsky that can be significant (either adding or removing energy, depending on the direction the body is rotating).

The bottom line is we won't know if this body is in an escape orbit until months after perihelion, but the odds are against it.

Chris Peterson wrote:

neufer wrote:
A perihelion velocity increase of just 47 millimeters per second
is all that is required [for Comet ISON] to reach escape velocity

In the case of a sungrazer this tiny (47mm/s) perihelion velocity increase could come either from:

• 1) strong cometary (tail) jets near perihelion from a rotating cometary nucleus and/or
  
  2) a gravitational assist near perihelion from a Sun moving at ~13m/s in the anti-Jupiter direction.

The effects you mention can add energy to the orbit, but they can also remove it.

Chris Peterson wrote:
In addition, there are other effects such as Yarkovsky that can be significant (either adding or removing energy, depending on the direction the body is rotating).

neufer wrote:The Yarkovsky effect is a photon type rocket whose momentum contribution is quite weak due to the E/c relationship. That's O.K. for long term effects on meteoroids and small asteroids but not for short term effects on comets. The chemical rocket equivalent of cometary jets should be much more efficient (solar energy wise) in generating thrust.