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Ahmad ibn Muhammad

Ahmad ibn Muhammad

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Ahmad ibn Muhammad
Amir of the Saffarid dynasty
AhmadIbnMuhammadSaffaridCoin.jpg
Coin of Ahmad
Reign923–963
PredecessorAmr ibn Ya'qub
SuccessorKhalaf ibn Ahmad
DiedMarch 963
Zarang
HouseSaffarids
FatherMuhammad ibn Khalaf
ReligionSunni Islam

Abu Ja'far Ahmad ibn Muhammad (June 21, 906 – March 31, 963) was the amir of Sistan from 923 until his death in 963. He is responsible for restoring Saffarid rule over Sistan, and was a great patron of the arts.

Ancestors[edit]

Abu Ja'far Ahmad's father was named Muhammad. Muhammad was very distantly related to the founder of the Saffarid amirate, Ya'qub-i Laith Saffari; his great-great-grandfather had been the brother of Ya'qub's great-grandfather. Muhammad shared a closer connection with Ya'qub's brother and successor Amr bin Laith, having married the latter's granddaughter.

Life[edit]

Abu Ja'far Ahmad's rise to power began in May 923, when the people of Zarang proclaimed him amir. Sistan at that time was ruled by 'Abdallah ibn Ahmad, who was unpopular in Zarang due to his harsh taxes. Taking advantage of his ties to the Saffarids, Abu Ja'far Ahmad gained the support of the city 'ayyars, who stopped an attempt by 'Abdallah's son 'Aziz to maintain control of the town. Abu Ja'far Ahmad's rule soon expanded outside Zarang; 'Abdallah's representative in al-Rukhkhaj defected to him and the citizens of Bust threw their support behind the Saffarid as well. 'Abdallah was defeated in battle by Abu Ja'far Ahmad's supporters, forcing him to make for Samanid Khurasan. He was captured, however, and brought back to Zarang in October 923. His capture ended his rule for good.

Although 'Abdallah was no longer a threat to Abu Ja'far Ahmad, his son 'Aziz remained opposed to him. Some of Abu Ja'far Ahmad's supporters turned against him and threw their support behind 'Aziz, forcing the Saffarid to march on Bust twice to subdue the rebels. 'Aziz attempted to conquer Sistan but was defeated by a Saffarid army towards the end of 925. He fled to Khurasan, ending his attempt to take over Sistan.

Having successfully defended against the rebels, Abu Ja'far Ahmad sought to expand his realm at the expense of the Abbasid Caliphate, which had been suffering a series of setbacks over the last several years. He therefore sent several of his officials to Kerman, a province which had formerly belonged to the Saffarids. Taxes were collected by the officials, who then returned to Sistan. Saffarid authority over Kerman was therefore only temporary; the Abbasids held a loose grip on the province for a few more years before the Banu Ilyas took over in 932.

Abu Ja'far Ahmad continued to be preoccupied with unrest in Bust. He had to personally arrive at the town in 931 to deal with a rebellion, and another force was sent in the following year. Events in the neighboring Samanid amirate also contributed to the troubles. In 930 a plot to overthrow the Samanid amir Nasr b. Ahmad and replace him with his brothers failed. A few individuals involved in the plot arrived in Bust in 932 at the head of a contingent of troops and attacked the Saffarid governor there. Abu Ja'fa Ahmad was forced to arrive at the head of an army and defeat the fugitives. Because he was frequently needed in Bust and other parts of the eastern provinces, Abu Ja'far Ahmad often left Zarang in the hands of the three sons of one Tahir b. Asnam.

After these initial troubles, Sistan and the outlying provinces calmed down for several years, making for a relatively peaceful period in Abu Ja'far Ahmad's reign. He was held in high regard by his neighbors; even the Samanids, the historical enemies of the Saffarids, were apparently friendly with him (in fact, the poet Rudaki praised the Saffarid's name in a panegyric at the Samanid court in Bukhara, see below). Other poets, both Persian and Arabic, also viewed the amir favorably. Many scholarly gatherings in Sistan were conducted, and were attended by leaders in the field such as Abu Sulayman Muhammad al-Sijistani and Nasafi.

This peace was not to last, however. Different factions outside the capital soon came to violence against each other, forcing the dispatch of the army. From the 950s on there was continuing unrest in Sistan. In the meantime, the three sons of Tahir b. Asnam who sometimes governed in Abu Ja'far Ahmad's name when he was absent from Zarang fell from favor and were imprisoned. In their place, Abu'l-Fath, the commander of the army, took over many functions of the government. He eventually revolted, however, and gained a large degree of support from the people outside of Zarang. Abu'l-Fath was further supported by another Saffarid, Abu'l-'Abbas b. Tahir, who, as a great-grandson of Amr b. Laith, could claim to be directly related to the original Saffarid amirs (in contrast, Ab Ja'far Ahmad could only claim descent from Amr on his mother's side).

The pretender Abu'l-'Abbas, together with Abu'l-Fath, advanced against Zarang. Abu Ja'far Ahmad met them in battle, and together with Turkish reinforcements from Bust, defeated the rebels. Abu'l-Fath fled to Nishapur, where he eventually died in the summer of 963.

Abu'l-'Abbas, on the other hand joined a plot with one of Abu Ja'far Ahmad's Turkish ghulams. Together, they killed Abu Ja'far Ahmad at a drinking party at the end of March 963[1] and plundered his treasury. The amir's son and heir, Abu Ahmad Khalaf, happened to outside of the capital the night of the murder and less than two months later managed to establish himself in Zarang.

References[edit]

  1. ^ Saffarids, The Encyclopedia of Islam, Vol. VIII, Ed. C.E.Bosworth, E. van Donzel, W.P.Heinrichs and G. Lecomte, (Brill, 1995), 797.

Sources[edit]

  • Bosworth, C.E. (1975). "The Ṭāhirids and Ṣaffārids". In Frye, R.N. (ed.). The Cambridge History of Iran, Volume 4: From the Arab Invasion to the Saljuqs. Cambridge: Cambridge University Press. pp. 90–135. ISBN 0-521-20093-8.
  • Bosworth, C.E. The History of the Saffarids of Sistan and the Maliks of Nimruz (247/861 to 949/1542-3). Costa Mesa, California: Mazda Publishers, 1994.
Preceded by
Abu Hafs 'Amr
Saffarid amir
923–963
Succeeded by
Abu Ahmad Khalaf
Preceded by
'Abdallah ibn Ahmad
Amir of Sistan
923–963
Succeeded by
Abu Ahmad Khalaf

Tisserand's parameter

Tisserand's parameter

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Tisserand's parameter (or Tisserand's invariant) is a value calculated from several orbital elements (semi-major axis, orbital eccentricity and inclination) of a relatively small object and a larger "perturbing body". It is used to distinguish different kinds of orbits. The term is named after French astronomer Félix Tisserand, and applies to restricted three-body problems in which the three objects all differ greatly in mass.

Definition[edit]

For a small body with semi-major axis , eccentricity , and inclination , relative to the orbit of a perturbing larger body with semimajor axis , the parameter is defined as follows:[1]

The quasi-conservation of Tisserand's parameter is a consequence of Tisserand's relation.

Applications[edit]

  • TJ, Tisserand's parameter with respect to Jupiter as perturbing body, is frequently used to distinguish asteroids (typically ) from Jupiter-family comets (typically ).[2]
  • The minor planet group of damocloids are defined by a Jupiter Tisserand's parameter of 2 or less (TJ ≤ 2).[3]
  • The roughly constant value of the parameter before and after the interaction (encounter) is used to determine whether or not an observed orbiting body is the same as one previously observed in Tisserand's criterion.
  • The quasi-conservation of Tisserand's parameter constrains the orbits attainable using gravity assist for outer Solar System exploration.
  • TN, Tisserand's parameter with respect to Neptune, has been suggested to distinguish near-scattered (affected by Neptune) from extended-scattered trans-Neptunian objects (not affected by Neptune; e.g. 90377 Sedna).
  • Tisserand's parameter could be used to infer the presence of an intermediate-mass black hole at the center of the Milky Way using the motions of orbiting stars.[4]

Related notions[edit]

The parameter is derived from one of the so-called Delaunay standard variables, used to study the perturbed Hamiltonian in a three-body system. Ignoring higher-order perturbation terms, the following value is conserved:

Consequently, perturbations may lead to the resonance between the orbital inclination and eccentricity, known as Kozai resonance. Near-circular, highly inclined orbits can thus become very eccentric in exchange for lower inclination. For example, such a mechanism can produce sungrazing comets, because a large eccentricity with a constant semimajor axis results in a small perihelion.

See also[edit]

References[edit]

  1. ^ Murray, Carl D.; Dermott, Stanley F. (2000). Solar System Dynamics. Cambridge University Press. ISBN 0-521-57597-4.
  2. ^ "Dave Jewitt: Tisserand Parameter". www2.ess.ucla.edu. Retrieved 2018-03-27.
  3. ^ Jewitt, David C. (August 2013). "The Damocloids". UCLA – Department of Earth and Space Sciences. Retrieved 15 February 2017.
  4. ^ Merritt, David (2013). Dynamics and Evolution of Galactic Nuclei. Princeton, NJ: Princeton University Press. ISBN 9781400846122.

External links[edit]

Bob Scarpitto

Bob Scarpitto

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Bob Scarpitto
No. 46, 82
Position:Flanker / Halfback / Punter
Personal information
Born: (1939-01-07) January 7, 1939 (age 80)
Rahway, New Jersey
Height:5 ft 11 in (1.80 m)
Weight:192 lb (87 kg)
Career information
High school:Rahway (Rahway, New Jersey)
College:Notre Dame
AFL draft:1961 / Round: 9 / Pick: 71
Career history
Career highlights and awards
Career NFL statistics
Player stats at NFL.com
Player stats at PFR

Bob Scarpitto was an American college and professional football player. A halfback, flanker and punter, he played college football at the University of Notre Dame, and played professionally in the American Football League for the San Diego Chargers in 1961, for the Denver Broncos from 1962 through 1967, and then for the AFL's Boston Patriots in 1968. He was an American Football League All-Star in 1966.

As of 2017's NFL off-season, Bob Scarpitto held at least 3 Broncos franchise records, including:

  • Most punts in a season (105 in 1967)
  • Most punts in a game (12 on 1967-09-10 @OAK; tied with 2 others)
  • Most punt yards in a game (565 on 1967-09-10 @OAK)

Scarpitto played high school football at Rahway High School.[1]

See also[edit]

References[edit]

  1. ^ Bob Scarpitto Archived 2007-09-29 at the Wayback Machine, database Football. Accessed December 23, 2007.

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