geographic north pole
qotb-e hudar-e zaminnegârik
Fr.: pôle nord géographique
→ north pole.
magnetic north pole
qotab-e hudar-e meqnâtisi
Fr.: pôle nord magnétique
A point of the → magnetosphere where the Earth's → magnetic field points vertically downward; in other words it has a 90° → magnetic dip toward the Earth's surface. The magnetic north pole can also be defined as the point toward which the south pole of the → compass needle is directed. The magnetic north pole is different from the → geographic north pole. It is actually hundreds of kilometers south of the geographic north pole. However, this has not always been the case. In the past 150 years it has moved more than 1,000 kilometers. Every 200,000 to 300,000 years the magnetic field of the Earth reverses direction, → magnetic reversal. Since the Earth's magnetic field is not exactly symmetrical, the north and south magnetic poles are not → antipodal.
M.E., O.E. norð, from P.Gmc. *nurtha- (cf. O.N. norðr, M.Du. nort, Du. noord, Ger. nord), ultimately from PIE *ner- "left, below."
North is related to left since it is to the left when one faces the rising Sun.
This occurs in, for example, the etymology of E. north, as above.
The same goes for Ar. shimal, which also means "left."
North America Nebula
miq-e Âmrikâ-ye hudari
Fr.: Nébuleuse de l'Amérique du Nord
An → H II region in → Cygnus, also known as NGC 7000, resembling the continent North America in long exposure images. This nebula is lying three degrees from bright star → Deneb and spans on the sky over four times the angular size of the full Moon. A dark lane separates the North America Nebula from the → Pelican Nebula, actually part of the same enormous cloud some 2,000 → light-years away.
It was first photographed in 1890 by Max Wolf (1863-1932), a German astronomer, who also first called it the North America Nebula because of its resemblance to the Earth's continent. America, from the feminine of Americus, the Latinized first name of the explorer Amerigo Vespucci (1454-1512), who made two trips to the New World as a navigator and claimed to have discovered it. The name America first appeared on a map in 1507 by the German cartographer Martin Waldseemüller, referring to the area now called Brazil; → nebula.
north celestial pole
qotb-e âsmâni-ye hudar
Fr.: pôle nord céleste
The point in the → northern hemisphere where the → rotation axis of Earth touches the → celestial sphere. The star → Polaris, also called the Pole Star, is located very near this point, at an angular separation of 42 degrees (about 1.4 lunar diameters).
Fr.: point Nord
North Polar Layered Deposits (NPLD)
Lerdhâ-ye Laye-laye-ye Qotb-e Hudar
Fr.: couches de dépôt du pôle nord
A large area of the north polar region of Mars which is covered with alternating layers of water ice and dust. → South Polar Layered Deposits.
North Polar Spur
šaxâk-e kahkešâni-ye hudari
Fr.: éperon galactique nord
One of the largest coherent structures in the radio sky, projecting from the → Galactic plane at → Galactic longitudel ~ 20° and extending to a very high → Galactic latitudeb ~ +80°. It was first identified in low frequency → radio surveys in the 1950s. The spur is also prominent in → soft X-rays. Its origins and nature have long been debated. However, what causes this phenomena is not well understood. It may be due to a combination of → OB associations and → supernova explosions.
Fr.: pôle nord
1) An → imaginary → point
in the → northern hemisphere representing the intersection
of the → Earth's → rotation axis
with the → globe or with the
→ celestial sphere.
North Pole Star
setâre-ye qotb-e hudar
Fr.: étoile du pole Nord
A star that lies on the → rotation axis of the Earth in the north hemisphere. The → Pole Star is not, in the long term, permanently fixed to the → celestial pole. This is because of the Earth's → axial precession which gradually moves the celestial poles in the sky. It takes about 26,000 years for the precession to turn the pole a full circuit. Currently the North Pole Star is → Polaris, which will continue to mark the north celestial pole for several more centuries. But, around 4,000 B.C. → Gamma Cephei will become the North Pole Star. Around 7,500 B.C., → Alderamin will take up the role. And it will be the brilliant → Vega's (Alpha Lyrae) turn in about 12,000 years. In the past, about 3,000 B.C., → Thuban (Alpha Draconis) was the North Pole Star. Then → Kokab (Beta Ursae Majoris) became the Pole Star from 1500 B.C. to 500 A.D. before leaving the task to Polaris.
Fr.: étoile du Nord
M.E., from O.E. norþerna, norðerne "northern," from norð "northern" + + -erne, suffix denoting direction
Hudari, relating to hudar, → north.
Fr.: Croix du Nord
An arrangement of stars in the form of a cross in the constellation → Cygnus.
Fr.: hémisphère nord
Fr.: nord vrai
The geographic north defined by the rotational pole of the Earth, as opposed to magnetic north defined by the geomagnetic north pole.