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41-580: Falgun was named for the nakshatra ( lunar mansion ) Uttara phalguni , in the vicinity of which the full moon appears at that time of the year. It marks the arrival of spring , the sixth and final season in Bangladesh, West Bengal, Assam , and Nepal . Falgun falls between mid-February and mid-March on the Gregorian calendar. This Bangladesh -related article is a stub . You can help Misplaced Pages by expanding it . This Nepal -related article

82-695: A nakshatra simply is a constellation . Every nakshatra is divided into four padas ( lit. "steps") related to the Char Dham , a set of four pilgrimage sites in India. The starting point for the nakshatras according to the Vedas is "Krittika" (it has been argued because the Pleiades may have started the year at the time the Vedas were compiled, presumably at the vernal equinox), but, in more recent compilations,

123-499: A particular equinox, that is, the equinox of a particular date, known as an epoch ; the coordinates are referred to the direction of the equinox at that date. For instance, the Astronomical Almanac lists the heliocentric position of Mars at 0h Terrestrial Time , 4 January 2010 as: longitude 118°09′15.8″, latitude +1°43′16.7″, true heliocentric distance 1.6302454 AU, mean equinox and ecliptic of date. This specifies

164-529: A relatively short time span, perhaps several centuries. J. Laskar computed an expression to order T good to 0.04″ /1000 years over 10,000 years. All of these expressions are for the mean obliquity, that is, without the nutation of the equator included. The true or instantaneous obliquity includes the nutation. Most of the major bodies of the Solar System orbit the Sun in nearly the same plane. This

205-545: Is a stub . You can help Misplaced Pages by expanding it . Nakshatra Nakshatra ( Sanskrit : नक्षत्रम् , romanized :  Nakṣatram ) is the term for Lunar mansion in Hindu astrology and Buddhist astrology. A nakshatra is one of 27 (sometimes also 28) sectors along the ecliptic. Their names are related to a prominent star or asterisms in or near the respective sectors. In essence (in Western astronomical terms),

246-530: Is a simplification. Periodic motions of the Moon and apparent periodic motions of the Sun (actually of Earth in its orbit) cause short-term small-amplitude periodic oscillations of Earth's axis, and hence the celestial equator, known as nutation . This adds a periodic component to the position of the equinoxes; the positions of the celestial equator and (March) equinox with fully updated precession and nutation are called

287-478: Is also used occasionally; the x -axis is directed toward the March equinox, the y -axis 90° to the east, and the z -axis toward the north ecliptic pole; the astronomical unit is the unit of measure. Symbols for ecliptic coordinates are somewhat standardized; see the table. Ecliptic coordinates are convenient for specifying positions of Solar System objects, as most of the planets' orbits have small inclinations to

328-490: Is divided into 12 signs of 30° longitude, each of which approximates the Sun's motion in one month. In ancient times, the signs corresponded roughly to 12 of the constellations that straddle the ecliptic. These signs are sometimes still used in modern terminology. The " First Point of Aries " was named when the March equinox Sun was actually in the constellation Aries ; it has since moved into Pisces because of precession of

369-471: Is likely due to the way in which the Solar System formed from a protoplanetary disk . Probably the closest current representation of the disk is known as the invariable plane of the Solar System . Earth's orbit, and hence, the ecliptic, is inclined a little more than 1° to the invariable plane, Jupiter's orbit is within a little more than ½° of it, and the other major planets are all within about 6°. Because of this, most Solar System bodies appear very close to

410-534: Is near an ascending or descending node at the same time it is at conjunction ( new ) or opposition ( full ). The ecliptic is so named because the ancients noted that eclipses only occur when the Moon is crossing it. The exact instants of equinoxes and solstices are the times when the apparent ecliptic longitude (including the effects of aberration and nutation ) of the Sun is 0°, 90°, 180°, and 270°. Because of perturbations of Earth's orbit and anomalies of

451-866: Is one of the five elements of a Pañcāṅga . The other four elements: 1   citrā́ṇi sākáṃ diví rocanā́ni sarīsr̥pā́ṇi bhúvane javā́ni turmíśaṃ sumatím ichámāno áhāni gīrbhíḥ saparyāmi nā́kam 2   suhávam agne kŕ̥ttikā róhiṇī cā́stu bhadráṃ mr̥gáśiraḥ śám ārdrā́ púnarvasū sūnŕ̥tā cā́ru púṣyo bhānúr āśleṣā́ áyanaṃ maghā́ me 3   púṇyaṃ pū́rvā phálgunyau cā́tra hástaś citrā́ śivā́ svātí sukhó me astu rā́dhe viśā́khe suhávānurādhā́ jyéṣṭhā sunákṣatram áriṣṭa mū́lam 4   ánnaṃ pū́rvā rāsatāṃ me aṣādhā́ ū́rjaṃ devy úttarā ā́ vahantu abhijín me rāsatāṃ púṇyam evá śrávaṇaḥ śráviṣṭhāḥ kurvatāṃ supuṣṭím 5   ā́ me mahác chatábhiṣag várīya ā́ me dvayā́ próṣṭhapadā suśárma ā́ revátī cāśvayújau bhágaṃ ma ā́ me rayíṃ bháraṇya ā́ vahantu   Ecliptic The ecliptic or ecliptic plane

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492-411: Is projected outward to the celestial sphere , forming the celestial equator , it crosses the ecliptic at two points known as the equinoxes . The Sun, in its apparent motion along the ecliptic, crosses the celestial equator at these points, one from south to north, the other from north to south. The crossing from south to north is known as the March equinox , also known as the first point of Aries and

533-405: Is the orbital plane of Earth around the Sun . From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic against the background of stars . The ecliptic is an important reference plane and is the basis of the ecliptic coordinate system . The ecliptic is the apparent path of the Sun throughout

574-515: The ascending node of the ecliptic on the celestial equator. The crossing from north to south is the September equinox or descending node . The orientation of Earth's axis and equator are not fixed in space, but rotate about the poles of the ecliptic with a period of about 26,000 years, a process known as lunisolar precession , as it is due mostly to the gravitational effect of the Moon and Sun on Earth's equatorial bulge . Likewise,

615-407: The mean equinox of 4 January 2010 0h TT as above , without the addition of nutation. Because the orbit of the Moon is inclined only about 5.145° to the ecliptic and the Sun is always very near the ecliptic, eclipses always occur on or near it. Because of the inclination of the Moon's orbit, eclipses do not occur at every conjunction and opposition of the Sun and Moon, but only when the Moon

656-448: The true equator and equinox ; the positions without nutation are the mean equator and equinox . Obliquity of the ecliptic is the term used by astronomers for the inclination of Earth's equator with respect to the ecliptic, or of Earth's rotation axis to a perpendicular to the ecliptic. It is about 23.4° and is currently decreasing 0.013 degrees (47 arcseconds) per hundred years because of planetary perturbations. The angular value of

697-520: The " start of Aries ". The first astronomical text that lists them is the Vedanga Jyotisha . In classical Hindu scriptures ( Mahabharata , Harivamsa ), the creation of the asterisms is attributed to Daksha . The Nakshatras are personified as daughters of Daksha and as wives of Chandra , the god of the Moon. When Chandra neglected his 26 other wives in favour of Rohini , his father-in-law cursed him with leprosy and proclaimed that

738-425: The Moon travels past the specific star fields called nakshatras. Hence, the stars are more like numbers on a clock, through which the hands of time (the moon) pass. This concept is described by J. Mercay (2012) in connection with Surya Siddhanta . In Hindu astronomy, there was an older tradition of 28 Nakshatras which were used as celestial markers in the heavens. When these were mapped into equal divisions of

779-462: The Moon would wax and wane each month. The Nakshatras are also alternatively described as the daughters of Kashyapa . In the Atharvaveda (Shaunakiya recension, hymn 19.7) a list of 27 stars or asterisms is given, many of them corresponding to the later nakshatras: This 27-day cycle has been taken to mean a particular group of stars. This has to do with the periodicity with which

820-399: The Sun about four minutes later each day than it would if Earth did not orbit; a day on Earth is therefore 24 hours long rather than the approximately 23-hour 56-minute sidereal day . Again, this is a simplification, based on a hypothetical Earth that orbits at uniform speed around the Sun. The actual speed with which Earth orbits the Sun varies slightly during the year, so the speed with which

861-504: The Sun seems to move along the ecliptic also varies. For example, the Sun is north of the celestial equator for about 185 days of each year, and south of it for about 180 days. The variation of orbital speed accounts for part of the equation of time . Because of the movement of Earth around the Earth–Moon center of mass , the apparent path of the Sun wobbles slightly, with a period of about one month . Because of further perturbations by

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902-625: The ancient Indian calendar with Vedic months of 30 days and a daily movement of the Moon of 13 degrees, this early designation of a sidereal month of 831 Muhurtas or 27.7 days is very precise. Later some Indian savants dropped the Nakshatra named Abhijit to reduce the number of divisions to 27, but the Chinese retained all of their original 28 lunar mansions. These were grouped into four equal quarters which would have been fundamentally disrupted if it had been decided to reduce

943-461: The calendar , the dates of these are not fixed. The ecliptic currently passes through the following thirteen constellations : There are twelve constellations that are not on the ecliptic, but are close enough that the Moon and planets can occasionally appear in them. The ecliptic forms the center of the zodiac , a celestial belt about 20° wide in latitude through which the Sun, Moon, and planets always appear to move. Traditionally, this region

984-410: The celestial equator. Spherical coordinates , known as ecliptic longitude and latitude or celestial longitude and latitude, are used to specify positions of bodies on the celestial sphere with respect to the ecliptic. Longitude is measured positively eastward 0° to 360° along the ecliptic from the March equinox, the same direction in which the Sun appears to move. Latitude is measured perpendicular to

1025-460: The coordinates of the twenty-seven Nakshatras. It is noted above that with the older tradition of 28 Nakshatras each equal segment would subtend 12.85 degrees or 12° 51′. But the 28 Nakshatra were chosen at a time when the Vedic month was recognised as having exactly 30 days. In India and China the original 28 lunar mansions were not equal. Weixing Nui provides a list of

1066-442: The corresponding regions of sky, per Basham (1954). Each of the 27 Nakshatras cover 13° 20’ of the ecliptic each. Each Nakshatra is also divided into quarters or padas of 3° 20’, and the below table lists the appropriate starting sound to name the child. The 27 nakshatras, each with 4 padas, give 108, which is the number of beads in a japa mala, representing all the elements (ansh) of Vishnu: Nakshatra

1107-432: The course of a year . Because Earth takes one year to orbit the Sun, the apparent position of the Sun takes one year to make a complete circuit of the ecliptic. With slightly more than 365 days in one year, the Sun moves a little less than 1° eastward every day. This small difference in the Sun's position against the stars causes any particular spot on Earth's surface to catch up with (and stand directly north or south of)

1148-406: The ecliptic in the sky. The invariable plane is defined by the angular momentum of the entire Solar System, essentially the vector sum of all of the orbital and rotational angular momenta of all the bodies of the system; more than 60% of the total comes from the orbit of Jupiter. That sum requires precise knowledge of every object in the system, making it a somewhat uncertain value. Because of

1189-410: The ecliptic itself is not fixed. The gravitational perturbations of the other bodies of the Solar System cause a much smaller motion of the plane of Earth's orbit, and hence of the ecliptic, known as planetary precession . The combined action of these two motions is called general precession , and changes the position of the equinoxes by about 50 arc seconds (about 0.014°) per year. Once again, this

1230-569: The ecliptic, a division of 27 portions was adopted since that resulted in a clearer definition of each portion (i.e. segment) subtending 13° 20′ (as opposed to 12°  51 + 3 ⁄ 7 ′ in the case of 28 segments). In the process, the Nakshatra Abhijit was left out without a portion. However, the Abhijit nakshatra becomes important while deciding on the timing of an auspicious event. The Surya Siddhantha concisely specifies

1271-412: The ecliptic, and therefore always appear relatively close to it on the sky. Because Earth's orbit, and hence the ecliptic, moves very little, it is a relatively fixed reference with respect to the stars. Because of the precessional motion of the equinox , the ecliptic coordinates of objects on the celestial sphere are continuously changing. Specifying a position in ecliptic coordinates requires specifying

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1312-436: The ecliptic, to +90° northward or −90° southward to the poles of the ecliptic, the ecliptic itself being 0° latitude. For a complete spherical position, a distance parameter is also necessary. Different distance units are used for different objects. Within the Solar System, astronomical units are used, and for objects near Earth , Earth radii or kilometers are used. A corresponding right-handed rectangular coordinate system

1353-514: The extent of the original 28 Nakshatras expressed in Muhurtas (with one Muhurta = 48 minutes of arc). Hindu texts note there were 16 Nakshatras of 30 Muhurtas, 6 of 45 Muhurtas, 5 of 15 Muhurtas and one of 6 Muhurtas. The 28 mansions of the 360° lunar zodiac total 831 Muhurtas or 27.7 days. This is sometimes described as an inaccurate estimate of our modern sidereal period of 27.3 days, but using

1394-476: The number of divisions to 27. Irrespective of the reason why ancient early Indian astronomers followed a Vedic calendar of exactly 12 months of 30 days it was this calendar and not a modern calendar of 365 days that they used for the astronomical calculations for the number of days taken for the Moon to complete one sidereal cycle of 360°. This is why initially they named 28 Nakshatras on their lunar zodiac. The following list of nakshatras gives

1435-441: The obliquity is found by observation of the motions of Earth and other planets over many years. Astronomers produce new fundamental ephemerides as the accuracy of observation improves and as the understanding of the dynamics increases, and from these ephemerides various astronomical values, including the obliquity, are derived. Until 1983 the obliquity for any date was calculated from work of Newcomb , who analyzed positions of

1476-462: The other planets of the Solar System , the Earth–Moon barycenter wobbles slightly around a mean position in a complex fashion. Because Earth's rotational axis is not perpendicular to its orbital plane , Earth's equatorial plane is not coplanar with the ecliptic plane, but is inclined to it by an angle of about 23.4°, which is known as the obliquity of the ecliptic . If the equator

1517-515: The planets until about 1895: ε = 23°27′08.26″ − 46.845″ T − 0.0059″ T + 0.00181″ T where ε is the obliquity and T is tropical centuries from B1900.0 to the date in question. From 1984, the Jet Propulsion Laboratory's DE series of computer-generated ephemerides took over as the fundamental ephemeris of the Astronomical Almanac . Obliquity based on DE200, which analyzed observations from 1911 to 1979,

1558-468: The sky's distant background. The ecliptic forms one of the two fundamental planes used as reference for positions on the celestial sphere, the other being the celestial equator . Perpendicular to the ecliptic are the ecliptic poles , the north ecliptic pole being the pole north of the equator. Of the two fundamental planes, the ecliptic is closer to unmoving against the background stars, its motion due to planetary precession being roughly 1/100 that of

1599-454: The start of the nakshatras list is the point on the ecliptic directly opposite to the star Spica , called Chitrā in Sanskrit . This translates to Ashwinī, a part of the modern constellation of Aries. These compilations, therefore may have been compiled during the centuries when the sun was passing through Aries at the time of the vernal equinox. This version may have been called Meshādi or

1640-399: The uncertainty regarding the exact location of the invariable plane, and because the ecliptic is well defined by the apparent motion of the Sun, the ecliptic is used as the reference plane of the Solar System both for precision and convenience. The only drawback of using the ecliptic instead of the invariable plane is that over geologic time scales, it will move against fixed reference points in

1681-445: Was calculated: ε = 23°26′21.45″ − 46.815″ T − 0.0006″ T + 0.00181″ T where hereafter T is Julian centuries from J2000.0 . JPL's fundamental ephemerides have been continually updated. The Astronomical Almanac for 2010 specifies: ε = 23°26′21.406″ − 46.836769″ T − 0.0001831″ T + 0.00200340″ T − 0.576×10 ″ T − 4.34×10 ″ T These expressions for the obliquity are intended for high precision over

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