Thank for the mail

I am putting this mail ( after fromatting ) on our notice board

arvind

> Hi friends
>
> This is to appear in the magazine 'Dream 2047' publihsed by Vigyan
> prasr (www.vigyanprasar.gov.in)
> T V Venkateswaran
> Scientist D, Vigyan Prasar
> New Delhi
>
> Why Poor Pluto is no longer a Planet?
>
> It is just about 75 years since the discovery of Pluto; hitherto cute
> little baby planet of our solar system. With the raising of quite a
> few yellow cards in Prague, on August 24th, 2006, by 3000 and odd
> astronomers, Pluto was demoted from full-fledged planet to "dwarf
> planet." Moreover, under the revised classification, the object 2003
> UB313 which in many ways precipitated this final debate, sometimes
> called Xena, and much touted as the "10th planet, becomes the largest
> known dwarf planet. Indeed it is an irony that Pluto was a `planet'
> when the New Horizon space mission was launched in January 2006; but
> will no longer be: as it would reach Pluto-Charon in 2015.
>
> Not the first time
>
> Demotion of stellar bodies from the initial status assigned to it is
> not new to astronomy; or for that matter science. In fact when
> Galileo Galilee famously turned his telescope towards the heaven he
> was blessed with the enchanting sight of rings of Saturn, mountains
> on the moon-landscape and extraordinary sight of `stars' rotating
> about the planet Jupiter. Yes, indeed Galileo unhesitatingly asserted
> that "that there are three stars in the heavens moving about Jupiter,
> as Venus and Mercury around the Sun" and named them
> initially "medicean stars", in honour of Medic family who provided
> patronage to him during his years of trial and tribulations. However
> they were subsequently reclassified as "medicean planets"; for the
> naming them, as `stars' were deemed inappropriate. In those
> days `moon' was the proper name for the natural satellite of Earth
> and many other satellites of planets such as Rhea of Saturn were also
> called as `planets'. It was only around 1700s that astronomers
> commenced the practice of calling the satellites of planets
> as `moons'.
>
> 1781 March 13, William Herschel along with his sister Caroline
> discovered the planet Uranus. After careful study to rule out the
> possibility that this object could be comet, Herschel concluded that
> he has indeed discovered a `new' planet; a planet about which no
> scared text had any inkling. Obviously such momentous discovery
> inspired many other astronomers to search the skies for other planets
> that may be lurking around.
>
> Meanwhile, Johann Elert Bode, a German astronomer observed that, if
> you divide the distance from the Sun to Saturn into 100 lengths,
> then; Mercury is at 4 lengths; Venus is at 7 lengths (4+3); Earth is
> at 10 lengths (4+6) ; Mars is at 16 lengths (4+12) ; Nothing was seen
> at 28 lengths (4+24) ; Jupiter is at 52 lengths (4+48) ; Saturn is at
> 100 lengths (4+96). Discovery of Uranus too seemed to provide
> credence to this claim; as per the above rule the next planet beyond
> Saturn was to be at 196 (4+192); although Uranus was actually at 192
> lengths. It was so near, it was thought to verify the law. Encouraged
> by this, in 1800 Hungarian Baron, Franz Xavier von Zach, set up a
> group of astronomers called the Celestial Police, to find
> the `missing planet'. They divided the Zodiac into zones and
> allocated different areas to different astronomers in the group.
>
> The Lady luck had a different plan; she smiled on Rev Father Giuseppe
> Piazzi, an Italian Astronomer. Piazzi was compiling a star catalogue
> at Palermo Observatory in Sicily. He accidentally discovered
> a `planet' between the orbits of Mars and Jupiter on January 1, 1801
> and named it after Sicilian God of harvest `Ceres'. Thus at the
> beginning of the 19th century there were 8 planets, including Ceres
> and Uranus. However Zach's Celestial Police was not in vain, Heinrich
> Olbers, a member of the Celestial Police discovered Pallas, which too
> was in the same orbital area of Ceres, on March 28th 1802. Karl
> Harding, another member of the Celestial Police, found Juno during
> September 1804. Heinrich Olbers discovered Vesta in March 1807. All
> these were classified as Planets, and the number of planets rose to
> 11 including Vesta. However there was something fishy in the
> discoveries, all these `planets' seemed to occupy the same orbital
> area as that of Ceres.
>
> Things appeared to cool off; the fifth planet in the same orbital
> area Astraea was discovered only in 1845, nearly 39 years after the
> discovery of Vesta. However, soon the floodgate of discovery of
> planets burst at its seam in 1847 with the discovery of three new
> asteroids. By the end of 1851 there were 15 asteroids, although
> astronomers sere disquieted, they braved themselves and still listed
> all of them as planets- solar system then consisted of 23 planets
> including Neptune (discovered in 1845), Uranus and 15 `planets' in
> the orbital region of Ceres. By 1668 more than 100 stellar objects
> were discovered in that region. Surely things were unseemly; in fact
> due their starlike appearance, Herschel had declared even as early as
> 1802 that "from their asteroidal appearance, I shall take my name,
> and call them Asteroids; reserving for myself, however, the liberty
> of changing that name, if another, more expressive of their nature
> should occur." Astronomers who had not heeded to this perceptive
> counsel at that time had to but agree; at one go 15 `planets' were
> reclassified as `minor planets' or `asteroids' around 1850s.
>
> Discovery of Pluto
>
> Discovery of Pluto is intimately linked to that of Neptune. Once
> Uranus was discovered astronomers observed that there was
> perturbations in its path; as if there is another massive body beyond
> Uranus giving it a jab. Convinced that there is a planet beyond
> Uranus search began; Adams in England and Levarrier in France
> spearheaded the search. They calculated the possible position of
> Neptune and with much drama the planet indeed was discovered by Galle
> and D'Arrest of Berlin Observatory on September 23, 1845.
>
> Neptune accounted for the observed perturbations in the path of
> Uranus, nonetheless Neptune itself showed perturbations as if being
> shoved around by a planet beyond it. `Ah' said astronomers `lets go
> for the Planet X'. Nonetheless it was soon evident to astronomers
> that treading the same path will not lead them to the Planet X.
> Calculations after calculations were made and yet the elusive planet
> was not to be seen. Where calculations and prediction failed;
> perseverance triumphed. With the invention of photography it was
> possible to recorded the position of stellar objects weeks apart and
> compare them. Clyde Tombaugh in fact did exactly that; and on 13th
> March 1930 Lowell Observatory announced the discovery of the ninth
> planet of the Solar system thereby bringing an end a search, which
> went on for about 25 years. When Tombaugh discovered Pluto
> astronomers welcomed it as the long sought "Planet X", which would
> account for residual perturbations in the orbit of Neptune. In a
> curious twist to the tale those perturbations proved to be illusory,
> and the discovery of Pluto was fortuitous.
>
> Pluto an odd ball
>
> Right from the day of its discovery Pluto has been an odd ball.
> Pluto's orbit deviates significantly from a perfect circle while the
> major planets have quasi-circular orbits. It is so elongated that it
> crosses the orbit of Neptune. Due to this, from 1979 to 1999 for
> twenty years in fact Pluto was rather closer than Neptune. Pluto's
> orbit is also considerably tilted – whooping 17 degrees- compared to
> the orbits of the major planets. At the time of its discovery Pluto
> was estimated to be the size of Earth; later downgraded to size of
> Mars. Further, in 1978, Pluto's companion, Charon was discovered.
> Chaorn was estimated to be half its size; earlier the size of Pluto
> was estimated by including the size of Charon as it was not possible
> to resolve them separately. This led to further downsizing of Pluto;
> now we know that Pluto is much smaller than the major planets- just
> about 2320 km across- smaller than seven moon of Solar system
> including our moon. Its mass is only 0.2% of the Earth's mass, and
> 100,000 times less than the mass of Jupiter. Pluto rotates in the
> opposite direction from most of the other planets. Pluto has been an
> irritant as a planet for astronomers quite long; aastronomers were
> indeed puzzled what to make of this small, frigid world.
>
> Why now?
>
> 2005 witnessed the 75th anniversary celebrations of the discovery of
> Pluto; Clyde Tombaugh was hailed. Nevertheless even before the din
> and dust settled down poor Pluto has been striped of its Planethood.
> As a matter of fact, even at an earlier occasion astronomers had
> suggested that Pluto does not really belong to the category of
> Planets. In 1999, an inadvertent suggestion, that Pluto may be termed
> the 10000th minor planet giving it "dual citizenship" of sorts as
> both a major and a minor planet was made by Brian Marsden of the
> Minor Planet Center of IAU. This stormed into a major debate that
> spread into streets; passionate editorials were written and email
> campaign was conducted fearing that Pluto might be "demoted" to non-
> planet status, in particular in USA. Taken aback, putting rest the
> rumors IAU then emphatically declared that there were no plans to
> change Pluto's planetary status.
>
> However, for astronomers it was evident for long that the fate of
> Pluto was sealed; sooner or later it will lose its status as Planet.
> The need for a strict definition was deemed necessary after new
> telescope technologies, especially Hubble Telescope and use of
> Computer technologies to compare photographs, began to reveal far-off
> objects in the region of Pluto. The first Kuiper belt object (KBOs)
> 1992 QB1 was discovered in 1992. 2001 KX76 an icy, reddish world over
> a thousand kilometres across was soon discovered. Two is a company,
> but surely three is a crowd; soon many more objects were discovered
> in the Kuiper Belt area going around the sun in the region of Pluto.
> In 2002, Quaoar (1280 km diameter) was discovered, making it a bit
> more than half the size of Pluto. Another discovery, Orcus, is
> probably even larger. In 2004 Sedna, an extremely distant object
> beyond the Kuiper belt was discovered with estimated 1800 km
> diameter, close to Pluto's 2320 km. As of now more than 783 objects
> have been discovered in the same region as that of Pluto. The
> proverbial last straw on the camel was the discovery of Trans-
> Neptunian object 2003 UB313 (popularly called as Xena). Announced on
> July 29, 2005 it rekindled the debate as to whether to classify Pluto
> as a planet or not. It is estimated to be at least as large as Pluto;
> and is the largest object yet discovered in the solar system since
> Neptune in 1846 and has caused some to refer to it as the "10th
> planet" of the solar system. It was clear that Pluto is embedded in
> a vast swarm of small bodies, just like the asteroid Ceres in the
> asteroid belt between Mars and Jupiter. Pluto has many friends
> orbiting nearby and at least one of them is larger than Pluto. There
> have been another important developments in our knowledge
> of "planetary systems" in the last decade or so: the discovery of
> celestial bodies orbiting stars – exoplanets- other than the sun.
> These recent developments make it pressing to arrive at a proper
> definition for the word "planet".
>
> What is in a name?
>
> In popular culture, whenever something new is discovered in the outer
> solar system, the first question asked is "Is it bigger than Pluto?"
> When it is understood to be only half the size of Pluto (2002
> discovery of Quaoar) or maybe three forth the size of Pluto (2004
> discovery of Sedna) there is a little disappointment and it is said
> that " Ok , well, it is not a planet'. But when it is said "Well
> rather this one bigger than Pluto" (2005 discovery of 2003 UB313) it
> is remarked "Hurrah! The 10th planet has been found!" In popular
> imagination only objects larger than Pluto are to be called planets.
> However from the point of view of science it is arbitrary and
> whimsical. For the uninitiated sure enough world of science appears
> to be weird; Bats are able to fly but it is not a bird; Whales waddle
> in ocean yet they are not fish but are mammals. Penguins can swim and
> toddle but can not fly, yet it is a bird! However such
> classifications allude to deep relationships; Penguins are closely
> related to birds from the point of view of evolution; and bats
> possesses organs specific to mammals. If Pluto is included as a
> planet, we have no physical basis for excluding UB313, dozens of
> other large spherical KBOs, and Ceres. The term "planet" would then
> lose any taxonomic utility. But an important function of scientific
> nomenclature is to reflect natural relationships, not to obscure them.
>
> IAU's Resolution
>
> International Astronomical Union (IAU) an international scientific
> body established in 1919, currently with 9000 members, organizes once
> in three year a general body to take stock of the development in
> Astronomy. XXVI th Congress held at Prague Czech Republic between
> August 14-25, 2006 adopted a resolution given first-ever scientific
> definition to `Planet' by a vote of the International Astronomical
> Union.
>
> In light of our improved understanding of the solar system
> astronomers have revised their classification. An initial proposal
> put forward criteria that kept Pluto's status and brought the club to
> 12 - adding 2003 UB313, the asteroid Ceres, and Pluto's largest moon,
> Charon to the nine planets. But this scheme met with considerable
> opposition from astronomers at the assembly who felt that very soon
> many members of the KBOs could lay claim to membership of planetary
> club under this classification. Revised resolution that was adopted
> defines three distinct classes of objects in the solar system:
> planets, dwarf planets, and small solar-system bodies. There are 8
> planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter,
> Saturn, Uranus, and Neptune. A dwarf planet is not a planet.
>
> The resolution adopted states "A "planet" is a celestial body that
> (a) is in orbit around the Sun, (b) has sufficient mass for its self-
> gravity to overcome rigid body forces so that it assumes a
> hydrostatic equilibrium (nearly round) shape, and (c) has cleared the
> neighbourhood around its orbit. Further it clarifies that "A "dwarf
> planet" is a celestial body that (a) is in orbit around the Sun, (b)
> has sufficient mass for its self-gravity to overcome rigid body
> forces so that it assumes a hydrostatic equilibrium (nearly round)
> shape, (c) has not cleared the neighbourhood around its orbit, and
> (d) is not a satellite. In addition the resolution states that "All
> other objects except satellites orbiting the Sun shall be referred to
> collectively as "Small Solar-System Bodies"."
>
> That the planet should go around the Sun is but natural, so is the
> second criteria, which essentially mean that the object should be
> massive enough to be crushed on its own weight into a spherical shape
> (or near spherical shape). This too is comprehensible; you do not
> want any and every lump of rock going around the sun to be
> termed `planet'. But how do we make sense of the third commandment?
>
> The Third Commandment
>
> The third norm is linked to the dynamics of planet formation. Solar
> system includes several distinct populations; the planets,
> satellites, asteroid belt, Kuiper Belt, Oort Cloud, etc. These
> distinct populations reflect different pathways in the evolution of
> the solar nebula, which in the first place coalesced in to central
> star (Sun) and solar system objects. In Safronov' s model of
> planetesimals and planetary evolution, a planet is an end product of
> disk accretion around a primary star that sweeps up or scatters most
> of the mass from its orbital zone in the accretion disk around a
> central star. Further dynamics of planet formation is linked to the
> degree to which a body dominates the other masses that share its
> orbital zone. The disk evolution in a mature systems tend to produce
> a small number of relatively large bodies (planets) in non-
> intersecting or resonant orbits, which prevent collisions between
> them. According to this model the inner region of the accretion disc
> coalesced into terrestrial planets; outer regions formed into gas
> giants. On the other hand objects like Ceres and Pluto remain in an
> arrested state of development, unlike mature planets and hence are
> rightly classified as `dwarf planets'.
>
> Further in course the evolution of solar system planets come to
> dominate their orbital region such that it is more massive than the
> total mass of all of the other bodies in a similar orbit. For
> example, the planet Neptune has 8600 times the mass of Pluto, the
> largest body that crosses its orbit. Likewise, the planet Earth has 2
> x 108 times the mass of the asteroid (1036) Ganymed, the largest body
> that crosses its orbit. The major planets have accumulated, captured,
> or ejected all the mass in their immediate proximity. They are the
> dominant bodies in their regions of space. In contrast, the asteroids
> and KBOs are members of populations with a shared orbital space, in
> which no member so dominates the others by mass. The two largest
> asteroids, Ceres and Pallas, differ in mass by a factor of about 4
> and the largest known KBO (UB313) has only about twice the mass of
> Pluto. Our solar system has no intermediate cases between solitary
> bodies (planets) and members of populations, defined in this way.
>
> Asteroids and comets, including KBOs, differ from planets in that
> they can collide with each other and with planets. It is postulated
> that about 3.8 billion years ago, after a period known as heavy
> bombardment, most of the planetesimals, which did not coalesce into
> planets within the solar system had either been ejected from the
> Solar system entirely, into distant eccentric orbits such as the Oort
> cloud, or had collided with larger objects due to the regular
> gravitational nudges from the Jovian planets. Debris leftover from
> this evolutionary phase of solar system remains as asteroid belt, the
> Kuiper Belt, and the Oort cloud. Moons such as Phobos, Deimos,
> Triton, and many of the small high-inclination moons of the Jovian
> planets are considered to be `captured' planetesimals.
>
> Moreover Neptune totally dominates Pluto's region of the Kuiper belt.
> While much of the material in the Kuiper belt has indeed been tossed
> aside or accumulated by Neptune, a very special region has actually
> been captured by Neptune. We now know that Neptune formed much closer
> to the sun than where it was today, and, as Neptune moved out, it
> pushed objects in this special region out with it while forcing them
> into a peculation orbit where they orbit the sun precisely twice for
> every three orbits of Neptune. Pluto is the largest of this class,
> and it and the others only exist where they do because of the
> dominance of Neptune. Same is the case with so called `Trojan
> asteroids' of Jupiter, they are swept by Jupiter's gravity to remain
> 60 degrees ahead or 60 degrees behind the planet, in what are known
> as the Lagrange points.
>
> In fact in the light of our modern understanding conventional list
> of "nine planets"- four terrestrial planets, four giant planets, and
> Pluto – has lost any scientific rationale, and is now merely
> historical. While it is quite understandable that in 1930 astronomers
> felt that Pluto was an exceptional object and decided to call it a
> planet; on the other hand majority of astronomers today recognize
> Pluto as a large member of a vast population of small bodies beyond
> Neptune.
>
> Science is all about recognizing that earlier ideas may have been
> wrong. For a long time biologists thought that all microbes were
> germs causing diseases in humans. Today we are more enlightened we
> are aware that some bacteria are beneficial; moreover we have
> realized that there is another class of microbe- viruses. Sure enough
> we have changed our ideas about which bug was what. We are all better
> off now as the new classification has clarified meaning and has
> allowed researchers and health professionals go about their jobs
> better. It is no wonder that replying to a question as to how Clyde
> Tombaugh would feel about the Pluto's demotion, his wife Patricia
> Tombaugh stated, "He was a scientist. He would understand they had a
> real problem when they start finding several of these things flying
> around the place"
>
> BOX
> Victor Safronov model of how planets evolved
>
> The model proposed by Victor Safronov (1917-1999), Soviet astronomer
> for evolution of planets around a star from an initial interstellar
> cloud informs our modern understanding of the dynamics of planet
> formation. His theory was in contrast to then prevailing theory that
> conceived planets to be end product of a process of gravitational
> fragmentation of the proto-planetary disc directly into planets.
> Safronov theorized that planets form from aggregation of countless
> smaller bodies: dust grains and debris left over in the solar system
> after formation of the Sun. Initially the dust or small grain move
> about due to Brownian motion, or turbulent motions in the gas to
> cause the collisions that can lead to coalescing. However, when the
> bodies reach sizes of approximately one kilometer, then they can
> attract each other directly through their mutual gravity, aiding
> further growth into moon-sized protoplanets enormously. Many such
> planetesimals are indeed formed in the accretion disc, many
> eventually break apart during violent collisions, but a few of the
> largest planetesimals survive such encounters and continue to grow
> into protoplanets and later planets. In this model Planets are end
> product of secondary accretion in a disk around a primary star.
> Planets in this sense occur only in highly evolved (old) systems,
> which have reached the final cleanup phase of accretion, with the
> major bodies in stable non-intersecting orbits. In this model Planets
> are the solitary bodies that prevail in the creative-destructive
> evolution of a disk, and are dynamically distinct from the
> populations of leftover debris - mainly asteroids and comets.
>
>
>
>
>
> --
> This message has been scanned for viruses and
> dangerous content by OpenProtect(http://www.openprotect.com), and is
> believed to be clean.
>
>


--
This message has been scanned for viruses and
dangerous content by OpenProtect(http://www.openprotect.com), and is
believed to be clean.