එරිස් ' නම් වාමන ග්රහයාගේ (ඩ්වෝප් ප්ලැනට්) සොයාගැනීම
{Infobox Planet | bgcolour = #FFA0FF | name = Eris | symbol= | image = 
| caption = Eris (centre) and Dysnomia (left of centre).
Hubble Space Telescope | discovery = yes | discoverer = M. E. Brown,
C. A. Trujillo,
D. L. Rabinowitz[1] | discovered = January 5, 2005[2][g] | mp_name = 136199 Eris | note = yes | alt_names = 2003 UB313[3] | named_after = Eris | mp_category = dwarf planet,
TNO,
plutoid,
and SDO[4][5] | orbit_ref = [3] | epoch = March 6, 2006
(JD 2453800.5)[6] | aphelion = 97.56 AU
14.60 × 109 km | perihelion = 37.77 AU
5.65 × 109 km | semimajor = 67.67 AU
10.12 × 109 km | eccentricity = 0.441 77 | period = 203,600 days
557 years | avg_speed = 3.436 km/s | mean_anomaly = 197.634 27° | inclination = 44.187° | asc_node = 35.869 6° | arg_peri = 151.430 5° | satellites=Dysnomia | physical_characteristics = yes | mean_radius = 1300සැකිල්ල:± km (2007)[7]
Preliminary: ≤1170 (2010)[8] | mass = (1.67±0.02) × 1022 kg[9]
0.0028 Earths
0.23 Moons | surface_area = 78,500,000 sq km (48,777,638.6 sq mi) | density= 2.25–2.5 g/cm3[10] | surface_grav = ~0.8 m/s2 | sidereal_day = 25.9 ± 8 hr[3] | albedo = 0.86 ± 0.07 | temperatures = yes | temp_name1 = (approx) | min_temp_1 = 30 K | mean_temp_1 = 42.5 K | max_temp_1 = 55 K | spectral_type = B-V=0.78, V-R=0.45[11] | magnitude = 18.7[12] | abs_magnitude = −1.19 ± 0.3[3] | angular_size = 40 milli-arcsec[13] | pronounce = /ˈɪərɪs/, or /ˈɛrɪs/ as in Greek Έρις [a] | adjectives = Eridian }} Eris, formal designation 136199 Eris, is the most massive known dwarf planet[i] in the Solar System and the ninth most massive body known to orbit the Sun directly. It is estimated to be approximately 2300–2400 km in diameter,[14] and 27% more massive than Pluto or about 0.27% of the Earth's mass.[9][15]
Eris was discovered in January 2005 by a Palomar Observatory-based team led by Mike Brown, and its identity was verified later that year. It is a trans-Neptunian object (TNO) and a member of a high-eccentricity population known as the scattered disc. It has one known moon, Dysnomia. As of 2011, its distance from the Sun is 96.6 AU,[12] roughly three times that of Pluto. With the exception of some comets, Eris and Dysnomia are currently the most distant known natural objects in the Solar System.[2][h]
Because Eris appeared to be larger than Pluto, its discoverers[16] and NASA initially described it as the Solar System’s tenth planet. This, along with the prospect of other similarly sized objects being discovered in the future, motivated the International Astronomical Union (IAU) to define the term planet for the first time. Under the IAU definition approved on August 24, 2006, Eris is a "dwarf planet" along with Pluto, Ceres, Haumea and Makemake.[17]
In 2010, preliminary results from observations of a stellar occultation by Eris on November 6 suggested that its diameter may be only 2320 km, which would make it essentially the same size as Pluto.[18] Given the error bars in the different size estimates, it is currently uncertain whether Eris or Pluto has the larger diameter.[19] Both Pluto and Eris are estimated to have solid-body diameters of about 2330 km.[19]
පටුන |
[සංස්කරණය] Discovery
Eris was discovered by the team of Mike Brown, Chad Trujillo, and David Rabinowitz[2] on January 5, 2005, from images taken on October 21, 2003. The discovery was announced on July 29, 2005, the same day as සැකිල්ල:Dp and two days after සැකිල්ල:Dp.[20] The search team had been systematically scanning for large outer solar system bodies for several years, and had been involved in the discovery of several other large TNOs, including 50000 Quaoar, 90482 Orcus, and 90377 Sedna.
Routine observations were taken by the team on October 21, 2003, using the 1200 mm Samuel Oschin reflecting telescope at Mount Palomar Observatory, California, but the image of Eris was not discovered at that point due to its very slow motion across the sky: The team's automatic image-searching software excluded all objects moving at less than 1.5 arcseconds per hour to reduce the number of false positives returned. When Sedna was discovered, it was moving at 1.75 arcsec/h, and in light of that the team reanalyzed their old data with a lower limit on the angular motion, sorting through the previously excluded images by eye. In January 2005, the re-analysis revealed Eris' slow motion against the background stars.
Follow-up observations were then carried out to make a preliminary determination of Eris' orbit, which allowed the object's distance to be estimated. The team had planned to delay announcing their discovery until further observations allowed more accurate calculations of Eris' orbit, but brought their announcement forward when the discovery of another large TNO they had been tracking, සැකිල්ල:Dp, was announced by a different team in Spain.[2]
More observations released in October 2005 revealed that Eris had a moon, later named Dysnomia. Observations of Dysnomia's orbit permitted scientists to determine the mass of Eris, which in June 2007 they calculated to be 1.66±0.02×1022 kg, 27% greater than Pluto's.
[සංස්කරණය] Classification
Eris is classified as a plutoid, that is, a trans-Neptunian object that is also a dwarf planet.[21] Its orbital characteristics more specifically categorize it a scattered disk object (SDO), or a TNO that is believed to have been "scattered" from the Kuiper belt into more distant and unusual orbits following gravitational interactions with Neptune as the Solar System was forming. Although its high orbital inclination is unusual among the known SDOs, theoretical models suggest that objects that were originally near the inner edge of the Kuiper belt were scattered into orbits with higher inclinations than objects from the outer belt.[22] Inner-belt objects are expected to be generally more massive than outer-belt objects, and so astronomers expect to discover more large objects like Eris in high-inclination orbits, which have traditionally been neglected.
Because Eris may be larger than Pluto, it was initially described as the "tenth planet" by NASA and in media reports of its discovery.[23] In response to the uncertainty over its status, and because of ongoing debate over whether Pluto should be classified as a planet, the IAU delegated a group of astronomers to develop a sufficiently precise definition of the term planet to decide the issue. This was announced as the IAU's Definition of a Planet in the Solar System, adopted on August 24, 2006. At this time, both Eris and Pluto were classified as dwarf planets, a category distinct from the new definition of planet.[24] Brown has since stated his approval of the "dwarf planet" label.[25] The IAU subsequently added Eris to its Minor Planet Catalogue, designating it (136199) Eris.[26]
[සංස්කරණය] Name
Eris is named after the Greek goddess Eris (Greek Ἔρις), a personification of strife and discord.[27] The name was assigned on September 13, 2006, following an unusually long period in which the object was known by the provisional designation 2003 UB313, which was granted automatically by the IAU under their naming protocols for minor planets. The regular adjectival form of Eris is Eridian.
[සංස්කරණය] Xena
Due to uncertainty over whether the object would be classified as a planet or a minor planet, as different nomenclature procedures apply to these different classes of objects,[28] the decision on what to name the object had to wait until after the August 24, 2006, IAU ruling.[29] As a result, for a time the object became known to the wider public as Xena.
"Xena" was an informal name used internally by the discovery team. It was inspired by the eponymous heroine of the television series Xena: Warrior Princess. The discovery team had reportedly saved the nickname "Xena" for the first body they discovered that was larger than Pluto. According to Brown,
We chose it since it started with an X (planet "X"), it sounds mythological (OK, so it’s TV mythology, but Pluto is named after a cartoon, right?),[b] and (this part is actually true) we've been working to get more female deities out there (i.e. Sedna). Also, at the time, the TV show was still on TV, which shows you how long we've been searching![30]
"We assumed [that] a real name would come out fairly quickly, [but] the process got stalled," Mike Brown said in interview,
One reporter called me up from the New York Times who happened to have been a friend of mine from college, [and] I was a little less guarded with him than I am with the normal press. He asked me, "What's the name you guys proposed?" and I said, "Well, I'm not going to tell." And he said, "Well, what do you guys call it when you're just talking amongst yourselves?"... As far as I remember this was the only time I told anybody this in the press, and then it got everywhere, which I only sorta felt bad about—I kinda like the name.[31]
[සංස්කරණය] Choosing an official name
According to science writer Govert Schilling, Brown initially wanted to call the object "Lila", after a concept in Hindu mythology that described the cosmos as the outcome of a game played by Brahma. The name was very similar to "Lilah", the name of Brown's newborn daughter. Brown was mindful of not making his name public before it had been officially accepted. He had done so with Sedna a year previously, and had been heavily criticised. However, he listed the address of his personal web page announcing the discovery as /~mbrown/planetlila and in the chaos following the controversy over the discovery of Haumea, forgot to change it. Rather than needlessly anger more of his fellow astronomers, he simply said that the webpage had been named for his daughter and dropped "Lila" from consideration.[32]
Brown had also speculated that Persephone, the wife of the god Pluto, would be a good name for the object.[2] The name had been used several times in science fiction,[33] and was popular with the public, having handily won a poll conducted by New Scientist magazine ("Xena", despite only being a nickname, came fourth).[34] However, this was not possible once the object was classified as a dwarf planet, because there is already an asteroid with that name, 399 Persephone.[2] Because IAU regulations require a name from creation mythology for objects with orbital stability beyond Neptune’s orbit, the team had also been considering such possibilities.[35]
With the dispute resolved, the discovery team proposed Eris on September 6, 2006. On September 13, 2006 this name was accepted as the official name by the IAU.[35][36] Brown decided that, as the object had been considered a planet for so long, it deserved a name from Greek and Roman mythology, like the other planets. However, the asteroids had taken the vast majority of Graeco-Roman names. Eris, whom Brown described as his favourite goddess, had fortunately escaped inclusion.[31] The name in part reflects the discord in the astronomical community caused by the debate over the object’s (and Pluto’s) nature.
[සංස්කරණය] Orbit
Eris has an orbital period of 557 years, and as of 2011 lies at 96.6 astronomical units from the Sun,[12] almost its maximum possible distance (its aphelion is 97.5 AU). It came to perihelion between 1698[5] and 1699,[37] to aphelion around 1977,[37] and will return to perihelion around 2256[37] to 2258.[38] Eris and its moon are currently the most distant known objects in the Solar System apart from long-period comets and space probes.[39] However, approximately forty known TNOs, most notably සැකිල්ල:Mpl, සැකිල්ල:Mpl- and සැකිල්ල:Dp, while currently closer to the Sun than Eris, have greater average orbital distances than Eris' semimajor axis of 67.7 AU.[4]
The Eridian orbit is highly eccentric, and brings Eris to within 37.9 AU of the Sun, a typical perihelion for scattered objects. This is within the orbit of Pluto, but still safe from direct interaction with Neptune (29.8–30.4 AU). Pluto, on the other hand, like other plutinos, follows a less inclined and less eccentric orbit and, protected by orbital resonance, can cross Neptune’s orbit. It is possible that Eris is in a 17:5 resonance with Neptune, though further observations will be required to check that hypothesis.[40] Unlike the eight planets, whose orbits all lie roughly in the same plane as the Earth's, Eris' orbit is highly inclined: It is tilted at an angle of about 44 degrees to the ecliptic. In about 800 years, Eris will be closer to the Sun than Pluto for some time (see the graph at the right).
Eris currently has an apparent magnitude of 18.7, making it bright enough to be detectable to some amateur telescopes. A 200 mm telescope with a CCD can detect Eris under favourable conditions.[c] The reason it had not been noticed until now is its steep orbital inclination; most searches for large outer Solar System objects concentrate on the ecliptic plane, where most bodies are found.
Eris is now in the constellation Cetus. It was in Sculptor from 1876 until 1929 and Phoenix from roughly 1840 until 1875. In 2036 it will enter Pisces and stay there until 2065, when it will enter Aries.[37] It will then move into the northern sky, entering Perseus in 2128 and Camelopardalis (where it will reach its northernmost declination) in 2173. Because of the high inclination of its orbit, Eris only passes through a few constellations of the traditional Zodiac.
[සංස්කරණය] Size, mass and density
| Year | Radius (Diameter) | Source |
|---|---|---|
| 2005 | 1,199(2397) km[41] | Hubble |
| 2007 | 1,300(2600) km[7] | Spitzer |
| 2010 | 1,170(2340) km[8] | Occultation |
In 2005, the diameter of Eris was measured to be 2,397 km, give or take 100 km, using images from the Hubble Space Telescope (HST).[14][41] The size of an object is determined from its absolute magnitude (H) and the albedo (the amount of light it reflects). At a distance of 97 AU, an object with a diameter of 3,000 km would have an angular size of 40 milliarcseconds,[13] which is directly measurable with the Hubble Space Telescope. Although resolving such small objects is at the very limit of the telescope's capabilities,[d] sophisticated image processing techniques such as deconvolution can be used to measure such angular sizes fairly accurately.[e]ජනවාරි 5, 2005 දී එරිස් නම් වු වාමන ග්රහයා පහත සඳහන් විද්යාඥයින් විසින් සොයාගන්නා ලදී. මයික් බ්රවින්, චැඩි ට්රැජිලෙප් හා ඩේවිඩ් /බිනොවිට්ස්. ඔක්තොම්බර් 21, 2003 දී ගත් ඡයාරූප වලින් මෙම ආකාශ වස්තුවේ උපස්ථිතිය හෙළි විය. මෙම විද්යාඥයින් කණ්ඩායම විසින් තවත් විශාල අභ්යවකාශ වස්තූන් ද සොයාගන්නා ලදී. 50,000 ක්වොෂා, 90482 ඕකස් හා 90377 සෙඩ්නා මේවාට උදාහරණ වේ.
2003 ඔක්තෝම්බර් 21 දින, කැලිෆෝනියාවේ මවුන්ට් පැලෝමාර් නිරීක්ෂණගාරයේ තිබෙන, 1200 mm ‘සැමුවෙල් ඔස්වින්’ සොයාගැනිමට අපොහොසත් වුණි. මීට හේතුව වූයේ එරිස්හි ගමන් වේගය මෘදුකාංගය මඟින් පැයකට තප්පර (ආක්සෙකන්ඩ්) 1.5 ට වඩා අඩු වේගයෙන් යුත් ආකාශ වස්තූන් බැහැර කරන ලදී. 90377 සෙඩ්නා සොයාගැනීමට හැකිවුයේ එහි වේගය පැයට ආක් තප්පර 1.75 පමණ වු නිසාය. ජනවාරි 2005, නැවත මෘදුකාංගය මඟින් බැහැර කරන ලද ඡායාරූප විශ්ලේෂණය කිරීමේදී එරිස් සොයාගන්නා ලදී.
මින් අනතුරුව, එරිස්හි කක්ෂය නිර්ණය කිරීමට නිරීක්ෂණ කරන ලදී. 'හව්මියා' නමැති තවත් අභ්යවකාශ වස්තූවක උපස්ථිතිය වෙනත් විද්යාඥයින් කණ්ඩායමක් මගින් ලොවට හෙළිකළ නිසා එරිස්හි උපස්ථිතිය හෙළිකිරීමට විද්යාඥයින් කණ්ඩායම විසින් පියවර ගන්නා ලදී.
ඔක්තෝබර් 2005 දී 'එරිස්' ට 'ඩිස්නෝමියා' නම් චන්ද්රයෙක් සිටින බව හෙළිවිය. 'ඩිස්නෝමියා' හි කක්ෂය පිළිබඳ මිනුම් ගැනීමෙන් අනතුරුව 'එරිස්' හි ස්කන්ධය සොයා ගැනීමට විද්යාඥයින්ට හැකිවිය. මෙය 2007 ජුනි මාසයේ ගණනය කළ අතර, එහි අගය(1.66+-0.02) x 10 22 kgවිය. මෙය ප්ලුටෝ ග්රහයාගේ ස්කන්ධයට වඩා 27% වැඩි අගයකි.
[සංස්කරණය] සටහන්
| Eris dwarf planet - Discovery |
උපන්යාස දෝෂය: <ref> ටැග පැවතුණත්, <references/> ටැග සොයාගත නොහැකි විය.
