Mu 2006 ni bwo Ihuriro mpuzamahanga ry’Abashakashatsi mu by’Isanzure (International Astronomical Union, IAU), ryakoze itora ku gisobanuro cy’umubumbe.

Icyo gihe hasanzwe Pluto itacyujuje ibisabwa ngo ibe umubumbe, bituma ishyirwa mu cyiciro cya ‘dwarf planet’, wagereranya n’ibindi bintu byo mu isanzure bijya kumera nk’umubumbe ariko bitujuje ibisabwa byose ngo byitwe umubumbe.

Kuva icyo gihe hari izindi mpinduka zakomeje kugaragara kuri Pluto, bituma abashakashatsi bamwe bibaza niba igihe cyaba kigeze ngo igisobanuro cy’umubumbe gihindurwe.

Muri rusange nta gisobanuro gihamye cy’umubumbe cyashyizweho, ndetse abashakashatsi mu by’Isanzure bakunze gukoresha ibisobanuro bwawo bigengesera cyane.

Nko mu bihe by’Abagereki bo hambere, umubumbe wasobanurwaga nk’inyenyeri igenda mu isanzure, aho Ukwezi n’Izuba nabyo byafatwaga nk’imibumbe.

Mu gihe cya “Copernican revolution” ubwo kwiga isanzure byatangiye gushingira ku Izuba aho gushingira ku Isi, Ukwezi kwakuwe mu cyiciro cy’imibumbe, kugirwa ‘satellite’.

Isi yahise ifatwa nk’umubumbe, naho Izuba rishyirwa mu cyiciro cy’ikirenga kuko ni ryo ryahise rihinduka ifatiro ry’ubushakashatsi mu isanzure.

Ni yo mpamvu ibyo abashakashatsi babonye uyu munsi babisobanura bafatiye ku karere kabarizwamo imibumbe igaragiye izuba (Solar System), haba mu kugaragaza intera birimo cyangwa imiterere yabyo n’ingaruka byagira.

Ibyo byagendeweho imyaka igera kuri 200, kugeza ubwo Umwongereza wakomokaga mu Budage, William Herschel, yavumbuye Uranus; naho Umutaliyani Giuseppe Piazzi akavumbura Ceres yari nini cyane mu ruhererekane rw’amabuye yo mu isanzure abarizwa hagati ya Mars na Jupiter.

Bijya gutangira, Uranus na Ceres byafashwe nk’imibumbe. Gusa uko hagiye havumburwa ibindi bintu byinshi mu isanzure bihuje inzira binyuramo na Ceres, abashakashatsi bongeye kubitekerezaho, basanga imibumbe iba ituye yonyine.

Herschel yasabye ko ibintu bito bigaragara hagati ya Mars na Jupiter byafatwa nk’amabuye yo mu Isanzure (astéroïde), naho Uranus yo igakomeza gufatwa nk’umubumbe.

Icyakora icyo gitekerezo cye cyanenzwe ko bamwe mu bashakashatsi basangaga kigamije ko izina rya Herschel rikomeza gukomera nk’uwavumbuye Uranus.

Abashakashatsi bakomeje kugendera kuri ibyo byiciro kugeza ubwo Umunyamerika Clyde Tombaugh yavumburaga Pluto mu 1930. Gusa uyu mubumbe mushya ntiwari ufite inzira ihamye unyuramo uzenguruka mu isanzure, kandi wari muto cyane ugereranyije n’indi mibumbe.

Ni ibintu byatumye abashakashatsi batangira kwibaza niba badakwiye kongera gusuzuma uko ibiri mu isanzure byashyizwe mu byiciro.

Kuva mu myaka ya 1990, abashakashatsi batangiye kubona mu Isanzure ibintu byinshi binyura mu nzira imwe na Pluto.

Mu 2005 ni bwo Umunyamerika Mike Brown yavumbuye Eris, ‘dwarf planet’ ihuje imitere na Pluto, inyura mu nzira iri inyuma ya Neptune. Byahise biba imbarutso y’amakenga menshi ku gufata Pluto nk’umubumbe.

Byatumye abashakashatsi bateraniye i Prague muri Repubulika ya Tchèque mu 2006 biyemeza guhuza ibitekerezo bakagaragaza ubusobanuro bukwiye kuranga icyitwa umubumbe.

Igice kimwe cy’abo bashakashatsi cyasabaga ko umubumbe wareberwa ku buryo ugaragara, ikindi kigasaba ko imibumbe yajya igenzurirwa ku biyigize cyangwa ibiyiranga.

Abasabaga ko imibumbe isobanurwa hashingiwe ku buryo igaragara, bavugaga ko umubumbe ukwiye kuba icyo ari cyo cyose kinini bihagije kandi gifite ishusho y’uruziga.

Bagenzi babo bo bavugaga ko umubumbe ukwiye kuba ikintu icyo ari cyo cyose gishobora kuganza mu nzira kinyuramo kizenguruka mu isanzure, ndetse kikaba cyakuramo utundi tuvungukira utwo ari two twose twaba tuyirimo.

Icyo gisobanuro cyashoboraga gutuma Pluto, Ceres n’ ibindi byazengurukaga mu nzira imwe na Pluto byose bihinduka imibumbe; ariko ibito byavumbuwe mu isanzure byose ntibyari kuba muri icyo cyiciro.

Byarangiye hemejwe ko ibyo bisobanuro bibiri by’impande zombi byashyirwa mu gisobanuro cy’umubumbe.

Kuko Pluto itakuraga mu nzira utundi tuvungukira n’ibintu bito biri mu nzira inyuramo izenguruka bigatuma izengurukana n’ibintu byinshi, hanzuwe ko itakomeza gufatwa nk’umubumbe.

Icyakora si buri mushakashatsi wemeranya n’icyo gisobanuro cyemerejwe muri iyo nama, ibyatumye hakomeza impaka z’urudaca zigihari kugeza uyu munsi.

Magingo aya kuvuga ngo ikintu ‘giteye nk’uruziga’ no kuvuga ngo ‘igikura ibindi bintu bito mu nzira kinyuramo kizenguruka’ ntibyumvikanwaho.

Icyakora abashyigikiye izo ngingo ebyiri bavuga ko imibumbe yose kuva kuri Mercure kugeza kuri Neptune, ifite imiterere nk’iy’uruziga.

Ni mu gihe ibyinshi mu bishidikanywaho ku kuba byakwitwa imibumbe, usanga n’ubundi bidateye nk’uruziga.

Ku kuganza mu nzira umubumbe unyuramo, hagaragazwa ko Mars ikubye inshuro 5.000 ikindi kintu wakwita ko ari kinini mu nzira uwo mubumbe unyuramo uzenguruka.

Nyamara ubunini bwa Pluto bukwira muri 7% by’inzira inyuramo gusa, ibintu bigaragaza neza ko nta tandukaniro rifatika riri hagati yayo n’ibindi bintu binyura muri iyo nzira.

Gusa urujijo rukomeza kuba ku bindi byiciro bikwiye gushyirwamo bya bintu byo mu isanzure bitari imibumbe, by’umwihariko ibifite ishusho imeze nk’uruziga ariko bitaganje mu nzira binyuramo bizenguruka.

Aho ngaho ingero za hafi zihita ziba Pluto na Ceres kugeza ubu zishyirwa mu cyiciro cya ‘dwarf planet’.

Abashakashatsi bakunze gukoresha ijambo ‘dwarf’ basobanura ikintu gito mu cyiciro runaka, bavuga nk’inyenyeri cyangwa ibindi.

Ariko ugeze ku mibumbe usanga ‘dwarf planet’ bidahita bisobanura umubumbe muto, mu gihe ari cyo byakabaye bisobanura ushingiye ku buryo ijambo ‘dwarf’ risanzwe rikoreshwa.

Iyo icyagaragaye mu isanzure basanze ari gito ku buryo kidafite imiterere nk’iy’uruziga (bene iyo miterere akenshi ishingira ku bunini bwacyo) gishyirwa mu cyiciro cy’ibintu bito byo mu karere kabarizwamo imibumbe igaragagiye Izuba (small solar system body).

Ibinonko (Comets) ni cyo cyiciro bibamo, ariko amabuye (asteroids) si ho abarizwa ngo kuko yo ataba imbere cyane muri ‘solar system’.

Hari icyiciro cyitwa ‘minor planets’ cyagereranwa n’imibumbe mito, kibarizwamo ‘dwarf planets’ na ‘small solar system bodies’ zitari ibinonko.

Ni ukuvuga ko ‘plutoids’ wagereranya na ‘dwarf planets’ zizenguruka Pluto, ndetse na ‘trans-Neptunian objects’ wagereranya na ‘plutoids’ na ‘small solar system bodies’ zizenguruka Neptune, byose ntibigira icyiciro bibarizwamo gihamye magingo aya.

Ibi bigaragazwa nk’ikintu kikiri ihurizo rikomeye ku bashakashatsi bashaka gutanga ibisobanuro bw’ibiri mu isanzure no kubigaragaza kuri gahunda, kandi imiterere yaryo yerekana ko ibiririmo bitari mu buryo buhamye ku buryo kubisobanura byakoroha.

Hagaragazwa ko kuri ubu nibura abashakashatsi bakabaye bakomeza kugendera ku bisobanuro bihari n’ubwo bitari shyashya. Icyakora hari icyizere ko ibibera mu isanzure byazasobanurwa neza igihe kimwe bitewe n’ikoranabuhanga rigenda ryiyambazwa mu bushakashatsi.