Pressemeddelelse

Er det her den mindste dværgplanet i Solsystemet?

ESO-teleskop leverer måske svaret.

28. oktober 2019

Asteroiden Hygiea kan måske klassificeres som en dværgplanet. Det tyder nye observationer gjort med instrumentet SPHERE ved ESOs Very Large Telescope (VLT) på. Asteroiden er den fjerdestørste i asteroidebæltet, efter Ceres, Vesta og Pallas. For første gang er Hygiea observeret i så stor detalje, at det har været muligt at studere overflade og bestemme dens form og størrelse. Forskerne kan se, at Hygiea er sfærisk, og dermed kan den måske snuppe æren for at være den mindste dværgplanet i Solsystemet fra Ceres.

 

I og med at Hygiea befinder sig i asteroidebæltet opfylder den allerede tre af de fire krav, som stilles for at den kan klassificeres som en dværgplanet: den kredser om Solen, den er ikke en måne, og til forskel fra en "rigtig" planet har den ikke støvsuget området omkring sin bane for andre objekter. Den sidste betingelse er, at den skal have nok masse til at dens egen tyngdekraft kan trække den sammen til en nogenlunde kugleform. Og det er lige det, som observationerne med VLT har vist for Hygiea.

"Takket være instrumentet SPHEREs helt unikke billedskabende muligheder på VLT, kunne vi se Hygieas facon, og den er faktisk næsten sfærisk," siger chefforsker Pierre Vernazza fra Laboratoire d'Astrophysique de Marseille i Frankrig. "Ud fra disse billeder kan vi reklassificere Hygiea som dværgplanet, og den bliver så den mindste i Solsystemet."

Forskerholdet brugte også SPHERE-observationerne til at sætte en grænse for Hygieas størrelse - med en diameter på lige over 430 km. Pluto, som er den mest kendte af dværgplaneterne, er tæt på 2400 km i diameter, og Ceres er tæt på 950 km.

Overraskende nok har observationerne også vist, at Hygiea mangler det meget store nedslagskrater, som forskerne forventede var et sted på dens overflade, fortæller de i den artikel, som bliver offentliggjort idag i tidsskriftet Nature Astronomy. Hygiea er det største medlem af en af de største asteroidefamilier, hvor der er tæt på 7000 medlemmer, som alle har deres oprindelse fra det samme større objekt. Astronomerne havde forventet, at den kollision, som skabte denne talrig familie, ville have efterladt et større aftryk på Hygiea.

"Resultatet her var en virkelig overraskelse, for vi forventede, at der var et større nedslagskrater, som det for eksempel er tilfældet med Vesta," siger Vernazza. Selvom astronomerne har observeret 95% af Hygieas overflade, er det kun lykkes at finde to sikre kratere. "Ingen af de to kratere kan stamme fra det nedslag, som skabte Hygieafamilien. Det er de for små til. Til sammen ville alle familiemedlemmerne udgøre et himmellegeme med en diameter på 100 km," forklarer medforfatter til artiklen Miroslav Brož fra Astronomical Institute of Charles University in Prag, Tjekkiet.

Forskerholdet besluttede blandt andet derfor at undersøge sagen nærmere. Ved hjælp af numeriske simuleringer kunne de afgøre, at Hygieas runde facon og store familie sandsynligvis skyldes en større direkte kollision med et legeme, som har været imellem 75 og 150 km i diameter. Simuleringerne viser, at dette sammenstød, som er sket for omkring 2 milliarder år siden, fuldstændig knuste det oprindelige legeme. Efterhånden har stumperne samlet sig igen, og det er det, som har forårsaget Hygieas afrundede facon og de tusinder af mindre asteroideledsagere. "En kollision af den størrelsesorden imellem to så store legemer i asteroidebæltet er ellers ikke sket indenfor de seneste 3-4 milliarder år," siger Pavel Ševeček, som er PhD student ved Astronomical Institute of Charles University, og som også var med i forskningsprojektet.

Det er både fremskridt indenfor avancerede beregninger og kraftigere teleskoper, som har gjort det muligt at studere asteroider i sådanne detaljer. "Takket være VLT og instrumentet SPHERE, som er en ny generation med adaptiv optik, kan vi nu tage billeder af asteroider i bæltet imellem Mars og Jupiter med en hidtil uopnåelig opløsning. Dermed kan vi fylde det hul ud, som ellers har været imellem at studere asteroiderne her fra Jorden og så fra interplanetariske rumsonder," slutter Vernazza.

Mere information

 

Forskningsresultaterne her offentliggøres i en artikel den 28. oktober 2019 i tidsskriftet Nature Astronomy.

The team is composed of P. Vernazza (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, Frankrig), L. Jorda (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, Frankrig), P. Ševeček (Institute of Astronomy, Charles University, Prague, Tjekkiet), M. Brož (Institute of Astronomy, Charles University, Prague, Tjekkiet), M. Viikinkoski (Mathematics and Statistics, Tampere University, Tampere, Finland), J. Hanuš (Institute of Astronomy, Charles University, Prague, Tjekkiet), B. Carry (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, Frankrig), A. Drouard (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, Frankrig), M. Ferrais (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgien), M. Marsset (Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, MA, USA), F. Marchis (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, Frankrig, and SETI Institute, Carl Sagan Center, Mountain View, USA), M. Birlan (Observatoire de Paris, Paris, Frankrig), E. Podlewska-Gaca (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Polen, and Institute of Physics, University of Szczecin, Polen), E. Jehin (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgien), P. Bartczak (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Polen), G. Dudzinski (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Polen), J. Berthier (Observatoire de Paris, Paris, Frankrig), J. Castillo-Rogez (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), F. Cipriani (European Space Agency, ESTEC – Scientific Support Office, Nederlandene), F. Colas (Observatoire de Paris, Paris, Frankrig), F. DeMeo (Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, MA, USA), C. Dumas (TMT Observatory, Pasadena, USA), J. Durech (Institute of Astronomy, Charles University, Prague, Tjekkiet), R. Fetick (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, Frankrig and ONERA, The French Aerospace Lab, Chatillon Cedex, Frankrig), T. Fusco (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, Frankrig and and ONERA, The French Aerospace Lab, Chatillon Cedex, Frankrig), J. Grice (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, Frankrig and Open University, School of Physical Sciences, The Open University, Milton Keynes, UK), M. Kaasalainen (Mathematics and Statistics, Tampere University, Tampere, Finland), A. Kryszczynska (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Polen), P. Lamy (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, Frankrig), H. Le Coroller (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, Frankrig), A. Marciniak (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Polen), T. Michalowski (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Polen), P. Michel (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, Frankrig), N. Rambaux (Observatoire de Paris, Paris, Frankrig), T. Santana-Ros (Departamento de Fı́sica, Universidad de Alicante, Alicante, Spanien), P. Tanga (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, Frankrig), F. Vachier (Observatoire de Paris, Paris, Frankrig), A. Vigan (Aix Marseille Université, CNRS, Laboratoire d'Astrophysique de Marseille, Marseille, Frankrig), O. Witasse (European Space Agency, ESTEC – Scientific Support Office, Nederlandene), B. Yang (European Southern Observatory, Santiago, Chile), M. Gillon (Space Sciences, Technologies and Astrophysics Research Institute, Université de Liège, Liège, Belgien), Z. Benkhaldoun (Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco), R. Szakats (Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Budapest, Ungarn), R. Hirsch (Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Poznań, Polen), R. Duffard (Instituto de Astrofísica de Andalucía, Glorieta de la Astronomía S/N, Granada, Spanien), A. Chapman (Buenos Aires, Argentina), J. L. Maestre (Observatorio de Albox, Almeria, Spanien).

ESO er den fremmeste fællesnationale astronomiorganisation i Europa, og verdens langt mest produktive jordbaserede astronomiske observatorium. 16 lande er med i ESO: Belgien, Danmark, Finland, Frankrig, Irland, Italien, Nederlandene, Polen, Portugal, Spanien, Sverige, Schweiz, Storbritannien, Tjekkiet, Tyskland og Østrig, og desuden værtsnationen Chile. Australien er med som strategisk partner. ESO har et ambitiøst program, som gør det muligt for astronomer at gøre vigtige videnskabelige opdagelser. Programmet har focus på design, konstruktion og drift af stærke jordbaserede observatorier. Desuden har ESO en ledende rolle i formidling og organisering af samarbejde omkring astronomisk forskning. ESO driver tre enestående observatorier i verdensklasse i Chile: La Silla, Paranal og Chajnantor. På Paranal driver ESO VLT, Very Large Telescope, som er verdens mest avancerede observatorium for synligt lys, samt to oversigtsteleskoper. VISTA, som observerer i infrarødt, er verdens største oversigtsteleskop, og VLT Survey Teleskopet er det største teleskop bygget til at overvåge himlen i synligt lys. ESO er en af de største partnere i ALMA, som er det største eksisterende astronomiprojekt. For tiden bygges ELT, et 39 m optisk og nærinfrarødt teleskop på Cerro Armazones, tæt ved Paranal. Det bliver "verdens største himmeløje".

Links

Fotos af VLT

Kontakter

Pierre Vernazza
Laboratoire d’Astrophysique de Marseille
Marseille, France
Tel: +33 4 91 05 59 11
E-mail: pierre.vernazza@lam.fr

Miroslav Brož
Charles University
Prague, Czechia
E-mail: mira@sirrah.troja.mff.cuni.cz

Pavel Ševeček
Charles University
Prague, Czechia
E-mail: pavel.sevecek@gmail.com

Bárbara Ferreira
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6670
E-mail: pio@eso.org

Ole J. Knudsen (Pressekontakt Danmark)
ESOs formidlingsnetværk og Aarhus Space Centre, Aarhus Universitet
Aarhus, Danmark
Tel: +45 8715 5597
E-mail: eson-denmark@eso.org

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Dette er en oversættelse af ESO pressemeddelelse eso1918 lavet af ESON - et netværk af personer i ESOs medlemslande, der er kontaktpunkter for medierne i forbindelse med ESO nyheder, pressemeddelelser mm.

Om pressemeddelelsen

Pressemeddelelse nr.:eso1918da
Navn:Hygiea
Type:Solar System : Interplanetary Body : Dwarf planet
Facility:Very Large Telescope
Instruments:SPHERE
Science data:2020NatAs...4..136V

Billeder

Billede af Hygiea fra SPHERE
Billede af Hygiea fra SPHERE
SPHERE billeder af Hygiea, Vesta og Ceres
SPHERE billeder af Hygiea, Vesta og Ceres

Videoer

ESOcast 211 Light: ESO Telescope Reveals What Could be the Smallest Dwarf Planet in the Solar System
ESOcast 211 Light: ESO Telescope Reveals What Could be the Smallest Dwarf Planet in the Solar System
Hygieas plads i Solsystemet
Hygieas plads i Solsystemet
Simulering af sammenstødet, som måske forklarer hvorfor Hygiea er rund
Simulering af sammenstødet, som måske forklarer hvorfor Hygiea er rund

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