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Snimljena tamna tvar
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Josko
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Joined: 19 Nov 2005
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Location: Biograd N/M
PostPosted: Sat Aug 18, 2007 6:08    Post subject: Reply with quote

http://space.newscientist.com/article/dn12497
http://tinyurl.com/yqn9cf

Nakon Bullet clustera pojavio se Abell 520 koji se ponaša potpuno drukčije. U Bulletu smo imali plin koji je, izgleda, sam sebe usporavao i tamnu tvar koja uopće nije pokazivala interakciju s plinom unutar klastera. Abell, naprotiv, pokazuje znatnu količinu tamne tvari koja se drži zajedno s plinom.

Pokušalo se objasniti na dva načina, ali nijedan nije zadovoljavajući:
1. Dogodio se veliki broj gravitacijskih praćki uz pomoću kojih se zadržalo tamnu tvar
2. Postoji još neka nama nepoznata interakcija tamne tvari s običnom
abell-520.jpg


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Josko
Vrlo čest korisnik
Vrlo čest korisnik
Joined: 19 Nov 2005
Posts: 75
Location: Biograd N/M
PostPosted: Tue Sep 25, 2007 22:53    Post subject: Reply with quote

http://www.spacedaily.com/reports/The_Magellanic_Clouds_Are_First_Time_Visitors_999.html

Još malo o Magellanovim oblacima i njihovoj prevelikoj brzini. Teško je tamnom tvari objasniti njihovu brzinu pa se pretpostavlja da ipak nisu sateliti Mliječne staze.
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Josko
Vrlo čest korisnik
Vrlo čest korisnik
Joined: 19 Nov 2005
Posts: 75
Location: Biograd N/M
PostPosted: Sat Oct 20, 2007 7:51    Post subject: Reply with quote

Josko wrote:
Priča se nastavlja... ova slika je zaista podigla dosta prašine. Pojavljuju se i teorije o novoj sili:
http://tinyurl.com/yke3qk

Manja skupina galaksija se giba prebrzo, 30-40% brže nego što bi trebala uzevši u obzir samo gravitaciju. Ukoliko nema većih grešaka u mjerenjima ili teoriji, trebala bi postojati i nova "tamna sila".

Ovi zaključci su bili malo preuranjeni:
Added 14 Mar 07: It looks like the dark force just went poof. Farrar and Volker Springel of the Max Planck Institute for Astrophysics have found that the clusters' speed was overestimated.

http://arxiv.org/abs/astro-ph/0703232
despite a shock speed of 4500 km/s, the subcluster's mass centroid is moving only with 2600 km/s in the rest frame of the system
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Josko
Vrlo čest korisnik
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Joined: 19 Nov 2005
Posts: 75
Location: Biograd N/M
PostPosted: Sat Aug 16, 2008 9:07    Post subject: Reply with quote

http://tinyurl.com/588lvd
Opet promjena slike o našoj galaksiji. Otkrivaju se novi prateći objekti, spomenuto istraživanje je otkrilo 11 novih. Većina tih pratećih "galaksijica" biva rastegnuta pod gravitacijskim utjecajem središta galaksije. Neke galaksijice ili njihovi dijelovi bivaju rastegnuti u trake (nizove zvijezda) koji završavaju u središtu Mliječne staze.

Zašto sam stavio pod ovu temu? Zapelo mi je za oko sljedeće:
The SDSS dwarfs have far fewer stars than the previously known satellites, noted Gilmore, but they have similar spatial extents, and the stars within them move at similar speeds. "I think the internal dynamics of these tiny galaxies may be hard to explain with our conventional ideas about dark matter," said Gilmore.
Dakle, galaksije sateliti, koje je pratio SDSS, po svom unutrašnjem gibanju se teško mogu objasniti našim trenutnim poznavanjem tamne materije.
sdss3_middle_th.jpg

Mliječna staza i sateliti

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