Author Topic: May 23rd 2009 OOTD Hyper-Velocity Stars HVS  (Read 8043 times)

Lovethetropics

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May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« on: May 23, 2009, 12:02:41 am »



Hyper-velocity stars
A star that is ejected at very high velocity (on the order of 1,000 km/s) from the center of a galaxy due to interaction with a massive central black hole. The existence of hypervelocity stars was first proposed in 1988. Computer models indicated that hypervelocity stars ought to be a natural consequence of binary stars coming close to the supermassive black hole known to exist at the heart of our own Milky Way Galaxy. When a binary swings too close to the central black hole, the intense gravity can tear the binary apart, capturing one star while violently flinging the other outward at enormous speed.

In 2005, the first hypervelocity star was discovered by astronomers using the Multiple Mirror Telescope in Arizona. Known as SDSS J090745.0+024507, it is 71 kiloparsecs from the Sun and moving through the outskirts of the galaxy – the so-called galactic halo – at about 850 km/s (528 miles/sec). This is more than twice the velocity needed to escape the Milky Way. SDSS J090745.0+024507 is expected to leave the galaxy altogether within 80 to 100 million years.

European groups subsequently identified two more hypervelocity stars, one of which may have originated in a neighboring galaxy, the Large Magellanic Cloud. In January 2006, the discovery of two more such objects was announced by the Arizona group, bringing the total number of known stellar exiles to five.

The two most recently discovered hypervelocity stars are both short-lived types, about four times more massive than the Sun. One lies in the direction of the constellation Ursa Major and is designated SDSS J091301.0+305120. It is traveling out of the galaxy at a speed of about 556 km/s (1.25 million mph) and is currently located about 240,000 light-years from us. The other, in the direction of the constellation Cancer, is designated SDSS J091759.5+672238. It is moving outward at 639 km/s (1.43 million mph) and is presently about 180,000 light-years away.

Astronomers estimate that a star is thrown from the galactic center every 100,000 years on average and that altogether there are about 1,000 hypervelocity stars heading out of the Galaxy. Finding them, however, among a stellar population that exceeds 100 billion is not easy.

Hypervelocity stars are becoming important tools for understanding massive black holes and also offer a unique probe of galactic structure. During their lifetime, these stars travel across most of the Galaxy. By measuring their movements across the sky, it ought to possible to refine our knowledge of the shape of the Milky Way and about the way its dark matter is distributed.


Hello everyone and thank you for reading this OOTD.  The information posted here comes from this site and here's the link to it.  




We on Galaxy Zoo are very lucky, we have nine of the 10 hyper-velocity stars on the SDSS footprint.  And here they are.  Only three say they are HVS.


Thank you dear Tommy for getting the objID's for the HVS's and for remembering the HVS stars I posted a while ago on your newbies' thread.
Thank you dear Alice for beautifying the OOTD.
Thank you dear Jules for the links and for saving this OOTD at the last minute like a hero out of a book. :-* ;D


HVS 1
SDSS J090744.99+024506.8 -- Variable Star
588010358530507060


Believe it or not I found another one five minutes after I posted this.
http://cas.sdss.org/astro/en/tools/explore/obj.asp?id=587732135914635282


HVS 2

SDSS J093320.86+441705.4 -- White Dwarf
588013383268565133


Number 3 not in SDSS

Number 4
[BGK2006] J091301.01+305119.8 -- Star
588017979949842518


Number 5
SDSS J091759.47+672238.3 -- Star

587738068348960770


Number 6
SDSS J110557.45+093439.4 -- Star
587732771585458263


Number 7
[BGK2006] J113312.12+010824.9 -- White Dwarf
588848901520359456


Number 8
[BGK2006] J094214.04+200322.1 -- Star
587741821063790648


Number 9
[AG92] 16400 -- Horizontal Branch Star and  [BGK2006] J102137.08-005234.8 -- Star
588848898828140657

Number 10

[BGK2006] J120337.86+180250.3   and   LSPM J1203+1802 -- High proper-motion Star
587742775095918754



I would like to say Happy Birthday to my husband Benito, today is his birthday.  Thank you dearest for your love and support ever since we met.
And a special hello to all my sisters from the Apostolado School. :-*
And my children, Laura, Benny and Moti and grandkids.  :-*



« Last Edit: July 04, 2009, 10:20:30 am by Lovethetropics »

 *and find lots of asteroids  ;D

citisue

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #1 on: May 23, 2009, 12:53:55 am »
WoW Aida, very interesting OOTD ;D ;D ;D

And here's to you -n- hubby  btw, I like your husbands name, Benito ;)
The best way to predict your future is to create it :)

Lovethetropics

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #2 on: May 23, 2009, 01:01:07 am »
WoW Aida, very interesting OOTD ;D ;D ;D

And here's to you -n- hubby  btw, I like your husbands name, Benito ;)

Thank you so much Sue.  ;D  How are you feeling?  I read you fell down and hit your head?  What did the doctor say?

 *and find lots of asteroids  ;D

marke

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #3 on: May 23, 2009, 01:11:28 am »
nice one Lovethetropics :)
"To raise new questions, new possibilities, to regard old problems from a new angle, requires creative imagination and marks real advance in science"

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elizabeth

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #4 on: May 23, 2009, 01:30:59 am »
 8) 8) 8) OOTD Aida. A big   on the cheek for Benito  ;)

Lovethetropics

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #5 on: May 23, 2009, 02:09:18 am »
Thank you  Marke and Liz!!  :D :D

I will Liz as soon as it's midnight here!!  Thanks!!  :-* :-*

 *and find lots of asteroids  ;D

Geoff

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #6 on: May 23, 2009, 06:27:18 am »
Thanks for the interesting OOTD Aida. I guess any planets that the HVS star had get left behind when it zooms off!
  Sometimes I think we're alone. Sometimes I think we're not. In either case, the prospect is staggering!- Arthur C. Clarke

Caro

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #7 on: May 23, 2009, 06:42:04 am »
Very interesting OotD Aida. And happy birthday to Benito.  :D
If things of sight such Heavens be, What Heavens are those we cannot see? Andrew Marvell

waveney

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #8 on: May 23, 2009, 06:43:32 am »
Interesting read Aida, and happy birthday to Benito
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Mukund Vedapudi

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #9 on: May 23, 2009, 07:46:43 am »
Hey Aida
Nice one, and happy birthday to Benito. ;D
Faith is the bird singing when the dawn is yet dark.

Pat

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #10 on: May 23, 2009, 08:00:48 am »
Very interesting Aida. :) Hope you have a Happy Birthday too. :)

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jules

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #11 on: May 23, 2009, 10:06:00 am »
Really unusual topic - more astronomy to learn! :D :D
And Happy Birthday to Mr Aida!!

LizPeter

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #12 on: May 23, 2009, 01:19:14 pm »
Brilliant.

AlexandredOr

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #13 on: May 23, 2009, 01:21:32 pm »
Great work... Thx A

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PaddyD

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Re: May 23rd 2009 OOTD Hyper-Velocity Stars HVS
« Reply #14 on: May 23, 2009, 02:32:24 pm »
Supper OOTD Adia.
Big thanks. ;)