Researchers discover why 'blue hook' stars are unusually hot

June 23, 2015
The crowded centre of the Omega Centauri globular cluster. Credit: Hubble Space telescope, NASA

Astronomers have solved a mystery over small, unusually hot blue stars, 10 times hotter than our Sun, that are found in the middle of dense star clusters.

The international team found the so-called blue hook throw off their cool outer layers late in life because they are rotating so rapidly, making them more luminous than usual.

"We've solved an old puzzle. These stars are only half the mass of our Sun yet we could not explain how they became so luminous," said team member Dr Antonino Milone, from ANU Research School of Astronomy and Astrophysics.

"As the star was forming billions of years ago from a disc of gas in the congested centre of the , another star or stars must have collided with the disc and destroyed it."

The research, published in Nature, gives new insights into star formation in the early Universe in the crowded centres of clusters. Star clusters are rare environments in the Universe, in which many stars are born at the same time.

The team studied the globular cluster Omega Centauri, the only cluster visible to the naked eye, which contains around 10 million stars in close proximity to one another.

The model shows the formation of stars in clusters do not all form at once, said co-author Dr Aaron Dotter, also from ANU Research School of Astronomy and Astrophysics.

"These blue stars must form in a second generation of ," he said. "Our new explanation is quite simple, and it hangs together really nicely."

Omega Centauri globular cluster. Credit:ESO/INAF-VST/OmegaCAM

Usually the large disc of ionised gas around a newly-forming star locks its rotation through magnetic effects. For the progenitors of blue hook stars, however, an early destruction of its disc allows the stars to spin up as the gas comes together to form a star.

Because its high rotation rate partially balances the inward force of gravity, the star consumes its hydrogen fuel more slowly and evolves differently throughout its life.

The blue hook phase of its life occurs after more than 10 billion years, when the star has consumed nearly all its hydrogen and begins burning the hotter fuel helium. The different evolution processes leave it with a heavier core which burns brighter than typical helium-burning stars.

Artist's impression of a protostellar disc disrupted by a collision. Credit: Marco Galliani, INAF

Explore further: Image: Hubble's compact blue dwarf galaxy UGC 11411

More information: "Rapidly rotating second-generation progenitors for the 'blue hook' stars of ω Centauri" Nature (2015) DOI: 10.1038/nature14516

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13 comments

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wduckss
1 / 5 (4) Jun 23, 2015
Nothing new. For a long time I announce that the temperature of a star is directly linked to the speed of rotation around the axis.
Quote from my web site: "The temperature of stars is directly related to the speed of its rotation. Those with slower rotation are red, while with the increase of the rotation speed, also increases the glow and the temperature of a star."
El_Nose
4.8 / 5 (8) Jun 23, 2015
did you read the article ??????

this has nothing to do with rotational velocity, This states that the star prematurely cycled through it's hydrogen and entered the helium burning phase early and burns hotter as a result.
JeanTate
5 / 5 (8) Jun 23, 2015
@wdcukss:
For a long time I announce that the temperature of a star is directly linked to the speed of rotation around the axis.
Quote from my web site
Other than on your website, where have you published this idea?

Have you published it as a paper, in a relevant, peer-reviewed journal? If so, reference please!
Tuxford
1 / 5 (5) Jun 23, 2015
In the dense matter regions deep within these clusters, SQK predicts accelerated production of both new matter AND energy (genic energy), the latter via photon blue shifting. Thus, these stars will naturally burn hotter due in part to their location. Similarly, photon blue shifting in the core helps explain Hot Jupiters, warm brown dwarfs, etc.
JeanTate
5 / 5 (5) Jun 23, 2015
@Tuxford:
... SQK predicts...
An idea which has not been sufficiently well studied yet to show consistency with even a small fraction of the relevant astronomical observations and experimental results. Despite the idea having been published many years' ago. And no work has been done on it for many years also.

In short, pseudoscience, right?
Uncle Ira
3.9 / 5 (7) Jun 23, 2015
Nothing new. For a long time I announce that the temperature of a star is directly linked to the speed of rotation around the axis.
Quote from my web site: "The temperature of stars is directly related to the speed of its rotation. Those with slower rotation are red, while with the increase of the rotation speed, also increases the glow and the temperature of a star."


@ Duck-Skippy. How you are podna? I am good me, thanks.

Why you don't put up the linkum or name of your interweb place so I can go over there and see if you are telling truth? About the claim that you already said it over there I mean. Plus maybe I would find some other good stuffs over there to have the fun with.
Tuxford
1.8 / 5 (5) Jun 23, 2015
@Tuxford:
... SQK predicts...
An idea which has not been sufficiently well studied yet to show consistency with even a small fraction of the relevant astronomical observations and experimental results. Despite the idea having been published many years' ago. And no work has been done on it for many years also.

In short, pseudoscience, right?


To the comfortably ignorant more concerned with displaying their knowledge and command of their chosen intellectual domain than with actually understanding the nature of things, then, yes. Labels is not my concern. Understanding is.
JeanTate
5 / 5 (4) Jun 23, 2015
@Tuxford: thanks for the clarification/confirmation.
To the comfortably ignorant more concerned with ... than with actually understanding the nature of things
SQK may be the greatest advance in physics since the 1920s, or it may be nonsense (or anything in between). How to decide which it is? By testing SQK, to see how consistent it is, with all relevant astronomical observations and experimental results. Why not devote your time to at least starting such tests, rather than spamming PO?
wduckss
1 / 5 (3) Jun 24, 2015
@wdcukss:
For a long time I announce that the temperature of a star is directly linked to the speed of rotation around the axis.
Quote from my web site
Other than on your website, where have you published this idea?

Have you published it as a paper, in a relevant, peer-reviewed journal? If so, reference please!

Published in US forums: www.unexplained-mysteries.com, HR: www.geek.hr and Ru: sdnnet.ru.
JeanTate
5 / 5 (5) Jun 24, 2015
@wduckss: Thanks.

So it's pseudoscience, right?
Tuxford
1 / 5 (2) Jun 24, 2015
Blue stars also located in the dense matter region of our galactic core.

http://phys.org/n...ars.html

For the comfortably ignorant: 2+2....
wduckss
1 / 5 (2) Jun 25, 2015
@wduckss: Thanks.

So it's pseudoscience, right?


Research work and not prescribed. The original is.
wduckss
1 / 5 (2) Jun 25, 2015
Nothing new. For a long time I announce that the temperature of a star is directly linked to the speed of rotation around the axis.
Quote from my web site: "The temperature of stars is directly related to the speed of its rotation. Those with slower rotation are red, while with the increase of the rotation speed, also increases the glow and the temperature of a star."


@ Duck-Skippy. How you are podna? I am good me, thanks.

Why you don't put up the linkum or name of your interweb place so I can go over there and see if you are telling truth? About the claim that you already said it over there I mean. Plus maybe I would find some other good stuffs over there to have the fun with.

http://www.svemir...rocesses

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