View Full Version : That Neutron Star Should Be a Black Hole

2005-Nov-02, 05:48 PM
SUMMARY: Astronomers were expecting that a massive star in the Westerlund 1 star cluster should have collapsed into a black hole. Instead, it became a neutron star. Since this star was 40 times the mass of the Sun before it collapsed, it should have been a prime black hole candidate. So why did it end up as a neutron star? It's possible that the star blew off most of its mass at the end of its life, so there just wasn't enough material to form a black hole.

View full article (http://www.universetoday.com/am/publish/case_mistaken_identity.html)
What do you think about this story? post your comments below.

2005-Nov-03, 03:13 PM

it is generally difficult to determine the mass of a star which is in an open cluster that can only be observed in infrared light. Westerlund 1 is such a cluster, totally obscured by milky way dust clouds.
I do not know how the spectral class of a star is specified if the star´s spectrum cannot be specified. Is it for sure that the star at the specified position is a neutron star?
I learned that when doing astronomical research, you often find that positions of stars in star catalogues require some corrections.

The usual theory of star formation and star development considers "usual" stars and does not consider stars that are "unusual". However, if a star is very massive and if this star at the same time rotates very fast, the centrifugal effect of its rotation may change the star shape to something resembling a flat disk (such a shape was found for Achernar and Altair), and this reduces the pressure on the core, as the mass distribution of the star is different from that of a "usual" star. With a lower pressure on the core, the pressure within an "electron gas" (in a white dwarf) or the pressure within a "neutron gas" (in a neutron star) can be less than "usually" should be expected for a star of the type.

So even a supermassive neutron star of many solar masses might have chance to last as a neutron star as long as it rotates fast enough.
But as such a star loses energy due to interaction with its surrounding magnetic field, it will slow down with time and finally collapse to a "usual" black hole.



2006-Apr-17, 02:23 AM
im not really smart. im only 14 but if i understand this. after a massive neutron star stops its spinning. it'll turn into a blackhole. i can understand that because a blackhole and a neutron star have a high gravity. but if it does turn into a blackhole wouldn't it just have another colission with a neutron star nearby and that'll let u learn more. if u do get this message can u send it to my e-mail at bbbbb_b@netzero.com

2006-Apr-17, 12:41 PM
if it does turn into a blackhole wouldn't it just have another colission with a neutron star nearby and that'll let u learn more.

Welcome kafkaz916.

It could only have such a collision if there was already a neutron star very near by (in a close orbit).

2006-Apr-17, 02:05 PM
So why did it end up as a neutron star?The set of all stochastically related variables present from the beginning of the collapse of the proto-stellar cloud that parents each star is considerable and the permutations and combinations of their relative strengths approaches an unbounded number. Consequently, "normal" should cover a very wide range of expectations. The two primary influences should be angular momentum and the magnetic fields present just before, during, and immediately after the explosion. Those with sufficient skill and computational equipment (certainly, not I) should be able to define the parametric envelope that bounds 99.999% of the cases that result.

Spectroscopic analysis of the ratio of each element in the debris to iron may help answer the question in terms of this star's "fingerprint".