STScI: Hyperfast Star Was Booted from Milky Way

[bystander]

Hyperfast Star Was Booted from Milky Way
Hubble Site | Space Telescope Science Institute (STScI-2010-19) | 22 July 2010

NASA's Hubble Space Telescope has detected a hypervelocity star – a rare entity moving three times faster than our sun.

[b]Illustration shows possible mechanism for how HE 0437-5439 acquired enough energy to be ejected from the Milky Way. [i](Credit: NASA/ESA/STScI/A. Field)[/i][/b]

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A hundred million years ago, a triple-star system was traveling through the bustling center of our Milky Way galaxy when it made a life-changing misstep. The trio wandered too close to the galaxy's giant black hole, which captured one of the stars and hurled the other two out of the Milky Way. Adding to the stellar game of musical chairs, the two outbound stars merged to form a super-hot, blue star.

This story may seem like science fiction, but astronomers using NASA's Hubble Space Telescope say it is the most likely scenario for a so-called hypervelocity star, known as HE 0437-5439, one of the fastest ever detected. It is blazing across space at a speed of 1.6 million miles (2.5 million kilometers) an hour, three times faster than our Sun's orbital velocity in the Milky Way. Hubble observations confirm that the stellar speedster hails from the Milky Way's core, settling some confusion over where it originally called home.

Most of the roughly 16 known hypervelocity stars, all discovered since 2005, are thought to be exiles from the heart of our galaxy. But this Hubble result is the first direct observation linking a high-flying star to a galactic center origin.

Black hole at Milky Way core powers galaxy's fastest stars
University of Michigan | 22 July 2010

[b]Illustration shows hot, blue star HE 0437-5439 being tossed out of the center of our Milky Way galaxy with enough speed to escape the galaxy's gravitational clutches. [i](Credit: NASA/ESA/STScI/G. Bacon)[/i][/b]

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The black hole at the center of the galaxy is to blame for sling-shotting "hypervelocity stars" out of the Milky Way at up to 1.8 million miles per hour, according to new evidence from research involving a University of Michigan astronomer.

Hypervelocity stars, discovered about five years ago, are the fastest stars astronomers have ever observed. They are escaping the galaxy at beyond what was thought to be its stellar speed limit.

The researchers used the Hubble Space Telescope to trace the trajectory and origin of HE 0437−5439, a speeding star in the southern hemisphere too faint to be seen with the naked eye. A paper about their findings has been accepted to Astrophysical Journal Letters.
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Just 16 hypervelocity stars have been discovered so far. There are 100 billion stars in the Milky Way.

The paper is titled "A Galactic Center Origin for HE 0437−5439, the Hypervelocity Star Near the Large Magellanic Cloud." This research is funded by NASA and the Smithsonian Institution.

A Galactic Center Origin for HE 0437−5439, the Hypervelocity Star Near the Large Magellanic Cloud

• Astrophysical Journal Letters 719 L23 (2010 Aug 10) doi: 10.1088/2041-8205/719/1/L23
  arXiv.org > astro-ph > arXiv:1007.3493 > 20 July 2010

[orin stepanek]

I thought somebody asked recently what happens when stars collide! In this case they became One. Of course they were both going about the same direction so maybe they didn't hit too hard.

[neufer]

I thought somebody asked recently what happens when stars collide! In this case they became One.
Of course they were both going about the same direction so maybe they didn't hit too hard.

I have a lot of BS concerning that:

<<Blue stragglers (BSS) are main sequence stars in open or globular clusters that are more luminous and bluer than stars at the main sequence turn-off point for the cluster. Blue stragglers were first discovered by Allan Sandage in 1953 while performing photometry of the stars in the globular cluster M3. Standard theories of stellar evolution hold that the position of a star on the Hertzsprung–Russell diagram should be determined almost entirely by the initial mass of the star and its age. In a cluster, stars all formed at approximately the same time, and thus in an H–R diagram for a cluster, all stars should lie along a clearly defined curve set by the age of the cluster, with the positions of individual stars on that curve determined solely by their initial mass. With masses two to three times that of the rest of the main sequence cluster stars, blue stragglers seem to be exceptions to this rule. The resolution of this problem is likely related to interactions between two or more stars in the dense confines of the clusters in which blue stragglers are found.

A Hubble Space Telescope image of NGC 6397, with a number of bright blue stragglers present.

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Several explanations have been put forth to explain the existence of blue stragglers. The simplest is that blue stragglers formed later than the rest of the stars in the cluster, but evidence for this is limited. Another simple proposal is that blue stragglers are either field stars which are not actually members of the clusters to which they seem to belong, or are field stars which were captured by the cluster. This too seems unlikely, as blue stragglers often reside at the very center of the clusters to which they belong.
[edit] Cluster interactions

The two most viable explanations put forth for the existence of blue stragglers both involve interactions between cluster members. One explanation is that they are current or former binary stars that are in the process of merging or have already done so. The merger of two stars would create a single more massive star, potentially with a mass larger than that of stars at the main sequence turn-off point. While a star born with a mass larger than that of stars at the turn-off point would have already evolved off of the main sequence, a more massive star which formed via merger would not have evolved as quickly. There is evidence in favor of this view, notably that blue stragglers appear to be much more common in dense regions of clusters, especially in the cores of globular clusters. Since there are more stars per unit volume, collisions and close encounters are far more likely in clusters than among field stars and calculations of the expected number of collisions are consistent with the observed number of blue stragglers.

One way to test this hypothesis is to study the pulsations of variable blue stragglers. The asteroseismological properties of merged stars may be measurably different from those of typical pulsating variables of similar mass and luminosity. However, the measurement of pulsations is very difficult, given the scarcity of variable blue stragglers, the small photometric amplitudes of their pulsations and the crowded fields in which these stars are often found. Some blue stragglers have been observed to rotate quickly, with one example in 47 Tucanae observed to rotate 75 times faster than the Sun, which is consistent with formation by collision.

The other explanation relies on mass transfer between two stars born in a binary star system. The more massive of the two stars in the system will evolve first and as it expands, will overflow its Roche lobe. Mass will quickly transfer from the initially more massive companion on to the less massive and like the collision hypothesis, would explain why there would be main sequence stars more massive than other stars in the cluster which have already evolved off of the main sequence. Observations of blue stragglers have found that some are lacking in carbon and oxygen in their photospheres, which is evidence of having dredged up from the interior of a companion.

Overall, there is evidence in favor of both collisions and mass transfer between binary stars. In M3, 47 Tucanae and NGC 6752, both mechanisms seem to be operating, with collisional blue stragglers occupying the cluster cores and mass transfer blue stragglers at the outskirts. The discovery of low-mass white dwarf companions around two blue stragglers in the Kepler field suggests these two blue stragglers gained mass via stable mass transfer.

Other types

"Yellow stragglers" or "red stragglers" are stars with colors between that of the turnoff and the red giant branch but brighter than the subgiant branch. Such stars have been identified in open and globular star clusters. These stars may be former blue straggler stars that are now evolving toward the giant branch.>>

[Beyond]

Neufer, i find that i can not disagree with you. You most certainly had a lot of BS about the topic and a little bit of YS and RS also.
The problem is now we have something else to worry about -- REAL SHOOTING STARS

[neufer]

Neufer, i find that i can not disagree with you. You most certainly had a lot of BS about the topic and a little bit of YS and RS also.
The problem is now we have something else to worry about -- REAL SHOOTING STARS

Click to play embedded YouTube video.

[Ann]

More blue stars! Me likes!



Ann

[owlice]

That's very pretty!