恐怖“吸血鬼太陽”揭開銀河系演變之謎(組圖)

havreyl · 發表於 2012-7-29 09:32:13

天文學家們通過本項研究可以了解到更多關於遙遠距離星系恒星年齡的真實比例，因為我們目前對係外恒星研究的唯一途徑是獲得它們的光譜資訊，如果對這些恒星光譜沒有深入假設分析，那麼無法得出銀河系的相關結論，比如那些恒星的品質以及年齡等資訊。

研究人員烏格斯·薩那認為本項研究表面大多數恒星是單一存在的假設可導致錯誤的結論，了解到“吸血鬼恒星”可以製造年輕恒星的假像之後，將改變我們對銀河系演變的看法。因此下一步將通過深入的研究形成“吸血鬼恒星”雙星系統的模型，雖然其是複雜的，但我們需要在將所有問題納入星系形成進行考量之前將“吸血鬼恒星”之謎揭開。

barying · 發表於 2012-7-30 04:16:08

科學家發現恐怖"吸血鬼太陽" 吮吸伴星物質為生

以上影片乃youtube提供,與本站無關; 若無法觀看,可查看原網址。

“吸血鬼太陽”可從伴星上汲取表面物質

LH54-425雙星系，其中包含了兩顆大品質恒星

據國外媒體報道，科學家發現太陽系之外的宇宙是非同尋常的空間，存在著許多與太陽截然不同的恒星。
一組由國際天文學家組成的研究小組通過位於智利的歐洲南方天文臺甚大望遠鏡（VLT）
觀測研究了一種被稱為O型主序星的恒星，這種罕見的恒星有著極高的溫度，品質和亮度。
O型主序星在星系演化的進程中扮演著重要作用。
此外，這種類型的恒星還與一種極端的宇宙事件相關聯，被科學家稱為“吸血鬼恒星”。

“吸血鬼恒星”是一個較小的伴星圍繞著一顆品質較大的恒星，並將其表面物質“悄無聲息”地吮吸掉。
根據位於荷蘭的阿姆斯特丹大學的研究人員烏格斯‧薩那（Hugues Sana）介紹：
“這些恒星完全是一個龐然大物，它們擁有十五倍甚至是更大的太陽品質，其亮度是太陽的百萬倍數量級。
吸血鬼恒星非常炙熱，併發出藍白色的光芒，其表面溫度超過了3萬攝氏度。”

國際天文學家小組研究的對象中包括了71顆O型主序星，以及它們的伴星，
發現的區域位於銀河系中的六個臨近太陽系的恒星團中。其中絕大多數的觀測由歐洲南方天文臺的望遠鏡完成，其中就包括甚大望遠鏡。
通過分析來自恒星團的光譜，科學家們發現了75%的型主序星存在於雙星系統中，這比之前研究觀測的結果具有更高的比例，這也是科學家們首次獲得如此精確的統計數字。
歐洲南方天文臺的甚大望遠鏡使得科學家們以前所未有的精度來觀測“吸血鬼恒星”。

更重要的是，吸血鬼恒星與其伴星之間的距離都靠得很近，
它們之間所發生的引力等相互作用形式比我們之前認為的要複雜，超出了我們的想像，
對理解星系演化構成了深遠的影響。我們一般將伴星中吸取對方表面物質的恒星稱為“吸血鬼恒星”。
雖然O型主序星在宇宙恒星世界中的比例較少，但是其往往與極端不尋常的宇宙事件相關聯，
對周圍的空間環境構成深遠的影響。

來自“吸血鬼恒星”的高能粒子風暴可衝擊恒星團並阻止恒星的形成，產生的輻射可使得周圍星雲發出明亮的輝光，
在發生超新星爆發後，攜帶的重元素對宇宙生命的出現起到了關鍵的作用。
此外，它們還與宇宙中發現的異常伽馬射線暴有關，該現象是宇宙中最具有“活力”的事件之一。
O型主序星也涉及到許多觸發星系演變的機制。

根據美國空間望遠鏡研究所的科學家、本項研究的合著者塞爾瑪‧德明科（Selma de Mink）介紹：
“如果在一顆恒星周圍存在另一個恒星，那麼前者的一生將受到這顆恒星的極大的影響。
如果兩顆恒星的軌道非常靠近，將導致兩者最終發生碰撞，即便兩顆恒星之間並未出現類似的現象，
那麼它們其中的一顆也將從其伴星上剝離表面物質。”

國際天文學家小組估計，恒星之間發生的碰撞合併現象大約由20%至30%是O型主序星，
如果是“吸血鬼恒星”的話，那麼這個數字將達到40%至50%，它們對恒星的演化構成較大影響。
但目前為止，大多數天文學家們認為距離極其相近並相互圍繞旋轉的恒星是例外事件，
類似的雙星系統一般解釋成X射線雙星、脈衝星雙星系統以及兩個黑洞構成的雙體問題。

最新的研究成果顯示重量級的雙星系統並不是常見的，由兩顆恒星構成的雙星世界行為方式與單顆恒星截然不同。
比如，吸血鬼恒星相比較于它那體積和品質更大的恒星，它卻可以將其表面物質剝離並吸附，
使得自己的品質大幅度增加，因此相比較于單顆恒星的演化，如果該情況可以完全無障礙演化下去，
那麼吸血鬼恒星的壽命比單恒星世界更長。

被“吸血鬼恒星”剝奪表面物質的伴星，在後者有機會變成紅巨星之前就會損失大量的品質，
取而代之的是暴露出炙熱、呈現藍色的核心。
這樣造成的結果是當我們觀測遙遠星系時，會發現更多呈現藍色恒星，
這意味著星系顯得更加地年輕，但真實情況卻不是。
吸收伴星物質後重新煥發活力的“吸血鬼恒星”與體積縮小變得更熱更藍的恒星將呈現出類似年輕恒星的假像。

initialcon · 發表於 2012-7-29 11:59:45

If there is an english version??

barying · 發表於 2012-7-30 04:18:27

回復 initialcon #2 的帖子

Here we go ~

A surprising number of massive stars in our Milky Way galaxy are part of close stellar duos, a new study finds, but most of these companion stars have turbulent relationships — with one "vampire star" sucking gas from the other, or the two stars violently merging to form a single star.

Astronomers using the European Southern Observatory's Very Large Telescope in Chile studied massive O-type stars, which are very hot and incredibly bright. These stars, which have surface temperatures of more than 54,000 degrees Fahrenheit (30,000 degrees Celsius) live short, violent lives, but they play key roles in the evolution of galaxies.

The researchers discovered that more than 70 percent of these massive stars have close companions, making up so-called binary systems in which two stars orbit each other.

While this percentage is far more than was previously expected, the astronomers were more surprised to find that majority of these stellar pairs have tumultuous relationships with one another, said study co-author Selma de Mink, of the Space Telescope Science Institute in Baltimore.

"We already knew that massive stars are very often in binaries," de Mink told SPACE.com. "What is very surprising to us is that they're so close, and such a large fraction is interacting. If a star has a companion so close next to it, it will have a very different evolutionary path. Before, this was very complicated for us to model, so we were hoping it was a minority of stars. But, if 70 percent of massive stars are behaving like this, we really need to change how we view these stars."

Type O stars drive galaxy evolution, but these stellar giants can also exhibit extreme behavior, garnering the nickname "vampire stars" for the way they suck matter from neighboring companions.

"These stars are absolute behemoths," study lead author Hugues Sana, of the University of Amsterdam in the Netherlands, said in a statement. "They have 15 or more times the mass of our sun and can be up to a million times brighter."

These massive stars typically end their lives in violent explosions, such as core-collapse supernovas or gamma-ray bursts, which are so luminous they can be observed throughout most of the universe.

For the new study, the astronomers analyzed the light coming from 71 O-type stars — a mix of single and binary stars — in six different star clusters, all located roughly 6,000 light-years away.

The researchers found that almost three-quarters of these stars have close companions. Most of these pairs are also close enough to interact with one another, with mass being transferred from one star to the other in a sort of stellar vampirism. About one-third of these binary systems are even expected to eventually merge to form a single star, the researchers said.

The results of the study indicate that massive stars with companions are more common than was once thought, and that these heavyweights in binary systems evolve differently than single stars — a fact that has implications for how scientists understand galaxy evolution.

"It makes a big difference for understanding the life of massive stars and how they impact the whole universe," said de Mink.

Big stars with a big impact

Type O stars make up less than 1 percent of the stars in the universe, but they have powerful effects on their surroundings. The winds and shocks from these stars can both trigger and halt star formation processes, the researchers said.

Over the course of their lives, culminating in the supernova explosions that signal their death, these massive stars also produce all the heavy elements in the universe. These elements enrich galaxies and are crucial for life.

But for massive stars in close binary systems, the interactions between the pair impact the evolution of both stars.

With vampire stars, the lower-mass star sucks fresh hydrogen from its companion, substantially increasing its mass and enabling it to live much longer than a single star of the same mass would, the researchers explained. The victim star, on the other hand, is left with an exposed core that mimics the appearance of a much younger star.

These factors could combine to give researchers misleading information about galaxies and the stars within them.

"The only information astronomers have on distant galaxies is from the light that reaches our telescopes," said Sana. "Without making assumptions about what is responsible for this light, we cannot draw conclusions about the galaxy, such as how massive or young it is. This study shows that the frequent assumption that most stars are single can lead to wrong conclusions."