【转载】新研究发现银河系更大旋转速度更快(图)
银河系模型新浪科技讯 北京时间1月6日消息，据国外媒体报道，数十年来，天文学家一直认为，在有关地球附近质量庞大的星系问题上，我们的银河系在仙女座星系面前充其量只是“小妹妹”的角色。但最新一项研究发现彻底颠覆了这种看法，因为实际情况是银河系比仙女座星系更大、更重、旋转速度更快。
天文学家日前绘制了一幅更为详细的银河系三维立体图，发现它的宽度比天文学家以前认为的多15%。更为重要的是，银河系的密度更大，质量比天文学家以前认为的多50%。天文学家1月5日在加州长滩市举行的美国天文学会大会上公布了这一最新发现。
实施这项研究的哈佛-史密森天体物理研究中心天体物理学家马克·雷德说，这种差异对我们意义重大。雷德身高5英尺5英寸(约合1.65米)，体重140磅，他举了一个形象的例子来说明这种差异：这就好比他忽然间变成了一个身高6英尺3英寸(约合1.91米)、体重达210磅的美式橄榄球联盟线卫球员。
雷德说：“以前，我们认为仙女座鹤立鸡群，银河系只是仙女座的小妹妹。但现在，仙女座更像是银河系的异卵双胞胎。”这并不见得就是一个好消息。银河系更大意味着它暴力撞击邻近仙女座星系的时间可能早于天文学家以前预测——尽管距离现在还有数十亿年之遥。
雷德及同事利用由10台射电望远镜天线组成的阵列，在地球绕太阳运转的不同时间测量银河系中最明显的新生恒星。他们绘制出这些恒星的图谱，图中不仅有我们首次看到它们的地方，而且以时间的第三维绘制——雷德说这是前所未见的。
借助这一点，雷德就能够确定螺旋形银河系绕其中心旋转的速度——大约每小时56.8万英里，这一速度快于科学家过去数十年认为的49.2万英里。这意味着银河系旋转速度比以前认为的增长15%。雷德说，过去的数字基于相对不精确的测量数据，而这次则基于实实在在的观测。
一旦确定了银河系旋转速度，那么最终控制这一速度的复杂公式便可确定银河系中所有暗物质的质量。暗物质是我们肉眼所看不到的，但却是迄今为止宇宙中数量最多的物质。所以，这意味着银河系的质量是天文学家以前估计的1.5倍。美国加州大学洛杉矶分校天体物理学家马克·莫里斯说，最新发现意义重大，但并不是有关银河系大小的最终结论。
莫里斯没有参加雷德的这项研究。体积更大还意味着银河系和仙女座之间的引力更加强烈。据雷德介绍，天文学家长期预测的银河系和仙女座星系之间的碰撞可能发生得更早，同时侧面碰撞的可能性更小，然而不用担心，毕竟银河系距离仙女座至少有20亿至30亿年远。(孝文） 非常大的改变呀。。。若干年后银河暴击仙女。。。后代们那时应该能超越III级文明，冲出银河系了吧。。。 LS的观点很乐观,悲观一点也有可能那时人类已经不存在了~::070821_15.jpg:: 本帖最后由 deepgreen 于 2009-1-6 13:45 编辑
据计算每级文明之间的能源利用率相差100亿倍，目前人类处于0.7级文明状态，从0到I级文明的过程是最为艰难的，如果能够顺利达到I级文明，没有自我毁灭掉，以后还是大有希望的。人类一旦真正离开地球，到处开花撒种，迟早会像蚂蚁一般，遍银河甚至遍宇宙是人吧。。。 每次AAS会议都会有很多抓眼球的新闻发布会，这些新东西未必一定正确，在写入教科书前，需要更多的独立的多方位检验确证。 遍银河甚至遍宇宙是人吧。。。
这个太恐怖了,宇宙还是不要有那么多人才会一直这么美丽吧~~::070821_12.jpg:: 本帖最后由 Hawl 于 2009-1-6 20:30 编辑
LS的观点很乐观,悲观一点也有可能那时人类已经不存在了~::070821_15.jpg::
一分半 发表于 2009-1-6 13:38 http://www.astronomy.com.cn/bbs/images/common/back.gif
::070821_15.jpg::
这话说的...::070821_18.jpg::
囧... 银河系太神奇了，好像来一次银河系旅行。 Triple Whammy: Milky Way More Massive, Spinning Faster and More Likely to Collide
For many of us, looking closely in the mirror and stepping on the bathroom scale just after the holidays can reveal a substantial surprise. Likewise, astronomers looking closely at the Milky Way have found our galaxy is more massive than previously thought. High-precision measurements of the Milky Way disclose our galaxy is rotating about 100,000 miles per hour faster than previously understood. That increase in speed, said Mark Reid of the Harvard-Smithsonian Center for Astrophysics, increases the Milky Way’s mass by 50 percent. The larger mass, in turn, means a greater gravitational pull that increases the likelihood of collisions with the Andromeda galaxy or smaller nearby galaxies. So even though we're faster, we're also heavier and more likely to be annihilated. Bummer!
The scientists are using the National Science Foundation’s Very Long Baseline Array (VLBA) radio telescope to remake the map of the Milky Way. Taking advantage of the VLBA’s unparalleled ability to make extremely detailed images, the team is conducting a long-term program to measure distances and motions in our Galaxy. At the American Astronomical Society’s meeting in Long Beach, California, Reid said they are using trigonometric parallax to make the measurements. "This is exactly what surveyors use on Earth to measure distances," he said. "And this is gold standard of measurement in astronomy."
Trigonometric parallax was first used in 1838 to measure the first stellar distance. However, with better technology, the accuracy is now about 10,000 times greater.
Our solar system is about 28,000 light-years from the Milky Way’s center. At that distance, the new observations indicate, we’re moving at about 600,000 miles per hour in our Galactic orbit, up from the previous estimate of 500,000 miles per hour.
The scientists observed 19 regions of prolific star formation across the Galaxy. In areas within these regions, gas molecules are strengthening naturally-occurring radio emission in the same way that lasers strengthen light beams. These areas, called cosmic masers, serve as bright landmarks for the sharp radio vision of the VLBA. By observing these regions repeatedly at times when the Earth is at opposite sides of its orbit around the Sun, the astronomers can measure the slight apparent shift of the object’s position against the background of more distant objects.
The astronomers found that their direct distance measurements differed from earlier, indirect measurements, sometimes by as much as a factor of two. The star-forming regions harboring the cosmic masers “define the spiral arms of the Galaxy,” Reid explained. Measuring the distances to these regions thus provides a yardstick for mapping the Galaxy’s spiral structure.
The star forming regions are shown in the green and blue dots on the image above. Our sun (and us!) are where the red circle is located.
The VLBA can fix positions in the sky so accurately that the actual motion of the objects can be detected as they orbit the Milky Way’s center. Adding in measurements of motion along the line of sight, determined from shifts in the frequency of the masers’ radio emission, the astronomers are able to determine the full 3-dimensional motions of the star-forming regions. Using this information, Reid reported that “most star-forming regions do not follow a circular path as they orbit the Galaxy; instead we find them moving more slowly than other regions and on elliptical, not circular, orbits.”
The researchers attribute this to what they call spiral density-wave shocks, which can take gas in a circular orbit, compress it to form stars, and cause it to go into a new, elliptical orbit. This, they explained, helps to reinforce the spiral structure.
Reid and his colleagues found other surprises, too. Measuring the distances to multiple regions in a single spiral arm allowed them to calculate the angle of the arm. “These measurements,” Reid said, “indicate that our Galaxy probably has four, not two, spiral arms of gas and dust that are forming stars.” Recent surveys by NASA’s Spitzer Space Telescope suggest that older stars reside mostly in two spiral arms, raising a question of why the older stars don't appear in all the arms. Answering that question, the astronomers say, will require more measurements and a deeper understanding of how the Galaxy works.
So, now that we know we're more massive, how do we compare with other galaxies in our neighborhood? "In our local group of galaxies, Andromeda was thought to be the dominant big sister," said Reid at the conference, "but we're basically equal in size and mass. We're not identical twins, but more like fraternal twins. And its likely the two galaxies will collide sooner than we thought, but it depends on a measurement of the sideways motion, which hasn't been done yet."
The VLBA is a system of 10 radio-telescope antennas stretching from Hawaii to New England and the Caribbean. It has the best resolving power, of any astronomical tool in the world. The VLBA can routinely produce images hundreds of times more detailed than those produced by the Hubble Space Telescope. The VLBA’s tremendous resolving power, equal to being able to read a newspaper in Los Angeles from the distance of New York, is what permits the astronomers to make precise distance determinations.
Source: AAS, Harvard-Smithsonian Center for Astrophysics
来篇原汁原味的。 本帖最后由 smile123 于 2009-1-8 05:24 编辑
9# q5968661
"...The scientists observed 19 regions of prolific star formation across the Galaxy..."
Just curious about what these 19 regions are, I dug around in astro-ph and found some interesting things:
5 papers I found are listed below:
1. arXiv:0811.0713 [ps, pdf, other]Title: Trigonometric Parallaxes of Massive Star Forming Regions: V. G23.01-0.41and G23.44-0.18
Authors: A. Brunthaler (1), M. J. Reid (2), K. M. Menten (1), X. W. Zheng (3), L. Moscadelli (4), Y. Xu(1,5) ((1) Max-Planck-Institut fuer Radioastronomie, (2)Harvard-Smithsonian Center for Astrophysics, (3) Nanjing University,(4) Osservatorio Astrofisico di Arcetri, (5) Purple MountainObservatory)
Comments: The Astrophysical Journal, accepted, 14 pages, 6 Figures, alsoavailable at this http URL
Subjects: Astrophysics (astro-ph)
2. arXiv:0811.0704 [ps, pdf, other]Title: Trigonometric Parallaxes of Massive Star Forming Regions: IV.G35.20-0.74 and G35.20-1.74
Authors: B. Zhang, X. W. Zheng, M. J. Reid, K. M. Menten, Y. Xu, L. Moscadelli, A. Brunthaler
Comments: 16 pages, 8 figures
Subjects: Astrophysics (astro-ph)
3. arXiv:0811.0701 [ps, pdf, other]Title: Trigonometric Parallaxes of Massive Star Forming Regions: III. G59.7+0.1and W 51 IRS2
Authors: Y. Xu, M. J. Reid, K. M. Menten, A. Brunthaler, X. W. Zheng, L. Moscadelli
Comments: 16 pages, 6 figures; to appear in the Astrophysical Journal
Subjects: Astrophysics (astro-ph)
4. arXiv:0811.0679 [ps, pdf, other]Title: Trigonometric Parallaxes of Massive Star Forming Regions: II. Cep A &NGC 7538
Authors: L. Moscadelli, M. J. Reid, K. M. Menten, A. Brunthaler, X. W. Zheng, Y. Xu
Comments: 21 pages, 8 figures; to appear in the Astrophysical Journal
Subjects: Astrophysics (astro-ph)
5. arXiv:0811.0595 [ps, pdf, other]Title: Trigonometric Parallaxes of Massive Star Forming Regions: I. S 252 &G232.6+1.0
Authors: M. J. Reid, K. M. Menten, A. Brunthaler, X. W. Zheng, L. Moscadelli, Y. Xu
Comments: 30 pages, 8 figures; to appear in the Astrophysical Journal
Subjects: Astrophysics (astro-ph)
NOTE: the 1st authors of paper 2 and 3 are CHINESES, and the papers are (partially) funded by NSF of China! 本帖最后由 deepgreen 于 2009-1-8 05:48 编辑
这几人厉害呀，轮着当第一作者，再多弄几个region，全部都能PhD混毕业了吧，教授们项目资金也能继续流水般进来（如果有的话）。。。
不知那些prolific star formation regions是如何选定的，手头的一套HANDBOOK OF STAR FORMING REGIONS里倒是至少列举了百来个STAR FORMING REGIONS。 非常大的改变呀。。。若干年后银河暴击仙女。。。后代们那时应该能超越III级文明，冲出银河系了吧。。。
deepgreen 发表于 2009-1-6 13:26 http://www.astronomy.com.cn/bbs/images/common/back.gif
兄台玩过“孢子”这个游戏吗？ 图图当中怎么有颗小雪花ya ~
兄台玩过“孢子”这个游戏吗？
xuanyuan14.leo 发表于 2009-1-8 11:50 http://www.astronomy.com.cn/bbs/images/common/back.gif
下载了，不过机子太破玩不动。。。
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