Thành viên:Unpear/Sự va chạm giữa Ngân Hà và Andromeda

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Sự va chạm giữa Ngân Hà và Andromeda là một dự đoán về va chạm thiên hà có thể xảy ra trong khoảng 4.5 tỉ năm giữa hai thiên hà lớn nhất trong Nhóm Địa Phương – Thiên hà Andromeda và Ngân Hà, thiên hà chứa Trái Đất.[1][2]

Giả thuyết[sửa | sửa mã nguồn]

Nó thường được sử dùng như là một ví dụ về một loại hiện tượng liên quan đến va chạm trong các cuộc mô phỏng.[3] Như các vụ va chạm cùng loại, nó không có nghĩa rằng các ngôi sao nằm trong các thiên hà thực sự đâm vào nhau, as galaxies are in fact very diffuse—the nearest star to the Sun is in fact almost thirty million solar diameters away from the Earth. (If the sun were scaled to the size of an American quarter (a small coin), 24.26 mm (0.955 in), the next closest quarter/star would be 700 km [475 miles] away.) If the collision occurs, the galaxies will likely merge into one larger galaxy.

Uncertainty[sửa | sửa mã nguồn]

There is, as yet, no way to know whether the possible collision is definitely going to happen or not. The radial velocity of the Andromeda galaxy with respect to the Milky Way can be measured by examining the Doppler shift of spectral lines from stars in the galaxy, but the transverse velocity cannot be directly measured. Thus, while it is known that the Andromeda galaxy is getting closer to the Milky Way by about 120 km/s, there is no way to tell whether it is going to collide or miss. The best indirect estimates of the transverse velocity indicate that it is less than 100 km/s.[4] This suggests that the dark matter halos, although possibly not the actual disks, of the galaxies will collide. A future European Space Agency spacecraft, the Gaia mission, expected to launch in the Spring of 2012, is intended to measure the positions of stars in the Andromeda galaxy with sufficient precision to pin down the transverse velocity.[1]

Frank Summers of the Space Telescope Science Institute has created a CGI visualization of the predicted event, based on research by Professors Chris Mihos of Case Western Reserve University and Lars Hernquist of Harvard University.[5]

Such collisions are relatively common, however. Andromeda, for example, is believed to have collided with at least one other galaxy in the past,[6] and several dwarf galaxies such as SagDEG are currently colliding with the Milky Way and being merged into it.

The fate of the Solar System[sửa | sửa mã nguồn]

Two scientists with the Harvard-Smithsonian Center for Astrophysics stated that when, and even whether, the two galaxies collide depend on Andromeda's sideways speed.[1] Based on current calculations they predict a 50% chance that in a merged galaxy the solar system will be swept out three times farther from the galactic core than it is currently located.[1] They also predict a 12% chance that the Solar System will be ejected from the new galaxy some time during the collision.[7] Such an event would have no adverse effect on the system and chances of any sort of disturbance to the Sun or planets themselves may be remote.[7][8]

Without intervention, by the time that the two galaxies collide, the surface of the Earth will have already become far too hot for liquid water to exist, ending all terrestrial life, which is currently estimated to occur in about 1 billion years due to gradually increasing warmth of the Sun.[9][10] (See also: Stellar evolution)

See also[sửa | sửa mã nguồn]

References[sửa | sửa mã nguồn]

  1. ^ a b c d Hazel Muir, "Galactic merger to 'evict' Sun and Earth," New Scientist 4 May 2007
  2. ^ Astronomy, June 2008, page 28, by Abraham Loeb and T. J. Cox
  3. ^ “Andromeda Galaxy May Steal Our Solar System From Milky Way”.
  4. ^ Abraham Loeb, Mark J. Reid, Andreas Brunthaler, and Heino Falcke The Astrophysical Journal, 633:894–898, November 10, 2005
  5. ^ Hubblesite Newscenter: Hubble Astronomer Creates Spectacular Galaxy Collision Visualization for the National Air and Space Museum
  6. ^ "Andromeda involved in galactic collision" MSNBC 10:38 a.m. PT 29 January 2007
  7. ^ a b Cain, Fraser (2007). “When Our Galaxy Smashes Into Andromeda, What Happens to the Sun?”. Universe Today. Truy cập ngày 16 tháng 5 năm 2007.
  8. ^ Cox, T. J.; Loeb, Abraham (2007). “The Collision Between The Milky Way And Andromeda”. Monthly Notices of the Royal Astronomical Society. 386: 461. doi:10.1111/j.1365-2966.2008.13048.x. arXiv:0705.1170.Quản lý CS1: nhiều tên: danh sách tác giả (liên kết)
  9. ^ Schröder, K.-P.; Smith, R.C. (2008). “Distant future of the Sun and Earth revisited”. Monthly Notices of the Royal Astronomical Society. 386 (1): 155. doi:10.1111/j.1365-2966.2008.13022.x. arXiv:0801.4031.
  10. ^ Carrington, D. (21 tháng 2 năm 2000). “Date set for desert Earth”. BBC News. Truy cập ngày 31 tháng 3 năm 2007.Quản lý CS1: ngày tháng và năm (liên kết)

Bibliography[sửa | sửa mã nguồn]

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