另眼系列之M81

来源:http://gallery.spitzer.caltech.e ... mage_name=sig07-009

http://hubblesite.org/newscenter/archive/releases/2007/19/image/j/

Multiwavelength M81
This beautiful galaxy is tilted at an oblique angle on to our line of sight, giving a "birds-eye view" of the spiral structure. The galaxy is similar to our Milky Way, but our favorable view provides a better picture of the typical architecture of spiral galaxies.

M81 may be undergoing a surge of star formation along the spiral arms due to a close encounter it may have had with its nearby spiral galaxy NGC 3077 and a nearby starburst galaxy (M82) about 300 million years ago.

M81 is one of the brightest galaxies that can be seen from the Earth. It is high in the northern sky in the circumpolar constellation Ursa Major, the Great Bear. At an apparent magnitude of 6.8 it is just at the limit of naked-eye visibility. The galaxy's angular size is about the same as that of the Full Moon.

This image combines data from the Hubble Space Telescope, the Spitzer Space Telescope, and the Galaxy Evolution Explorer (GALEX) missions. The GALEX ultraviolet data were from the far-UV portion of the spectrum (135 to 175 nanometers). The Spitzer infrared data were taken with the IRAC 4 detector (8 microns). The Hubble data were taken at the blue portion of the spectrum.

                               
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[ 本帖最后由 寻找拉玛 于 2008-2-11 22:25 编辑 ]

6MB大图.这是分卷压缩需要全部下载,才可以解压.

[ 本帖最后由 寻找拉玛 于 2008-2-9 14:13 编辑 ]

这个用来桌面很合适，震撼大图。这是分卷压缩需要全部下载,才可以解压.

[ 本帖最后由 寻找拉玛 于 2008-2-9 14:13 编辑 ]

来源:http://gallery.spitzer.caltech.e ... ge_name=ssc2003-06d

Messier 81The magnificent spiral arms of the nearby galaxy Messier 81 are highlighted in this image from NASA's Spitzer Space Telescope. Located in the northern constellation of Ursa Major (which also includes the Big Dipper), this galaxy is easily visible through binoculars or a small telescope. M81 is located at a distance of 12 million light-years.

The main image is a composite mosaic obtained with the multiband imaging photometer and the infrared array camera. Thermal infrared emission at 24 microns detected by the photometer (red, bottom left inset) is combined with camera data at 8.0 microns (green, bottom center inset) and 3.6 microns (blue, bottom right inset).

A visible-light image of Messier 81, obtained with a ground-based telescope at Kitt Peak National Observatory, is shown in the upper right inset. Both the visible-light picture and the 3.6-micron near-infrared image trace the distribution of stars, although the Spitzer image is virtually unaffected by obscuring dust. Both images reveal a very smooth stellar mass distribution, with the spiral arms relatively subdued.

As one moves to longer wavelengths, the spiral arms become the dominant feature of the galaxy. The 8-micron emission is dominated by infrared light radiated by hot dust that has been heated by nearby luminous stars. Dust in the galaxy is bathed by ultraviolet and visible light from nearby stars. Upon absorbing an ultraviolet or visible-light photon, a dust grain is heated and re-emits the energy at longer infrared wavelengths. The dust particles are composed of silicates (chemically similar to beach sand), carbonaceous grains and polycyclic aromatic hydrocarbons and trace the gas distribution in the galaxy. The well-mixed gas (which is best detected at radio wavelengths) and dust provide a reservoir of raw materials for future star formation.

The 24-micron multiband imaging photometer image shows emission from warm dust heated by the most luminous young stars. The infrared-bright clumpy knots within the spiral arms show where massive stars are being born in giant H II (ionized hydrogen) regions. Studying the locations of these star forming regions with respect to the overall mass distribution and other constituents of the galaxy (e.g., gas) will help identify the conditions and processes needed for star formation.

来源:http://gallery.spitzer.caltech.e ... ge_name=ssc2003-06c

Messier 81The magnificent spiral arms of the nearby galaxy Messier 81 are highlighted in this NASA Spitzer Space Telescope image. Located in the northern constellation of Ursa Major (which also includes the Big Dipper), this galaxy is easily visible through binoculars or a small telescope. M81 is located at a distance of 12 million light-years.

Because of its proximity, M81 provides astronomers with an enticing opportunity to study the anatomy of a spiral galaxy in detail. The unprecedented spatial resolution and sensitivity of Spitzer at infrared wavelengths show a clear separation between the several key constituents of the galaxy: the old stars, the interstellar dust heated by star formation activity, and the embedded sites of massive star formation. The infrared images also permit quantitative measurements of the galaxy's overall dust content, as well as the rate at which new stars are being formed.

The infrared image was obtained by Spitzer's infrared array camera. It is a four-color composite of invisible light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (yellow) and 8.0 microns (red). Winding outward from the bluish-white central bulge of the galaxy, where old stars predominate and there is little dust, the grand spiral arms are dominated by infrared emission from dust. Dust in the galaxy is bathed by ultraviolet and visible light from the surrounding stars. Upon absorbing an ultraviolet or visible-light photon, a dust grain is heated and re-emits the energy at longer infrared wavelengths. The dust particles, composed of silicates (which are chemically similar to beach sand) and polycyclic aromatic hydrocarbons, trace the gas distribution in the galaxy. The well-mixed gas (which is best detected at radio wavelengths) and dust provide a reservoir of raw materials for future star formation.

The infrared-bright clumpy knots within the spiral arms denote where massive stars are being born in giant H II (ionized hydrogen) regions. The 8-micron emission traces the regions of active star formation in the galaxy. Studying the locations of these regions with respect to the overall mass distribution and other constituents of the galaxy (e.g., gas) will help identify the conditions and processes needed for star formation. With the Spitzer observations, this information comes to us without complications from absorption by cold dust in the galaxy, which makes interpretation of visible-light features uncertain.

The white stars scattered throughout the field of view are foreground stars within our own Milky Way galaxy.

来源:http://dirty.as.arizona.edu/~kgordon/m81_ero/m81_ero.html

[ 本帖最后由 寻找拉玛 于 2008-2-9 14:24 编辑 ]

来源:http://www.cv.nrao.edu/course/astr534/HILine.html

[ 本帖最后由 寻找拉玛 于 2008-2-9 14:27 编辑 ]

原帖由 benlinliu 于 2008-2-9 14:41 发表

                               
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如果可能,请LAMOST列计划,细致观测"暗"旋臂,回答以下四个问题

是不是在"暗"旋臂存在X射线源?

在上述X射线源中,有X射线点源吗?

上述点源有多少?

这些点源是不是有旋臂状分布? ...

先打住, 别忙"列计划".
LS知道LAMOST的观测波段吧! 先谈谈你的逻辑 LAMOST 的观测如何能发现X射线源呢? 让我等学习学习先

辛苦辛苦

图很精彩！看到M81的许多细节了，非常好！

我滴妈呀
第一张太漂亮了！

感觉非常震撼 好图 !~