M51：哈勃的涡状星系影像

M51：哈勃的涡状星系影像

ByNASA中文

2022年6月13日 M51: The Whirlpool Galaxy from Hubble Image Credit: NASA, ESA, Hubble, HLA; Processing & Copyright: Bernard Miller Explanation: The Whirlpool Galaxy is a classic spiral galaxy. At only 30 million light years distant and fully 60 thousand light years across, M51, also known as NGC 5194, is one of the brightest and most picturesque galaxies on the sky. The featured image is a digital combination of images taken in different colors by the Earth-orbiting Hubble Space Telescope, highlighting many sharp features. Anyone with a good pair of binoculars, however, can see this Whirlpool toward the constellation of the Hunting Dogs (Canes Venatici). M51 is a spiral galaxy of type Sc and is the dominant member of a whole group of galaxies. Astronomers speculate that…

涡状星系的磁场

涡状星系的磁场

ByNASA中文

2021年01月20日 The Magnetic Field of the Whirlpool Galaxy Image Credit: NASA, SOFIA, HAWC+, Alejandro S. Borlaff; JPL-Caltech, ESA, Hubble; Text: Jayanne English (U. Manitoba) Explanation: Do magnetic fields always flow along spiral arms? Our face-on view of the Whirlpool Galaxy (M51) allows a spectacularly clear view of the spiral wave pattern in a disk-shaped galaxy. When observed with a radio telescope, the magnetic field appears to trace the arms’ curvature. However, with NASA’s flying Stratospheric Observatory for Infrared Astronomy (SOFIA) observatory, the magnetic field at the outer edge of M51’s disk appears to weave across the arms instead. Magnetic fields are inferred by grains of dust aligning in one direction and acting like polaroid glasses on infrared light. In the featured image, the field orientations…

M33：三角星系

M33：三角星系

ByGotthew

2019 December 31 M33: The Triangulum Galaxy Image Credit & Copyright: Rui Liao Explanation: The small, northern constellation Triangulum harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy. M33 is over 50,000 light-years in diameter, third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the Andromeda Galaxy and astronomers in these two galaxies would likely have spectacular views of each other’s grand spiral star systems. As for the view from planet Earth, this sharp image shows off M33’s blue star clusters and pinkish star forming regions along the galaxy’s…

M27: 不是彗星

M27: 不是彗星

ByNASA中文

2019 August 29 M27: Not a Comet Image Credit & Copyright: Bob Franke Explanation: While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would identify it as a planetary nebula, but it’s not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star’s outer layers are expelled into space, with a visible glow generated by…

斯皮策“眼里”的漩涡星系

斯皮策“眼里”的漩涡星系

ByNASA中文

不同波长的光能够揭示天体的不同特征。最左边是漩涡星系（Whirlpool galaxy）的可见光图像，第二张结合了可见光和红外光，而右边的两个图像对应不同波长的红外光。 Credits: NASA/JPL-Caltech 加入了NASA斯皮策太空望远镜（Spitzer Space Telescope）的观测，这个星系的不同色调记录了它从可见光到红外光下的外观变化。 漩涡星系（又名Messier 51或NGC 5194/5195）实际上是一对相互作用的星系，它们通过引力互相吸引、拉扯扭曲。它距离我们大约2300万光年，位于猎犬座（Canes Venatici）。 最左边的图像（a）显示了可见光下的漩涡星系，就像我们的眼睛可以通过强大的望远镜看到它一样。事实上，这张照片来自基特峰国家天文台（Kitt Peak National Observatory）的2.1米望远镜。螺旋臂（spiral arms）上系着深色的尘埃，散发出很少的可见光并掩盖其中/后面的星光。 左二（b）包括来自基特峰的两个可见光波长（蓝色和绿色）以及来自斯皮策的红外数据（红色）。在可见光下阻挡我们视线的尘埃在这些较长的红外波长下开始发光。 斯皮策的全红外视图可以在右侧两个图像中看到，它们覆盖了略微不同的红外光范围。 第三张图（c）包括三种红外波长：3.6微米（以蓝色显示）、4.5微米（绿色）、和8微米（红色）。来自漩涡星系数十亿颗恒星的混合光在较短的红外波长下最亮，就是这里的蓝色薄雾。图像上的蓝点主要是近处的恒星和一些遥远的星系。红色的部分显示的是主要由碳组成的尘埃，它们被星系中的恒星照亮。 通过这些发光的尘埃，天文学家们可以了解恒星之间密集气体的分布。在可见光或红外光下很难看到密集的气体云，但它们总存在于有尘埃的地方。 最后一张（d）扩展了红外视图，加入了24微米（红色，去掉了4.5微米）的光，这可以强调尘埃温度高的区域。明亮、发红的白色斑点描绘出新恒星形成的区域，此过程会加热周围环境。 螺旋星系的红外视图也显示了它的两个组成部分的巨大差异：主螺旋星系中很明显有尘埃，而图像顶部较小的伴星系几乎没有尘埃特征。我们可以看到有微弱的蓝色薄雾围绕上面的星系，这可能是在两个星系近距离相互作用的过程中抛出恒星的光。 有关斯皮策的更多信息，请访问： www.nasa.gov/spitzer and www.spitzer.caltech.edu