File:A cosmological measuring tape.jpg

页面内容不支持其他语言。
這個文件來自維基共享資源
维基百科,自由的百科全书

原始文件(1,280 × 1,158像素,文件大小:247 KB,MIME类型:image/jpeg


摘要

描述
English: This NASA/ESA Hubble Space Telescope image shows the spiral galaxy NGC 3021 which lies about 100 million light-years away in the constellation of Leo Minor (The Little Lion). Among many other types of stars, this galaxy contains Cepheid variable stars, which can be used work out the distance to the galaxy. These stars pulsate at a rate that is closely related to their intrinsic brightness, so measurements of their rate of pulsation and their observed brightness give astronomers enough information to calculate the distance to the galaxy itself. Cepheids are also used to calibrate an even brighter distance marker, that can be used over greater distances: Type Ia supernovae. One of these bright exploding stars was observed in NGC 3021, back in 1995. In addition, the supernova in NGC 3021 was also used to refine the measurement of what is known as the Hubble constant. The value of this constant defines how fast the Universe is expanding and the more accurately we know it the more we can understand about the evolution of the Universe in the past as well as in the future. So, there is much more to this galaxy than just a pretty spiral.
日期
来源 http://www.spacetelescope.org/images/potw1513a/
作者 NASA & ESA / Acknowledgement: A. Riess (STScI)

许可协议

w:zh:知识共享
署名
署名
ESA/Hubble images, videos and web texts are released by the ESA under the Creative Commons Attribution 4.0 International license and may on a non-exclusive basis be reproduced without fee provided they are clearly and visibly credited. Detailed conditions are below; see the ESA copyright statement for full information. For images created by NASA or on the hubblesite.org website, or for ESA/Hubble images on the esahubble.org site before 2009, use the {{PD-Hubble}} tag.
Conditions:
  • The full image or footage credit must be presented in a clear and readable manner to all users, with the wording unaltered (for example: "ESA/Hubble"). Web texts should be credited to ESA/Hubble (except when used by media). The credit should not be hidden or disassociated from the image footage. Links should be active if the credit is online. See the usage rights Q&A section on the ESA copyright page for guidance.
  • ESA/Hubble materials may not be used to state or imply the endorsement by ESA/Hubble or any ESA/Hubble employee of a commercial product or service.
  • ESA/Hubble requests a copy of the product sent to them to be indexed in their archive.
  • If an image shows an identifiable person, using that image for commercial purposes may infringe that person's right of privacy, and separate permission should be obtained from the individual.
  • If images or visuals are changed significantly from the original work (apart from resizing, cropping), we suggest that the changes are mentioned after the credit line. For example "Original image by ESA/Hubble (M. Kornmesser), warping and recolouring by NN".

Notes:

  • Note that this general permission does not extend to the use of ESA/Hubble's logo, which shall remain protected and may not be used or reproduced without prior and individual written consent of ESA/Hubble.
  • Also note that music, scientific papers and code on the esahubble.org site are not released under this license and can not be used for non-ESA/Hubble products.
  • By reproducing ESA/Hubble material, in part or in full, the user acknowledges the terms on which such use is permitted.
w:zh:知识共享
署名
本文件采用知识共享署名 4.0 国际许可协议授权。
署名: ESA/Hubble
您可以自由地:
  • 共享 – 复制、发行并传播本作品
  • 修改 – 改编作品
惟须遵守下列条件:
  • 署名 – 您必须对作品进行署名,提供授权条款的链接,并说明是否对原始内容进行了更改。您可以用任何合理的方式来署名,但不得以任何方式表明许可人认可您或您的使用。

说明

添加一行文字以描述该文件所表现的内容

此文件中描述的项目

描繪內容

image/jpeg

288e7ccd4f830e0bfe20d6c2db7567ff662a04f5

253,294 字节

1,158 像素

1,280 像素

文件历史

点击某个日期/时间查看对应时刻的文件。

日期/时间缩⁠略⁠图大小用户备注
当前2015年4月10日 (五) 15:252015年4月10日 (五) 15:25版本的缩略图1,280 × 1,158(247 KB)JmencisomUser created page with UploadWizard

以下2个页面使用本文件:

全域文件用途

以下其他wiki使用此文件:

元数据