File:Animation of cosmic distance ladder (heic1611a).webm

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Original file ‎(WebM audio/video file, VP8, length 30 s, 1,920 × 1,080 pixels, 623 kbps overall, file size: 2.23 MB)

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English: This animation shows the principle of the cosmic distance ladder used by Adam Riess and his team to reduce the uncertainty of the Hubble constant.

For the calibration of relatively short distances the team observed Cepheid variables. These are pulsating stars which fade and brighten at rates that are proportional to their true brightness and this property allows astronomers to determine their distances. The researchers calibrated the distances to the Cepheids using a basic geometrical technique called parallax. With Hubble’s sharp-eyed Wide Field Camera 3 (WFC3), they extended the parallax measurements further than previously possible, across the Milky Way galaxy. To get accurate distances to nearby galaxies, the team then looked for galaxies containing both Cepheids and Type Ia supernovae. Type Ia supernovae always have the same intrinsic brightness and are also bright enough to be seen at relatively large distances. By comparing the observed brightness of both types of stars in those nearby galaxies, the team could then accurately measure the true brightness of the supernova. Using this calibrated rung on the distance ladder the accurate distance to additional 300 type Ia supernovae in far-flung galaxies was calculated.

They compare those distance measurements with how the light from the supernovae is stretched to longer wavelengths by the expansion of space. Finally, they use these two values to calculate how fast the universe expands with time, called the Hubble constant.
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Source http://spacetelescope.org/videos/heic1611a/
Author NASA, ESA, A. Feild (STScI), and A. Riess (STScI/JHU)
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Date/TimeThumbnailDimensionsUserComment
current16:58, 18 May 201830 s, 1,920 × 1,080 (2.23 MB)ComputerHotline (talk | contribs)Imported media from https://cdn.spacetelescope.org/archives/videos/hd_1080p25_broadcast/heic1611a.avi

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Format Bitrate Download Status Encode time
VP9 1080P 569 kbps Completed 19:33, 17 August 2018 48 s
Streaming 1080p (VP9) 569 kbps Completed 18:56, 16 January 2024 1.0 s
VP9 720P 281 kbps Completed 19:33, 17 August 2018 36 s
Streaming 720p (VP9) 281 kbps Completed 13:14, 25 January 2024 1.0 s
VP9 480P 154 kbps Completed 19:33, 17 August 2018 28 s
Streaming 480p (VP9) 153 kbps Completed 05:32, 18 December 2023 1.0 s
VP9 360P 94 kbps Completed 19:32, 17 August 2018 19 s
Streaming 360p (VP9) 94 kbps Completed 09:00, 2 January 2024 1.0 s
VP9 240P 52 kbps Completed 19:32, 17 August 2018 16 s
Streaming 240p (VP9) 52 kbps Completed 04:29, 12 December 2023 1.0 s
WebM 360P 274 kbps Completed 16:58, 18 May 2018 14 s
Streaming 144p (MJPEG) 867 kbps Completed 07:50, 30 October 2023 3.0 s

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