Return to Video

How to weigh a star using gravitational lensing

  • 0:00 - 0:02
    Here's some exciting space news.
  • 0:02 - 0:04
    Astronomers have used the Hubble Telescope
  • 0:04 - 0:07
    and a technique pioneered by
  • 0:07 - 0:09
    Albert Einstein to weigh a white
  • 0:09 - 0:10
    dwarf star for the first time.
  • 0:10 - 0:13
    So in 1916, Einstein said that
  • 0:13 - 0:15
    a massive object like a star would
  • 0:15 - 0:17
    actually warp the fabric of spacetime
  • 0:17 - 0:20
    and what that means is that a ray of
  • 0:20 - 0:22
    light going past the star would actually
  • 0:22 - 0:24
    get bent and move in different paths
  • 0:24 - 0:25
    as it was before.
  • 0:25 - 0:29
    In 1936, a Czech engineer named Mandl
  • 0:29 - 0:31
    came knocking on Einstein's door and asked
  • 0:31 - 0:32
    him to do a little calculation.
  • 0:32 - 0:34
    He said what would happen if a star passed in front
  • 0:34 - 0:36
    of another star, and Einstein really
  • 0:36 - 0:38
    didn't want to do it. He was kind of busy but
  • 0:38 - 0:40
    he felt sorry for him and he did the
  • 0:40 - 0:42
    calculation and wrote a paper for Science,
  • 0:42 - 0:45
    very short paper saying if one star passed
  • 0:45 - 0:47
    in front of another star, the distant star
  • 0:47 - 0:50
    would be magnified and distorted by this
  • 0:50 - 0:52
    gravitational lensing effect. And today,
  • 0:52 - 0:55
    gravitational lensing is one of the most
  • 0:55 - 0:56
    powerful tools in astronomy. People use
  • 0:56 - 0:58
    it to measure the size of the universe and
  • 0:58 - 1:01
    to map out dark matter and to find distant
  • 1:01 - 1:03
    galaxies they couldn't find otherwise
  • 1:03 - 1:06
    because they were too dim. What people in
  • 1:06 - 1:09
    space telescope have done is watch as a
  • 1:09 - 1:12
    distant ordinary star passed behind a
  • 1:12 - 1:14
    white dwarf. It was distorted just as
  • 1:14 - 1:16
    Einstein said it would. And by looking at
  • 1:16 - 1:19
    the exact distortion, they were able to
  • 1:19 - 1:21
    calculate how much the white dwarf was
  • 1:21 - 1:23
    distorting spacetime and therefore,
  • 1:23 - 1:25
    what its mass was, which turned out to be
  • 1:25 - 1:27
    two-thirds of the mass of the Sun (more or less), which
  • 1:27 - 1:29
    is what the theory has said. But still,
  • 1:29 - 1:31
    it's good to know. So once more, we have
  • 1:31 - 1:33
    Einstein to thank for yet another discovery
  • 1:33 - 1:36
    even though he died way back in 1955.
  • 1:37 - 1:39
    This is Mike Lemonick for Scientific American.
  • 1:39 - 1:43
    Please take the time to subscribe to our
  • 1:43 - 1:43
    YouTube channel.
Tytuł:
How to weigh a star using gravitational lensing
Opis:

more » « less
Video Language:
English
Team:
Scientific American
Projekt:
Misc. Videos
Duration:
01:55

English, British subtitles

Revisions Compare revisions