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How to weigh a star using gravitational lensing

  • 0:00 - 0:02
    Here is some exciting space news.
  • 0:02 - 0:04
    Astronomers have used the Hubble Telescope
  • 0:04 - 0:07
    and a technique pioneered
    by Albert Einstein
  • 0:07 - 0:10
    to weigh a white dwarf star
    for the first time.
  • 0:10 - 0:15
    So in 1916, Einstein says
    that a massive object like a star
  • 0:15 - 0:18
    would actually warp
    the fabric of spacetime.
  • 0:18 - 0:21
    What that means is that a ray of light
    going past the star
  • 0:21 - 0:24
    would actually get bent
    and move in a different path
  • 0:24 - 0:26
    as it was before.
  • 0:26 - 0:29
    In 1936, a Czech engineer named Mandl
  • 0:29 - 0:30
    came knock on Einstein's door
  • 0:30 - 0:32
    and asked him to do
    a little calculation.
  • 0:32 - 0:35
    He said, "What if a star passed
    in front of another star?"
  • 0:35 - 0:37
    Einstein really didn't want to do it.
  • 0:37 - 0:39
    He was kinda busy
    but he felt sorry for him
  • 0:39 - 0:40
    and he did the calculation
  • 0:40 - 0:42
    and wrote a paper for Science,
  • 0:42 - 0:44
    a very short paper saying
  • 0:44 - 0:47
    if one star passed
    in front of another star,
  • 0:47 - 0:49
    the distant star would be
    magnified and distorted
  • 0:49 - 0:51
    by this gravitational lensing effect.
  • 0:52 - 0:55
    Today, gravitational lensing is one
    of the most powerful tools in astronomy.
  • 0:55 - 0:58
    People use it to measure
    the size of the universe
  • 0:58 - 1:02
    and to map out dark matter
    and to find distant galaxies
  • 1:02 - 1:03
    they couldn't find otherwise
  • 1:03 - 1:05
    because were too dim.
  • 1:05 - 1:08
    What people in space telescope have done
  • 1:08 - 1:12
    is watch as a distant ordinary star
    passed behind a white dwarf.
  • 1:12 - 1:15
    It was distorted just
    as Einstein said it would.
  • 1:15 - 1:18
    And by looking at the exact distortion,
  • 1:18 - 1:20
    they were able to calculate
  • 1:20 - 1:22
    how much the white dwarf
    was distorting spacetime
  • 1:22 - 1:24
    and therefore, what it mass was
  • 1:24 - 1:26
    which turned out to be
    2/3 of the mass of the Sun
  • 1:26 - 1:28
    (more or less), as the theory has said.
  • 1:28 - 1:30
    But still, it's good to know.
  • 1:30 - 1:32
    So once more, we have Einstein to thank
  • 1:32 - 1:34
    for yet another discovery
  • 1:34 - 1:37
    even though he died way back in 1955.
  • 1:38 - 1:40
    This is Mike Lemonick
    for Scientific American
  • 1:40 - 1:43
    Please take the TIME
    to subscribe to our Youtube channel.
Tytuł:
How to weigh a star using gravitational lensing
Opis:

Astronomers recently tapped Einstein's concept of gravitational lensing to determine the weight of a distant star. Watch and learn how this concept came to be and how it works.

Subscribe to our channel! https://www.youtube.com/SciAmerican

Transcript:
Here's some exciting space news, astronomers have used the Hubble Telescope and a technique pioneered by Albert Einstein to weigh a white dwarf star for the first time. So in 1916, Einstein said that a massive object like a star would actually warp the fabric of space-time, and what that means is that a ray of light going past the star would actually get bent and move in a different path than it was before. In 1936, a Czech engineer named Mandl came and knocked on Einstein's door and asked him to do a little calculation. He said, "What would happen if a star passed in front of another star?" And Einstein really didn't want to do it. He was kind of busy, but he felt sorry for him and he did the calculation and wrote a paper for Science. A very short paper saying: if one star passed in front of another star, the distant star would be magnified and distorted by this gravitational lensing effect. And today, gravitational lensing is one of the most powerful tools in astronomy. People use it to measure the size of the universe and to map out dark matter and to find distant galaxies they couldn't find otherwise because they were too dim. What people at space telescope have done is watch as a distant ordinary star passed behind a white dwarf. It was distorted just as Einstein said it would and by looking at the exact distortion they were able to calculate how much the white dwarf was distorting space-time and therefore what its mass was. Which turns out to be 2/3 the mass of the Sun, more or less, which is what the theory said but still, it's good to know. So once more, we have Einstein to thank for yet another discovery even though he died way back in 1955.
This is Mike Lemonick for Scientific American. Please take the time to subscribe to our YouTube channel.

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Video Language:
English
Team:
Scientific American
Projekt:
Misc. Videos
Duration:
01:55

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