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Could a star be powered by a black hole at its center?

A black hole inside a vast envelope of gas sounds like a contradiction: what could keep the gas from simply falling in? Quasistar models explore how energy released by accretion outside the event horizon could support such an envelope.

5–7 min

Questions you could explore

  • Where would the energy be released if light cannot escape from inside the event horizon?
  • How does matter falling toward a black hole differ from energy escaping from inside its event horizon?

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Space

A crescent Moon is not a partly switched-off Moon

Sunlight illuminates half the Moon, while its changing position around Earth changes how much of that lit half we can see. A phase is different from an eclipse, where one body blocks light from reaching another.

3–5 min

A crescent Moon is not a partly switched-off Moon

Space3–5 minSunlight illuminates half the Moon, while its changing position around Earth changes how much of that lit half we can see. A phase is different from an eclipse, where one body blocks light from reaching another.

Space

Two eclipses, two different shadows

A solar eclipse and a lunar eclipse both involve the Sun, Earth, and Moon, but the shadow falls in a different place. In one, the Moon’s shadow reaches Earth; in the other, the Moon moves into Earth’s shadow. The Moon’s tilted orbit helps explain why these alignments do not happen every month.

5–7 min

Two eclipses, two different shadows

Space5–7 minA solar eclipse and a lunar eclipse both involve the Sun, Earth, and Moon, but the shadow falls in a different place. In one, the Moon’s shadow reaches Earth; in the other, the Moon moves into Earth’s shadow. The Moon’s tilted orbit helps explain why these alignments do not happen every month.

Space

What can century-old photographs reveal about stars today?

A star photographed on a glass plate a century ago can become a new measurement when compared with later observations. Harvard's DASCH project digitizes an astronomical plate archive, alongside dates and logbooks. Explore how calibration makes those old images useful for investigating changes across decades.

8–10 min

What can century-old photographs reveal about stars today?

Space8–10 minA star photographed on a glass plate a century ago can become a new measurement when compared with later observations. Harvard's DASCH project digitizes an astronomical plate archive, alongside dates and logbooks. Explore how calibration makes those old images useful for investigating changes across decades.

Could a star be powered by a black hole at its center? | Speech Topic | speaking.app