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Thursday, March 28, 2024

Science Corner – Billions of planets with life – or just one?

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Around a star called Lich, in the constellation of Virgo the Virgin, orbit three planets called Poltergeist, Phobetor, and Draugr. Really, I am not making this up! Except that Lich is no longer a star, because it exploded, briefly becoming brighter than a thousand suns, blasting any planets’ atmospheres into space, and frying any life they may have had.

What was left of the star collapsed down to a ball about 20 km in diameter, more massive than the sun – so a pinhead would be a million tons – spinning at 10,000 rpm, detected on Earth as radio pulses – a pulsar.

In 1992 close inspection of Lich’s pulse rate showed tiny periodic variations that could only be explained by the gravitational pull of planets. These were the first extrasolar planets (exoplanets) discovered.

Many more were found in other ways. When the colors of starlight are spread out like a rainbow, in a spectrograph, lines like a barcode can be seen, which shift towards blue if the star approaches and towards red if it recedes. In 1995 astronomers saw lines from a star not very different from the sun shifting periodically as it was pulled by a big planet, a ‘hot Jupiter,’ orbiting every 4.23 days. The technique improved so much that astronomers can now detect stars wobbling at walking-speed, and hundreds of exoplanets have been found this way, including some similar to Earth in size.

But even more have been found in transit, that is by passing in front of the star and dimming its light. Venus and Mercury sometimes do that to our sun, visible as little black discs. By September 8, 2017, astronomers had found 3,667 exoplanets, mostly using the Kepler telescope in space, monitoring 145,000 stars for periodic dimming.

Most exciting so far is Trappist-1, with seven planets found in 2015, at least three of which are in the Goldilocks zone, not too hot or cold but just right for liquid water, and perhaps life. Sometimes we can even detect a planet’s atmosphere as the starlight shines through it. On August 31 astronomers using the Hubble Space Telescope announced the detection of hydrogen, suggesting large quantities of water on those planets.

There may be more than a billion Goldilocks planets in our Milky Way galaxy. We know one has life. Is it just one, or millions, or billions?

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Michael Albrow
Michael Albrow
Michael Albrow is a scientist emeritus at Fermilab, Batavia and a member of Naperville Sunrise Rotary. Born in England, Mike lived in Switzerland and Sweden before settling in the U.S. 25 years ago.

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