Our sun's undiscovered stellar nemesis is still out there, says physicist

science & techPhys.org

Our sun's undiscovered stellar nemesis is still out there, says physicist

from Phys.org

Long-period, high-inclination comets of the sort that can cause extinction-level impacts here on Earth have long been thought to originate from a theoretical Oort cloud. That is, a roughly spherical cloud of icy cometary objects that number in the trillions at distances that extend up to 1.6 light-years away.

explained

Nemesis is a hypothetical red dwarf or brown dwarf, originally postulated in 1984 to be orbiting the Sun at a distance of about 95,000 AU (1.5 light-years), somewhat beyond the Oort cloud, to explain a perceived cycle of mass extinctions in the geological record, which seem to occur more often at intervals of 26 million years. In a 2017 paper, Sarah Sadavoy and Steven Stahler argued that the Sun was probably part of a binary system at the time of its formation, leading them to suggest "there probably was a Nemesis, a long time ago". Such a star would have separated from this binary system over four billion years ago, meaning it could not be responsible for the more recent cycles of mass extinctions.

From Wikipedia: Nemesis (hypothetical star) (CC BY-SA 4.0) ↗

how it works

A distant companion would orbit far beyond the planets and, on each pass, gravitationally jostle the Oort cloud. That would knock some comets onto paths falling toward the inner solar system in bursts.

so what

It shows how scientists try to explain where dangerous comets come from, and how an elegant idea can persist even when searches come up empty. If Nemesis existed it would be a dim red or brown dwarf, which is why astronomers keep looking.

the bigger pattern

Searching for a hidden object by its gravitational effects has worked before, as with Neptune in 1846, and failed before, as with the hunted planet Vulcan near Mercury. Nemesis so far belongs with the second group.

fun fact

The name Nemesis comes from the Greek goddess of retribution.

D. W. Griffith’s A Corner in Wheat (1909)

the gist

In 1909 D. W. Griffith made a 14-minute film about a speculator who corners the wheat market and doubles the price of bread. A farmer sows his field while a 'Wheat King' gambles in the Chicago wheat pit; bakers raise the loaf from five cents to ten and the poor line up for bread. Griffith cut back and forth between the farm, the feast and the breadline, a technique called parallel editing, so audiences saw both ends of the economy at once. The film drew on Frank Norris's stories and on a real scheme: months earlier Chicago financier James Patten had cornered wheat, sent bread prices up and made about $5 million, roughly $185 million today.

how it works

To corner a market, a trader buys up most of the available supply and the futures contracts that promise more. Anyone who has to deliver the commodity must then buy from the cornerer at whatever price is demanded. The trader profits until the stock is released or the scheme collapses.

so what

A century on, it still shows how markets can be rigged by someone who controls supply, and how the people at either end, farmers and eaters, pay for it. It also helped establish editing as a way to argue a point, not just tell a story.

the bigger pattern

Corners have recurred whenever supply could be locked up, from the Hunt brothers' attempt on silver in 1979 to 1980 to the 'Black Friday' gold panic of 1869. Many such schemes end by collapsing, and the response is often new rules on speculation.

fun fact

In the film the Wheat King dies by falling into a grain elevator and being buried in the wheat he hoarded, an ending borrowed from Norris's novel The Octopus.

Usman Khawaja refuses to answer Sandpapergate question about Pat Cummins | 7.30

from ABC News In-depth

One of the darkest days in Australia's sporting history has been dragged back into the spotlight.

A new autobiography by former Test cricketer Usman Khawaja has made explosive revelations about the Australian Test team's 2018 ball-tampering saga in South Africa.

7.30 host Sarah Ferguson speaks to Usman Khawaja.

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