Michael Murphy (opens in new tab), Professor of Astrophysics, Swinburne University of Technology
There’s an ungainly, irksome downside with our understanding of nature’s legal guidelines which physicists have been making an attempt to elucidate for many years. It’s about electromagnetism, the legislation of how atoms and light-weight work together, which explains all the things from why you do not fall by way of the ground to why the sky is blue.
Our idea of electromagnetism is arguably the most effective bodily idea people have ever made — but it surely has no reply for why electromagnetism is as robust as it’s. Only experiments can inform you electromagnetism’s power, which is measured by a quantity referred to as α (aka alpha, or the fine-structure constant (opens in new tab)).
The American physicist Richard Feynman, who helped give you the idea, called this (opens in new tab) “one of the greatest damn mysteries of physics” and urged physicists to “put this number up on their wall and worry about it.”
Related: How many stars are in the universe?
In research just published in Science (opens in new tab), we determined to check whether or not α is similar in other places inside our galaxy by learning stars which might be nearly an identical twins of our sun. If α is completely different in other places, it’d assist us discover the final word idea, not simply of electromagnetism, however of all nature’s legal guidelines collectively — the “theory of everything.”
We need to break our favourite idea
Physicists really need one factor: a scenario the place our present understanding of physics breaks down. New physics. A sign that can not be defined by present theories. An indication-post for the idea of all the things.
To discover it, they could wait deep underground in a gold mine (opens in new tab) for particles of dark matter to collide with a particular crystal. Or they could carefully tend the world’s best atomic clocks (opens in new tab) for years to see in the event that they inform barely completely different time. Or smash protons collectively at (almost) the velocity of sunshine within the 17-mile (27 kilometers) ring of the Large Hadron Collider.
The bother is, it is onerous to know the place to look. Our present theories cannot information us.
Of course, we glance in laboratories on Earth, the place it is best to go looking totally and most exactly. But that is a bit just like the drunk only searching for his lost keys under a lamp-post (opens in new tab) when, truly, he may need misplaced them on the opposite aspect of the street, someplace in a darkish nook.
Stars are horrible, however typically terribly comparable
We determined to look past Earth, past our solar system, to see if stars that are almost an identical twins of our sun produce the identical rainbow of colours. Atoms within the atmospheres of stars soak up among the mild struggling outwards from the nuclear furnaces of their cores.
Only sure colours are absorbed, leaving darkish traces within the rainbow. Those absorbed colours are decided by α — so measuring the darkish traces very rigorously additionally lets us measure α.
The downside is, the atmospheres of stars are transferring — boiling, spinning, looping, burping — and this shifts the traces. The shifts spoil any comparability with the identical traces in laboratories on Earth, and therefore any likelihood of measuring α. Stars, it appears, are horrible locations to check electromagnetism.
But we puzzled: in the event you discover stars which might be very comparable — twins of one another — possibly their darkish, absorbed colours are comparable as properly. So as an alternative of evaluating stars to laboratories on Earth, we in contrast twins of our sun to one another.
A brand new check with solar twins
Our crew of pupil, postdoctoral and senior researchers, at Swinburne University of Technology and the University of New South Wales, measured the spacing between pairs of absorption traces in our sun and 16 “solar twins” — stars nearly indistinguishable from our sun.
The rainbows from these stars have been noticed on the 3.6-metre European Southern Observatory (ESO) telescope (opens in new tab) in Chile. While not the biggest telescope on the earth, the sunshine it collects is fed into in all probability the best-controlled, best-understood spectrograph: HARPS (opens in new tab). This separates the sunshine into its colours, revealing the detailed sample of darkish traces.
HARPS spends a lot of its time observing sun-like stars to seek for planets. Handily, this supplied a treasure trove of precisely the info we wanted.
From these beautiful spectra, we have now proven that α was the identical within the 17 solar twins to an astonishing precision: simply 50 elements per billion. That’s like evaluating your peak to the circumference of Earth. It’s probably the most exact astronomical check of α ever carried out.
Unfortunately, our new measurements did not break our favourite idea. But the celebs we have studied are all comparatively close by, solely as much as 160 light-years away.
We’ve just lately recognized new solar twins a lot additional away, about half approach to the middle of our Milky Way galaxy.
In this area, there ought to be a a lot greater focus of dark matter — an elusive substance astronomers imagine lurks all through the galaxy and past. Like α, we all know treasured little about dark matter, and some theoretical physicists (opens in new tab) recommend the internal elements of our galaxy could be simply the darkish nook we must always seek for connections between these two “damn mysteries of physics.”
If we are able to observe these rather more distant suns with the biggest optical telescopes, possibly we’ll discover the keys to the universe.
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