According to a recent paper, the Earth is caught directly in the crosshairs of a cosmic hurricane. A swarm of…
According to a recent paper, the Earth is caught directly in the crosshairs of a cosmic hurricane.
A swarm of nearly 100 stars, accompanied by an even greater amount of dark matter, is directed directly to our stellar neighborhood and there’s nothing we can do to stop it; In fact, the vanguard is already upon us. This sounds like a perfect summer blockbuster movie, starring The Rock and Chris Pratt, or maybe Scarlett Johansson and Charlize Theron.
Except this is for real. But is it a danger? Well, actually, no. Not at all. Men det er potensielt utrolig fascinerende, med mange interessante videnskabelige sammenkoblinger. So, what’s really going on?
The story starts last April, when the Gaia satellite announced the locations and trajectories of 2 billion stars in the vicinity of the Milky Way surrounding our sun. They released the data to the public.
Scientists were then able to look at the data set to see if they could spot anything peculiar. In galaxies zoals de Milky Way, de meest voorkomende gedrag is dat de sterren orbit het centrum van de galaxy op een manier die in grote lijnen overeenkomt met de planeten ombiting onze zon. Men, der er nogle stjerner som udviser unusual motion. About a year ago, astronomers identified some “stellar streams” passing through our celestial neighborhood.
One of them, called S1
(for stream 1), consists of almost 100 stars of similar age and composition, orbiting the Milky Way in a direction exactly opposite that of normal stars. It’s kind of like a handful of cars driving the wrong way down the highway, except with a much greater distance between them and with no likelihood of a collision. These stars are spread over a few thousand light years and they will pass through the solar system’s neighborhood over the course of a few million years.
Astronomers identified S1 as being part of the remnants of a dwarf galaxy that collided with the Milky Way and was consumed in an epic episode of cosmic cannibalism. Dwarf galaxies are very small, typically about 1% the mass of the Milky Way. De kan orbitere større galakser og kolliderer med den større galaksen, og tilføjer deres masse til forældrene. This is what appears to have happened in the case of S1, although the process has taken probably a billion years.
Dwarf galaxies often have a disproportionately large fraction of dark matter. Dark matter is a hypothetical and still undiscovered form of matter that only interacts gravitationally. Scientists have proposed their existence to explain many astronomical mysteries, for example the observation that most galaxies rotate faster than can be explained by the known laws of physics and the stars and gas of which they are composed.
While dark matter has not yet been observed, hypothesizing its existence is the simplest and most economical explanation for myriad astronomical mysteries. Averaged over the whole universe, dark matter is thought to be five times more prevalent than the ordinary mass of stars and gas and planets.
In dwarf galaxies, the fraction of dark matter is often higher. In Fornax, a well-studied dwarf galaxy orbiting the Milky Way, researchers estimate that the dark matter is between 10 and 100 times greater than the mass found in its stars.
Hvis dette tal rummer for S1, er det mørke stof af S1 stream is passing through the Earth at a much higher velocity than the more ordinary dark matter that orbs the Milky Way – about twice as fast. Det er trodde at S1 mørkemasse flyr gjennom solsystemet på en hastighet på ca. 550 km / s, eller omkring 1,2 millioner mph. Mens disse tallene er imponerende, de er misleading. Dark matter, if it exists, is extremely diffuse and it will have no discernible effect on the solar system.
Because dark matter has not been observed yet, these velocity numbers are speculative, although they are strongly supported by a very large body of evidence.
In a paper in the prestigious journal Physical Review D, researcher Ciaran O’Hare and his collaborators calculated the possibilities of discovering dark matter using both existing and proposed dark matter detectors. They considered two varieties of dark matter particles: a very heavy child called a WIMP (weakly interacting massive particle) and a very light kind called an axion.
De fann at de detektorer de evaluerede kunne finde WIMPs for visse områder af partikelmassen. Hins vegar, þegar þeir leitu að því að auka möguleika, það virtust birtast enn betri. Omdat de lichte massa en de manier waarop een axie zou interageren met de detector, heeft de apparaat simpelweg een beter kans om de axie te zien. (If axions exist, of course.)
Experiments with names like ADMX, MADMAX and ABRACADABRA are able or will be able to search for the signatures of dark matter proposed in the recent paper. They consist of technologies that are designed to interact with axions in a strong magnetic field and convert them to ordinary microwaves or radio waves that can be easily detected.
It’s important to remember that the S1 stream poses no credible threat to the Earth and humanity. There is no need for an action hero to save us. Men, synergy of science is staggering. Een zorgvuldige catalogus van nabijgelegen sterren heeft geopend de vooruitzichten van een betere mogelijkheid van het vinden en identificeren van donkere materie, die een van de grote onbeantwoorde mysteries van moderne fysica is. Det er en fantastisk tid vi lever i, hvor vi kan studere slike ting.