Question: Did scientists recently find dark matter near our sun?
Plenty of dark matter near the Sun
ScienceDaily (Aug. 9, 2012) — Astronomers at the University of Zürich and the ETH Zürich, together with other international researchers, have found large amounts of invisible "dark matter" near the Sun. Their results are inconsistent with the theory that the Milky Way Galaxy is surrounded by a massive "halo" of dark matter, but this is the first study of its kind to use a method rigorously tested against mock data from high quality simulations. The authors also find tantalizing hints of a new dark matter component in our Galaxy.
Dark matter was first proposed by the Swiss astronomer Fritz Zwicky in the 1930s. He found that clusters of galaxies were filled with a mysterious dark matter that kept them from flying apart. At nearly the same time, Jan Oort in the Netherlands discovered that the density of matter near the Sun was nearly twice what could be explained by the presence of stars and gas alone. In the intervening decades, astronomers developed a theory of dark matter and structure formation that explains the properties of clusters and galaxies in the Universe, but the amount of dark matter in the solar neighbourhood has remained more mysterious. For decades after Oort's measurement, studies found 3-6 times more dark matter than expected. Then last year new data and a new method claimed far less than expected. The community was left puzzled, generally believing that the observations and analyses simply weren't sensitive enough to perform a reliable measurement.
Testing the method on a simulated Milky Way
Now an international team, lead by researchers of the University of Zürich with the participation of the ETH Zürich, have developed a new technique. The researchers used a state-of-the-art simulation of the Milky Way to test their mass-measuring method before applying it to real data. This threw up a number of surprises: they noticed that standard techniques used over the past twenty years were biased, always tending to underestimate the amount of dark matter. The researchers then developed a new unbiased technique that recovered the correct answer from the simulated data. Applying their technique to the positions and velocities of thousands of orange K dwarf stars near the Sun, they obtained a new measure of the local dark matter density.
Evidence for dark matter near the sun
"We are 99% confident that there is dark matter near the Sun," says the lead author Silvia Garbari. In fact, if anything, the authors' favored dark matter density is a little high: they find more dark matter than expected at 90% confidence. There is a 10% chance that this is merely a statistical fluke, but if future data confirms this high value the implications are exciting as Silvia explains: "This could be the first evidence for a "disc" of dark matter in our Galaxy, as recently predicted by theory and numerical simulations of galaxy formation, or it could mean that the dark matter halo of our galaxy is squashed, boosting the local dark matter density."
Many physicists are placing their bets on dark matter being a new fundamental particle that interacts only very weakly with normal matter, but strongly enough to be detected in experiments deep underground. An accurate measure of the local dark matter density is vital for such experiments as co-author Prof. George Lake explains: "If dark matter is a fundamental particle, billions of these particles will have passed through your body by the time your finish reading this article. Experimental physicists hope to capture just a few of these particles each year in experiments like XENON and CDMS currently in operation. Knowing the local properties of dark matter is the key to revealing just what kind of particle it consists of."
The effects of what is thought to be dark matter was observed through gravitational lensing, the same time that the Higgs' boson pattern was found. It hasn't been confirmed, though.
It wasn't near the Sun, however, it was quite far away between two distant galaxy clusters, around 2.4 billion light years away.
There is dark matter in our Solar System. It isn't really as mysterious as some seem to think. There are lots of dark matter "candidates" and they really have been "found". The problem is that the known candidates do not account for a significant portion of the dark matter that is believed to exist. Nevertheless, these dark matter candidates (neutrinos, WIMPs, brown dwarfs, and more) are definitely around, here in our Solar neighborhood.
The real mystery is dark energy.
No, on two grounds:
1 Dark matter has never exactly been 'found'. The best we can do is to infer its presence, and that we do mainly by means of conflicting mass calculations. By looking at a galaxy we can estimate with reasonable accuracy the total mass of the stars, gas, planets, black holes and such that it contains. That gives us one mass estimate. We can also make an unrelated estimate by measuring the rotation of its outer parts around the centre, and hence the gravitational pull of the galaxy. In practice, there is a consistent difference between these calculations, such that the first estimate is always well below the second. 'Dark matter' is just shorthand for 'there seems to be something out there, but we really haven't a clue what it might be'. If it exists, and there is still a possibility that we have got one or other calculation wrong, then the main thing about it is that it doesn't interact with electromagnetic radiation. Hence 'dark'.
2 It would be rather improbable to observe dark matter so close to home. Whatever it is doesn't seem to be very 'lumpy' on a galactic scale, but rather fairly evenly spread. That makes it harder to observe over short range.