An invisible force at the center of our galaxy
Scientists have theorized that our Milky Way galaxy has a super massive black hole at the center of it, but how did this idea come about? How do astronomers measure something that has actually never been seen in our telescopes?
Above is an animation of star movements in our galaxy over the past 16 years. They all orbit around a point that emits no light in our galaxy. We can measure the mass of these stars and calculate that their orbits require an object with the mass of 4 million Suns. So far this points to a super massive black hole in our galaxy.
A new study of the Perseus galaxy cluster, shown in this image, using NASA’s Chandra X-ray Observatory and 73 other clusters with ESA’s XMM-Newton has revealed a mysterious X-ray signal in the data. This signal is represented in the circled data points in the inset, which is a plot of X-ray intensity as a function of X-ray energy. The signal is also seen in over 70 other galaxy clusters using XMM-Newton. This unidentified X-ray emission line - that is, a spike of intensity at a very specific energy, in this case centered on about 3.56 kiloelectron volts (keV).
One intriguing possible explanation of this X-ray emission line is that it is produced by the decay of sterile neutrinos, a type of particle that has been proposed as a candidate for dark matter. While holding exciting potential, these results must be confirmed with additional data to rule out other explanations and determine whether it is plausible that dark matter has been observed.
- A paper describing the detection of this mysterious emission line was published in the June 20th issue of The Astrophysical Journal and a preprint is available online.
Credit: NASA/CXC/SAO/E.Bulbul, et al.
Scientists believe dark energy makes up about 68% of the universe and dark matter about 27%. That leaves just 5% for us and everything we can actually see.
But what’s the dark stuff made of?
From the TED-Ed Lesson Dark matter: The matter we can’t see - James Gillies
Animation by TED-Ed
Quantum Flavordynamics (Weak Nuclear Force)
- This is basically the decay of a neutron into a proton by the emission of a W- boson.
- The up and down part of quarks is known as their flavour, they can effectively change flavours, in this case it is a down quark into an up quark.
- The W- has to be emitted for the flavour of the quark to change but it does not last long until it decays into an electron (e-) and an anti-electron neutrino (ν
- The W- boson (80GeV) is roughly 80x heavier than the neutron (1GeV) it decayed from meaning that it takes a lot of energy for this to happen so is seen happening inside stars which is basically just a big burning ball of protons.
- The energy for this change can also be borrowed from the vacuum provided the energy is paid back, to do this we refer to Heisenberg’s uncertainty principle:
ΔE x Δt<h
(amount of energy borrowed from vacuum) x (amount of time borrowed for) < Plancks constant
- This shows that the energy debt has to be paid back in 1e-25 seconds in which time the W- boson can move the distance of part a proton before it decays.
- This process is represented by the special unitary matrix two dimensional su(2) in mathematics. It is 2D because it is only changing ups and downs.
A newfound huge asteroid, nicknamed “The Beast,” is expected to zoom by Earth this weekend. The asteroid 2014 HQ124, which is the size of a football stadium, poses no chance of hitting Earth in its flyby on Sunday (June 8), and will pass by at a range of three times the distance between the Earth-moon on Sunday (June 8). It was discovered on April 23 by NASA’s Wide-Field Infrared Survey Explorer, a sky-mapping space telescope.
Credit: NASA / JPL
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