One of the consequences of general relativity is that light can be deflected by nearby masses. Mass curves space, and this curvature causes light to bend slightly. It was first observed during a total eclipse in 1919. The effect is extremely small unless the light passes close to a large mass, so gravitational lensing (as it is typically known) is usually only noticed with objects such as lensed galaxies, or specific tests of general relativity. But even though the effect is small as you get further from a mass, it isn’t zero. As our astronomical measurements become more precise, the effects of gravity are starting to become something we can’t ignore.
Energy Bubble
Yesterday I talked about the Fermi gamma ray telescope, and how it allowed us to make much more precise observations of gamma rays in the universe. Part of the purpose of the Fermi telescope is to observe gamma ray bursts, but its broader purpose is to make a sky survey of gamma ray sources in the universe. Already it has found something quite interesting.
Star of Bethlehem
When stars are portrayed in media, they are often shown with long spikes emanating from them. Perhaps the most common example is that of the “star of Bethlehem” which, according to the story, led the wise men to baby Jesus. Of course when we look at stars in the night sky, we don’t see any such spikes. Stars twinkle due to atmospheric disturbances, but that’s about it. In photographs, however, bright stars often have such long spikes. So what causes them? It all has to do with an interesting bit of optics.
Two By Two
Yesterday I talked about the detection of gamma ray bursts, intense blasts of gamma rays that occasionally appear in distant galaxies. Gamma ray bursts were only detected when gamma ray satellites were put into orbit in the 1960s. This is because gamma rays are absorbed by our atmosphere. Even then, the detectors were relatively primitive and couldn’t determine the direction of the bursts. Instead, multiple satellites were used to triangulate the location of these bursts. Since then, gamma ray astronomy has gotten much more sophisticated.
Counting in the Dark
The Alpha Magnetic Spectrometer (AMS) is a particle detector located on the International Space Station. It’s designed to detect high energy particles known as cosmic rays, and a while back it made news regarding claims it had detected dark matter. It hadn’t, but instead had detected an excess of positrons that might be due to dark matter. It could also be due to other things, which is why claiming it had found evidence of dark matter was a bit disingenuous. Now the AMS is back with more data. Despite some claims, the new results don’t hint at dark matter any more than last time, but it is still solid work.
The Big One
In the 1960s a series of satellites were built as part of Project Vela. Project Vela was intended to detect violations of the 1963 ban on above ground testing of nuclear weapons. The Vela satellites were designed to detect bursts of gamma rays, which are high energy electromagnetic waves (light) produced by radioactive decay. If any nuclear weapon was detonated in space, the resulting radioactive decay would release a large amount of gamma rays which would be detected by the Vela satellites.
Pale Blue Dot
The image above is a radio image of Voyager 1. It was taken from the Very Long Baseline Array, which is a collection of 10 radio telescopes scattered from Hawaii to the Virgin Islands. It captures the faint radio signal of the distant probe. That pale blue dot is the most distant object made by humans.
Aurora Glow
This week there’s been plenty of solar activity, including a couple of x-class solar flares. Since these flares were aimed in Earth’s general direction there has been some murmuring about “the big one” but these aren’t remotely large in historical terms. They are, however, strong enough that millions could have a rare chance of viewing an aurora.
To Your Scattered Photons Go
Yesterday I wrote about the cosmic x-ray background, and I noted that x-ray astronomy, particularly with high-energy x-rays is difficult. But what is it about x-rays that makes x-ray astronomy so challenging?