Friday, May 15, 2015

The Case of the Strangled Galaxies

Summary: Galaxies are considered dead when they no longer are producing new stars. It is still unclear what causes this process but what astronomers do now know is the most common time scale of them dying -- approximately four billion years. Astronomers are calling this process strangulation.

Astronomers are able to tell how quickly the galaxy died based on the metal content remaining in the galaxy. The more stars that are being formed in a galaxy, the more metal content is seen. The way it works is simple. If a galaxy dies quickly and quite violently (for instance if the cool gas that fuels the star formation is suddenly ripped away), then the stars immediately stop producing and the metal content remains the same. But if the galaxy if cut off from the supply of cool gas but still continues to produce stars, using up the last of the supply, the metal content in the galaxy grows and grows until it "suffocates".

The difference was seen when comparing the spectra of light emitted by red, passive galaxies and blue, star-forming galaxies. With the data from Sloan they were able to see that the dead galaxies were, on average, four billion years older than the active galaxies. This is consistent with the amount of time the astronomers had calculated it would take to burn of the remaining amount of gas supply whilst strangling to death.

While the astronomers are now confident that death by strangulation is the most common way a galaxy meets it's ultimate end, it is still not clear what causes this. The most likely suspect at this point in time seems to be overcrowding which would lead to a greater probability of disruption to the gas supply, but this would need further investigation.



BBC News
Nature

Friday, May 8, 2015

LHC is Up and Running

Summary: After the scheduled two year shutdown and update of the Large Hadron Collider at CERN, the LHC is back and ready for even higher energy collisions. It began smashing particles again Easter Sunday at energies of 450 GeV. Amazingly enough, this is a lower energy and will be used for calibrations before the truly record breaking energies of 7,000 GeV starting on June 1st.


BBC News

Friday, March 27, 2015

A Shattering of Old Dark Matter Theories

Summary: Thanks to new data, further theories of the nature of dark matter have been smashed to pieces! Pardon me for being excited about leading theories being wrong but that only means that I may have a part to play in developing the correct theory. So what has changed?

It turns out dark matter really doesn't seem to interact with anything apart from gravity. It doesn't even interact with itself. The study was conducted my using the Hubble and Chandra to look at collisions of different galaxies and watch the dark matter. Well, it looked at the gravitational lensing since dark matter itself is essentially impossible to see.

In the way science should work, Dr. Massey explains that "if you want to figure out what something is made out of, you knock it, or you throw it across the room and see where the bits go." The surprising part was that unlike the stars that slide past each other and the gas clouds that come to a halt in these collisions, the dark matter "seems not to interact with anything at all." Rather like a ghost, it just glides through the other dark matter like it's no big deal. Since it doesn't even interact with itself, many prominent theories for what dark matter is has now fallen apart. Which means exciting new possibilities for the rest of us in the future. 


BBC News
Science Mag

Sunday, March 22, 2015

Rosetta's Comet is Slowing Down

Summary: Despite the rover not being turned on again, astronomers are still learning new things about the chosen comet. For instance, it's changing rotation speed. The comet takes approximately 12.4 hours to complete one rotation, only that rate seems to be slowing down by one second per day. It seems like a small change but that is big in astronomical terms. It is actually a faster rate of change than in September. Back then it was slowing down by 33 milliseconds per day. (And right there is a differential equation for those who are so inclined.)

Scientists know the reason for this. The comet 67P is becoming more active which means there are gas jets shooting out of the rock and serving as propulsion, much like a rocket, only in the opposite direction of rotation, thus slowing it down. The jets actually shoot out of the comet at 800 meters per second and extend a few kilometers off the surface.

Astronomers found this out thanks to Rosetta still being in orbit around the rock. In order to keep the satellite in the correct trajectory, the navigators were using a system of landmarks on the surface to keep track of position. Only the landmarks were coming into view at a different time than expected.

BBC News

Saturday, March 14, 2015

More Secret Oceans

Summary: Jupiter's moon Ganymede is the latest solar system body now thought to have a secret ocean lying beneath its icy crust. The evidence for this lies in the aurora produced by the moon's magnetosphere. The auroras are also influences by Jupiter, but not as much as scientists thought they should be. The presence of a salty ocean below the surface would counteract some if the effects of Jupiter and leave what we see now.

This new evidence means that we are past the point of ambiguity but not certain yet. We will know more when a probe in 2030 orbits the moon and finishes with a crash landing into the surface. 


BBC News

And Happy Pi Day!

Wednesday, January 28, 2015

Changing the Speed of Light

Summary: Scientists in Scotland have successfully altered the speed of light. Incredible in my humble opinion. To do this, they used a mask to alter the shape of a photon. This slowed the light down. Then the photon was released back into free space and raced against a photon of unaltered shape. Amazingly, the altered particle remained at the lower speed.

At this initial stage it is nothing more than a curiosity but it could have implications for astronomy. While it would not make a difference in small distances such as between Earth and the moon, if photons mutate shape in nature then our distances to far off stars and galaxies may not be as accurate as previously assumed.

BBC News

Astronomical Updates

Highest Quality image of Ceres:
Ceres, the 950-km wide dwarf planet has a new image that is clearer than ever before. The resolution beats that of Hubble's image of Ceres. The cool thing is the image quality can only improve as Dawn approaches.

BBC News


New Horizons setting it's sights on Pluto:
The New Horizons probe will be zooming by Pluto on July 14th of this year but before it reaches the planet, it must start taking images to calibrate it's instruments and check its trajectory. The first images, with Pluto only as a tiny speck, should be released this week. Researchers are hoping that this mission will reveal many surprises about Pluto including new moons and possible rings.

BBC News


Large Asteroid and it's Moon:
The asteroid 2004 BL 86 was seen with a moon as it passed relatively close to Earth. The asteroid itself is 325m wide and it's moon is 70m wide.

BBC News