Discovery of the Oldest Star

A team of astronomers at the Australian National University recently discovered the oldest known star in the Universe using the SkyMapper telescope at the Siding Spring Observatory (pictured above). The star is hypothesized to have formed shortly after the Big Bang and is about 6,000 ly away from the Earth. By studying this star, astronomers hope to learn about the chemistry of the first stars and early Universe.

Unlike younger stars, it seems like this old star has a different chemical composition, particularly containing a smaller amount of iron. What I found really cool was that the SkyMapper telescope was able to use this fact to find the star, since the telescope can distinguish a star's iron level from its color!

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Kepler 413-b: A Planet With Rapid Seasonal Changes

Located in the constellation of Cygnus roughly 2,300 ly away, Kepler 413-b is a giant gas planet that is approximately 35 times larger than the Earth. From the image above, you can also see that the planet orbits a binary star system consisting of a red and orange dwarf. The orbital period is ~66 days.

Like the Earth, Kepler 413-b precesses about its axis of rotation. Strangely, however, the tilt of its axis can vary up to 30 degrees in an 11 year period (recall the Earth's has been a steady 23.5 degrees)! This is what is responsible for the sudden changes in seasons on the planet.

As is evidenced from its name, Kepler 413-b was discovered by the Kepler spacecraft. It was found in an analogous manner to the way we talked about detecting eclipsing binary star systems in class. That is, astronomers studied the dimming of the binary star system as the planet passed in front of it during its orbit. Interestingly, through inconsistencies in the transit period of Kepler 413-b, astronomers were also able to discover that its orbit is tilted by 2.5 degrees with respect to the plane of the orange dwarf-red dwarf binary system (see picture above).

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A Baby Milky Way

I thought this was pretty interesting. With the help of the Keck Telescope in Hawaii, astronomers were able to obtain spatially resolved images of young galaxies, such as DLA2222-0946, shown above. Young galaxies such as this one will one day grow to become common spiral galaxies, much like our Milky Way. Although they tend to be common, they are important in that they provide insight into the evolution process by which the bulk of galaxies form.

Detecting these young galaxies, and resolving them, seems to be the difficult part. This is because they mainly contain neutral gas, which does not emit any light. So how do astronomers find them? With the help of quasars! As the light from a quasar passes through the gas of these galaxies, absorption spectra can be acquired to determine the presence and contents of the gas.

Because of this, the young galaxies are also termed DLAs, or damp Lyman-alpha absorption systems. From the Rydberg formula we discussed in lecture, this corresponds to m=1 and n=2 absorptions of hydrogen. A simple but useful application of what we have learned thus far.

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Variations in the Brightness of Polaris

Over the past few decades there have been variations in the brightness of Polaris, the North Star. Around the 1990s, scientists realized that Polaris was becoming dimmer, only to increase in brightness again in the 2000s.

The variation in Polaris' brightness can be attributed to it belonging to a class of stars known as Cepheid variables, whose luminosity varies with time. Because the brightness of these Cepheids is directly related to the pulsation period, they serve an important function as standard candles that allow astronomers to measure distances in space.

Scott Engle, an astronomer at Villanova University, is part of a team that has been observing these fluctuations over the past years. Interestingly, in order to gauge how much brighter the North Star has become, they used data acquired by Tycho Brahe and dating as far back as the 10th century! Although not entirely accurate, they estimate that the start has become 2.5-4.6 times brighter!

Another interesting note is that even though Engle's team received approval to observe Polaris with the Hubble Space Telescope (HST), the HST team were reluctant because they feared that it might damage the sensitive Cosmic Origins Spectograph detector used in the telescope. Thankfully, nothing seems to have gone wrong.

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