The Largest Yellow Star Discovered

A team of astronomers recently discovered the largest yellow star revealed to this date utilizing the European Southern Observatory's Very Large Telescope Interferometer. As we learned in class, interferometry allows one to combine numerous telescopes spaced apart into one large telescope with a smaller diffraction limit (theta is inversely proportional to d, the distance between the telescopes).

The yellow hypergiant, named HD 5171 A, is located 12,000 ly from Earth, is 13,000 times the size of our sun, and is twice the size of Betelgeuse! Additionally, it is one of the ten largest stars currently known. Because of this, it is not terribly surprising that HD 5171 A is slightly visible to the naked eye. Yellow hypergiants are also very rare, with only 12 being located in the Milky Way.

Perhaps even more surprising than finding this rare, giant star was finding its binary partner. Specifically, HD 5171 A is part of an eclipsing binary system, which was determined by measuring the varying brightness of the star with time. The data also yielded a period of 1300 days for the companion star. What is really interesting, though, is that orbiting partner is close enough to HD 5171 A that they are in contact with each other (illustrated below). This is important since it can alter the evolution process of the yellow hypergiant.

The video below is also a cool animation of the star in space!

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"Impossible" Shots of the Milky Way

Although the video and pictures are impossible in the sense that they are astounding, many people thought they were really impossible. This is because the photos were taken by an avid photographer named Justin Ng in Singapore, where there is heavy light pollution. The pollution is clearly evident in the horizon of the pictures. The bright object that rises next to the tree is Venus. Enjoy!

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What Are Tendrils?

Many of us are familiar with the "cosmic web," which describes the intricate way galaxies are organized into clusters and nodes connected by long strings. However, many of us may not be familiar with "tendrils." This is because this is a fairly new concept.

In contrast to the belief that galaxies located in the voids, or empty space between clusters, of the cosmic web are arranged randomly, Australian astronomers from the International Center for Radio Astronomy Research recently discovered that the galaxies are actually arranged in small, delicate strings leading into the vast empty space. It is this new type of structure that they termed "tendrils."

In order to discover these "tendrils," the scientists made use of the data from the Galaxy and Mass Assembly (GAMA) survey, which brings together data from numerous instruments including the Visible and Infrared Survey Telescope for Astronomy and the Anglo-Australian Telescope. Further cataloging is on the way to find more tendrils.

The result: the voids are not as empty as we thought!

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I also found this short video on tendrils, so feel free to check it out here.

No Planet X, but New Stars

As frequently occurs in the realm of science, astronomers have accidentally found thousands of new stars while searching for Planet X. Planet X, sometimes referred to as Nemesis, is a planet believed to be at the periphery of the solar system causing slight deviations in the orbits of Uranus and Neptune. Because scientists postulated Planet X may be a red or brown dwarf, which are too dim to observe with visible wavelength telescopes, the Wide-Field Infrared Survey Explorer (WISE) was used to try to find the planet. Although data collected between 2010-2011 did not reveal the presence of Nemesis, it did show thousands of new stars.

If you want to learn about the elusive (or more likely nonexistent) Planet X, check out the article here!

Comets Predict the Presence of an Exoplanet

Astronomers recently discovered a large cloud of carbon monoxide gas surrounding Beta Pictoris, a 20 million year old star system located 63 ly from Earth. Because ultraviolet radiation from the central and surrounding stars should have destroyed this layer of carbon monoxide a long time ago, scientists believe it is being replenished by the collision of comets. According to their calculations, one large comet must be destroyed every five minutes in order to maintain the CO disk around Beta Pictoris!

In order to detect the carbon monoxide disk, astronomers used the Atacama Large Millimeter/submillimeter Array in Chile to obtain spectra like those we discussed earlier in the course. The data showed that a major portion of the carbon monoxide was concentrated in one region, which gives rise to two different explanations since Beta Pictoris was observed side-on. The prominent one is that there are actually two concentrated clouds of CO, which would require the presence of a to-be-found exoplanet (Beta Pictoris already contains the planet Beta Pictoris b). This exoplanet would need to be around the size of Saturn and orbit Beta Pictoris at a larger distance than Beta Pictoris b to essentially concentrate the swarm of comets between the two planets. This is another method for finding exoplanets we can add to our list!

The video below also gives a great summary with some of the data astronomers found.

http://www.space.com/24975-colliding-comets-may-be-hiding-alien-planet-video.html

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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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When You Reach For The Stars

          Because of the strong resemblance to the shape of a hand, the picture shown above has been coined the "Hand of God." The image was obtained from X-ray imaging using NASA's Chandra X-ray Observatory to detect the low-energy x-rays (red and green) and NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) to detect the high-energy x-rays (blue). The energy ranges the Chandra Observatory and NuSTAR can observe are 0.5-2 keV and 7 to 25 keV, respectively.

          The X-ray image is the result of a supernova star explosion that left behind a pulsar, which is a magnetized neutron star that rotates. The resulting magnetic field of the pulsar, coupled with its rotating motion, then interacts with charged particles created in the supernova to form a pulsar wind nebula. This nebula is what is detected to give the "Hand of God." However, it is still unclear whether the physical material is in the shape of a hand or if it is by coincidence that the emitted radiation results in the shape. Whichever it may be, there is no taking away from this breathtaking picture.

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Pulsar

Pulsar Wind Nebula