Astronomers identify a young heavyweight star in the Milky Way

Artist's impression of the disc and outflow around the massive young star. Credit: A. Smith, Institute of Astronomy, Cambridge.

Astronomers have identified a young star, located almost 11,000 light years away, which could help us understand how the most massive stars in the Universe are formed. This young star, already more than 30 times the mass of our Sun, is still in the process of gathering material from its parent molecular cloud, and may be even more massive when it finally reaches adulthood.

The researchers, led by a team at the University of Cambridge, have identified a key stage in the birth of a very massive star, and found that these stars form in a similar way to much smaller stars like our Sun - from a rotating disc of gas and dust. The results will be presented this week at the Star Formation 2016 conference held at the University of Exeter, and are reported in the Monthly Notices of the Royal Astronomical Society.
In our galaxy, massive young stars - those with a mass at least eight times greater than the Sun - are much more difficult to study than smaller stars. This is because they live fast and die young, making them rare among the 100 billion stars in the Milky Way, and on average, they are much further away.
"An average star like our Sun is formed over a few million years, whereas massive stars are formed orders of magnitude faster—around 100,000 years," said Dr John Ilee from Cambridge's Institute of Astronomy, the study's lead author. "These massive stars also burn through their fuel much more quickly, so they have shorter overall lifespans, making them harder to catch when they are infants."
The protostar that Ilee and his colleagues identified resides in an infrared dark cloud - a very cold and dense region of space which makes for an ideal stellar nursery. However, this rich star-forming region is difficult to observe using conventional telescopes, since the young stars are surrounded by a thick, opaque cloud of gas and dust. But by using the Submillimeter Array (SMA) in Hawaii and the Karl G Jansky Very Large Array (VLA) in New Mexico, both of which use relatively long wavelengths of light to observe the sky, the researchers were able to 'see' through the cloud and into the stellar nursery itself.
By measuring the amount of radiation emitted by cold dust near the star, and by using unique fingerprints of various different molecules in the gas, the researchers were able to determine the presence of a 'Keplerian' disc - one which rotates more quickly at its centre than at its edge.
"This type of rotation is also seen in the Solar System - the inner planets rotate around the Sun more quickly than the outer planets," said Ilee. "It's exciting to find such a disc around a massive young star, because it suggests that massive stars form in a similar way to lower mass stars, like our Sun."
The initial phases of this work were part of an undergraduate summer research project at the University of St Andrews, funded by the Royal Astronomical Society (RAS). The undergraduate carrying out the work, Pooneh Nazari, said, "My project involved an initial exploration of the observations, and writing a piece of software to 'weigh' the central star. I'm very grateful to the RAS for providing me with funding for the summer project—I'd encourage anyone interested in academic research to try one!"
From these observations, the team measured the mass of the protostar to be over 30 times the mass of the Sun. In addition, the disc surrounding the young star was also calculated to be relatively massive, between two and three times the mass of our Sun. Dr Duncan Forgan, also from St Andrews and lead author of a companion paper, said, "Our theoretical calculations suggest that the disc could in fact be hiding even more mass under layers of gas and dust. The disc may even be so massive that it can break up under its own gravity, forming a series of less massive companion protostars."
The next step for the researchers will be to observe the region with the Atacama Large Millimetre Array (ALMA), located in Chile. This powerful instrument will allow any potential companions to be seen, and allow researchers to learn more about this intriguing young heavyweight in our galaxy.

Jellyfish proteins used to create polariton laser

A schematic illustration of a fluorescent protein polariton laser in action. Particles made from a mixture of light and electronic energy are created in a film of green fluorescent protein produced by live cells. The particles can …more

A combined team of researchers from Scotland and Germany has developed a way to create a polariton laser by using jellyfish proteins cultivated in E. coli cells. In their paper published in the journal Science Advances, the team describes their technique and possible uses for the result.

As most people know, at a basic level, conventional lasers work by bouncing light around inside of a cavity and then emitting identical photons as a beam. There is another type of laser that is less well known, the polariton laser—it works by tossing photons back and forth between excited molecules. But the reason it has not made its way into commercial use is because it must be cooled to an extremely low temperature to work properly. In this new approach, the researchers report the development of such a laser that works at room temperatures.

To make the new laser, the researchers grew enhanced green fluorescent protein from jellyfish in E. coli cells because prior research suggested they were capable of producing polaritons (quasiparticles that are able to carry excitations with them). The protein was fashioned into a very thin (500 nanometer) film that was set between two mirrors. To create a laser beam, all the researchers had to do was shine a blue light into the device, which excited the proteins to the point of producing polaritons—soon thereafter, they spontaneously synchronized, producing a laser beam that was emitted out of the device.

The researchers note that others have tried to create such lasers with limited success due to the excited particles colliding with one another—severe cooling was the only way to tame them. But the jellyfish proteins came with a built-in solution—each was barrel-shaped with the fluorescent molecules shielded inside, protecting the emitted particles from interfering with one another.

The team suggests that because the laser operates at room temperature, one of its ideal applications might be as a laser tag for cancer—one that is able to note the differences in wavelengths of light bounced from cells allowing for easily identifying those that are cancerous. They plan to search for other biological materials that might serve a similar purpose but that do so by emitting colors other than green.

One of the most inflated giant planets discovered

KELT-12b discovery light curve from the KELT-North telescope. The light curve contains 7,498 observations spanning 6.3 years. The light curve is phase-folded to the BLS-determined orbital period of 5.031450 days. The red points show the same data binned at 1.2-hour intervals after phasefolding. Credit: Stevens et al., 2016.

An international team of astronomers has detected a highly inflated giant planet orbiting a mildly evolved star. According to a research paper published Aug. 16 on the arXiv pre-print server, the newly found exoplanet, designated KELT-12b, is one of the most inflated "hot Jupiters" known to date.

A giant exoworld that expands in size when its parent star is at the end of its life is called "inflated." This inflation process is very often seen in the so-called "hot Jupiters"—gas giant planets similar in characteristics to the solar system's biggest planet, with orbital periods of less than 10 days. They have high surface temperatures as they orbit their parent stars very closely. The newly discovered KELT-12b is another great example of an inflated "hot Jupiter."
KELT-12b was spotted by a team of researchers led by Daniel Stevens of the Ohio State University. For their observations, the astronomers employed the KELT-North telescope at the Winer Observatory in Arizona. KELT-North is one of the two robotic telescopes in the Kilodegree Extremely Little Telescope (KELT) survey, whose main goal is to search for transiting exoplanets around bright stars.
While analyzing KELT-North data acquired from 2007 to 2013, the scientists identified the initial transit signal of KELT-12b. Afterwards, the team conducted follow-up observations to confirm the planetary nature of this signal. They obtained several high-cadence, high-precision light curves from their global follow-up network of observers and small telescopes.
"We identified the initial transit signal in the KELT-North survey data and established the planetary nature of the companion through precise follow-up photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging," the researchers wrote in the paper.
The newly found alien world is orbiting a mildly evolved, 2 billion-year-old star KELT-12 (also known as TYC 2619-1057-1) that is about 2.4 times larger than our sun and has a mass of approximately 1.59 solar masses. The planet itself, with an orbital period of five days, is slightly less massive than Jupiter, having about 0.95 the mass of the solar system's gas giant. However, its radius is much larger than astronomers have expected – around 1.79 Jupiter radii. This relatively large radius, combined with an extremely low density at a level of just 0.21 g/cm3 indicates that KELT-12b is an inflated exoplanet. Moreover, the scientists emphasize that it is one of the most inflated "hot Jupiters" discovered so far.
As the newest addition to the list of inflated gas giants, KELT-12b data could be helpful in future studies of the inflation process, as it is still unclear what really causes it. In general, the possible explanations could be assigned to two different theories—scientists believe that the inflation is caused by deposition of energy from the host star, or due to inhibited cooling of the planet.
The authors of the paper hope that future studies will greatly expand our catalog of "hot Jupiters" around hot stars, adding new ones with orbital periods longer than a few days. It is expected to put researchers in a better position to investigate any differences in giant planet inflation, which could be crucial to our understanding of this process.