Sunday, June 5, 2016

Remote Robotic Telescope Update: June 2016

Hello, all! A quick post on the state of Insight Observatory's robotic telescope project. For those of you "in the dark" (ha!) here is a short recap: ever since the beginning of Insight Observatory we have had plans to set up and run a robotic telescope for use on IO sponsored projects. We have the majority of items needed to fulfill this endeavor and are continuously looking for means to complete the acquisition of the remaining equipment so the project can finally be realized.

As of June 2016 we possess the following items:
  • Dream Telescope 16" f/3.75 Astrograph: The telescope itself which provides a fast optical system and coverage of large CCD imaging sensors
  • Software Bisque Paramount ME: This type of mount has been widely used for robotic telescopes for years, so we know we have a battle-proven solution
  • Astrodon MMOAG: Off-axis guider for guiding the Paramount
  • HP Server: Need a computer to run all this stuff!
What is needed to complete the project? Here's a breakdown:
Image of Finger Lakes Instruments (FLI) ProlinePL 16803 Imaging Camera
Image of Starlight Express Ultrastar Guiding Camera
  • Finger Lakes 10 Position Filter Wheel: This will hold the imaging filters
Image of Finger Lakes 10 Position Filter Wheel
  • Filters: We will need LRGB filters at first, and then later will acquire other types (Hydrogen Alpha, photometric, etc) when funds become available
Of course. let's not forget that we need a place to host this telescope! Last year we had some discussions with SkyPi and found them to be excellent people to work with, so we hope to be able to use them when it comes time to get our scope setup and hosted.

That's all for now folks, keep your eye on this site for further updates!
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Wednesday, June 1, 2016

Variable Stars and the Stories They Tell: Exoplanets and the Search for Extraterrestrial Life

Though the figures are tough to keep up with, as they are changing almost daily, the Kepler space telescope has discovered over 2,300 exoplanets in all. Those are just a few in existence whose orbital planes lie at a favorable incline from our perspective. Of those 2,300+, at least 207 are Earth-sized and at least 48 lie in the so-called 'Goldilocks' or habitable zone. The way Kepler achieves this miracle of detection of extra-solar planets is by measuring the varying light curves of their parent or host stars. As a planet transits or passes in front of a star, as seen from our neighborhood, there is a barely measurable but significant decrease in the star's light, on average about 2%, with another .03% decrease in the presence of a planetary atmosphere. This is roughly equivalent to the amount of light lost by an observer of a housefly passing in front of a car headlight as seen from several miles away. When astronomers can determine a regular pattern of dimming and brightening, they can deduce that the star has at least one planet in orbit around it. Stars vary in their brightness for other reasons, as was seen earlier, but this may the most exciting one.

Image of An artist imagining Kepler-62f, a potentially habitable exoplanet discovered using data from the Kepler Spacecraft
An artist imagining Kepler-62f, a potentially
habitable exoplanet discovered using
 data from the Kepler Spacecraft
If life is discovered elsewhere in the universe, is it likely it will be found on Earth-like extra-solar planets - planets that fall into that comfy, cozy distance from their host stars that we refer to as the Habitable Zone? We humans like to think so, and it may very well be, but life may also be found in much less likely environments. The diversity of life on Earth, itself, is staggering in that it can be found in the deepest ocean trenches, in waters above 600 degrees Fahrenheit and pushing well north and south of the Arctic and Antarctic Circles, respectively, and, on land, in temperatures well below freezing. It should be remembered that we are products of our environment in the struggle for life. Nature has tried out many kinds of organisms through the process of natural selection and most of those organisms were ill-suited to the task of survival. In fact, more species of living things have become extinct than have survived.

The first step in finding extraterrestrial life is to find extra-solar planets, or, exoplanets. The first technique used to detect extra-solar planets was through the measurement of the shift in the radial velocity of a host star. A planet or planets orbiting a star will produce shifts in the spectral lines of the star as they tug on it, making the star appear to wiggle back and forth, as it moved through space. In 1952, Otto Struve suggested that extra-solar planets might be detected by dips in a host star's light during a planet's transit. Even then, techniques were available to detect such a drop in light but it was forgotten about for decades. In 1999, two professional astronomers using a 10-centimeter telescope discovered the first telltale signs of such a transiting extra-solar planet. Amateur and professional astronomers have since detected countless candidates.

NASA's Ames Research Center lists a table of 70-plus confirmed exoplanets discovered by Kepler as of May 2012 and designated by the name 'Kepler' followed by a letter. Planetary characteristics in the table for each planet include the following headings: Jupiter Masses, Earth Masses, Jupiter Radii, Earth Radii, Density, Temperature, Transition Duration, Period, Semi-Major Axis (UA), Eccentricity, Inclination (in degrees) and Distance (in parsecs). The table also lists characteristics of the host star. It should be noted here that Kepler-23b – Kepler-30b are planets that are within just a few Earth radii, though they are several hundred times more massive and their orbital periods seem much too short (just a few days) to be within the habitable zone. Nevertheless, it tells us that exoplanets, roughly the size of Earth, are detectable and are indeed out there.

Image of Earthlike Exoplanets Discovered by the Kepler Spacecraft Chart Courtesy of NASA
Earth like Exoplanets Discovered by the Kepler
Spacecraft Chart Courtesy of NASA
The Kepler mission was originally slated to last 3 1/2 years but steps have been taken by its team of engineers to extend its mission another 3 years. Within the first 45 days of operation, Kepler, combined with follow-up ground-based observations, confirmed the discovery of five new exoplanets, including Kepler-7b, the least dense planet discovered at that time. Kepler has also been credited with the discovery of two "super-hot" orbiting companions - companions that appear to be hotter than their respective host stars. That discovery first announced at the 215th American Astronomical Society meeting in Washington, D. C. on January 4, 2010, revealed that the data from Kepler, along with the ground-based data had yet to confirm just what these objects are. One of the objects, KOI-74b measured 70,000 degrees Fahrenheit! Its host star, in comparison, is a mere 17,000 degrees Fahrenheit. The object is roughly the size of Jupiter and orbits its host star every 23 days. The hottest confirmed exoplanet to date has a temperature of 3,700 degrees Fahrenheit. As of June 15, 2010, Kepler had identified 706 stars hosting exoplanet candidates with sizes from as small as that of Earth to larger than Jupiter. On August 26, 2010, two new exoplanets orbiting the same star were discovered via the transit method. Two planets orbiting the star Kepler-9, roughly 2,300 light-years distant have been designated Kepler-9b and 9c and were discovered over a seven-month period. Astronomers at the W. M. Keck Observatory in Hawaii have estimated the masses of these two confirmed planets. Kepler-9b is the larger of the two, the other being only 1.5 Earth radii, making it one of the smallest exoplanets known.

Image of Open Cluster NGC 6819 in Cygnus - Image by Al Kelly
Open Cluster NGC 6819 in Cygnus - Image by Al Kelly
Other discoveries by Kepler include solar-like oscillations in the light curves of red giant stars using time-series photometry and solar-like asteroseismic events in relatively nearby type-G stars and in the open cluster NGC 6819. Although the Kepler mission was originally designed to find transiting Earth-like exoplanets by continuously observing over 100,000 stars in a field centered in the constellation Cygnus, two years into the mission, it is also providing an extraordinary collection of time-series data for studying the variability of stars in our galaxy. There are on-line tools available for studying this variability, including the NASA Star and Exoplanet Database's periodogram tool. A periodogram finds the periodicities present in time-series data sets and the probability that an individual period arises by chance. Life "as we know it", would require that it evolve on a planet with the exact same physical makeup as Earth. Life here on Earth is carbon-based, but we should not necessarily exclude, say, even silicon-based life on other worlds. Our body chemistry is that of the Earth. Nevertheless, life will come in many forms. It may be possible to detect life on Earth-like exoplanets possessing an atmosphere by measuring gaseous emissions in its atmosphere by spectroscopy, such as the oxygen given off by vegetation here on Earth. Other forms of life give off carbon dioxide and even methane into the atmosphere. Luckily, the universe operates the same everywhere else as it does locally, so we can know what signs to look for. The presence of such gasses can be determined by measuring a planet's transmission spectrum during its transit across the face of a star. If a planetary atmosphere is not present, the light fall-off will be the same at all wavelengths. If certain elements are present in the planet's atmosphere, they will absorb some of the star's light. In one case, sodium present in the atmosphere of a planet made the planet appear to be six percent larger than at other wavelengths. Another way that astrobiologists and exobiologists expect to be able to detect the presence of life is by spectropolarimetry, or, looking for bio-signatures in the reflected polarized light of a host star by one of its planets.

Ultimately, we should not limit our search to Earth-like planets exclusively, but it's a good place to start. Life, as we know it - or not - may be a far more interesting story than we think, and one thing is becoming clearer; the "Habitable Zone" around a given star may be less distinct than many of us imagine!
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Sunday, May 29, 2016

Type Ia Supernovae, Recurrent Novae and Classical Novae

A Possible Symbiotic Relationship Between Type Ia Supernovae, Recurrent Novae, and Classical Novae: Do These Events Occur in the Same or Different Stellar Masses?

Astronomers are trying to determine the answer to the question of whether there is a direct relationship between Type Ia Supernovae (SNeIa), Classical Novae (CNe) and Recurrent Novae (RNe). Some evidence has been found to support a distinct relationship between catastrophic SNe events and RNe outbursts. There is evidence that a tipping of the scale into a full-fledged Type Ia SN may be related to RNe, and though some evidence seems to point to this, all the particulars are not out regarding the three types. Do the three events occur within the same stellar mass, or are they separate events occurring in separate stellar masses. 

Image of Las Cumbres Observatory Global Telescope Network
Las Cumbres Observatory Global Telescope Network
The results of a study, led by Ben Dilday, a postdoctoral researcher in physics at UC Santa Barbara and at Las Cumbres Observatory Global Telescope Network (LCOGT), are surprising because previous indirect –– but strong –– evidence had pointed to the merger of two white dwarf stars as the originators of other Type Ia supernovae. One interesting subject is the planetary nebula NGC 5189. It has a unique, torqued-spiral shape, with peculiar patterns of knots around it's periphery, possibly due to a wobbling in the stars' rotation, or, possibly, to the presence of a binary white dwarf system at its center.

Symbiotic binaries are systems containing both a white dwarf (WD) and a red giant component. Symbiotic novae are those systems in which thermonuclear eruptions occur on the WD component. These are to be distinguished from events driven by accretion disk instabilities analogous to dwarf novae eruptions in cataclysmic variable outbursts. Another class of symbiotic system is that in which the WD is extremely luminous and it seems likely that quiescent nuclear burning is ongoing on the accreting WD. A fundamental question is the secular evolution of the WD. Do the repeated outbursts or quiescent burning in these accreting systems cause the WD to gain or lose mass? If it is gaining mass, can it eventually reach the Chandrasekhar Limit and become a supernova (a Type Ia SN if it can hide the hydrogen and helium in the system)? In order to better understand these systems, a new study has begun of the evolution of Thermonuclear Runaways (TNRs) in the accreted envelopes of WDs using a variety of initial WD masses, luminosities, and mass accretion rates. Astrophysicists have put into use a 1-D hydro code, NOVA, which includes the new convective algorithm of Arnett, Meakin, and Young, the Hix and Thielemann nuclear reaction solver, the Iliadis reaction rate library, the Timmes equation of state, and the OPAL opacities. It is reported that (1) the WD grows in mass for all simulations so that canonical 'steady burning' does not occur, and, (2) that only a small fraction of the accreted matter is ejected in some (but not all) simulations. They have also found that the accreting systems, before thermonuclear runaway, are too cool to be seen in X-ray searches for Type Ia SN progenitors.

Image of SN PTF 11kx Imaged by BJ Fulton Las Cumbres Global Telescope Network
SN PTF 11kx Imaged by BJ Fulton
Las Cumbres Global Telescope Network
The case of SN PTF 11kx, discovered by the Palomar Transient Factory, showed this relationship beyond further doubt. Astronomers could discern that the supernova was surrounded by shells of hydrogen gas that had likely been blown off in previous nova eruptions, decades before the supernova occurred. Novae are more frequent but weak explosions not catastrophic to the star. While similar shells of material had been seen before in a handful of Type Ia supernovae, their origin was debated and they had never before been firmly linked to novae - some doubted that the material was near to the supernova at all. SN PTF 11kx proved differently. The surrounding gas was moving too slowly to be from the supernova event itself, but too fast to be from a typical stellar wind. Lars Bildsten, director of UC Santa Barbara's Kavli Institute for Theoretical Physics, hypothesized that it was material shot out from a previous nova eruption, which had been slowed as it collided with the wind from the red giant star. UCSB graduate student Kevin Moore showed this hypothesis to be plausible, and would lead to gas moving at speeds seen in the observations. Adding credence to the theory was the fact that the material moved at two different speeds -- faster-moving interior material to slower-moving exterior -- exactly as expected. The outer material had been slowing for decades, while the inner material had less time to slow. But if this was the case, the fast-moving supernova ejecta should have eventually collided with the nova material. About two months after the explosion, this is exactly what happened. New observations showed that the supernova ejecta was colliding with the interior shell of material. It was impossible to doubt that this gas was nearby the supernova. "This was the most exciting supernova I've ever studied," said Dilday, "For several months, almost every new observation showed something we'd never seen before."

This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration; The Palomar Transient Factory at the California Institute of Technology; Baltic Astronomy, Vol 21, pages 76 - 87, 201arXiv:1211.6145v1 [astro-ph.SR]
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