Tammy Plotner, Author at Universe Today

June 23, 2011December 24, 2015 by Tammy Plotner

Betelgeuse: A Claim To Flame

This picture of the dramatic nebula around the bright red supergiant star Betelgeuse was created from images taken with the VISIR infrared camera on ESO’s Very Large Telescope (VLT). This structure, resembling flames emanating from the star, forms because the behemoth is shedding its material into space. The earlier NACO observations of the plumes are reproduced in the central disc. The small red circle in the middle has a diameter about four and half times that of the Earth’s orbit and represents the location of Betelgeuse’s visible surface. The black disc corresponds to a very bright part of the image that was masked to allow the fainter nebula to be seen. Credit: ESO/P. Kervella

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If it were at home in the center of our solar system, this red supergiant’s girth would extend out almost to the orbit of Jupiter. It’s about a thousand times larger than Sol and shines a hundred thousand times brighter. What’s more, the amount of mass it sheds every ten thousand years could create another sun. It’s nearing the end of its life and when it goes supernova, we’ll be able to see it here on Earth – even in broad daylight. So what’s surrounding Betelgeuse that looks like the conflagration generation? Read on…

Using the VISIR instrument on ESO’s Very Large Telescope (VLT), researchers have been able to take a more detailed look than ever at the nebula surrounding Betelgeuse. These infrared diffraction-limited images hold clues to the stellar aging process, since much of this structure cannot be seen in visible light. Filled with knots and pockets, this mysterious ether makes for prime study.

“Mass-loss occurring in red supergiants (RSGs) is a major contributor to the enrichment of the interstellar medium in dust and molecules. The physical mechanism of this mass loss is however relatively poorly known. Betelgeuse is the nearest RSG, and as such a prime object for high angular resolution observations of its surface (by interferometry) and close circumstellar environment.” says P. Kervella, et al. “The goal of our program is to understand how the material expelled from Betelgeuse is transported from its surface to the interstellar medium, and how it evolves chemically in this process.”

With branches extending up to six times the diameter of the star, Betelguese isn’t showing any uniformity in its surface shedding process. Picture, if you will, heating a pot of spaghetti sauce on a hot stove. When the temperature fires up below, it creates a rising bubble. When this surfaces, it pops – blowing spaghetti sauce all over the top of your stove and walls – and releasing steam. While this is a loose analogy, it’s fairly representative of what’s going on with this red supergiant. Large-scale gas motions inside the star are popping out O-rich dust, such as silicates or alumina and expelling gases in jets.

“The circumstellar envelope around Betelgeuse extends at least up to several tens of stellar radii. Its relatively high degree of clumpiness indicates an inhomogeneous spatial distribution of the material lost by the star.” says P. Kervella, et al. “Its extension corresponds to an important intermediate scale, where most of the dust is probably formed, between the hot and compact gaseous envelope observed previously in the near infrared and the interstellar medium.”

For now, there’s still many questions to be answered, such as how the dust is created and how it can be found as such great distances from the star itself. We’re just now beginning to understand RSG convection properties and their mechanisms for mass loss. For now, the team will continue their studies using these new techniques. “The knots and filamentary extensions of the nebula observed at larger distances from Betelgeuse appear to correspond to inhomogeneities in the mass lost by the star in the recent past, probably within the last few centuries. Further observations are expected to clarify the nature and composition of the nebular features identified in our images, using spatially resolved spectroscopy of the CSE.”

And the marshmallow for this campfire might just be a companion star…

Original Story Source: ESO Press Release.

June 22, 2011December 24, 2015 by Tammy Plotner

Cygnus X-1: Blue Supergiant Pairs With Black Hole

This X-ray image of Cygnus X-1 was taken by a balloon-borne telescope, the High Energy Replicated Optics (HERO) project. NASA image.

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Discovered in 1964 during a rocket flight, Cygnus X-1 holds the record for being the strongest X-ray source seen from Earth. The blue supergiant star designated as HDE 226868 is just part of this high-mass X-ray binary system… the other is a black hole.

“We present a detailed study of the X-ray dust scattering halo of the black hole candidate based on two Chandra HETGS observations. Using 18 different dust models, including one modified by us (dubbed XLNW), we probe the interstellar medium between us and this source.” says Jingen Xiang, et al. “A consistent description of the cloud properties along the line of sight that describes at the same time the halo radial profile, the halo lightcurves, and the column density from source spectroscopy is best achieved with a small subset of these models… The remainder of the dust along the line of sight is close to the black hole binary.”

Located about 6,000 light years from Earth as measured by the Hipparcos satellite (but this value has a relatively high degree of uncertainty), Cygnus X-1 has been the topic for a huge amount of astronomical studies for nearly 50 years. We’re aware the blue supergiant variable star orbits its unseen companion at roughly 1/5 the distance of the Sun to the Earth (0.2 AU), and we surmised that stellar wind accounted for the accretion disk around the X-ray source. We are also aware of a pair of jets spewing material into interstellar space. Deep inside, superheated materials are sending out copious amounts of X-rays, but what else lay beyond? Can we separate star from event horizon with accuracy?

“We report a direct and accurate measurement of the distance to the X-ray binary Cygnus X-1, which contains the first black hole to be discovered. The distance of 1.86(-0.11,+0.12) kpc was obtained from a trigonometric parallax measurement using the Very Long Baseline Array. The position measurements are also sensitive to the 5.6 d binary orbit and we determine the orbit to be clockwise on the sky.” says Mark J. Reid, et al. “We also measured the proper motion of Cygnus X-1 which, when coupled to the distance and Doppler shift, gives the three-dimensional space motion of the system. When corrected for differential Galactic rotation, the non-circular (peculiar) motion of the binary is only about 21 km/s, indicating that the binary did not experience a large “kick” at formation.”

If you don’t think this is exciting news, then think again. “The compact primary in the X-ray binary Cygnus X-1 was the first black hole to be established via dynamical observations.” says Lijun Gou. “We have recently determined accurate values for its mass and distance, and for the orbital inclination angle of the binary. Building on these results, which are based on our favored (asynchronous) dynamical model, we have measured the radius of the inner edge of the black hole’s accretion disk by fitting its thermal continuum spectrum to a fully relativistic model of a thin accretion disk.”

Determining the spin rate has been high on the list of observations – and difficult because it changed states periodically. Only when it is in a soft spectral state can accurate measurements be taken. Oddly enough, for all the countless observations taken of Cygnus X-1 over the years, it has never been caught in a thermally dominant state. To that end, the black hole spin is measured by estimating the inner radius of the accretion disk.

“Our results take into account all significant sources of observational and model-parameter uncertainties, which are dominated by the uncertainties in black hole mass, orbital inclination angle and distance.” says the team. “The uncertainties introduced by the thin-disk model we employ are particularly small in this case, given the disk’s low luminosity.”

Heisenberg would be so proud….

Original Story Souce: Cornell University Library with facts from Wikipedia.

June 22, 2011December 24, 2015 by Tammy Plotner

White Dwarf Stars Predict Our Solar System’s Demise

A Hubble Space Telescope color image of a small portion of the cluster only 0.63 light-years across reveals eight white dwarf stars (inside blue circles) among the cluster's much brighter population of yellow sun-like stars and cooler red dwarf stars. (Credit: Harvey Richer (University of British Columbia, Vancouver, Canada) and NASA)

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With no more volume than could be contained within a teaspoon, the material that makes up a white dwarf star weighs tons. Smaller than the diameter of Earth, and a direct family member of stars like our own Sol, these stellar gnomes could predict our eventual fate.

Using data from the Hubble Space Telescope, Nathan Dickinson, a postgraduate student in the University’s Department of Physics and Astronomy, is hard at work analyzing chemical compositions of white dwarf stars for his PhD. Unlike many students interested in “heavy metal”, Dickinson is more interested in “heavy elements”. The older, more cool models could contain elements such as oxygen, nitrogen, silicon… while the hot youngsters show heavy elements like calcium and magnesium. These weighty basics occur at extreme heat and sometimes, even to excess. The cremation generation?

“Understanding whether the extra material in hot white dwarfs comes from torn up planets is important,” emphasizes Dickinson. “It can give us an idea of how these ancient planetary systems evolve as the star ages, so we get a fuller picture of how solar systems die. However, they sometimes exhibit more of this material than is expected, which raises the question of whether this extra material also came from planets or whether it originated elsewhere, perhaps in clouds around the star.”

Past research has shown that anywhere from 1 to 3% of white dwarf stars can be contaminated by an influx of materials from closely orbiting dust clouds. What makes up these clouds? It could be rocky debris like asteroids. Held within the Roche Limit, these planetoids are mulched by gravitational tides – just like Saturn’s ring system.

“Working at the forefront of this scientific area is extremely exciting,” says Dickinson. “I find being one of a relatively small community of people in the world to work on this particular area amazing. This work is helping to shape our understanding of how most stars end their lives, how solar systems die, how the environment around these ancient stars behaves and what will ultimately happen to the vast majority of stars in the galaxy.”

And really close to home…

Original Story Source: Science Daily.

June 21, 2011December 24, 2015 by Tammy Plotner

Sleeping Beauties: A Galactic Fairye Tale

Bluer galaxies are actively “awake” and forming stars, while redder galaxies have shut down and are “asleep.” (Image: NASA, ESA, S. Beckwith (STScI) and the HUDF team)

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It’s a well known fact that galaxies come in two types – either actively forming stars or not. In simplistic terms, that means they are either awake or asleep. But now scientists are looking back twelve billion light years across time to find the same holds just as true then as it does now. As a matter of fact, galaxies may have been behaving this way for around 85% of the history of the Universe.

“The fact that we see such young galaxies in the distant universe that have already shut off is remarkable,” said Kate Whitaker, a Yale University graduate student and lead author of the paper, which is published in the June 20 online edition of the Astrophysical Journal.

So, without poking the sleeping dragon, just how did the astronomers make their determinations? Try with the use of a 4-meter Kitt Peak telescope in Arizona and a special set of filters developed by Whitaker and her team. Just like all astronomy filters, this new breed is selective to certain bandpasses, or wavelengths, of light. These new filter sets were then used on 40,000 galaxies over a 75 night period and the data collected and examined. The end product was the deepest and most comprehensive of its kind so far. Active, awake galaxies appear more blue, while the sleepy-heads appear red. Believe it or not, when it comes to the cosmic bedroom there’s more activity than previously thought.

“We don’t see many galaxies in the in-between state,” said Pieter van Dokkum, a Yale astronomer and another author of the paper. “This discovery shows how quickly galaxies go from one state to the other, from actively forming stars to shutting off.”

Whether the dozing galaxies have completely shut down remains an open question, Whitaker said. However, the new study suggests the active galaxies are forming stars at rates about 50 times greater than their somnambulistic counterparts. “Next, we hope to determine whether galaxies go back and forth between waking and sleeping or whether they fall asleep and never wake up again,” van Dokkum said. “We’re also interested in how long it takes galaxies to fall asleep, and whether we can catch one in the act of dozing off.”

Pass the Red Bull… and sing the blues! “Are you sleeping? Can you hear me? Do you know if I am by your side? Does it matter? If you hear me? When the mornin’ comes I’ll be there by your side… There was a time, we had a time. There was a time we had time…”

Original Story Source: Yale Daily Bulletin.

June 21, 2011April 26, 2016 by Tammy Plotner

Model Lighting Ordinance Means Preservation Of Future Dark Skies

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For every astronomer everywhere – and even naturalists – the need to preserve dark skies has been an issue tackled by the International Dark Skies Association for over two decades. It’s more than just asking your neighbor to turn off their porch light while you’re observing. It’s about light pollution as a whole – from government to community lighting. In the past the IDA has relied on education, but now things could be getting a whole lot better.

“IDA and the Illuminating Engineering Society (IES) proudly announce public release of the Model Lighting Ordinance (MLO) as a valuable guide for environmentally responsible outdoor lighting in North America.” says the organization. “Developed jointly by the IDA and the IES over a period of seven years, the IDA/IES partnership will encourage broad adoption of comprehensive outdoor lighting ordinances without devoting extensive staff time and resources to their development.”

In a time of budget cuts and pressure on volunteer time, such programs like the MLO are absolutely invaluable. This guide will enable communities to make responsible decisions about outdoor lighting standards… effectively reducing glare, light trespass, and skyglow. Studies have shown these three culprits of light pollution wreak havoc on more than just astronomy – it affects our own human biorhythms, wildlife and more. By having a standard that’s easy and cost effective to follow, things can be changed.

“The MLO offers several innovations to outdoor lighting regulation, including the use of five lighting zones to classify land use with appropriate lighting levels for each. Zones range from LZ0, designed for pristine natural environments and limited outdoor lighting, to LZ4, for limited application in areas of extensive development in the largest cities. The second innovation limits the amount of light used for each property.” says the group. “Third, the MLO uses the IES’s new TM-15 -11 “BUG” (Backlight, Uplight and Glare) classification of outdoor lighting fixtures to ensure that only well-shielded fixtures are used. No uplight for area and street lighting is allowed in any zone. The MLO will be revised on a regular basis to include new information, feedback from municipalities using it and changes to IES standards.”

Will these new guidelines be adopted by government and industry? You might be surprised at just how well concepts of this type can be accepted when you can show how they are not only cost effective, but energy saving as well. Not everyone around the world reacts in a negative way when asked to cut lighting – especially when they realize a group is tackling major concerns such as security and safety.

Bob Parks, executive director of IDA, hopes for widespread application. “The MLO will give communities the tool they need to control outdoor lighting and the assurance that the outcome will meet the international standards developed by the IES,” states Parks. “The MLO will accelerate adoption of quality outdoor lighting practices in municipalities of all sizes and show planners how to improve the quality of outdoor lighting while saving energy and reducing operating cost.”

Robert Horner, director of public policy for the IES, expresses similar expectations, stating, “The IES is proud to have produced, in partnership with the IDA, the first Model Lighting Ordnance. This will give states and municipalities the ability to enact effective outdoor lighting legislation and codes, while maintaining the necessary lighting quality for a safe and secure lighted environment and meeting all relevant IES standards and practices.”

In the meantime, get involved with your community and the IDA. Our dark skies future starts with you…

Original Story Source: International Dark Sky Association and Model Lighting Ordinance.

June 21, 2011December 24, 2015 by Tammy Plotner

New Comet Approaching!

Animation showing the comet moving against the background of stars. Images taken at the Pan-STARRS 1 Telescope on the night of June 5-6, 2011. Hawaii time is 10 hours earlier than Universal Time (UT). Credit: Henry Hsieh, PS1SC

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Pan-STARRS… Doesn’t that conjure up an image of a faceless stranger whispering in the dark, passing their hand over a clear sky and leaving a glittering trail? Pan-STARRS… Take the second star on the left and go straight on ’til morning. Pan-STARRS… Regardless of my flights of fancy, Pan-STARRS is a telescopic reality and its home is Mount Haleakala, Hawaii. The Panoramic Survey Telescope and Rapid Response System is renowned for its wide-field imaging capabilities – and its mission to alert planet Earth of potentially dangerous objects approaching. Now the most recent discovery is a comet which may be visible to the naked eye in early 2013.

Discovered on the night of June 5-6 using the Pan-STARRS 1 telescope, the moving rogue was confirmed to be a comet on the following night by astronomer Richard Wainscoat and graduate student Marco Micheli using the Canada-France-Hawaii Telescope on Mauna Kea. The Oort Cloud visitor quickly had its orbit calculated by the Harvard Minor Planet Center and shows it will be visiting in our solar system within about 30 million miles (50 million km) of the Sun in early 2013. While that’s about the same distance as the Sol / Mercury factor, the comet will not encounter Earth… just give us a good show.

Wainscoat said, “The comet has an orbit that is close to parabolic, meaning that this may be the first time it will ever come close to the sun, and that it may never return.” Just like our stranger in the dark, eh?

Will this new comet named C/2011 L4 (PANSTARRS) create a spectacle? It’s not easy to judge. While it is expected to be brightest in February or March 2013, it depends on how much ice it contains as to how bright it will become. Another factor is positioning. Since it will be low to the west at sunset, sky brightness may also make it difficult to observe. Right now C/2011 L4 is about 700 million miles (1.2 billion km) from the Sun, placing it beyond the orbit of Jupiter and only able to be spotted using a large telescope and imaging equipment. It will take several months of observation for more accurate assessments, but astronomers are cautious since many predictions can end up being a cometary dud. There’s no doubt it will be here – but there’s always uncertainties as to how bright it will be.

In the mean time, we’ll take Pan-STARRS whispering word for it… and believe.

Original Story Source: Institute for Astronomy / University of Hawaii.

June 21, 2011December 24, 2015 by Tammy Plotner

The ATLAS3D Project: Calling A Different Tune

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In 1926, astronomer Edwin Hubble gave us our first basic galaxy classification scenario – the Hubble Sequence. Using photographic plates, Hubble derived a simplistic system based on three visually known structures: elipitical, spiral and lenticular. This sequence, when plotted out, gave the appearance of a common object and eventually became known as the “Hubble Tuning Fork” (as seen above). For many decades, this served as a standard. Now the ATLAS3D Project is calling a different tune…

Just who is the pied piper in this merry band? The ATLAS3D project is a multiwavelength survey combined with a theoretical modelling effort. The observations it takes spans from the radio to the millimetre and optical. It provides multicolor imaging, as well as two-dimensional kinematics of the atomic, molecular and ionized gases, together with the kinematics and population of the stars, Where does it dance? Only around a carefully selected, volume-limited sample of 260 early-type galaxies.

Heading up the project is a team of 25 astronomers from Europe and Northern America, including ASTRON astronomers Morganti, Oosterloo, and Serra – and all with a mission – to update and revise our understanding of galactic evolution. Employing the SAURON spectrograph on the 4.2-meter William Herschel Telescope on La Palma, the team was able to distinguish stellar movement in the pre-determined galactic candidates. These new assessments show that spheroid galaxies belong to the spiral galaxy classification. How did they come to that conclusion? The largest portion of spheroids – or early types – are basically the same family as spirals and evolve along a similar line. But with ATLAS3D findings, we’re looking at new concepts.

We’re seeing beyond the optical (photographic plates) which founded Hubble’s original diagram – where once galaxies were separated by their distinct characteristics such as rapid rotators rich in stars and gas – or as slowly moving, gas-poor models. Up until now, it was also next to impossible to distinguish sparse “face-on” structure from edge-on spheroids. With the aid of kinematic data astronomers can “see” rotation – allowing observation of all galaxy types from any angle.

“Slow and fast rotators tend to be classified as ellipticals and lenticulars, respectively, but the contamination is strong enough to affect results solely based on such a scheme: 20 per cent of all fast rotators are classified as ellipticals, and more importantly 66 per cent of all ellipticals in the ATLAS3D sample are fast rotators.” says the team. “Our complete sample of 260 ETGs leads to a new criterion to disentangle fast and slow rotators which now includes a dependency on the apparent ellipticity. It separates the two classes significantly better than the previous prescription.”

While it will take many years and many more observations to sort out all the new data, it would seem that our current understanding of galactic evolution just might need a “tune up”.

Oringinal Story Source: ASTRON.

June 19, 2011April 26, 2016 by Tammy Plotner

Skylight Telescopes… Tomorrow’s Treasures

Skylight Refractors - Credit: Richard Day

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What you’re looking at isn’t a vintage telescope, but a modern day long focus refractor. Custom-built to exacting standards, this new twist on an old breed doesn’t make you one of the crowd… it makes you stand out in one.

Drive your car down the highway and how long does it take to spot a model that’s the same as yours? Get that new look in clothes and sure enough you’ll catch someone wearing the same shirt. When it comes to telescopes, walk through any star party and you’re sure to find a piece of equipment identical to what you own. Why not turn having a telescope into an ultra personal experience by choosing a one that’s totally unique? A Skylight Telescopes Custom Refractor can do that for you.

Hand-crafted and inspired directly by telescopes designed in the 19th Century, Skylight Custom Refractors show attention to detail and craftsmanship that are simply unsurpassed. They are the brainchild of Richard Day. “Being surrounded by interesting refractors made me a little jaded towards modern telescopes and the fairly obvious similarities found from brand to brand. I was particularly captivated by the beautiful refractors made by T. Cooke and Sons… not very well known in the USA, but revered in the UK and Europe.” says Day. “While stepping back and appreciating a particularly nice 3″/f15 example, I had a ‘why doesn’t anyone make anything like this anymore?’ moment, and so I decided that I would.”

From conception to finished product took Richard two years, but the end result quickly captivated the UK publication, Astronomy Now. “This telescope delivers a serious optical punch. Star testing under calm conditions at 187x showed nearly identical diffraction rings inside and outside focus. In focus, stars displayed a hard Airy disc with a pair of textbook perfect diffraction rings round them. I’m happy to report a cautious 1/8 wave for this optic. I could not detect coma, field curvature, astigmatism or distortion.” says Neil English. “The last quarter moon was mind-boggling. I had to charge the telescope with stupendously high powers (about 100x per inch) before any image breakdown manifested itself. At these excessive powers, image quality was still very good, with only mere traces of yellow and blue tinges visible around crater rims at areas of high contrast.”

With all of this comes a price – and Skylight Refractors don’t come cheap. But, there is a reason. Each one of these unique telescopes is custom built and quality optics are expensive. Only through mass production can a telescope company lower their prices and Richard isn’t a company… he’s an artisan. “Victorian design is now virtually lost in favour of mass produced, CNC machined white tubes, which I simply do not find terribly interesting.” says Day. “The Victorian design element is an exercise in elegance for me…many people have told me that my scopes are the most beautiful that they’ve ever seen, and this pleases me greatly.”

Originally a Vancouver native, Richard takes his telescope making seriously. Every telescope he designs is individually star tested from his London home, then signed and numbered before they are released. With the exception of the focuser and optics, it’s all handcrafted and when each limited number of a model is gone? It’s gone forever. Because of their exclusive nature, Skylight Refractors were never meant to be offered “wholesale” – but now a few of them are available around the world. Where can they be found? In Europe, it’s Skylight Telescopes. In Canada, it’s Vancouver Telescope Centre or Khan Scope Centre. In the United States, it’s from my home-zone, OPT.

When Skylight Refractors appeared at the 2011 NEAF gathering in Rockland, New York, it was all one could do to not want to take one home… permanently. Quite simply put, they are that beautiful and well-constructed. Lunar and planetary observing, double stars… You’re no longer just observing by rote, but practicing a time-honored craft. Just imagine yourself owning a telescope that matches the caliber of those used by the Cambridge Observatory, Coats Observatory, Carter Observatory or Yorkshire Philosophical Society. So enduring was this design that many are still in use today. Be assured that owning a classic telescope is like owning your own personal piece of history – one that will be around long after fancy has faded. I cannot thank Richard enough for allowing me to take a personal look at – and interest in – what he has to offer.

Why sail along the stars when you can sail with them?

Addendum: This review was intended to re-kindle the romantic and personal experience which observers feel for their equipment. Make no mistake – this is a high quality refractor which employs state-of-the-art components such as high quality Japanese glass objectives in a handmade collimateable countercell and a premium Baader Steeltrack focuser. Its design allows for high magnfication – above and beyond the call of duty, and the color correction is outstanding. This is not a “model” telescope, but a telescope modeled after a time-honored design. Its performance level – like all telescopes – relies on the eyepiece introduced. Use lesser quality and you’ll get diminuished performance. Use a premium occular and you’ll get the view you paid for! And its cost, by the way, is not only comparable to similar custom made refractors (such as Stellarvue), but even less in some instances.

June 18, 2011December 24, 2015 by Tammy Plotner

Exomoons Could Be Excellent Incubators

Artist's impression of the view from a hypothetical moon around a exoplanet orbiting a triple star system. Credit: NASA

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With the arrival of the Cassini–Huygens mission in 2004 to Saturn’s satellite Titan, we terrestrials became acutely aware that similar moons could be orbiting similarly large planets in other solar systems besides our own. These extrasolar moons, or exomoons, might be a little bit difficult to distinguish with our current equipment, but our technological grasp has greatly improved in recent years. Now current studies suggest that not only can these naturally occurring satellites exist – but they also might be habitable.

As we know, there isn’t exactly a lack of planetary candidates hospitable to life. At least 40 so far discovered are within Earth-like tolerances and it’s only a matter of time before transit timings (TTV and TDV) and wobble variations will allow us to detect their moons. If the potential is there for the giant planet – then why not its companion?

“The satellites of extrasolar planets (exomoons) have been recently proposed as astrobiological targets. Since giant planets in the habitable zone are thought to have migrated there,” says Simon Porter of Lowell Observatory and William Grundy of Arizona State University. “It is possible that they may have captured a former terrestrial planet or planetesimal.”

Although we’re aware of life-possible exoplanet existence, we’re not yet sure of how they got to their current position. Simulations show they may have formed on the edge of where ice can exist, but this might also make them a bit inhospitable. Disk migration would bring them closer to the parent star – but also make them intolerably hot. Yet, there’s a theory which says during the shuffle that some planetesimals could have been “swapped” in the process.

“We therefore attempt to model the dynamical evolution of a terrestrial planet captured into orbit around a giant planet in the habitable zone of a star.” says Porter and Grundy. “We find that approximately half of loose elliptical orbits result in stable circular orbits over timescales of less than a few million years. We also find that those orbits are mostly low-inclination, but have no prograde/retrograde preference.”

Right now the most probable candidates for “living” exomoons would be around planets very similar to Neptune and orbiting a star similar to our Sun. Once these Earth-massed satellites have stabilized into a long-lived orbit, they should be within the range of findability using the transit timing variation much stronger than the duration variation – even if their orbit is tight to the parent planet.

“In addition, we calculate the transit timing and duration variations for the resulting systems, and find that potentially habitable Earth-mass exomoons should be detectable.” reports the team. “Even with these closer orbits, some exomoons are still within the range of detectability. The combination of TTV and TDV may offer a stronger detection signal than photometry for these orbits, though both could detect some of the orbits produced.”

Abstract Information: Post-Capture Evolution of Potentially Habitable Exomoons.

June 17, 2011December 24, 2015 by Tammy Plotner

EPOXI Encounters Energetic Comet Hartley 2

Jets can be seen streaming out of the nucleus, or main body, of comet Hartley 2 in this image from NASA's EPOXI mission. The nucleus is approximately 2 kilometers (1.2 miles) long and .4 kilometers (.25 miles) across at the narrow "neck." Credit: NASA/JPL-Caltech/UMD

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No, EPOXI isn’t the name of a new super glue, but an abbreviation for the continuation of Deep Impact. While the original mission to study Comet 9P/Tempel was a huge success, the spacecraft continues to explore objects of opportunity. Its name is derived from Extrasolar Planet Observations and Characterization (EPOCh) and the Deep Impact Extended Investigation (DIXI)… and it’s now fulfilling another goal as it swings by Comet Hartley 2. It approached, encountered and departed, sending back 117,000 images and spectral findings – along with some surprising observations.

“From all the imaging we took during approach, we knew the comet was a little skittish even before flyby,” said EPOXI Project Manager Tim Larson of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It was moving around the sky like a knuckleball and gave my navigators fits, and these new results show this little comet is downright hyperactive.”

What EPOXI found was a “hyperactive comet” – one that didn’t react in anticipated ways. From a distance of 431 miles (694 kilometers), the spacecraft watched as water and carbon-dioxide jets erupted from the flying space rock’s surface. While this in itself isn’t unusual, the fact that it didn’t happen uniformly caused scientists to sit up and take notice. Jets occurred at both ends of the comet with the strongest activity centered on the small end. Water vapor ejected from the central portion showed a notable lack of carbon-dioxide and ice, leading investigators to speculate the material was re-deposited from the ends of Hartley 2.

“Hartley 2 is a hyperactive little comet, spewing out more water than most other comets its size,” said Mike A’Hearn, principal investigator of EPOXI from the University of Maryland, College Park. “When warmed by the sun, dry ice — frozen carbon dioxide — deep in the comet’s body turns to gas jetting off the comet and dragging water ice with it.”

Hartley2_CN_coma — A large, diffuse cloud of CN gas surrounds the nucleus of Hartley 2 in this image from NASA's EPOXI mission. The gas forms a cloud of more than 200,000 kilometers (about 124,000 miles) in radius, compared to the comet's size of about 2 kilometers (1.24 miles). Credit: NASA/JPL-Caltech/UMD

Is Hartley 2 unique? No. Scientists are aware of at least a dozen comets that behave similarly, but this is the first we’ve been able to examine closely via a spacecraft. These odd comets are extremely active for their size and may be driven by carbon dioxide or carbon monoxide. “These could represent a separate class of hyperactive comets,” said A’Hearn. “Or they could be a continuum in comet activity extending from Hartley 2-like comets all the way to the much less active, “normal” comets that we are more used to seeing.”

What makes this new class of comets so unusual? Just three ingredients: deposits around the inactive center which may have originated at the ends, a tumbling state of rotation and a large end containing ubiquitous inclusions which can span`approximately 165 feet (50 meters) high and 260 feet (80 meters) wide. EPOXI also picked up another surprise at Hartley 2’s smaller end – shiny cubicals reaching 16 stories tall and two to three times more reflective than other average surface materials. But that’s not all. For nine days in September, the energetic comet expelled 10 million times more CN gas in its coma – a dramatic and unexpected change called the “CN anomaly”. It was analyzed by McFadden and Dennis Bodewits, a former postdoctoral fellow at NASA Goddard who is now at the University of Maryland, and their colleagues. This comet exhaust normally includes a similar amount of dust, but not in this case.

“We aren’t sure why this dramatic change happened,” says McFadden. “We know that Hartley 2 gives off considerably more CN gas than comet Tempel 1, which was studied earlier by a probe released by the Deep Impact spacecraft. But we don’t know why Hartley 2 has more CN, and we don’t know why the amount coming off the comet changed so drastically for a short period of time. We’ve never seen anything like this before.”

Until now…

Original Story Source: NASA Mission News.