Astronomy Without A Telescope – The Unlikeliness Of Being

The search for extraterrestrial intelligence could be a waste of time according to a recent statistical analysis of the likelihood of life arising spontaneously on habitable-zone exoplanets out there in the wider universe (and when have predictive statistics ever got it wrong?). Credit: SETI Institute.

History has proved time and again that mathematical modelling is no substitute for a telescope (or other data collection device). Nonetheless, some theoreticians have recently put forward a statistical analysis which suggests that life is probably very rare in the universe – despite the apparent prevalence of habitable-zone exoplanets, being found by the Kepler mission and other exoplanet search techniques.

You would be right to be skeptical, given the Bayesian analysis undertaken is based on our singular experience of abiogenesis – being the origin of life from non-life, here on Earth. Indeed, the seemingly rapid abiogenesis that occurred on Earth soon after its formation is suggested to be the clinching proof that abiogenesis on habitable-zone exoplanets must be rare. Hmm…

Bayes theorem provides a basis for estimating the likelihood that a prior assumption or hypothesis (e.g. that abiogenesis is common on habitable-zone exoplanets) is correct, using whatever evidence is available. Its usage is nicely demonstrated in solving the Monty Hall problem.

Go here for the detail, but in a nutshell:
There are three doors, one with a car behind it and the other two have goats. You announce which door you will pick – knowing that it carries a 1/3 probability of hiding the car. Then Monty Hall, who knows where the car is, opens another door to reveal a goat. So, now you know that door always had a zero probability of hiding the car. So, the likelihood of the remaining door hiding the car carries the remaining 2/3 probability of the system, since there was always an absolute 1/1 probability that the car was behind one of the three doors. So, it makes more sense for you to open that remaining door, instead of the first one you picked.

In this story, Monty Hall opening the door with a goat represents new data. It doesn’t allow you to definitively determine where the car is, but it does allow you to recalculate the likelihood of your prior hypothesis (that the car is behind the first door you picked) being correct.

Applying Bayesian analysis to the problem of abiogenesis on habitable-zone exoplanets is a bit of a stretch. Speigel and Turner argue that the evidence we have available to us – that life began quite soon after the Earth became habitable – contributes nothing to estimating the likelihood that life arises routinely on habitable-zone exoplanets.

We need to acknowledge the anthropic nature of the observation we are making. We are here after 3.5 billion years of evolution – which has given us the capacity to gather together the evidence that life began here 3.5 billion years ago, shortly after the Earth became habitable. But that is only because this is how things unfolded here on Earth. In the absence of more data, the apparent rapidity of abiogenesis here on Earth could just be a fluke.

Stromatolites - which were a fairly early form of life on Earth. Earth became inhabited by such early life shortly after it became habitable. This might seem suggestive that life is somewhat inevitable when the conditions are right. But a statistician is never going to buy such an argument when it's based on a single example.

This is a fair point, but a largely philosophical one. It informs the subsequent six pages of Spiegel and Turner’s Bayesian analysis, but it is not a conclusion of that analysis.

The authors seek to remind us that interviewing one person and finding that she or he likes baked beans does not allow us to conclude that most people like baked beans. Yes agree, but that’s just statistics – it’s not really Bayesian statistics.

If we are ever able to closely study an exoplanet that has been in a habitable state for 3.5 billion years and discover that either it has life, or that it does not – that will be equivalent to Monty Hall opening another door.

But for now, we might just be a fluke… or we might not be. We need more data.

Further reading: Spiegel and Turner. Life might be rare despite its early emergence on Earth: a Bayesian analysis of the probability of abiogenesis.

Tagged as: Bayesian analysis

View the original article here

New Webb Telescope Technologies Already Helping Human Eyes

Image of the Scanning Shack Hartmann System (SSHS), a pair of large mirror test stations used to measure the mirror segments of the Webb telescope. As part of that SSHS program, several improvements were made to the wavefront sensor technology that now allow eye health instruments to be aligned more precisely. Credit: Abbott Medical Optics Inc.

Editor’s note: This NASA press release provides just one example of how developing technology for space missions often has practical, beneficial and sometimes unintended applications on Earth.

Even while construction of the James Webb Space Telescope is underway on the most advanced infrared vision of any space observatory, its technologies are already proving useful to human eye health here on Earth.

“The Webb telescope program has enabled a number of improvements in measurement technology for astronomy, mirror fabrication, and measurement of human eyes, diagnosis of ocular diseases and potentially improved surgery,” said Dr. Dan Neal, Research Fellow at Abbott Medical Optics Inc. in Albuquerque, N.M.

The Webb telescope will be the most scientifically powerful telescope NASA has ever built — 100 times more powerful than the Hubble Space Telescope. The Webb telescope will find the first galaxies that formed in the early universe, connecting the Big Bang to our own Milky Way Galaxy. It will also peer through dusty clouds to see stars and planets being born, connecting star formation in our own galaxy with the solar system.

“The advanced wavefront sensing technology developed for testing the Webb telescope’s 18 primary mirrors led to the new applications in other areas,” said Tony Hull of L3 Integrated Optical Systems Division-Tinsley Facility in Richmond, Calif., where the Webb’s mirrors were recently polished to accuracies of less than one millionth of an inch.

“Wavefront sensing” is used to measure shape of the mirrors during fabrication and control the optics once the telescope is in orbit.

Ophthalmologists routinely use wavefront technology to measure aberrations of the eye. Those measurements help with diagnosis, research, characterization and planning treatment of eye health issues.

“The technology also provides more accurate eye measurements for people about to undergo Laser Refractive Surgery,” Neal said. “To date 10-12 million eyes have been treated with Lasik procedures in the U.S. alone. As technology improves, so does the quality of these procedures.”

James Webb Space Telescope. Credit: NASA

A new “scanning and stitching” technology developed for the Webb telescope led to a number of innovative instrument concepts for more accurate measurement for contact lenses and intra-ocular lenses. Another benefit to eye health is that this technique can help “map” the topography of the eye more accurately.

Think of the surface of your eye as being as dented as the surface of the moon. Precise measurements of your eye’s surface are helpful when assessing eyes for contact lenses. The scanning and stitching technology improvements have enabled eye doctors to get much more detailed information about the shape and “topography” of your eye, and do it in seconds rather than hours. Four patents have been issued as result of innovations driven by the Webb telescope program. “These tools are now used to align and build the next generation of measuring devices for human eyes,” Neal said.

“The lasting impact of the Webb telescope may go beyond the vision of astronomers seeking to see the distant universe; the impact may be a better national technology base and better vision for people everywhere,” Hull said.

NASA’s Innovative Partnerships Program Office (IPPO) is making available wavefront sensing and adaptive optics technologies, procedures and lab equipment to private industry through its “Can you See it Now?” campaign. All of the technologies associated with the campaign are available for licensing and can be found at http://ipp.gsfc.nasa.gov/wavefront.

Tagged as: James Webb Space Telescope, Technology

View the original article here

Astronomy Without A Telescope – Gravitational Waves

An artist's impression of gravitational waves. In reality, a single uniform massive object does not generate gravitational waves. However, a massive binary system in orbital motion, could generate dynamic pulses of gravitational energy that might be detected from Earth. Credit: NASA.

Gravitational waves have some similar properties to light. They move at the same speed in a vacuum – and with a certain frequency and amplitude. Where they differ from light is that they are not scattered or absorbed by matter, in the way that light is.

Thus, it’s likely that primordial gravitational waves, that are speculated to have been produced by the Big Bang, are still out there waiting to be detected and analyzed.

Gravitational waves have been indirectly detected via observations of pulsar PSR 1913+16, a member of a binary system, the orbit of which decays at the rate of approximately three millimetres per orbit. The inspiraling of the binary (i.e. the decay of its orbit) can only be explained by an invisible loss of energy, which we presume to be the result of gravitational waves transporting energy away from the system.

Direct observation of gravitational waves currently escapes us – but seems at least feasible by monitoring the alignment of widely separated test masses. Such monitoring systems are currently in place on Earth, including LIGO, which has test masses separated by up to four kilometres – that separation distance being monitored by lasers designed to detect tiny changes in that distance, which might result from the passage of a gravitational wave initiated from a distant point in the universe.

The passing of a gravitational wave should stretch and contract the Earth. This is not because it strikes the Earth and imparts kinetic energy to it – like an ocean wave hitting land. Instead, the Earth – which sits within space-time – has its geometry altered, so that it continues to fit the momentarily stretched and then contracted space-time within which it sits, as a gravitational wave passes.

The Laser Interferometer Gravitational-Wave Observatory (LIGO) Hanford installation. When you are talking gravitational wave astronomy, big is good. Credit: Caltech.

Gravitational waves are thought to be unaffected by interaction with matter and they move at the speed of light in a vacuum, regardless of whether or not they themselves are in a vacuum. They do lose amplitude (wave height) over distance, but only through attenuation. This is similar to the way that a water wave, emanating from the point of impact of a pebble dropped into a pond, loses amplitude proportionally to the square of the radius of the growing circle that it forms.

Gravity waves may also decline in frequency (i.e. increase in wavelength) over very large distances, due to the expansion of the universe – in much the same way that the wavelength of light is red-shifted by the expansion of the universe.

Given all this, the exceedingly tiny effects that are expected of the gravitational waves that may routinely pass by Earth create a substantial challenge for detection and measurement – since these tiny space-time fluctuations must be distinguished from any background noise.

The noise background for LIGO includes seismic noise (i.e. intrinsic movements of the Earth), instrument noise (i.e. temperature changes that affect the alignment of the detection equipment) and a quantum-level noise, also known as Johnson-Nyquist noise – which arises from the quantum indeterminacy of photon positions.

Kip Thorne, one of the big names in gravity wave theory and research, has apparently ironed out that last and perhaps most troublesome effect through the application of quantum non-demolition principles – which enable the measurement of something without destroying it, or without collapsing its wave function.

Nonetheless, the need for invoking quantum non-demolition principles is some indication of the exceedingly faint nature of gravitational waves – which have a generally weak signal strength (i.e. small amplitude) and low frequency (i.e. long, in fact very long, wavelength).

Where visible light may be 390 nanometres and radio light may be 3 metres in wavelength – gravitational waves are more in the order of 300 kilometres for an average supernova blast, up to 300,000 kilometres for an inspiraling black hole binary and maybe up to 3 billion light years for the primordial echoes of the Big Bang.

So, there’s a fair way to go with all this at a technological level – although proponents (as proponents are want) say that we are on the verge of our first confirmed observation of a gravitational wave – or otherwise they reckon that we have already collected the data, but don’t fully know how to interpret them yet.

This is the current quest of citizen science users of Einstein@Home – the third most popular BOINC distributed computing project after SETI@Home (spot an alien) and Rosetta@Home (fold a protein).

This article follows a public lecture delivered by Kip Thorne at the Australian National University in July 2011 – where he discussed plans for LIGO Australia and also the animated simulations of black hole collisions described in the paper below – which may provide templates to interpret the waveforms that will be detected in the future by gravitational wave observatories.

Further reading: Owen et al (including Thorne, K.) Frame-Dragging Vortexes and Tidal Tendexes Attached to Colliding Black Holes: Visualizing the Curvature of Spacetime.

Tagged as: gravitational waves; LIGO

View the original article here

XCOR Lynx Slated to Fly New Suborbital Telescope

Artist rendering of the XCOR Lynx outfitted with the Atsa Suborbital Observatory. Credit: XCOR

Commercial space company XCOR Aerospace has signed a “Memorandum of Understanding” with the Planetary Science Institute, laying the groundwork for flying a human-operated telescope on board XCOR’s Lynx spacecraft. The Atsa Suborbital Observatory is a specially designed telescope for use in suborbital space vehicles, and when used with commercial suborbital vehicles, PSI says it will provide low-cost space-based observations above the contaminating atmosphere of Earth, while avoiding some operational constraints of satellite telescope systems.

“The XCOR vehicle design and capabilities work well for hosting the kind of observing facility we are developing,” said PSI Senior Scientist Faith Vilas, the Atsa Project Scientist.

“NASA has been flying suborbital observatories for decades, on unmanned, disposable rockets. The new manned, reusable commercial platforms will allow us to make repeated observations with a single instrument, but without the need to refurbish it between flights,” said Luke Sollitt, and affiliate scientist with PSI and a co-inventor with Vilas of the Atsa Observatory. “In addition, the short turn-around means we can do many observations or targets.”

Atsa means “eagle” in the Navajo language. The facility is optimized for observing solar system objects near the sun that are difficult to study from orbital observatories such as Hubble and ground-based telescopes.

The Lynx flight profile. Credit: XCOR

The Lynx is a two-seat, piloted space transport vehicle, capable of taking humans and payloads on a half-hour suborbital flight to 100 km (330,000 feet) and then return safely to a landing at the takeoff runway, providing 4-6 minutes of weightless flight.

Like an aircraft, Lynx is a horizontal takeoff and horizontal landing vehicle, but instead of a jet or piston engine, Lynx uses its own fully reusable rocket propulsion system to depart a runway and return safely.

The Atsa Observatory will be mounted on the top of the Lynx in an experiment pod. XCOR or PSI did not release the cost per flight, but XCOR’s price for one passenger is $95,000 USD. In contrast, the price for using sounding rockets vary, depending on how high the rocket goes, but some cost as little as $10,000 USD.

“These are natural targets for instruments on suborbital rockets to observe, but a human-tended facility using the kind of reusable launch vehicle offered by XCOR offers significant cost savings,” said Mark Sykes, CEO and Director of PSI, who is also a long-time planetary astronomer and is training to be an Atsa operator.

The Lynx spacecraft will fly to space on a customized flight trajectory and will be capable of precision pointing, allowing the Atsa system with its operator to acquire the desired target and make the planned observations. “We are being approached by many potential customers who are interested in supporting observations of the inner solar system,” Vilas said. “We will also be able to support target of opportunity observations for newly discovered objects and other phenomena.”

“We’re looking forward to flying PSI’s Atsa system on Lynx, it will be a groundbreaking experience. The rapid and flexible operations of the Lynx will enable scientists to pick specific targets of interest and the same day fly multiple tailor made observation missions quickly and inexpensively when they want them to be flown,” said Khaki Rodway McKee, XCOR’s Program Manager.

“We are entering into a new era in the human exploration of space, where private companies like XCOR and PSI will begin to play leading roles in certain areas, beginning with suborbital flight – harkening back to the days of NASA’s Mercury program,” Sykes said.

Andrew Nelson, XCOR’s Chief Operating Officer, said, “Much like the early days of the Internet, mobile communications and social networking revolutions saw new and innovative applications drive commercial multi-billion dollar marketplaces, so we are seeing privately funded efforts like PSI’s Atsa as a key early adopter signaling a robust future for suborbital reusable launch vehicles.”

Source: PSI

Tagged as: Atsa Suborbital Observatory, Lynx, Planetary Science Institute, XCOR

View the original article here

Astronomy Without A Telescope – Backgrounds

Thousands of galaxies seen by the Herschel Space Observatory through the Lockman Hole. Credit: ESA.

You’ve probably heard of the cosmic microwave background, but it doesn’t stop there. The as-yet-undetectable cosmic neutrino background is out there waiting to give us a view into the first seconds after the Big Bang. Then, looking further forward, there are other backgrounds across the electromagnetic spectrum – all of which contribute to what’s called the extragalactic background light, or EBL.

The EBL is the integrated whole of all light that has ever been radiated by all galaxies across all of time. At least, all of time since stars and galaxies first came into being – which was after the dark ages that followed the release of the cosmic microwave background.

The cosmic microwave background was released around 380,000 years after the Big Bang. The dark ages may have then persisted for another 750 million years, until the first stars and the first galaxies formed.

In the current era, the cosmic microwave background is estimated to make up about sixty percent of the photon density of all background radiation in the visible universe – the remaining forty per cent representing the EBL, that is the radiation contributed by all the stars and galaxies that have appeared since.

This gives some indication of the enormous burst of light that the cosmic microwave background represented, although it has since been red-shifted into almost invisibility over the subsequent 13.7 billion years. The EBL is dominated by optical and infrared backgrounds, the former being starlight and the latter being dust heated by that starlight which emits infrared radiation.

Just like the cosmic microwave background can tell us something about the evolution of the earlier universe, the cosmic infrared background can tell us something about the subsequent evolution of the universe – particularly about the formation of the first galaxies.

The power density of the universe's background radiation plotted over wavelength. The cosmic microwave background, though substantially red-shifted due to its age, still dominates. The remainder, extragalactic background light, is dominated by optical and infrared radiation, which have power densities several orders of magnitude higher than the remaining radiation wavelengths.

The Photodetector Array Camera and Spectrometer (PACS) Evolutionary Probe is a ‘guaranteed time’ project for the Herschel Space Observatory. Guaranteed means there always a certain amount of telescope time dedicated to this project regardless of other priorities. The PACS Evolutionary Probe project, or just PEP, aims to survey the cosmic infrared background in the relatively dust free regions of the sky that include: the Lockman Hole; the Great Observatories Origins Deep Survey (GOODS) fields; and the Cosmic Evolution Survey (COSMOS) field.

The Herschel PEP project is collecting data to enable determination of rest frame radiation of galaxies out to a redshift of about z =3, where you are observing galaxies when the universe was about 3 billion years old. Rest frame radiation means making an estimation of the nature of the radiation emitted by those early galaxies before their radiation was red-shifted by the intervening expansion of the universe.

The data indicate that infrared contributes around half of the total extragalactic background light. But if you just look at the current era of the local universe, infrared only contributes one third. This suggests that more infrared radiation was produced in the distant past, than in the present era.

This may be because earlier galaxies had more dust – while modern galaxies have less. For example, elliptical galaxies have almost no dust and radiate almost no infrared. However, luminous infrared galaxies (LIRGs) radiate strongly in infrared and less so in optical, presumably because they have a high dust content.

Modern era LIRGs may result from galactic mergers which provide a new supply of unbound dust to a galaxy, stimulating new star formation. Nonetheless, these may be roughly analogous to what galaxies in the early universe looked like.

Dustless, elliptical galaxies are probably the evolutionary end-point of an galactic merger, but in the absence of any new material to feed off these galaxies just contain aging stars.

So it seems that having a growing number of elliptical galaxies in your backyard is a sign that you live in a universe that is losing its fresh, infrared flush of youth.

Further reading: Berta et al Building the cosmic infrared background brick by brick with Herschel/PEP

Tagged as: cosmic infrared background

View the original article here

Astronomy Without A Telescope – Star Seeds

The Rho Ophiuchi cloud complex - within which the cloud L1688 is the most active star-forming location. Although hidden by dust, it is possible to study star formation by sub-millimetre astronomy. Credit NASA.

Molecular clouds are called so because they have sufficient density to support the formation of molecules, most commonly H2 molecules. Their density also makes them ideal sites for new star formation – and if star formation is prevalent in a molecular cloud, we tend to give it the less formal title of stellar nursery.

Traditionally, star formation has been difficult to study as it takes place within thick clouds of dust. However, observation of far-infrared and sub-millimetre radiation coming out of molecular clouds allows data to be collected about prestellar objects, even if they can’t be directly visualized. Such data are drawn from spectroscopic analysis – where spectral lines of carbon monoxide are particularly useful in determining the temperature, density and dynamics of prestellar objects.

Far-infrared and sub-millimetre radiation can be absorbed by water vapor in Earth’s atmosphere, making astronomy at these wavelengths difficult to achieve from sea level – but relatively easy from low humidity, high altitude locations such as Mauna Kea Observatory in Hawaii.

Simpson et al undertook a sub-millimeter study of the molecular cloud L1688 in Ophiuchus, particularly looking for protostellar cores with blue asymmetric double (BAD) peaks – which signal that a core is undergoing the first stages of gravitational collapse to form a protostar. A BAD peak is identified through Doppler-based estimates of gas velocity gradients across an object. All this clever stuff is done via the James Clerk Maxwell Telescope in Mauna Kea, using ACSIS and HARP – the Auto-Correlation Spectral Imaging System and the Heterodyne Array Receiver Programme.

A sample of protostellar cores from cloud L1688 in Ophiuchus. Cores with signature blue asymmetric double (BAD) peaks, indicating gas infall due to gravitational collapse, are all on the right side of the Jeans Instability line. This plot enables the likely evolutionary path of protostellar cores to be estimated. Credit: Simpson et al.

The physics of star formation are not completely understood. But, presumably due to a combination of electrostatic forces and turbulence within a molecular cloud, molecules begin to aggregate into clumps which perhaps merge with adjacent clumps until there is a collection of material substantial enough to generate self-gravity.

From this point, a hydrostatic equilibrium is established between gravity and the gas pressure of the prestellar object – although as more matter is accreted, self-gravity increases. Objects can be sustained within the Bonnor-Ebert mass range – where more massive objects in this range are smaller and denser (High Pressure in the diagram). But as mass continues to climb, the Jeans Instability Limit is reached where gas pressure can no longer withstand gravitational collapse and matter ‘infalls’ to create a dense, hot protostellar core.

When the core’s temperature reaches 2000 Kelvin, H2 and other molecules dissociate to form a hot plasma. The core is not yet hot enough to drive fusion but it does radiate its heat – establishing a new hydrostatic equilibrium between outward thermal radiation and inward gravitational pull. At this point the object is now officially a protostar.

Being now a substantial center of mass, the protostar is likely to draw a circumstellar accretion disk around it. As it accretes more material and the core’s density increases further, deuterium fusion commences first – followed by hydrogen fusion, at which point a main sequence star is born.

Further reading: Simpson et al The initial conditions of isolated star formation – X. A suggested evolutionary diagram for prestellar cores.

Tagged as: sub-millimetre astronomy

View the original article here