Sorry NASA, but it turns out that a 1917 image on an astronomical glass plate from the Carnegie Institute Observatories' collection shows the first-ever evidence of a planetary system beyond our own Sun. This unexpected find was recognized in the process of researching an article about planetary systems surrounding white dwarf stars in New Astronomy Reviews.

Here's what happened: about a year ago, the review's author, Jay Farihi of University College London, contacted our Observatories' Director, John Mulchaey. He was looking for a plate in the Carnegie archive that contained a spectrum of van Maanen's star (shown above), a white dwarf discovered by Dutch-American astronomer Adriaan van Maanen in the very year our own plate was made.

The 1917 photographic plate spectrum of van Maanen's star from the Carnegie Observatories' archive is shown below. The pull-out box shows the strong lines of the element calcium, which are surprisingly easy to see in the century old spectrum. The spectrum is the thin, (mostly) dark line in the center of the image. The broad dark lanes above and below are from lamps used to calibrate wavelength, and are contrast-enhanced in the box to highlight the two "missing" absorption bands in the star.

Stellar spectra are recordings of the light emitted by distant stars. Spectra spread out all of the component colors of light, like a rainbow from a prism, and they can teach astronomers about a star's chemical composition. They can also tell them how the light emitted by a star is affected by the chemistry of the things it passes through before reaching us on Earth.

Stellar spectra images allowed 19th century astronomers to develop a system for classifying stars that is still used today. Modern astronomers use digital tools to image stars, but for decades, they would use glass photographic plates both to take images of the sky, and to record stellar spectra.

As requested, the Observatories located the 1917 plate, made by former Observatories Director Walter Adams at Mount Wilson Observatory, which was then part of Carnegie. Other than a notation on the plate's sleeve indicating that the star looked a bit warmer than our own Sun, everything seemed very ordinary.

However, when Farihi examined the spectrum, he found something quite extraordinary.

The clue was in what's called an "absorption line" on the spectrum. Absorption lines indicate "missing pieces," areas where the light coming from a star passed through something and had a particular color of light absorbed by that substance. These lines indicate the chemical makeup of the interfering object.

Carnegie's 1917 spectrum of van Maanen's star revealed the presence of heavier elements, such as calcium, magnesium, and iron, which should have long since disappeared into the star's interior due to their weight.

Only within the last 12 years has it become clear to astronomers that van Maanen's star and other white dwarfs with heavy elements in their spectra represent a type of planetary system featuring vast rings of rocky planetary remnants that deposit debris into the stellar atmosphere. These recently discovered systems are called "polluted white dwarfs." They were a surprise to astronomers, because white dwarfs are stars like our own Sun at the end of their lifetimes, so it was not at all expected that they would have leftover planetary material around them at that stage.

The image at the top of the page shows  Camelopardalis, a binary star system with a white dwarf and its companion star, surrounded by shells of ionised gas (NASA/JPL-Caltech)

"The unexpected realization that this 1917 plate from our archive contains the earliest recorded evidence of a polluted white dwarf system is just incredible," Mulchaey said. "And the fact that it was made by such a prominent astronomer in our history as Walter Adams enhances the excitement."

Planets themselves have not yet been detected orbiting van Maanen's star, nor around similar systems, but Farihi is confident it is only a matter of time.

"The mechanism that creates the rings of planetary debris, and the deposition onto the stellar atmosphere, requires the gravitational influence of full-fledged planets," he explained. "The process couldn't occur unless there were planets there."

"Carnegie has one of the world's largest collections of astronomical plates with an archive that includes about 250,000 plates from three different observatories--Mount Wilson, Palomar, and Las Campanas," concluded Mulchaey. "We have a ton of history sitting in our basement and who knows what other finds we might unearth in the future?"

The Daily Galaxy via Carnegie Institute

Image credit: van Maanen's star H. Bond (STSci), R. Ciardullo (PSU), WFPC2, HST, NASA

The Universe is becoming gradually cleaner as more and more cosmic dust is being mopped up by the formation of stars within galaxies, an international team of astronomers has revealed. Peering back 12 billion years using the Herschel space telescope to produce far-infrared images of the sky, the team led by researchers at Cardiff University has been able to observe the very early formation of galaxies and compare them to galaxies that have formed much more recently.

Cosmic dust is comprised of tiny solid particles that are found everywhere in space between the stars. The dust and the gas in the universe is the raw material out of which stars and galaxies form. Though this blanket of material is key to the formation of stars and galaxies, it also acts as a sponge, absorbing almost half of the light emitted by stellar objects and making them impossible to observe with standard optical telescopes.

With the launch of the Herschel space telescope in 2009, researchers were provided with the perfect tool for probing this hidden universe. Owing to a collection of sensitive instruments, mirrors and filters, the Herschel telescope had the capacity to detect the dust through the far-infrared emission it emits, revealing the existence of stars and galaxies hidden by the dust.

Professor Steve Eales, a co-leader of the project from Cardiff University's School of Physics and Astronomy, said: "We were surprised to find that we didn't need to look far in the past to see signs of galaxy evolution. Our results show that the reason for this evolution is that galaxies used to contain more dust and gas in the past, and the universe is gradually becoming cleaner as the dust is used up."

Professor Haley Gomez, also of the School of Physics and Astronomy, presented the team's results today, 29 June, at the National Astronomy Meeting in Nottingham. After seven years of work analysing the images from the Herschel telescope, the team of over 100 astronomers have released a large catalogue of the sources of far-infrared radiation in this 'hidden universe'.

The team's survey of the sky, called the Herschel Astrophysical Terahertz Large Area Survey (Herschel ATLAS), has revealed the details of over half a million galaxies, many of which have been viewed as they were over 12 billion years ago, just shortly after the big bang.

The team are hopeful that this unprecedented catalogue of sources will be vital tools for astronomers wishing to understand the detailed history of galaxies and the wider cosmos.

"Before Herschel we only knew of a few hundred such dusty sources in the distant universe and we could only effectively 'see' them in black and white," said Loretta Dunne, a co-leader of project from Cardiff University's School of Physics and Astronomy, said: Herschel, with its five filters, has given us the equivalent of technicolour, and the colour of the galaxy tell us about their distances and temperatures. So we now have half a million galaxies we can use to map out the hidden star formation in the universe."

The Daily Galaxy via Cardiff University

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"Robots really do dream. We can ask RobERt to dream up what he thinks a water spectrum will look like, and he's proved very accurate," says Ingo Waldmann of University College London. "This dreaming ability has been very useful when trying to identify features in incomplete data. RobERt can use his dream state to fill in the gaps."

Machine-learning techniques that mimic human recognition and dreaming processes are being deployed in the search for habitable worlds beyond our solar system. A deep belief neural network, called RobERt (Robotic Exoplanet Recognition), has been developed by astronomers at UCL to sift through detections of light emanating from distant planetary systems and retrieve spectral information about the gases present in the exoplanet atmospheres.

"Different types of molecules absorb and emit light at specific wavelengths, embedding a unique pattern of lines within the electromagnetic spectrum," explained Dr Waldmann, who leads RobERt's development team. "We can take light that has been filtered through an exoplanet's atmosphere or reflected from its cloud-tops, split it like a rainbow and then pick out the 'fingerprint' of features associated with the different molecules or gases. Human brains are really good at finding these patterns in spectra and label them from experience, but it's a really time consuming job and there will be huge amounts of data.

A neural network's dream of Earth, is shown above. Similar to RobERt dreaming of exoplanet spectra, this neural network was trained to dream in the style of a Monet painting.

We built RobERt to independently learn from examples and to build on his own experiences. This way, like a seasoned astronomer or a detective, RobERt has a pretty good feeling for what molecules are inside a spectrum and which are the most promising data for more detailed analysis. But what usually takes days or weeks takes RobERt mere seconds."

Deep belief neural networks, or DBNs, were developed more than a decade ago and are commonly used for speech recognition, Internet searches and tracking customer behaviour. RobERt's DBN has three layers of unit processors, or 'neurons'. Information is fed into a bottom layer of 500 neurons, which make an initial filter of the data and pass a subset up to the second layer. Here, 200 neurons refine the selection and pass data up to a third layer of 50 neurons to make the final identification of the gases most likely to be present.

To prepare RobERt for his challenge, Waldmann and colleagues at UCL created a total of 85,750 simulated spectra, covering five different types of exoplanet ranging from GJ1214b, a potential "ocean planet," to WASP-12, a hot Jupiter orbiting very close to its star. Each spectrum in the training set contained the fingerprint of a single gas species. RobERt's learning progress was tested at intervals during the training with 'control' spectra. At the end of the training phase, RobERt had a recognition accuracy of 99.7%.

"RobERt has learned to take into account factors such as noise, restricted wavelength ranges and mixtures of gases," said Waldmann. "He can pick out components such as water and methane in a mixed atmosphere with a high probability, even when the input comes from the limited wavebands that most space instruments provide and when it contains overlapping features."

RobERt's DBN can also be reversed so that instead of analysing data fed into the system, he can enter a 'dreaming state' in which he can generate full spectra based on his experiences.

The James Webb Space Telescope, due for launch in 2018, will tell as more about the atmospheres of exoplanets, and new facilities like Twinkle or ARIEL will be coming online over the next decade that are specifically tailored to characterising the atmospheres of exoplanets. The amount of data these missions will provide will be breathtaking. RobERt will play an invaluable role in helping us to analyse data from these missions and find out what these distant worlds are really like."

The Daily Galaxy via Royal Astronomical Society (RAS)

Image credit: Waldmann/UCL/Gatys

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“Suppose there is a civilization like ours and suppose — unlike us, who are skittish about broadcasting our presence — they think it's important to be a beacon, an interstellar or extragalactic lighthouse of sorts,” says University of California  Santa Barbara physicist, Philip Lubin.. “There is a photonics revolution going on on Earth that enables this specific kind of transmission of information via visible or near-infrared light of high intensity."

magine if we sent up a visible signal that could eventually be seen across the entire universe. Imagine if another civilization did the same. Recent photonics advances now allow us to be seen across the universe, with major implications for the search for extraterrestrial intelligence, says Lubin.

Looking up at the night sky — expansive and seemingly endless, stars and constellations blinking and glimmering like jewels just out of reach — it's impossible not to wonder: Are we alone? For many of us, the notion of intelligent life on other planets is as captivating as ideas come. Maybe in some other star system, maybe a billion light years away, there's a civilization like ours asking the exact same question.

The technology now exists to enable exactly that scenario, according to Lubin, whose new work applies his research and advances in directed-energy systems to the search for extraterrestrial intelligence (SETI). His recent paper “The Search for Directed Intelligence” appears in the journal REACH Reviews in Human Space Exploration.

“If even one other civilization existed in our galaxy and had a similar or more advanced level of directed-energy technology, we could detect ‘them' anywhere in our galaxy with a very modest detection approach,” said Lubin, who leads the UCSB Experimental Cosmology Group. “If we scale it up as we're doing with direct energy systems, how far could we detect a civilization equivalent to ours? The answer becomes that the entire universe is now open to us.

“Similar to the use of directed energy for relativistic interstellar probes and planetary defense that we have been developing, take that same technology and ask yourself, ‘What are consequences of that technology in terms of us being detectable by another ‘us' in some other part of the universe?'” Lubin added. “Could we see each other? Can we behave as a lighthouse, or a beacon, and project our presence to some other civilization somewhere else in the universe? The profound consequences are, of course, ‘Where are they?' Perhaps they are shy like us and do not want to be seen, or they don't transmit in a way we can detect, or perhaps ‘they' do not exist.”

The same directed energy technology is at the core of Lubin's recent efforts to develop miniscule, laser-powered interstellar spacecraft. That work, funded since 2015 by NASA (and just selected by the space agency for “Phase II” support) is the technology behind billionaire Yuri Milner's newsmaking, $100-million Breakthrough Starshot initiative announced April 12.

Lubin is a scientific advisor on Starshot, which is using his NASA research as a roadmap as it seeks to send tiny spacecraft to nearby star systems.

In describing directed energy, Lubin likened the process to using the force of water from a garden hose to push a ball forward. Using a laser light, spacecraft can be pushed and steered in much the same way. Applied to SETI, he said, the directed energy system could be deployed to send a targeted signal to other planetary systems.

“In our paper, we propose a search strategy that will observe nearly 100 billion planets, allowing us to test our hypothesis that other similarly or more advanced civilizations with this same broadcast capability exist,” Lubin said.

“As a species we are evolving rapidly in photonics, the production and manipulation of light,” he explained. “Our recent paper explores the hypothesis: We now have the ability to produce light extremely efficiently, and perhaps other species might also have that ability. And if so, then what would be the implications of that? This paper explores the ‘if so, then what?'”

Traditionally and still, Lubin said, the “mainstay of the SETI community” has been to conduct searches via radio waves. Think Jodie Foster in “Contact,” receiving an extraterrestrial signal by way of a massive and powerful radio telescope. With Lubin's UCSB-developed photonics approach, however, making “contact” could be much simpler: Take the right pictures and see if any distant systems are beaconing us.

“All discussions of SETI have to have a significant level of, maybe not humor, but at least hubris as to what makes reason and what doesn't,” Lubin said. “Maybe we are alone in terms of our technological capability. Maybe all that's out there is bacteria or viruses. We have no idea because we've never found life outside of our Earth.

The Daily Galaxy via ucsb.edu

Image credit top of page, NASA-WMAP

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