New Telescope Optics Can Directly View Exoplanets By Hiding Interfering Starlight

By Rebecca Boyle
June 11th, 2012
popsci.com

Sifting Starlight These two images show HD 157728, a nearby star 1.5 times larger than the sun. The star is centered in both images, and its light has been mostly removed by an adaptive optics system and coronagraph belonging to Project 1640, which uses new technology on the Palomar Observatory’s 200-inch Hale telescope to spot planets.

For now, the thousands of potential exoplanets discovered in the past two years are little more than curvy dips on a graph. Astronomers using the Kepler Space Telescope pick them out by examining the way they blot out their own stars’ light as they move through their orbits. But if astronomers could block out the stars themselves, they may be able to see the planets directly. A new adaptive optics system on the storied Palomar Observatory just started doing that — it’s the first of its kind capable of spotting planets outside our solar system.

The new system is called Project 1640, and it creates dark holes around stars that may harbor planets. It removes the blinding glare of starlight so astronomers can see the exoplanets. This is extremely hard to do, said Charles Beichman, executive director of the NASA Exoplanet Science Institute at Caltech. “Imagine trying to see a firefly whirling around a searchlight more than a thousand miles away,” he said in a statement.

Coronagraphs are used to block out starlight so scientists can see what lurks around the stars. But even when you block the brightest light, about half of it can still fuzz up an image, creating speckles and background light that will interfere with images of potential planets. To address this speckly starlight, Project 1640 uses the world’s most advanced adaptive optics system, and four separate instruments on Palomar’s 200-inch Hale telescope that image the infrared light generated by young, warm planets orbiting stars.

Beta Pictoris: This image of the star Beta Pictoris shows a huge planet orbiting the star. The pale blue dots at the center are the planet, shown in two orbital configurations. The black disk is where the star would be; it’s blocked by a coronagraph. But more starlight is visible at the sides, which could potentially be outshining other, smaller planets in this solar system. A new adaptive optics system can remove this shine, too, unveiling new worlds around distant stars.

Its adaptive optics system can make more than 7 million active mirror deformations per second, with a precision level better than one nanometer. Its wave front sensor, which detects the atmosphere-caused deformations of light hitting the telescope, is also sensitive to a nanometer. As the system detects perturbations in the light waves coming into the telescope, it continually adjusts and deforms to block out the light as effectively as possible.

The system can resolve objects 1 million to 10 million times fainter than the object at the center of the image, which is usually the star. With that level of sensitivity, astronomers may be able to see planets.

Now that it’s up and running, as of late June, astronomers have embarked on a three-year survey of hot young stars. The planets they will detect with this method will probably be large hot Jupiters, and so unlikely to contain life — but their moons potentially could. In any event, it’s likely to be yet another major player in the planet-hunting business.

Seen for the First Time: Starless Galaxies

popsci.com
Colin Lecher
June 11th, 2012

Dark Galaxies The illuminating quasar is circled in red. The dark galaxies are in blue. Royal Astronomical Society

Galaxy-building theory says there are stars and there are stage hands. The bright, shining galaxies filled with stars, the theory goes, took star-building gas from somewhere else, but we couldn’t find exactly where the help came from. Now astronomers have likely found that source; starless “dark galaxies” that fed others early in the history of the universe have been seen.

The European Southern Observatory’s Very Large Telescope was able to catch a glimpse of the galaxies for the first time as they were being illuminated by a quasar. Since the galaxies are bad at forming stars on their own, they’re difficult to see without a light source like a quasar, which shines UV light and can cause a fluorescent glow in the starless galaxies. Their existence has been hinted at before, but this marks the first direct look.

Some estimations were also offered by researchers on the properties of these galaxies. The mass of their gas is about 1 billion times that of the Sun’s, and they’re about 100 times less conducive to star-forming than similar neighbors.

The find also validates progressive rock band King Crimson’s early scientific predictions.

The Darkest World: Scientists Discover ‘Darth Vader’ Planet

The distant exoplanet TrES-2b, shown here in an artist's conception, is darker than the blackest coal. It refuses to give back light. Why? That's a mystery

The polarities of darkness and light have been central to human cultural imaginings since our origins.

In the 5th century B.C. there was Zoroastrian religion, based on the eternal battle between darkness (evil) and light (spiritual purity). In the modern world we have the mythic conflict between Luke Skywalker in his white tunic and his black-shrouded, fallen father, Darth Vader. Given our penchant for pulling the world apart into this kind of dichotomy, it is, perhaps, no wonder that the recent discovery of the darkest of dark planets has made news.

A few weeks ago, two astronomers announced the discovery of TrES-2b via the Kepler spacecraft. The planet is a so-called “Hot Jupiter” — a large gas giant orbiting extremely close to its sun-like star (the whole system is about 750 light years away from us).

What makes TrES-2b so remarkable is its refusal to give back light. The scientific word for reflectivity is albedo. The Earth reflects about 37 percent or 0.37 of the light it receives from the sun. That is why we present such a beautiful bright blue face to the universe.

TrES-2b is another story entirely. It bounces back less than 1 percent (0.01) of the light it receives from its star. That means the planet is blacker than coal. Seen from space, TrES-2b would barely be visible.

It is not clear yet why TrES-2b is so dark. It may be that the intense heat from the nearby star has formed strange, light-absorbing compounds in the planet’s atmosphere.

“It’s a mystery as to what’s causing it to be so dark,” co-discover David Kipping told Space.com. “There’s a good chance it’s a chemical we haven’t even thought of yet.”

A world darker than coal, darker than night and darker than the heart of wickedness. You can provide your own metaphor, analogy or back story if you want.

One of the great beauties of science is the way it lets us discover how much richer the world is than our imagination might have conceived. Then our imaginations find their own uses for these discoveries, making the world we find our own.

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