coronagraph

This composite image shows a coronal mass ejection, a type of space weather linked to solar energetic particles, as seen from two space-based solar observatories and one ground-based instrument. The image in gold is from NASA’s Solar Dynamics Observatory, the image in blue is from the Manua Loa Solar Observatory’s K-Cor coronagraph, and the image in red is from ESA and NASA’s Solar and Heliospheric Observatory.

Our constantly-changing sun sometimes erupts with bursts of light, solar material, or ultra-fast energized particles — collectively, these events contribute to space weather. A new study shows that the warning signs of one type of space weather event can be detected tens of minutes earlier than with current forecasting techniques – critical extra time that could help protect astronauts in space. 

Credits: NASA/ESA/SOHO/SDO/Joy Ng and MLSO/K-Cor

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Hubble captures ‘shadow play’ caused by possible planet

Searching for planets around other stars is a tricky business. They’re so small and faint that it’s hard to spot them. But a possible planet in a nearby stellar system may be betraying its presence in a unique way: by a shadow that is sweeping across the face of a vast pancake-shaped gas-and-dust disk surrounding a young star.

The planet itself is not casting the shadow. But it is doing some heavy lifting by gravitationally pulling on material near the star and warping the inner part of the disk. The twisted, misaligned inner disk is casting its shadow across the surface of the outer disk.

These images, taken a year apart by NASA’s Hubble Space Telescope, reveal a shadow moving counterclockwise around a gas-and-dust disk encircling the young star TW Hydrae. The two images at the top, taken by the Space Telescope Imaging Spectrograph, show an uneven brightness across the disk.

Through enhanced image processing (images at bottom), the darkening becomes even more apparent. These enhanced images allowed astronomers to determine the reason for the changes in brightness.

The dimmer areas of the disk, at top left, are caused by a shadow spreading across the outer disk. The dotted lines approximate the shadow’s coverage. The long arrows show how far the shadow has moved in a year (from 2015-2016), which is roughly 20 degrees.

Based on Hubble archival data, astronomers determined that the shadow completes a rotation around the central star every 16 years.

They know the feature is a shadow because dust and gas in the disk do not orbit the star nearly that quickly.

So, the feature must not be part of the physical disk.

The shadow may be caused by the gravitational effect of an unseen planet orbiting close to the star. The planet pulls up material from the main disk, creating a warped inner disk. The twisted disk blocks light from the star and casts a shadow onto the disk’s outer region.

A team of astronomers led by John Debes of the Space Telescope Science Institute in Baltimore, Maryland say this scenario is the most plausible explanation for the shadow they spotted in the stellar system TW Hydrae, located 192 light-years away in the constellation Hydra, also known as the Female Water Snake. The star is roughly 8 million years old and slightly less massive than our sun. Debes’ team uncovered the phenomenon while analyzing 18 years’ worth of archival observations taken by NASA’s Hubble Space Telescope.

“This is the very first disk where we have so many images over such a long period of time, therefore allowing us to see this interesting effect,” Debes said. “That gives us hope that this shadow phenomenon may be fairly common in young stellar systems.”

Debes will present his team’s results Jan. 7 at the winter meeting of the American Astronomical Society in Grapevine, Texas.

Debes’ first clue to the phenomenon was a brightness in the disk that changed with position. Astronomers using Hubble’s Space Telescope Imaging Spectrograph (STIS) first noted this brightness asymmetry in 2005. But they had only one set of observations, and could not make a definitive determination about the nature of the mystery feature.

Searching the archive, Debes’ team put together six images from several different epochs. The observations were made by STIS and by the Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS).

STIS is equipped with a coronagraph that blocks starlight to within about 1 billion miles from the star, allowing Hubble to look as close to the star as Saturn is to our sun. Over time, the structure appeared to move in counter-clockwise fashion around the disk, until, in 2016, it was in the same position as it was in images taken in 2000.

This 16-year period puzzled Debes. He originally thought the feature was part of the disk, but the short period meant that the feature was moving way too fast to be physically in the disk. Under the laws of gravity, disks rotate at glacial speeds. The outermost parts of the TW Hydrae disk would take centuries to complete one rotation.

“The fact that I saw the same motion over 10 billion miles from the star was pretty significant, and told me that I was seeing something that was imprinted on the outer disk rather than something that was happening directly in the disk itself,” Debes said. “The best explanation is that the feature is a shadow moving across the surface of the disk.”

Debes concluded that whatever was making the shadow must be deep inside the 41-billion-mile-wide disk, so close to the star it cannot be imaged by Hubble or any other present-day telescope.

The most likely way to create a shadow is to have an inner disk that is tilted relative to the outer disk. In fact, submillimeter observations of TW Hydrae by the Atacama Large Millimeter Array (ALMA) in Chile suggested a possible warp in the inner disk.

But what causes disks to warp? “The most plausible scenario is the gravitational influence of an unseen planet, which is pulling material out of the plane of the disk and twisting the inner disk,” Debes explained. “The misaligned disk is inside the planet’s orbit.”

Given the relatively short 16-year period of the clocklike moving shadow, the planet is estimated to be about 100 million miles from the star – about as close as Earth is from the sun. The planet would be roughly the size of Jupiter to have enough gravity to pull the material up out of the plane of the main disk. The planet’s gravitational pull causes the disk to wobble, or precess, around the star, giving the shadow its 16-year rotational period.

Recent observations of TW Hydrae by ALMA in Chile add credence to the presence of a planet. ALMA revealed a gap in the disk roughly 93 million miles from TW Hydrae. A gap is significant, because it could be the signature of an unseen planet clearing away a path in the disk.

This new Hubble study, however, offers a unique way to look for planets hiding in the inner part of the disk and probe what is happening very close to the star, which is not reachable in direct imaging by current telescopes. “What is surprising is that we can learn something about an unseen part of the disk by studying the disk’s outer region and by measuring the motion, location, and behavior of a shadow,” Debes said.

“This study shows us that even these large disks, whose inner regions are unobservable, are still dynamic, or changing in detectable ways which we didn’t imagine.”

TOP IMAGES….These images, taken a year apart by NASA’s Hubble Space Telescope, reveal a shadow moving counterclockwise around a gas-and-dust disk encircling the young star TW Hydrae. The two images at the top, taken by the Space Telescope Imaging Spectrograph, show an uneven brightness across the disk. Through enhanced image processing (images at bottom), the darkening becomes even more apparent. These enhanced images allowed astronomers to determine the reason for the changes in brightness. The dimmer areas of the disk, at top left, are caused by a shadow spreading across the outer disk. The dotted lines approximate the shadow’s coverage. The long arrows show how far the shadow has moved in a year (from 2015-2016), which is roughly 20 degrees. Based on Hubble archival data, astronomers determined that the shadow completes a rotation around the central star every 16 years. They know the feature is a shadow because dust and gas in the disk do not orbit the star nearly that quickly. So, the feature must not be part of the physical disk. The shadow may be caused by the gravitational effect of an unseen planet orbiting close to the star. The planet pulls up material from the main disk, creating a warped inner disk. The twisted disk blocks light from the star and casts a shadow onto the disk’s outer region. Credit NASA, ESA, and J. Debes (STScI)


LOWER IMAGE….This diagram reveals the proposed structure of a gas-and-dust disk surrounding the nearby, young star TW Hydrae.The illustration shows an inner disk that is tilted due to the gravitational influence of an unseen companion, which is orbiting just outside the disk.The tilted inner disk is the best explanation for a shadow covering part of the disk’s outer region. The warped disk is blocking light from the star and casting the shadow across the disk. The nature of the darkening was first revealed in Hubble Space Telescope archival observations, which showed that the feature moved around the star at a much faster rate than any phenomenon that would be physically linked to the slowly rotating disk.TW Hydrae is about 8 million years old and resides 192 light-years from Earth. Credit NASA, ESA, and A. Feild (STScI)

Solar System: Things to Know This Week

Has Cassini inspired you? Learn more about dwarf planet Ceres, get the latest images from the Keck Observatory and more!

1. Has Cassini Inspired You?

During nearly two decades in space, Cassini has been a source of inspiration to many. Has Cassini inspired you? Upload your artwork, photos, poems or songs to the social media platform of your choice, such as Instagram, YouTube, Facebook, Twitter or others. Tag it #CassiniInspires. Or, send it directly to: cassinimission@jpl.nasa.gov. We’ll highlight some of the creations on this page. See examples and details at: saturn.jpl.nasa.gov/mission/cassiniinspires/

2. Dawn’s Shines a Light on Ceres

Our Dawn mission has found evidence for organic material on Ceres, a dwarf planet and the largest body in the main asteroid belt between Mars and Jupiter. Learn more: solarsystem.nasa.gov/news/2017/02/17/dawn-discovers-evidence-for-organic-material-on-ceres

3. Into the Vortex

A new device called the vortex coronagraph was recently installed inside NIRC2 (Near Infrared Camera 2) at the W.M. Keck Observatory in Hawaii and has delivered its first images, showing a ring of planet-forming dust around a star, and separately, a cool, star-like body, called a brown dwarf, lying near its companion star.

4. Enceladus: Cassini Cracks the Code of the Icy Moon

A puzzling sensor reading transformed our Cassini Saturn mission and created a new target in the search for habitable worlds beyond Earth, when on Feb. 17, 2005, Cassini made the first-ever close pass over Saturn’s moon. Since our two Voyager spacecraft made their distant flybys of Enceladus about 20 years prior, scientists had anticipated the little moon would be an interesting place to visit. Enceladus is bright white – the most reflective object in the solar system, in fact – and it orbits in the middle of a faint ring of dust-sized ice particles known as Saturn’s E ring. Scientists speculated ice dust was being kicked off its surface somehow. But they presumed it would be, essentially, a dead, airless ball of ice.

What Cassini saw didn’t look like a frozen, airless body. Instead, it looked something like a comet that was actively emitting gas. The magnetometer detected that Saturn’s magnetic field, which envelops Enceladus, was perturbed above the moon’s south pole in a way that didn’t make sense for an inactive world. Could it be that the moon was actively replenishing gases it was breathing into space? Watch the video.

5. Descent Into a Frozen Underworld

Our planet’s southernmost active volcano reaches 12,448 feet (3,794 meters) above Ross Island in Antarctica. It’s a good stand-in for a frozen alien world, the kind we want to send robots to someday. Learn more: solarsystem.nasa.gov/news/2017/02/13/descent-into-a-frozen-underworld

Discover the full list of 10 things to know about our solar system this week HERE.

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How Science Can Learn More About ‘Proxima b’ And All Earth-Like Worlds

“This planet is almost definitely tidally locked to its star, meaning that the same hemisphere always faces the star and the opposite hemisphere always faces away, just like the Moon does to Earth. The star itself is active and flares frequently, meaning that catastrophic radiation impacts the Sun-facing side quite regularly, but never touches the dark side. And the “seasons” are determined by the ellipticity of its orbit, rather than its axial tilt. But there’s still so much left to learn, and we have a number of different technological avenues to explore – including potentially all of them – if we want to learn more about it.”

Now that we’ve learned the nearest star to our Sun, Proxima Centauri, has a rocky planet at the right distance for liquid water, it’s time to consider how we might learn the answers to our burning questions about it and all nearby Earth-like exoplanets. What’s the atmosphere like, and what does it consist of? What does the surface of the world look like, and what’s on it? And is there life, or intelligent life, present at all? There are three ways to conduct these searches, and they’re all complementary. We can use giant ground-based telescopes, including arrays of telescopes, for high-resolution spectroscopic images of these worlds. We can use space-based telescopes with coronagraphs or starshades to image these worlds directly over time. Or we could undertake a journey across space, and visit the system directly to obtain in situ measurements we could never get from afar.

If this doesn’t inspire you to invest in astronomy and learning more about the Universe, perhaps nothing will!

After nearly a decade of development, construction, and testing, the Gemini Planet Imager (GPI) is pointing skyward and collecting light from distant worlds with the help of a special starlight-blocking device, called a coronagraph, built at the American Museum of Natural History.

This is Gemini Planet Imager’s first-light image of the light scattered by a disk of dust orbiting the young star HR4796. The narrow ring is thought to be dust from asteroids or comets left behind by planet formation; some scientists have theorized that the sharp edge of the ring is defined by an unseen planet.

Processing by Marshall Perrin, Space Telescope Science Institute

NASA’s Fleet of Planet-hunters and World-explorers

Around every star there could be at least one planet, so we’re bound to find one that is rocky, like Earth, and possibly suitable for life. While we’re not quite to the point where we can zoom up and take clear snapshots of the thousands of distant worlds we’ve found outside our solar system, there are ways we can figure out what exoplanets light years away are made of, and if they have signs of basic building blocks for life. Here are a few current and upcoming missions helping us explore new worlds:

Kepler

Launched in 2009, the Kepler space telescope searched for planets by looking for telltale dips in a star’s brightness caused by crossing, or transiting, planets. It has confirmed more than 1,000 planets; of these, fewer than 20 are Earth-size (therefore possibly rocky) and in the habitable zone – the area around a star where liquid water could pool on the surface of an orbiting planet. Astronomers using Kepler data found the first Earth-sized planet orbiting in the habitable zone of its star and one in the habitable zone of a sun-like star.

In May 2013, a second pointing wheel on the spacecraft broke, making it not stable enough to continue its original mission. But clever engineers and scientists got to work, and in May 2014, Kepler took on a new job as the K2 mission. K2 continues the search for other worlds but has introduced new opportunities to observe star clusters, young and old stars, active galaxies and supernovae.

Transiting Exoplanet Survey Satellite (TESS)

Revving up for launch around 2017-2018, NASA’s Transiting Exoplanet Survey Satellite (TESS) will find new planets the same way Kepler does, but right in the stellar backyard of our solar system while covering 400 times the sky area. It plans to monitor 200,000 bright, nearby stars for planets, with a focus on finding Earth and Super-Earth-sized planets. 

Once we’ve narrowed down the best targets for follow-up, astronomers can figure out what these planets are made of, and what’s in the atmosphere. One of the ways to look into the atmosphere is through spectroscopy.  

As a planet passes between us and its star, a small amount of starlight is absorbed by the gas in the planet’s atmosphere. This leaves telltale chemical “fingerprints” in the star’s light that astronomers can use to discover the chemical composition of the atmosphere, such as methane, carbon dioxide, or water vapor. 

James Webb Space Telescope

Launching in 2018, NASA’s most powerful telescope to date, the James Webb Space Telescope (JWST), will not only be able to search for planets orbiting distant stars, its near-infrared multi-object spectrograph will split infrared light into its different colors- spectrum- providing scientists with information about an physical properties about an exoplanet’s atmosphere, including temperature, mass, and chemical composition. 

Hubble Space Telescope

Hubble Space Telescope is better than ever after 25 years of science, and has found evidence for atmospheres bleeding off exoplanets very close to their stars, and even provided thermal maps of exoplanet atmospheres. Hubble holds the record for finding the farthest exoplanets discovered to date, located 26,000 light-years away in the hub of our Milky Way galaxy.

Chandra X-ray Observatory

Chandra X-ray Observatory can detect exoplanets passing in front of their parent stars. X-ray observations can also help give clues on an exoplanet’s atmosphere and magnetic fields. It has observed an exoplanet that made its star act much older than it actually is

Spitzer Space Telescope

Spitzer Space Telescope has been unveiling hidden cosmic objects with its dust-piercing infrared vision for more than 12 years. It helped pioneer the study of atmospheres and weather on large, gaseous exoplanets. Spitzer can help narrow down the sizes of exoplanets, and recently confirmed the closest known rocky planet to Earth.

SOFIA

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airplane mounted with an infrared telescope that can fly above more than 99 percent of Earth’s atmospheric water vapor. Unlike most space observatories, SOFIA can be routinely upgraded and repaired. It can look at planetary-forming systems and has recently observed its first exoplanet transit

What’s Coming Next?

Analyzing the chemical makeup of Earth-sized, rocky planets with thin atmospheres is a big challenge, since smaller planets are incredibly faint compared to their stars. One solution is to block the light of the planets’ glaring stars so that we can directly see the reflected light of the planets. Telescope instruments called coronagraphs use masks to block the starlight while letting the planet’s light pass through. Another possible tool is a large, flower-shaped structure known as the starshade. This structure would fly in tandem with a space telescope to block the light of a star before it enters the telescope. 

All images (except SOFIA) are artist illustrations.

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With its C2 coronagraph instrument, SOHO captured a blossoming coronal mass ejection as it roared into space from the right side of the Sun (Dec. 28, 2013). SOHO also produces running difference images and movies of the Sun’s corona in which the difference between one image and the next (taken about 10 minutes apart) is highlighted.

This technique strongly emphasizes the changes that occurred. Here we have taken a single white light frame and shift it back and forth with a running difference image taken at the same time to illustrate the effect.

Credit: SOHO (ESA & NASA)

Science When the Sun Don’t Shine

About once a year, somewhere on Earth, the sun is blocked by the moon. This phenomenon – called a total solar eclipse – is one of the most beautiful natural events.

Blocking the light of the sun during a total solar eclipse reveals the sun’s relatively faint, feathery atmosphere, called the corona. The corona is one of the most interesting parts of the sun. We usually study it using an instrument called a coronagraph, which uses a solid disk to make an artificial eclipse by blocking the sun’s face.

To successfully block all of the sun’s bright light – which can bend around the sharp edges of a coronagraph disk – coronagraphs must block much more than just the face of the sun.  So total solar eclipses are a rare chance to study the lower part of the corona, close to the surface of the sun.   

We have sent a team of scientists to Indonesia, where they’re preparing for an experiment during the March 8, 2016, eclipse, visible from Southeast Asia.

The scientists are measuring a certain kind of light – called polarized light – scattered by electrons in the lower corona, which will help us understand the temperature and speed of these electrons.

The March 8 eclipse is a preview of the total solar eclipse that will be visible across the US in August 2017.

Remember, you should never look directly at the sun – even if the sun is partly obscured. This also applies during a total eclipse up until the time when the sun is completely and totally blocked. More on safety: http://go.nasa.gov/1L6xpnI

For more eclipse information, check out nasa.gov/eclipse

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Dr. Adams photographic print of the solar eclipse (Lick Observatory 12.19 Metre 40 ft. Coronagraph), Sydney Observatory, Wollal, Western Australia, 1922.

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Solar Flares and CME’s: Coronal Mass Ejections 

A Solar Flare is a sudden flash of brightness observed over the Sun’s surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy. They are often, but not always, followed by a colossal coronal mass ejection. The flare ejects clouds of electrons, ions, and atoms through the corona of the sun into space. These clouds typically reach Earth a day or two after the event. The term is also used to refer to similar phenomena in other stars, where the term stellar flare applies.

A Coronal Mass Ejection (CME) is a massive burst of gas and magnetic field arising from the solar corona and being released into the solar wind, as observed in a coronagraph. Coronal mass ejections are often associated with other forms of solar activity, most notably solar flares or filament eruptions, but a broadly accepted theoretical understanding of these relationships has not been established. 

CMEs most often originate from active regions on the Sun’s surface, such as groupings of sunspots associated with frequent flares. Near solar maxima, the Sun produces about three CMEs every day, whereas near solar minima, there is about one CME every five days.

Giffed by: rudescience  From: This video by nasa

Astronomers Debut Vision For Future Space Telescopes

In a meeting today at the American Museum of Natural History, members of the Association of Universities for Research in Astronomy (AURA) presented a roadmap to a powerful space observatory that would allow for greater exploration of planets outside of our solar system, including signs of life.

At its heart is AURA’s vision for a High-Definition Space Telescope (HDST), described by some as a “super-Hubble,”that could improve on that storied telescope’s capabilities by a factor of more than 100. The HDST would be the centerpiece of a space observatory that would also host a suite of specialized instruments, including coronagraphs that can block light from stars and allow astronomers to glimpse nearby objects such as exoplanets.

Read more on the Museum blog

First light for SPHERE exoplanet imager

SPHERE — the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument — has been installed on ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile and has achieved first light. This powerful new facility for finding and studying exoplanets uses multiple advanced techniques in combination. It offers dramatically better performance than existing instruments and has produced impressive views of dust discs around nearby stars and other targets during the very first days of observations. SPHERE was developed and built by a consortium of many European institutes, led by the Institut de Planétologie et d'Astrophysique de Grenoble, France, working in partnership with ESO. It is expected to revolutionise the detailed study of exoplanets and circumstellar discs.

SPHERE passed its acceptance tests in Europe in December 2013 and was then shipped to Paranal. The delicate reassembly was completed in May 2014 and the instrument is now mounted on VLT Unit Telescope 3. SPHERE is the latest of the second generation of instruments for the VLT (the first three were X-shooter, KMOS and MUSE).

SPHERE combines several advanced techniques to give the highest contrast ever reached for direct planetary imaging — far beyond what could be achieved with NACO, which took the first ever direct image of an exoplanet. To reach its impressive performance SPHERE required early development of novel technologies, in particular in the area of adaptive optics, special detectors and coronagraph components.

SPHERE is a very complex instrument. Thanks to the hard work of the many people who were involved in its design, construction and installation it has already exceeded our expectations. Wonderful!” says Jean-Luc Beuzit, of the Institut de Planétologie et d'Astrophysique de Grenoble, France and Principal Investigator of SPHERE.

SPHERE’s main goal is to find and characterise giant exoplanets orbiting nearby stars by direct imaging. This is an extremely challenging task as such planets are both very close to their parent stars in the sky and also very much fainter. In a normal image, even in the best conditions, the light from the star totally swamps the weak glow from the planet. The whole design of SPHERE is therefore focused on reaching the highest contrast possible in a tiny patch of sky around the dazzling star.

The first of three novel techniques exploited by SPHERE is extreme adaptive optics to correct for the effects of the Earth’s atmosphere so that images are sharper and the contrast of the exoplanet increased. Secondly, a coronagraph is used to block out the light from the star and increase the contrast still further. Finally, a technique called differential imaging is applied that exploits differences between planetary and stellar light in terms of its colour or polarisation — and these subtle differences can also be exploited to reveal a currently invisible exoplanet.

Image credit: ESO/J.-L. Beuzit et al./SPHERE Consortium

The future of astronomy: the starshade and exoplanet imaging

“The light from Vega was reduced by more than a factor of one billion, and many new stars that had never been seen before were discovered just by performing this simple test. By blocking the starlight using this new concept — the starshade — we were able to view objects closer to the star than ever before. The next step? Get one into orbit and empower it to work with a Hubble-class (or greater!) optical space telescope. We’ll be able to see the light directly from dozens of rocky planets, for the first time, including their spectra as the planet rotates and revolves in its own orbit.”

25 years ago, there were no planets known around Sun-like stars other than our own. Just 5 years ago, there were no rocky planets known around Sun-like stars other than our own. And today, we don’t have any direct images of those rocky worlds potentially suitable for life. But in just another ten to fifteen years, that might not be true anymore. By blocking out the light in front of a star, you can potentially see the light from the faint planet instead. While conventional coronagraphs might reduce the amount of light transmitted by a factor of one million, a hypergaussian surface at the right distance — a starshade — can reduce the star’s light by a factor of over 10^10, making direct exoplanet imaging possible.