Discovery – Page 7 – A Darker View

The Sky Is Falling

Yes… The sky is falling… Literally.

Anyone who spends a good amount of time observing the night sky is well aware of how common meteors are. On any given night you will see five to ten meteors an hour is you observe carefully from a dark site. This rate goes up dramatically during a meteor shower. Most of the meteors you will see are quite small, ranging from dust grains to smallish sand sized bits. Anything large can be quite spectacular. Something the size of a pebble will create a bright meteor, a bright fireball that streaks across the sky.

Bolide Events from 1994 to 2013 — The graphic shows atmospheric impact events from 1994 to 2013, credit NASA’s Near Earth Object (NEO) Program

I have personally witnessed many bright fireballs, it is just a function of how much time you spend outside at night. Meteors that are bright enough to light up the landscape, that leave glowing trains of vapor behind, clouds that last for many minutes, that twist and drift in the high atmospheric winds.

Estimates vary widely, but something like 50,000 tons of meteoric material rains down on the Earth every year. The process that allowed our planet to form continues to this day.

Occasionally a larger object enters the atmosphere. Something big enough to reach the ground intact. Or even something big enough to cause damage from the impact. How often this occurs would be a surprise to most of our fellow citizens who pay little attention to the the natural world around them.

The Chelyabinsk event got the world’s attention. A medium sized object exploded in the atmosphere directly over a mid-sized city causing modest damage. Due to the prevalence of camera gear in modern Russia we were treated to an unprecedented view of this event. With historical events like Tunguska, all we have is eyewitness accounts and a few grainy black and white photographs of the damage taken years after the impact. Now we get dozens of videos of the event that detail how it occurred from dozens of viewpoints.

While this event is unusual, it was not unprecedented, objects of this size will continue to impact our planet. Meanwhile the event fades from public awareness, at least until it happens again… Which it will.

To drive home this point researchers at NASA’s Near Earth Object (NEO) Program have released a map of impacts over the last few years. Using atmospheric sensors that detect the pressure wave of the airburst they were able to locate and estimate the size of the larger events. For further details you can read the press release.

The Chelyabinsk meteor can be seen as a large dot over southern Russia. That event may be the largest dot on the map, but it is not alone. It is the number of other dots that may surprise some people. Our planet is impacted regularly.

Mikaelyan Meteor — A meteor breaking up over Groningen, Netherlands, 18:57, 13 Oct 2009, photo by Robert Mikaelyan, used with permission

Astronomers Thrilled by Extreme Storms on Uranus

W. M. Keck Observatory press release…

The normally bland face of Uranus has become increasingly stormy, with enormous cloud systems so bright that for the first time ever, amateur astronomers are able to see details in the planet’s hazy blue-green atmosphere.

“The weather on Uranus is incredibly active,” said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and leader of the team that first noticed the activity when observing the planet with adaptive optics on the W. M. Keck Observatory in Hawaii.

Uranus NIRC2 — Infrared images of Uranus (1.6 and 2.2 microns) obtained on Aug. 6, 2014, with adaptive optics on the 10-meter Keck II telescope. Credit: Imke De Pater (UC Berkeley) & W. M. Keck Observatory

“This type of activity would have been expected in 2007, when Uranus’s once every 42-year equinox occurred and the sun shined directly on the equator,” noted co-investigator Heidi Hammel of the Association of Universities for Research in Astronomy. “But we predicted that such activity would have died down by now. Why we see these incredible storms now is beyond anybody’s guess.”

In all, de Pater, Hammel and their team detected eight large storms on Uranus’s northern hemisphere when observing the planet with the Keck Observatory on August 5 and 6. One was the brightest storm ever seen on Uranus at 2.2 microns, a wavelength that senses clouds just below the tropopause, where the pressure ranges from about 300 to 500 mbar, or half the pressure at Earth’s surface. The storm accounted for 30 percent of all light reflected by the rest of the planet at this wavelength.

When amateur astronomers heard about the activity, they turned their telescopes on the planet and were amazed to see a bright blotch on the surface of a normally boring blue dot.

‘I got it!’

French amateur astronomer Marc Delcroix processed the amateur images and confirmed the discovery of a bright spot on an image by French amateur Régis De-Bénedictis, then in others taken by fellow amateurs in September and October. He had his own chance on Oct. 3 and 4 to photograph it with the Pic du Midi one-meter telescope, where on the second night, “I caught the feature when it was transiting, and I thought, ‘Yes, I got it!’” said Delcroix.

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Mysterious G2 Cloud Near Black Hole Identified

W. M. Keck Observatory press release…

The mystery about a thin, bizarre object in the center of the Milky Way headed toward our galaxy’s enormous black hole has been solved by UCLA astronomers using the W. M. Keck Observatory, home of the two largest telescopes on Earth. The scientists studied the object, known as G2, during its closest approach to the black hole this summer, and found the black hole did not dine on it. The research is published today in the journal Astrophysical Journal Letters.

G2 at the galatic center — An image from W. M. Keck Observatory near infrared data shows that G2 survived its closest approach to the black hole. Credit Andrea Ghez/Gunther Witzel/UCLA Galactic Center Group/W. M. Keck Observatory

While some scientists believed the object was a cloud of hydrogen gas that would be torn apart in a fiery show, Ghez and her team proved it was much more interesting.

“G2 survived and continues happily on its orbit; a gas cloud would not do that,” said Andrea Ghez, UCLA professor of physics and astronomy who holds the Lauren B. Leichtman and Arthur E. Levine Chair in Astrophysics, and directs the UCLA Galactic Center Group. “G2 was completely unaffected by the black hole; no fireworks.”

Instead, the team has demonstrated it is a pair of binary stars that had been orbiting the black hole in tandem and merged together into an extremely large star, cloaked in gas and dust, and choreographed by the black hole’s powerful gravitational field.

“G2 is not alone,” said Ghez, who uses Keck Observatory to study thousands of stars in the neighborhood of the supermassive black hole. “We’re seeing a new class of stars near the black hole, and as a consequence of the black hole.”

Ghez and her colleagues — who include lead author Gunther Witzel, a UCLA postdoctoral scholar in Ghez’s research group, and Mark Morris, a UCLA professor of physics and astronomy — studied the event with both of the 10-meter telescopes at Keck Observatory.

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Scientists Build First Map of Hidden Universe

W. M. Keck Observatory press release…

A team led by astronomers from the Max Planck Institute for Astronomy has created the first three-dimensional map of the ‘adolescent’ Universe, just 3 billion years after the Big Bang. This map, built from data collected from the W. M. Keck Observatory, is millions of light-years across and provides a tantalizing glimpse of large structures in the ‘cosmic web’ – the backbone of cosmic structure.

On the largest scales, matter in the Universe is arranged in a vast network of filamentary structures known as the ‘cosmic web’, its tangled strands spanning hundreds of millions of light-years. Dark matter, which emits no light, forms the backbone of this web, which is also suffused with primordial hydrogen gas left over from the Big Bang. Galaxies like our own Milky Way are embedded inside this web, but fill only a tiny fraction of its volume.

Now a team of astronomers led by Khee-Gan Lee, a post-doc at the Max Planck Institute for Astronomy, has created a map of hydrogen absorption revealing a three-dimensional section of the universe 11 billions light years away – the first time the cosmic web has been mapped at such a vast distance. Since observing to such immense distances is also looking back in time, the map reveals the early stages of cosmic structure formation when the Universe was only a quarter of its current age, during an era when the galaxies were undergoing a major ‘growth spurt’.

The map was created by using faint background galaxies as light sources, against which gas could be seen by the characteristic absorption features of hydrogen. The wavelengths of each hydrogen feature showed the presence of gas at a specific distance from us. Combining all of the measurements across the entire field of view allowed the team a tantalizing glimpse of giant filamentary structures extending across millions of light-years, and paves the way for more extensive studies that will reveal not only the structure of the cosmic web, but also details of its function – the ways that pristine gas is funneled along the web into galaxies, providing the raw material for the formation of galaxies, stars, and planets.

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Earth and The Milky Way Just Got a Few Trillion New Neighbors

W. M. Keck Observatory press release…

Do you know where you live? You probably know your street address and the name of your town, state, and country. But what about your cosmic address — your location among the stars? Thanks to efforts by some astronomers in Hawaii, you can now tell people you live in Laniakea.

Scientists have known for decades that our solar system rests on an outer arm of the Milky Way galaxy. In turn, galaxies are not sprinkled randomly throughout the cosmos; they cluster into groups, which themselves are part of larger groups.

Two views of the Laniakea Supercluster. The outer surface shows the region dominated by Laniakea’s gravity. Credit CEA/SACLAY

What has been known is our Milky Way is part of the Local Group, a collection of galaxies some 10 million light-years across. Now, a team of scientists led by University of Hawaii at Manoa astronomer R. Brent Tully have mapped the boundaries of a “supercluster” of galaxies stretching 500 *million* light-years through space. They named the supercluster “Laniakea,” a Hawaiian word meaning “immense heaven.” The name was suggested by Kapiolani Community College linguist Nawa’a Napoleon as a tribute to the Polynesian sailors who crossed the Pacific, navigating by the stars.

Tully’s team determined Laniakea’s contours using a method similar to the way geographers would map watersheds on Earth. In an article published in the September 2014 issue of Nature, Tully and his co-authors Hélène Courtois, Yehuda Hoffman, and Daniel Pomarède describe how they began by measuring the distance from Earth to more than eight thousand galaxies and observing the galaxies’ movement. From those measurements, they calculated each galaxy’s “peculiar velocity,” or the difference between its observed velocity and the rate at which all galaxies are receding from each other (called the “cosmic expansion”).

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Keck Observatory Gives Astronomers First Glimpse of Monster Galaxy Formation

W. M. Keck Observatory press release…

After years of searching, Yale University astronomers have discovered a window into the early, violent formation of the nuclei of the Universe’s monster galaxies. After spotting a potential candidate with the 2.4-meter Hubble Space Telescope, the team of astronomers pointed the 10-meter Keck II telescope, operated by the W. M. Keck Observatory, to witness the turbulent, star-bursting galactic core forming millions of stars at a ferocious rate. The data collected during their five day run in Hawaii offers important clues about the galaxy’s development as it was 11 billion years ago — just 3 billion years after the Big Bang. The research is being published today in the journal Nature.

This image shows observations of a newly discovered galaxy core dubbed GOODS-N-774. Credit: NASA/ESA

Galaxy formation theories have long suggested that monster elliptical galaxies form from the inside out, creating their dramatically star-studded central cores during early cosmic epochs. But scientists had never been able to observe this core construction — until now.

Only the most powerful telescopes have the ability to look back far enough to gather this important insight. “It’s a formation process that can’t happen anymore,” said Erica Nelson, Yale graduate student and lead author of the paper. “The early universe could make these galaxies, but the modern universe can’t. It was this hotter, more turbulent place — these were boiling cauldrons forging stars.”

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Merging Galaxies in the Distant Universe Through a Gravitational Lens

ESA/Hubble press release…

Galaxy H-ATLAS J142935.3-002836 seen in a composite of Hubble and Keck 2 data, credit NASA/ESA/ESO/W. M. Keck Observatory

The NASA/ESA Hubble Space Telescope and many other telescopes on the ground and in space have been used to obtain the best view yet of a collision that took place between two galaxies when the Universe was only half its current age. The astronomers enlisted the help of a galaxy-sized magnifying glass to reveal otherwise invisible detail.

These new studies of the galaxy have shown that this complex and distant object looks surprisingly like the well-known local galaxy collision, the Antennae Galaxies.

In this picture, which combines views from Hubble and the Keck-II telescope on Hawaii (using adaptive optics), you can see a foreground galaxy that is acting as the gravitational lens. The galaxy resembles how our home galaxy, the Milky Way, would appear if seen edge-on. But around this galaxy there is an almost complete ring — the smeared out image of a star-forming galaxy merger far beyond.

Stormy Weather on Uranus

W. M. Keck Observatory press release…

Weather on any planet can be quite unpredictable. As hurricanes threaten the Aloha State, astronomers working at W. M. Keck Observatory on the island of Hawaii were surprised by the appearance of gigantic swirling storm systems on the distant planet Uranus.

Uranus Storms — Massive storms on Uranus captured August 5 and 6, 2014 as seen by Keck Observatory. Credit Imke de Pater (UC Berkeley)/Keck Observatory

During the Voyager encounter with Uranus in 1986, only a scant handful of dim clouds were seen in its atmosphere. When the planet approached equinox in 2007 (i.e., when the Sun stood high above its equator), large storms developed on the planet, yet most of these faded.

In the past few days, however, astronomers were surprised by a multitude of bright storms on the planet, including one monstrous feature.

“We are always anxious to see that first image of the night of any planet or satellite, as we never know what it might have in store for us,” said Imke de Pater, professor at UC Berkeley and team leader. “This extremely bright feature we saw on UT 6 August 2014 reminds me of a similarly bright storm we saw on Uranus’s southern hemisphere during the years leading up to and at equinox”.

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Observations Reveal Massive Eruptions on Jupiter’s Moon Io

W. M. Keck Observatory Press Release…

Three massive volcanic eruptions occurred on Jupiter’s moon Io within a two-week period, leading astronomers to speculate that these presumed rare “outbursts,” which can send material hundreds of miles above the surface, might be much more common than previously thought. The observations were made using the W. M. Keck Observatory and Gemini Observatory, both near the summit of Mauna Kea, Hawaii.

Io Eruptions — Images of Io obtained at different infrared wavelengths (in microns, μm, or millionths of a meter) with the W. M. Keck Observatory’s 10-meter Keck II telescope on Aug. 15, 2013 (a-c) and the Gemini North telescope on Aug. 29, 2013 (d). Credit: Imke de Pater and Katherine de Kleer, UC Berkely

“We typically expect one huge outburst every one or two years, and they’re usually not this bright,” said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and lead author of one of two papers describing the eruptions. “Here we had three extremely bright outbursts, which suggest that if we looked more frequently we might see many more of them on Io.”

Io, the innermost of Jupiter’s four large “Galilean” moons, is about 2,300 miles across, and, aside from Earth, is the only known place in the solar system with volcanoes erupting extremely hot lava like that seen on Earth. Because of Io’s low gravity, large volcanic eruptions produce an umbrella of debris that rises high into space.

De Pater’s long-time colleague and coauthor Ashley Davies, a volcanologist with NASA’s Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, Calif., said that the recent eruptions resemble past events that spewed tens of cubic miles of lava over hundreds of square miles in a short period of time.

“These new events are in a relatively rare class of eruptions on Io because of their size and astonishingly high thermal emission,” he said. “The amount of energy being emitted by these eruptions implies lava fountains gushing out of fissures at a very large volume per second, forming lava flows that quickly spread over the surface of Io.”

All three events, including the largest, most powerful eruption of the trio on 29 Aug. 2013, were likely characterized by “curtains of fire,” as lava blasted out of fissures perhaps several miles long.

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Ancient Worlds from Another Galaxy Discovered Next Door

W. M. Keck Observatory press release…

An international team of scientists, led by astronomers at Queen Mary University of London, report of two new planets orbiting Kapteyn’s star, one of the oldest stars found near the Sun. One of the newly-discovered planets could be ripe for life as it orbits at the right distance to the star to allow liquid water on its surface. The paper is being published by the Monthly Notices of the Royal Astronomical Society on June 4.

Dutch astronomer Jacobus Kapteyn discovered the star at the end of the 19th century. It is the second fastest moving star in the sky and belongs to the galactic halo, an extended cloud of stars orbiting our galaxy. With a third of the mass of the sun, this red-dwarf can be seen in the southern constellation of Pictor with an amateur telescope.

The astronomers used new data from the 3.6 meter La Silla Observatory in Chile to measure tiny periodic changes in the motion of the star, and followed up with two more high-precision spectrometers to secure the detection: W. M. Keck Observatory’s HIRES instrument installed on the 10-meter Keck I telescope on the summit of Mauna Kea, and PFS at the 6.5 meter Las Campanas Observatory in Chile.

Using the Doppler Effect, which shifts the star’s light spectrum depending on its velocity, the scientists can work out some properties of these planets, such as their masses and periods of orbit.

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