Tag: galaxy

Supernova Split into Four Images by Cosmic Lens

W. M. Keck Observatory press release…

Astronomers have for the first time spotted four images of a distant exploding star, arranged in a cross-shape pattern by a powerful gravitational lens. In addition to being a unique sighting, the discovery will provide insight into the distribution of dark matter. The findings will appear March 6 in a special issue of the journal Science, celebrating the centenary of Albert Einstein’s Theory of General Relativity.

LensedSupernova
This image shows the light of a supernova split into four images by a foreground elliptical galaxy embedded in a giant cluster of galaxies. The four images were spotted on Nov. 11, 2014. Credit: NASA/ESA
Two teams spent a week analyzing the object’s light, confirming it was the signature of a supernova, then turned to the W. M. Keck Observatory on Mauna Kea, in Hawaii, to gather critical measurements including determining the distance to the supernova’s host galaxy 9.3 billion light-years from Earth.

To explain the unique, four-up projection, the scientists determined a galaxy cluster and one of its massive elliptical members are gravitationally bending and magnifying the light from the supernova behind it, through an effect called gravitational lensing. First predicted by Albert Einstein, this effect is similar to a glass lens bending light to magnify and distort the image of an object behind it. The multiple images, arranged around the massive elliptical galaxy, form an Einstein Cross, a name originally given to a multiple-lensed quasar that appear as a cross.

Although astronomers have discovered dozens of multiply imaged galaxies and quasars, they have never seen a stellar explosion resolved into several images. “It really threw me for a loop when I spotted the four images surrounding the galaxy – it was a complete surprise,” said Patrick Kelly of the University of California, Berkeley, lead author of the paper and a member of the Grism Lens Amplified Survey from Space (GLASS) collaboration. The GLASS group is working with the FrontierSN team to analyze the supernova.

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Supernova Ejects Galaxy’s Fastest Star

W. M. Keck Observatory press release…

Scientists using the W. M. Keck Observatory and Pan-STARRS1 telescopes on Hawaii have discovered a star that breaks the galactic speed record, traveling with a velocity of about 1,200 kilometers per second or 2.7 million miles per hour. This velocity is so high, the star will escape the gravity of our galaxy. In contrast to the other known unbound stars, the team showed that this compact star was ejected from an extremely tight binary by a thermonuclear supernova explosion. These results will be published in the March 6 issue of Science.

US 708 Supernova Ejected Star
An artist impression of the mass-transfer phase followed by a double-detonation supernova that leads to the ejection of US 708. Credit: ESA/Hubble, NASA, S. Geier
Stars like the Sun are bound to our Galaxy and orbit its center with moderate velocities. Only a few so-called hypervelocity stars are known to travel with velocities so high that they are unbound, meaning they will not orbit the galaxy, but instead will escape its gravity to wander intergalactic space.

A close encounter with the supermassive black hole at the centre of the Milky Way is typically presumed the most plausible mechanism for kicking these stars out of the galaxy.

A team of astronomers led by Stephan Geier (European Southern Observatory, Garching) observed the known high-velocity star know as US 708 with the Echellette Spectrograph and Imager instrument on the 10-meter, Keck II telescope to measure its distance and velocity along our line of sight. By carefully combining position measurements from digital archives with newer positions measured from images taken during the course of the Pan-STARRS1 survey, they were able to derive the tangential component of the star’s velocity (across our line of sight).

Putting the measurements together, the team determined the star is moving at about 1,200 kilometers per second – much higher than the velocities of previously known stars in the Milky Way galaxy. More importantly, the trajectory of US 708 means the supermassive black hole at the galactic center could not be the source of US 708’s extreme velocity.

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Comprehensive Andromeda Study Hints of Violent History

W. M. Keck Observatory press release…

Dots show locations of stars in the Keck Observatory spectroscopic survey superimposed on an image of Andromeda. Credit: Claire Dorman/ESA
Dots show locations of stars in the Keck Observatory spectroscopic survey superimposed on an image of Andromeda. Credit: Claire Dorman/ESA
A detailed study of the motions of different stellar populations in Andromeda galaxy by UC Santa Cruz scientists using W. M. Keck Observatory data has found striking differences from our own Milky Way, suggesting a more violent history of mergers with smaller galaxies in Andromeda’s recent past. The findings are being presented on Thursday, January 8, at the winter meeting of the American Astronomical Society in Seattle.

The structure and internal motions of the stellar disk of a spiral galaxy hold important keys to understanding the galaxy’s formation history. The Andromeda galaxy, also called M31, is the closest spiral galaxy to the Milky Way and the largest in the local group of galaxies.

“In the Andromeda galaxy we have the unique combination of a global yet detailed view of a galaxy similar to our own. We have lots of detail in our own Milky Way, but not the global, external perspective,” said Puragra Guhathakurta, professor of astronomy and astrophysics at the University of California, Santa Cruz.

The new study, led by UC Santa Cruz graduate student Claire Dorman and Guhathakurta, combined data from two large surveys of stars in Andromeda conducted at the Keck Observatory in Hawaii as well as data from the Hubble Space Telescope.

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Evicted? Possible Black Hole Found 2,600 Light Years from Home

W. M. Keck Observatory press release…

Markarian 177 and SDSS1133
Using the Keck II telescope in Hawaii, researchers obtained high-resolution images of Markarian 177 and SDSS1133 using a near-infrared filter. Credit: W. M. Keck Observatory/M. Koss Et Al.
An international team of researchers analyzing decades of observations from many facilities — including the W. M. Keck Observatory on Mauna Kea, the Pan-STARRS1 telescope on Haleakala and NASA’s Swift satellite — has discovered what appears to be a black hole booted from its host galaxy. The team was led by Michael Koss, who was a postdoctoral fellow at the Institute for Astronomy (IfA) at the University of Hawaii at Manoa during most of the time the study was ongoing. The study will be published in the Nov. 21 edition of Monthly Notices of the Royal Astronomical Society.

The mystery object is part of the dwarf galaxy Markarian 177, located in the bowl of the Big Dipper, a well-known star pattern within the constellation Ursa Major. Although supermassive black holes usually occupy galactic centers, SDSS1133 is located at least 2,600 light-years from its host galaxy’s core. The team was able to detect it in astronomical surveys dating back more than 60 years.

In June 2013, the researchers obtained high-resolution near-infrared images of the object using the 10-meter Keck II telescope at Keck Observatory. “When we analyzed the Keck data, we found the emitting region of SDSS1133 is less than 40 light-years across, and that the center of Markarian 177 shows evidence of intense star formation and other features indicating a recent disturbance that matched what we expected for a recoiling black hole,” said Chao-Ling Hung, a UH Manoa graduate student performing the analysis of the Keck Observatory imaging in the study.

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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.

The Cosmic Web
3D map of the cosmic web at a distance of 10.8 billion light years. Credit: Casey Stark (UC Berkeley) AND Khee-Gan Lee (MPIA)
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.

Laniakea Supercluster
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.

GOODS-N-774
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…

H-ATLAS J142935.3-002836
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.