Category: Astronomy

Exploring the cosmos

New Record: Keck Observatory Measures Most Distant Galaxy

W. M. Keck Observatory press release…

A team of astrophysicists using the W. M. Keck Observatory in Hawaii has successfully measured the farthest galaxy ever recorded and more interestingly, captured its hydrogen emission as seen when the Universe was less than 600 million years old. Additionally, the method in which the galaxy called EGSY8p7 was detected gives important insight into how the very first stars in the Universe lit-up after the Big Bang. The paper will be published shortly in the Astrophysical Journal Letters.

Galaxy EGSY8p7
EGSY8p7 is the most distant confirmed galaxy whose spectrum obtained with the W. M. Keck Observatory places it at a redshift of 8.68 at a time when the Universe was less than 600 million years old. Credit: Adi Zitrin, California Institute of Technology
Using Keck Observatory’s powerful infrared spectrograph called MOSFIRE, the team dated the galaxy by detecting its Lyman-alpha emission line – a signature of hot hydrogen gas heated by strong ultraviolet emission from newly born stars. Although this is a frequently detected signature in galaxies close to Earth, the detection of Lyman-alpha emission at such a great distance is unexpected as it is easily absorbed by the numerous hydrogen atoms thought to pervade the space between galaxies at the dawn of the Universe. The result gives new insight into cosmic reionization’, the process by which dark clouds of hydrogen were split into their constituent protons and electrons by the first generation of galaxies.

“We frequently see the Lyman-alpha emission line of hydrogen in nearby objects as it is one of most reliable tracers of star-formation,” said California Institute of Technology (Caltech) astronomer, Adi Zitrin, lead author of the discovery paper. “However, as we penetrate deeper into the Universe, and hence back to earlier times, the space between galaxies contains an increasing number of dark clouds of hydrogen which absorb this signal.”

Recent work has found the fraction of galaxies showing this prominent line declines markedly after when the Universe was about a billion years old, which is equivalent to a redshift of about 6. Redshift is a measure of how much the Universe has expanded since the light left a distant source and can only be determined for faint objects with a spectrograph on a powerful large telescope such as the Keck Observatory’s twin 10-meter telescopes, the largest on Earth.

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Mercury Appears in the Evening Sky

The planet Mercury is starting an evening apparition. The planet should become visible this week just above the fading glow of the setting Sun as a magnitude -1 object. The planet is moving about 1° further from the Sun and higher in the sunset each day, reaching a maximum elongation of 27° on September 4th. This will be the best evening apparition for Mercury in 2015.

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Keck Observatory Astronomer Wins Major Prize

W. M. Keck Observatory press release…

UCLA professor and longtime W. M. Keck Observatory astronomer, Andrea Ghez will be awarded the 2015 Bakerian Medal, the Royal Society’s premiere prize lecture in the physical sciences, the organization announced this week.

Andrea Ghez
Andrea Ghez, Keck Observatory astronomer and UCLA’s Lauren B. Leichtman and Arthur E. Levine Professor of Astrophysics. Credit: Christopher Dibble
“I’m thrilled to receive the Bakerian Medal from the Royal Society,” said Ghez, who is UCLA’s Lauren B. Leichtman and Arthur E. Levine Professor of Astrophysics. “The research that is being recognized is the product of a wonderful collaboration among the scientists in the UCLA Galactic Center Group and the University of California’s tremendous investment in the W. M. Keck Observatory. Having cutting-edge tools and a great team makes discovery easy.”

The medal is accompanied by a cash prize of 10,000 pounds (approximately $15,500), and Ghez will deliver the Bakerian Lecture in London in November. The organization, the oldest scientific academy in continuous existence, cited Ghez’s “acclaimed discoveries using the techniques of optical astronomy, especially her sustained work on the motions and nature of the stars orbiting the black hole in the centre of our Galaxy.”

“All the data for this project came from Keck Observatory,” Ghez said. “We were able to launch this project 20 years ago because of the unique way that Keck Observatory works. We were able to modify instrumentation and try new approaches to data collection in a way that simply isn’t possible at other observatories. Working at Keck Observatory and with the staff there has been an amazing experience.”

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Telescopes Team Up to Find Distant Uranus-Sized Planet Through Microlensing

W. M. Keck Observatory press release…

The W. M. Keck Observatory in Hawaii and NASA’s Hubble Space Telescope have made independent confirmations of an exoplanet orbiting far from its central star. The planet was discovered through a technique called gravitational microlensing. This finding opens a new piece of discovery space in the extrasolar planet hunt: to uncover planets as far from their central stars as Jupiter and Saturn are from our sun. The Hubble and Keck Observatory results will appear in two papers in the July 30 edition of The Astrophysical Journal.

OGLE-2005-BLG-169 Microlensing
A graphic explanation of the microlensing study of OGLE-2005-BLG-169. Credit: NASA, ESA, and A. Feild (STSCI)
The large majority of exoplanets cataloged so far are very close to their host stars because several current planet-hunting techniques favor finding planets in short-period orbits. But this is not the case with the microlensing technique, which can find more distant and colder planets in long-period orbits that other methods cannot detect.

Microlensing occurs when a foreground star amplifies the light of a background star that momentarily aligns with it. If the foreground star has planets, then the planets may also amplify the light of the background star, but for a much shorter period of time than their host star. The exact timing and amount of light amplification can reveal clues to the nature of the foreground star and its accompanying planets.

“Microlensing is currently the only method to detect the planets close to their birth place,” said team member, Jean-Philippe Beaulieu, Institut d’Astrophysique de Paris. “Indeed, planets are being mostly formed at a certain distance from the central star where it is cold enough for volatile compounds to condense into solid ice grains. These grains will then aggregate and will ultimately evolve into planets.”

The system, cataloged as OGLE-2005-BLG-169, was discovered in 2005 by the Optical Gravitational Lensing Experiment (OGLE), the Microlensing Follow-Up Network (MicroFUN), and members of the Microlensing Observations in Astrophysics (MOA) collaborations—groups that search for extrasolar planets through gravitational microlensing.

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Fossil Star Clusters Reveal Their Age

W. M. Keck Observatory press release…

Using a new age-dating method and the W. M. Keck Observatory on Maunakea, an international team of astronomers have determined that ancient star clusters formed in two distinct epochs – the first 12.5 billion years ago and the second 11.5 billion years ago. These results are being published in Monthly Notices of the Royal Astronomical Society.

Cosmic Timeline of Globular Clusters
A cosmic timeline showing the birth of the Universe in a Big Bang 13.7 billion years ago to the present day. Credit: NASA/CXC/SAO and A. Romanowsky
Although the clusters are almost as old as the Universe itself, these age measurements show the star clusters – called globular clusters – are actually slightly younger than previously thought.

“We now think that globular clusters formed alongside galaxies rather than significantly before them,” research team leader, Professor Duncan Forbes of Swinburne University of Technology said.

The new estimates of the star cluster average ages were made possible using data obtained from the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, which was carried out on Keck Observatory’s 10-meter, Keck II telescope. Observations were carried out over years using the powerful DEIMOS multi-object spectrograph fitted on Keck II, which is capable of obtaining spectra of one hundred globular clusters in a single exposure.

DEIMOS breaks the visible wavelengths of objects into spectra, which the team used to reverse-engineer the ages of the globular clusters by comparing the chemical composition of the globular clusters with the chemical composition of the Universe as it changes with time.

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Venus Disappears into the Sunset

The 2015 evening apparition of Venus is drawing to a close. Already quite low in the sky at sunset the planet will disappear into the bright glow over the next couple weeks. Venus will pass through inferior conjunction on August 15th and reappear in the dawn during the first weeks of September.

Accompanying Venus into solar conjuntion is the bright planet Jupiter, continuing their dance in the sunset.

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Found: Earth’s Closest Cousin Yet

W. M. Keck Observatory press release…

The W. M. Keck Observatory has confirmed the first near-Earth-size planet in the “habitable zone” around a sun-like star. This discovery and the introduction of 11 other new small habitable zone candidate planets were originally made by NASA’s Kepler space telescopes and mark another milestone in the journey to finding another “Earth.”

Kepler 452b
This artist’s concept compares Earth (left) to the new planet, called Kepler-452b, which is about 60 percent larger in diameter. Credit: NASA/JPL-Caltech/T. Pyle
“We can think of Kepler-452b as bigger, older cousin to Earth, providing an opportunity to understand and reflect upon Earth’s evolving environment,” said Jon Jenkins, Kepler data analysis lead at NASA’s Ames Research Center in Moffett Field, California, who led the team that discovered Kepler-452b. “It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; about 1.5 billion years longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet.”

The data from Kepler suggested to the team there was a planet causing the light from it’s host star to dim as is orbited around it. The team then turned to ground-based observatories including the University of Texas at Austin’s McDonald Observatory, the Fred Lawrence Whipple Observatory on Mt. Hopkins, Arizona, and the world’s largest telescopes at Keck Observatory on Maunakea, Hawaii for confirmation.

Specifically, the ten-meter Keck I telescope, fitted with the HIRES instrument was used to confirm the Kepler data as well as to more precisely determine the properties of the star, specifically its temperature, surface gravity and metallicity.

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Finding Another Earth

NASA JPL Press Release…

The discovery of a super-Earth-sized planet orbiting a sun-like star brings us closer than ever to finding a twin of our own watery world. But NASA’s Kepler space telescope has captured evidence of other potentially habitable planets amid the sea of stars in the Milky Way galaxy.

Exoplanet Kepler-542b
This artist’s conception of a planetary lineup shows habitable-zone planets with similarities to Earth: from left, Kepler-22b, Kepler-69c, the just announced Kepler-452b, Kepler-62f and Kepler-186f. Last in line is Earth itself. Credit NASA/Ames/JPL-Caltech
To take a brief tour of the more prominent contenders, it helps to zero in on the “habitable zone” around their stars. This is the band of congenial temperatures for planetary orbits — not too close and not too far. Too close and the planet is fried (we’re looking at you, Venus). Too far and it’s in deep freeze. But settle comfortably into the habitable zone, and your planet could have liquid water on its surface — just right. Goldilocks has never been more relevant. Scientists have, in fact, taken to calling this water-friendly region the “Goldilocks zone.”

The zone can be a wide band or a narrow one, and nearer the star or farther, depending on the star’s size and energy output. For small, red-dwarf stars, habitable zone planets might gather close, like marshmallow-roasting campers around the fire. For gigantic, hot stars, the band must retreat to a safer distance.

About a dozen habitable zone planets in the Earth-size ballpark have been discovered so far — that is, 10 to 15 planets between one-half and twice the diameter of Earth, depending on how the habitable zone is defined and allowing for uncertainties about some of the planetary sizes.

The new discovery, Kepler-452b, fires the planet hunter’s imagination because it is the most similar to the Earth-sun system found yet: a planet at the right temperature within the habitable zone, and only about one-and-a-half times the diameter of Earth, circling a star very much like our own sun. The planet also has a good chance of being rocky, like Earth, its discoverers say.

Kepler-452b is more similar to Earth than any system previously discovered. And the timing is especially fitting: 2015 marks the 20th anniversary of the first exoplanet confirmed to be in orbit around a typical star.

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