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Posts Tagged ‘gravitational microlensing’

Astronomers ‘Unscramble’ Einstein Ring To Reveal Most Detailed View Ever Of Star Formation In The Distant Universe


Credit: ALMA (NRAO/ESO/NAOJ)/Y. Tamura (The University of Tokyo)/Mark Swinbank (Durham University)

Credit: ALMA (NRAO/ESO/NAOJ)/Y. Tamura (The University of Tokyo)/Mark Swinbank (Durham University)

ALMA’s Long Baseline Campaign produced spectacular images of the distant, gravitationally lensed galaxy called HATLAS J090311.6+003906, otherwise known as SDP.81. New analyses of these images reveal details never before seen in a galaxy so remote, including phenomenally massive yet concentrated clumps of star-forming material.

The ALMA observations of SDP.81, made at the end of 2014, were enabled by a cosmic effect known as gravitational lensing. A large galaxy nestled between SDP.81 and ALMA is acting as a lens, magnifying the more distant galaxy’s light and warping it into a near-perfect example of a phenomenon known as an Einstein Ring.

In the months following these observations, at least seven groups of scientists have independently analyzed the ALMA data on SDP.81. This flurry of research papers has divulged unprecedented information about the galaxy, including details about its structure, contents, motion, and other physical characteristics.

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Mapping Dark Matter, 4.5 Billion light Years Away


Credit: ESA/Hubble, NASA, HST Frontier Fields

Credit: ESA/Hubble, NASA, HST Frontier Fields

Using the NASA/ESA Hubble Space Telescope, an international team of astronomers have mapped the mass within a galaxy cluster more precisely than ever before. Created using observations from Hubble’s Frontier Fields observing programme, the map shows the amount and distribution of mass within MCS J0416.1–2403, a massive galaxy cluster found to be 160 trillion times the mass of the Sun.

The detail in this ‘mass map’ was made possible thanks to the unprecedented depth of data provided by new Hubble observations, and the cosmic phenomenon known as strong gravitational lensing. The team, led by Dr Mathilde Jauzac of Durham University in the UK and the Astrophysics & Cosmology Research Unit in South Africa, publish their results in the journal Monthly Notices of the Royal Astronomical Society.

Measuring the amount and distribution of mass within distant objects in the Universe can be very difficult. A trick often used by astronomers is to explore the contents of large clusters of galaxies by studying the gravitational effects they have on the light from very distant objects beyond them. This is one of the main goals of Hubble’s Frontier Fields, an ambitious observing programme scanning six different galaxy clusters — including MCS J0416.1–2403.

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Hubble Shows Farthest Lensing Galaxy Yields Clues To Early Universe


Credit: NASA, ESA, K.-V. Tran (Texas A&M University), and K. Wong (Academia Sinica Institute of Astronomy & Astrophysics)

Credit: NASA, ESA, K.-V. Tran (Texas A&M University), and K. Wong (Academia Sinica Institute of Astronomy & Astrophysics)

Astronomers using NASA’s Hubble Space Telescope have unexpectedly discovered the most distant cosmic magnifying glass, produced by a monster elliptical galaxy. Seen here as it looked 9.6 billion years ago, this monster elliptical galaxy breaks the previous record holder by 200 million years. These “lensing” galaxies are so massive that their gravity bends, magnifies, and distorts light from objects behind them, a phenomenon called gravitational lensing.

The object behind the cosmic lens is a tiny spiral galaxy undergoing a rapid burst of star formation. Its light has taken 10.7 billion years to arrive here. Seeing this chance alignment at such a great distance from Earth is a rare find.

Locating more of these distant lensing galaxies will offer insight into how young galaxies in the early universe built themselves up into the massive dark-matter-dominated galaxies of today. Dark matter cannot be seen, but it accounts for the bulk of the universe’s matter.

“When you look more than 9 billion years ago in the early universe, you don’t expect to find this type of galaxy-galaxy lensing at all,” explained lead researcher Kim-Vy Tran of Texas A&M University in College Station. “It’s very difficult to see an alignment between two galaxies in the early universe.”

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Hubble Astronomers Use Supernovae To Gauge Power Of Cosmic Lenses


Distant exploding stars observed by NASA’s Hubble Space Telescope are providing astronomers with a powerful tool to determine the strength of naturally-occurring “cosmic lenses” that are used to magnify objects in the remote universe.

Two teams of astronomers, working independently, observed three such exploding stars, called supernovae. Their light was amplified by the immense gravity of massive galaxy clusters in the foreground — a phenomenon called gravitational lensing. Astronomers use the gravitational lensing effect to search for distant objects that might otherwise be too faint to see, even with today’s largest telescopes.

“We have found supernovae that can be used like an eye chart for each lensing cluster,” explained Saurabh Jha of Rutgers University in Piscataway, N.J., a member of the Cluster Lensing and Supernova survey with Hubble (CLASH) team. “Because we can estimate the intrinsic brightness of the supernovae, we can measure the magnification of the lens.”

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‘Upside-Down Planet’ Reveals New Method For Studying Binary Star Systems


Simulation. Credit: NASA

Simulation. Credit: NASA

What looked at first like a sort of upside-down planet has instead revealed a new method for studying binary star systems, discovered by a University of Washington student astronomer.

Working with UW astronomer Eric Agol, doctoral student Ethan Kruse has confirmed the first “self-lensing” binary star system — one in which the mass of the closer star can be measured by how powerfully it magnifies light from its more distant companion star. Though our sun stands alone, about 40 percent of similar stars are in binary (two-star) or multi-star systems, orbiting their companions in a gravitational dance.

Kruse’s discovery confirms an astronomer’s prediction in 1973, based on stellar evolution models of the time, that such a system should be possible. A paper by Kruse and Agol was published in the April 18 edition of Science.

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Faraway Moon Or Faint Star? Possible Exomoon Found


Titan, Europa, Io and Phobos are just a few members of our solar system’s pantheon of moons. Are there are other moons out there, orbiting planets beyond our sun?

NASA-funded researchers have spotted the first signs of an “exomoon,” and though they say it’s impossible to confirm its presence, the finding is a tantalizing first step toward locating others. The discovery was made by watching a chance encounter of objects in our galaxy, which can be witnessed only once.

“We won’t have a chance to observe the exomoon candidate again,” said David Bennett of the University of Notre Dame, Ind., lead author of a new paper on the findings appearing in the Astrophysical Journal. “But we can expect more unexpected finds like this.”

The international study is led by the joint Japan-New Zealand-American Microlensing Observations in Astrophysics (MOA) and the Probing Lensing Anomalies NETwork (PLANET) programs, using telescopes in New Zealand and Tasmania. Their technique, called gravitational microlensing, takes advantage of chance alignments between stars. When a foreground star passes between us and a more distant star, the closer star can act like a magnifying glass to focus and brighten the light of the more distant one. These brightening events usually last about a month.

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NASA Hubble Team Finds Monster “El Gordo” Galaxy Cluster Bigger Than Thought


Image Credit: NASA, ESA, and J. Jee (University of California, Davis)

Image Credit: NASA, ESA, and J. Jee (University of California, Davis)

NASA’s Hubble Space Telescope has weighed the largest known galaxy cluster in the distant universe, catalogued as ACT-CL J0102-4915, and found it definitely lives up to its nickname — El Gordo (Spanish for “the fat one”).

By measuring how much the cluster’s gravity warps images of galaxies in the distant background, a team of astronomers has calculated the cluster’s mass to be as much as 3 million billion times the mass of our sun. Hubble data show the galaxy cluster, which is 9.7 billion light-years away from Earth, is roughly 43 percent more massive than earlier estimates.

The team used Hubble to measure how strongly the mass of the cluster warped space. Hubble’s high resolution allowed measurements of so-called “weak lensing,” where the cluster’s immense gravity subtly distorts space like a funhouse mirror and warps images of background galaxies. The greater the warping, the more mass is locked up in the cluster.

“What I did is basically look at the shapes of the background galaxies that are farther away than the cluster itself,” explained lead author James Jee of the University of California at Davis. “It’s given us an even stronger probability that this is really an amazing system very early in the universe.”

A fraction of this mass is locked up in several hundred galaxies that inhabit the cluster and a larger fraction is in hot gas that fills the entire volume of the cluster. The rest is tied up in dark matter, an invisible form of matter that makes up the bulk of the mass of the universe.

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