Universe Today

Image credit: Hubble
An international team of astronomers may have set a new record in discovering what is the most distant known galaxy in the universe. Located an estimated 13 billion light-years away, the object is being viewed at a time only 750 million years after the big bang, when the universe was barely 5 percent of its current age.

The primeval galaxy was identified by combining the power of NASA’s Hubble Space Telescope and CARA’s W. M. Keck Telescopes on Mauna Kea in Hawaii. These great observatories got a boost from the added magnification of a natural “cosmic gravitational lens” in space that further amplifies the brightness of the distant object.

The newly discovered galaxy is likely to be a young galaxy shining during the end of the so-called “Dark Ages” ? the period in cosmic history which ended with the first galaxies and quasars transforming opaque, molecular hydrogen into the transparent, ionized universe we see today.

The new galaxy was detected in a long exposure of the nearby cluster of galaxies Abell 2218, taken with the Advanced Camera for Surveys on board the Hubble Space Telescope. This cluster is so massive that the light of distant objects passing through the cluster actually bends and is amplified, much as a magnifying glass bends and magnifies objects seen through it. Such natural gravitational “telescopes” allow astronomers to see extremely distant and faint objects that could otherwise not be seen. The extremely faint galaxy is so far away its visible light has been stretched into infrared wavelengths, making the observations particularly difficult.

“As we were searching for distant galaxies magnified by Abell 2218, we detected a pair of strikingly similar images whose arrangement and color indicate a very distant object,” said astronomer Jean-Paul Kneib (Observatoire Midi-Pyrenees and Caltech), who is lead author reporting the discovery in a forthcoming article in the Astrophysical Journal.

Analysis of a sequence of Hubble images indicate the object lies in between a redshift of 6.6 and 7.1, making it the most distant source currently known. However, long exposures in the optical and infrared taken with spectrographs on the 10-meter Keck telescopes suggest that the object has a redshift towards the upper end of this range, around redshift 7.

Redshift is a measure of how much the wavelengths of light are shifted to longer wavelengths. The greater the shift in wavelength toward the redder regions of the spectrum, the more distant the object is.

“The galaxy we have discovered is extremely faint, and verifying its distance has been an extraordinarily challenging adventure,” said Dr. Kneib. “Without the magnification of 25 afforded by the foreground cluster, this early object could simply not have been identified or studied in any detail at all with the present telescopes available. Even with aid of the cosmic lens, the discovery has only been possible by pushing our current observatories to the limits of their capabilities!”

Using the combination of the high resolution of Hubble and the large magnification of the cosmic lens, the astronomers estimate that this object, although very small ? only 2,000 light-years across ? is forming stars extremely actively. However, two intriguing properties of the new source are the apparent lack of the typically bright hydrogen emission line and its intense ultraviolet light which is much stronger than that seen in star-forming galaxies closer by.

“The properties of this distant source are very exciting because, if verified by further study, they could represent the hallmark of a truly young stellar system that ended the Dark Ages,” added Dr. Richard Ellis, Steele Professor of Astronomy at Caltech, and a co-author in the article.

The team is encouraged by the success of their technique and plans to continue the search for more examples by looking through other cosmic lenses in the sky. Hubble’s exceptional resolution makes it ideally suited for such searches.

“Estimating the abundance and characteristic properties of sources at early times is particularly important in understanding how the universe reionized itself, thus ending the Dark Ages,” said Mike Santos, a former Caltech graduate student, now a postdoctoral researcher at the Institute of Astronomy, Cambridge, UK. “The cosmic lens has given us a first glimpse into this important epoch. We are now eager to learn more by finding further examples, although it will no doubt be challenging.”

“We are looking at the first evidence of our ancestors on the evolutionary tree of the entire universe,” said Dr. Frederic Chaffee, director of the W. M. Keck Observatory, home to the twin 10-meter Keck telescopes that confirmed the discovery. “Telescopes are virtual time machines, allowing our astronomers to look back to the early history of the cosmos, and these marvelous observations are of the earliest time yet.”

The Caltech team reporting on the discovery consists of Drs. Jean-Paul Kneib, Richard S. Ellis, Michael R. Santos and Johan Richard. Drs. Kneib and Richard also serve the Observatoire Midi-Pyrenees of Toulouse, France. Dr. Santos also represents the Institute of Astronomy, Cambridge, UK.

Public funding for this project was provided in part by NASA GSRP grant NGT5-50339 and NASA STScI grant HST-GO-09452.01-A.

The W. M. Keck Observatory is managed by the California Association for Research in Astronomy (CARA), a scientific partnership among the California Institute of Technology (Caltech), the University of California, and the National Aeronautics and Space Administration (NASA). The Space Telescope Science Institute (STScI) is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), for NASA, under contract with the Goddard Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA).

Original Source: Hubble News Release

Image credit: SDSS
The most distant known quasars show that some supermassive black holes formed when the universe was merely 6 percent of its current age, or about 700 million years after the big bang.

How black holes of several billion solar masses formed so rapidly in the very early universe is one mystery raised by astronomers with the Sloan Digital Sky Survey (SDSS). They have discovered 13 of the oldest, most distant quasars yet found.

“We hope to at least double that number in the next three years,” said Xiaohui Fan of the University of Arizona?s Steward Observatory in Tucson.

Fan led the SDSS team that discovered the distant quasars, which are compact but luminous objects thought to be powered by supermassive black holes. The most distant quasar, in the constellation Ursa Major, is roughly 13 billion light years away.

The most ancient quasars raise other tantalizing questions about the early universe. Fan talked about it today (Feb. 13) at the American Association for the Advancement of Science annual meeting in Seattle.

The infant universe was hydrogen and helium.

“But we see a lot of other elements around those early quasars,” Fan said. “We see evidence of carbon, nitrogen, iron and other elements, and it?s not clear how these elements got there. There is as much iron, proportionate to the population of those early systems, as there is in mature galaxies nearby.”

Astronomers estimate the current age of the universe at 13.7 billion years. Quasars in the early universe looked as mature as nearby galaxies that, like the Milky Way, formed a couple of billion years after the big bang.

Also, radio astronomers collaborating with SDSS researchers detected carbon monoxide, a key component of molecular clouds, near the ancient quasars.

All this evidence suggests that the first mature galaxies formed right along with the ancient supermassive black holes in the very early universe.

Although cosmologists aren?t panicked, they need to refine theory to clarify what?s going on.

Fan and his colleagues believe the oldest quasars can be used to probe the end of the Cosmic Dark Ages and the beginning of the Cosmic Renaissance.

In so-called Cosmic Dark Ages, the universe was a cold, opaque place without stars. Then came a critical phase where the universe went through a rapid transition. The first galaxies and quasars formed in the Cosmic Renaissance, heating the universe so it became the place we see today.

Fan and his colleagues believe some of their oldest known quasars may span the critical transition.

“Our observations suggest that what we may be seeing during this transition is atomic hydrogen becoming completely ionized. This ionization process was one of the important processes going on during the first one billion years.”

Current observations have just begun to reveal when and how this ionization process occurred. Data from distant quasars combined with other evidence, such as from the cosmic microwave background, which is relict radiation from the big bang, will begin to test theory of how the first galaxies appeared in the universe, Fan said.

It may take the large-aperture space telescope, NASA’s 6.5-meter James Webb Space Telescope, to really explore what happened between the Cosmic Dark Ages and the Cosmic Renaissance, Fan said.

Optical/infrared ground-based telescopes cannot detect objects red-shifted much beyond 6.5, Fan noted. Water vapor in Earth?s atmosphere absorbs longer infrared wavelengths, so it will take a space-based telescope, probably with an aperture larger than that of the NASA Spitzer Telescope now orbiting Earth, to study objects at redshift 7, 8, or 10 in detail, Fan said.

(So-called redshift is a phenomenon proportional to the velocity of a a celestial object speeding away from Earth. The lines in its spectrum shift toward longer, red wavelengths. Astronomers now believe that the most distant objects recede from Earth at the highest velocities, so the farther away an object is, the greater its redishift.)

Original Source: UA News Release

Image credit: CfA
When choosing a Valentine’s Day gift for a wife or girlfriend, you can’t go wrong with diamonds. If you really want to impress your favorite lady this Valentine’s Day, get her the galaxy’s largest diamond. But you’d better carry a deep wallet, because this 10 billion trillion trillion carat monster has a cost that’s literally astronomical!

“You would need a jeweler’s loupe the size of the Sun to grade this diamond!” says astronomer Travis Metcalfe (Harvard-Smithsonian Center for Astrophysics), who leads a team of researchers that discovered the giant gem. “Bill Gates and Donald Trump together couldn’t begin to afford it.”

When asked to estimate the value of the cosmic jewel, Ronald Winston, CEO of Harry Winston Inc., indicated that such a large diamond probably would depress the value of the market, stating, “Who knows? It may be a self-deflating prophecy because there is so much of it.” He added, “It is definitely too big to wear!”

The newly discovered cosmic diamond is a chunk of crystallized carbon 50 light-years from the Earth in the constellation Centaurus. (A light-year is the distance light travels in a year, or about 6 trillion miles.) It is 2,500 miles across and weighs 5 million trillion trillion pounds, which translates to approximately 10 billion trillion trillion carats, or a one followed by 34 zeros.

“It’s the mother of all diamonds!” says Metcalfe. “Some people refer to it as ‘Lucy’ in a tribute to the Beatles song ‘Lucy In The Sky With Diamonds.'”

The diamond star completely outclasses the largest diamond on Earth, the 530-carat Star of Africa which resides in the Crown Jewels of England. The Star of Africa was cut from the largest diamond ever found on Earth, a 3,100-carat gem.

The huge cosmic gem (technically known as BPM 37093) is actually a crystallized white dwarf. A white dwarf is the hot core of a star, left over after the star uses up its nuclear fuel and dies. It is made mostly of carbon and is coated by a thin layer of hydrogen and helium gases.

For more than four decades, astronomers have thought that the interiors of white dwarfs crystallized, but obtaining direct evidence became possible only recently.

“The hunt for the crystal core of this white dwarf has been like the search for the Lost Dutchman’s Mine. It was thought to exist for decades, but only now has it been located,” says co-author Michael Montgomery (University of Cambridge).

The white dwarf studied by Metcalfe, Montgomery, and Antonio Kanaan (UFSC Brazil), is not only radiant but also harmonious. It rings like a gigantic gong, undergoing constant pulsations.

“By measuring those pulsations, we were able to study the hidden interior of the white dwarf, just like seismograph measurements of earthquakes allow geologists to study the interior of the Earth. We figured out that the carbon interior of this white dwarf has solidified to form the galaxy’s largest diamond,” says Metcalfe.

Our Sun will become a white dwarf when it dies 5 billion years from now. Some two billion years after that, the Sun’s ember core will crystallize as well, leaving a giant diamond in the center of our solar system.

“Our Sun will become a diamond that truly is forever,” says Metcalfe.

A paper announcing this discovery has been submitted to The Astrophysical Journal Letters for publication.

Original Source: CfA News Release

Image credit: Hubble
Many examples are known where a galaxy acts as a gravitational lens, producing multiple images on the sky of a more distant object like a bright quasar hidden behind it. But there has been a persistent mystery for over 20 years: Einstein’s general theory of relativity predicts there should be an odd number of images, yet almost all observed lenses have only 2 or 4 known images. Now, astronomer Joshua Winn of the Harvard-Smithsonian Center for Astrophysics (CfA) and two former CfA colleagues, David Rusin (now at the University of Pennsylvania) and Christopher Kochanek (The Ohio State University), have identified a third, central image of a lensed quasar. Radio observations of the system known as PMN J1632-0033 in the constellation Ophiuchus uncovered a faint central image, which can be used to investigate the properties of the lensing galaxy and the supermassive black hole expected to lie at its center.

“Finding this central image is interesting in its own right, but is even more important for what it can tell us about the lensing galaxy. This offers us a new tool for studying galaxies so far away that, even to the Hubble Space Telescope, they’re just faint smudges,” said Winn.

Quasars are extremely distant and bright objects believed to be powered by supermassive black holes. They shine brightly by converting the gravitational energy of matter falling into the black hole into light and other types of radiation, such as radio waves.

In gravitational lensing, light rays from a quasar which pass close to a galaxy are bent by the galaxy’s gravitational field, much as they would be bent when passing through a glass lens. The denser the center of a galaxy, and the stronger its gravity, the fainter the central image will be. Yet this central image, whose light has passed closest to the middle of the lensing galaxy, can tell us much about that galaxy’s core. That opportunity makes finding such central images particularly desirable.

In the system PMN J1632-0033, a radio-loud quasar at redshift z=3.42 (a distance of about 11.5 billion light-years) is being lensed by an elliptical galaxy at redshift z~1 (about 8 billion light-years away). Two images of the quasar were known to exist, and a third, very faint radio source was suspected to be the central image. However, that third source was right on top of the lensing galaxy, and so might have been intrinsic to the lensing galaxy itself.

By observing the radio “color,” or spectrum, of all three images using the National Science Foundation’s Very Large Array and Very Long Baseline Array, Winn and his colleagues provided compelling evidence that the third source is indeed the quasar’s central image. Its spectrum is essentially identical to the other two images, except at low frequencies where some of the radio energy was absorbed by the lensing galaxy.

The geometry and properties of the quasar’s three images already are telling us about the core of the lensing galaxy. For example, its central black hole weighs less than 200 million solar masses. Also, its surface density (amount of matter as projected against the plane of the sky) at the location of the central image is more than 20,000 solar masses per square parsec. (For comparison, the surface density of the Milky Way near our sun is about 50 solar masses per square parsec.) Both figures for the lensing galaxy agree with expectations based on detailed observations of galaxies hundreds of times closer to the Earth.

“Almost all of our knowledge about galaxy centers comes from studying very nearby galaxies. The remarkable thing about central images is that you can get similar information about the cores of galaxies hundreds of times farther away, and billions of years younger than our neighboring galaxies,” said Winn.

This research is available online at http://arxiv.org/abs/astro-ph/0312136 and will be published in the February 12, 2004 issue of the journal Nature.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: Harvard CfA News Release