all cosmology stories

Harvard astronomers share dark prize

50443248 — Tue, 02 Oct 2007 10:02:27 -0400

Two teams who upset everyone's ideas about how the universe works and its future will share the $500,000 Gruber Cosmology Prize for discovering that 70 percent of the universe is nothing but a strange form of energy.

In 1998, a group called the High-z Supernova Search Team published irresistible evidence that the universe is expanding at a rate that may never slow down. Eleven of the 19 members of the High-z team are or were affiliated with Harvard University. Months later, a second team, the Supernova Cosmology Project, independently confirmed the startling finding. That team was lead by Saul Perlmutter of the University of California, Berkeley.

Cosmic blast announces a future supernova

Thu, 12 Jul 2007 16:07:54 -0400

It's one thing to theorize about an exploding star the size of our sun, it's another to look up in the sky and watch one getting ready to blow.

Astronomers are now doing this.

On Feb. 12, a star known as RS Ophiuchi, some 8,000 trillion miles away, erupted in an explosion so bright it could be seen on Earth without a telescope. It was the star's sixth attention-getting blowout since 1898.

Using satellites and ground-based telescopes, observers from the Harvard-Smithsonian Center for Astrophysics (CfA) and their colleagues from other institutions caught the eruption near its maximum brightness. They measured high-energy X-rays, low-energy radio waves, and heat coming from the outburst.

Jupiter's 'big brother' has moon-forming dust disk

70652986 — Mon, 26 Mar 2007 06:27:45 -0400

Earth's moon was created by an early collision with another large planetary body. It was a "chip off the old block." Mars captured its asteroidal moons as they passed by. But Jupiter made its own moons out of dust and gas remaining from its formation. Now, observations by astronomer Subhanjoy Mohanty of the Harvard- Smithsonian Center for Astrophysics and his colleagues provide the first direct evidence for a dusty disk around a distant planet that in mass would be Jupiter's "big brother."

"It is quite possible that moons or moonlets could form out of this disk, just as they have around the giant planets in our own solar system," said Mohanty.

Mohanty presented the discovery June 5, 2006, in a press conference at the 208th meeting of the American Astronomical Society. Other members of the team are Ray Jayawardhana (University of Toronto), Nuria Huélamo (ESO) and Eric Mamajek (CfA).

The team studied a planetary mass object known as 2MASS1207-3932B, which is located about 170 light-years from Earth in the direction of the constellation Centaurus. 2M1207B, as it is abbreviated, orbits a tiny brown dwarf star at a separation of about 40 astronomical units, or 3.7 billion miles - comparable to the size of Pluto's orbit. That separation is much larger than typical for binary brown dwarf systems. The wide separation may indicate that the duo formed in relative isolation, far from passing stars that could have pulled them apart.

Two exiled stars are leaving our galaxy forever

70652986 — Mon, 26 Mar 2007 06:24:35 -0400

TV reality show contestants aren't the only ones under threat of exile. Astronomers using the MMT Observatory in Arizona have discovered two stars exiled from the Milky Way galaxy. Those stars are racing out of the Galaxy at speeds of more than 1 million miles per hour - so fast that they will never return.

"These stars literally are castaways," said Smithsonian astronomer Warren Brown (Harvard-Smithsonian Center for Astrophysics). "They have been thrown out of their home galaxy and set adrift in an ocean of intergalactic space."

Brown and his colleagues spotted the first stellar exile in 2005. European groups identified two more, one of which may have originated in a neighboring galaxy known as the Large Magellanic Cloud. The latest discovery brings the total number of known exiles to five.

"These stars form a new class of astronomical objects - exiled stars leaving the Galaxy," said Brown.

Astronomers suspect that about 1,000 exile stars exist within the Galaxy. By comparison, the Milky Way contains about 100,000,000,000 (100 billion) stars, making the search for exiles much more difficult than finding the proverbial "needle in a haystack." The Smithsonian team improved their odds by preselecting stars with locations and characteristics typical of known exiles. They sifted through dozens of candidates spread over an area of sky almost 8,000 times larger than the full moon to spot their quarry.

"Discovering these two new exiled stars was neither lucky nor random," said astronomer Margaret Geller (Smithsonian Astrophysical Observatory), a co-author on the paper. "We made a targeted search for them. By understanding their origin, we knew where to find them."

This research has been submitted to The Astrophysical Journal Letters for publication and is available online at http://arxiv.org/ abs/astro-ph/0601580. Authors on the paper are Brown, Geller, Scott Kenyon and Michael Kurtz (Smithsonian Astrophysical Observatory).

Cosmic jet looks like giant tornado in space

70652986 — Mon, 26 Mar 2007 06:23:49 -0400

While examining a region where new stars are forming with NASA's Spitzer Space Telescope, astronomers found a surprise - an object that looks like a giant tornado in space. The apparent tornado is shaped by a cosmic jet packing a powerful punch as it plows through clouds of interstellar gas and dust. They released an image of the "tornado" Jan. 12, 2006, at the 207th meeting of the American Astronomical Society in Washington, D.C.

"When I first saw the image of this tornado-like object, I was amazed," said Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics (CfA). "In the thousands of Spitzer images we've looked at, we've never seen anything like this before."

The "tornado" is actually a shock front created by a jet of material flowing downward through the field of view. A still- forming star located off the upper edge of the image generates this outflow. The jet slams into neighboring dust clouds at a speed of more than 100 miles per second, heating the dust to incandescence and causing it to glow with infrared light detectable by Spitzer. The triangular shape results from the wake created by the jet's motion, similar to the wake behind a speeding boat.

The outflow that powers the "tornado," designated Herbig-Haro 49/50, had been observed before, most recently using a ground-based telescope at the Cerro Tololo Inter-American Observatory. Intrigued by the shock emission spotted at Cerro Tololo, astronomers then targeted Spitzer onto the region and were thrilled to see a spectacular spiral structure emerge.

"The helical morphology of the `tornado' makes it unique," said astronomer John Bally (University of Colorado), lead author on the research.

The scientists could only speculate about the source of the spiral appearance. Magnetic fields throughout the region might have shaped the object. Alternatively, the shock might have developed instabilities as it plowed into surrounding material, creating eddies that give the "tornado" its distinctive appearance.

Space telescope captures cosmic 'Mountains of Creation'

70652986 — Mon, 26 Mar 2007 06:23:04 -0400

Captured by the Spitzer Space Telescope's infrared eyes, a new majestic image resembles the iconic "Pillars of Creation" picture taken of the Eagle Nebula in visible light by NASA's Hubble Space Telescope in 1995. Both views feature star-forming clouds of cool gas and dust that have been sculpted into pillars by radiation and winds from hot, massive stars.

The Spitzer image shows the eastern edge of a region known as W5, near the Perseus constellation 7,000 light-years away. This region is dominated by a single massive star, whose location outside the pictured area is "pointed out" by the finger-like pillars. The pillars themselves are colossal, together resembling a mountain range. For comparison, the pillars in the Eagle Nebula are less than one-tenth their size.

The largest of the pillars seen by Spitzer entombs hundreds of never-before-seen embryonic stars, and the second largest contains dozens.

"We believe that the star clusters lighting up the tips of the pillars are essentially the offspring of the region's single, massive star," said Lori Allen, lead investigator of the new observations from the Harvard-Smithsonian Center for Astrophysics (CfA). "It appears that radiation and winds from the massive star triggered new stars to form."

Spitzer was able to see the stars forming inside the pillars thanks to its infrared vision. Visible-light images of this same region show dark towers outlined by halos of light. The stars inside are cloaked by walls of dust. But infrared light coming from these stars can escape through the dust, providing astronomers with a new view.

Cosmic cloudshine

70652986 — Mon, 26 Mar 2007 06:22:47 -0400

Hubble's iconic images include many shots of cosmic clouds of gas and dust called nebulae. For example, the famous "Pillars of Creation" mark the birthplace of new stars within the Eagle Nebula. Yet despite their beauty, visible-light images show only the nebulae surfaces. Baby stars may hide beneath, invisible even to Hubble's powerful gaze.

Harvard astronomers have pioneered a new way to peer below the surface using near-infrared light that is invisible to the human eye. The resulting images are both beautiful and scientifically valuable because they can be used to map the structure of interstellar matter.

"We can now see the structure of gigantic star-forming regions over vast distances with a resolution 50 times better than before," said Alyssa Goodman of the Harvard-Smithsonian Center for Astrophysics (CfA). "This technique will revolutionize the way we map stellar birthplaces."

While Hubble's NICMOS instrument and NASA's Spitzer Space Telescope also use infrared light to study nebular interiors, ground-based images at near-infrared wavelengths provide an unparalleled combination of wide-field coverage and high resolution.

"Images like these will give astronomers new insight into what those giant complexes of gas and dust really look like," added Jonathan Foster, a graduate student at Harvard University and the paper's first author.

The researchers took long-exposure photographs of a star- forming region in the constellation Perseus and were surprised to see something they had never seen before. Just as earthly clouds shine orange at night as they reflect light from streetlights below, they discovered that clouds in outer space show a similar effect. In space, otherwise "dark" clouds of dust and gas are illuminated by faint starlight washing over them.

Goodman and Foster dubbed the new celestial phenomenon "cloudshine." Their long-exposure, near-infrared images uncovered the faintly shining billows of material. Recent advances in infrared detectors, combined with longer than usual imaging times, led to the discovery.

It takes three Smithsonian observatories to decipher one mystery object

70652986 — Mon, 26 Mar 2007 06:22:33 -0400

In an exercise that demonstrates the power of a multiwavelength investigation using diverse facilities, astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) have deciphered the true nature of a mysterious object hiding inside a dark cosmic cloud. They found that the cloud, once thought to be featureless, contains a baby star, or possibly a failed star known as a "brown dwarf," that is still forming within its dusty cocoon.

Observations indicate that the mystery object has a mass about 25 times that of Jupiter, which would place it squarely in the realm of brown dwarfs. However, its mass may eventually grow large enough to qualify it as a small star. The object also is cool and faint, shining with less than 1/20 the sun's luminosity.

"This object is the runt of the star formation family," said CfA astronomer Tyler Bourke.

Establishing the true nature of the object required the unique capabilities of the Submillimeter Array (SMA) in Hawaii. "The SMA spotted what no single-dish telescope could see," said Bourke.

Using the SMA, scientists detected a weak outflow of material predicted by star formation theories. That outflow - 10 times smaller in mass than any seen before - confirmed both the low- mass nature of the object and its association with the surrounding dark cloud. "The sensitivity and resolution of the Submillimeter Array with its multiple antennas were crucial in detecting the outflow," said Bourke.

The puzzling object was discovered using a Smithsonian- developed infrared camera on board NASA's Spitzer Space Telescope. Spitzer studied the dusty cosmic cloud named L1014 as part of the Cores to Disks Legacy program. A core is the densest region of a cloud, massive enough to make a star like the sun.

Black holes aren't so black

70652986 — Mon, 26 Mar 2007 06:22:14 -0400

As gas is pulled into a black hole by its strong gravitational force, the gas heats up and radiates. That radiation can be used to illuminate the black hole and paint its profile.

Within a few years, astronomers believe they will be able to peer close to the horizon of the black hole at the center of the Milky Way. Already, they have spotted light from "hot spots" just outside the black hole. While current technology is not quite ready for the final plunge, Harvard theorists Avery Broderick and Avi Loeb already have modeled what observers will see when they look into the maw of this monster.

"It will be really remarkable when observers can see all the way to the edge of the Milky Way's central black hole - a hole 10 million miles in diameter that's more than 25,000 light-years away," said Broderick.

All it will take is a cross-continental array of submillimeter telescopes to effectively create a single telescope as large as the Earth. This process, known as interferometry, has already been used to study longer wavelength radio emissions from outer space. By studying shorter wavelength submillimeter emissions, astronomers could get a high-resolution view of the region just outside the black hole.

Ferreting out the first stars

70652986 — Mon, 26 Mar 2007 06:22:35 -0400

The first stars are so distant and formed so long ago that they are invisible to our best telescopes.

Until they explode. Hypernovas (more powerful cousins of supernovas) and their associated gamma-ray bursts offer astronomers the possibility of detecting light from the first generations of stars.

NASA's Swift satellite already has seen a gamma-ray burst (GRB) with a redshift of 6.29, meaning that the progenitor star exploded about 13 billion years ago, when the universe was less than a billion years old. Theorists Volker Bromm (University of Texas at Austin) and Avi Loeb (Harvard-Smithsonian Center for Astrophysics) predict that one-tenth of the blasts Swift will spot during its operational lifetime will come from stars at a redshift of 5 or greater, that lived and died during the first billion years of the universe.

"Most of those GRBs will come from second generation or later stars," said Loeb. "But if we get lucky, Swift may even detect a burst from one of the very first stars that formed -- a star made of only hydrogen and helium."

Calculations suggest that such stars, which are called Population III for historical reasons, would have been behemoths weighing 50-500 times as much as the Sun. A Population III star would have gulped its nuclear fuel faster than an SUV, dying quickly and explosively.

"Our best guess right now is that the recent GRB was not from a Pop III star. However, its redshift is high enough to make it very interesting," said Bromm.

First baby photo of stellar twins

70652986 — Mon, 26 Mar 2007 06:22:38 -0400

Newborn stars are difficult to photograph. They tend to hide in the nebulous stellar nurseries where they formed, enshrouded by thick layers of dust. Now, Smithsonian astronomer T.K. Sridharan (Harvard-Smithsonian Center for Astrophysics) and his colleagues have photographed a pair of stellar twins in infrared light, which penetrates the dust. And these babies are whoppers, weighing several times the mass of the Sun.

Moreover, Sridharan's images reveal a circumstellar disk surrounding the more massive of the two stars. The presence of a disk suggests that massive, multiple-star systems form the same way as the Sun, by gradually accreting material from a gaseous disk.

"This system is the youngest massive binary ever to be directly imaged - only about 100,000 years old," said Sridharan.

Fastest pulsar speeding out of galaxy

70652986 — Mon, 26 Mar 2007 06:22:40 -0400

A speeding, superdense neutron star somehow got a powerful "kick" that is propelling it completely out of our Milky Way Galaxy into the cold vastness of intergalactic space. Its discovery is puzzling astronomers who used the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope to directly measure the fastest speed yet found in a neutron star.

The neutron star is the remnant of a massive star born in the constellation Cygnus that exploded about two and a half million years ago in a titanic explosion known as a supernova. Ultra- precise VLBA measurements of its distance and motion show that it is on course to inevitably leave our galaxy.

"We know that supernova explosions can give a kick to the resulting neutron star, but the tremendous speed of this object pushes the limits of our current understanding," said Shami Chatterjee, of the National Radio Astronomy Observatory (NRAO) and the Harvard-Smithsonian Center for Astrophysics. "This discovery is very difficult for the latest models of supernova core collapse to explain," he added.

Chatterjee and his colleagues used the VLBA to study the pulsar B1508+55, about 7,700 light-years from Earth. With the ultrasharp radio "vision" of the continent-wide VLBA, they were able to precisely measure both the distance and the speed of the pulsar, a spinning neutron star emitting powerful beams of radio waves. Plotting its motion backward pointed to a birthplace among groups of giant stars in the constellation Cygnus -- stars so massive that they inevitably explode as supernovae.

"This is the first direct measurement of a neutron star's speed that exceeds 1,000 kilometers per second," said Walter Brisken, an NRAO astronomer. "Most earlier estimates of neutron-star speeds depended on educated guesses about their distances. With this one, we have a precise, direct measurement of the distance, so we can measure the speed directly," Brisken said. The VLBA measurements show the pulsar moving at nearly 1,100 kilometers (more than 670 miles) per second -- about 150 times faster than an orbiting Space Shuttle. At this speed, it could travel from London to New York in five seconds.

How to build a big star

70652986 — Mon, 26 Mar 2007 06:22:43 -0400

The most massive stars in our galaxy weigh as much as 100 small stars like the Sun. How do such monsters form? Do they grow rapidly by swallowing smaller protostars within crowded star-forming regions? Some astronomers thought so, but a new discovery suggests instead that massive stars develop through the gravitational collapse of a dense core in an interstellar gas cloud via processes similar to the formation of low mass stars.

"In the past, theorists have had trouble modeling the formation of high-mass stars and there has been an ongoing debate between the merger versus the accretion scenarios." said astronomer Nimesh Patel of the Harvard-Smithsonian Center for Astrophysics (CfA). "We've found a clear example of an accretion disk around a high-mass protostar, which supports the latter while providing important observational constraints to the theoretical models."

Patel and his colleagues studied a young protostar 15 times more massive than the Sun, located more than 2,000 light-years away in the constellation Cepheus. They discovered a flattened disk of material orbiting the protostar. The disk contains 1 to 8 times as much gas as the Sun and extends outward for more than 30 billion miles - eight times farther than Pluto's orbit.

The existence of this disk provides clear evidence of gravitational collapse, the same gradual process that built the Sun. A disk forms when a spinning gas cloud contracts, growing denser and more compact. The angular momentum of the spinning material forces it into a disk shape. The planets in our solar system formed from such a disk 4.5 billion years ago.

Robotic telescope penetrates heart of universe's most powerful explosion

70652986 — Mon, 26 Mar 2007 06:18:25 -0400

Cullen Blake, a graduate student at the Harvard-Smithsonian Center for Astrophysics and lead author on the paper, said that the simultaneous observation of infrared light with a gamma-ray burst was unprecedented.

This observation was made possible by PAIRITEL's ability to aim at objects quickly and automatically. PAIRITEL pointed at the burst minutes after the Integral gamma-ray satellite detected it. PAIRITEL's efficiency allowed astronomers to spot infrared light from the explosion during the gamma-ray burst.

Zaldarriaga probes universe's start

50443248 — Tue, 24 Jul 2007 14:32:02 -0400

Matias Zaldarriaga is peering back into time to find his roots - and the roots of everything else ever created.
Zaldarriaga, named professor of astronomy in July, is an expert in cosmology, which is the study of the origins and evolution of the universe.

A theoretical astrophysicist, Zaldarriaga is trying to understand the faint cosmic whispers of the big bang, that split-second explosion of inconceivable violence when all matter was hurled outward on a journey that would form the universe around us - somewhere between 10 billion and 20 billion years ago.

The period from the big bang to about 400,000 years later, when radiation called the "cosmic microwave background" was formed, is the focus of Zaldarriaga's research.