all Harvard College Observatory (HCO) stories

Astronomers nab culprit in galactic hit-and-run

70652986 — Mon, 26 Mar 2007 05:46:46 -0400

The Andromeda galaxy, the closest large spiral to the Milky Way, appears calm and tranquil as it wheels through space. But appearances can be deceiving. Astronomers have new evidence that Andromeda was involved in a violent head-on collision with the neighboring dwarf galaxy Messier 32 (M32) more than 200 million years ago.

"Like a CSI team, we gathered clues and reconstructed the scene of the crime," said Pauline Barmby (Harvard-Smithsonian Center for Astrophysics), a member of the research group that made the discovery. "The evidence clearly shows that M32 is guilty of committing a hit-and-run."

This discovery was reported in the Oct. 19, 2006, issue of the journal Nature.

Dramatic proof of the galactic smash-up came from images taken by the Infrared Array Camera (IRAC) on NASA's Spitzer Space Telescope. Those images revealed a never-before-seen dust ring deep within the Andromeda galaxy. When combined with a previously observed outer ring, the presence of both dust rings suggests a long-ago disturbance whose effects are still expanding outward through Andromeda.

Strange new planet baffles astronomers

70652986 — Mon, 26 Mar 2007 06:28:15 -0400

Using a network of small automated telescopes known as HAT, Smithsonian astronomers have discovered a planet unlike any other known world. This new planet, designated HAT-P-1, orbits one member of a pair of distant stars 450 light-years away in the constellation Lacerta.

"We could be looking at an entirely new class of planets," said Gaspar Bakos, a Hubble fellow at the Harvard-Smithsonian Center for Astrophysics (CfA). Bakos designed and built the HAT network and is lead author of a paper submitted to the Astrophysical Journal describing the discovery. That paper is available online at http://arxiv.org/abs/astro-ph/0609369.

With a radius about 1.38 times Jupiter's, HAT-P-1 is the largest known planet. In spite of its huge size, its mass is only half that of Jupiter.

"This planet is about one-quarter the density of water," Bakos said. "In other words, it's lighter than a giant ball of cork! Just like Saturn, it would float in a bathtub if you could find a tub big enough to hold it, but it would float almost three times higher."

HAT-P-1 revolves around its host star every 4.5 days in an orbit one-twentieth of the distance from Earth to the Sun. Once each orbit, it passes in front of its parent star, causing the star to appear fainter by about 1.5 percent for more than two hours, after which the star returns to its previous brightness.

HAT-P-1's parent star is one member of a double-star system called ADS 16402 and is visible in binoculars. The two stars are separated by about 1500 times the Earth-Sun distance. The stars are similar to the Sun but slightly younger - about 3.6 billion years old compared to the Sun's age of 4.5 billion years.

Major funding for HATnet was provided by NASA.

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.

'Wintering-over' at the South Pole

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

They came to the South Pole, enduring months of bitter cold, darkness, and isolation, to peer at the galaxy's center through clear, dry skies. And in December, they - scientists from the Harvard-Smithsonian Center for Astrophysics (CfA) - declared "mission accomplished."

After 11 years, the Antarctic Submillimeter Telescope and Remote Observatory, AST/RO, was dismantled last fall. The 1.7- meter telescope was boxed up for transport and now sits on the snow, awaiting a decision on its next stop.

Super-Earths may be three times more common than Jupiters

70652986 — Mon, 26 Mar 2007 06:25:36 -0400

Astronomers have discovered a new "super-Earth" orbiting a red dwarf star located about 9,000 light-years away. This newfound world weighs about 13 times the mass of the Earth and is probably a mixture of rock and ice, with a diameter several times that of Earth. It orbits its star at about the distance of the asteroid belt in our solar system, 250 million miles out. Its distant location chills it to -330 degrees Fahrenheit, suggesting that although this world is similar in structure to the Earth, it is too cold for liquid water or life.

Orbiting almost as far out as Jupiter does in our solar system, this "super-Earth" likely never accumulated enough gas to grow to giant proportions. Instead, the disk of material from which it formed dissipated, starving it of the raw materials it needed to thrive.

"This is a solar system that ran out of gas," says Harvard astronomer Scott Gaudi of the Harvard-Smithsonian Center for Astrophysics (CfA), a member of the MicroFUN collaboration that spotted the planet.

The discovery was reported March 13, 2006 in a paper posted online at http://arxiv.org/abs/astro-ph/0603276 and submitted to The Astrophysical Journal Letters for publication.

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.

There's more to the North Star than meets the eye

70652986 — Mon, 26 Mar 2007 06:24:03 -0400

We tend to think of the North Star, Polaris, as a steady, solitary point of light that guided sailors in ages past. But there is more to the North Star than meets the eye - two faint stellar companions. The North Star is actually a triple star system. And while one companion can be seen easily through small telescopes, the other hugs Polaris so tightly that it has never been seen directly - until now.

By stretching the capabilities of NASA's Hubble Space Telescope to the limit, astronomers have photographed the close companion of Polaris for the first time. They presented their findings Jan. 9, 2006 in a press conference at the 207th meeting of the American Astronomical Society in Washington, D.C.

"The star we observed is so close to Polaris that we needed every available bit of Hubble's resolution to see it," said Smithsonian astronomer Nancy Evans (Harvard-Smithsonian Center for Astrophysics).

The companion proved to be less than two-tenths of an arcsecond from Polaris - an incredibly tiny angle equivalent to the apparent diameter of a quarter located 19 miles away. At the system's distance of 430 light-years, that translates into a physical separation of about 2 billion miles.

"The brightness difference between the two stars made it even more difficult to resolve them," stated Howard Bond of the Space Telescope Science Institute (STScI). Polaris is a supergiant more than two thousand times brighter than the Sun, while its companion is a main-sequence star. "With Hubble, we've pulled the North Star's companion out of the shadows and into the spotlight."

By watching the motion of the companion star, Evans and her colleagues expect to learn not only the stars' orbits but also their masses. Measuring the mass of a star is one of the most difficult tasks facing stellar astronomers.

A star that looks like a planet

70652986 — Mon, 26 Mar 2007 05:42:39 -0400

Astronomers using NASA's Spitzer Space Telescope have discovered a remarkably small brown dwarf surrounded by a dusty disk. The brown dwarf contains only about eight times the mass of Jupiter, making it one of the smallest known brown dwarfs.

A harvest of dozens of new stars

70652986 — Mon, 26 Mar 2007 05:42:16 -0400

A new infrared image of the reflection nebula NGC 1333, located about 1,000 light-years from Earth in the constellation Perseus, reveals dozens of stars like the Sun but much younger.

"These newborns are less than a million years old - babies by astronomical standards," said Rob Gutermuth of the Harvard- Smithsonian Center for Astrophysics (CfA). "Our Sun may have formed in a similar environment 4.5 billion years ago."

Most of the visible light from the region's young stars is obscured by the dusty cloud in which they formed.

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.

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.

Amateur and professional astronomers team to find new planet

70652986 — Mon, 26 Mar 2007 06:18:20 -0400

Astronomer Scott Gaudi of the Harvard-Smithsonian Center for Astrophysics believes that microlensing has the potential for wide use in the future: "With improving technologies and techniques, the first Earth-sized planet may be found by microlensing."

Last year marked the first discovery made using microlensing. This second find establishes the immediate usefulness of the technique in the ongoing search for new worlds.

The most recently discovered planet weighs approximately three times more than Jupiter and most likely orbits a star similar to the sun. When it was discovered, the planet was located about three times as far away from its host star as the Earth is from the Sun.

Both the planet and its star are located approximately 15,000 light-years from the Earth. The new planet and its star compose one of the most distant worlds ever found by man. Gravitational microlensing offers unique advantages for astronomers hunting planets: not only can it find more distant worlds than previously used techniques, but microlensing also is more sensitive to smaller worlds.

The microlensing event was detected and observed by the Optical Gravitational Lensing Experiment, or OGLE, led by Andrzej Udalski of Warsaw University. Two other collaborations - the Probing Lensing Anomalies NETwork (PLANET) and Microlensing Observations in Astrophysics (MOA) - also followed the event and contributed to the journal paper.

Case of Sedna's 'missing moon' solved

70652986 — Mon, 26 Mar 2007 06:17:51 -0400

In trying to solve the riddle of Sedna's "missing moon," scientists Scott Gaudi, Krzysztof (Kris) Stanek and colleagues at the Harvard-Smithsonian Center for Astrophysics took measurements that have cleared up the mystery by showing that a moon wasn't needed after all. Sedna is rotating much more rapidly than originally believed, spinning once on its axis every 10 hours. This shorter rotation period is typical of planetoids in our solar system, requiring no external influences to explain.

"We've solved the case of Sedna's missing moon. The moon didn't vanish because it was never there to begin with," said Gaudi.

The research was submitted to The Astrophysical Journal Letters for publication and is posted online at http://arxiv.org/abs/astro-ph/0503673.

While these data solve one mystery of Sedna, other mysteries remain. Chief among them is the question of how Sedna arrived in its highly elliptical, eons-long orbit.