Astronomers witness mysterious and unique disintegration of asteroid

This series of Hubble Space Telescope images reveals the breakup of an asteroid over a period of several months in late 2013. 

The largest fragments are up to 200 yards in radius, each with "tails" caused by dust lifted from their surfaces and pushed back by the pressure of sunlight. 

The 10 pieces of the asteroid drift apart slowly and show a range of breakup times, suggesting that the disintegration cannot be explained by a collision with another asteroid. 

One idea for the breakup is that the asteroid was accelerated by sunlight to spin at a fast enough rate to fly apart by centrifugal force. 

The images were taken in visible light with Hubble's Wide-Field Camera 3. 

Credit: NASA, ESA, D. Jewitt/UCLA

Astronomers have witnessed for the first time the breakup of an asteroid into as many as 10 smaller pieces.

The discovery is published online March 6 in Astrophysical Journal Letters.

Though fragile comet nuclei have been seen falling apart as they near the sun, nothing resembling this type of breakup has been observed before in the asteroid belt. NASA's Hubble Space Telescope photographed the demolition.

"Seeing this rock fall apart before our eyes is pretty amazing," said David Jewitt, a professor in the UCLA Department of Earth, Planetary and Space Sciences and the UCLA Department of Physics and Astronomy, who led the astronomical forensics investigation.

The crumbling asteroid, designated P/2013 R3, was first noticed as an anomalous, fuzzy-looking object on Sept. 15, 2013, by the Catalina and Pan-STARRS sky-survey telescopes.

Pan-STARRS sky-survey telescope

A follow-up observation on Oct. 1 with the W.M. Keck telescope on Hawaii's Mauna Kea revealed three co-moving bodies embedded in a dusty envelope that is nearly the diameter of Earth.

"The Keck telescope showed us that this asteroid was worth looking at with Hubble," Jewitt said.

With its superior resolution, the Hubble telescope revealed that there were really 10 embedded objects, each with comet-like dust tails.

The four largest rocky fragments are up to 200 yards in radius, about twice the length of a football field.

The Hubble data showed that the fragments are drifting away from each other at a leisurely pace of one mile per hour—slower than a strolling human.

The asteroid began coming apart early last year, but new pieces continue to emerge in the most recent images.

This makes it unlikely that the asteroid is disintegrating because of a collision with another asteroid, which would be instantaneous and violent.

Some of the debris from such a high-velocity smash-up would also be expected to travel much faster than observed.

A black hole shreds a star, and a bright flare is formed - Video

Computer simulation of the disruption of a star by a black hole shows the formation of an "accretion disk" of stellar material spiraling into the black hole. 

This image shows an early stage in the formation of the disk. 

Credit: James Guillochon

Ramirez-Ruiz, a professor of astronomy and astrophysics at the University of California, Santa Cruz, uses computer simulations to explore the universe's most violent events, so when the first detailed observations of a star being ripped apart by a black hole were reported in 2012 (Gezari et al., Nature), he was eager to compare the data with his simulations.

Ramirez-Ruiz

He was also highly skeptical of one of the published conclusions: that the disrupted star was a rare helium star.

"I was sure it was a normal hydrogen star and we were just not understanding what's going on," said Ramirez-Ruiz.

In a paper accepted for publication in the Astrophysical Journal and available online at arXiv.org, Ramirez-Ruiz and his students explain what happens during the disruption of a normal sun-like star by a supermassive black hole, and they show why observers might fail to see evidence of the hydrogen in the star.


First author and UCSC graduate student James Guillochon (now an Einstein Fellow at Harvard University) and undergraduate Haik Manukian worked with Ramirez-Ruiz to run a series of detailed computer simulations of encounters between stars and black holes.

James Guillochon

Supermassive black holes are thought to lurk at the centers of most galaxies. Some (known as active galactic nuclei) are very bright, emitting intense radiation from superheated gas falling into the black hole.

But the central black holes of most galaxies in the local universe have run out of gas and are quiescent.

Only when an unlucky star approaches too close and gets shredded by the black hole's powerful tidal forces does the galactic center emit a bright flare of light.

Astronomers call this a "tidal disruption event" (TDE), and in a typical galaxy it happens about once every 10,000 years.

"That means you have to survey the nearest 10,000 galaxies in order to see one event, so for many years this was very much a theoretical field," Ramirez-Ruiz said.

Then came Pan-STARRS (Panoramic Survey Telescope and Rapid Response System), which is surveying the sky on a continual basis and has begun detecting and recording observations of these very rare events.

The first one, known as PS1-10jh, was detected in 2010 and published in 2012.

Astronomers recorded the light curve (the rise and fall in brightness over time) and took a spectrum at peak brightness to study the different wavelengths of light.

The spectrum of an active galactic nucleus (AGN) shows characteristic "emission lines" at specific wavelengths corresponding to the most common elements such as hydrogen and helium.

These emission lines appear as spikes of increased intensity in a continuous spectrum. The shocking thing about PS1-10jh was the absence of a hydrogen line in the spectrum.

"It's very unusual to have seen helium and not hydrogen. Stars are mainly made of hydrogen, and stars made only of helium are extremely rare, so this was a huge issue," Guillochon said.

"People said maybe it was a giant star with a helium core and a hydrogen envelope, and the black hole removed the hydrogen first and then the helium core in a second pass."

Guillochon began to explore the possibilities using computer simulations. The results provide a new understanding of the origin of the emission lines in a tidal disruption event.

They show that the flare of light from a tidal disruption contains information about the type of star and the size of the black hole, and they show that PS1-10jh involved the most common type of star (a main-sequence star much like our sun) and a relatively small supermassive black hole.

More Information: 'PS1-10jh: The Disruption of a Main-Sequence Star of Near-Solar Composition': James Guillochon, Haik Manukian, Enrico Ramirez-Ruiz (UC Santa Cruz) arXiv:1304.6397 [astro-ph.HE] (or arXiv:1304.6397v2 [astro-ph.HE])

Hubble sees asteroid spouting six comet-like tails

This NASA Hubble Space Telescope set of images reveals a never-before-seen set of six comet-like tails radiating from a body in the asteroid belt, designated P/2013 P5. 

The asteroid was discovered as an unusually fuzzy-looking object with the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) survey telescope in Hawaii. 

The multiple tails were discovered in Hubble images taken on Sept. 10, 2013. 

When Hubble returned to the asteroid on Sept. 23, the asteroid's appearance had totally changed. It looked as if the entire structure had swung around. 

One interpretation is that the asteroid's rotation rate has been increased to the point where dust is falling off the surface and escaping into space where the pressure of sunlight sweeps out fingerlike tails. 

According to this theory, the asteroid's spin has been accelerated by the gentle push of sunlight. The object, estimated to be no more than 1,400 feet across, has ejected dust for at least five months, based on analysis of the tail structure. 

These visible-light, false-color images were taken with Hubble's Wide Field Camera 3. Credit: NASA, ESA, and D. Jewitt (UCLA)

NEO Asteroid Detection: NASA's Arecibo now and ATLAS in the future

Arecibo Radio Telescope

The NEO program at NASA currently detects and tracks Earth-approaching asteroids and comets with land-based and orbiting telescopes. Scientists estimate their mass and orbit to gauge whether they pose a danger.

With this system, the Arecibo radio telescope in Puerto Rico, which has an antenna 305 meters in diameter, can observe with great sensitivity a third of the night sky and detect asteroids that are on the large side.

All asteroid observations made anywhere in the world by telescopes, even by amateur star gazers, must be passed on to the Minor Planet Center, which is financed by NASA and run by the Smithsonian Astrophysical Observatory for the Paris-based International Astronomical Union.

But in times of tight budgets like these, NASA is trying to develop other systems specifically capable of tracking small objects in space.

NASA is financing to the tune of $5 million a project at the University of Hawaii called Atlas, or Asteroid Terrestrial-Impact Alert System.

Researchers say ATLAS, which will monitor the entire visible sky every night, will be able to detect objects 45 meters (yards) in diameter a week before they hit our planet.

For those measuring 150 meters (yards) in diameter, the system -- which could be operational in late 2015 -- will give a three week heads up.

The goal is to find the objects and give enough advance warning for measures to be taken to protect people, said John Tonry, the principal investigator at ATLAS.

The system has enough sensitivity to detect a match flame in New York City when viewed from San Francisco, for instance.

"That's enough time to evacuate the area of people, take measures to protect buildings and other infrastructures and be alert to a tsunami danger generated by ocean impacts," according to the ATLAS website.

ATLAS will complement the Institute for Astronomy’s Pan-STARRS project, a system that searches for large “killer asteroids” years, decades, and even centuries before impact with Earth.

Whereas Pan-STARRS takes a month to complete one sweep of the sky in a deep but narrow survey, ATLAS will search the sky in a closer and wider path to help identify the smaller asteroids that hit Earth more frequently.

Pan-STARRS Discovers Potentially Hazardous Asteroid

The University of Hawaii's Pan-STARRS PS1 telescope on Haleakala has discovered an asteroid that will come within 4 million miles of Earth in mid-October. The object is about 150 feet in diameter and was discovered in images acquired on September 16, when it was about 20 million miles away.

It is the first "potentially hazardous object" (PHO) to be discovered by the Pan-STARRS survey and has been given the designation "2010 ST3."

"Although this particular object won't hit Earth in the immediate future, its discovery shows that Pan-STARRS is now the most sensitive system dedicated to discovering potentially dangerous asteroids," said Dr. Robert Jedicke, a University of Hawaii member of the PS1 Scientific Consortium (PS1SC), who is working on the asteroid data from the telescope.

"This object was discovered when it was too far away to be detected by other asteroid surveys," Jedicke noted.

Most of the largest PHOs have already been catalogued, but scientists suspect that there are many more under a mile across that have not yet been discovered. These could cause devastation on a regional scale if they ever hit our planet. Such impacts are estimated to occur once every few thousand years.

NEO's and killer Asteroids: US interstellar defense shield

killer-space-rocks-americas-interstellar-defense-shield

Pan-Starrs/Brett Simison

The end of the world is coming but we’re prepared for it.

Astronomers in Haleakala, Hawaii have announced that the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) telescope, PS1, is fully operational. Pan-STARRS will search for killer asteroids, supernovae (exploding stars) and other objects.

The facility in Hawaii boasts one of the largest digital cameras in the world, a 1,400 megapixel (1,400,000,000 pixels) device that can photograph and map one sixth of the sky every month. Pan-STARRS will allow astronomers to track any potential threats to the Earth.

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