Close Encounter with the Tarantula

Tarantula Nebula

Credit: ESA/Hubble& NASA

Acknowledgement: Judy Schmidt

Turning its 2.4-metre eye to the Tarantula Nebula, the NASA/ESA Hubble Space Telescope has taken this close-up of the outskirts of the main cloud of the Nebula.

The bright wispy structures are the signature of an environment rich in ionised hydrogen gas, called H II by astronomers. In reality these appear red, but the choice of filters and colours of this image, which includes exposures both in visible and infrared light, make the gas appear green.

These regions contain recently formed stars, which emit powerful ultraviolet radiation that ionises the gas around them. These clouds are ephemeral as eventually the stellar winds from the newborn stars and the ionisation process will blow away the clouds, leaving stellar clusters like the Pleiades.

Located in the Large Magellanic Cloud, one of our neighbouring galaxies, and situated at a distance of 170 000 light-years away from Earth, the Tarantula Nebula is the brightest known nebula in the Local Group of galaxies. It is also the largest (around 650 light-years across) and most active star-forming region known in our group of galaxies, containing numerous clouds of dust and gas and two bright star clusters. A recent Hubble image shows a large part of the nebula immediately adjacent to this field of view.

The cluster at the Tarantula nebula’s centre is relatively young and very bright. While it is outside the field of view of this image, the energy from it is responsible for most of the brightness of the Nebula, including the part we see here. The nebula is in fact so luminous that if it were located within 1000 light-years from Earth, it would cast shadows on our planet.

The Tarantula Nebula was host to the closest supernova ever detected since the invention of the telescope, supernova 1987A, which was visible to the naked eye.

The image was produced by Hubble’s Advanced Camera for Surveys, and has a field of view of approximately 3.3 by 3.3 arcminutes.

A version of this image was entered into the Hubble’s Hidden Treasures Image Processing Competition by contestant Judy Schmidt. Hidden Treasures is an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public. The competition has now closed and the results will be published soon.

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Physicists shed new light on supernova mystery

Detection of neutrinos from supernova 1987A strongly supports the gravitational core collapse theory of type II supernovae, but what re-energises the stalled shockwave to allow such an immense explosion to take place remains unknown. The emission of scalar gravitational waves from the neutron core of a collapsing heavy star may provide an explanation.

(Credit: NASA)

Physicists have a new theory on the mysterious mechanism that causes the explosion of massive, or core, stars. These Type II supernovae, the term given to exploding core stars, are huge and spectacular events; intriguing because for a short time they emit as much light as is normally produced by an entire galaxy. In fact, the enormous amount of energy they release is second only to the Big Bang itself. While there is general agreement on how the collapse of a core star begins, how the energy escapes from the star (the process that causes the explosion) is not fully understood. A paper published in Physics Letters B (3 November 2011) offers a new theoretical explanation.

A core star collapses when it runs out of the nuclear fuel it depends on and folds in on itself in less than a second under its own huge weight. This process releases enormous amounts of gravitational energy, causing an explosion. A small fraction of the total energy released during a supernova Type II (collapse of a lone massive star that burns energy through fusion), is emitted as light, the kinetic energy of the exploding stellar envelope is 10 times greater again, but by far the most energy is carried away by neutrinos. It is by studying these neutrinos (among the most difficult particles to detect) that physicists have come to general agreement that gravitational collapse does start the Type II supernova process.

Less understood is whether the outgoing pressure wave causing the explosion - that soon becomes a huge shock wave - travels all the way out and ejects the outer part of the star. Simulations have shown that the prompt shock stalls at distances of about 300 km from the centre because of the immense energy required to keep its momentum. Further simulations have found that the shock could re-start if the electrons could absorb a small amount of energy - about 1% of the neutrino energy available.

Physicists at the University of Aberdeen, STFC’s Rutherford Appleton Laboratory, the University of Strathclyde and the Instituto Superior Técnico in Lisbon suggest in Physics Letters B that the solution to the Type II supernovae mystery might lie in a fundamental field long proposed by physicists to answer many important questions. They claim that a component of gravity called the ‘scalar gravitational field’ may be the driving force behind the release of energy that causes the star to finally explode. The existence of scalar fields are predicted but have not yet been detected.

“Scalar fields, unlike electromagnetic fields do not have a direction. They are needed to explain inflation in the early universe and dark energy in cosmology. They are also being hunted at CERN’s Large Hadron Collider as the Higgs particle, giving rise to the origin of mass. In our case, we believe it is responsible for accelerating particles”, said Professor Bob Bingham from STFC and the University of Strathclyde.

“The theory is that emission of these scalar gravitational waves from the neutron core of a collapsing heavy star may re-energise the stalled shockwave”, added Dr Charles Wang from the University of Aberdeen.

Notes for editors

These scientists in the UK and Portugal have recently analysed the nonlinear coupling (a process by which energy is transferred from one system to another) to this scalar gravitational field. They found that under extreme conditions with strong time-varying gravity such as may be found in the interior of a newly-born neutron star, the scalar gravitational field may be stimulated by a parametric instability (a form of coupling between energy sources). Parametric instabilities were initially studied by Lord Rayleigh over a century ago.

The theory is that emission of these scalar gravitational waves from the neutron core of a collapsing heavy star may re-energise the stalled shockwave. This theoretical possibility for a new mechanism, - a potential solution to the type II supernova mystery is in Physics Letters B (link opens in a new window), Vol 705 (2011), Pages 148 – 151.

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Further information:

University of Aberdeen

Research and the expansion of knowledge is fundamental to the distinguished 500-year history of the University of Aberdeen in Scotland. Ideas that have taken root at the University have gone on to change the world - from pure thought to practical solutions for everyday problems. The study of Physics has a long and illustrious history at the University and former staff include great physicists such as James Clerk Maxwell. Today the team is involved in world-class research in both experimental and theoretical areas, with research topics covering classical areas such as general relativity, solid-state physics and dynamical systems and chaos. Physicists at the University are also involved in multi-disciplinary research topics, especially the application of physics to biology. More information can be found on the University of Aberdeen website. (link opens in a new window)


University of Strathclyde

Since its foundation in 1796, the University of Strathclyde’s vision as a ‘place of useful learning’ has led the way in connecting new ideas to the solution of problems facing society, and producing high quality graduates ready for leadership and the professions. Today, the University is recognised as one of the UK’s leading international technological universities, and prides itself on partnership with the public and private sectors. Its bold vision is to transform research, education and knowledge exchange to deliver useful learning for the technological age. More information can be found on the University of Strathclyde's website.

Instituto Superior Técnico (link opens in a new window)

STFC

The Science and Technology Facilities Council is keeping the UK at the forefront of international science and tackling some of the most significant challenges facing society such as meeting our future energy needs, monitoring and understanding climate change, and global security.

The Council has a broad science portfolio and works with the academic and industrial communities to share its expertise in materials science, space and ground-based astronomy technologies, laser science, microelectronics, wafer scale manufacturing, particle and nuclear physics, alternative energy production, radio communications and radar.

STFC operates or hosts world class experimental facilities including:
in the UK; ISIS pulsed neutron source, the Central Laser Facility, and LOFAR. STFC is also the majority shareholder in Diamond Light Source Ltd.
overseas; telescopes on La Palma and Hawaii

It enables UK researchers to access leading international science facilities by funding membership of international bodies including European Laboratory for Particle Physics (CERN), the Institut Laue Langevin (ILL), European Synchrotron Radiation Facility (ESRF) and the European Southern Observatory (ESO).

STFC is one of seven publicly-funded research councils. It is an independent, non-departmental public body of the Department for Business, Innovation and Skills (BIS).

About STFC

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Hubble Revisits an Old Friend

Supernova SN 1987A
Credit: ESA/Hubble & NASA

Supernova SN 1987A, one of the brightest stellar explosions since the invention of the telescope more than 400 years ago, is no stranger to the NASA/ESA Hubble Space Telescope. The observatory has been on the frontline of studies into this brilliant dying star since its launch in 1990, three years after the supernova exploded on 23 February 1987. This image of Hubble’s old friend, retreived from the telescope’s data archive, may be the best ever of this object, and reminds us of the many mysteries still surrounding it.

Dominating this picture are two glowing loops of stellar material and a very bright ring surrounding the dying star at the centre of the frame. Although Hubble has provided important clues on the nature of these structures, their origin is still largely unknown.

Another mystery is that of the missing neutron star. The violent death of a high-mass star, such as SN 1987A, leaves behind a stellar remnant — a neutron star or a black hole. Astronomers expect to find a neutron star in the remnants of this supernova, but they have not yet been able to peer through the dense dust to confirm it is there.

The supernova belongs to the Large Magellanic Cloud, a nearby galaxy about 168 000 light-years away. Even though the stellar explosion took place around 166 000 BC, its light arrived here less than 25 years ago.

This picture is based on observations done with the High Resolution Channel of Hubble’s Advanced Camera for Surveys. The field of view is approximately 25 by 25 arcseconds.

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Herschel Helps Solve Mystery of Cosmic Dust Origins

This layout compares two pictures of a supernova remnant called SN 1987A -- the left image was taken by the Herschel Space Observatory, and the right is an enlarged view of the circled region at left, taken with NASA's Hubble Space Telescope. Image credit: ESA/NASA-JPL/UCL/STScI. Full image and caption

This plot shows energy emitted from a supernova remnant called SN 1987A. Previously, NASA's Spitzer Space Telescope detected warm dust around the object. Image credit: ESA/NASA-JPL/UCL/STScI . Full image and caption

PASADENA, CALIF. -- New observations from the infrared Herschel Space Observatory reveal that an exploding star expelled the equivalent of between 160,000 and 230,000 Earth masses of fresh dust. This enormous quantity suggests that exploding stars, called supernovae, are the answer to the long-standing puzzle of what supplied our early universe with dust.

"This discovery illustrates the power of tackling a problem in astronomy with different wavelengths of light," said Paul Goldsmith, the NASA Herschel project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., who is not a part of the current study. "Herschel's eye for longer-wavelength infrared light has given us new tools for addressing a profound cosmic mystery."

Herschel is led by the European Space Agency with important contributions from NASA.

Cosmic dust is made of various elements, such as carbon, oxygen, iron and other atoms heavier than hydrogen and helium. It is the stuff of which planets and people are made, and it is essential for star formation. Stars like our sun churn out flecks of dust as they age, spawning new generations of stars and their orbiting planets.

Astronomers have for decades wondered how dust was made in our early universe. Back then, sun-like stars had not been around long enough to produce the enormous amounts of dust observed in distant, early galaxies. Supernovae, on the other hand, are the explosions of massive stars that do not live long.

The new Herschel observations are the best evidence yet that supernovae are, in fact, the dust-making machines of the early cosmos.

"The Earth on which we stand is made almost entirely of material created inside a star," explained the principal investigator of the survey project, Margaret Meixner of the Space Telescope Science Institute, Baltimore, Md. "Now we have a direct measurement of how supernovae enrich space with the elements that condense into the dust that is needed for stars, planets and life."

The study, appearing in the July 8 issue of the journal Science, focused on the remains of the most recent supernova to be witnessed with the naked eye from Earth. Called SN 1987A, this remnant is the result of a stellar blast that occurred 170,000 light-years away and was seen on Earth in 1987. As the star blew up, it brightened in the night sky and then slowly faded over the following months. Because astronomers are able to witness the phases of this star's death over time, SN 1987A is one of the most extensively studied objects in the sky.

A new view from NASA's Hubble Space Telescope showing how supernova 1987A has recently brightened is at http://hubblesite.org/newscenter/archive/releases/2011/21 .

Initially, astronomers weren't sure if the Herschel telescope could even see this supernova remnant. Herschel detects the longest infrared wavelengths, which means it can see very cold objects that emit very little heat, such as dust. But it so happened that SN 1987A was imaged during a Herschel survey of the object's host galaxy -- a small neighboring galaxy called the Large Magellanic Cloud (it's called large because it's bigger than its sister galaxy, the Small Magellanic Cloud).

After the scientists retrieved the images from space, they were surprised to see that SN 1987A was aglow with light. Careful calculations revealed that the glow was coming from enormous clouds of dust -- consisting of 10,000 times more material than previous estimates. The dust is minus 429 to minus 416 degrees Fahrenheit (about minus 221 to 213 Celsius) -- colder than Pluto, which is about minus 400 degrees Fahrenheit (204 degrees Celsius).

"Our Herschel discovery of dust in SN 1987A can make a significant understanding in the dust in the Large Magellanic Cloud," said Mikako Matsuura of University College London, England, the lead author of the Science paper. "In addition to the puzzle of how dust is made in the early universe, these results give us new clues to mysteries about how the Large Magellanic Cloud and even our own Milky Way became so dusty."

Previous studies had turned up some evidence that supernovae are capable of producing dust. For example, NASA's Spitzer Space Telescope, which detects shorter infrared wavelengths than Herschel, found 10,000 Earth-masses worth of fresh dust around the supernova remnant called Cassiopea A. Hershel can see even colder material, and thus the coldest reservoirs of dust. "The discovery of up to 230,000 Earths worth of dust around SN 1987A is the best evidence yet that these monstrous blasts are indeed mighty dust makers," said Eli Dwek, a co-author at NASA Goddard Space Flight Center in Greenbelt, Md.

Other authors include M. Otsuka, J. Roman-Duval, K.S. Long and K.D. Gordon, Space Telescope Science Institute, Baltimore, Md.; B. Babler, University of Wisconsin, Madison; M.J. Barlow, University College London, United Kingdom; C. Engelbracht, K.A. Misselt and E. Montiel, University of Arizona, Tucson; K. Sandstrom, Max Planck Institut für Astronomie, Heidelberg, Germany; M. Lakicevic and J.Th. van Loon, Keele University, United Kingdom; G. Sonneborn, Goddard Space Flight Center, Greenbelt, Md.; G.C. Clayton, Louisiana State University, Baton Rouge; P. Lundqvist, Stockholm, Sweden; T. Nozawa, University of Tokyo, Japan; S. Hony, K. Okumura and M. Sauvage, the French Alternative Energies and Atomic Energy Commission, France.

Herschel is a European Space Agency cornerstone mission, with science instruments provided by consortia of European institutes and with important participation by NASA. NASA's Herschel Project Office is based at NASA's Jet Propulsion Laboratory. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, supports the United States astronomical community. Caltech manages JPL for NASA.

More information is online at http://www.nasa.gov/herschel and http://www.esa.int/SPECIALS/Herschel/index.html .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

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New Supernova Remnant Lights Up

This HST image of SN 1987A shows the brightening ring of supernova debris. The closest supernova explosion seen in almost 400 years, it is located in the Large Magellanic Cloud. Credit: Pete Challis (CfA). High Resolution Image (jpg)

Cambridge, MA - In 1987, light from an exploding star in a neighboring galaxy, the Large Magellanic Cloud, reached Earth. Named Supernova 1987A, it was the closest supernova explosion witnessed in almost 400 years, allowing astronomers to study it in unprecedented detail as it evolves.

Today a team of astronomers announced that the supernova debris, which has faded over the years, is brightening. This shows that a different power source has begun to light the debris, and marks the transition from a supernova to a supernova remnant.

"Supernova 1987A has become the youngest supernova remnant visible to us," said Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics (CfA).

Kirshner leads a long-term study of SN 1987A with NASA's Hubble Space Telescope. Since its launch in 1990, Hubble has provided a continuous record of the changes in SN 1987A.

As shown in the accompanying image, SN 1987A is surrounded by a ring of material that blew off the progenitor star thousands of years before it exploded. The ring is about one light-year (6 trillion miles) across. Inside that ring, the "guts" of the star are rushing outward in an expanding debris cloud.

Most of a supernova's light comes from radioactive decay of elements created in the explosion. As a result, it fades over time. However, the debris from SN 1987A has begun to brighten, suggesting that a new power source is lighting it.

"It’s only possible to see this brightening because SN 1987A is so close and Hubble has such sharp vision," Kirshner said.

A supernova remnant consists of material ejected from an exploding star, as well as the interstellar material it sweeps up. The debris of SN 1987A is beginning to impact the surrounding ring, creating powerful shock waves that generate X-rays observed with NASA's Chandra X-ray Observatory. Those X-rays are illuminating the supernova debris and shock heating is making it glow. The same process powers well-known supernova remnants in our galaxy like Cassiopeia A.

Because it's so young, the remnant of SN 1987A still shows the history of the last few thousand years of the star's life recorded in the knots and whorls of gas. By studying it further, astronomers may decode that history.

"Young supernova remnants have personality," Kirshner agreed.

Eventually, that history will be lost when the bulk of the expanding stellar debris hits the surrounding ring and shreds it. Until then, SN 1987A continues to offer an unprecedented opportunity to watch a cosmic object change over the course of a human lifetime. Few other objects in the sky evolve on such short time-scales.

This research appears in a paper in the June 9, 2011 issue of Nature. The first author is Josefin Larsson (University of Stockholm).

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) 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.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

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