Category: Hubble

Image credit: Hubble

Using the Hubble Space Telescope, astronomers have discovered three of the faintest and small objects ever seen in the Outer Solar System. Each object is a lump of ice and rock, called a Kuiper Object, that could date back to the creation of the Solar System, 4.5 billion years ago. What’s surprising, however, is how few Kuiper Objects the team discovered. They were expecting to find 60 as small as 15 km in the field they surveyed, but only turned up 3.

Astronomers using NASA’s Hubble Space Telescope have discovered three of the faintest and smallest objects ever detected beyond Neptune. Each object is a lump of ice and rock ? roughly the size of Philadelphia ? orbiting beyond Neptune and Pluto, where the icy bodies may have dwelled since the formation of the solar system 4.5 billion years ago. They reside in a ring-shaped region called the Kuiper Belt, which houses a swarm of icy rocks that are leftover building blocks, or “planetesimals,” from the solar system’s creation.

The results of the search were announced by a group led by astronomer Gary Bernstein of the University of Pennsylvania at today’s meeting of the Division of Planetary Sciences in Monterey, Calif.

The study’s big surprise is that so few Kuiper Belt members were discovered. With Hubble’s exquisite resolution, Bernstein and his co- workers expected to find at least 60 Kuiper Belt members as small as 10 miles (15 km) in diameter ? but only three were discovered.

“Discovering many fewer Kuiper Belt objects than was predicted makes it difficult to understand how so many comets appear near Earth, since many comets were thought to originate in the Kuiper Belt,” Bernstein says. “This is a sign that perhaps the smaller planetesimals have been shattered into dust by colliding with each other over the past few billion years.”

Bernstein and his colleagues used Hubble to look for planetesimals that are much smaller and fainter than can be seen from ground-based telescopes. Hubble’s Advanced Camera for Surveys was pointed at a region in the constellation Virgo over a 15-day period in January and February 2003. A bank of 10 computers on the ground worked for six months searching for faint-moving spots in the Hubble images.

The search netted three small objects, named 2003 BF91, 2003 BG91, and 2003 BH91, which range in size from 15-28 miles (25-45 km) across. They are the smallest objects ever found beyond Neptune. At their current locations, these icy bodies are a billion times fainter (29th magnitude) than the dimmest objects visible to the naked eye. But an icy body of this size that escapes the Kuiper Belt to wander near the Sun can become visible from Earth as a comet as the wandering body starts to evaporate and form a surrounding cloud.

Astronomers are probing the Kuiper Belt because the region offers a window on the early history of our solar system. The planets formed over 4 billion years ago from a cloud of gas and dust that surrounded the infant Sun. Microscopic bits of ice and dust stuck together to form lumps that grew from pebbles to boulders to city- or continent-sized planetesimals. The known planets and moons are the result of collisions between planetesimals. In most of the solar system, all of the planetesimals have either been absorbed into planets or ejected into interstellar space, destroying the traces of the early days of the solar system.

Around 1950, Gerard Kuiper and Kenneth Edgeworth proposed that in the region beyond Neptune there are no planets capable of ejecting the leftover planetesimals. There should be a zone, the two astronomers said? now called the Kuiper Belt ? filled with small, icy bodies. Despite many years of searching, the first such object was not found until 1992. Since then, astronomers have discovered nearly 1,000 from ground-based telescopes. Most astronomers now believe that Pluto, discovered in 1930, is in fact a member of the Kuiper Belt.

Astronomers now use the Kuiper Belt to learn about the history of the solar system, much as paleontologists use fossils to study early life. Each event that affected the outer solar system ? such as possible gravitational disturbances from passing stars or long-vanished planets ? is frozen into the properties of the Kuiper Belt members that astronomers see today.

If the Hubble telescope could search the entire sky, it would find perhaps a half million planetesimals. If collected into a single planet, however, the resulting object would be only a few times larger than Pluto. The new Hubble observations, combined with the latest ground-based Kuiper Belt surveys, reinforce the idea that Pluto itself and its moon Charon are just large Kuiper Belt members. Why the Kuiper Belt planetesimals did not form a larger planet, and why there are fewer small planetesimals than expected, are questions that will be answered with further Kuiper Belt studies. These studies will help astronomers understand how planets may have formed around other stars as well.

The new Hubble results were reported by Bernstein and David Trilling (University of Pennsylvania); Renu Malhotra (University of Arizona); Lynne Allen (University of British Columbia); Michael Brown (California Institute of Technology); and Matthew Holman (Harvard-Smithsonian Center for Astrophysics). The results have been submitted to the Astronomical Journal for publication, and a preliminary report is available on the Web at http://arxiv.org/abs/astro-ph/0308467.

Original Source: Hubble News Release

Image credit: Hubble

The latest image released from the Hubble Space Telescope is of the spiral galaxy NGC 3370, located in the constellation Leo. The galaxy was imaged because astronomers wanted to observe Cepheid variable stars – special stars which brighten and dim at a known rate and are used to calculate distances to objects. The team had to make a long exposure of the galaxy (about a full day), so Hubble had a chance to gather a lot of light; that’s why there are many fainter galaxies visible in the background of the picture.

Amid a backdrop of far-off galaxies, the majestic dusty spiral, NGC 3370, looms in the foreground in this NASA Hubble Space Telescope image. Recent observations taken with the Advanced Camera for Surveys show intricate spiral arm structure spotted with hot areas of new star formation. But this galaxy is more than just a pretty face. Nearly 10 years earlier NGC 3370, in the constellation Leo, hosted a bright exploding star.

In November 1994, the light of a supernova in nearby NGC 3370 reached Earth. This stellar outburst briefly outshone all of the tens of billions of other stars in its galaxy. Although supernovae are common, with one exploding every few seconds somewhere in the universe, this one was special. Designated SN 1994ae, this supernova was one of the nearest and best observed supernovae since the advent of modern, digital detectors. It resides 98 million light-years (30 megaparsecs) from Earth. The supernova was also a member of a special subclass of supernovae, the type Ia, the best tool astronomers have to chart the growth rate of the expanding universe.

Recently, astronomers have compared nearby type Ia supernovae to more distant ones, determining that the universe is now accelerating in its expansion and is filled with mysterious “dark energy.” Such measurements are akin to measuring the size of your room by stepping it off with your feet. However, a careful measurement of the length of your foot (to convert your measurements into inches or centimeters) is still needed to know the true size of your room. Similarly, astronomers must calibrate the true brightness of type Ia supernovae to measure the true size and expansion rate of the universe.

The very nearest type Ia supernovae, such as SN 1994ae, can be used to calibrate distance measurements in the universe, because other, fainter stars of known brightness can be observed in the same galaxy. These stellar “standard candles” are the Cepheid variable stars, which vary regularly in brightness with periods that are directly related to their intrinsic brightness, and thus allow the distance to the galaxy?and the supernova?to be determined directly. However, only the Hubble Space Telescope, equipped with its new Advanced Camera for Surveys, has the capability to resolve these individual Cepheids.

Adam Riess, an astronomer at Space Telescope Science Institute in Baltimore, Md., observed NGC 3370 a dozen times over the course of a month and has seen many Cepheid variables. Already he and his colleagues can see that these Cepheids are the most distant yet observed with Hubble. Because of their need to observe this galaxy with great frequency to record the variation of the Cepheids, the total exposure time for this galaxy is extremely long (about one full day), and the combined image provides one of the deepest views taken by Hubble. As a result, thousands of distant galaxies in the background are easily discernable.

Dr. Riess imaged NGC 3370 with Hubble in early 2003. His science only required looking at NGC 3370 in two filters that covered the visual and infrared portions of the spectrum. By teaming up with the Hubble Heritage Project, a third blue filter was added to the data to produce the composite three-color image that is shown.

Credit: NASA, The Hubble Heritage Team and A. Riess (STScI)

Source: Hubble Press Release

Image credit: NASA

A NASA panel released three options for the future of the Hubble Space Telescope after its last servicing mission in 2004 or 2005 which will extend its life to 2010. The first idea is to do another servicing mission in 2010 and keep Hubble operating as long as possible. The second option is to just do the single servicing mission around 2006 and install a propulsion device which would allow NASA to de-orbit the telescope by remote control. And the third possibility is to launch a robotic mission that will attach a propulsion device so Hubble can be de-orbited later.

An independent panel of astronomers identified three options for NASA to consider for planning the transition from the Hubble Space Telescope (HST) to the James Webb Space Telescope (JWST) at the start of the next decade.

The panel, chaired by Prof. John Bahcall, Institute for Advanced Study, Princeton, N.J., chartered by NASA earlier this year, submitted their report to the agency this week.

NASA’s current plans are to extend the life of the HST to 2010 with one Space Shuttle servicing mission (SM 4) in 2005 or 2006. The plan is tentative pending the agency’s return to flight process and the availability of Shuttle missions. NASA plans to eventually remove the HST from orbit and safely bring it down into the Pacific Ocean.

“NASA is deeply appreciative to Prof. Bahcall and the panel for getting this thoughtful report to us ahead of schedule,” said Dr. Ed Weiler, NASA’s Associate Administrator for Space Science. “We have a big job to do to study the panel’s findings and consider our options, and we will respond as soon as we have time to evaluate their report,” Weiler said.

The three options presented by the HST-JWST Transition Plan Review Panel, listed in order of priority, are:

“1. Two additional Shuttle servicing missions, SM4 in about 2005 and SM5 in about 2010, in order to maximize the scientific productivity of the Hubble Space Telescope. The extended HST science program resulting from SM5 would only occur if the HST science was successful in a peer-reviewed competition with other new space astrophysics proposals.”

“2. One Shuttle servicing mission, SM4, before the end of 2006, which would include replacement of HST gyros and installing improved instruments. In this scenario, the HST could be de-orbited, after science operations are no longer possible, by a propulsion device installed on the HST during SM4 or by an autonomous robotic system.”

“3. If no Shuttle servicing missions are available, a robotic mission to install a propulsion module to bring the HST down in a controlled descent when science is no longer possible.”

In addition, the panel described various ways to ensure maximum science return from the HST if none, one or two Shuttle servicing missions are available.

“A lot of astronomers and NASA officials were astonished, when we said our report was ready just one week after our public meeting. This was possible because we reached unanimous agreement on our conclusions very quickly; remarkable when you consider there were six independent-minded scientists on the panel. Our secret is we did our homework very thoroughly. Many people helped to educate us,” Bahcall said.

For information about NASA and space science on the Internet, visit:

Home Page

The HST-JWST Transition Panel report is available on the Internet at:

http://www.nasa.gov/audience/formedia/features/MP_Public_Reports.html

Information about the panel, including membership and charter, is available at:

http://hst-jwst-transition.hq.nasa.gov/hst-jwst/

For information about the Hubble Space Telescope on the Internet, visit:

http://oposite.stsci.edu/

For information about the James Webb Space Telescope on the Internet, visit:

http://ngst.gsfc.nasa.gov/

Original Source: NASA News Release

A new image taken by the Hubble Space Telescope shows a large galaxy gobbling up a smaller one; a process anticipated by astronomers, but never directly seen before. Astronomers used the Keck Telescope in Hawaii to confirm that the dwarf galaxy is being consumed by measuring the rate that stars are streaming towards the larger galaxy. The stars of the smaller galaxy will eventually form a spherical halo surrounding the flattened disk of the larger galaxy.

Image credit: Hubble

The newest image from the Hubble Space Telescope reveals one of the nearest globular star clusters, NGC 6397, located only 8,200 light years away in the constellation Ara. The stars in this cluster are packed one million times more densely than our own galactic neighborhood; collisions between stars occur every few million years. Two colliding stars may merge to become a “blue straggler”; a bright, young hot star that looks very different from the rest of the stars in the cluster.

This Hubble Space Telescope view of the core of one of the nearest globular star clusters, called NGC 6397, resembles a treasure chest of glittering jewels. The cluster is located 8,200 light-years away in the constellation Ara.

Here, the stars are jam-packed together. The stellar density is about a million times greater than in our Sun’s stellar neighborhood. The stars are only a few light-weeks apart, while the nearest star to our Sun is over four light-years away.

The stars in NGC 6397 are in constant motion, like a swarm of angry bees. The ancient stars are so crowded together that a few of them inevitably collide with each other once in a while. Near misses are even more common. Even so, collisions only occur every few million years or so. That’s thousands of collisions in the 14-billion-year lifetime of the cluster.

These Hubble images were taken for a research program aimed at studying what is left behind when such collisions and near misses occur. When direct collisions occur, the two stars may merge to form a new star called a “blue straggler”; these hot, bright, young stars stand out among the old stars that make up the vast majority of stars in a globular cluster. Several such bright blue stars are visible near the center of the cluster in the Hubble Heritage image.

If two stars come close enough together without actually colliding, they may “capture” each other and become gravitationally bound. One type of binary that might form this way is a “cataclysmic variable”? a pairing of a normal, hydrogen-burning star and a burned-out star called a white dwarf. In a binary system, the white dwarf will pull material off the surface of the normal star. This material encircles the white dwarf in an “accretion disk,” and eventually falls onto it. The result of this accretion process is that cataclysmic variables are, as the name suggests, variable in brightness. The heat generated by the accreting material also generates unusual amounts of ultraviolet and blue light.

To search for cataclysmic variables, the program consisted of a series of 55 images of the cluster taken over a period of about 20 hours. Most of the images were taken in ultraviolet and blue filters; a few images were also taken at green and infrared wavelengths. By comparing the brightness of all the stars in all the images, the Hubble astronomers were able to identify several cataclysmic variable stars in the cluster. Comparison of their brightness in the different filters confirmed that they were emitting copious amounts of ultraviolet light. A few of these stars can be seen in the Hubble Heritage image as faint blue or violet stars.

One of the more intriguing results of this study was completely unexpected. Three faint blue stars can be seen near the center of the cluster ? in the Hubble Heritage image they appear turquoise. These three stars don’t vary in brightness at all, and were clearly not cataclysmic variables. These stars may be very-low-mass white dwarfs, formed in the cores of giant stars whose evolution is somehow interrupted before a full-fledged white dwarf has time to form.

Such an interruption might occur as the result of a stellar collision or an interaction with a binary companion. When a giant star interacts with another star, it can lose its outer layers prematurely, compared to its normal evolution, exposing its hot, blue core. The end result will be a white dwarf of a smaller mass than would have otherwise ensued. In any case, these unusual stars are yet more evidence that the center of a dense globular cluster is a perilous place to reside.

A large number of normal white dwarfs were also identified and studied. These stars appear throughout the cluster, since they form through normal stellar evolution processes and don’t involve any stellar interactions, which occur predominantly near the cluster center. Nearly 100 such burned-out stars were identified in these images, the brightest of which can be seen here as faint blue stars.

This Hubble image is a mosaic of two sets of images taken several years apart by the Wide Field Planetary Camera 2. Archival data from science teams led by Jonathan Grindlay (Harvard University) and Ivan King (University of California, Berkeley), taken in 1997 and 1999, were combined with Hubble Heritage data taken in 2001. Adrienne Cool (San Francisco State University), who was also on both archival science teams, worked with the Hubble Heritage team to acquire the new observations.

Original Source: Hubble News Release

Image credit: NASA

The Hubble Space Telescope, one of the most important scientific instruments ever created, is entering the final chapter of its life, and NASA is trying to figure out what they should do with it. The Hubble Space Telescope was launched in 1990, and it’s expected to continue operations until 2010, when it’s replaced by the James Webb observatory which will launch in 2011. NASA has convened a special panel of experts to determine the best way to handle the transition.

The Hubble Space Telescope (HST) is one of the most important scientific facilities of NASA and indeed of the world. The HST has created enormous interest in astronomy and in space science, contributing in the process fundamental scientific discoveries related to the origins of the universe, the structure and evolution of the universe, and the exploration of the solar system. The scientific community has endorsed the James Webb Space Telescope as the next generation space telescope, the natural successor to the HST. It is a necessary task to consider exactly how and when to terminate the operation of this successful scientific experiment.

Currently, the end of Hubble operations is planned for 2010, and the launch of JWST is planned for late 2011. In principle, HST operations could be enhanced through continued servicing by the space shuttle. In fact, servicing may be essential to reach the 2010 target date. However, servicing missions by the shuttle are expensive and inherently dangerous.

NASA would like to assess the scientific impact of its current plan for effecting the transition from HST to JWST in the context of its overall space science program. In addition, NASA would like to determine if there are modifications to this plan that may better address key scientific issues within the constraints provided by the agency?s strategic plan and budget.

To this end NASA has chartered a panel of senior community members, with John Bahcall serving as chair, to review agency plans and to receive community input on the HST – JWST transition topic. The links below lead to the panel’s charter, membership roster, information about a public meeting on the topic and pages for people to provide the panel with their views via email. [Input closed August 13, 2003]

The final report from the HST-JWST Transition Panel may be found here.

Original Source: NASA Status Report

Image credit: Hubble

The most recent image taken by the Hubble Space Telescope shows the delicate looking remnants from a supernova explosion in our nearest galaxy. The remnant, called LMC N 49, is located in the Large Magellanic Cloud, and the supernova would have been visible several thousand years ago. At the core of the object is a rapidly-spinning neutron star which has a magnetic field a quadrillion times stronger than the Earth’s field; objects like this are called magnetars.

Resembling the puffs of smoke and sparks from a summer fireworks display in this image from NASA’s Hubble Space Telescope, these delicate filaments are actually sheets of debris from a stellar explosion in a neighboring galaxy. Hubble’s target was a supernova remnant within the Large Magellanic Cloud (LMC), a nearby, small companion galaxy to the Milky Way visible from the southern hemisphere.

Denoted N 49, or DEM L 190, this remnant is from a massive star that died in a supernova blast whose light would have reached Earth thousands of years ago. This filamentary material will eventually be recycled into building new generations of stars in the LMC. Our own Sun and planets are constructed from similar debris of supernovae that exploded in the Milky Way billions of years ago.

This seemingly gentle structure also harbors a very powerful spinning neutron star that may be the central remnant from the initial blast. It is quite common for the core of an exploded supernova star to become a spinning neutron star (also called a pulsar – because of the regular pulses of energy from the rotational spin) after the immediate shedding of the star’s outer layers. In the case of N 49, not only is the neutron star spinning at a rate of once every 8 seconds, it also has a super-strong magnetic field a thousand trillion times stronger than Earth’s magnetic field. This places this star into the exclusive class of objects called “magnetars.”

On March 5, 1979, this neutron star displayed a historic gamma-ray burst episode that was detected by numerous Earth-orbiting satellites. Gamma rays have a million or more times the energy of visible light photons. The Earth’s atmosphere protects us by blocking gamma rays that originate from outer space. The neutron star in N 49 has had several subsequent gamma-ray emissions, and is now recognized as a “soft gamma-ray repeater.” These objects are a peculiar class of stars producing gamma rays that are less energetic than those emitted by most gamma-ray bursters.

The neutron star in N 49 is also emitting X-rays, whose energies are slightly less than that of soft gamma rays. High-resolution X-ray satellites have resolved a point source near the center of N 49, the likely X-ray counterpart of the soft gamma-ray repeater. Diffuse filaments and knots throughout the supernova remnant are also visible in X-ray. The filamentary features visible in the optical image represent the blast wave sweeping through the ambient interstellar medium and nearby dense molecular clouds.

Today, N 49 is the target of investigations led by Hubble astronomers You-Hua Chu from the University of Illinois at Urbana-Champaign and Rosa Williams from the University of Massachusetts. Members of this science team are interested in understanding whether small cloudlets in the interstellar medium of the LMC may have a marked effect on the physical structure and evolution of this supernova remnant.

The Hubble Heritage image of N 49 is a color representation of data taken in July 2000, with Hubble’s Wide Field Planetary Camera 2. Color filters were used to sample light emitted by sulfur ([S II]), oxygen ([O III]), and hydrogen (H-alpha). The color image has been superimposed on a black-and-white image of stars in the same field also taken with Hubble.

Original Source: Hubble News Release

Image credit: Hubble

A new series of images taken by the Hubble Space Telescope contain 25,000 galaxies, many of which are interacting and in the process of formation. Some of these galaxies are so far away, they’re seen when the Universe was only 2 billion years old. Astronomers are using Hubble and the Chandra X-Ray observatory to survey two large areas of the sky to build a deeper understanding of galaxy evolution.

NASA’s Hubble Space Telescope reached back to nearly the beginning of time to sample thousands of infant galaxies. This image, taken with Hubble’s Advanced Camera for Surveys, shows several thousand galaxies, many of which appear to be interacting or in the process of forming. Some of these galaxies existed when the cosmos was less than about 2 billion years old. The foreground galaxies, however, are much closer to Earth. Two of them [the white, elongated galaxies, left of center] appear to be colliding.

This image represents less than one-tenth of the entire field surveyed by Hubble. The full field, consisting of about 25,000 galaxies, is part of a larger survey called the Great Observatories Origins Deep Survey (GOODS), the most ambitious study of the early universe yet undertaken with the Hubble telescope. This survey targeted two representative spots in the sky – one in the Northern Hemisphere and the other in the Southern Hemisphere. This image represents the southern field, located in the constellation Fornax. The entire GOODS survey reveals roughly 50,000 galaxies. Astronomers have identified more than 2,000 of them as infant galaxies, observed when the universe was less than about 2 billion years old.

Because infant galaxies are very faint and very rare, astronomers are using Hubble to search for them over a relatively wide swath of sky. In fact, the new observations cover about 60 times the area of the original Hubble Deep Field Observations, obtained in 1995. Astronomers also are using the Chandra X-ray Observatory to search the GOODS fields for the earliest black holes in the universe. The Space Infrared Telescope Facility (SIRTF) will sample these same fields soon after it is launched in August 2003.

By combining light from all three of NASA’s great observatories with data from ground-based telescopes, astronomers hope to build a coherent picture of galaxy evolution.

This image of the southern field was assembled from observations taken between July 2002 and February 2003.

Original Source: Hubble News Release

Image credit: Hubble

The Hubble Space Telescope has taken a new image of the Pencil Nebula, officially known as NGC 2736, which is part of the huge Vela supernova remnant located 815 light-years away. The nebula’s luminous appearance comes from dense gas regions which have been struck by the supernova’s shock wave and heated up. Astronomers estimate that the supernova went off 11,000 years ago; although, no historical records of the explosion have ever been found.

Remnants from a star that exploded thousands of years ago created a celestial abstract portrait, as captured in this NASA Hubble Space Telescope image of the Pencil Nebula.

Officially known as NGC 2736, the Pencil Nebula is part of the huge Vela supernova remnant, located in the southern constellation Vela. Discovered by Sir John Herschel in the 1840s, the nebula’s linear appearance triggered its popular name. The nebula’s shape suggests that it is part of the supernova shock wave that recently encountered a region of dense gas. It is this interaction that causes the nebula to glow, appearing like a rippled sheet.

In this snapshot, astronomers are looking along the edge of the undulating sheet of gas. This view shows large, wispy filamentary structures, smaller bright knots of gas, and patches of diffuse gas. The Hubble Heritage Team used the Advanced Camera for Surveys in October 2002 to observe the nebula. The region of the Pencil Nebula captured in this image is about three fourths of a light-year across. The Vela supernova remnant is 114 light-years (35 parsecs) across. The remnant is about 815 light-years (250 parsecs) away from our solar system.

The nebula’s luminous appearance comes from dense gas regions that have been struck by the supernova shock wave. As the shock wave travels through space [from right to left in the image], it rams into interstellar material. Initially the gas is heated to millions of degrees, but then subsequently cools down, emitting the optical light visible in the image.

The colors of the various regions in the nebula yield clues about this cooling process. Some regions are still so hot that the emission is dominated by ionized oxygen atoms, which glow blue in the picture. Other regions have cooled more and are seen emitting red in the image (cooler hydrogen atoms). In this situation, color shows the temperature of the gas. The nebula is visible in this image because it is glowing.

The supernova explosion left a spinning pulsar at the core of the Vela region. Based on the rate at which the pulsar is slowing down, astronomers estimate that the explosion may have occurred about 11,000 years ago. Although no historical records of the blast exist, the Vela supernova would have been 250 times brighter than Venus and would have been easily visible to southern observers in broad daylight. The age of the blast, if correct, would imply that the initial explosion pushed material from the star at nearly 22 million miles per hour. As the Vela supernova remnant expands, the speed of its moving filaments, such as the Pencil Nebula, decreases. The Pencil Nebula, for example, is moving at roughly 400,000 miles per hour.

Original Source: Hubble News Release

Image credit: ESA

Astronomers from the European Space Agency have uncovered a bizarre mystery. They?ve found strange jets emerging from a planetary nebula called Henize 3-1475. Even more unusual is the shape of the jets, which curve back on opposite sides like water coming from a rotating garden sprinkler. Their theory is that a large star at the centre of the nebula is emanating the jets as it slowly turns, once every 1,500 years. Furthermore, the flow isn?t smooth, it?s all bubbled and knotted, leading the astronomers to believe new gas blasts out every 100 years or so.

There are many mysterious objects seen in the night sky which are not really well understood. For example, astronomers are puzzled by the ‘jets’ emerging from planetary nebulae. However, the S-shaped jet from Henize 3-1475 is the most perplexing of all.

‘Jets’ are long outflows of fast-moving gas found near many objects in the Universe, such as around young stars, or coming from black holes, neutron stars, and planetary nebulae, for example. The NASA/ESA Hubble Space Telescope has imaged the young planetary nebula Henize 3-1475 and its bizarre jet. Astronomers have nicknamed it the ‘Garden-sprinkler’ Nebula.

The origin of jets in the Universe is unclear, but they appear to originate in small regions of space where even Hubble’s sharp vision cannot penetrate. To produce a jet, you require some sort of nozzle mechanism. So far, these theoretical ‘nozzles’ remain hidden by dust that obscures our view of the centres of planetary nebulae.

Despite decades of intense effort, there is no single example of a jet whose origin is clearly understood. The curious S-shape and extreme high speed of its gaseous outflow gives Henize 3-1475 a special place in the study of planetary nebulae.

Henize 3-1475 is located in the constellation of Sagittarius around 18 000 light-years away from us. The central star is more than 12 000 times as luminous as our Sun and weighs three to five times as much. With a velocity of around 4 million kilometres per hour, the jets are the fastest ever discovered. Scientists are also intrigued by the converging, funnel-shaped structures that connect the innermost ‘knots’ and the core region.

A group of international astronomers led by Angels Riera from Universitat Polit?cnica de Catalunya, Barcelona, Spain, have combined observations from Hubble’s Wide Field and Planetary Camera 2, the Space Telescope Imaging Spectrograph and ground-based telescopes. Their work suggests that the nebula’s S-shape and hypervelocity outflow is created by a central source that ejects streams of gas in opposite directions and precesses once every 1500 years. It is like an enormous, slowly rotating garden sprinkler.

The flow is not smooth, but rather episodic with an interval of about 100 years, creating clumps of gas moving away at velocities up to 4 million kilometres per hour. The reason for these intermittent ejections of gas is not known. It may be due to either cyclic magnetic processes in the central star (similar to the Sun’s 22-year magnetic cycle), or to interactions with a companion star.

Original Source: ESA News Release