Category: Hubble

Image credit: Hubble

The latest image release from the Hubble Space Telescope is of the “Little Ghost Nebula”; a.k.a. NGC 6369, located several thousand light years from Earth in the constellation of Ophiuchus. The nebula was created when a star like our own Sun entered the final stages of its life and expelled its outer layers into space. The glow is caused by the ultraviolet light streaming from the star and heating up the surrounding gas and dust.

NASA’s Hubble Space Telescope has recently obtained images of the planetary nebula NGC 6369. This object is known to amateur astronomers as the “Little Ghost Nebula,” because it appears as a small, ghostly cloud surrounding the faint, dying central star. NGC 6369 lies in the direction of the constellation Ophiuchus, at a distance estimated to be between about 2,000 and 5,000 light-years from Earth.

When a star with a mass similar to that of our own Sun nears the end of its lifetime, it expands in size to become a red giant. The red-giant stage ends when the star expels its outer layers into space, producing a faintly glowing nebula. Astronomers call such an object a planetary nebula, because its round shape resembles that of a planet when viewed with a small telescope.

The Hubble photograph of NGC 6369, captured with the Wide Field Planetary Camera 2 (WFPC2) in February 2002, reveals remarkable details of the ejection process that are not visible from ground-based telescopes because of the blurring produced by the Earth’s atmosphere.

The remnant stellar core in the center is now sending out a flood of ultraviolet (UV) light into the surrounding gas. The prominent blue-green ring, nearly a light-year in diameter, marks the location where the energetic UV light has stripped electrons off of atoms in the gas. This process is called ionization. In the redder gas at larger distances from the star, where the UV light is less intense, the ionization process is less advanced. Even farther outside the main body of the nebula, one can see fainter wisps of gas that were lost from the star at the beginning of the ejection process.

The color image has been produced by combining WFPC2 pictures taken through filters that isolate light emitted by three different chemical elements with different degrees of ionization. The doughnut-shaped blue-green ring represents light from ionized oxygen atoms that have lost two electrons (blue) and from hydrogen atoms that have lost their single electrons (green). Red marks emission from nitrogen atoms that have lost only one electron.

Our own Sun may eject a similar nebula, but not for another 5 billion years. The gas will expand away from the star at about 15 miles per second, dissipating into interstellar space after some 10,000 years. After that, the remnant stellar ember in the center will gradually cool off for billions of years as a tiny white dwarf star, and eventually wink out.

Original Source: Hubble News Release

Image credit: Hubble

The latest photo taken by the Hubble Space Telescope is of a rare type of galaxy, known as Hoag’s Object, where a ring of stars orbit a yellow nucleus. The bluish outer ring is composed of clusters of hot, young stars while the heart is made of mostly older stars. It’s possible that the “gap” in between contains star clusters too faint to see.

A nearly perfect ring of hot, blue stars pinwheels about the yellow nucleus of an unusual galaxy known as Hoag’s Object. This image from NASA’s Hubble Space Telescope captures a face-on view of the galaxy’s ring of stars, revealing more detail than any existing photo of this object. The image may help astronomers unravel clues on how such strange objects form.

The entire galaxy is about 120,000 light-years wide, which is slightly larger than our Milky Way Galaxy. The blue ring, which is dominated by clusters of young, massive stars, contrasts sharply with the yellow nucleus of mostly older stars. What appears to be a “gap” separating the two stellar populations may actually contain some star clusters that are almost too faint to see. Curiously, an object that bears an uncanny resemblance to Hoag’s Object can be seen in the gap at the one o’clock position. The object is probably a background ring galaxy.

Ring-shaped galaxies can form in several different ways. One possible scenario is through a collision with another galaxy. Sometimes the second galaxy speeds through the first, leaving a “splash” of star formation. But in Hoag’s Object there is no sign of the second galaxy, which leads to the suspicion that the blue ring of stars may be the shredded remains of a galaxy that passed nearby. Some astronomers estimate that the encounter occurred about 2 to 3 billion years ago.

This unusual galaxy was discovered in 1950 by astronomer Art Hoag. Hoag thought the smoke-ring-like object resembled a planetary nebula, the glowing remains of a Sun-like star. But he quickly discounted that possibility, suggesting that the mysterious object was most likely a galaxy. Observations in the 1970s confirmed this prediction, though many of the details of Hoag’s galaxy remain a mystery.

The galaxy is 600 million light-years away in the constellation Serpens. The Wide Field and Planetary Camera 2 took this image on July 9, 2001.

Original Source: Hubble News Release

Image credit: Hubble

The newest image release from the Hubble Space Telescope is of the shredded remnants of Cassiopeia A, a star that went supernova more than 10,000 years ago – the youngest known supernova in our galaxy. Debris has formed into thousands of cooling knots of gas and dust, and will eventually supply new star systems with heavier elements such as oxygen and sulphur.

Glowing gaseous streamers of red, white, and blue ? as well as green and pink ? illuminate the heavens like Fourth of July fireworks. The colorful streamers that float across the sky in this photo taken by NASA’s Hubble Space Telescope were created by one of the biggest firecrackers seen to go off in our galaxy in recorded history, the titanic supernova explosion of a massive star. The light from the exploding star reached Earth 320 years ago, nearly a century before our United States celebrated its birth with a bang.

The dead star’s shredded remains are called Cassiopeia A, or “Cas A” for short. Cas A is the youngest known supernova remnant in our Milky Way Galaxy and resides 10,000 light-years away in the constellation Cassiopeia, so the star actually blew up 10,000 years before the light reached Earth in the late 1600s.

This stunning Hubble image of Cas A is allowing astronomers to study the supernova’s remains with great clarity, showing for the first time that the debris is arranged into thousands of small, cooling knots of gas. This material eventually will be recycled into building new generations of stars and planets. Our own Sun and planets are constructed from the debris of supernovae that exploded billions of years ago.

This photo shows the upper rim of the supernova remnant’s expanding shell. Near the top of the image are dozens of tiny clumps of matter. Each small clump, originally just a small fragment of the star, is tens of times larger than the diameter of our solar system.

The colors highlight parts of the debris where chemical elements are glowing. The dark blue fragments, for example, are richest in oxygen; the red material is rich in sulfur.

The star that created this colorful show was a big one, about 15 to 25 times more massive than our Sun. Massive stars like the one that created Cas A have short lives. They use up their supply of nuclear fuel in tens of millions of years, 1,000 times faster than our Sun. With their fuel exhausted, heavy stars begin a complex chain of events that lead to the final dramatic explosion. Their cores rapidly collapse, releasing an enormous amount of gravitational energy. This sudden burst of energy reverses the collapse and tosses most of the star’s mass into space. The ejected material can travel as fast as 45 million miles per hour (72 million kilometers per hour).

The images were taken with the Wide Field and Planetary Camera 2 in January 2000 and January 2002.

Original Source: Hubble News Release

Image credit: Hubble

The most recently released photograph taken by the Hubble Space Telescope is of wispy nebula IC 4406, dubbed the “Retina Nebula”. The object is a ring of dust and gas around a dying star and is nearly perfectly symmetrical. One of the more interesting features is the lattice of dark lanes that crisscross the centre of the nebula, each of which is 160 astronomical units wide (1 AU is the distance from the Earth to the Sun). The photograph is a composite of images taken in June 2001 and January 2002.

A dying star, IC 4406, dubbed the “Retina Nebula” is revealed in this month’s Hubble Heritage image.

Like many other so-called planetary nebulae, IC 4406 exhibits a high degree of symmetry; the left and right halves of the Hubble image are nearly mirror images of the other. If we could fly around IC 4406 in a starship, we would see that the gas and dust form a vast donut of material streaming outward from the dying star. From Earth, we are viewing the donut from the side. This side view allows us to see the intricate tendrils of dust that have been compared to the eye’s retina. In other planetary nebulae, like the Ring Nebula (NGC 6720), we view the donut from the top.

The donut of material confines the intense radiation coming from the remnant of the dying star. Gas on the inside of the donut is ionized by light from the central star and glows. Light from oxygen atoms is rendered blue in this image; hydrogen is shown as green, and nitrogen as red. The range of color in the final image shows the differences in concentration of these three gases in the nebula.

Unseen in the Hubble image is a larger zone of neutral gas that is not emitting visible light, but which can be seen by radio telescopes.

One of the most interesting features of IC 4406 is the irregular lattice of dark lanes that criss-cross the center of the nebula. These lanes are about 160 astronomical units wide (1 astronomical unit is the distance between the Earth and Sun). They are located right at the boundary between the hot glowing gas that produces the visual light imaged here and the neutral gas seen with radio telescopes. We see the lanes in silhouette because they have a density of dust and gas that is a thousand times higher than the rest of the nebula. The dust lanes are like a rather open mesh veil that has been wrapped around the bright donut.

The fate of these dense knots of material is unknown. Will they survive the nebula’s expansion and become dark denizens of the space between the stars or simply dissipate?

This image is a composite of data taken by Hubble’s Wide Field Planetary Camera 2 in June 2001 by Bob O’Dell (Vanderbilt University) and collaborators and in January 2002 by The Hubble Heritage Team (STScI). Filters used to create this color image show oxygen, hydrogen, and nitrogen gas glowing in this object.

Original Source: Hubble News Release

Image credit: Hubble

The Hubble Space Telescope’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) is functioning again, thanks to the refurbishing it got from a recent space shuttle mission. The telescope’s infrared capabilities ended when the NICMOS ran out of coolant three years ago. To showcase its capabilities, Hubble controllers release a series of images today, including the Cone Nebula – brilliant in infrared.

After more than three years of inactivity, and thanks to a new cryogenic refrigerator, the Hubble Space Telescope’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) today debuts various breathtaking views of galaxies in several stages of development.

The first NICMOS test images demonstrate its powerful new capability for making remarkable discoveries unique to space-based near-infrared astronomy. The NICMOS’s penetrating vision sliced through the edge-on dusty disk of a galaxy, NGC 4013, to peer all the way into the galaxy’s core. Astronomers were surprised to see what appears to be an edge-on ring of stars, 720 light-years across, encircling the nucleus. Though such star-rings are not uncommon in barred spiral galaxies, only NICMOS has the resolution to see the ring buried deep inside an edge-on galaxy.

Shifting its infrared vision to our stellar backyard, NICMOS peeled back the outer layers of the Cone Nebula (also photographed by Hubble’s Advanced Camera for Surveys in April) to see the underlying dusty “bedrock” in this stellar “pillar of creation.”

“It is fantastic that we have restored Hubble’s infrared eyesight. NICMOS has taken us to the very fringes of the Universe and to a time when the first galaxies were formed. We can’t wait to get back out there,” said Dr. Rodger Thompson, NICMOS Principal Investigator, University of Arizona, Tucson.

Installed on Hubble in February 1997, NICMOS used infrared vision to probe dark, dusty, never-before-seen regions of space with the optical clarity that only Hubble can provide. Its infrared detectors operated at a very cold temperature (minus 351 degrees Fahrenheit, which is minus 213 degrees Celsius or 60 Kelvin).

To keep the detectors cold, NICMOS was encased in a thermos-like container filled with solid nitrogen ice. It was expected that the solid nitrogen ice would last approximately four years. However, the ice evaporated about twice as fast as planned and was depleted after only 23 months of NICMOS science operations. In 1999 ? with its supply of ice exhausted ? NICMOS became dormant.

Determined not to be defeated, NASA scientists and engineers devised a plan to restore NICMOS to life. They turned to a new mechanical cooling technology, jointly developed by NASA and the U.S. Air Force. The NICMOS Cooling System (NCS) was built by NASA’s Goddard Space Flight Center, Greenbelt, MD, and the Creare Corporation, Hanover, NH.

The mechanical cooler operates on principles similar to a modern home refrigerator. It pumps ultra-cold neon gas through the internal plumbing of the instrument. At its core are three miniature, high-tech turbines that spin at rates up to about 430,000 rpm. Since the speed of the turbines can be adjusted at will, the NICMOS light sensors can be operated at a more optimal temperature than was possible before, about 77 Kelvin (minus 321 degrees Fahrenheit).

The NICMOS cooling system is virtually vibration-free, an important aspect for Hubble since vibrations can affect image quality in much the same way that a shaky camera produces blurred pictures.

“The Hubble Space Telescope Servicing Mission 3B is now demonstrated to be a complete success. We had 100 percent servicing mission success, and now we have 100 percent performance success for the newly installed NICMOS Cooling System,” said Dr. Ed Cheng, HST Development Project Scientist from NASA’s Goddard Space Flight Center.

Astronauts installed the NCS inside Hubble during the fifth and final spacewalk of Servicing Mission 3B on March 8, 2002. On March 18, the NCS was turned on via commands sent from the Space Telescope Operations Control Center at Goddard. It has continued to operate flawlessly ever since. The deep interior of the NICMOS reached the target temperature of 70 Kelvin (minus 333 degrees Fahrenheit) on April 11. Most of the internal heat had been removed from the instrument, and the NCS stabilized itself at this temperature. On April 19, NICMOS was brought up to a fully operational state and testing of its internal condition began. Since then, fine adjustments have been made to the settings of the NCS to optimize the instrument for best performance.

Original Source: Hubble News Release

Image credit: Hubble

A new photograph taken by the Hubble Space Telescope shows a nebula formed around a group of young, hot, stars. Designated N44C, the nebula is located in the Large Magellanic Cloud, a nearby, small companion galaxy to the Milky Way. It’s peculiar because the star located at the centre of the nebula is inexplicably hot – it could be that the star has a black hole or neutron star companion.

Resembling the hair in Botticelli’s famous portrait of the birth of Venus, softly glowing filaments stream from a complex of hot young stars. This image of a nebula, known as N44C, comes from the archives of NASA’s Hubble Space Telescope (HST). It was taken with the Wide Field Planetary Camera 2 in 1996 and is being presented by the Hubble Heritage Project.

N44C is the designation for a region of glowing hydrogen gas surrounding an association of young stars in the Large Magellanic Cloud, a nearby, small companion galaxy to the Milky Way visible from the Southern Hemisphere.

N44C is peculiar because the star mainly responsible for illuminating the nebula is unusually hot. The most massive stars, ranging from 10-50 times more massive than the Sun, have maximum temperatures of 54,000 to 90,000 degrees Fahrenheit (30,000 to 50,000 degrees Kelvin). The star illuminating N44C appears to be significantly hotter, with a temperature of about 135,000 degrees Fahrenheit (75,000 degrees Kelvin)!

Ideas proposed to explain this unusually high temperature include the possibility of a neutron star or black hole that intermittently produces X-rays but is now “switched off.”

On the top right of this Hubble image is a network of nebulous filaments that inspired comparison to Botticelli. The filaments surround a Wolf-Rayet star, another kind of rare star characterized by an exceptionally vigorous “wind” of charged particles. The shock of the wind colliding with the surrounding gas causes the gas to glow.

N44C is part of the larger N44 complex, which includes young, hot, massive stars, nebulae, and a “superbubble” blown out by multiple supernova explosions. Part of the superbubble is seen in red at the very bottom left of the HST image.

The data were taken in November 1996 with Hubble’s Wide Field Planetary Camera 2 by Donald Garnett (University of Arizona) and collaborators and stored in the Hubble archive. The image was composed by the Hubble Heritage Team (STScI/AURA).

Original Source: Hubble News Release

Image credit: Hubble

NASA provided the first pictures today from the newly refurbished Hubble Space Telescope. Among the four new images unveiled to the public today included colliding galaxies, and several nebulas. The Advanced Cameral for Surveys was installed by the crew of the space shuttle Atlantis just a few months ago, and seems to be working well. Operators expect it will be ten times more efficient than the observatory’s previous camera – so far, so good.

“Remarkable, breathtaking” are words jubilant astronomers are using to describe the first four views of the universe taken by the Hubble Space Telescope’s new Advanced Camera for Surveys, released by NASA today.

The new camera was installed on Hubble by astronauts during a shuttle mission last March, the fourth Hubble Space Telescope servicing mission. During five of the most challenging spacewalks ever attempted, the crew successfully upgraded the orbiting telescope with the new camera, a new power unit, new solar arrays and an experimental cooling unit for an infrared camera. Hubble managers say the orbiting telescope has been operating superbly since the servicing mission.

“Today marks the beginning of a new era of exploration with Hubble,” said Dr. Ed Weiler, Associate Administrator for Space Science at NASA Headquarters, Washington. “Our team of scientists and engineers on the ground and the astronauts in space once again did the impossible. After 12 years in space, Hubble not only was given a major overhaul, its new camera has already shown us that, even after 12 years of great science and astounding images, we haven’t seen anything yet.”

Among the suite of four “suitable-for-framing” Advanced Camera for Surveys (ACS) science-demonstration pictures released today is a stunning view of a colliding galaxy, dubbed the “Tadpole,” located 420 million light-years away. Unlike textbook images of stately galaxies, the “Tadpole” ? with a long tail of stars ? captures the essence of a dynamic, restless and violent universe, looking like a runaway pinwheel firework.

“The ACS is opening a wide new window onto the universe. These are among the best images of the distant universe humans have ever seen,” said astronomer Holland Ford of Johns Hopkins University in Baltimore, lead scientist in the camera’s seven-year development.

The camera’s tenfold increase in efficiency will open up much anticipated new capability for discovery. “ACS will allow us to push back the frontier of the early universe. We will be able to enter the ‘twilight zone’ period when galaxies were just beginning to form out of the blackness following the cooling of the universe from the big bang,” said Ford.

The ACS is a camera of superlatives. It is expected to surpass the sensitivity of the largest ground-based telescope to eventually see the very faintest objects ever recorded. The camera delivers a panoramic crispness comparable to that of a wide-screen movie, containing 16 million picture elements (megapixels) per image. By comparison, digital photos from typical consumer cameras are 2 to 4 megapixels.

The ACS image of the Tadpole illustrates the dramatic gains over the Wide Field Planetary Camera 2 resulting from doubling the area and resolution, and demonstrates a five- fold improvement in sensitivity. An unexpected bonus is the enormous number of galaxies in the new Hubble image beyond the Tadpole galaxy, giving it an appearance like the galaxy- filled Hubble Deep Field (HDF) image, taken in 1995. However, the ACS picture was taken in one-twelfth the time it took for the original HDF. Like the Hubble Deep Field, the ACS galaxies contain myriad shapes that are snapshots of galaxies throughout the universe’s 13 billion-year evolution. The ACS images are so sharp astronomers can identify “building blocks” of galaxies, colliding galaxies and extremely distant galaxies in the field ? an exquisite sampler of galaxies.

“The ACS will let us obtain the deepest image of the universe for the foreseeable future,” added astronomer Garth Illingworth of the University of California, Lick Observatory, Santa Cruz, the deputy leader for the camera team.

The other pictures include a stunning collision between two spiral galaxies, dubbed “the Mice,” that presage what might happen to our own Milky Way several billion years in the future when it collides with the neighboring galaxy in the constellation Andromeda. Computer simulations, made by Joshua Barnes of the University of Hawaii and John Hibbard of the National Radio Astronomy Observatory, show that we are seeing the collision of the Mice approximately 160 million years after their closest encounter. Running the simulations forward in time shows that the two galaxies will eventually merge. A similar fate may await the Milky Way and the Andromeda galaxy.

Looking closer to home, ACS imaged the “Cone Nebula,” a craggy-looking mountaintop of cold gas and dust that is a cousin to Hubble’s iconic “pillars of creation” in the Eagle Nebula, photographed in 1995.

Peering into a celestial maternity ward called the M17 Swan Nebula, the ACS revealed a watercolor fantasy-world tapestry of vivid colors and glowing ridges of gas. Embedded in this crucible of star creation are embryonic planetary systems.

In addition to the ACS, spacewalking astronauts installed a new high-tech mechanical “refrigerator” on Hubble during the servicing mission. This “cryocooler” has successfully pumped most of the heat out of the interior of the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), achieving and maintaining to within a few hundredths of one degree the target temperature for neon gas passing through the instrument of 70 degrees Kelvin (minus 203 degrees Centigrade or minus 333 degrees Fahrenheit).

Engineers are now in the process of checking out the operation of the resuscitated NICMOS instrument. By early June, scientists expect to release the first astronomical images taken with the NICMOS since 1998, when it was still being cooled by a rapidly depleting block of solid nitrogen ice.

The new rigid solar arrays, working with the new Power Control Unit, are generating 27 percent more electrical power than the previous arrays. This doubles the electrical power that can be allocated to the scientific instruments on Hubble. The new reaction wheel is operating normally. Nearly a month ago, the Space Telescope Imaging Spectrograph and the Wide Field and Planetary Camera 2 resumed science observations.

“This servicing mission has turned out to be an extraordinary success,” said Preston Burch, Hubble Project Manager at NASA’s Goddard Space Flight Center in Greenbelt, Md. “It was the most difficult and complicated Hubble servicing mission attempted to date and our observatory came through it with flying colors.”

Image credit: Hubble

Thanks to the Hubble Space Telescope, astronomers are using ancient stars in the Milky Way to come up with an independent estimate about the age of the Universe. In the past, astronomers have calculated this age using its rate of expansion, and pegged it between 13-14 billion years old. Under this new method, the astronomers targeted ancient white dwarf stars which cool down at a very predictable rate. These stars were formed near the beginning of the Universe, and the astronomers were able to estimate that they are between 12-13 billion years old. Close enough.

Pushing the limits of its powerful vision, NASA’s Hubble Space Telescope has uncovered the oldest burned-out stars in our Milky Way Galaxy. These extremely old, dim “clockwork stars” provide a completely independent reading on the age of the universe without relying on measurements of the expansion of the universe.

The ancient white dwarf stars, as seen by Hubble, turn out to be 12 to 13 billion years old. Because earlier Hubble observations show that the first stars formed less than 1 billion years after the universe’s birth in the big bang, finding the oldest stars puts astronomers well within arm’s reach of calculating the absolute age of the universe.

Though previous Hubble research sets the age of the universe at 13 to 14 billion years based on the rate of expansion of space, the universe’s birthday is such a fundamental and profound value that astronomers have long sought other age-dating techniques to cross-check their conclusions. “This new observation short-circuits getting to the age question, and offers a completely independent way of pinning down that value,” says Harvey Richer of the University of British Columbia, Canada.

The new age-dating observations were done by Richer and colleagues by using Hubble to go hunting for elusive ancient stars hidden inside a globular star cluster located 5,600 light-years away in the constellation Scorpius. The results are to be published in the Astrophysical Journal Letters.

Conceptually, the new age-dating observation is as elegantly simple as estimating how long ago a campfire was burning by measuring the temperature of the smoldering coals. For Hubble, the “coals” are white dwarf stars, the burned out remnants of the earliest stars that formed in our galaxy.

Hot, dense spheres of carbon “ash” left behind by the long-dead star’s nuclear furnace, white dwarfs cool down at a predictable rate ? the older the dwarf, the cooler it is, making it a perfect “clock” that has been ticking for almost as long as the universe has existed.

This approach has been recognized as more reliable than age-dating the oldest stars still burning by nuclear fusion, which relies on complex models and calculations about how a star burns its nuclear fuel and ages. White dwarfs are easier to age-date because they are simply cooling, but the trick has always been finding the dimmest and hence longest-running “clocks.”

As white dwarfs cool they grow fainter, and this required that Hubble take many snapshots of the ancient globular star cluster M4. The observations amounted to nearly eight days of exposure time over a 67-day period. This allowed for even fainter dwarfs to become visible, until at last the coolest ? and oldest ? dwarfs were seen. These stars are so feeble (at 30th magnitude ? which is considerably fainter than originally anticipated for any Hubble telescope imaging with the original cameras), they are less than one-billionth the apparent brightness of the faintest stars that can be seen by the naked eye.

Globular clusters are the first pioneer settlers of the Milky Way. Many coalesced to build the hub of our galaxy and formed billions of years before the appearance of the Milky Way’s magnificent pinwheel disk (as further confirmed by Richer’s observations). Today 150 globular clusters survive in the galactic halo. The globular cluster M4 was selected because it is the nearest to Earth, so the intrinsically feeblest white dwarfs are still apparently bright enough to be picked out by Hubble.

In 1928, Edwin Hubble’s measurements of galaxies made him realize that the universe was uniformly expanding, which meant the universe had a finite age that could be estimated by mathematically “running the expansion backward.” Edwin Hubble first estimated the universe was only 2 billion years old. Uncertainties over the true expansion rate led to a spirited debate in the late 1970s, with estimates ranging from 8 billion to 18 billion years. Estimates of the ages of the oldest normal “main-sequence” stars were at odds with the lower value, since stars could not be older than the universe itself.

In 1997 Hubble astronomers broke this impasse by triumphantly announcing a reliable age for the universe, calculated from a very precise measurement of the expansion rate. The picture soon got more complicated when astronomers using Hubble and ground-based observatories discovered the universe was not expanding at a constant rate, but accelerating due to an unknown repulsive force termed “dark energy.” When dark energy is factored into the universe’s expansion history, astronomers arrive at an age for the universe of 13-14 billion years. This age is now independently verified by the ages of the “clockwork” white dwarfs measured by Hubble.

Original Source: Hubble News Release

Image credit: NASA

The Hubble Space Telescope’s latest task is to track down elusive Pluto-like objects that lurk at the very edge of our Solar System – many of which seem to travel in pairs like Pluto and its moon Charon. These objects are classified as Kuiper Belt Objects (KBO) and can be found in a vast belt past Neptune. So far, 1% of KBOs have been found to be binary systems, a fact which puzzles astronomers.

NASA’s Hubble Space Telescope is hot on the trail of an intriguing new class of solar system object that might be called a Pluto “mini-me” ? dim and fleeting objects that travel in pairs in the frigid, mysterious outer realm of the solar system called the Kuiper Belt.

In results published today in the journal Nature, a team of astronomers led by Christian Veillet of the Canada-France-Hawaii Telescope Corporation (CFHT) in Kamuela, Hawaii, is reporting the most detailed observations yet of the Kuiper Belt object (KBO) 1998 WW31, which was discovered four years ago and found to be a binary last year by the CFHT.

Pluto and its moon Charon and countless icy bodies known as KBOs inhabit a vast region of space called the Kuiper Belt. This ‘junkyard’ of material left over from the solar system’s formation extends from the orbit of Neptune out to 100 times as far as the Earth is from the Sun (which is about 93 million miles) and is the source of at least half of the short-period comets that whiz through our solar system. Only recently have astronomers found that a small percentage of KBOs are actually two objects orbiting around each other, called binaries.

“More than one percent of the approximately 500 known KBOs are indeed binary: a puzzling fact for which many explanations will be proposed in what is going to be a very exciting and rapidly evolving field of research in the coming years,” says Veillet.

Hubble was able to measure the total mass of the pair based on their mutual 570-day orbit (a technique Isaac Newton used 400 years ago to estimate the mass of our Moon). The ‘odd-couple’ 1998 WW31 together are about 5,000 (0.0002) times less massive than Pluto and Charon.

Like a pair of waltzing skaters, the binary KBOs pivot around a common center of gravity. The orbit of 1998 WW31 is the most eccentric ever measured for any binary solar system object or planetary satellite. Its orbital distance varies by a factor of ten, from 2,500 to 25,000 miles (4,000 to 40,000 kilometers). It is difficult to determine how KBOs wind up traveling in pairs. They may have formed that way, born like twins, or may be produced by collisions where a single body is split in two.

Ever since the first KBO was discovered in 1992, astronomers have wondered how many KBOs may be binaries, but it was generally assumed that the observations would be too difficult for most telescopes. However, the insights to be gained from study of binary KBOs would be significant: measuring binary orbits provide estimates of KBO masses, and mutual eclipses of the binary allow astronomers to determine individual sizes and densities. Assuming some fraction of KBOs should be binary – just as has been discovered in the asteroid belt – astronomers eventually began to search for gravitationally entwined pairs of KBOs.

Then, finally, exactly a year ago on April 16, 2001, Veillet and collaborators announced the first discovery of a binary KBO: 1998 WW31. Since then, astronomers have reported the discoveries of six more binary KBOs. “It’s amazing that something that seems so hard to do and takes many years to accomplish can then trigger an avalanche of discoveries,” says Veillet. Four of those discoveries were made with the Hubble Space Telescope: two were discovered with a program led by Michael Brown of the California Institute of Technology in Pasadena, CA, and two more with a program led by Keith Noll of the Space Telescope Science Institute in Baltimore, MD. The sensitivity and resolution of Hubble is ideal for studying binary KBOs because the objects are so faint and so close together.

The Kuiper Belt is one of the last big missing puzzle pieces to understanding the origin and evolution of our solar system and planetary systems around other stars. Dust disks seen around other stars could be replenished by collisions among Kuiper Belt-type objects, which seems to be common among stars. These collisions offer fundamental clues to the birth of planetary systems.

Original Source: Hubble News Release

After three weeks of tests, NASA controllers have given the newly upgraded Hubble Space Telescope a clean bill of health. Initial tests are largely complete; however, calibrations of the observatory’s instruments are expected to continue for another two months. Routine science observations have now resumed using the telescope’s Imaging Spectrograph and the Wide Field and Planetary Camera 2.

After three weeks of in-orbit checkout, following its deployment from Space Shuttle Columbia on March 9, the Hubble Space Telescope has been declared healthy and fit by engineers and scientists at NASA’s Goddard Space Flight Center in Greenbelt, Md., and the Space Telescope Science Institute in Baltimore.

Initial checkout of the spacecraft and instruments has largely been completed. However, the calibration process for the instruments will continue for another two months. The new rigid solar arrays, coupled with the new Power Control Unit, are working perfectly, generating 27 percent more electrical power than the old arrays. This increase in power roughly doubles the power available to the scientific instruments. The new reaction wheel is operating normally.

The powerful new Advanced Camera for Surveys (ACS) is now undergoing its final optical alignment and focus checks. The image quality of individual stars observed in a standard calibration field is excellent. The Advanced Camera’s light-sensing detectors are also working very well. It is anticipated that the first Early Release Observations of astronomical targets taken with the Advanced Camera for Surveys will be available around the first week in May.

The new, high-tech mechanical cooler inserted by the Astronauts during SM3B has been working continuously and properly since March 18. The cooler?s intended purpose is to attempt to resuscitate the dormant Near-Infrared Camera and Multi-Object Spectrometer (NICMOS), which depleted its expendable solid nitrogen coolant in January 1999. Although this new ?refrigerator?, dubbed the NICMOS Cooling System (NCS), has been reliably generating the amount of cooling power expected, Hubble engineers report that the NICMOS instrument is cooling down more slowly than originally expected. Because it will take longer to reach the proper operating temperature, below approximately 80 degrees Kelvin, the initial checkout and scientific observations with NICMOS will be delayed for several weeks.

Routine science observations have now resumed with the Space Telescope Imaging Spectrograph and the Wide Field and Planetary Camera 2, the two instruments that were operating on Hubble prior to Servicing Mission 3B. On another note, a gyro (Gyro 3) that had not been performing as well as it should prior to the mission resumed perfect operation after it was turned off and re-started while Hubble was in Columbia’s payload bay.

The Space Shuttle Columbia journeyed to the Hubble Space Telescope for the fourth servicing mission on March 1, 2002. During a series of five spacewalks, Astronauts installed new hardware and upgraded older systems, leaving the telescope better than ever. After a successful mission spanning 11 days in orbit, the shuttle landed safely on March 12 at Kennedy Space Center, Fla.

Original Source: NASA News Release