Universe Today

Image credit: UH IfA

Astronomers from the University of Hawaii’s Institute for Astronomy released new images from their brand new 16-megapixel camera installed on the 2.2 metre telescope on Mauna Kea. This new camera provides a tremendous increase in resolution over the 1-megapixel camera the telescope was using before, and makes this telescope one of the most powerful on Earth for Infrared astronomy. The newly-released image is of galaxy NGC 891, which is 10 million light-years away in the constellation of Andromeda.

Astronomers from the University of Hawaii (UH), Institute for Astronomy (IfA) today released the first image from a gigantic new 16 Megapixel infrared camera recently mounted on the UH 2.2-meter (88-inch) Telescope on Mauna Kea. The new camera provides a sixteen-fold increase in sky coverage together with much higher sensitivity than the 1-Megapixel cameras in widespread use on telescopes for the last decade. Until larger telescopes have similar cameras, it makes the 30-year-old UH 2.2-meter telescope the most powerful in the world for infrared imaging.

The development of this new technology has been driven by the requirements of NASA’s James Webb Space Telescope (JWST), the next step beyond the Hubble Space Telescope and planned for launch within ten years. This 6 meter class space telescope with six times the collecting area of Hubble will be launched into an orbit far beyond the moon where it will cool to temperatures of -400 degrees Fahrenheit, allowing extremely sensitive infrared observations. NASA has selected the UH/RSC (Rockwell Scientific Company) detector technology for the camera on JWST and is expected to adopt it for several other instruments.

Funded by a nearly $7 million award from NASA Ames Research Center, a team at the IfA Hilo facility headed up by Dr. Don Hall, former IfA director, has partnered with the Rockwell Scientific Company in Camarillo, CA, in a four year program to develop 4 Megapixel chips utilizing new infrared detector materials and state of the art silicon chips which, at a size of nearly 2″ x 2″, are some of the largest ever produced. In partnership with GL Scientific, a Honolulu small business, the team has innovated a new approach to mounting the individual 4 Megapixel chips so that four of them can be “tiled” into a 16 Megapixel camera. This approach allows for even larger “mosaic” cameras in the future.

Hall emphasized that the project was run from Hilo. “The IfA team provided technical direction of both the development effort at Rockwell Scientific and the silicon chip fabrication at the UMC foundry in Taiwan,” he said. “In addition, we have established in Hilo a facility to test these new detectors that is widely regarded as the best available”. Hall also commented “complex instruments like this camera usually require extensive de-bugging once they are mounted at the telescope. It is a tribute to the technical excellence of the IfA staff and the superb equipment at the IfA facility that this camera produced science data on its first night”.

The galaxy imaged, NGC 891, is in the constellation Andromeda at a distance of about 10 million light years. It is of particular scientific interest because it is very similar to our own Milky Way Galaxy but is seen almost exactly edge-on. Dr. Richard Wainscoat and Peter Capak, who are analyzing the image, emphasized the importance of being able to image the entire galaxy in a single exposure with the new camera. “With smaller cameras, galaxies such as NGC 891 had to be imaged in small postage stamp sized pieces that had to be painstakingly pieced together – the new camera produces a better image in a tiny fraction of the time,” Wainscoat said. “By allowing us to image very large areas of the sky, this camera will allow us to detect some of the most distant galaxies in the Universe”.

Along with the JWST, large ground based telescopes are already racing to take advantage of this new technology. Two Mauna Kea projects, the Canada-France-Hawaii Telescope and the Gemini Telescopes, are forging ahead with 16 Megapixel infrared cameras and Rockwell Scientific has orders for several other cameras for telescopes in Chile.

IfA Director Dr. Rolf Kudritzki said “This project is an excellent example of IfA’s nurturing of extremely high-tech projects in its Hilo facility and there is an institutional commitment to continued support of such activities. It is particularly gratifying that a number of the key personnel on this project grew up in Hilo and were recruited back from the Mainland and that several others were recruited directly as graduates of UH Hilo. The project also provided important training for undergraduate assistants from UH Hilo, many of whom have gone on to positions in related fields”.

The Institute for Astronomy at the University of Hawaii conducts research into galaxies, cosmology, stars, planets, and the Sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Mauna Kea. Refer to http://www.ifa.hawaii.edu/ for more information about the Institute.

Original Source: IFA News Release

Image credit: ESO

The European Southern Observatory has released new images of nebula N44 in the Large Magellanic Cloud. Astronomers used the ESO’s Wide-Field-Imager on the 2.2 metre La Silla Observatory to capture the area with unprecedented clarity. N44 is approximately 1,000 light-years across and contains about 40 bright luminous blue stars. The blue stars live for a very short time and then explode as supernovae – some have already exploded in the area, creating some of the nebula’s visible material.

The two best known satellite galaxies of the Milky Way, the Magellanic Clouds, are located in the southern sky at a distance of about 170,000 light-years. They host many giant nebular complexes with very hot and luminous stars whose intense ultraviolet radiation causes the surrounding interstellar gas to glow.

The intricate and colourful nebulae are produced by ionised gas [1] that shines as electrons and positively charged atomic nuclei recombine, emitting a cascade of photons at well defined wavelengths. Such nebulae are called “H II regions”, signifying ionised hydrogen, i.e. hydrogen atoms that have lost one electron (protons). Their spectra are characterized by emission lines whose relative intensities carry useful information about the composition of the emitting gas, its temperature, as well as the mechanisms that cause the ionisation. Since the wavelengths of these spectral lines correspond to different colours, these alone are already very informative about the physical conditions of the gas.

N44 [2] in the Large Magellanic Cloud is a spectacular example of such a giant H II region. Having observed it in 1999 (see ESO PR Photos 26a-d/99), a team of European astronomers [3] again used the Wide-Field-Imager (WFI) at the MPG/ESO 2.2-m telescope of the La Silla Observatory, pointing this 67-million pixel digital camera to the same sky region in order to provide another striking – and scientifically extremely rich – image of this complex of nebulae. With a size of roughly 1,000 light-years, the peculiar shape of N44 clearly outlines a ring that includes a bright stellar association of about 40 very luminous and bluish stars.

These stars are the origin of powerful “stellar winds” that blow away the surrounding gas, piling it up and creating gigantic interstellar bubbles. Such massive stars end their lives as exploding supernovae that expel their outer layers at high speeds, typically about 10,000 km/sec.

It is quite likely that some supernovae have already exploded in N44 during the past few million years, thereby “sweeping” away the surrounding gas. Smaller bubbles, filaments, bright knots, and other structures in the gas together testify to the extremely complex structures in this region, kept in continuous motion by the fast outflows from the most massive stars in the area.
The new WFI image of N44

The colours reproduced in the new image of N44, shown in PR Photo 31a/03 (with smaller fields in more detail in PR Photos 31b-e/03) sample three strong spectral emission lines. The blue colour is mainly contributed by emission from singly-ionised oxygen atoms (shining at the ultraviolet wavelength 372.7 nm), while the green colour comes from doubly-ionised oxygen atoms (wavelength 500.7 nm). The red colour is due to the H-alpha line of hydrogen (wavelength 656.2 nm), emitted when protons and electrons combine to form hydrogen atoms. The red colour therefore traces the extremely complex distribution of ionised hydrogen within the nebulae while the difference between the blue and the green colour indicates regions of different temperatures: the hotter the gas, the more doubly-ionised oxygen it contains and, hence, the greener the colour is.

The composite photo produced in this way approximates the real colours of the nebula. Most of the region appears with a pinkish colour (a mixture of blue and red) since, under the normal temperature conditions that characterize most of this H II region, the red light emitted in the H-alpha line and the blue light emitted in the line of singly-ionised oxygen are more intense than that emitted in the line of the doubly-ionised oxygen (green).

However, some regions stand out because of their distinctly greener shade and their high brightness. Each of these regions contains at least one extremely hot star with a temperature somewhere between 30,000 and 70,000 degrees. Its intense ultraviolet radiation heats the surrounding gas to a higher temperature, whereby more oxygen atoms are doubly ionised and the emission of green light is correspondingly stronger, cf. PR Photo 31c/03.

Original Source: ESO News Release

Image credit: CNRS

An international team of astronomers have discovered a new galaxy colliding with our own Milky Way. This new galaxy, Canis Major, is located only 42,000 light years away from the centre of the Milky Way – it’s our new “closest galaxy”. Canis Major was discovered during an infrared survey of the sky, which allowed the astronomers to peer through the obscuring dust and gas of the Milky Way. Canis Major is quite small (as galaxies go); it only contains about a billion stars.

An international team of astronomers from France, Italy, the UK and Australia has found a previously unknown galaxy colliding with our own Milky Way. This newly-discovered galaxy takes the record for the nearest galaxy to the centre of the Milky Way. Called the Canis Major dwarf galaxy after the constellation in which it lies, it is about 25000 light years away from thesolar system and 42000 light years from the centre of the Milky Way. This i closer than the Sagittarius dwarf galaxy, discovered in 1994, which is also colliding with the Milky Way. The discovery shows that the Milky Way is building up its own disk by absorbing small satellite galaxies. The research is to be published in the Monthly Notices of the Royal Astronomical Society within the next few weeks.

The discovery of the Canis Major dwarf was made possible by a recent survey of the sky in infrared light (the Two-Micron All Sky Survey or “2MASS”), which has allowed astronomers to look beyond the clouds of dust in the disk of the Milky Way. Until now, the dwarf galaxy lay undetected behind the dense disk. “It’s like putting on infrared night-vision goggles,” says team-member Dr Rodrigo Ibata of Strasbourg Observatory. “We are now able to study a part of the Milky Way that has been previously out of sight”.

The new dwarf galaxy was detected by its M-giant stars =AD cool, red stars that shine especially brightly in infrared light. “We have used these rare M-giant stars as beacons to trace out the shape and location of the new galaxy because its numerous other stars are too faint for us to see,” explains Nicolas Martin, also of Strasbourg Observatory. “They are particularly useful stars as we can measure their distances, and so map out the three-dimensional structure of distant regions of the Milky Way disk.” In this way, the astronomers found the main dismembered corpse of the dwarf galaxy in Canis Major and long trails of stars leading back to it. It seems that streams of stars pulled out of the cannibalised Canis Major galaxy not only contribute to the outer reaches of the Milky Way’s disk, but may also pass close to the Sun.

Astronomers currently believe that large galaxies like the Milky Way grew to their present majestic proportions by consuming their smaller galactic neighbours. They have found that cannibalised galaxies add stars to the vast haloes around large galaxies. However, until now, they did not appreciate that even the disks of galaxies can grow in this fashion. Computer simulations show that the Milky Way has been taking stars from the Canis Major dwarf and adding them to its own disk – and will continue to do so.

“On galactic scales, the Canis Major dwarf galaxy is a lightweight of about only one billion Suns,” said Dr. Michele Bellazzini of Bologna Observatory. “This small galaxy is unlikely to hold together much longer. It is being pushed and pulled by the colossal gravity of our Milky Way, which has been progressively stealing its stars and pulling it apart.” Some remnants of the Canis Major dwarf form a ring around the disk of the Milky Way.

“The Canis Major dwarf galaxy may have added up to 1% more mass to our Galaxy,” said Dr Geraint Lewis of the University of Sydney. “This is also an important discovery because it highlights that the Milky Way is not in its middle age – it is still forming.” “Past interactions of the sort we are seeing here could be responsible for some of the exquisite detail we see today in the structure of the Galaxy,” says Dr Michael Irwin of the University of Cambridge.

Original Source: RAS News Release

Image credit: NASA/JPL

The Sun ejected two massive flares towards the Earth last week, and NASA’s Cassini spacecraft listened in on the burst of radio waves that accompanied them. The radio waves took 69 minutes to reach Cassini, moving at the speed of light, and they sound a bit like the whoosh of a jet engine. The blast of radio waves was one of the largest ever recorded – a type 3 event. Cassini is on track to reach Saturn on July 1, 2004.

University of Iowa Professor and Space Physicist Dr. Don Gurnett used NASA’s Cassini spacecraft to record the sound of one of the largest solar flares seen in decades, as it moved outward from the Sun.

The sound can be heard online at: http://www-pw.physics.uiowa.edu/space-audio/.

NASA’s Solar and Heliospheric Observatory (SOHO) spacecraft captured this image of a solar flare, seen in the lower center of the image, as it erupted from the Sun early on Tuesday, October 28, 2003.

The radio wave burst, resembling the clicking of an old-fashioned telegraph machine followed by the rush of a jet engine, was recorded Oct. 28 by Cassini while on its way to a July 1, 2004, encounter with Saturn. Cassini will be the first orbiter to give us a close-up look at the ringed world and its moons. Its piggybacked Huygens probe, contributed by the European Space Agency, will descend through the smoggy atmosphere of Saturn’s moon Titan, impacting on what could be a liquid methane ocean.

Gurnett noted that the radio waves — moving at the speed of light — took just 69 minutes to reach the spacecraft, currently some 1.3 billion kilometers (809 million miles) from Earth.

“This is one of the biggest events of its kind ever seen,” said Gurnett. The event, described as a “type 3” radio burst, was detected using the Cassini radio and plasma wave instrument, largely built at the University of Iowa, and for which Gurnett serves as principal investigator.

“The sound is produced by electrons moving out from the solar flare, beginning at a high frequency before dropping to a lower frequency,” Gurnett said. Scientists monitoring the solar flare said that the massive cloud — composed of billions of tons of electrically charged particles — reached Earth on Oct. 29.

Cassini-Huygens is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech, manages the mission for NASA’s Office of Space Science, Washington, D.C.

Original Source: NASA/JPL News Release