Subaru Telescope has added another dimension of information about one of the most studied of all compact galaxy groups—Stephan’s Quintet. Located within the borders of the constellation Pegasus, Stephan’s Quintet consists of a visual grouping of five galaxies, four of which form an actual compact group of galaxies; one additional galaxy appears in images of the group but is much closer than the others. Refinements in observations of the quintet are revealing more about its members. A comparison of images (the left and right images in Figure 1) compiled by using a suite of specialized filters with Subaru’s Prime Focus Camera (Suprime-Cam) have shown different types of star-formation activity between the closer galaxy NGC7320 and the more distant galaxies in Stephan’s Quintet. They show the quintet in 3-D.
These new images are the product of Suprime-Cam’s ability to capture images of objects in a wide field of view and to use specialized filters to focus observations according to particular research objectives. To learn about the star-forming regions in Stephan’s Quintet and their structures, observers used special narrowband filters for Hα emissions, which let in a very specific wavelength of light to indicate distinctive hydrogen emissions during active star formation. They used two Hα filters, each with a different recession velocity, i.e. the speed at which the object is moving away from the observer. They used one Hα filter with a recession velocity of 0, which means that the speed at which the object is moving away from the observer is 0 and that it is not far distant. They used another Hα filter with a greater recession velocity of 4200 miles (6,700 km) per second, an indicator of distant objects. In addition to the red color attributed to the Hα emission, blue and green colors assigned to the images from the blue and red filters captured light so that the composite tricolor images aligned with human color perception in red, green, and blue.
ESA’s Rosetta spacecraft has revealed asteroid Lutetia to be a primitive body, left over as the planets were forming in our Solar System. Results from Rosetta’s fleeting flyby also suggest that this mini-world tried to grow a metal heart.
Rosetta flew past Lutetia on 10 July 2010 at a speed of 54 000 km/hr and a closest distance of 3170 km. At the time, the 130 km-long asteroid was the largest encountered by a spacecraft. Since then, scientists have been analysing the data taken during the brief encounter.
All previous flybys went past objects, which were fragments of once-larger bodies. However, during the encounter, scientists speculated that Lutetia might be an older, primitive ‘mini-world’.
In today’s issue of the journal Nature, astronomers report that organic compounds of unexpected complexity exist throughout the Universe. The results suggest that complex organic compounds are not the sole domain of life but can be made naturally by stars.
Prof. Sun Kwok and Dr. Yong Zhang of The University of Hong Kong show that an organic substance commonly found throughout the Universe contains a mixture of aromatic (ring-like) and aliphatic (chain-like) components. The compounds are so complex that their chemical structures resemble those of coal and petroleum. Since coal and oil are remnants of ancient life, this type of organic matter was thought to arise only from living organisms. The team’s discovery suggests that complex organic compounds can be synthesized in space even when no life forms are present.
Full Story: http://www.hku.hk/press/news_detail_6633.html
A new analysis of Hubble surveys, combined with simulations of galaxy interactions, reveals that the merger rate of galaxies over the last 8 billion to 9 billion years falls between the previous estimates.
The galaxy merger rate is one of the fundamental measures of galaxy evolution, yielding clues to how galaxies bulked up over time through encounters with other galaxies. And yet, a huge discrepancy exists over how often galaxies coalesced in the past. Earlier measurements of galaxies in deep-field surveys made by NASA’s Hubble Space Telescope generated a broad range of results: anywhere from 5 percent to 25 percent of the galaxies were merging.
The new study, led by Jennifer Lotz of the Space Telescope Science Institute in Baltimore, Md., analyzed galaxy interactions at different distances, allowing the astronomers to compare mergers over time. Lotz’s team found that galaxies gained quite a bit of mass through collisions with other galaxies. Large galaxies merged with each other on average once over the past 9 billion years. Small galaxies were coalescing with large galaxies more frequently. In one of the first measurements of smashups between dwarf and massive galaxies in the distant universe, Lotz’s team found these mergers happened three times more often than encounters between two hefty galaxies.
To visible-light telescopes, this star-forming cloud appears to be chomping through the cosmos, earning it the nickname the “Pacman” nebula, like the famous Pac-Man video game that debuted in 1980. When viewed in infrared light by NASA’s Wide-field Infrared Survey Explorer, or WISE, the Pacman takes on a new appearance. In place of its typical, triangle-shaped mouth is a new set of lower, sharp-looking teeth. The Pacman is located at the top of the picture, taking a bite in the direction of the upper left corner.
The teeth are actually pillars where new stars may be forming. These structures were formed when radiation and winds from massive stars in a central cluster blew gas and dust away, leaving only the densest of material. The red dots sprinkled throughout the picture are thought to be the youngest stars, still forming in cocoons of dust.
The Pacman nebula, also called NGC 281, is located 9,200 light years away in the constellation Cassiopeia.
In early November, NASA will seek applicants for its next class of astronaut candidates who will support long-duration missions to the International Space Station and future deep space exploration activities.
“For scientists, engineers and other professionals who have always dreamed of experiencing spaceflight, this is an exciting time to join the astronaut corps,” said Janet Kavandi, director of flight crew operations at the Johnson Space Center in Houston. “This next class will support missions to the station and will arrive via transportation systems now in development. They also will have the opportunity to participate in NASA’s continuing exploration programs that will include missions beyond low Earth orbit.”
NASA scientists will be tracking asteroid 2005 YU55 with antennas of the agency’s Deep Space Network at Goldstone, Calif., as the space rock safely flies past Earth slightly closer than the moon’s orbit on Nov. 8. Scientists are treating the flyby of the 1,300-foot-wide (400-meter) asteroid as a science target of opportunity – allowing instruments on “spacecraft Earth” to scan it during the close pass.
Tracking of the aircraft carrier-sized asteroid will begin at 9:30 a.m. local time (PDT) on Nov. 4, using the massive 70-meter (230-foot) Deep Space Network antenna, and last for about two hours. The asteroid will continue to be tracked by Goldstone for at least four hours each day from Nov. 6 through Nov. 10. Radar observations from the Arecibo Planetary Radar Facility in Puerto Rico will begin on Nov. 8, the same day the asteroid will make its closest approach to Earth at 3:28 p.m. PST.
The trajectory of asteroid 2005 YU55 is well understood. At the point of closest approach, it will be no closer than 201,700 miles (324,600 kilometers) or 0.85 the distance from the moon to Earth. The gravitational influence of the asteroid will have no detectable effect on anything here on Earth, including our planet’s tides or tectonic plates. Although 2005 YU55 is in an orbit that regularly brings it to the vicinity of Earth (and Venus and Mars), the 2011 encounter with Earth is the closest this space rock has come for at least the last 200 years.
Astronomers have accurately measured the diameter of the faraway dwarf planet Eris for the first time by catching it as it passed in front of a faint star. This event was seen at the end of 2010 by telescopes in Chile, including the Belgian TRAPPIST telescope at ESO’s La Silla Observatory. The observations show that Eris is an almost perfect twin of Pluto in size. Eris appears to have a very reflective surface, suggesting that it is uniformly covered in a thin layer of ice, probably a frozen atmosphere. The results will be published in the 27 October 2011 issue of the journal Nature.
In November 2010, the distant dwarf planet Eris passed in front of a faint background star, an event called an occultation. These occurrences are very rare and difficult to observe as the dwarf planet is very distant and small. The next such event involving Eris will not happen until 2013. Occultations provide the most accurate, and often the only, way to measure the shape and size of a distant Solar System body.
The candidate star for the occultation was identified by studying pictures from the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory. The observations were carefully planned and carried out by a team of astronomers from a number of (mainly French, Belgian, Spanish and Brazilian) universities using — among others — the TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope, eso1023) telescope, also at La Silla.
Full Story: http://www.eso.org/public/news/eso1142/