Posted on by Fraser Cain

Meteor Strike on the Moon

The red dot indicates the location of the recent meteoroid impact. Image credit: NASA/MSFC/Bill Cooke. Click to enlarge
NASA scientists have observed an explosion on the moon. The blast, equal in energy to about 70 kg of TNT, occurred near the edge of Mare Imbrium (the Sea of Rains) on Nov. 7, 2005, when a 12-centimeter-wide meteoroid slammed into the ground traveling 27 km/s.

“What a surprise,” says Marshall Space Flight Center (MSFC) researcher Rob Suggs, who recorded the impact’s flash. He and colleague Wes Swift were testing a new telescope and video camera they assembled to monitor the moon for meteor strikes. On their first night out, “we caught one,” says Suggs.

The object that hit the moon was “probably a Taurid,” says MSFC meteor expert Bill Cooke. In other words, it was part of the same meteor shower that peppered Earth with fireballs in late October and early November 2005. (See “Fireball Sightings” from Science@NASA.)

The moon was peppered, too, but unlike Earth, the moon has no atmosphere to intercept meteoroids and turn them into harmless streaks of light. On the moon, meteoroids hit the ground–and explode.

“The flash we saw,” says Suggs, “was about as bright as a 7th magnitude star.” That’s two and a half times dimmer than the faintest star a person can see with their unaided eye, but it was an easy catch for the group’s 10-inch telescope.

Cooke estimates that the impact gouged a crater in the moon’s surface “about 3 meters wide and 0.4 meters deep.” As moon craters go, that’s small. “Even the Hubble Space Telescope couldn’t see it,” notes Cooke. The moon is 384,400 km away. At that distance, the smallest things Hubble can distinguish are about 60 meters wide.

This isn’t the first time meteoroids have been seen hitting the moon. During the Leonid meteor storms of 1999 and 2001, amateur and professional astronomers witnessed at least half-a-dozen flashes ranging in brightness from 7th to 3rd magnitude. Many of the explosions were photographed simultaneously by widely separated observers.

Since the Leonids of 2001, astronomers have not spent much time hunting for lunar meteors. “It’s gone out of fashion,” says Suggs. But with NASA planning to return to the moon by 2018, he says, it’s time to start watching again.

There are many questions that need answering: “How often do big meteoroids strike the moon? Does this happen only during meteor showers like the Leonids and Taurids? Or can we expect strikes throughout the year from ‘sporadic meteors?'” asks Suggs. Explorers on the moon are going to want to know.

“The chance of an astronaut being directly hit by a big meteoroid is miniscule,” says Cooke. Although, he allows, the odds are not well known “because we haven’t done enough observing to gather the data we need to calculate the odds.” Furthermore, while the danger of a direct hit is almost nil for an individual astronaut, it might add up to something appreciable for an entire lunar outpost.

Of greater concern, believes Suggs, is the spray??bf?”the secondary meteoroids produced by the blast.” No one knows how far the spray reaches and exactly what form it takes.

Also, ground-shaking impacts could kick up moondust, possibly over a wide area. Moondust is electrostatically charged and notoriously clingy. (See “Mesmerized by Moondust” from Science@NASA.) Even a small amount of moondust can be a great nuisance: it gets into spacesuit joints and seals, clings to faceplates, and even makes the air smell when it is tramped indoors by moonwalkers. Could meteoroid impacts be a source of lunar “dust storms?” Another question for the future….

Suggs and his team plan to make more observations. “We’re contemplating a long-term monitoring program active not only during major meteor showers, but also at times in between. We need to develop software to find these flashes automatically,” he continues. “Staring at 4 hours of tape to find a split-second flash can get boring; this is a job for a computer.”

With improvements, their system might catch lots of lunar meteors. Says Suggs, “I’m ready for more surprises.”

Original Source: NASA News Release

Posted on by Fraser Cain

Photos of Young Stellar Clusters

NGC 2467 and Surroundings. Image credit: ESO Click to enlarge
Just like Charles Dickens’ Christmas Carol takes us on a journey into past, present and future in the time of only one Christmas Eve, two of ESO’s telescopes captured various stages in the life of a star in a single image.

ESO’s first image shows the area surrounding the stellar cluster NGC 2467, located in the southern constellation of Puppis (“The Stern”). With an age of a few million years at most, it is a very active stellar nursery, where new stars are born continuously from large clouds of dust and gas.

The image, looking like a colourful cosmic ghost or a gigantic celestial Mandrill, contains the open clusters Haffner 18 (centre) and Haffner 19 (middle right: it is located inside the smaller pink region – the lower eye of the Mandrill), as well as vast areas of ionised gas.

The bright star at the centre of the largest pink region on the bottom of the image is HD 64315, a massive young star that is helping shaping the structure of the whole nebular region.

The first image was taken with the Wide-Field Imager camera at the 2.2m MPG/ESO telescope located at La Silla, in Chile.

Another image of the central part of this area is shown in ESO’s second image. It was obtained with the FORS2 instrument at ESO’s Very Large Telescope on Cerro Paranal, also in Chile.

NGC 2467 and Surroundings. Image credit: ESO Click to enlarge
However, the second image zooms in on the open stellar cluster Haffner 18, perfectly illustrating three different stages of this process of star formation: In the centre of the picture, Haffner 18, a group of mature stars that have already dispersed their birth nebulae, represents the completed product or immediate past of the star formation process. Located at the bottom left of this cluster, a very young star, just come into existence and, still surrounded by its birth cocoon of gas, provides insight into the very present of star birth. Finally, the dust clouds towards the right corner of the image are active stellar nurseries that will produce more new stars in the future.

Haffner 18 contains about 50 stars, among which several short lived, massive ones. The massive star still surrounded by a small, dense shell of hydrogen, has the rather cryptic name of FM3060a. The shell is about 2.5 light-years wide and expands at a speed of 20 km/s. It must have been created some 40,000 years ago. The cluster is between 25,000 and 30,000 light-years away from us.

Original Source: ESO News Release

Posted on by Fraser Cain

You Don’t Need an iPod to Listen to Podcasts!

When I mention to people that I record a regular podcast, I often get some kind of response like, “oh, I can’t listen to that, I don’t have an iPod.” Yikes! Podcasts, despite their name, don’t require an iPod, or even a portable MP3 player of any kind. If you like to listen to radio shows, you’ll love podcasting. I’ve written up an explainer to help you get up to speed, and listen to a whole Universe of free audio content – especially my own podcast. 🙂

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Lakebed on Mars Wasn’t So Watery In the Past

Mars seems not to be as wet as it was predicted. Image credit: NASA Click to enlarge
A region of Mars that some planetary scientists believe was once a shallow lakebed and likely habitable for life may not have been so wet after all, according to a new University of Colorado at Boulder study.

The new study indicates chemical signatures in the bedrock, interpreted in 2004 by the Mars Exploration Rover, or MER, mission team as evidence for widespread, intermittent water at Mars’ surface, may have instead been created by the reaction of sulfur-bearing steam vapors moving up through volcanic ash deposits. Known as Meridiani Planum, the region may have been more geologically similar to volcanic regions in parts of North America, Hawaii or Europe, said Thomas McCollom of CU-Boulder’s Center for Astrobiology.

“Our study indicates it was probably more like parts of Yellowstone, Hawaii or Italy than something like the Great Salt Lake,” said McCollom, also a research associate at CU-Boulder’s Laboratory for Atmospheric and Space Physics. “We think it was far less favorable for past biological activity than other scenarios that have been proposed.”

A paper on the subject by McCollom and CU-Boulder Research Associate Brian Hynek of CU-Boulder’s LASP appears in the Dec. 22 issue of Nature.

A series of scientific papers published in December 2004 by the Mars Exploration Rover team and based on data gathered by the rover Opportunity, concluded that the Meridiani Planum region once probably had a large sea or huge lake that may have waxed and waned over eons. The authors proposed that the evaporation of surface and subsurface water over time left behind various chemical precipitates — predominately sulfate salts — which they interpreted as evidence for a watery environment that would have been conducive for life to exist.

But if the sulfate was the result of precipitation from an evaporating brine of surface and subsurface water as has been proposed, McCollom and Hynek contend the bedrock should be enriched with a large amount of positively charged atoms, known as cations, from minerals like iron, calcium and magnesium. But it is not, they said.

“We think the bedrock was laid down by enormous volcanic ash flows over time that were then permeated by sulfur dioxide-rich steam vapors,” said McCollom. “The sulfur dioxide and water combined to form sulfuric acid, which reacted with and altered the bedrock to give it its present chemical composition.”

The new scenario does not require prolonged interaction between bedrock and a standing body of surface water as proposed by the MER team, and the process likely occurred at high temperatures, perhaps more than 200 degrees F, said McCollom. “Everything about the site seems to be consistent with our conclusions,” he said.

“In our scenario, the water required to support the chemistry in this bedrock would only have had to have been around for months, years or perhaps as much as a few centuries,” said Hynek. “This is very different than previous scenarios, which require that a much larger amount of water be present for many millennia.”‘

The European Space Agency’s Mars Express spacecraft recently showed the chemistry of layered deposits surrounding the Meridiani Planum region is similar to the bedrock at the Opportunity landing site, implying the entire area hosted volcanic activity, said Hynek. The size of the suspected Meridiani Planum volcanic deposits appears much larger than any similar deposit on Earth and encompasses an area roughly the size of Arizona, according to the CU-Boulder researchers.

McCollom described the geology of the region as “solfatara-like,”‘ a term that originated from Solfatara Crater, a volcanic region near Naples, Italy, harboring vents that emit vapors. “While solfataras are riddled with vents and fissures giving off sulfurous vapors at the surface, the deposits we see at Meridiani probably represent the subsurface beneath such fissures,” said McCollom.

On Earth, solfataras host microbes that are capable of using sulfur for sustenance, McCollom said. Some of the areas are now under study by astrobiologists looking to characterize extreme environments on Earth that support life.

“My view is that there is a good possibility there is life on Mars, probably in the subsurface,” he said. “We know from examples on Earth that life can exist in extreme places, and Mars seems to have the necessary ingredients for that.”

Hynek said that in the distant past, Meridiani Planum may have had all the necessary ingredients to support organisms like those found in solfataras. “But the unique and probably short-lived nature of the environment suggests it may not be the best place to look for evidence of Martian life today,” he said.

Original Source: CU-Boulder News Release

Posted on by Fraser Cain

Young Stars in the Christmas Tree Cluster

NGC 2264, the Cone Nebula and Christmas Tree Cluster. Image credit: NASA/JPL-Caltech. Click to enlarge
Astronomers using NASA’s Spitzer Space Telescope have given the world a spectacular new picture of a star-forming region called the “Christmas Tree Cluster,” complete with first-ever views of a group of newborn stars still linked to their siblings.

Spitzer’s cameras are very sensitive to the infrared (heat), allowing astronomers to see through the obscuring gas and dust of the star-forming cloud that swaddles infant stars.

The Christmas Tree Cluster, also known as NGC 2264, is a well-studied region in the Monoceros (the Unicorn) constellation. The Christmas Tree Cluster was so named because it looks like a tree in visible light. The nebula is roughly 2,500 light-years away. That is, the nebula emitted the light in the new Spitzer image 2,500 years ago.

For astronomers studying the development of very young stars — stars less than a few million years old — “This region has it all,” said University of Arizona astronomer Erick T. Young.

“We see the dramatic-looking emission of cold gas — clouds that look like thunderheads. We see when the massive molecular cloud breaks up and begins to condense into clumps of stars,” Young said. “And, for the first time, because of Spitzer’s sensitivity, we can see individual stars roughly the size of our sun tightly packed within those clumps.” The cluster of stars is so tightly packed that they must be less than 100,000 years old, he added.

Astronomers are calling this compact collection of bright protostars within the Christmas Tree Cluster the “Snowflake Cluster” because of how they are spaced. The newborn stars are patterned like a single feathery crystal of snow, or geometrically spaced like spokes in a wheel.

The Spitzer observations show that just as theory predicts, the density and temperature of the initial star-forming cloud dictates the spacing between the protostars.

Young is deputy principal investigator for Spitzer’s Multiband Imaging Photometer (MIPS), a UA-built camera that took the longest wavelengths of infrared light used in Christmas Tree Cluster mosaic. Astronomers combined light from MIPS and Spitzer’s Infrared Array Camera (IRAC), developed by the Smithsonian Astrophysical Observatory, in constructing in the picture.

The infant stars appear as pink and red specks in the snowflake cluster that adorns the larger Christmas Tree Cluster in the IRAC and MIPS image. The larger, yellowish spheres are massive stars within the NGC 2264 region. The organic molecules mixed in with dust that surrounds the cluster are illuminated as wisps of green. The blue dots smeared across the image are older Milky Way stars at various distances along the telescope’s line of sight.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA’s Science Mission Directorate. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. JPL is a division of Caltech.

Original Source: UA News Release

Posted on by Fraser Cain

New Rings and Moons Around Uranus

The newly discovered pair of Uranus faint dusty rings. Image credit: NASA Click to enlarge
NASA’s Hubble Space Telescope photographed a new pair of rings around Uranus and two new, small moons orbiting the planet.

The largest ring is twice the diameter of the planet’s previously known rings. The rings are so far from the planet, they are being called Uranus’s “second ring system.” One of the new moons shares its orbit with one of the rings. Analysis of the Hubble data also reveals the orbits of Uranus’s family of inner moons have changed significantly over the past decade.

“The detection of these new interacting rings and moons will help us better understand how planetary systems are formed and sustained, which is of key importance to NASA’s scientific exploration goals,” said Dr. Jennifer Wiseman, program scientist for Hubble at NASA Headquarters.

Since dust orbiting Uranus is expected to be depleted by spiraling away, the planet’s rings must be continually replenished with fresh material. “The new discoveries demonstrate that Uranus has a youthful and dynamic system of rings and moons,” said Mark Showalter of the SETI Institute, Mountainview, California.

Showalter and Jack Lissauer of NASA’s Ames Research Center, Moffet Field, Calif., propose that the outermost ring is replenished by a 12-mile-wide newly discovered moon, named Mab, which they first observed using Hubble in 2003.

Meteoroid impacts continually blast dust off the surface of Mab. The dust then spreads out into a ring around Uranus. Mab’s ring receives a fresh infusion of dust from each impact. Nature keeps the ring supplied with new dust while older dust spirals away or bangs back into the moon.

Showalter and Lissauer have measured numerous changes to the orbits of Uranus’s inner moons since 1994. The moon’s motions were derived from earlier Hubble and Voyager observations. “This appears to be a random or chaotic process, where there is a continual exchange of energy and angular momentum between the moons,” Lissauer said. His calculations predict moons would begin to collide as often as every few million years, which is extraordinarily short compared to the 4.5 billion year age of the Uranian system.

Showalter and Lissauer believe the discovery of the second ring, which orbits closer to the planet than the outer ring, provides further evidence that collisions affect the evolution of the system. This second ring has no visible body to re-supply it with dust. The ring may be a telltale sign of an unseen belt of bodies a few feet to a few miles in size. Showalter proposes that a previous impact to one of Uranus’s moons could have produced the observed debris ring.

Hubble uncovered the rings in August 2004 during a series of 80, four-minute exposures of Uranus. The team later recognized the faint new rings in 24 similar images taken a year earlier. Images from September 2005 reveal the rings even more clearly.

Showalter also found the rings in archival images taken during Voyager 2’s flyby of Uranus in 1986. Uranus’s first nine rings were discovered in 1977 during observations of the planet’s atmosphere. During the Voyager encounters, two other inner rings and 10 moons were discovered. However, no one noticed the outer rings, because they are extremely faint and much farther from the planet than expected. Showalter was able to find them by a careful analysis of nearly 100 Voyager images.

Because the new rings are nearly transparent, they will be easier to see when they tilt edge-on. The new rings will increase in brightness every year as Uranus approaches its equinox, when the sun shines directly over the planet’s equator. When it happens in 2007, all of the rings will be tilted edge-on toward Earth and easier to study. These research data will appear in an upcoming issue of the journal Science.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. The Space Telescope Science Institute in Baltimore conducts Hubble science operations. The Institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc., Washington.

Original Source: NASA News Release

Posted on by Fraser Cain

Titan’s Purple Halo

Titan’s orange globe surrounded with a soft purple haze. Image credit: NASA/JPL/SSI Click to enlarge
With its thick, distended atmosphere, Titan’s orange globe shines softly, encircled by a thin halo of purple light-scattering haze.

Images taken using blue, green and red spectral filters were used to create this enhanced-color view; the color images were combined with an ultraviolet view that makes the high-altitude, detached layer of haze visible. The ultraviolet part of the composite image was given a purplish hue to match the bluish-purple color of the upper atmospheric haze seen in visible light.

Small particles that populate high hazes in Titan’s atmosphere scatter short wavelengths more efficiently than longer visible or infrared wavelengths, so the best possible observations of the detached layer are made in ultraviolet light.

The images in this view were taken by the Cassini narrow-angle camera on May 5, 2005, at a distance of approximately 1.4 million kilometers (900,000 miles) from Titan and at a sun-Titan-spacecraft, or phase, angle of 137 degrees. Image scale is 8 kilometers (5 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release.

Posted on by Fraser Cain

New Imaging Technique Reveals the Moon’s Secrets

Remote-sensing instruments on SMART-1 scan the Moon’s surface. Image credit: ESA Click to enlarge
ESA’s SMART-1 spacecraft has been surveying the Moon’s surface in visible and near-infrared light using a new technique, never before tried in lunar orbit.

For the last few months, the Advanced Moon Imaging Experiment (AMIE) on board SMART-1, has been opening new ground by attempting multi-spectral imaging in the ‘push-broom’ mode. This technique is particularly suited to colour imaging of the lunar surface.

(Note that ‘colour imaging’ here does not mean natural colour, the colour bands of the AMIE filters are in the infrared region and are selected such that the intensity of the iron absorption line can be determined from brightness ratios of the images.)

In this mode, AMIE takes images along a line on the Moon’s surface perpendicular to the ground track of the spacecraft.

It relies on the orbital motion of the spacecraft to reposition it as it records a sequence of images known as an ‘image swath’.

The AMIE camera on board SMART-1 has fixed-mounted filters which see the Moon in different colour bands. The figure shows four consecutive images taken by AMIE from left to right. The fixed filters are indicated by coloured frames.

The images, taken only a few seconds apart, show how the surface is moving through the different filters. The spacecraft is moving over the Moon’s surface at a speed of more than a kilometre per second!

By combining images showing the same feature on the Moon as seen through different filters, colour information can be obtained. This allows to study the mineralogical composition on the lunar surface, which in turn lets scientists deduce details of the formation of our celestial companion.

Whereas the multi-spectral camera aboard the US Clementine mission had constant illumination conditions, SMART-1’s orbit will offer different viewing angles. AMIE’s views correlated with Clementine data of the same lunar areas will allow scientists to better interpret such spectral data.

Original Source: ESA Portal

Posted on by Fraser Cain

Ariane 5 Blasts Off with Two Satellites

Ariane 5 lift off from the Guiana Space Centre. Image credit: ESA Click to enlarge
The second member of Europe’s new generation of weather satellites has successfully been lifted onto orbit, continuing an uninterrupted series of launch successes since 1977.

This ninth Meteosat satellite, developed on behalf of EUMETSAT under the aegis of the European Space Agency, will reinforce EUMETSAT’s capacity to monitor the Earth atmosphere above Europe, Africa, the Middle-East and the Atlantic Ocean.

MSG-2 (2nd flight model of Meteosat Second Generation) was one of the two payloads of Ariane 5’s latest launch. The European launch vehicle lifted off from the Guiana Space Centre, Europe’s spaceport, in Kourou, French Guiana, at 19:33 local time on 21 December (23:33 CET).

The Ariane 5GS vehicle successfully delivered its two passenger payloads onto a near perfect geostationary transfer orbit. The MSG-2 satellite is now under control of ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany, under a contract with EUMETSAT. In the coming days, it will perform a series of orbital manoeuvres using its onboard propulsion system in order to circularize its orbit at geostationary altitude.

“The successful launch of the second Meteosat satellite today reinforces the cooperation between the European Space Agency (ESA) and EUMETSAT in the designing and development of a series of missions devoted to meteorology” said Volker Liebig, ESA’s Director of Earth Observation programmes.

“Two further MSG satellites, planned to be launched, will guarantee continuity of services until around 2018. MSG- 2 improves today the provision of essential data and information for operational weather forecast and sustainable development” he continued.

MSG-2 is the first of three satellites based on the same design and procured by ESA on behalf of EUMETSAT, the European weather satellite organization, founded in 1986 and now encompassing all 17 ESA member states plus Turkey. Bulgaria, Croatia, the Czech Republic, Estonia, Hungary, Iceland, Latvia, Romania, Serbia-Montenegro, Slovakia and Slovenia are also contributing states to the organisation.

A new eye to watch our weather

The MSG satellites are designed to observe the Earth in twelve spectral bands and to deliver pictures every 15 minutes in visible light, infrared and at water vapour wavelength, with a ground resolution of 1 km. In all, they are able to return 10 times more data than the satellites of the original series.

Weighing about 2 metric tons at launch, the MSGs are twice and half heavier than their predecessors, but about half of this mass is propellant for reaching the operational orbit and station-keeping for about 7 years. They keep the same drum-shaped design but at a larger scale, with a 3.22-m diameter and a height of 3.74 m.

The payload is composed of two radiometers, SEVIRI and GERB. The Spinning Enhanced Visible & Infrared Imager (SEVIRI) observes the Earth in 12 spectral bands in visible light and infrared and delivers a picture of the hemisphere every 15 minutes. This allows to follow closely the development of rapidly evolving weather phenomena like storms, blizzards and fog. Its ground resolution in visible parts of the spectrum is 1 km, in order to monitor highly localized events.

The Global Earth Radiation Budget (GERB) experiment measures the amount of solar radiation reflected into space by the Earth and atmosphere, providing vital information about global climate change.

Besides these two instruments, MSG satellites carry a comprehensive communications payload for satellite operation, data communication and user data dissemination. It also includes a Search and Rescue transponder to relay distress signals from ships, aircraft and others in peril to the emergency services.

Witnessing global climate change

Once in geostationary orbit, MSG-2 will undergo several months of in-orbit commissioning before being operational. A first picture of the Earth captured by the SEVIRI instrument should be released by late January. In summer 2006 , MSG-2 is expected to enter operational service above the Gulf of Guinea, at 0 degree of longitude.

Renamed Meteosat 9, it will replace Meteosat 8 as the primary satellite to monitor the atmosphere and the climate. Meteosat 8 will be moved to 3.4 degrees West as a back-up satellite in order to ensure continuity of service in any circumstance. In addition EUMETSAT still operates the first-generation Meteosat 5, 6 and 7 satellites with an extended coverage over the Indian Ocean.

The MSG programme was decided in 1990 as follow-on to the highly successful original Meteosat series, with the introduction of new, more powerful and more accurate sensors, for a continuous observation of Earth’s atmosphere. With two more satellites currently ordered, the MSG series should provide coverage at least through 2018. This uninterrupted monitoring lasts since the very first Meteosat satellite, which was developed and launched by ESA in 1977. The Meteosat data are a unique testimony on the evolution of the planet’s climate over nearly three decades and its consequences on our weather.

Original Source: ESA Portal

Posted on by Fraser Cain

Galaxies Grow Up in Dark Matter Nurseries

An accurate illustration of young galaxies twe<lve billion light years awayClick to enlarge/a>
Astronomers have found clear indications that clumps of dark matter are the nursing grounds for new born galaxies about twelve billion light years away. A single nest of dark matter can nurture several young galaxies. These results from researchers at the Space Telescope Science Institute, the National Astronomical Observatory of Japan, and the University of Tokyo confirm predictions of the currently dominant theory of cosmology known as the Cold Dark Matter model.

Recent studies suggest that dark matter out weighs ordinary matter by a factor of seven. Although dark matter cannot be seen directly through a telescope, it reveals itself to astronomers by its strong gravitational pull on nearby stars and gas, and even galaxies.

Galaxies are often clustered together and how they cluster is determined mostly by gravity.

By studying how galaxies cluster, it is possible to determine how dark matter is distributed and how it affects the birth and growth of galaxies. In the past, it was extremely difficult to study the clustering of young galaxies. Young galaxies appear faint due to their great distances, and finding enough of them to study how they cluster was an observational challenge.

Masami Ouchi from the Space Telescope Science Institute and colleagues used the Subaru telescope and its Suprime-Cam camera to study a piece of the sky in the constellation Cetus (the Whale) called the Subaru/XMM-Newton Deep Survey Field (SXDS). This piece of sky covers an area five times the size of the full moon. By taking deep and sensitive images of the field in three colors of visible light, the SXDS team was able to find about seventeen thousand (17,000) young galaxies twelve billion light years away. This number is ten times larger than previous studies of such young galaxies.
Based on these data, the team found that:

1) There are many pairs of galaxies with separations less than eight hundred thousand (800,000) light years.
2) Even at large distances, galaxies are strongly clustered.

Both of these results are expected if the galaxies are nestled within clumps of dark matter. The SXDS team compared the observational results in detail to theoretical predictions based on a Cold Dark Matter model by team member Takashi Hamana and found that the average clump of dark matter nests weighs as much as six hundred billion (600,000,000,000) Suns, and that a single clump of dark matter harbors multiple young galaxies.

Independently, Nobunari Kashikawa from the National Astronomical Observatory of Japan and colleagues also used Subaru’s Suprime-Cam camera to study an area of sky in the constellation Coma Berenices (Berenice’s Hair) called the Subaru Deep Field (SDF). This field is only the size of one full moon but the data available are twice as sensitive as the SXDS field data. The SDF team found about five thousand (5,000) young galaxies at a distance of twelve billion light years, and eight hundred (800) even younger galaxies at a distance of twelve billion five hundred million light years. The SDF team was also able to double check the identities of the young galaxies by taking spectral data of the galaxies with the Subaru and Keck telescopes. The SDF team independently obtained the results 1)+2) described above, and concluded that some single clumps of dark matter harbours multiple young galaxies. In the SDF images, it is possible to see several new born galaxies huddled together in a small area. By comparing the SDF data in detail to high precision computer simulations of the growth of clumps in Cold Dark Matter by team member Masahiro Nagashima of Kyoto University, the SDF team concludes that heavier clumps of dark matter have more bright galaxies, and that this preference produces the correlations found in real observation.

The two teams together have found the first concrete evidence that young galaxies in the early universe are nestled within clumps of dark matter, and that a single clump of dark matter nurses several young galaxies. Both teams took advantage of the Subaru telescope’s unique ability to take deep sensitive images over a large area of sky.

Original Source: NAOJ News Release