Hubble Unmasks Ghost Galaxies

ESA - Hubble Space Telescope logo.

10 July 2012

 Hubble probes ‘ghost’ galaxy

Astronomers have used the NASA/ESA Hubble Space Telescope to study some of the smallest and faintest galaxies in our cosmic neighbourhood. These galaxies are fossils of the early Universe: they have barely changed for 13 billion years. The discovery could help explain the so-called “missing satellite” problem, where only a handful of satellite galaxies have been found around the Milky Way, against the thousands that are predicted by theories.

Astronomers have puzzled over why some extremely faint dwarf galaxies spotted in our Milky Way galaxy’s backyard contain so few stars. The galaxies are thought to be some of the tiniest, oldest, and most pristine galaxies in the Universe. They have been discovered over the past decade by astronomers using automated computer techniques to search through the images of the Sloan Digital Sky Survey. But an international team of astronomers needed the NASA/ESA Hubble Space Telescope to help solve the mystery of why these galaxies are starved of stars, and why so few of them have been found.

Hubble probes ‘ghost’ galaxy

Hubble views of three of these small galaxies, the Hercules, Leo IV and Ursa Major dwarf galaxies, reveal that they all started forming stars more than 13 billion years ago — and then abruptly stopped — all in the first billion years after the Universe was born in the Big Bang. In fact, the extreme age of their stars is similar to Messier 92, the oldest known globular cluster [1] in the Milky Way.

“These galaxies are all ancient and they’re all the same age, so you know something came down like a guillotine and turned off the star formation at the same time in these galaxies,” said Tom Brown of the Space Telescope Science Institute in Baltimore, USA, the study’s leader. “The most likely explanation is a process called reionisation.”

The relic galaxies are evidence for a transitional phase in the early Universe that shut down star-making factories in tiny galaxies. This phase seems to coincide with the time when the first stars burned off a fog of cold hydrogen, a process called reionisation. In this period, which began in the first billion years after the Big Bang, radiation from the first stars knocked electrons off primeval hydrogen atoms, ionising the Universe’s cool hydrogen gas. [2]

Veil lifted on ‘ghost’ galaxy

The same radiation that sparked universal reionisation also appears to have squelched star-making activities in dwarf galaxies, such as those in Brown’s study. The small irregular galaxies were born about 100 million years before reionisation began and had just started to churn out stars at that time. Roughly 2000 light-years wide, these galaxies are the lightweight cousins of the more luminous and higher-mass star-making dwarf galaxies near our Milky Way. Unlike their higher-mass relatives, the puny galaxies were not massive enough to shield themselves from the harsh ultraviolet light. What little gas they had was stripped away as the flood of ultraviolet light rushed through them. Their gas supply depleted, the galaxies could not make new stars.

The discovery could help explain the so-called “missing satellite problem,” where only a few dozen dwarf galaxies have been observed around the Milky Way while the computer simulations predict that thousands should exist. One possible explanation for the low number discovered to date is that there has been very little, or even no star formation in the smallest of these dwarf galaxies, leaving them virtually invisible.

A swarm of dark matter around the Milky Way

The Sloan survey recently uncovered more than a dozen of these galaxies in our cosmic neighbourhood. These have very few stars — only a few hundred or thousand — but a great deal of dark matter, the underlying scaffolding upon which galaxies are built. Normal dwarf galaxies near the Milky Way contain 10 times more dark matter than the ordinary matter that makes up gas and stars, while in these so-called ultra-faint dwarf galaxies, dark matter outweighs ordinary matter by at least a factor of 100. Astronomers think the rest of the sky should contain dozens more of these ultra-faint dwarf galaxies with few stars, and the evidence for squelched star formation in the smallest of these dwarfs suggests that there may be still thousands more with essentially no stars at all.

Animated movie traces evolution of stars in dwarf galaxy

“By measuring the star formation histories of the observed dwarfs, Hubble has supported the theoretical explanation for the paucity of such objects, according to which star formation in the smaller clumps would be shut down by reionisation,” said Jason Tumlinson of the Space Telescope Science Institute, a member of the research team.

The results are published in the 1 July issue of The Astrophysical Journal Letters.

Notes:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of T. M. Brown (STScI), J. Tumlinson (STScI), M. Geha (Yale), E. N. Kirby (Cal Tech), D. A. VandenBerg (University of Victoria), R. R. Munoz (University of Chile), J. S. Kalirai (STScI), J. D. Simon (Carnegie Institution), R. J. Avila (STScI), P. Guhathakurta (UCO/Lick), A. Renzini (Osservatorio Astronomico di Padova) and, H. C. Ferguson (STScI)

[1] Globular clusters are tightly-bound spherical collections of up to a few hundred thousand stars. They are known to contain some of the most ancient stars in the Universe. In addition, globular clusters are known to have formed in single events, so all the stars in them have the same age.

[2] The period of reionisation is also the limit for how far telescopes can see: the process is what rendered the Universe’s hydrogen gas transparent to ultraviolet light.

Links:

    Science paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1211.pdf

    Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

Images, Video, Text, Credits: NASA, ESA, and T. Brown, J. Tumlinson (STScI).

Best regards, Orbiter.ch

ESA’s Clean Space targets orbital debris and greener environment

ESA - ESTEC logo.

10 July 2012

Next year’s Hollywood film Gravity features George Clooney stranded in orbit by cascading space junk. The threat is genuine, with debris levels rising steadily. ESA’s new Clean Space initiative is developing methods of preserving near-Earth space – and the terrestrial environment, too.

Responding to public environmental concerns, Clean Space aims to reduce the environmental effect of Europe’s space activities, cutting waste and pollution on Earth and in orbit.

Debris in low-Earth orbit

Industry is contributing to ESA’s draft plans for developing Clean Space technologies: new tools to assess environmental effects, more eco-friendly replacements for materials and techniques, and ways to halt the production of more space debris and bring down existing debris levels. 

ESA Director General Jean-Jacques Dordain emphasises that implementing Clean Space is a major objective of Agenda 2015, the Agency’s upcoming action plan: “If we are convinced that space infrastructure will become more and more essential, then we must transmit the space environment to future generations as we found it, that is, pristine.”

Mr Dordain, ESA Director General

“We can therefore say that Clean Space is not a new programme, but instead a new way of designing all of ESA’s programmes. I would like ESA to become a model agency in this respect.

“We will not succeed alone; we will need everyone’s help. The entire space sector has to be with us.”

ESTEC, ESA’s technical centre in Noordwijk, the Netherlands, hosted a Clean Space workshop in June, jointly organised by ESA and industry body Eurospace.

Earth: cleaning up space projects

On Earth, Clean Space involves evaluating the environmental impact of future space projects, as well as monitoring the likely effects of forthcoming legislation on the space industry – environmental law being an extremely fast-moving field.

Clean Space workshop

Life-cycle assessment will be important for evaluating the environmental effects of space technologies, from their initial design and manufacture to their end-of-life.

In the workshop, Environmental consultancy BIO Intelligence Services described the current wide employment of life-cycle assessment in other industrial sectors.

Environmental friendliness often goes hand-in-hand with increased efficiency – offering industry competitive advantage.

Novel manufacturing processes such as ‘additive manufacturing’, where structures are built up in layers, or ‘friction stir welding’, where lower weld temperatures use less materials and energy to do a better job.

Example of additive manufacturing

Reducing the need for often costly waste disposal is another win–win: rocket maker Safran is working on a biological method of breaking down toxic solid-propellant waste.

Space: cleaner means safer

In Gravity, runaway orbital collisions fill low-Earth orbit with a lethal debris cloud.

In real life, of the 6000 satellites launched during the Space Age, less than 1000 remain operational. The rest are derelict and prone to fragment as leftover fuel or batteries explode.

Exploding satellite

Orbiting at 7.5 km/s or more, even a 2 cm screw has sufficient ‘lethal diameter’ to take out a satellite.

The workshop discussed various means of minimising future debris production, such as tethers or sails to help drag abandoned satellites out of low orbit within 25 years.

Satellite reentry also needs to be a safer process – sometimes entire chunks of satellites have hit the ground intact. New ‘design for demise’ concepts aim to prevent that.

But even if all space launches stop tomorrow, simulations show that debris levels will keep growing. Active removal is also needed, including robotic missions to repair or deorbit satellites.

For more information, visit ESA's new Clean Space website (see below link).

Related Links:

Clean Space Eco-design and Green Technologies Workshop 2012Gravity (film): http://www.esa.int/SPECIALS/DG/SEML5F1VW3H_0.html

Space agencies leading way to sustainable future: http://www.esa.int/SPECIALS/Technology/SEMN7QZW5VG_0.html

Clean Space website: http://www.esa.int/TEC/Clean_Space/

Images, Text, Credits: ESA / Arcam AB.

Greetings, Orbiter.ch

We have liftoff! of the Proton M Breeze M rocket and the SES-5 satellite

ILS / ROSCOSMOS - SES-5 poster.

July 9, 2012

 Preparations to launch Proton-M rocket

Today at 6:38pm GMT - SES-5 launch with an ILS Proton-M rocket from Baikonur cosmodrome in Kazakhstan.

liftoff of the Proton M Breeze M rocket and the SES-5 satellite

SES’ high-powered Ku-band beams will bring incremental capacity over Africa, and the Nordic and Baltic countries to support DTH services. Its comprehensive C-band beams cover Africa, the Middle East and Europe to enable services such as GSM backhaul, VSAT applications, maritime communications and video distribution. SES-5 will also carry the first hosted L-band payload for the European Geostationary Navigation Overlay Service (EGNOS). The EGNOS payload, which was developed by the European Space Agency (ESA) and the European Commission (EC), will help verify, improve, and report on the reliability and accuracy of navigation positioning signals in Europe.

SES-5 satellite

The Proton M launch vehicle, utilizing a 5-burn Breeze M mission design, lift off from Pad 24 at Baikonur Cosmodrome, Kazakhstan, with the SES-5 satellite on board. The first three stages of the Proton use a standard ascent profile to place the orbital unit (Breeze M upper stage and the SES-5 satellite) into a sub-orbital trajectory. From this point in the mission, the Breeze M perform planned mission maneuvers to advance the orbital unit first to a circular parking orbit, then to an intermediate orbit, followed by a transfer orbit, and finally to a geostationary transfer orbit. Separation of the SES-5 satellite is scheduled to occur approximately 9 hours, 12 minutes after liftoff.

For more information about the Mission SES-5, visit: http://www.ilslaunch.com/mission-control/mission-ses-5

Images, Video, Text, Credits: ILS / ROSCOSMOS / Loral / Orbiter.ch.

Greetings, Orbiter.ch

Cosmic Cocoon

NASA - Chandra X-ray Observatory patch.

July 9, 2012

Using observations from NASA's Chandra X-ray Observatory, researchers have obtained the first X-ray evidence of a supernova shock wave breaking through a cocoon of gas surrounding the star that exploded. This discovery may help astronomers understand why some supernovas are much more powerful than others.

On Nov. 3, 2010, a supernova was discovered in the galaxy UGC 5189A, located about 160 million light years away. Using data from the All Sky Automated Survey telescope in Hawaii taken earlier, astronomers determined this supernova exploded in early October 2010.

This composite image of UGC 5189A shows X-ray data from Chandra in purple and optical data from Hubble Space Telescope in red, green and blue. SN 2010jl is the very bright X-ray source near the top of the galaxy.

Chandra X-ray Observatory

A team of researchers used Chandra to observe this supernova in December 2010 and again in October 2011. The supernova was one of the most luminous that has ever been detected in X-rays.

In the first Chandra observation of SN 2010jl, the X-rays from the explosion's blast wave were strongly absorbed by a cocoon of dense gas around the supernova. This cocoon was formed by gas blown away from the massive star before it exploded.

In the second observation taken almost a year later, there is much less absorption of X-ray emission, indicating that the blast wave from the explosion has broken out of the surrounding cocoon. The Chandra data show that the gas emitting the X-rays has a very high temperature -- greater than 100 million degrees Kelvin – strong evidence that it has been heated by the supernova blast wave.

In a rare example of a cosmic coincidence, analysis of the X-rays from the supernova shows that there is a second unrelated source at almost the same location as the supernova. These two sources strongly overlap one another as seen on the sky. This second source is likely to be an ultraluminous X-ray source, possibly containing an unusually heavy stellar-mass black hole, or an intermediate mass black hole.

For more information about Chandra X-ray Observatory, visit: http://www.nasa.gov/mission_pages/chandra/main/index.html

Images, Text, Credit: X-ray: NASA / CXC / Royal Military College of Canada/P.Chandra et al); Optical: NASA / STScI.

Best regards, Orbiter.ch

The Mysterious Case of the Disappearing Dust

NASA - WISE Mission patch.

July 9, 2012

This artist's concept illustrates a dusty planet-forming disk, similar to the one that vanished around the star called TYC 8241 2652. Image credit: NASA / JPL-Caltech.

Imagine if the rings of Saturn suddenly disappeared. Astronomers have witnessed the equivalent around a young sun-like star called TYC 8241 2652. Enormous amounts of dust known to circle the star are unexpectedly nowhere to be found.

"It's like the classic magician's trick: now you see it, now you don't. Only in this case we're talking about enough dust to fill an inner solar system and it really is gone!" said Carl Melis of the University of California, San Diego, who led the new study appearing in the July 5 issue of the journal Nature.

A dusty disk around TYC 8241 2652 was first seen by the NASA Infrared Astronomical Satellite (IRAS) in 1983, and continued to glow brightly for 25 years. The dust was thought to be due to collisions between forming planets, a normal part of planet formation. Like Earth, warm dust absorbs the energy of visible starlight and reradiates that energy as infrared, or heat, radiation.

The first strong indication of the disk's disappearance came from images taken in January 2010 by NASA's Wide-field Infrared Survey Explorer, or WISE. An infrared image obtained at the Gemini telescope in Chile on May 1, 2012, confirmed that the dust has now been gone for two-and-a-half years.

"Nothing like this has ever been seen in the many hundreds of stars that astronomers have studied for dust rings," said co-author Ben Zuckerman of UCLA, whose research is funded by NASA. "This disappearance is remarkably fast even on a human time scale, much less an astronomical scale. The dust disappearance at TYC 8241 2652 was so bizarre and so quick, initially I figured that our observations must simply be wrong in some strange way."

Wide-field Infrared Survey Explorer (WISE). Image credit: NASA / JPL-Caltech

The astronomers have come up with a couple of possible solutions to the mystery, but they say none are compelling. One possibility is that gas produced in the impact that released the dust helped to quickly drag the dust particles into the star and thus to their doom. In another possibility, collisions of large rocks left over from an original major impact provide a fresh infusion of dust particles into the disk, which caused the dust grains to chip apart into smaller and smaller pieces.

The result is based upon multiple sets of observations of TYC 8241 2652 obtained with the Thermal-Region Camera Spectrograph on the Gemini South telescope in Chile; IRAS; WISE; NASA's Infrared Telescope on Mauna Kea in Hawaii; the European Space Agency's Herschel Space Telescope, in which NASA plays an important role; and the Japanese/European Space Agency AKARI infrared satellite.

Read the Gemini news release at http://www.gemini.edu/node/11836 , and the UCLA release at http://newsroom.ucla.edu/portal/ucla/astronomers-discover-a-houdini-235572.aspx .

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages, and operated, WISE for NASA's Science Mission Directorate. The spacecraft was put into hibernation mode after it scanned the entire sky twice, completing its main objectives. Edward Wright is the principal investigator and is at UCLA. The mission was selected competitively under NASA's Explorers Program managed by the agency's Goddard Space Flight Center in Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah. The spacecraft was built by Ball Aerospace & Technologies Corp. in Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

IRAS was executed jointly by the United States (NASA), the Netherlands and the United Kingdom. The Infrared Telescope is operated and managed for NASA by the University of Hawaii, located in Honolulu.

More information is online at http://www.nasa.gov/wise, http://wise.astro.ucla.edu and http://jpl.nasa.gov/wise

Images (mentioned), Text, Credit: NASA / JPL / Whitney Clavin.

Greetings, Orbiter.ch

Mars Panorama - Next Best Thing to Being There

NASA - Mars Exploration Rover Opportunity (MER-B) patch.

July 9, 2012

Image above: This full-circle scene combines 817 images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity. Image credit: NASA / JPL-Caltech / Cornell / Arizona State Univ.

From fresh rover tracks to an impact crater blasted billions of years ago, a newly completed view from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity shows the ruddy terrain around the outcrop where the long-lived explorer spent its most recent Martian winter.

This scene recorded from the mast-mounted color camera includes the rover's own solar arrays and deck in the foreground, providing a sense of sitting on top of the rover and taking in the view. Its release this week coincides with two milestones: Opportunity completing its 3,000th Martian day on July 2, and NASA continuing past 15 years of robotic presence at Mars. Mars Pathfinder landed July 4, 1997. NASA's Mars Global Surveyor orbiter reached the planet while Pathfinder was still active, and Global Surveyor overlapped the active missions of the Mars Odyssey orbiter and Opportunity, both still in service.

The new panorama is online at http://photojournal.jpl.nasa.gov/catalog/PIA15689. It is presented in false color to emphasize differences between materials in the scene. It was assembled from 817 component images taken between Dec. 21, 2011, and May 8, 2012, while Opportunity was stationed on an outcrop informally named "Greeley Haven," on a segment of the rim of ancient Endeavour Crater.

"The view provides rich geologic context for the detailed chemical and mineral work that the team did at Greeley Haven over the rover's fifth Martian winter, as well as a spectacularly detailed view of the largest impact crater that we've driven to yet with either rover over the course of the mission," said Jim Bell of Arizona State University, Tempe, Pancam lead scientist.

Mars Exploration Rover B "Opportunity". Image Credits: NASA / JPL-Caltech

Opportunity and its twin, Spirit, landed on Mars in January 2004 for missions originally planned to last for three months. NASA's next-generation Mars rover, Curiosity, is on course for landing on Mars next month.

Opportunity's science team chose to call the winter campaign site Greeley Haven in tribute to Ronald Greeley (1939-2011), a team member who taught generations of planetary science students at Arizona State University.

"Ron Greeley was a valued colleague and friend, and this scene, with its beautiful wind-blown drifts and dunes, captures much of what Ron loved about Mars," said Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for Opportunity and Spirit.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for the NASA Science Mission Directorate, Washington.

More information about Opportunity is online at: http://www.nasa.gov/rovers and http://marsrovers.jpl.nasa.gov . You can follow the project on Twitter at http://twitter.com/MarsRovers and on Facebook at http://www.facebook.com/mars.rovers .

Images (mentioned), Text, Credit: NASA / JPL / Guy Webster.

Cheers, Orbiter.ch

Flying along the Vela ridge

ESA - Herschel Mission patch.

9 July 2012

 Vela C region (click on the image for enlarge)

A beautiful blue butterfly flutters towards a nest of warm dust and gas, above an intricate network of cool filaments in this image of the Vela C region by ESA’s Herschel space observatory.

Vela C is the most massive of the four parts of the Vela complex, a massive star nursery just 2300 light-years from the Sun. It is an ideal natural laboratory for us to study the birth of stars.

Herschel’s far-infrared detectors can spot regions where young high- and low-mass stars have heated dense clumps of gas and dust, where new generations of stars may be born.

The eye is immediately drawn to two prominent features in this image: a delicate blue and yellow butterfly shape just right of centre that appears to be flying towards a nest of coiled blue material in the lower right.

Herschel space observatory

These regions stand out from their surroundings because their dust has been heated by young hot stars. A cluster of very hot, massive stars are strung out along the butterfly’s ‘body’, their radiation heating up the surrounding dust seen as yellow in this scene.

These heavy stars will follow ‘live fast, die young’, burning brightly for only a short time in cosmic terms. Those with more than eight times the mass of our own Sun will explode as cataclysmic supernovas within 10 million years of forming.

A particularly dense trunk of cool gas and dust weaves its way through the centre of the image, surrounded by a complex network of wispy red filaments.

Deeply embedded inside the filaments are numerous point-like sources, particularly evident towards the left of the scene: these are protostars, the seeds of new stars that will soon also light up the Vela region of the sky. 

For more information about Herschel Mission, visit: http://www.esa.int/esaMI/Herschel/index.html
and http://www.nasa.gov/mission_pages/herschel/index.html

Images, Text, Credits: ESA / PACS & SPIRE Consortia, T. Hill, F. Motte, Laboratoire AIM Paris-Saclay, CEA / IRFU – CNRS / INSU – Uni. Paris Diderot, HOBYS Key Programme Consortium.

Greetings, Orbiter.ch