Posted on by Fraser Cain

Expedition 9 Lands Safely

Image credit: NASA
International Space Station Expedition 9 crewmembers, Commander Gennady Padalka and NASA Science Officer Mike Fincke landed on target in the steppes of Kazakhstan at 8:36 p.m. EDT Saturday after 188 days in space.

Padalka and Fincke had undocked their Soyuz capsule from the orbiting laboratory at 5:08 p.m. EDT and headed home. With them was Russian Space Forces Test Cosmonaut Yuri Shargin, who had come to the Station with the Expedition 10 crew, Commander Leroy Chiao and Cosmonaut Salizhan Sharipov. Shargin spent eight days on the Station doing scientific experiments.

With Padalka and Fincke’s launch in April, six months earlier than initial plans, the two-man crew lived and worked on the Station, conducting scientific experiments and maintaining Station systems.

Fincke led the American scientific research agenda, working in the Destiny Laboratory module of the Space Station for advances to further future exploration.

In addition to continued studies on the effects of weightlessness on the human body, Fincke conducted multiple experiments in the physical sciences, completing more than 100 percent of the research agenda with 24 research experiments.

During their mission, Padalka and Fincke received two Russian Progress Cargo supply ships and conducted four spacewalks.

Soon after the crew’s arrival, one of the Station’s control moment gyroscopes, which control the vehicle’s orientation, lost power and shut down, requiring an unplanned spacewalk to replace a circuit breaker for the part. Donning Russian spacesuits, due to a cooling malfunction of the American spacesuits, Padalka and Fincke headed out into the void for their first time, but had to end the spacewalk within minutes when Fincke’s oxygen system was not operating correctly. On their second attempt, the pair navigated around the American side of the Station and successfully replaced the circuit breaker, restoring power to the gyroscope.

On two subsequent planned spacewalks, Padalka and Fincke replaced a set of samples being tested for their ability to withstand the space environment; they changed out a thruster residue experiment that had gathered data for more than two years; and installed radio antennas and upgraded navigational aids needed for next year’s arrival of the European Automated Transfer Vehicle (ATV).

Aside from their planned mission activities, the ninth crew to live on Station experienced a series of events that kept them connected to Earth during their six-month orbital stay.

During an unrelenting hurricane season, Padalka and Fincke captured the fury of an alphabet of tropical weather systems in the Atlantic and Caribbean: Alex, Bonnie, Charley, Frances and Ivan with digital cameras onboard.

From space, they observed both life and death. The crew celebrated the birth of Fincke’s baby daughter, Tarali Paulina, a first-time event for a Station resident and noted the death of former American President Ronald Reagan who first directed the construction of an orbital outpost.

Padalka and Fincke also did their part in inspiring the next generation of explorers in several Earth-bound activities, including a question-and-answer session to students on eating, a life necessity, in space.

Returned to Earth, Padalka and Fincke will take part in debriefings and medical activities in Star City, Russia. They will then travel to Houston in mid-November for further post-flight activities.

Station activities were handed over to the orbiting laboratory’s new residents, Expedition 10 crewmembers Commander Leroy Chiao and ISS Flight Engineer Salizhan Sharipov who arrived eight days ago.

Their mission includes two spacewalks, arrival of two unpiloted Progress supply capsules, and preparation for the arrival of the first Space Shuttle to visit the International Space Station since the Space Shuttle Columbia accident.

Science will continue, much of it with facilities and samples already on the Space Station. The Expedition 10 research agenda remains flexible. It includes experiments in human life sciences and space operations.

Chiao and Sharipov also will work with the Station’s robotic arm, Canadarm2. Their activities will focus on observations outside of the Station, maintaining operator proficiency, and completing the checkout of the Canadarm2 system.

Original Source: NASA News Release

Posted on by Fraser Cain

Cassini’s First Titan Flyby Tomorrow

Long hidden behind a thick veil of haze, Titan, the only known moon with an atmosphere, is ready for its close-up on Oct. 26, 2004. This visit by the Cassini spacecraft may settle intense speculation about whether this moon of Saturn harbors oceans of liquid methane and ethane beneath its coat of clouds.

Cassini will fly by Titan at a distance of 1,200 kilometers (745 miles), with closest approach at 9:44 a.m. Pacific Time. This flyby will be nearly 300 times closer than the first Cassini flyby of Titan, on July 3.

This is one of 45 planned flybys of Titan during the four-year tour. Subsequent flybys will bring the spacecraft even closer. Scientists believe Titan’s atmosphere is similar to that of early Earth.

“Cassini will see Titan as it has never been seen before. We expect the onboard instruments will pierce the moon’s dense atmosphere and reveal a whole new world,” said Dr. Charles Elachi, director of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and team leader for the Cassini radar instrument.

One important goal of this flyby is to confirm scientists’ model of Titan’s atmosphere to prepare for the Huygens probe descent. The probe, built and managed by the European Space Agency, will be cut loose from its mother ship on Christmas Eve and will coast through the atmosphere of Titan. On the way down, the probe will sample the atmosphere with a sophisticated set of scientific instruments.

“Titan has been lying still, waiting. Cassini may finally show us if what we thought of this moon is true, and whether the Huygens probe touchdown will be a splash,” said Dr. Jean-Pierre Lebreton, Huygens project manager and project scientist for the European Space Research and Technology Center, Noordwijk, Netherlands.

Eleven of Cassini’s 12 instruments will be aimed at Titan during this encounter. Scientists hope to learn more about Titan’s interior structure, surface, atmosphere and interaction with Saturn’s magnetosphere. This first in-place sampling of Titan’s atmosphere will help in understanding the atmosphere’s density and composition, which, in turn, will help aid management of the Huygens probe. This flyby will mark the first time Cassini’s imaging radar is used to observe Titan, and is expected to provide topographical maps and show whether there is a liquid or solid surface.

“We know our instrument will see through the haze to Titan’s surface,” said Dr. Robert H. Brown, team leader for the visual and infrared mapping spectrometer, University of Arizona, Tucson. “This encounter is about digging down below the atmosphere and getting our first glimpse of Titan geology.”

Cassini’s ion and neutral mass spectrometer will taste mysterious, subtle flavors in Titan’s atmosphere. “Our instrument will scoop up a breath of Titan’s puffy atmosphere during the flyby,” said Roger Yelle, instrument team member, also with the University of Arizona. The experiment will measure how many molecules of different masses it gathers in the gulp of Titan’s mostly nitrogen, methane-laced atmosphere.

Titan is Saturn’s largest moon. It is larger than Mercury or Pluto and is the second largest moon in the solar system, after Jupiter’s moon Ganymede. Titan is a cold place thought to be inhospitable to life at 95 degrees Kelvin (minus 289 degrees Fahrenheit).

Cassini has performed flawlessly since entering orbit around Saturn on June 30. The team believes that on Tuesday night, all will proceed as planned.

“This is not the same white-knuckle situation we had during Saturn orbit insertion, but there are some things we can’t control,” said Earl Maize, deputy project manager for the Cassini-Huygens mission at JPL. “If a spacecraft anomaly should occur, or if the weather at the tracking stations does not cooperate, the science return may be limited or lost. Although this is an unlikely scenario, the possibility still exists.” Cassini will have only one opportunity to send the data back to Earth before the data are overwritten on the recorders by data from the next set of observations. The first downlink of data by NASA’s Deep Space Network occurs at 6:30 p.m. PDT.

More information on the Cassini-Huygens mission is available at http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

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 Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Reminder: Plan for the Lunar Eclipse

As we reported a week ago, there’s going to be a lunar eclipse on October 27/28 which will be visible from the Americas and Western Europe. This’ll be the last chance to see a total lunar eclipse for a while, so I highly suggest – no, I demand – that you set aside some time on Wednesday evening to enjoy it. We’re having an eclipse party with some friends.

If it’s cloudy in your area, or you live in a part of the world that just can’t see it, don’t worry, I’ll be putting together my regular list of astrocameras focused on the Moon. If you’re going to be broadcasting coverage of the eclipse onto the Internet, please email me at [email protected] so that we can get as complete a coverage as possible.

Thanks!

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Spirit Steering Problem Returns

A problem that affects the steering on NASA’s Mars Exploration Rover Spirit has recurred after disappearing for nearly two weeks.

Engineers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., are working to fully understand the intermittent problem and then implement operational work-arounds. Meanwhile, Spirit successfully steered and drove 3.67 meters (12 feet) on Oct. 17.

Rover engineers are also analyzing a positive development on Spirit’s twin, Opportunity: a sustained boost in power generation by Opportunity’s solar panels.

Both rovers have successfully completed their three-month primary missions and their first mission extensions. They began second extensions of their missions on Oct. 1.

Rover engineers refrained from driving Spirit for five days after an Oct. 1 malfunction of a system that prevents wheels from being jostled in unwanted directions while driving. Each of the front and rear wheels of the rover has a motor called a steering actuator. It sets the direction in which the wheel is headed. The steering actuators are different from the motors that make the wheels roll, and hold the wheel in a specific direction while driving. A relay used in turning these steering actuators on and off is the likely cause of the intermittent nature of the anomaly.

The relay operates Spirit’s right-front and left-rear wheels concurrently, and did not operate as commanded on Oct. 1. Subsequent testing showed no trace of the problem, and on Oct. 7, the rover steered successfully and drove about 2 meters (7 feet), putting it in position to examine a layered rock called “Tetl” for several days. However, the anomaly occurred again on Oct. 13, and the problem appeared intermittently in tests later last week.

“We are continuing tests on Spirit and in our testbed here at JPL,” said Jim Erickson, Mars Exploration Rover project manager at JPL. One possible work-around would be to deliberately blow a fuse controlling the relay, disabling the brake action of the steering actuators. The rovers could be operated without that feature. “The only change might be driving in shorter steps when the rover is in rugged terrain,” Erickson said.

Spirit has driven a total of 3,647 meters (2.27 miles) since landing, more than six times the distance set as a goal for the mission. Its current target is a layered rock called “Uchben” in the “Columbia Hills.” Opportunity has driven 1,619 meters (just over a mile). Its latest stop is a lumpy boulder dubbed “Wopmay” inside “Endurance Crater.”

The daily power supply for each rover comes from 1.3 square meters (14 square feet) of solar panels converting sunlight into electricity. Just after the landings in January, the output was about 900 watt-hours per day for each rover — enough to run a 100-watt bulb for nine hours. As anticipated, output gradually declined due to dust buildup and the martian seasonal change with fewer hours of sunlight and a lower angle of the Sun in the sky. By July, Spirit’s daily output had declined to about 400 watt-hours per day. It has been between 400 and 500 watt-hours per day for most of the past two months.

Opportunity, closer to Mars’ equator and with the advantage of a sunward-facing tilt as it explored inside the southern half of a crater, maintained an output level between 500 and 600 watt-hours per day in June, July and August. Since early September, the amount of electricity from Opportunity’s solar panels has increased markedly and unexpectedly, to more than 700 watt-hours per day, a level not seen since the first 10 weeks of the mission.

“We’ve been surprised but pleased to see this increase,” said Erickson, “The team is evaluating ways to determine which of a few different theories is the best explanation.”

Possible explanations under consideration include the action of wind removing some dust from the solar panels or the action of frost causing dust to clump. “We seem to have had several substantial cleanings of the solar panels,” Erickson said.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Science Mission Directorate, Washington. Additional information about the project is available from JPL at http://marsrovers.jpl.nasa.gov/ and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Frame Dragging Confirmed

An international team of NASA and university researchers has found the first direct evidence the Earth is dragging space and time around itself as it rotates.

The researchers believe they have measured the effect, first predicted in 1918 by using Einstein’s theory of general relativity, by precisely observing shifts in the orbits of two Earth-orbiting laser-ranging satellites. The researchers observed the orbits of the Laser Geodynamics Satellite I (LAGEOS I), a NASA spacecraft, and LAGEOS II, a joint NASA/Italian Space Agency (ASI) spacecraft.

The research, reported in the journal Nature, is the first accurate measurement of a bizarre effect that predicts a rotating mass will drag space around it. The Lense-Thirring Effect is also known as frame dragging.

The team was led by Dr. Ignazio Ciufolini of the University of Lecce, Italy, and Dr. Erricos C. Pavlis of the Joint Center for Earth System Technology, a research collaboration between NASA’s Goddard Space Flight Center, Greenbelt, Md., and the University of Maryland Baltimore County.

“General relativity predicts massive rotating objects should drag space-time around themselves as they rotate,” Pavlis said. “Frame dragging is like what happens if a bowling ball spins in a thick fluid such as molasses. As the ball spins, it pulls the molasses around itself. Anything stuck in the molasses will also move around the ball. Similarly, as the Earth rotates, it pulls space-time in its vicinity around itself. This will shift the orbits of satellites near Earth.” The study is a follow-up to earlier work in 1998 where the authors’ team reported the first direct detection of the effect.

The previous measurement was much less accurate than the current work, due to inaccuracies in the gravitational model available at the time. Data from NASA’s GRACE mission allowed for a vast improvement in the accuracy of new models, which made this new result possible.

“We found the plane of the orbits of LAGEOS I and II were shifted about six feet (two meters) per year in the direction of the Earth’s rotation,” Pavlis said. “Our measurement agrees 99 percent with what is predicted by general relativity, which is within our margin of error of plus or minus five percent. Even if the gravitational model errors are off by two or three times the officially quoted values, our measurement is still accurate to 10 percent or better.” Future measurements by Gravity Probe B, a NASA spacecraft launched in 2004, should reduce this error margin to less than one percent. This promises to tell researchers much more about the physics involved.

Ciufolini’s team, using the LAGEOS satellites, previously observed the Lense-Thirring effect. It has recently been observed around distant celestial objects with intense gravitational fields, such as black holes and neutron stars. The new research around Earth is the first direct, precise measurement of this phenomenon at the five to 10 percent level. The team analyzed an 11-year period of laser ranging data from the LAGEOS satellites from 1993 to 2003, using a method devised by Ciufolini a decade ago.

The measurements required the use of an extremely accurate model of the Earth’s gravitational field, called EIGEN-GRACE02S, which became available only recently, based on an analysis of GRACE data. The model was developed at the GeoForschungs Zentrum Potsdam, Germany, by a group who are co-principal investigators of the GRACE mission along with the Center for Space Research of the University of Texas at Austin.

LAGEOS II, launched in 1992, and its predecessor, LAGEOS I, launched in 1976, are passive satellites dedicated exclusively to laser ranging. The process entails sending laser pulses to the satellite from ranging stations on Earth and then recording the round-trip travel time. Given the known value for the speed of light, this measurement enables scientists to precisely determine the distances between laser ranging stations on Earth and the satellite.

NASA and Stanford University, Palo Alto, Calif. developed Gravity Probe B. It will precisely check tiny changes in the direction of spin of four gyroscopes contained in an Earth satellite orbiting 400-miles directly over the poles. The experiment will test two theories relating to Einstein’s Theory of General Relativity, including the Lense-Thirring Effect. These effects, though small for Earth, have far-reaching implications for the nature of matter and the structure of the universe.

Original Source: NASA News Release

Posted on by Fraser Cain

The Virgo Galaxy Cluster is Still Being Formed

An international team of astronomers [2] has succeeded in measuring with high precision the velocities of a large number of planetary nebulae [3] in the intergalactic space within the Virgo Cluster of galaxies. For this they used the highly efficient FLAMES spectrograph [4] on the ESO Very Large Telescope at the Paranal Observatory (Chile).

These planetary nebulae stars free floating in the otherwise seemingly empty space between the galaxies of large clusters can be used as “probes” of the gravitational forces acting within these clusters. They trace the masses, visible as well as invisible, within these regions. This, in turn, allows astronomers to study the formation history of these large bound structures in the universe.

The accurate velocity measurements of 40 of these stars confirm the view that Virgo is a highly non-uniform galaxy cluster, consisting of several subunits that have not yet had time to come to equilibrium. These new data clearly show that the Virgo Cluster of galaxies is still in its making.

They also prove for the first time that one of the bright galaxies in the region scrutinized, Messier 87, has a very extended halo of stars, reaching out to at least 65 kpc. This is more than twice the size of our own galaxy, the Milky Way.

A young cluster
At a distance of approximately 50 million light-years, the Virgo Cluster is the nearest galaxy cluster. It is located in the zodiacal constellation Virgo (The Virgin) and contains many hundreds of galaxies, ranging from giant and massive elliptical galaxies and spirals like our own Milky Way, to dwarf galaxies, hundreds of times smaller than their big brethren. French astronomer Charles Messier entered 16 members of the Virgo cluster in his famous catalogue of nebulae. An image of the core of the cluster obtained with the Wide Field Imager camera at the ESO La Silla Observatory was published last year as PR Photo 04a/03.

Clusters of galaxies are believed to have formed over a long period of time by the assembly of smaller entities, through the strong gravitational pull from dark and luminous matter. The Virgo cluster is considered to be a relatively young cluster because previous studies have revealed small “sub-clusters of galaxies” around the major galaxies Messier 87, Messier 86 and Messier 49. These sub-clusters have yet to merge to form a denser and smoother galaxy cluster.

Recent observations have shown that the so-called “intracluster” space, the region between galaxies in a cluster, is permeated by a sparse “intracluster population of stars”, which can be used to study in detail the structure of the cluster.

Cosmic wanderers
The first discoveries of intracluster stars in the Virgo cluster were made serendipitously by Italian astronomer, Magda Arnaboldi (Torino Observatory, Italy) and her colleagues, in 1996. In order to study the extended halos of galaxies in the Virgo cluster, with the ESO New Technology Telescope at La Silla, they searched for objects known as “planetary nebulae” [3].

Planetary nebulae (PNe) can be detected out to large distances from their strong emission lines. These narrow emission lines also allow for a precise measure of their radial velocities. Planetary Nebulae can thus serve to investigate the motions of stars in the halo regions of distant galaxies.

In their study, the astronomers found several planetary nebulae apparently not related to any galaxies but moving in the gravity field of the whole cluster. These “wanderers” belonged to a newly discovered intracluster population of stars.

Since these first observations, several hundreds of these wanderers have been discovered. They must represent the tip of the iceberg of a huge population of stars swarming among the galaxies in these enormous clusters. Indeed, as planetary nebulae are the final stage of common low mass stars – like our Sun – they are representative of the stellar population in general. And as planetary nebulae are rather short-lived (a few tens of thousand years – a blitz on astronomical timescales), astronomers can estimate that one star in about 8,000 million of solar-type stars is visible as a planetary nebula at any given moment. There must thus be a comparable number of stars in between galaxies as in the galaxies themselves. But because they are diluted in such a huge volume, they are barely detectable.

Because these stars are predominantly old, the most likely explanation for their presence in the intracluster space is that they formed within individual galaxies, which were subsequently stripped of many of their stars during close encounters with other galaxies during the initial stages of cluster formation. These “lost” stars were then dispersed into intracluster space where we now find them.

Thus planetary nebulae can provide a unique handle on the number, type of stars and motions in regions that may harbour a substantial amount of mass. Their motions contain the fossil record of the history of galaxy interaction and the formation of the galaxy cluster.

Measuring the speed of dying stars
The international team of astronomers [2] went on further to make a detailed study of the motions of the planetary nebulae in the Virgo cluster in order to determine its dynamical structure and compare it with numerical simulations. To this aim, they carried out a challenging research programme, aimed at confirming intracluster planetary nebula candidates they found earlier and measuring their radial velocities in three different regions (“survey fields”) in the Virgo cluster core.

This is far from an easy task. The emission in the main Oxygen emission line from a planetary nebula in Virgo is comparable to that of a 60-Watt light bulb at a distance of about 6.6 million kilometres, about 17 times the average distance to the Moon. Furthermore intracluster planetary nebula samples are sparse, with only a few tens of planetary nebulae in a quarter of a degree square sky field – about the size of the Moon. Spectroscopic observations thus require 8 metre class telescopes and spectrographs with a large field of view. The astronomers had therefore to rely on the FLAMES-GIRAFFE spectrograph on the VLT [4], with its relatively high spectral resolution, its field of view of 25 arcmin and the possibility to take up to 130 spectra at a time.

The astronomers studied a total of 107 stars, among which 71 were believed to be genuine intracluster planetary candidates. They observed between 21 and 49 objects simultaneously for about 2 hours per field. The three parts of the Virgo core surveyed contain several bright galaxies (Messier 84, 86, 87, and NGC 4388) and a large number of smaller galaxies. They were chosen to represent different entities of the cluster.

The spectroscopic measurements could confirm the intracluster nature of 40 of the planetary nebulae studied. They also provided a wealth of knowledge on the structure of this part of the Virgo cluster.

In The Making
In the first field near Messier 87 (M87), the astronomers measured a mean velocity close to 1250 km/s and a rather small dispersion around this value. Most stars in this field are thus physically bound to the bright galaxy M87, in the same way as the Earth is bound to the Sun. Magda Arnaboldi explains: “This study has led to the remarkable discovery that Messier 87 has a stellar halo in approximate dynamical equilibrium out to at least 65 kpc, or more than 200,000 light-years. This is more than twice the size of our own galaxy, the Milky Way, and was not known before.”

The velocity dispersion observed in the second field, which is far away from bright galaxies, is larger than in the first one by a factor four. This very large dispersion, indicating stars moving in very disparate directions at different speeds, also tells us that this field most probably contains many intracluster stars whose motions are barely influenced by large galaxies. The new data suggest as a tantalizing possibility that this intracluster population of stars could be the leftover from the disruption of small galaxies as they orbit M87.

The velocity distribution in the third field, as deduced from FLAMES spectra, is again different. The velocities show substructures related to the large galaxies Messier 86, Messier 84 and NGC 4388. Most likely, the large majority of all these planetary nebulae belong to a very extended halo around Messier 84.

Ortwin Gerhard (University of Basel, Switzerland), member of the team, is thrilled: “Taken together these velocity measurements confirm the view that the Virgo Cluster is a highly non-uniform and unrelaxed galaxy cluster, consisting of several subunits. With the FLAMES spectrograph, we have thus been able to watch the motions in the Virgo Cluster, at a moment when its subunits are still coming together. And it is certainly a view worth seeing!”

More information
The results presented in this ESO Press Release are based on a research paper (“The Line-of-Sight Velocity Distributions of Intracluster Planetary Nebulae in the Virgo Cluster Core” by M. Arnaboldi et al.) that has just appeared in the research journal Astrophysical Journal Letters Vol. 614, p. 33.

Notes
[1]: The University of Basel Press Release on this topic is available at http://www.zuv.unibas.ch/uni_media/2004/20041022virgo.html.

[2]: The members of the team are Magda Arnaboldi (INAF, Osservatorio di Pino Torinese, Italy), Ortwin Gerhard (Astronomisches Institut, Universit?t Basel, Switzerland), Alfonso Aguerri (Instituto de Astrofisica de Canarias, Spain), Kenneth C. Freeman (Mount Stromlo Observatory, ACT, Australia), Nicola Napolitano (Kapteyn Astronomical Institute, The Netherlands), Sadanori Okamura (Dept. of Astronomy, University of Tokyo, Japan), and Naoki Yasuda (Institute for Cosmic Ray Research, University of Tokyo, Japan).

[3]: Planetary nebulae are Sun-like stars in their final dying phase during which they eject their outer layers into surrounding space. At the same time, they unveil their small and hot stellar core which appears as a “white dwarf star”. The ejected envelope is illuminated and heated by the stellar core and emits strongly in characteristic emission lines of several elements, notably oxygen (at wavelengths 495.9 and 500.7 nm). Their name stems from the fact that some of these nearby objects, such as the “Dumbbell Nebula” (see ESO PR Photo 38a/98) resemble the discs of the giant planets in the solar system when viewed with small telescopes.

[4]: FLAMES, the Fibre Large Array Multi-Element Spectrograph, is installed at the 8.2-m VLT KUEYEN Unit Telescope. It is able to observe the spectra of a large number of individual, faint objects (or small sky areas) simultaneously and covers a sky field of no less than 25 arcmin in diameter, i.e., almost as large as the full Moon. It is the result of a collaboration between ESO, the Observatoire de Paris-Meudon, the Observatoire de Gen?ve-Lausanne, and the Anglo Australian Observatory (AAO).

Original Source: ESO News Release

Posted on by Fraser Cain

Huygens Will Listen For Thunderstorms

Image credit: ESA
The sound of alien thunder, the patter of methane rain and the crunch (or splash) of a landing, all might be heard as Huygens descends to the surface of Titan on 14 January 2005.

What?s more, they will be recorded by a microphone on the probe and relayed back so that everyone on Earth can hear the sounds of Titan. Although the Russians took a microphone to Venus in the 1970s, few scientific results came out if that endeavour. A similar microphone for Mars was destroyed when NASA?s Mars Polar Lander crashed a few years ago.

The new microphone is part of the Huygens Atmospheric Structure Instrument (HASI), one of six multi-functional experiments carried on the Huygens probe. It is designed to help track down lightning by listening for the clap of thunder usually associated with such an event.

Although there is only a small chance that the spacecraft will pass near a thunderstorm, it is an extremely important investigation to carry out. It may help us to understand if thunderstorms are an important energy source for organic chemistry on Titan.

This may hold clues about how life began on Earth. Titan?s atmosphere is laced with chemicals and many scientists think these are the same as those that formed the building blocks of life on Earth, 4000 million years ago. But how did they join together on Earth to ultimately become DNA?

One possibility is that sudden discharges of energy, as occur in lightning, could have forced the simple chemicals together, making more complicated ones. So Huygens will listen for thunder and ?sniff? for chemicals that might have been produced in lightning strikes.

In fact, a second microphone experiment can also be found on Huygens. It is part of the Surface Science Package (SSP) and contributes to an experiment to measure the speed of sound in Titan?s atmosphere.

These results present an exciting possibility because if the HASI microphone does hear thunder, electrodes on the same instrument will register the lightning?s electrical discharge and scientists will be able to calculate how close Huygens passed to the storm.

If Huygens actually passes through a storm, the microphone will detect the splash of the rain onto the spacecraft casing. Unlike on Earth, this rain will not be water but probably liquid methane.

Marcello Fulchignoni, of the Universit? Denis Diderot, Paris, is the principal investigator of HASI. He says, ?Combined with the camera images, temperature and pressure profiles, and altitude data, the ?soundtrack? will provide a fascinating look at the details of the mission?s descent. We will be working hard to bring the voice of Huygens to the public as soon as we can after the descent.?

Original Source: ESA News Release

Posted on by Fraser Cain

Gmail Invites

I made a mention in yesterday’s newsletter that I had a few Gmail invites left over. You know, this is Google’s competitor to Hotmail and Yahoo that gives you a free email address with one GB of space. It’s still in beta, but I’m really impressed with it so far. I made a small mention down at the bottom, but I was still deluged with email requests for a Gmail invite. I had posted 6 invites in the Universe Today forum, and they were snapped up in a few minutes.

Now, I know there are hundreds of you reading this newsletter with some Gmail invites to spare, so I was wondering if you could help out. Visit the forum, head down to the bottom and post any spare invite links that you have. I’ve posted instructions in the forum on how to do this. Do not email me directly asking for an invite.

Here’s a link to the thread in the forum where everyone is posting their invites. Please help out if you can.

Thanks!

Fraser Cain
Publisher
Universe Today

P.S. The Universe Today forum has nearly 3,000 members now from all around the world. Come, hang out, and chat with other space enthusiasts!

Posted on by Fraser Cain

Arizona Telescope Turned Into a Robot

Today, the world of astronomy meets the science fiction world of Isaac Asimov’s “I, Robot” with the commissioning of a new robotic telescope. While it lacks the humanoid qualities of the movie version, this robot will aid in humanity’s quest to understand the early universe by observing the most distant and powerful explosions known.

Located at the Fred L. Whipple Observatory on Mt. Hopkins, Arizona, the Peters Automated Infrared Imaging Telescope (PAIRITEL) is the first fully “robotic” infrared telescope in North America dedicated to observing transient astronomical events. The telescope, used for several years in a major all-sky survey (2MASS), has been refurbished to work autonomously. It will operate in tandem with NASA’s new gamma-ray burst satellite “Swift,” to be launched on November 8 from Kennedy Space Center.

With PAIRITEL, a team of astronomers led by Dr. Joshua Bloom of the Harvard Society of Fellows, Harvard-Smithsonian Center for Astrophysics (CfA) and UC Berkeley, hopes to pinpoint the gamma-ray burst explosions from the first and most distant stars in the universe. A gamma ray burst (GRB) is a quick flash of gamma-ray radiation lasting about a minute, accompanied by an afterglow emission of X-rays, visible, infrared, and radio light. The afterglow may be observable for days to weeks afterward. The majority of GRBs are believed to be due to massive stars that explode violently and release tremendous blasts of energy.

“Innovatively exploring the night sky in the time domain – seeing how things change from night to night, and even from minute to minute – is the next big frontier in astronomy,” said Bloom. “PAIRITEL was optimized to study cosmic events like GRBs that are here today and gone tomorrow.”

Peering back to a time when the universe was less than 1 billion years old is the holy grail of observational astronomy. So far, only energetic galaxy cores known as quasars have been used to probe the early universe. But gamma-ray burst afterglows, if astronomers are able to image them quickly, hold clear advantages over quasars. For up to one hour after the burst, afterglow brightnesses can reach up to 1000 times that of the brightest known quasar in the universe.

Also, explained Bloom, “The stars that create GRBs likely formed before the black holes that create quasars. So by looking for the youngest and most distant GRBs, we can study the earliest epochs of the universe.”

A key feature of PAIRITEL that will allow the location of distant GRBs is its rapid response time. PAIRITEL will receive signals from Swift and automatically move, in under 2 minutes, to the part of the sky where a GRB has appeared.

“My ultimate vision is to have astronomy robots talking to robots, deciding what to observe and how, with no human intervention,” said Bloom. “As it is, PAIRITEL only e-mails us when it’s found a particularly interesting source, or when something goes wrong and it needs help!”

Another key feature of PAIRITEL is its sensitivity at infrared wavelengths, setting this system apart from the bevy of visible-light robotic telescopes already in existence. Images taken with infrared filters (about twice the wavelength of visible light) are indispensable: visible light emitted from more than 12 billion light-years away is completely extinguished for observers on Earth. Bloom explained, “Forget about the dimming due to the extreme distances: the hydrogen gas between us and the explosions makes it like searching for a firefly behind a thick London fog. In the infrared we can peer through the shroud to the good stuff.” In addition, the unique camera on PAIRITEL takes pictures simultaneously at three different wavelengths of light, allowing for instantaneous full-color snapshots.

The Swift spacecraft will find GRBs at a rate 10 to 20 times higher than currently feasible, and should find more bursts in 6 months than all well-studied bursts to date. Bloom said he is most excited about using Swift and PAIRITEL “together to find the golden needle in the haystack – a high-redshift GRB that’s farther away than the most distant known galaxy or quasar.”

When PAIRITEL is not chasing down GRBs, it will be used to make precision measurements of supernovae to help determine the few fundamental parameters that dictate the expansion of the universe. Among other projects, Dr. Michael Pahre (CfA) will use PAIRITEL to study the near-infrared light of nearby galaxies to compare it with mid-infrared light in images obtained with NASA’s Spitzer Space Telescope. Harvard graduate student Cullen Blake, who has written software for the project, will also use PAIRITEL to try to find Earth-mass planets around brown dwarfs. Other PAIRITEL team members include: Prof. Mike Skrutskie (Univ. of Virginia), Dr. Andrew Szentgyorgyi (CfA), Prof. Robert Kirshner (Harvard University/CfA), Dr. Emilio Falco (CfA), Dr. Thomas Matheson (NOAO), and Dan Starr (Gemini Observatory, Hawaii). The staff of Mt. Hopkins-Wayne Peters, Bob Hutchins, and Ted Groner-worked on the automation of the telescope.

PAIRITEL, nearly 2 years after the inception of the project, is being dedicated today to the late Jim Peters, who worked for the Smithsonian Astrophysical Observatory, first on satellite tracking and then as a telescope operator on Mt. Hopkins for 25 years. His widow and son will be in attendance at the ceremony.

The project was funded by a grant from the Harvard Milton Fund. The telescope is owned by the Smithsonian Astrophysical Observatory and the infrared camera is on loan from the University of Virginia.

Additional information about Swift and PAIRITEL is available online at:

http://swift.gsfc.nasa.gov/docs/swift/swiftsc.html
http://pairitel.org/

Original Source: CfA News Release

Posted on by Fraser Cain

Mystery Object in the Milky Way’s Halo

Most of the stars in our Milky Way galaxy lie in a very flat, pinwheel-shaped disk. Although this disk is prominent in images of galaxies similar to the Milky Way, there is also a very diffuse spherical “halo” of stars surrounding and enclosing the disks of such galaxies.

Recent discoveries have shown that this outer halo of the Milky Way is probably composed of small companion galaxies ripped to shreds as they orbited the Milky Way.

A discovery announced today by the Sloan Digital Sky Survey (SDSS) reveals a clump of stars unlike any seen before. The findings may shed light on how the Milky Way’s stellar halo formed.

This clump of newly discovered stars, called SDSSJ1049+5103 or Willman 1, is so faint that it could only be found as a slight increase in the number of faint stars in a small region of the sky.

“We discovered this object in a search for extremely dim companion galaxies to the Milky Way,” explains Beth Willman of New York University’s Center for Cosmology and Particle Physics. “However, it is 200 times less luminous than any galaxy previously seen.”

Another possibility, adds Michael Blanton, an SDSS colleague of Willman’s at New York University, is that Willman 1 is an unusual type of globular cluster, a spherical agglomeration of thousands to millions of old stars.”

“Its properties are rather unusual for a globular cluster. It is dimmer than all but three known globular clusters. Moreover, these dim globular clusters are all much more compact than Willman 1”, explains Blanton. “If it’s a globular cluster, it is probably being torn to shreds by the gravitational tides of the Milky Way.”

The real distinction between the globular cluster and dwarf galaxy interpretations is that galaxies are usually accompanied by substantial quantities of dark matter, says Julianne Dalcanton, an SDSS researcher at the University of Washington. “Clearly the next step is to carry out additional measurements to determine whether there is any dark matter associated with Willman 1.”

SDSS consortium member Daniel Zucker of the Max Planck Institute for Astronomy in Heidelberg, Germany, says the Sloan Digital Sky Survey has proven to be “a veritable gold mine for studies of the outer parts of our galaxy and its neighbors, as shown by Dr. Willman’s discovery, and by our group’s earlier discovery of a giant stellar structure and a new satellite galaxy around the Andromeda Galaxy.”

If Willman 1 does turn out to be a dwarf galaxy, this discovery could shed light on a long-standing mystery.

The prevailing ‘Cold Dark Matter’ model predicts that our own Milky Way galaxy is surrounded by hundreds of dark matter clumps, each a few hundred light years in size and possibly populated by a dwarf galaxy.

However, only 11 dwarf galaxies have been discovered orbiting the Milky Way. Perhaps some of these clumps have very few embedded stars, making the galaxies particularly difficult to find.

“If this new object is in fact a dwarf galaxy, it may be the tip of the iceberg of a yet unseen population of ultra-faint dwarf galaxies,” suggests Willman.

The Milky Way has been an area of intense research by SDSS consortium members.

“The colors of the stars in Willman 1 are similar to those in the Sagittarius tidal stream, a former dwarf companion galaxy to the Milky Way now in the process of merging into the main body of our Galaxy,” explains Brian Yanny, an SDSS astrophysicist at The Department of Energy’s Fermi National Accelerator Laboratory, a leader in research on the Milky Way’s accretion of material.

Continues Yanny: “If Willman 1 is a globular cluster, then it may have piggybacked a ride into our Galaxy’s neighborhood on one of these dwarf companions, like a tiny mite riding in on a flea as it, in turn, latches onto a massive dog.”

“Whether it is a globular cluster or a dwarf galaxy, this very faint object appears to represent one of the building blocks of the Milky Way,” Willman said.

Original Source: SDSS News Release