Most Accurate Distance to NGC 300

Observed Fields in NGC 300. Image credit: ESO Click to enlarge
Cepheid pulsating stars have been used as distance indicators since the early discovery of Henrietta Leavitt almost a hundred years ago. From her photographic data regarding one of the Milky Way’s neighbour galaxies, the Small Magellanic Cloud, she found that the brightness of these stars closely correlate with their pulsation periods.

This period-luminosity relation, once calibrated, allows a precise distance determination of a galaxy once Cepheids have been discovered in it, and their periods and mean magnitudes have been measured.

While the Cepheid method doesn’t reach out far enough in the Universe to directly determine cosmological parameters like the Hubble constant, Cepheid distances to relatively nearby resolved galaxies have laid the foundation for such work in the past, as in the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Cepheids indeed constitute one of the first steps in the cosmic distance ladder.

The current main problem with the Cepheid method is that its dependence on a galaxy’s metallicity, that is, its content in elements more heavy than hydrogen and helium, has never been measured accurately so far. Another intriguing difficulty with the method is the fact that the total absorption of the Cepheid’s light on its way to Earth, and in particular the amount of absorption within the Cepheid’s host galaxy, must be precisely established to avoid significant errors in the distance determination.

To tackle this problem, Wolfgang Gieren (University of Concepcion, Chile) and his team devised a Large Programme at ESO: the Araucaria Project. Its aim is to obtain distances to relatively nearby galaxies with a precision better than 5 percent.

One of the key galaxies of the team’s Araucaria Project is the beautiful, near face-on galaxy NGC 300 in the Sculptor Group. In a wide-field imaging survey carried out at the ESO/MPG 2.2-m telescope on La Silla in 1999-2000, the team had discovered more than a hundred Cepheid variables spanning a broad range in pulsation period. Pictures of the galaxy, and some of its Cepheids from these data were released in ESO Press Photos 18a-h in 2002. Last year, the team presented the distance of NGC 300 as derived from these optical images in V- and I-bands.

The team complemented this unique dataset with new data taken with the ISAAC near-infrared camera and spectrometer on ESO’s 8.2-m VLT Antu telescope.

“There are three substantial advantages in the Cepheid distance work when images obtained through near-infrared passbands are used instead of optical data”, says Wolfgang Gieren. The most important gain is the fact that the absorption of starlight in the near-infrared, and particularly in the K-band, is dramatically reduced as compared to the effect interstellar matter has at visible wavelengths. A second advantage is that Cepheid light curves in the infrared have smaller amplitudes and are much more symmetrical than their optical counterparts, making it possible to measure a Cepheid’s mean K-band brightness just from a very few, and in principle from just one observation at known pulsation phase. In contrast, optical work requires the observation of full light curves to determine accurate mean magnitudes. The third basic advantage in the infrared is a reduced sensitivity of the period-luminosity relation to metallicity, and to blending with other stars in the crowded fields of a distant galaxy.

Taking this into account, one of the main purposes of the team’s Large Programme has been to conduct near-infrared follow-up observations of Cepheids in their project’s target galaxies which have previously been discovered in optical wide-field surveys.

Deep images in the J and K bands of three fields in NGC 300 containing 16 Cepheids were taken with VLT/ISAAC in 2003.

“The high quality of the data allowed a very accurate measurement of the mean J- and K- magnitudes of the Cepheids from just 2 observations of each star obtained at different times”, says Grzegorz Pietrzynski, another member of the team, also from Concepcion.

Using these remarkable data the period-luminosity relations were constructed. “They are the most accurate infrared PL relations ever obtained for a Cepheid sample in a galaxy beyond the Magellanic Clouds”, emphasizes Wolfgang Gieren.

The total absorption of light (“reddening”) of the Cepheids in NGC 300 was obtained by combining the values for the distance of the galaxy obtained in the various optical and near-infrared bands in which NGC 300 was observed. This led to the discovery that there is a very significant contribution to the total reddening from absorption intrinsic to NGC 300. This intrinsic absorption has an important effect on the determination of the distance but had not been taken into account previously.

The team was able to measure the distance to NGC 300 with the unprecedented total uncertainty of only about 3 percent. The astronomers found that NGC 300 is located 6.13 million light-years away.

Original Source: ESO News Release

Cassini Finds Active Ice on Enceladus

Map showing observed temperatures at Enceladus. Image credit: NASA/JPL/GSFC. Click to enlarge
Saturn’s tiny icy moon Enceladus, which ought to be cold and dead, instead displays evidence for active ice volcanism.

NASA’s Cassini spacecraft has found a huge cloud of water vapor over the moon’s south pole, and warm fractures where evaporating ice probably supplies the vapor cloud. Cassini has also confirmed Enceladus is the major source of Saturn’s largest ring, the E-ring.

“Enceladus is the smallest body so far found that seems to have active volcanism,” said Dr. Torrence Johnson, Cassini imaging-team member at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Enceladus’ localized water vapor atmosphere is reminiscent of comets. ‘Warm spots’ in its icy and cracked surface are probably the result of heat from tidal energy like the volcanoes on Jupiter’s moon Io. And its geologically young surface of water ice, softened by heat from below, resembles areas on Jupiter’s moons, Europa and Ganymede.”

Cassini flew within 175 kilometers (109 miles) of Enceladus on July 14. Data collected during that flyby confirm an extended and dynamic atmosphere. This atmosphere was first detected by the magnetometer during a distant flyby earlier this year.

The ion and neutral mass spectrometer and the ultraviolet imaging spectrograph found the atmosphere contains water vapor. The mass spectrometer found the water vapor comprises about 65 percent of the atmosphere, with molecular hydrogen at about 20 percent. The rest is mostly carbon dioxide and some combination of molecular nitrogen and carbon monoxide. The variation of water vapor density with altitude suggests the water vapor may come from a localized source comparable to a geothermal hot spot. The ultraviolet results strongly suggest a local vapor cloud.

The fact that the atmosphere persists on this low-gravity world, instead of instantly escaping into space, suggests the moon is geologically active enough to replenish the water vapor at a slow, continuous rate.

“For the first time we have a major clue not only to the role of water at the icy moons themselves, but also to its role in the evolution and dynamics of the Saturn system as a whole,” said Dr. Ralph L. McNutt, ion and neutral mass spectrometer-team member, Johns Hopkins University Applied Physics Laboratory, Laurel, Md.

Images show the south pole has an even younger and more fractured appearance than the rest of Enceladus, complete with icy boulders the size of large houses and long, bluish cracks or faults dubbed “tiger stripes.”

Another Cassini instrument, the composite infrared spectrometer, shows the south pole is warmer than anticipated. Temperatures near the equator were found to reach a frigid 80 degrees Kelvin (minus 316 Fahrenheit), as expected. The poles should be even colder because the Sun shines so obliquely there. However, south polar average temperatures reached 85 Kelvin (minus 307 Fahrenheit), much warmer than expected. Small areas of the pole, concentrated near the “tiger stripe” fractures, are even warmer: well over 110 Kelvin (minus 261 Fahrenheit) in some places.

“This is as astonishing as if we’d flown past Earth and found that Antarctica was warmer than the Sahara,” said Dr. John Spencer, team member of the composite infrared spectrometer, Southwest Research Institute, Boulder, Colo.

Scientists find the temperatures difficult to explain if sunlight is the only heat source. More likely, a portion of the polar region, including the “tiger stripe” fractures, is warmed by heat escaping from the interior. Evaporation of this warm ice at several locations within the region could explain the density of the water vapor cloud detected by other instruments. How a 500-kilometer (310-mile) diameter moon can generate this much internal heat and why it is concentrated at the south pole is still a mystery.

Cassini’s cosmic dust analyzer detected a large increase in the number of particles near Enceladus. This observation confirms Enceladus is a source of Saturn’s E-ring. Scientists think micrometeoroids blast the particles off, forming a steady, icy, dust cloud around Enceladus. Other particles escape, forming the bulk of the E ring.

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. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.

Additional information and graphics on these results are available at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Original Source: NASA News Release

What’s Up This Week – August 1 – August 7, 2005

Globular cluster M22. Image credit: N.A. Sharp/REU Program NOAO/AURA/NSF. Click to enlarge.
Monday, August 1 – Today is the birthdate of Maria Mitchell. Born in 1818, Mitchell, became the first woman to be elected as an astronomer to the American Academy of Arts and Sciences. She later rocketed to worldwide fame when she discovered a bright comet in 1847.

Tonight, let’s continue our exploration of globular clusters. These gravitationally bound concentrations of stars contain anywhere from ten thousand to one million members and attain sizes of up to 200 light years in diameter. At one time, these fantastic members of our galactic halo were believed to be round nebula, and perhaps the very first to be discovered was M22 in Saggitarius by Abraham Ihle in 1665. This particular globular is easily seen in even small binoculars and can be easily located just slightly more than two degrees northeast of the “teapot’s lid”, Lambda – Kaus Borealis.

Ranking third amidst the 151 known globular clusters in total light, the M22 is probably the nearest of these incredible systems to our Earth with an approximate distance of 9,600 light years and is also one of the nearest globulars to the galactic plane. Since it resides less than a degree from the ecliptic, it often shares the same eyepiece field with a planet. At magnitude 6, the class VII M22 will begin to show individual stars to even modest instruments and will burst into stunning resolution for larger aperture. About a degree west/northwest, mid-sized telescopes and larger binoculars will capture smaller 8th magnitude NGC 6642. At class V, this particular globular will show more concentration toward the core region than the M22. Enjoy them both!

Tuesday, August 2 – As we know, the major distribution of globular clusters centers around our galactic center in the Ophiuchus/Saggitarius region. Tonight let’s explore what creates a globular cluster’s form and we’ll start with the “head of the class”, M75.

Orbiting the galactic center for billions of years, globular clusters endured a wide variety of disturbances. Their component stars escape when accelerated by mutual encounters and the tidal force of our own Milky Way pulls them apart when they are near the periapsis, or galactic center. Even close encounters with other masses, such as other clusters and nebula, can act upon them! At the same time, their stellar members are also evolving and this loss of gas can contribute to mass loss and deflation of these magnificent clusters. Although this happens far less quickly than in open clusters, our observable globular friends may only be survivors of a once larger population whose stars have been spread throughout the halo. This destruction process is never-ending, and it is believed that globular clusters will cease to exist in about 10 billion years.

Although it will be later evening when the M75 appears on the Saggitarius/Capricornus border, you will find the journey of about 8 degrees southwest of Beta Capricorni worth the wait. At magnitude 8, it can be glimpsed as a small round patch in binoculars, but a telescope is needed to see its true glory. Residing around 67,500 light years from our solar system, the M75 is one of the more remote of Messier’s globular clusters. Since it is so far from the galactic center – possibly 100,000 light years distant – the M75 has survived billions of years to remain one of the few Class I globular clusters. Although resolution is possible in very large scopes, note that this globular cluster is one of the most concentrated in the sky, with only the outlying stars resolvable to most instruments.

Wednesday, August 3 – Tonight let’s return to earlier evening skies as we continue our studies with one of the nearer to the galactic center globulars – M14. Located about sixteen degrees (less than a handspan) south of Alpha Ophiuchi, this ninth magnitude, class VIII cluster can be spotted with larger binoculars, but only fully appreciated with the telescope.

When studied spectroscopically, globular clusters are found to be much lower in heavy element abundance than stars such as own Sun. These earlier generation stars (Population II) began their formation during the birth of our galaxy, making globular clusters the oldest of formations that we can study. In comparison, the disk stars have evolved many times, going through cycles of starbirth and supernova, which in turn enriches the heavy element concentration in star forming clouds which may cause their collapse. Of course, as you may have guessed, M14 breaks the rules.

M14 contains an unusually high number of variable stars – in excess of 70 – with many of them known to be the W Virginis type. In 1938, a nova appeared in M14, but it was undiscovered until 1964 when Amelia Wehlau of the University of Ontario was surveying the photographic plates taken by Helen Sawyer Hogg. The nova was revealed on eight of these plates taken on consecutive nights and showed itself as a 16th magnitude star – and was believed to be at one time almost 5 times brighter than the cluster members. Unlike 80 years earlier with T Scorpii in the M80, actual photographic evidence of the event existed. In 1991, the eyes of the Hubble were turned its way, but the suspect star and no traces of a nebulous remnant were discovered. Then six years later, a carbon star was discovered in the M14.

To a small telescope, the M14 will offer little to no resolution and will appear almost like an elliptical galaxy, lacking in any central condensation. Larger scopes will show hints of resolution, with a gradual fading towards the cluster’s slightly oblate edges. A true beauty!

Thursday, August 4 – For viewers in the Americas, this is our “New Moon” night (11:04 pm EDT) as our nearest astronomical neighbor reaches the point of its greatest elongation (apogee) and becomes 252,669 miles distant from Earth.

As we explore globular clusters, we simply assume them all to be part of the Milky Way galaxy, but that might not always be the case. We know they are basically concentrated around the galactic center, but there may be four of them that actually belong to another galaxy. Tonight we’ll look at one such cluster being drawn into the Milky Way’s halo. Set your sights just about one and a half degrees west/south west from Zeta Saggitarii for the M54.

At around magnitude 7.6, M54 is definately bright enough to be spotted in binoculars, but its rich class III concentration is more notable in a telescope. Despite its brightness and deeply concentrated core, the M54 isn’t exactly easy to resolove. At one time we thought it to be around 65,000 light years distant and high in variables with a known number of 82 RR Lyrae types. We knew it was receeding, but when the Saggittarius Dwarf Elliptical Galaxy was discovered in 1994, we noted the M54 was receeding at almost precisely the same speed! When more accurate distances were measured, we found the M54 to coincide with the SagDEG distance of 80-90,000 light years, and the M54’s distance is now calculated at 87,400 light years. No wonder it’s hard to resolve!

Friday, August 5 – Today we celebrate the 75th birthday of Neil Armstrong, the first human to walk on the moon. Congratulations! Also on this date in 1864, Giovanni Donati made the very first spectroscopic observations of a comet (Tempel, 1864 II). His observations of three absorption lines lead to what we now know as the Swan bands, a form of molecular carbon (C2).

Our study continues tonight as we move away from the galactic center in search of remote globular cluster that can be viewed by most telescopes. As we have learned, radial velocity measurements show us the majority of globulars are involved in highly eccentric elliptical orbit – one that takes them far outside the Milky Way. This orbit forms a sort of spherical “halo” which tends to be more concentrated toward our galactic center. Reaching out several thousands of light years, this halo is actually larger than the disk of our own galaxy. Since globular clusters aren’t involved in our galaxy’s disk rotation, they may possess very high relative velocities. Tonight let’s head toward the constellation of Aquilla and look at one such globular – NGC 7006.

Located about half a fist’s width east of Gamma Aquilae, the NGC 7006 is speeding towards us at at velocity of around 215 miles per second. At 150,000 light years from the center of our galaxy, this particular globular could very well be an extra-galactic object. At magnitude 11.5, it’s not for the faint of heart, but can be spotted in scopes as small as 150mm, and requires larger aperture to look like anything more than a suggestion. Given its tremendous distance from the galactic center it’s not hard to realize this is a class I although it is quite faint. Even the largest of amateur scopes will find it unresolvable!

Saturday, August 6 – Studies continue as we look deeper into structure. As a rule, globular clusters normally contain a large number of variable stars, and most usually the RR Lyrae type such as earlier study M54. At one time they were known as “Cluster Variables” – with the amount varying from one to another. Many of them contain vast amounts of white dwarfs, some have neutron stars which are detected as pulsars, but out of all 151, only four have a very unusual member – a planetary nebula.

Tonight our studies will take us toward the emerging constellation of Pegasus and magnitude 6.5, class IV, M15. Easily located with even small binoculars about four degrees northwest of Enif, this magnificent globular cluster is a true delight in a telecope. Amoungst the globulars, the M15 ranks third in variable star population with 112 identified. As one of the most dense of clusters, it is surprising that it is considered to be only class III. Its deeply concentrated core is easily apparent, and has began the process of core collapse during its evolution. The central core itself is very small compared to the cluster’s true size and almost half the M15’s mass is contained within it. Although it has been studied by the Hubble, we still do not know if this density is caused by the component’s mutual gravity, or if it might disguise a supermassive object similar to a galactic nucleus.

M15 was the first globular cluster in which a planetary nebula, known as Pease 1, could be identified. Larger aperture scopes can easily see it at high power. Suprisingly enough, the M15 also is home to 9 known pulsars, which are neutron stars left behind from previous supernova during the cluster’s evolution – one of which is a double neutron star. While total resolution is impossible, a handful of bright stars can be picked out against that magnificent core region and wonderful chains and streams of members await your investigation tonight!

Sunday, August 7 – On this date in 1959, Explorer 6 became the first satellite to transmit photographs of the Earth from its orbit.

Wait until the Moon has began to set tonight and let’s return again to look at two giants so we might compare roughly equal sizes, but not equal class. To judge them fairly, you must use the same eyepiece. Start first by re-locating previous study M4. This is a class IX globular cluster. Notice the powder-like qualities. It might be heavily populated, but it is not dense. Now return to previous study M13. This is a class V globular cluster. Most telescopes will make out at least some resolution and a distinct core region. It is the level of condensation that creates class. It is no different than judging magnitudes and simply takes practice. Try your hand at the M55 along the bottom of the Saggitarius “teapot” – it’s a class XI. Although it is a full magnitude brighter than the class I, M75 that we looked at earlier in the week, can you tell the difference in concentration? For those with GoTo systems, take a quick hop through Ophiuchus and look at the difference between NGC 6356 (class II) and NGC 6426 (class IX). If you want to try one that they can’t even class? Look no further the M71 in Sagitta. It’s all a wonderful game and the most fun comes from learning!

In the mean time, don’t forget all those other wonderful globular clusters such as 47 Tucanae, Omega Centauri, M56, M92, M28 and a host of others! May all your journeys be at light speed…~Tammy Plotner

Quark-Gluon Plasma Created

Degree of interaction among quarks in liquid gold-gold collisions. Image credit: RHIC Click to enlarge
Using high-speed collisions between gold atoms, scientists think they have re-created one of the most mysterious forms of matter in the universe — quark-gluon plasma. This form of matter was present during the first microsecond of the Big Bang and may still exist at the cores of dense, distant stars.

UC Davis physics professor Daniel Cebra is one of 543 collaborators on the research. His main role was building the electronic listening devices that collect information about the collisions, a job he compared to “troubleshooting 120,000 stereo systems.”

Now, using those detectors, “we look for trends in what happened during the collision to learn what the quark-gluon plasma is like,” he said.

“We have been trying to melt neutrons and protons, the building blocks of atomic nuclei, into their constituent quarks and gluons,” Cebra said. “We needed a lot of heat, pressure and energy, all localized in a small space.”

The scientists produced the right conditions with head-on collisions between the nuclei of gold atoms. The resulting quark-gluon plasma lasted an extremely short time — less than 10-20 seconds, Cebra said. But the collision left tracings that the scientists could measure.

“Our work is like accident reconstruction,” Cebra said. “We see fragments coming out of a collision, and we construct that information back to very small points.”

Quark-gluon plasma was expected to behave like a gas, but the data shows a more liquid-like substance. The plasma is less compressible than expected, which means that it may be able to support the cores of very dense stars.

“If a neutron star gets large and dense enough, it may go through a quark phase, or it may just collapse into a black hole,” Cebra said. “To support a quark star, the quark-gluon plasma would need rigidity. We now expect there to be quark stars, but they will be hard to study. If they exist, they’re semi-infinitely far away.”

The project is led by Brookhaven National Laboratory and Lawrence Berkeley National Laboratory, with collaborators at 52 institutions worldwide. The work was done in Brookhaven’s Relativistic Heavy Ion Collider (RHIC).

Original Source: UC Davis News Release

Is Methane Evidence of Life on Mars?

Mars. Image credit: NASA Click to enlarge
Are microbes making the methane that’s been found on Mars, or does the hydrocarbon gas come from geological processes? It’s the question that everybody wants to answer, but nobody can. What will it take to convince the jury?

Many experts told Astrobiology Magazine that the best way to judge whether methane has a biological origin is to look at the ratio of carbon-12 (C-12) to carbon-13 (C-13) in the molecules. Living organisms preferentially take up the lighter C-12 isotopes as they assemble methane, and that chemical signature remains until the molecule is destroyed.

“There may be a way of distinguishing the origin of methane, whether biogenic or not, by using stable isotope measurements,” says Barbara Sherwood Lollar, an isotope chemist at the University of Toronto.

But isotope signals are subtle, best performed by accurate spectrometers placed on the martian surface rather than on an orbiting spacecraft orbit.

And there are complications. For one thing, an average martian methane level of 10 parts per billion (ppb) may be too faint for accurate isotope measurement, even for a spectroscope placed on Mars. Also, the C-12 to C-13 ratio of methane alone is not always proof of life. For example, the “Lost City” hydrothermal vent field in the Atlantic Ocean did not show a clear isotope signature, says James Kasting, professor of earth and mineral science at Penn State University.

“The methane is not that strongly fractionated, but they still think it might be biological,” says Kasting. “At Lost City, you can’t figure out if it’s biological or not by the isotopes. How are we going to figure that out on Mars?”

By expanding the search, responds Sherwood Lollar. Instead of measuring only carbon, she suggests measuring hydrogen isotopes, because biological systems also prefer hydrogen (H) to the heavier deuterium (2H).

A second approach would look at the longer, heavier hydrocarbons — ethane, propane and butane — that are related to methane, and that sometimes appear with biogenic or abiogenic methane. Sherwood Lollar detected these hydrocarbons while investigating abiogenic methane trapped in pores in ancient rocks in the Canadian Shield, a large deposit of Precambrian igneous rock. “When the water gets trapped over very, very long time periods,” she says, an abiogenic reaction between water and rock makes methane, ethane, propane and butane.

If the longer-chain abiogenic hydrocarbons are ever detected in the martian atmosphere, how could we distinguish them from similar hydrocarbons that are the breakdown products of kerogen, a remnant of decomposing living matter? The answer, Sherwood Lollar repeats, could be found in the isotopes. Abiogenic hydrocarbon chains would contain a higher proportion of heavier isotopes than the hydrocarbon chains derived from the breakdown of kerogen.

“Future missions to Mars plan to look for the presence of higher hydrocarbons as well as methane,” Sherwood Lollar says. “If this isotopic pattern can be identified in martian methane and ethane for instance, then this type of information could help resolve abiogenic versus biogenic origin.”

Isotopes figure prominently in several upcoming space missions that could slake the growing thirst for evidence on the methane mystery:

* The Phoenix lander, scheduled for launch in August 2007, will go to an ice-rich region near the North Pole, and “dig up dirt and analyze the dirt, along with the ice,” says William Boynton of the University of Arizona, who will direct the mission. The lander’s mass spectrometer will measure isotopes in any methane trapped in the soil, if the concentration is sufficient. “We won’t be able to measure the isotope ratio [in the atmosphere], because it won’t be a high enough concentration,” Boynton says.

* Mars Science Laboratory, scheduled for launch sometime between 2009 and 2011, is a 3,000-kilogram, six-wheel rover packed with scientific instruments. The tunable laser spectrometer and mass spectrometer-gas chromatograph may both be able to ferret out isotope ratios of carbon and other elements.

* Beagle 3, a successor to Britain’s lost-in-space Beagle 2, may carry an improved mass spectrometer capable of measuring carbon isotope ratios, but the project has yet to be approved. The craft would not launch until at least 2009.

From these launch dates, it’s clear the jury on this who-dun-it must remain sequestered for years, until hard data on the source of methane on Mars can be aired in the scientific courtroom. At this point, it’s fair to say that many expert witnesses take the possibility of a biogenic source rather seriously. For example, Vladimir Krasnopolsky, who led one of the teams that found methane on the planet, says, “Bacteria, I think, are plausible sources of methane on Mars, the most likely source.” But he expects the microbes to be found in oases, “because the martian conditions are very hostile to life. I think these bacteria may exist in some locations where conditions are warm and wet.”

That observation points to a possible win-win situation for those who want to find life on Mars, says Timothy Kral of the University of Arkansas, who grows methanogens for a living. If, as calculations suggest, asteroids and comets are not a likely to be delivering methane to Mars, then either methane-making organisms must be living in the subsurface, or there is a place where it’s warm enough for abiogenic generation.

“Even though it is not an indication of life directly, it’s an indication that there is warming,” says Kral. In those conditions, “there is heat, energy for organisms to grow.”

A lot has changed in the past year. Kral, who has spent a dozen years growing methanogens in a simulated martian environment, says, “Prior to last year, when people asked if I thought there was life on Mars, I would giggle. I would not be in this business if I did not think it was possible, but there was no real evidence for any life. Then, all of a sudden, last year, they found methane in the atmosphere, and we suddenly have a piece of real scientific evidence saying that it’s possible” that Mars is the second living planet.

Original Source: NASA Astrobiology

10th Planet Discovered

This new planet is larger than Pluto. Image credit: NASA/JPL. Click to enlarge.
A planet larger than Pluto has been discovered in the outlying regions of the solar system.

The 10th planet was discovered using the Samuel Oschin Telescope at Palomar Observatory near San Diego, Calif. The discovery was announced today by planetary scientist Dr. Mike Brown of the California Institute of Technology in Pasadena, Calif., whose research is partly funded by NASA.

The planet is a typical member of the Kuiper belt, but its sheer size in relation to the nine known planets means that it can only be classified as a planet, Brown said. Currently about 97 times further from the sun than the Earth, the planet is the farthest-known object in the solar system, and the third brightest of the Kuiper belt objects.

“It will be visible with a telescope over the next six months and is currently almost directly overhead in the early-morning eastern sky, in the constellation Cetus,” said Brown, who made the discovery with colleagues Chad Trujillo, of the Gemini Observatory in Mauna Kea, Hawaii, and David Rabinowitz, of Yale University, New Haven, Conn., on January 8.

Brown, Trujillo and Rabinowitz first photographed the new planet with the 48-inch Samuel Oschin Telescope on October 31, 2003. However, the object was so far away that its motion was not detected until they reanalyzed the data in January of this year. In the last seven months, the scientists have been studying the planet to better estimate its size and its motions.

“It’s definitely bigger than Pluto,” said Brown, who is a professor of planetary astronomy.

Scientists can infer the size of a solar system object by its brightness, just as one can infer the size of a faraway light bulb if one knows its wattage. The reflectance of the planet is not yet known. Scientists can not yet tell how much light from the sun is reflected away, but the amount of light the planet reflects puts a lower limit on its size.

“Even if it reflected 100 percent of the light reaching it, it would still be as big as Pluto,” says Brown. “I’d say it’s probably one and a half times the size of Pluto, but we’re not sure yet of the final size.

“We are 100 percent confident that this is the first object bigger than Pluto ever found in the outer solar system,” Brown added.

The size of the planet is limited by observations using NASA’s Spitzer Space Telescope, which has already proved its mettle in studying the heat of dim, faint, faraway objects such as the Kuiper-belt bodies. Because Spitzer is unable to detect the new planet, the overall diameter must be less than 2,000 miles, said Brown.

A name for the new planet has been proposed by the discoverers to the International Astronomical Union, and they are awaiting the decision of this body before announcing the name.

The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA.

For more information and images see: http://www.nasa.gov/vision/universe/solarsystem/newplanet-072905-images.html

or http://www.astro.caltech.edu/palomarnew/sot.html

For information about NASA and agency programs on the Web, visit:

http://www.nasa.gov/home/index.

Original Source: NASA/JPL News Release

Supernova, Before and After

Supernova (SN) 2005cs in M51. Image credit: Hubble Click to enlarge
A series of lucky breaks has allowed two University of California, Berkeley, astronomers to track down the identity of a distant star that lit up the majestic Whirlpool Galaxy a month ago.

While astronomers can predict which stars will end their lives in a fiery explosion, surprisingly only five supernovas before now had been traced back to a known star, according to one of the astronomers, UC Berkeley astronomy professor Alex Filippenko. Most supernovas are too distant, or their progenitor stars too faint or in too crowded fields for astronomers to look back in historical sky photos in order to pinpoint the location and type of star.

The Space Telescope Science Institute (STScI) today (Thursday, July 28) released photos of the beautiful Whirlpool Galaxy, M51, showing the location of the original star and the bright supernova just 12 days after its explosion was discovered.

The supernova, dubbed SN 2005cs, belongs to a class of exploding stars called “Type II-plateau.” A supernova of this type results from the collapse and subsequent explosion of a massive star whose light remains at a constant brightness (a “plateau”) for a period of time.

This finding is consistent with the idea that the progenitors of supernova explosions are red, supergiant stars with masses eight to 15 times the sun’s mass. The progenitor star of SN 2005cs was found to be at the low end of the mass range for supernova explosions. Stars with masses lower than eight solar masses do not explode as supernovae at all, but rather blow off their outer atmospheres to become planetary nebulae before contracting to white dwarfs.

A German amateur astronomer was the first to note the unusually bright star – perhaps a supernova – in M51, and he asked the staff at the Central Bureau for Astronomical Telegrams to post a note to that effect on June 29. Filippenko, who specializes in supernovae and black holes, received the notice late that afternoon and rushed to get one of his former students to request a spectrum of the brightly burning star from a telescope in Arizona. This spectrum confirmed that it was a Type II supernova.

Filippenko, by chance, was at the very end of a year-long observational program using the Hubble Space Telescope, and he worked during an overnight flight and early the next morning to submit a request to observe the supernova before his opportunity ended at 5 p.m. Eastern time June 30. Since Hubble can easily resolve stars in nearby galaxies, such as the Whirlpool, it was the only chance he had to track down the exploding star’s identity. The new picture was needed for comparison with archival images in order to accurately determine the position of the supernova.

He got in under the wire, convincing the telescope crew to observe the waning supernova on July 11, amidst the hoopla and frequent observations of the Deep Impact probe’s collision with comet Temple I.

“This will be one of Hubble’s many legacies,” Filippenko said. “No other telescope program could observe the exact location of this Type II supernova, yet it was an opportunity not to be missed.”

From the brand new Hubble image and a January 2005 image Hubble had taken of the Whirlpool Galaxy, UC Berkeley research astronomer Weidong Li and Filippenko were able to pinpoint the location of the progenitor star and identify it as a red supergiant whose mass is about seven to 10 times that of the sun.

“This is a great example of the excitement of science, when something happens and you have to jump on it right away,” said Filippenko, who is known for the enthusiasm he brings to teaching. “Some nights you just don’t sleep.”

Filippenko, Li and colleague Schuyler Van Dyk of Caltech’s Spitzer Science Center first reported their findings in IAU circulars 8556 and 8565 on July 3 and July 12, respectively. The team submitted a full paper describing their research to The Astrophysical Journal on July 18.

The Space Telescope Science Institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc., under contract with the Goddard Space Flight Center, Greenbelt, Md. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency.

Original Source: UC Berkeley News Release

Super Climate Simulation Models Oceans, Ice, Land and Atmosphere

Image depicts the sea surface temperature. Image credit: Shep Smithline, GFDL; Chris Hill, MIT. Click to enlarge
Researchers from MIT, NASA’s Goddard Space Flight Center and several other government and academic institutions have created four new supercomputer simulations that for the first time combine mathematical computer models of the atmosphere, ocean, land surface and sea ice.

These simulations are the first field tests of the new Earth System Modeling Framework (ESMF), an innovative software system that promises to improve predictive capability in diverse areas such as short-term weather forecasts and century-long climate-change projections.

Although still under development, groups from NASA, the National Science Foundation, the National Oceanic and Atmospheric Administration (NOAA), the Department of Energy, the Department of Defense and research universities are using ESMF as the standard for coupling their weather and climate models to achieve a realistic representation of the Earth as a system of interacting parts.

ESMF makes it easier to share and compare alternative scientific approaches from multiple sources; it uses remote sensing data more efficiently and eliminates the need for individual agencies to develop their own coupling software.

“The development of large Earth system applications often spans initiatives, institutions and agencies, and involves the geoscience, physics, mathematics and computer science communities. With ESMF, these diverse groups can leverage common software to simplify model development,” said NASA’s Arlindo da Silva, a scientist in Goddard’s Global Modeling and Assimilation Office.

The newly completed field tests, known as interoperability experiments, show that the new approach can be successful. Although most of the experiments would require exhaustive tuning and validation to be scientifically sound, they already show that ESMF can be used to assemble coupled applications quickly, easily and with technical accuracy.

The MIT experiment combines an atmosphere-land-ice model from NOAA’s Geophysical Fluid Dynamics Laboratory with an MIT ocean-sea ice model known as MITgcm (http://mitgcm.org/). This may ultimately bring new insights into ocean uptake of carbon dioxide and other atmospheric gases and information on how this process affects climate. Christopher Hill, principal research scientist in the MIT Department of Earth, Atmospheric and Planetary Sciences, and a member of the MIT Climate Modeling Iniatiative, led development of the software at MIT.

The ESMF research team plans to release the software to the scientific community via the Internet later this month.

Original Source: MIT News Release

Mimas and Tethys Circling Saturn

Tethys and Mimas circling Saturn. Image credit: NASA/JPL/SSI. Click to enlarge
Far above the howling winds of Saturn, its icy moons circle the planet in silence. Mimas is seen near the upper right, while Tethys hovers at the bottom. Dark shadows cast by the see-through rings slice across the northern hemisphere. Mimas is 397 kilometers (247 miles) across. Tethys is 1,071 kilometers (665 miles) across.
The dark, doughnut-shaped storm near the south pole is at least 1,600 kilometers (1,000 miles) across and could easily swallow any of Saturn’s moons except giant Titan (5,150 kilometers, 3,200 miles across).

The image was taken with the Cassini spacecraft wide-angle camera on June 21, 2005, through a filter sensitive to wavelengths of infrared light centered at 752 nanometers at a distance of approximately 2.2 million kilometers (1.3 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 53 degrees. The image scale is 125 kilometers (78 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 team is based at the Space Science Institute, 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