Green Laser - something to know

Many of us use the green laser as a very useful tool in star parties and in teaching newbies to learn the constellations. But there are certain things one should know about the dangers involved with this useful "toy". Here is a link which tells us how much dangerous it can be.

http://www.skyandtelescope.com/community/skyblog/observingblog/99956999.html

Let us take care to use this useful instrument safely!

Identifying Exoplanets by Their Dust Tails

Are we losing the Sahara to space? No, is the simple answer to that. The Earth has a trail of dust behind it but the dust is interstellar dust which is already present in the solar system. This interplanetary dust comes from the fragments of comets and asteroids that have collided. As the Earth travels through this dust the dust is disturbed and leaves what looks like a trail are behind it.

There is another way of looking at the formation of the dust tail. The Earth leaves behind it an area of almost suction like quality that sucks the dust in from the edges giving the appearance of a dust tail. The dust tail is pulled along by gravity and leaves a trail around the sun.

The Spitzer telescope found the dust tail a few months ago as it went straight through it. This has allowed the dust tail to be mapped and shows how the tail can give an indication of a planet. Distant exoplanets around stars many light years from our own can be indicated by strange features drawn in the dust tail by these planets. These features can be bumps, warps, rings and offsets.

The dust has already been followed in other planetary systems other than our own. About 20 dust discs have been seen and have led to a few planets already being found. One of these was found around a star called Formalhaut.

These dust tails will help the future James Webb space telescope to hunt for extra solar planets and hopefully find them quicker.

Shedding 'Bent' Light on Dark Matter

This is one of the most detailed maps of dark matter in our universe ever created. The location of the dark matter (tinted blue) was inferred through observations of magnified and distorted distant galaxies seen in this picture. Image credit: NASA/JPL-Caltech/ESA/Institute of Astrophysics of Andalusia, University of Basque Country/JHU

Astronomers using NASA's Hubble Space Telescope took advantage of a giant cosmic magnifying glass to create one of the sharpest and most detailed maps of dark matter in the universe. Dark matter is an invisible and unknown substance that makes up the bulk of the universe's mass. Astronomer Dan Coe led the research while working at NASA's Jet Propulsion Laboratory in Pasadena, Calif.; he is currently with the Space Telescope Science Institute in Baltimore, Md.

The astronomers used Hubble to chart the invisible matter in the massive galaxy cluster Abell 1689, located 2.2 billion light-years away. The cluster's gravity, the majority of which comes from dark matter, acts like a cosmic magnifying glass, bending and amplifying the light from distant galaxies behind it. This effect, called gravitational lensing, produces multiple, warped, and greatly magnified images of those galaxies, like the view in a funhouse mirror. By studying the distorted images, astronomers estimated the amount of dark matter within the cluster.

The new dark matter observations may yield new insights into the role of dark energy in the universe's early formative years. A mysterious property of space, dark energy fights against the gravitational pull of dark matter. The new results suggest that galaxy clusters may have formed earlier than expected, before the push of dark energy inhibited their growth. Dark energy pushes galaxies apart from one another by stretching the space between them, suppressing the formation of giant structures called galaxy clusters. One way astronomers can probe this primeval tug-of-war is by mapping the distribution of dark matter in clusters.

Read the full story at http://hubblesite.org/newscenter/archive/releases/2010/37/full/ .

The California Institute of Technology in Pasadena manages JPL for NASA.

Status Update: Cassini to Resume Nominal Operations

Artist's concept of NASA's Cassini spacecraft at Saturn. Image credit: NASA/JPL-Caltech 

November 09, 2010

Engineers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., expect the Cassini spacecraft will resume normal operations on Nov. 24. They have traced the steps taken by an onboard computer before Cassini put itself in precautionary "safe mode" last week.

Mission managers determined that the spacecraft went into safe mode because of a flip of a bit in the command and data system computer. The bit flip prevented the computer from registering an important instruction, and the spacecraft, as programmed, went into the standby mode. Engineers are still working to understand why the bit flipped.

Since the spacecraft went into safe mode on Nov. 2, the onboard computer with the bit flip has been reset and one of the science instruments has been turned back on to keep it warm. Over the next week or so, engineers will bring the rest of the science instruments back online.

Playback from the computer's memory is enabling engineers to extract science data collected before the spacecraft entered safe mode. The flow of science data is expected to resume when the instruments are powered back on next week.

"The bit flip happened in exactly the wrong location -- almost any place else would have merely resulted in a rejected command -- but the spacecraft responded exactly as programmed," said Bob Mitchell, Cassini program manager at JPL. "Cassini is in excellent shape, and we are looking forward to the next seven years of this mission."

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.

More Cassini information is available at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Cassini's CIRS Reveals Saturn Is on a Cosmic Dimmer Switch

Heat emitted from the interior of Saturn (red) shows up in this false-color image of Saturn, made from data taken in 2008 by Cassini's visual and infrared mapping spectrometer. Credit:NASA/JPL/ASI/University of Arizona


Like a cosmic light bulb on a dimmer switch, Saturn emitted gradually less energy each year from 2005 to 2009, according to observations by NASA’s Cassini spacecraft. But unlike an ordinary bulb, Saturn's southern hemisphere consistently emitted more energy than its northern one. On top of that, energy levels changed with the seasons and differed from the last time a spacecraft visited in the early 1980s. These never-before-seen trends came from an analysis of comprehensive data from the Composite Infrared Spectrometer (CIRS), an instrument built by NASA's Goddard Space Flight Center in Greenbelt, Md., as well as a comparison with earlier data from NASA's Voyager spacecraft. When combined with information about the energy coming to Saturn from the sun, the results could help scientists understand the nature of Saturn's internal heat source.

The findings were reported November 9 in the Journal of Geophysical Research-Planets by Liming Li of Cornell University in Ithaca, N.Y. (now at the University of Houston), and colleagues from several institutions, including Goddard and NASA's Jet Propulsion Laboratory in Pasadena Calif., which manages the Cassini mission. "The Cassini CIRS data are very valuable because they give us a nearly complete picture of Saturn," says Li. "This is the only single data set that provides so much information about this planet, and it's the first time that anybody has been able to study the power emitted by one of the giant planets in such detail."

The planets in our solar system lose energy in the form of heat radiation in wavelengths that are invisible to the human eye. The CIRS instrument picks up wavelengths in the thermal infrared region, which is beyond red light, where the wavelengths correspond to heat emission.

"In planetary science, we tend to think of planets as losing power evenly in all directions and at a steady rate," says Li. "Now we know Saturn is not doing that." (Power is the amount of energy emitted per unit of time.)

Instead, Saturn's flow of outgoing energy was lopsided, with its southern hemisphere giving off about one-sixth more energy than the northern one, Li explains. This effect matched Saturn's seasons: during those five Earth years, it was summer in the southern hemisphere and winter in the northern one. (A season on Saturn lasts about seven Earth years.) Like Earth, Saturn has these seasons because the planet is tilted on its axis, so one hemisphere receives more energy from the sun and experiences summer while the other receives less energy and is shrouded in winter. Saturn’s equinox, when the sun was directly over the equator, occurred in August 2009.

In the study, Saturn's seasons looked Earth-like in another way: in each hemisphere, its effective temperature, which characterizes its thermal emission to space, started to warm up or cool down as a change of season approached. Because Saturn's weather is variable and the atmosphere tends to retain heat (called heat inertia), the temperature changes in complicated ways throughout the atmosphere. "The effective temperature provides us a simple way to track the response of Saturn's atmosphere, as a system, to the seasonal changes," says Li. Cassini's observations in the northern hemisphere revealed that the effective temperature gradually dropped from 2005 to 2008 and then started to warm up again by 2009. In Saturn's southern hemisphere, the effective temperature cooled from 2005 to 2009, as the equinox started to approach.

The emitted energy for each hemisphere rose and fell along with the effective temperature. Even so, during this five-year period, the planet as a whole seemed to be slowly cooling down and emitting less energy.

To find out if similar changes were happening one Saturn year ago, the researchers looked at data collected by Voyager in 1980 and 1981. Like Cassini CIRS, Voyager recorded fluctuations in the energy emitted by the planet and in the effective temperature. But Voyager did not see the imbalance between the southern and northern hemispheres; instead, the two regions were much more consistent with each other.

Why wouldn't Voyager have seen the same summer-versus-winter difference between the two hemispheres? The amount of energy coming from the sun (called solar radiance), which drives weather and atmospheric temperatures, could have fluctuated from one Saturn year to the next. The patterns in Saturn's cloud cover and haze could have, too.

"It's reasonable to think that the changes in Saturn's emitted power are related to cloud cover," says Amy Simon-Miller, who heads the Planetary Systems Laboratory at Goddard and is a co-author on the paper. "As the amount of cloud cover changes, the amount of radiation escaping into space also changes. This might vary during a single season and from one Saturn year to another. But to fully understand what is happening on Saturn, we will need the other half of the picture: the amount of power being absorbed by the planet."

Li is finishing an analysis of the solar energy that came to Saturn, based on data sets collected by two other Cassini instruments, the imaging science subsystem and the visual and infrared mapping spectrometer. He agrees that this information is crucial because Saturn, like its fellow giant planets Jupiter and Neptune, is thought to have its own source of internal energy. (The fourth giant planet, Uranus, does not seem to have an internal source.) By studying the changes in Saturn's outgoing energy along with the changes in incoming solar energy, scientists can learn about the nature of the planet's internal energy source and whether it, too, changes over time.

"The differences between Saturn's northern and southern hemisphere and that fact that Voyager did not see the same asymmetry raise a very important question: does Saturn's internal heat vary with time?" says Li. "The answer will significantly deepen our understanding of the weather, internal structure and evolution of Saturn and the other giant planets."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., 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 composite infrared spectrometer team is based at NASA Goddard, where the instrument was built.

More Cassini information is available at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

Elizabeth Zubritsky
NASA's Goddard Space Flight Center, Greenbelt, Md.

ω Centauri’s Red Giants Confirm Stellar Evolution Models

As the get older, Sun-like stars become red giants and shed mass. Image Credit: ESO/S. Steinhofel

While science education often focuses on teaching the scientific method (or at least tries to), the real process of science is often far less linear. Theories tie together so many points of data, that making singular predictions that confirm or refute a proposition is often challenging. Such is the case for stellar evolution. The understanding is woven together from so many independent pieces, that the process is more of a roaring sea than a directed river.

Realizing this, I’ve been keen on instances in which necessary predictions are observationally confirmed later. A new study, led by Mariela Vieytes from the University of Buenos Aires and accepted in an upcoming publication of Astronomy & Astrophysics, does just that by demonstrating one of the necessary conditions for predictions of post main sequenceevolution. Specifically, astronomers need to establish that stars undergo significant amounts of mass loss (~0.1-0.3 M_☉) during their red giant branch evolution. This requirement was set forth as part of the expected behavior necessary to explain: “i) the very existence of the horizontal branch (HB) and its morphology, ii) the pulsational properties of RR Lyrae stars, iii) the absence of asymptotic giant branch (AGB) stars brighter than the red giant branch (RGB) tip, and the chemistry and characteristics in the AGB, post-AGB and planetary nebulaevolutionary phases, iv) the mass of white dwarf (WD) stars.”

Astronomers expected to find confirmation of this mass loss by detecting gas congregating in the cores of globular clusters after being shed by stars evolving along the RGB. Yet searches for this gas came up mostly empty. Eventually astronomers realized that gas would be stripped relatively quickly as globular clusters plunged through the galactic plane. But this left them with the need to confirm the prediction in some other manner.

One way to do this is to look at the stars themselves. If they show velocities in their photospheres greater than the escape velocity, they will lose mass. Just how much higher will determine the amount of mass lost. By analyzing the Doppler shift of specific absorption lines of several stars in the cluster ω Centauri, the team was able to match the amount of mass being lost to predictions from evolutionary models. From this, the team concluded that their target stars were losing between the rates of mass loss are estimated as a few 10^-9 and 10^-10M_☉ yr^-1. This is in general agreement with the predictions set forth by evolutionary models.

Cool Star is a Gem of a Find

That green dot in the middle of this image might look like an emerald amidst glittering diamonds, but it is actually a dim star belonging to a class called brown dwarfs. This particular object is the first ultra-cool brown dwarf discovered by WISE. Image credit: NASA/JPL-Caltech/UCLA 

November 09, 2010

NASA's Wide-field Infrared Survey Explorer, or WISE, has eyed its first cool brown dwarf: a tiny, ultra-cold star floating all alone in space.

WISE is scanning the whole sky in infrared light, picking up the glow of not just brown dwarfs but also asteroids, stars and galaxies. It has sent millions of images down to Earth, in which infrared light of different wavelengths is color-coded in the images.

"The brown dwarfs jump out at you like big, fat, green emeralds," said Amy Mainzer, the deputy project scientist of WISE at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Mainzer, who makes jewelry in her spare time, explained that the brown dwarfs appear like green gems in WISE images because the methane in their atmospheres absorbs the infrared light that has been coded blue, and because they are too faint to give off the infrared light that is color-coded red. The only color left is green.

Like Jupiter, brown dwarfs are made up of gas -- a lot of it in the form of methane, hydrogen sulfide, and ammonia. These gases would be deadly to humans at the concentrations found around brown dwarfs. And they wouldn't exactly smell pretty.

"If you could bottle up a gallon of this object's atmosphere and bring it back to Earth, smelling it wouldn't kill you, but it would stink pretty badly -- like rotten eggs with a hint of ammonia," said Mainzer.

Mainzer and other members of the WISE team are already accumulating a quarry of brown dwarf candidates similar to this one. Brown dwarfs have masses somewhere between those of a star and a planet. They start out like stars as collapsing balls of gas, but they lack the mass to fuse atoms together at their core and shine with starlight. As time goes on, these lightweights cool off, until they can only be seen in infrared light. There could be many such objects lurking in the neighborhood of our sun, but astronomers know of only a handful so far. WISE is expected to find hundreds, including the coolest and closest of all.

To scientists, brown dwarfs represent the perfect laboratories for studying planet-like atmospheres.

"They're a great test of our understanding of atmospheric physics of planets, since they don't have solid surfaces, and there's no big, bright sun to get in the way," said co-author Michael Cushing, a postdoctoral fellow at JPL.

WISE's new brown dwarf is named WISEPC J045853.90+643451.9 for its location in the sky. It is estimated to be 18 to 30 light-years away and is one of the coolest brown dwarfs known, with a temperature of about 600 Kelvin, or 620 degrees Fahrenheit. That's downright chilly as far as stars go. The fact that this brown dwarf jumped out of the data so easily and so quickly -- it was spotted 57 days into the survey mission -- indicates that WISE will discover many, many more. The discovery was confirmed by follow-up observations at the University of Virginia's Fan Mountain telescope, the Large Binocular Telescope in southeastern Arizona, and NASA's Infrared Telescope Facility on Mauna Kea, Hawaii. The results are in press at the Astrophysical Journal.

Read more about how NASA's Spitzer Space Telescope and WISE are hunting down the coldest brown dwarfs.

JPL manages the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., 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. More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu.

How Afraid of Asteroids Should You Be?

"Every man is free to rise as far as he's able or willing, but the degree to which he thinks determines the degree to which he'll rise." -Ayn Rand
We're all aware that one of the ways that human life on Earth could end, conceivably, is the same way that the dinosaurs went down.

And asteroid tracking and deflection technology is fast becoming one of the hot issues of the day. It appears so often in the news that you'd think we are at a high risk, any day, of being hit by a catastrophic asteroid.

But -- and my opinion here definitely runs against the mainstream -- I think this hysteria is absolutely ridiculous. One of the things you almost never hear about are the frequency and the odds of an asteroid strike harming you. If large asteroid strikes happened every few decades, we'd have something legitimate to prepare for and worry about. But if you've only got a one-in-a-million chance of an asteroid harming you over your lifetime -- meaning you are over 100 times more likely to be struck by lightning than harmed by an asteroid -- perhaps there are better ways to spend your resources.

Read more-www.portal to the universe.com