New type of dust in Martian atmosphere discovered

A group of French and Russian scientists, including three specialists from Moscow Institute of Physics and Technology, has discovered a new peculiarity of the Martian atmosphere.

The scientists had analyzed satellite-acquired data and concluded that the dust particles in the planet's atmosphere can be of two types.

The scientific article which presents the results of the research in detail has been published in Icarus.

The Russian contributors to the research, Anna Fedorova, Alexander Rodin and Oleg Korablev, are the specialists of MIPT and SRI (IKI) RAS.

These scientists and their French colleagues from the Paris Observatory and LATMOS research laboratory have carried out a simultaneous analysis of the ultraviolet and infrared atmospheric extinctions from SPICAM, the spectrometer on the board of the orbital station Mars Express.

The results were received during the solar occultations at the beginning of Northern summer on Mars.

Before the Sun is completely eclipsed by the planetary disk, its rays pierce through the atmosphere and then get "caught" by the spectrometer's detector.

Having gone through the atmosphere, the solar rays show a different spectrum with the changes hinting at the atmosphere's makeup, the amount of various aerosols and the size of their particles.

This method was applied to understand the way the particles are distributed in the atmosphere.

The researchers have found out that the dust particles in the Martian atmosphere are not homogeneous, but can be roughly grouped into two modes.

• The first – coarser - mode is represented by both H2O ice grains with the average radius of 1.2 μm, and slightly smaller dust particles (R = 0.7 μm).
• The second mode is a lot finer, it is an aerosol which consists of much smaller particles with a radius of 0.04–0.07 μm.

Interestingly, the density number of the both modes is not that high. Even in the most "dusty" layers of the planet's atmosphere at altitudes of 20–30 km there are about 3.000 particles of the finer mode per 1 cm³, and not more than 2 particles of the coarser mode per 1 cm³.

If compared with what is considered the norm on Earth, the air with such dust density is rather clean (rooms are usually a lot dustier); yet, aerosols are important because they, according to the scientists, play a key role in forming the planet's climate.

Because of fine dust particles in the higher layers of the atmosphere, ice "embryos" are formed faster, which, in turn, influences clouds' build-up. The clouds are responsible for both precipitation and temperature condition on the planet's surface.

Analyzing the way the dust is spread in the atmosphere of the planet with regard to the altitude and geographical coordinates is crucial for forming the full picture of what is happening on Mars.

Besides that, the dust modes which the scientists have discovered confirm that Martian dust storms ("dust devils") are able to lift large quantities of substance from the planet's surface.

The researchers point out that the fact of fine dust presence in the atmosphere can contradict the previously obtained data on the existence of the supersaturated steam at the same altitude.

More information: Icarus, www.sciencedirect.com/science/… ii/S0019103513005332

New type of black-hole quasar discovered

Illustration of another theory, showing the gas of a quasar rotating around a black hole. Credit: York University

Like our Milky Way, every known large galaxy has at its center a supermassive black hole, some of which are surrounded by a super-bright disk of hot gas called a quasar—but now a research team that includes Penn State astronomers has discovered a surprising new class of quasars in distant galaxies that even the most current theories had not predicted.

"The gas in this new type of quasar is moving in two directions: some is moving toward Earth but most of it is moving at high velocities away from us, possibly toward the quasar's black hole," said study co-author Niel Brandt, Distinguished Professor of Astronomy and Astrophysics at Penn State University.

"Just as you can use the Doppler shift for sound to tell if an airplane is moving away from you or toward you, we used the Doppler shift for light to tell whether the gas in these quasars is moving away from Earth or toward these distant black holes, which have a mass from millions to billions of times that of the Sun." Brandt explained.

Matter around these black holes forms a quasar disc that is bigger than Earth's orbit around the Sun and hotter than the surface of the Sun. These quasars generate enough light to be seen across the observable universe.

The international research team, led by Patrick Hall of York University in Toronto, Canada, discovered the unusual quasars with data from a large sky survey, the Sloan Digital Sky Survey (SDSS-III).

"Matter falling into black holes may not sound surprising," says Hall, "but what we found is, in fact, quite mysterious and was not predicted by current theories."

Such gas is found in only about 1 out of 10,000 quasars, and only seventeen cases now are known.

This discovery is detailed in a peer-reviewed paper in this month's issue of the journal Monthly Notices of the Royal Astronomical Society, published by Oxford University Press.

In addition to Brandt, the Penn State coauthors of this paper include Graduate Student Nurten Filiz Ak and Distinguished Professor of Astronomy and Astrophysics Donald Schneider, who also is the Survey Coordinator and Scientific Publication Coordinator for SDSS-III.

The two specific research components of the Sloan Digital Sky Survey that were used to make this discovery are the SDSS Legacy survey and the SDSS-III Baryon Oscillation Spectroscopic Survey.

"The gas in the disc must eventually fall into the black hole to power the quasar, but what is often seen instead is gas blown away from the black hole by the heat and light of the quasar, heading toward us at velocities up to 20 per cent of the speed of light," Hall said.

"If the gas is falling into the black hole, then we don't understand why it's so rare to see infalling gas. There's nothing else unusual about these quasars. If gas can be seen falling into them, why not in other quasars?"

Hall said there is one other possible explanation for these objects. "It could be that the gas moving away from us is not falling into the black hole but is orbiting around it, just above the disc of hot gas, and is very gradually being pushed away from the black hole. A wind like that will show gas moving both toward us and away from us.

To make an analogy: imagine an ant on a spinning merry-go-round, crawling from the center to the edge. You will see the ant moving toward you about half the time and away from you about half the time.

The same idea could apply to the gas in these quasars. In either case, the gas in these quasars is moving in an unusual fashion."

Models of quasars and their winds will have to be revised to account for these objects.

To help understand what revision is needed, the research team is observing these quasars further using Canadian and American access to the Gemini-North telescope in Hawaii.

More information: Paper: mnras.oxfordjournals.org/content/434/1/222.abstract

Survivor of stellar collision is new type of pulsating star

Artist's impression of the eclipsing, pulsating binary star J0247-25. 

Credit: Keele University

A team of astronomers from the UK, Germany and Spain have observed the remnant of a stellar collision and discovered that its brightness varies in a way not seen before on this rare type of star.

By analysing the patterns in these brightness variations, astronomers will learn what really happens when stars collide.

This discovery will be published in the 27 June 2013 issue of the journal Nature.

Stars like our Sun expand and cool to become red giant stars when the hydrogen that fuels the nuclear fusion in their cores starts to run out.

Many stars are born in binary systems so an expanding red giant star will sometimes collide with an orbiting companion star.

As much as 90% of the red giant star's mass can be stripped off in a stellar collision, but the details of this process are not well understood.

Only a few stars that have recently emerged from a stellar collision are known, so it has been difficult to study the connection between stellar collisions and the various exotic stellar systems they produce.

When an eclipsing binary system containing one such star turned up as a by-product of a search for extrasolar planets, Dr Pierre Maxted and his colleagues decided to use the high-speed camera ULTRACAM to study the eclipses of the star in detail.

These new high-speed brightness measurements show that the remnant of the stripped red giant is a new type of pulsating star.

Many stars, including our own Sun, vary in brightness because of pulsations caused by sound waves bouncing around inside the star.

For both the Sun and the new variable star, each pulsation cycle takes about 5 minutes. These pulsations can be used to study the properties of a star below its visible surface.

Computer models produced by the discovery team show that the sound waves probe all the way to the centre of the new pulsating star.

Further observations of this star are now planned to work out how long it will be before the star starts to cool and fade to produce a stellar corpse ("white dwarf'") of abnormally low mass.

Dr Pierre Maxted from Keele University, who led the study, said "We have been able to find out a lot about these stars, such as how much they weigh, because they are in a binary system. This will really help us to interpret the pulsation signal and so figure out how these stars survived the collision and what will become of them over the next few billion years."

New Type of Matter Found: 'Nuclear Pasta' in Neutron Stars

Artistic representation of a neutron star. The layer of "nuclear pasta" would be located in the innermost crust, near the core.

CREDIT: University of Alicante

A rare state of matter dubbed "nuclear pasta" appears to exist only inside ultra-dense objects called neutron stars, astronomers say.

There, the nuclei of atoms get crammed together so tightly that they arrange themselves in patterns akin to pasta shapes — some in flat sheets like lasagna and others in spirals like fusilli.

And these formations are likely responsible for limiting the maximum rotation speed of these stars, according to a new study.

"Such conditions are only reached in neutron stars, the most dense objects in the universe besides black holes," said astronomer José Pons of Alicante University in Spain.

This new phase of matter had been proposed by theorists years ago, but was never experimentally verified.

Now, Pons and his colleagues have used the spin rates of a class of neutron stars called pulsars to offer the first evidence that nuclear pasta exists.

Pulsars emit light in a pair of beams that shoot out like rays from a lighthouse. As the pulsars spin, the beams rotate in and out of view, making the stars appear to "pulse" on and off, and allowing astronomers to calculate how fast the stars are spinning.

Researchers have observed dozens of pulsars, but have never discovered one with a spin period longer than 12 seconds.

"In principle, that is not expected. You should see some with larger periods," Pons told reporters. A longer spin period would mean the star is spinning more slowly.

But the pasta matter could explain the absence of pulsars with longer spin periods. The researchers realized that if atomic nuclei inside the stars were reorganizing into pasta formations, this matter would increase the electric resistivity of the stars, making it harder for electrons to travel through the material.

This, in turn, would cause the stars' magnetic fields to dissipate much faster than expected. Normally, pulsars slow their spin down by radiating electromagnetic waves, which causes the stars to lose angular momentum.

But if the stars' magnetic fields are already limited, as would happen with pasta-matter, they cannot radiate electromagnetic waves as strongly, so they cannot spin down.

This keeps the pulsars stuck at a minimum spin speed, or a maximum spin period.

"Making this connection between the observational astronomical effect, which is the existence of this upper spin period limit, with the need for this layer in the inner crust, is what makes the connection between observations and theory," Pons said.

Neutron stars form when massive stars reach the end of their lives and run out of fuel for nuclear fusion. These aging stars explode in supernovas, their cores collapsing into small, dense objects.

The resulting masses are so dense, in fact, that normal atoms cannot exist anymore. Instead, protons and electrons essentially melt into each other, producing neutrons as well as lightweight particles called neutrinos.

The end result is a neutron star, whose mass is 90-percent neutrons.

In these stars' crusts, which have been found to be billions of times stronger than steel, normal atomic nuclei made of protons and neutrons can still exist, albeit densely squished, and this is where the new pasta formations appear.

In normal matter, the separation among nuclei is huge (relatively speaking), as positively charged atomic nuclei don't like to be near each other.

"But in neutron stars, matter is very packed and nuclei are so close to each other that they almost touch," Pons said."It's like a huge, gigantic nuclei, a huge continuum."

The research was published June 9 in the journal Nature Physics.