Scientific Research on ISS (International Space Station)

A comparison between fire on Earth (left) and fire in a microgravity environment (right), such as that found on the ISS.

One of the main goals of the ISS is to provide a place to conduct experiments that require one or more of the unusual conditions present on the station. The primary fields of research include biology, physics, astronomy, and meteorology.The 2005 NASA Authorization Act designated the US segment of the International Space Station as a national laboratory with a goal to increase the use of the ISS by other Federal entities and the private sector.

One research goal is to improve the understanding of long-term space exposure on the human body. Subjects currently under study include muscle atrophy, bone loss, and fluid shift. The data will be used to determine whether space colonisation and lengthy human spaceflight are feasible. As of 2006, data on bone loss and muscular atrophy suggest that there would be a significant risk of fractures and movement problems if astronauts landed on a planet following a lengthy space cruise.

Researchers are investigating the relation of the near-weightless environment on the ISS to the evolution, development and growth, and the internal processes of plants and animals. In response to some of this data, NASA wants to investigate microgravity's effects on the growth of three-dimensional, human-like tissues, and the unusual protein crystals that can be formed in space.

The physics of fluids in microgravity is being investigated, enabling researchers to better model the behaviour of fluids in the future. Because of the ability to almost completely combine fluids in microgravity, physicists are interested in investigating the combinations of fluids that will not normally mix well on Earth. In addition, by examining reactions that are slowed down by low gravity and temperatures, scientists hope to gain new insight regarding superconductivity.

Materials science is an important part of the research activity aboard the station, with the goal of reaping economic benefits by improving techniques used on the ground. Experiments are intended to provide a better understanding of the relationship between processing, structure, and properties so the conditions required on Earth to achieve desired materials properties can be reliably predicted.

Other areas of interest include the effect of the low gravity environment on combustion, studying the efficiency of burning and control of emissions and pollutants. These findings may improve our understanding of energy production, and in turn have an economic and environmental impact. There are also plans to use the ISS to examine aerosols, ozone, water vapour, and oxides in Earth's atmosphere, as well as cosmic rays, cosmic dust, antimatter, and dark matter in the universe.

One component assisting in these various studies is the ExPRESS Logistics Carrier (ELC). Developed by NASA, four of these units are set to be launched to the ISS. As currently envisioned, the ELCs will be delivered on three separate Space Shuttle missions. They will allow experiments to be deployed and conducted in the vacuum of space, and will provide the necessary electricity and computing to process experimental data locally. Delivery is currently scheduled for STS-129 in November 2009, STS-133 in May 2010 and STS-134 in September 2010.

The Alpha Magnetic Spectrometer (AMS), a particle physics experiment, is scheduled to be added to the station. This device will be launched on STS-134 in 2010, and will be mounted externally on the Integrated Truss Structure. The AMS will search for various types of unusual matter by measuring cosmic rays. The experiments conducted will help researchers study the formation of the universe, and search for evidence of dark matter and antimatter.

Keck Interferometer Nuller Spots Double Dust Cloud

Credit: NASA/GSFC/Marc Kuchner and Francis Reddy
This graphic compares the inner and outer disk of the 51 Oph system to the location of the planets and asteroid belt of the Solar System.


KAMUELA, Hawaii (Sept. 24, 2009) — Linking the twin, 10-meter telescopes in Hawaii, astronomers at the W. M. Keck Observatory discovered an extended, double-layered dust disk orbiting 51 Ophiuchi, a star that is 410 light-years from Earth. It is the first time the Keck Interferometer Nuller instrument has identified such a compact cloud around a star so far away.

The new data suggest that 51 Ophiuchi is a protoplanetary system with a dust cloud that orbits extremely close to its parent star, said University of Maryland astronomer Christopher Stark, who led the research team.

Keck Observatory operates one of the largest optical interferometers in the United States. The interferometer provides high precision resolution measurements equal to a telescope as large as the distance that separates the telescope’s primary mirrors—85 meters in the case of the Keck twins. In April 2007, the team simultaneously pointed both Keck telescopes at the star 51 Ophiuchi, or 51 Oph, and used the Interferometer’s Nuller, a technique to combine the incoming light in a particular way, to block the unwanted starlight of 51 Oph and measure faint adjacent signals from the dust cloud surrounding the star.

According to the observations, excess material orbited 51 Oph. Stark and his collaborators repeated the nulling measurements at several different wavelengths of light and combined this data with information from other telescopes to determine the shape and orientation of the material as well as the sizes of the dust grains.

The data suggest that two debris disks orbit 51 Oph. The inner disk has larger grains, roughly 10 micrometers or larger in diameter, and extends out to four astronomical units, or AUs, beyond the star. The second disk comprised of mainly 0.1 micrometer grains extends from roughly seven AU to 1200 AU. One AU is the distance between Earth and the Sun or roughly 93 million miles. The new results appear in the Oct. 1 Astrophysical Journal.

If these debris disks orbited the Sun, the inner cloud of larger grains would extend roughly from the position of Mercury’s orbit to just past the edge of the asteroid belt. The outer disk of smaller grains would originate just before Saturn’s orbit and extend to a distance ten times farther than the edge of the Kuiper belt.

51 Oph’s inner, compact dust disk is one of the most compact dust clouds ever detected, and the new Keck Interferometer Nuller observations demonstrate the instrument’s ability to detect dust clouds a hundred times smaller than a conventional telescope can observe, Stark said.

The instrument was also essential to solving the mystery of what made 51 Oph’s dust disk appear so compact while its spectra, or chemical fingerprints, suggested that the dust orbited at much larger distances, added Marc Kuchner, an astronomer at NASA’s Goddard Space Flight Center in Greenbelt, Md. who was part of the research team. The answer was simply that the star had two debris disks.

Because of the power of the Keck Nuller, Stark and his team were able to resolve inner and outer dust disks, which together form 51 Oph’s exozodiacal cloud. In similar star systems, the outer cloud of dust seems to be a distinct outer belt, probably analogous to the Kuiper belt or a second system of asteroids. But 51 Oph appears to be different, Kuchner said. The observations suggest that the star’s outer cloud is comprised of smaller grains and is connected to the inner cloud so that the system has only one underlying belt of asteroids.

This system most likely represents a rare, nearby example of a young planetary system just entering the late stages of planet formation. Terrestrial planets may be forming, although none have been detected within the system yet, Stark said.

His team’s data also indicates that the cloud around 51 Oph is 100,000 times more dense than the dust cloud circling the Solar System. In most planet-forming systems, as asteroid and comet collisions produce dust, the larger grains spiral toward the star while its outward pressure pushes smaller particles to the edge or even out of the system. 51 Ophiuchi, a star 260 times more luminous than the Sun, likely pushes the smaller dust grains from the inner disk to the outer disk, Kuchner explained.

Keck’s Nuller, which was funded by NASA and built by the Jet Propulsion Laboratory in Pasadena, Calif., will be used to help astronomers further understand how and when these asteroid belts form and how dust from the star’s debris disk might interfere with direct imaging of planets orbiting another star, he said.

Radical New Theory: Black Holes Attack and Devour Stars from the Inside

As if they weren't considered beastly enough, black holes can dive into nearby stars and devour them from the inside out, scientists now suggest. Such invasions by such black holes could help explain the most powerful explosions in the universe, gamma-ray bursts, whose origins remain elusive.

The idea needs support from further theoretical work, and observations would help, too. Meanwhile, here's what spawned the notion:

Gamma-ray bursts are narrow beams of intense radiation that can unleash as much energy as our sun will during its entire 10-billion-year lifetime — all in anywhere from milliseconds to a minute or more. The processes that can generate that much energy in that short a time are among the biggest mysteries in astronomy today.

The majority of gamma-ray bursts last two seconds or more. These cosmic flashes, dubbed long gamma-ray bursts, are linked to jets of plasma from massive dying stars. Scientists currently suggest this plasma is heated up by the energy released from neutrinos as they meet and annihilate their antimatter counterparts. Both kinds of particles are emitted by the dense, hot disk of matter that accretes or builds up around a black hole as it rips apart a dying star.

Now researchers have come up with a different, radical explanation — the plasma jets come directly from black holes when they invade stars.

Powerful forces

Their concept is based on recent observations by the Swift satellite that indicates the central engine driving these plasma jets can operate for up to 10,000 seconds, much longer than the neutrino model can explain.

Scientists at the University of Leeds in England instead suggest the matter that falls into black holes can generate extremely powerful magnetic forces that focus and drive the plasma jets linked with long gamma-ray bursts. The matter has to whirl very rapidly, with the centrifugal forces caused by this spin opposing the powerful gravitational pull of the black hole, for the prolonged blast seen in long gamma-ray bursts.

The researchers found one way such whirling matter could result is if a black hole plunged into a star and began eating it from the inside. As the black hole ripped the star apart, its remains could twirl apart in precisely the right way needed for a long gamma-ray burst.

"This 'invader variant' provides a natural explanation of the very fast rotation," researcher Serguei Komissarov, a mathematician and astrophysicist at the University of Leeds in England, told.

Other ideas

Another way such rapid spinning might have occurred is if the dying star was initially born rotating very quickly and retained this rate of spin during its entire life. Also, the dying star in question might have orbited very close to another star, and the resulting tidal forces — the tug of one object that distorts the shape of another, just as the sun and moon cause tides in Earth's ocean and even in its rocky crust — could have spun it up, Komissarov explained.

"The magnetic model has been proposed by other scientists, say 10 years ago or so, but was never popular," Komissarov said. "During the last few years we have been studying the true potential of this model and now we argue that some observational data, including the latest data from Swift, speak in favor of it."

Komissarov did caution that no direct observations linked with long gamma-ray bursts have revealed the extremely strong magnetic fields required by their model so far.

"Further research, both theoretical and observational, is needed to clarify this issue," he said.

Komissarov and his colleague Maxim Barkov detailed their findings in the Monthly Notices of the Royal Astronomical Society.

The Planet that will die soon

Picture: The camera which has found Planet WASP-18b

WASP-18b is an extrasolar planet that is notable for having an orbital period of less than one day. It has a mass equal to 10 Jupiter masses,just below the boundary line between planets and brown dwarfs, about 13 Jupiter masses. Due to tidal deceleration, it is expected to spiral towards and eventually merge with its host star, WASP-18, in less than a million years.The planet is approximately 1.9 million miles from its star, which is about 325 light years from Earth. It was discovered by Coel Hellier, a professor of astrophysics at Keele University in England.

Scientists at Keele and at the University of Maryland are working to understand whether the discovery of this planet so shortly before its expected demise (with less than 0.1% of its lifetime remaining) was fortuitous, or whether tidal dissipation by WASP-18 is actually much less efficient than astrophysicists typically assume.Observations made over the next decade should yield a measurement of the rate at which WASP-18b's orbit is decaying.

The closest example of a similar situation in our own solar system is Mars' moon, Phobos. Phobos orbits Mars at a distance of only about 5,600 miles, 40 times closer than our moon is to the Earth,and is expected to be destroyed in about eleven million years.