RSSArchive for August, 2011

‘The Dish’ finds a ‘diamond planet’

Artist's visualisation of the pulsar and its orbiting planet

An artist's visualisation of the pulsar and its orbiting planet, which astronomers think could be made partly of diamond or a diamond-like substance. The blue squiggly line represents the beams of radio waves emanating from the pulsar. The orange bubble represents the size of the Sun, showing that the the planet's orbit has about the same radius as the Sun (about 600,000 km), yet it whizzes around in just two hours!

  • Planet detected orbiting a pulsar 4,000 light-years away
  • It’s actually the remnant core of what was once a star
  • Probably made of compressed carbon—diamond!

ASTRONOMERS USING ‘THE DISH’—CSIRO’s radio telescope near Parkes, NSW—believe they’ve found a small planet made of diamond, orbiting an unusual star.

The discovery was made by an international research team, led by Professor Matthew Bailes of Swinburne University of Technology in Melbourne, Australia, and is reported today in the journal Science.

“Although bizarre, this planet is evidence that we’ve got the right understanding of how these binary systems evolve,” said Dr Michael Keith of CSIRO Astronomy and Space Science, one of the research team members.

Not fitting the pattern

The researchers, from Australia, Germany, Italy, the UK and the USA, first found an unusual star called a pulsar, now named PSR J1719-1438, using the 64-m Parkes radio telescope in eastern Australia.

Pulsars are small spinning stars about 20 km in diameter—the size of a small city—that emit a beam of radio waves. As the star spins and the radio beam sweeps repeatedly over Earth, radio telescopes detect a regular pattern of radio pulses.

The researchers followed up their discovery with the Lovell radio telescope in the UK and one of the Keck telescopes in Hawaii, and noticed that the arrival times of the pulsar’s pulses were systematically altered—in a way that must be caused by the gravitational pull of a small planet orbiting the pulsar.

The CSIRO's Parkes radio telescope

The CSIRO's Parkes radio telescope

Small, heavy and fast

The modulations of the radio pulses reveal several things about the planet.

First, it orbits the pulsar in just two hours and ten minutes, and the distance between the two objects is 600,000 km—a little less than the radius of our Sun.

Second, the companion must be small, less than 60,000 km (that’s about five times the Earth’s diameter). The planet is so close to the pulsar that, if it were any bigger, it would be ripped apart by the pulsar’s gravity.

But despite its small size, the planet has slightly more mass than Jupiter.

A stripped-down dwarf

“This high density of the planet provides a clue to its origin,” Professor Bailes said.

The team thinks that the ‘diamond planet’ is all that remains of a once-massive star, most of whose matter was siphoned off towards the pulsar.

But pulsar J1719-1438 and its companion are so close together that the companion can only be a very stripped-down ‘white dwarf’ star, one that has lost its outer layers and over 99.9 per cent of its original mass.

“This remnant is likely to be largely carbon and oxygen, because a star made of lighter elements like hydrogen and helium would be too big to fit the measured orbit,” said CSIRO’s Dr Keith.

The density means that this material is certain to be crystalline—that is, a large part of the star may be similar to a diamond.

The pulsar and its planet lie 4,000 light-years away in the constellation of Serpens (the Snake). The system is about an eighth of the way towards the Galactic Centre from the Earth.

Diamond planet Easy Q&A

What have they found?

  • They’ve spotted a system that comprises a weird kind of star, called a pulsar, and a medium-sized planet that is probably made of almost pure carbon…which is most likely in the form of diamond or a diamond-like substance.
  • The system is 4,000 light-years from Earth—that’s 40 thousand trillion kilometres away!
  • The pulsar emits radio waves in a regular pattern as it spins, like a lighthouse, which is what the CSIRO’s Parkes radio telescope picked up.
  • The planet itself cannot be seen as it is too small and too far away.

If they can’t see the planet, how do they know it’s really there?

  • Its presence is inferred by the distorting effect it has on the pulsar’s powerful radio emissions.
  • It whizzes around its star in just two hours (compared to one year for Earth around the Sun).
  • The data was analysed using an incredible supercomputer at Swinburne University in Melbourne.
  • The planet is about 5 times as wide as the Earth, but much, much heavier.

So why do they think it is made of diamond?

  • Now here’s the interesting bit, because the planet actually seems to be the dense, remnant core of a star, rather than a traditional planet.
  • Many stars, as they burn up their hydrogen fuel, end up having cores made of carbon.
  • The star changed into a planet, with only it’s core remaining.

How did it change from a star into a planet?

  • Because the pulsar has a huge gravitational pull and is a cosmic cannibal!
  • The pulsar and the other star would have been orbiting very close to each other.
  • The pulsar would have pulled all the outer gas layers off the other star—99.9 percent of its mass—eventually leaving it with just its carbon core.
  • If we could have seen it happening, it would have looked like a huge whirlpool of gas coming off the doomed star and spiralling onto the neighbouring pulsar.

What do astronomers hope to learn from these types of star systems?

  • For one thing, pulsars are the “end points”—the dying stages—in the lives of many kinds of big stars, so learning more about them tells us about the evolution and life cycle of those stars and the wider universe.
  • But pulsars also are important for understanding and testing laws of physics.
  • Astronomers can use them as “natural laboratories” for testing theories, such as Einstein’s theory of gravity.
  • That’s because you can only go so far testing some theories in the laboratory—to really put them to the test, you need to study massive objects travelling at high speed, and that’s what pulsar systems are.

Main text adapted from information issued by CSIRO. Q&A by Jonathan Nally, SpaceInfo.com.au Images courtesy Swinburne Astronomy Productions and David McClenaghan, CSIRO.

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Galaxy gazing with The Eyes

Galaxies NGC 4438 and NGC 4435

A peculiar pair of galaxies, NGC 4438 and NGC 4435, nicknamed The Eyes. The larger of the two, NGC 4438 (top) is thought to have once been a spiral galaxy that was strongly deformed by collisions with other galaxies in the relatively recent past. The two galaxies belong to the Virgo Cluster and are about 50 million light-years away.

  • The Eyes are two galaxies, NGC 4435 and 4438
  • Located 50 million light-years from Earth
  • Probably involved in a collision 100 million years ago

THIS BEAUTIFUL YET PECULIAR pair of galaxies is nicknamed ‘The Eyes’ and is about 50 million light-years from Earth, with the two galaxies some 100,000 light-years apart.

Their nickname comes from the apparent similarity between their cores—two white ovals that resemble a pair of eyes glowing in the dark when seen through a moderate-sized backyard telescope.

But although the centres of these two galaxies look similar, their outskirts could not be more different.

The galaxy in the lower right, known as NGC 4435, is compact and seems to be almost devoid of gas and dust.

In contrast, the large galaxy in the upper left (NGC 4438) has a lane of obscuring dust just below its core, young stars can be seen left of its centre, and gas extends at least up to the edges of the image.

The contents of NGC 4438 have been stripped out by a violent process—a collision with another galaxy that has distorted its spiral shape.

NGC 4435 could be the culprit. Some astronomers think that the damage caused to NGC 4438 resulted from an approach between the two galaxies to within about 16,000 light-years some 100 million years ago.

But while the larger galaxy was damaged, the smaller one was significantly more affected. Gravitational ‘tides’ from the clash are probably responsible for ripping away the contents of NGC 4438, and for removing most of NGC 4435’s gas and dust.

Another possibility is that the giant elliptical galaxy Messier 86, further away from The Eyes and not visible in this image, was responsible for the damage caused to NGC 4438. Recent observations have found filaments of ionised hydrogen gas connecting the two large galaxies, indicating that they may have collided in the past.

Messier 86 and The Eyes belong to the Virgo Cluster, a very rich grouping of galaxies. In such close quarters, galaxy collisions are fairly frequent.

Download wallpapers of The Eyes galaxies (NGC 4438 and NGC 4435):

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Adapted from information issued by ESO / Gems project.

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Moon mission soon to launch

NASA’S LUNAR-BOUND GRAIL twins are being prepared for launch at Cape Canaveral Air Force Station’s Launch Complex 17.

GRAIL-A and GRAIL-B will fly in tandem orbits around the Moon for several months to measure its gravity field in unprecedented detail. The mission will answer longstanding questions about the Moon, and provide scientists a better understanding of how Earth and other rocky planets in the Solar System formed.

GRAIL’s launch period opens September 8 and extends through to October 19. On each day, there are two separate instantaneous launch opportunities separated in time by approximately 39 minutes. On September 8, the first launch opportunity is at 10:37pm Sydney time (8:37am EDT). The second launch opportunity is 11:16pm (9:16am EDT).

Adapted from information issued by NASA/JPL-Caltech.

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Galaxies are running out of gas

A star-forming region

Compared to earlier cosmic epochs, galaxies these days are running of out of the gas raw material with which to make new stars. (Hubble Space Telescope image.)

THE UNIVERSE FORMS FEWER STARS than it used to, and a CSIRO study has now shown why—compared to the past, galaxies today have less gas from which to make stars.

Dr Robert Braun (CSIRO Astronomy and Space Science) and his colleagues used CSIRO’s Mopra radio telescope near Coonabarabran, NSW, to study far-off galaxies and compare them with nearby ones.

Light (and radio waves) from the distant galaxies takes time to travel to us, so we see the galaxies as they were between three and five billion years ago.

Galaxies at that stage of the Universe’s life appear to contain considerably more molecular hydrogen gas than comparable galaxies in today’s Universe, the research team found.

Stars form from clouds of molecular hydrogen. The less molecular hydrogen there is, the fewer stars will form.

The research team’s paper is in press in Monthly Notices of the Royal Astronomical Society.

Raw material for stars

Astronomers have known for at least 15 years that the rate of star formation peaked when the Universe was only a few billion years old and has declined steeply ever since.

“Our result helps us understand why the lights are going out,” Dr Braun said. “Star formation has used up most of the available molecular hydrogen gas.”

Mopra radio telescope

CSIRO's Mopra radio telescope near Coonabarabran in New South Wales.

After stars form, they shed gas during various stages of their lives, or in dramatic events such as explosions (supernovae). This returns some gas to space to contribute to further star formation.

“But most of the original gas—about 70%—remains locked up, having been turned into things such as white dwarfs, neutron stars and planets,” Dr Braun said.

“So the molecular gas is used up over time. We find that the decline in the molecular gas is similar to the pattern of decline in star formation, although during the time interval that we have studied, it is declining even more rapidly.”

Dark energy the demon

Ultimately, the real problem is the rate at which galaxies are “refuelled” from outside.

Gas falls into galaxies from the space between galaxies, the intergalactic medium. Two-thirds of the gas in the universe is still found in the intergalactic medium—the space between the galaxies—and only one third has already been consumed by previous star formation in galaxies, astronomers think.

“The drop-off in both gas availability and star formation seems to have started around the time that Dark Energy took control of the Universe,” Dr Braun said.

Up until that time, gravity dominated the Universe, so the gas was naturally pulled in to galaxies, but then the effect of Dark Energy took over and the Universe started expanding faster and faster.

This accelerating expansion has probably made it increasingly difficult for galaxies to capture the additional gas they need to fuel future generations of star formation, Dr Braun speculates.

Adapted from information issued by CSIRO; NASA, ESA, STScI/AURA.

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Shooting star, seen from above

ISS image of a meteor

The bright streak of a Perseid meteor as it flashes into Earth's upper atmosphere. The image was snapped by an astronaut aboard the International Space Station.

THIS ASTRONAUT PHOTOGRAPH, taken from the International Space Station (ISS) while over China (approximately 400 kilometres to the northwest of Beijing), provides the unusual perspective of looking down on a meteor as it passed through the atmosphere.

Many people have spent time outdoors under a dark sky, watching for “shooting stars” to streak across the firmament. In some cultures, this event is an occasion to make a wish; in others it is viewed as a herald of important events, such as the birth of a future ruler.

While not actual stars, “shooting stars” do come from outer space, in the form of meteoroids entering the Earth’s atmosphere.

Meteor or meteorite?

Meteoroids are small objects moving through the Solar System that are attracted to the Earth by its gravitational pull.

These small objects—typically fragments of asteroids or comets, though they can also originate from the Moon or Mars—begin to heat and burn up as they collide with air molecules in Earth’s atmosphere, creating a bright vapour trail or streak.

At this point, the object is known as a meteor. If any remnant of the object survives to impact the Earth’s surface, it becomes known as a meteorite.

While most meteorites are natural in origin, on occasion manmade space debris can re-enter the atmosphere and also become a meteor or even a meteorite!

Comes from a comet

The image was taken on August 13, 2011, during the Perseid Meteor Shower that occurs every August. The Perseid meteors are particles that originate from Comet Swift-Tuttle; the comet’s orbit is close enough for these particles to be swept up by the Earth’s gravitational field every year—leading to one of the most dependable meteor shower displays.

Green and yellow airglow appears in thin layers above the limb of the Earth, extending from image left to the upper right. Atoms and molecules above 50 kilometres in the atmosphere are excited by sunlight during the day, and then release this energy at night, producing primarily green light that is observable from orbit.

Part of a ISS solar panel is visible at upper right; behind the panel.

Astronaut photograph provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre. Text adapted from information issued by William L. Stefanov, Jacobs/ESCG at NASA-JSC.

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High and dry – Astronomy in the Atacama

IN THE PURSUIT OF PRISTINE SKIES, ESO—the European Southern Observatory organisation—operates its telescopes far beyond Europe, in the remote and arid landscape of the Atacama Desert in Chile. This ESOcast episode explains why astronomers like to get high and dry.

Adapted from information issued by ESO. Still image courtesy G. Hüdepohl (atacamaphoto.com) / ESO.

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Alien world is blacker than coal

Artist's conception of exoplanet TrES-2b

Exoplanet TrES-2b (artist's conception) is darker than the blackest coal. This Jupiter-sized world reflects less than 1% of the light that falls on it, making it blacker than any planet or moon in our Solar System.

  • Exoplanet TrES-2b orbits a star 750 light-years from Earth
  • Reflects less than one percent of the starlight falling on it
  • The Jupiter-sized world puts out only a faint red glow

ASTRONOMERS HAVE DISCOVERED the darkest known exoplanet—a distant, Jupiter-sized gas giant known as TrES-2b. Their measurements show that TrES-2b reflects less than one percent of the starlight falling on it, making it blacker than coal or any planet or moon in our Solar System.

“TrES-2b is considerably less reflective than black acrylic paint, so it’s truly an alien world,” said astronomer David Kipping of the Harvard-Smithsonian Centre for Astrophysics (CfA), lead author on the paper reporting the research.

In our Solar System, Jupiter is swathed in bright clouds of ammonia that reflect more than a third of the sunlight reaching it. In contrast, TrES-2b (which was discovered in 2006 by the Trans-Atlantic Exoplanet Survey, or TrES) lacks reflective clouds due to its high temperature.

Pitch black planet … almost

TrES-2b orbits its star at a distance of only 4.8 million kilometres. The star’s intense light heats TrES-2b to a temperature of more than 1,000° Celsius—much too hot for ammonia clouds.

Instead, its exotic atmosphere contains light-absorbing chemicals like vaporised sodium and potassium, or gaseous titanium oxide. Yet none of these chemicals fully explain the extreme blackness of TrES-2b.

“It’s not clear what is responsible for making this planet so extraordinarily dark,” stated co-author David Spiegel of Princeton University. “However, it’s not completely pitch black. It’s so hot that it emits a faint red glow, much like a burning ember or the coils on an electric stove.”

Artist's impression of the Kepler spacecraft

Artist's impression of the Kepler spacecraft

One-sided world

Kipping and Spiegel determined the reflectivity of TrES-2b using data from NASA’s Kepler spacecraft. Kepler is designed to measure the brightnesses of distant stars with extreme precision.

The team monitored the brightness of the TrES-2 system as the planet orbited its star. They detected a subtle dimming and brightening due to the planet’s changing phase.

TrES-2b is believed to be tidally locked like our moon, so one side of the planet always faces the star. And like our moon, the planet shows changing phases as it orbits its star. This causes the total brightness of the star plus planet to vary slightly.

“By combining the impressive precision from Kepler with observations of over 50 orbits, we detected the smallest-ever change in brightness from an exoplanet—just 6 parts per million,” said Kipping. “In other words, Kepler was able to directly detect visible light coming from the planet itself.”

More where this one came from?

The extremely small fluctuations proved that TrES-2b is incredibly dark. A more reflective world would have shown larger brightness variations as its phase changed.

Kepler has located more than 1,200 planetary candidates in its field of view. Additional analysis will reveal whether any other unusually dark planets lurk in that data.

TrES-2b orbits the star GSC 03549-02811, which is located about 750 light-years from Earth. (One light-year is about 10 trillion kilometres.)

Adapted from information issued by CfA. Images courtesy David A. Aguilar (CfA) / NASA.

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10 things to know about Juno

HAVING BEGUN ITS FIVE-YEAR JOURNEY to Jupiter, NASA’s Juno spacecraft has a long road ahead of it before it can get to work studying the largest planet in the Solar System. The demanding mission will involve a long cruise phase, a hazardous operation phase, and a kamikaze ending.

Here are 10 interesting and fascinating facts about the Juno spacecraft and its target planet.

  • Total flight distance to Jupiter is 2,800 million kilometres. If you could hop in your car and drive non-stop at 100 kilometres per hour, it would take you 3,196 years to cover that distance. Juno will do it in just 5 years!
  • One it reaches Jupiter, the spacecraft will spend 12 months completing 33 huge orbits around the planet.
  • The orbits will go north-south over Jupiter’s poles. This sort of orbit is used when mission planners want to cover every square metre of a planet—as Juno circles, the planet rotates underneath and the spacecraft can ‘map’ the whole globe, strip by strip.
  • The orbit will bring Juno to within 5,000 kilometres of the planet’s cloud tops every 11 days. This will be the closest a spacecraft has ever come to Jupiter, apart from the entry probe released by the Galileo spacecraft. (That probe plunged into Jupiter’s atmosphere on December 7, 1995, sending back data for about 57 minutes before being destroyed by the incredible temperatures and pressures.)
  • Jupiter is surrounded by an enormous and intense radiation field. Mission planners intend to keep Juno out of the worst of it—yet still, over the course of its 12 months investigating the giant planet, the spacecraft will receive a total radiation dose equivalent to 100 million dental X-rays. Ouch!

    A Juno solar panel

    Juno carries three 9m-long solar power panels.

  • Because of that, the spacecraft’s vital innards are protected inside a titanium box, known as ‘the vault’.
  • This is the first mission to go so far from the Sun without a plutonium power source. Instead, Juno has three huge, 9-metre-long high-efficiency solar power panels.
  • Juno is named after the Roman goddess and wife of the mythological figure, Jupiter. Juno was supposed to have the ability to see through clouds, so it is fitting that her name is given to a mission that will see below Jupiter’s thick cloud layers.
  • After 12 months orbiting Jupiter, Juno will be deliberately de-orbited and perform a fiery death plunge into the planet’s atmosphere. This will be done to eliminate the possibility of the spacecraft eventually crashing into one of Jupiter’s moons, potentially contaminating it with any microbes that might have been brought all the way from Earth.
  • Total cost of the mission is about US$1.1 billion, which includes all the development, construction, launch, cruise and operation costs through to the end of the mission on October 16, 2017.

Story by Jonathan Nally, SpaceInfo.com.au. Images courtesy NASA / JPL-Caltech / KSC.

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Take a tour of the Crab Nebula

THE CRAB NEBULA IS ONE OF THE BRIGHTEST sources of high-energy radiation in the sky. Little wonder—it’s the expanding remains of an exploded star, a supernova seen in 1054.

Scientists have used virtually every telescope at their disposal, including NASA’s Chandra X-ray Observatory, to study the Crab.

The supernova left behind a magnetised neutron star—a pulsar. It’s about the size of Washington DC, but it spins 30 times per second. Each rotation sweeps a lighthouse-like beam past us, creating a pulse of electromagnetic energy detectable across the spectrum.

The pulsar in the Crab Nebula is among the brightest sources of high-energy gamma rays. Recently, NASA’s Fermi Gamma Ray Observatory and Italy’s AGILE Satellite detected strong gamma-ray flares from the Crab, including a series of “superflares” in April 2011.

To help pinpoint the location of these flares, astronomers enlisted Chandra space telescope.

With its keen X-ray eyes, Chandra saw lots of activity, but none of it seems correlated with the superflare. This hints that whatever is causing the flares is happening with about a third of a light-year from the pulsar. And rapid changes in the rise and fall of gamma rays imply that the emission region is very small, comparable in size to our Solar System.

The Chandra observations will likely help scientists to home in on an explanation of the gamma-ray flares one day.

Even after a thousand years, the heart of this shattered star still offers scientists glimpses of staggering energies and cutting edge science.

Adapted from information issued by Harvard-Smithsonian Centre for Astrophysics. Still image courtesy (X-ray) NASA / CXC / SAO / F.Seward, (optical) NASA / ESA / ASU / J.Hester & A.Loll, (infrared) NASA / JPL-Caltech / Univ. Minn. / R.Gehrz.

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Made in Space – DNA building blocks

NASA-FUNDED RESEARCHERS HAVE UNCOVERED EVIDENCE that some building blocks of DNA—the molecule that carries the genetic instructions for life—found in meteorites, were likely formed in space.

The research gives support to the idea that a ‘kit’ of ready-made parts formed in space and delivered to Earth by meteorite and comet impacts, assisted the development of life.

Adapted from information issued by NASA / GSFC.

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