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Resources and web links

HELLO FOLKS. My apologies for the lack of updates on SpaceInfo.com.au in recent weeks, but your editor has been away conducting astronomy lectures aboard a cruise ship (the wonderful m/s Oosterdam, of the Holland America Line) on a journey to various tropical paradises scattered throughout the Pacific Ocean. Having now reluctantly returned to reality, it’ll be back to normal with SpaceInfo.

Lots of people aboard the Oosterdam asked me where I got all the incredible images of space that I showed during my lectures, and I promised to post some links. So here we go.

NASA has plenty of great web sites, for adults and children, including these favourites of mine:

NASA home page

NASA Planetary Photojournal

NASA Human Space Flight Gallery

NASA Quest

NASA Kids’ Club

There are lots of amazing images from the Hubble Space Telescope at these sites:

Hubble Space Telescope

European Space Agency Hubble site

There are other telescopes up in space too – here are a few:

Spitzer Space Telescope

Kepler Observatory

Herschel Space Telescope

And then there are all the wonderful ground-based observatories — here’s a small selection:

Australian Astronomical Observatory

Australia Telescope

Square Kilometre Array

Keck Observatory

Gemini Observatory

For keeping an eye on the Sun and solar activity, try these sites:

SOHO spacecraft

Solar Dynamics Observatory spacecraft

Here are links to some of the spacecraft missions that are exploring the planets of our Solar System:

MESSENGER (Mercury)

LRO (the Moon)

Cassini (Saturn)

Juno (Jupiter)

New Horizons (Pluto)

Curiosity rover (Mars)

Mars Express (Mars)

Mars Odyssey (Mars)

Mars Reconnaissance Orbiter (Mars)

Opportunity rover (Mars)

My thanks to everyone aboard the m/s Oosterdam, both crew and passengers, for making the journey so enjoyable and fulfilling.

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‘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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Happy birthday Neptune!

Neptune

Neptune, the eighth planet from the Sun, has now completed one 165-Earth-year-long orbit of the Sun since it's discovery in 1846.

THE EIGHTH PLANET is celebrating today, having completed one orbit around the Sun since its discovery in 1846. Neptune’s year is 164.8 Earth years long, so it has taken until now for it to make one full circle of the Solar System.

Neptune was the first planet to be found via a mathematical prediction. Astronomers had noted that Uranus—the next planet inwards to the Sun—was not following its predicted path, and the gravitational pull of an as-yet-undiscovered planet was thought to the culprit.

Predictions were made for where in the sky this mystery planet might be found, and sure enough, there it was—Neptune.

The story of the prediction and discovery has lots of twists and turns—read more about it here.

And the story of how the planet then got its name is equally complex—and you can read more about that here.

Neptune orbits the Sun at an average distance of 30.1 AU (one AU being the distance between Earth and Sun), or about 4.5 billion kilometres.

The following video (courtesy NASA, ESA, G. Bacon, and Z. Levay (STScI)) shows a speeded up view of Neptune rotating, using images taken every four hours by the Hubble Space Telescope:

Neptune is the fourth-largest planet, with a radius at the equator of 24,764 kilometres—about four times wider than Earth.

The giant blue world is the most distant Solar System body visited by a spacecraft. NASA’s Voyager 2 probe flew past Neptune in 1989.

Here’s a fascinating video (courtesy NASA, ESA, and G. Bacon and M. Estacion (STScI)) which puts that one Neptunian orbit into an Earth timeline perspective:

Story by Jonathan Nally. Images courtesy NASA.

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Confirmed: first image of distant planet

Star 1RXS J160929.1-210524 and its planet

This image, first released in September of 2008, shows the star 1RXS J160929.1-210524 and its ~8 Jupiter-mass companion (within red circle), which has now been confirmed as a planet.

  • Planet first spotted in 2008; needed confirmation
  • Now known to orbit a star 500 light-years from Earth
  • A scorching 1,500ºC; still cooling down

A planet only about 8 times the mass of Jupiter has been confirmed orbiting a Sun-like star at over 300 times farther from the star than the Earth is from our Sun.

It is the least-massive planet known to orbit at such a great distance from a star.

The discovery utilised high-resolution adaptive optics technology at the Gemini Observatory to take direct images and light spectra of the planet.

First reported in September 2008 by a team led by David Lafrenière (then at the University of Toronto, now at the University of Montreal and Centre for Research in Astrophysics of Quebec), the suspected planetary system required further observations over time to confirm that the planet and star were indeed moving together through space.

Back in 2008, all astronomers knew for sure was that the young, planetary mass object appeared to be sitting right next to the young Sun-like star.

The closeness of the two objects strongly suggested that they were linked, but it was still possible (though unlikely) that they were unrelated and only aligned by chance.

According to Lafrenière, “Our new observations rule out this chance alignment possibility, and thus confirms that the planet and the star are related to each other.”

With this confirmation the system, known as 1RXS J160929.1-210524 (or 1RXS 1609 for short), provides scientists with a unique specimen that challenges planetary formation theories because of its extreme distance from the star.

“The unlikely locale of this alien world could be telling us that nature has more than one way of making planets,” says co-author Ray Jayawardhana of the University of Toronto.

An infrared image of the 1RXS 1609 system

An infrared (heat) image of the system, revealing the planet to be a scorching 1,500 degrees Celsius.

“Or, it could be hinting at a violent youth when close encounters between newborn planets hurl some siblings out to the hinterlands,” he adds.

First to be directly imaged

With its initial detection by the team using the Gemini Observatory in April of 2008, the object became the first likely planet known to orbit a Sun-like star to be revealed by direct imaging (rather than the indirect through which most such planets have been found).

At the time of its discovery the team also obtained a spectrum of the light from the planet and was able to determine many of its characteristics, which are confirmed in this new work.

Since the initial observations several other worlds have been discovered using direct imaging, including a system of three planets around the star HR 8799 also discovered with Gemini. However, the planets around HR 8799 orbit much closer to their host star.

The team’s recent work on 1RXS 1609 also verified that no additional large planets (between 1-8 Jupiter masses) are present in the system closer to the star.

Future observations should make it possible to measure a very precise velocity of the planet relative to its host star. This will show whether the planet is on a roughly circular orbit, as would be expected if it really formed far from its host star; or whether it is in a very non-circular or even “open” orbit, as could be the case if it formed closer to its star, but was gravitationally “kicked out” following a close encounter with another planet.

Scorching hot planet

The host star is located about 500 light-years away in a group of young stars called the Upper Scorpius association that formed about five million years ago. The original survey studied more than 85 stars in this association.

The planet has an estimated temperature of about 1,500 degrees Celsius and is much hotter than Jupiter, which has a atmospheric cloud-top temperature of about 160 Kelvin (-110 degrees Celsius). The host star has an estimated mass of about 85% that of our Sun.

The Gemini North observatory in Hawai'i

The Gemini North observatory in Hawai'i

The young age of the system explains the high temperature of the planet. The contraction of the planet under its own gravity during its formation quickly raised its temperature to thousands of degrees. With this contraction phase over, the planet is slowly cooling down by radiating infrared light (heat). In billions of years, the planet will eventually reach a temperature similar to that of Jupiter.

High-tech telescope

The observations used the Near-Infrared Imager (NIRI) and the Altair adaptive optics system on the Gemini North telescope. Adaptive optics allows scientists to remove much of the distortions caused by our atmosphere and dramatically sharpen views of space.

“Without adaptive optics, we would simply have been unable to see this planet,” says Lafrenière. “The atmosphere blurs the image of a star so much that it extends over and is much brighter than the image of a faint planet around it, rendering the planet undetectable.”

“Adaptive optics removes this blurring and provides a better view of faint objects very close to stars.”

The Gemini Observatory is an international collaboration with two identical 8-metre telescopes. The Frederick C. Gillett Gemini Telescope is located at Mauna Kea, Hawai’i (Gemini North) and the other telescope at Cerro Pachón in northern Chile (Gemini South).

Together, they provide full coverage of both hemispheres of the sky. Both telescopes incorporate new technologies that allow large, relatively thin mirrors under active control to collect and focus both optical and infrared radiation from space.

Countries in the Gemini partnership are the USA, UK, Canada, Chile, Argentina, Australia and Brazil.

Adapted from information issued by Gemini Observatory / AURA / David Lafrenière (University of Montreal) / Ray Jayawardhana (University of Toronto) / Marten van Kerkwijk (University of Toronto).