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What’s up? The night sky for December 2011

Telescope dome at night

Stargazing is great fun, now that the warmer summer weather is here.

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere.

December 2

It is First Quarter Moon today at 8:52pm Australian Eastern Daylight Time (AEDT). First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains  throw nice shadows, making it easier to get that 3D effect.

December 6

Today the Moon will reach the farthest point in its orbit, apogee, at a distance from Earth of 405,412 kilometres. And if you take a look at the Moon this evening, you’ll see a bright ‘star’ above and to its right. That’s not a star—it’s actually the planet Jupiter!

December 9

Take a look at the Moon in this evening’s sky, and you’ll see a brightish star a little way out to its right. And yes, this one really is a star. It’s called Aldebaran, and it’s the brightest star in the constellation Taurus. Aldebaran is a red giant star roughly 44 times as big as the Sun, and is about 65 light-years from Earth.

December 10

Full Moon occurs today at 1:36am AEDT, and tonight everyone in Australia and New Zealand will experience a total lunar eclipse. See our separate lunar eclipse story for full details on how, when and where to see it.

Eclipses aside…although it looks very pretty high up there in the sky, astronomers, both amateur and professional, generally hate the full Moon. This is because its light tends to drown out many of the fainter objects they’re interested in seeing. (It does this by actually making the sky glow.) It’s also not a good time to look at the Moon itself through a telescope, as the overhead sunlight (as seen from the perspective of the Moon) doesn’t throw any shadows across the lunar surface—and shadows are what give the craters and mountains their 3D look.

Man looking through a telescope

The Moon looks great through a telescope, but you won't need one to see the total lunar eclipse on December 10, 2011.

December 17

If you’re up early today, look for the Moon and you’ll see that it seems to have two companions. A little way below and to its left is the star Regulus, and below and to its right is the planet Mars. Regulus is actually a quadruple star system, comprised of four stars in two groups of two, gravitationally bound to one another. But the main star is a young, blue star a little over three times the mass of the Sun, and about three to four times as big as the Sun too.

December 18

It is Last Quarter Moon today at 11:48am AEDT. The Moon is still near Mars in the sky, being above and to the right of the planet in the hours before dawn.

December 21

The Moon, a star and a planet make a nice triangle in this morning’s sky. The star is Spica, the brightest star in the constellation Virgo, and the planet is Saturn. Saturn will be to the left of the Moon, and Spica will be above Saturn. Spica, a blue giant star, is the 15th brightest star in the night sky and is about 260 light-years from Earth.

December 22

There are two items of note for today. First, the Moon will be at the closest point in its orbit, called perigee, which is the opposite of apogee. The distance between the two bodies today will be 364,800 kilometres. And secondly, today marks the summer solstice in the Southern Hemisphere. This is the day of the year when the Sun is highest in the sky.

December 25

New Moon occurs today at 5:06am AEDT.

December 27-28

The Moon is back in the western evening sky. Over these two nights, it’ll be paired up with the planet Venus—the duo will make a very attractive sight in the evening dusk.

There’s more great night sky viewing information at Melbourne Planetarium’s Skynotes site.

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Story by Jonathan Nally. Images courtesy IAU.

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ET’s nightlife could be a giveaway

Artist's impression of an alien planet showing city lights

If an alien civilisation builds brightly-lit cities, like those shown in this artist's conception, future generations of telescopes might allow us to detect them. This would offer a new method of searching for extraterrestrial intelligence elsewhere in our Galaxy.

IN THE SEARCH FOR EXTRATERRESTRIAL INTELLIGENCE, astronomers have hunted for radio signals and ultra-short laser pulses. But in a new proposal, Avi Loeb (Harvard-Smithsonian Centre for Astrophysics) and Edwin Turner (Princeton University) suggest a new technique for finding aliens—look for their city lights.

“Looking for alien cities would be a long shot, but wouldn’t require extra resources. And if we succeed, it would change our perception of our place in the universe,” said Loeb.

As with other SETI methods, they rely on the assumption that aliens would use Earth-like technologies. This is reasonable because any intelligent life that evolved in the light from its nearest star is likely to have artificial illumination that switches on during the hours of darkness.

Telling night from day

How easy would it be to spot a city on a distant planet? Clearly, this light will have to be distinguished from the glare from the parent star. Loeb and Turner suggest looking at the change in light from an exoplanet as it moves around its star.

As the planet orbits, it goes through phases similar to those of the Moon. When it’s in a dark phase, more artificial light from the night side would be visible from Earth than reflected light from the dayside. So the total flux from a planet with city lightingwill vary in a way that is measurably different from a planet that has no artificial lights.

Artist's impression of Pluto

Current technology could spot city lights on Pluto (artist's impression).

Spotting this tiny signal would require future generations of telescopes. However, the technique could be tested closer to home, using bodies at the edge of our Solar System.

Closer to home?

Loeb and Turner calculate that today’s best telescopes ought to be able to see the light generated by a Tokyo-sized metropolis at the distance of the Kuiper Belt—the region occupied by Pluto, Eris, and thousands of smaller icy bodies. So if there are any cities out there, we ought to be able to see them now.

By looking, astronomers can hone the technique and be ready to apply it when the first Earth-sized worlds are found around distant stars in our galaxy.

“It’s very unlikely that there are alien cities on the edge of our Solar System, but the principle of science is to find a method to check,” Turner said. “Before Galileo, it was conventional wisdom that heavier objects fall faster than light objects, but he tested the belief and found they actually fall at the same rate.”

As our technology has moved from radio and TV broadcasts to cable and fibre optics, we have become less detectable to aliens. If the same is true of extraterrestrial civilisations, then artificial lights might be the best way to spot them from afar.

Adapted from information issued by Harvard-Smithsonian Centre for Astrophysics. Images by David A. Aguilar (CfA) and ESO.

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What’s up? Night sky for November 2011

People looking at the evening sky

Late spring nights and mornings are ideal for stargazing, and there are some interesting things to see this month.

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere.

November 3

It is First Quarter Moon today at 3:38am Australian Eastern Daylight Time. First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains are throwing nice shadows, making it easier to get that 3D effect.

November 9

Take a look in the evening sky and you’ll see the Moon with what looks like a bright star above and to its right. Well, that’s not a star, it’s the planet Jupiter. Also today, the Moon will reach the farthest point from Earth in its orbit, apogee, at a distance from Earth of 406,176 kilometres.

November 10

Take a look at the western horizon after sunset and you’ll see a pretty group comprising Venus, Mercury and the star Antares.

Looking at the Moon with a telescope

The Moon teams up with several planets during November

November 11

Full Moon occurs today at 7:16am Australian Eastern Daylight Time.

November 11-12

Out to the east in the early morning sky (pre-dawn) you’ll find a pair of celestial orbs that contrast each other nicely in colour. Ruddy coloured Mars will appear very close to Regulus, a blue giant star that is the brightest star in the constellation Leo.

November 19

It is Last Quarter Moon today at 2:09am Australian Eastern Daylight Time. If you’re up before dawn, take a look out to the eastern sky and you’ll see the Moon with the star Regulus close by, and the planet Mars about 4 degrees away as well.

November 23

Another attractive grouping, but quite low in the eastern sky before dawn (so you’ll need a clear horizon). There’ll be the Moon, plus the star Spica (the brightest star in the constellation Virgo) and the planet Saturn as well.

November 24

Today the Moon will be at the closest point to Earth in its orbit, called perigee, which is the opposite of apogee. The distance between the two bodies today will be 359,691 kilometres.

November 25

New Moon occurs today at 5:10pm Australian Eastern Daylight Time.

November 27

Take a look out to the west just after sunset, and you might see the very thin crescent Moon below and to the right of the planet Venus.

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Images courtesy IAU / TWAN / Babak /A. Tafreshi.

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What’s up? Night sky for August 2011

Stargazers with telescopes

This month, Saturn will be the planet to watch in the western part of the sky after sunset.

FOUR PLANETS ARE VISIBLE THIS MONTH, although you’ll have to be quick to spot Mercury, as it starts the month low on the western horizon after sunset and within about a week will have become lost in the Sun’s glare.

Slightly higher in the western sky after sunset is Saturn, shining brightly and visited by the Moon on the 4th.

Jupiter and Mars are still the luminaries of the morning sky—Jupiter high in the north, and Mars low in the north-east. Their brighter sibling, Venus, will not be visible this month, as it is on the opposite side of the Sun from us.

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere.

August 1

Look for the very thin crescent Moon low in the west after sunset. The planet Mercury will be about seven Moon widths above and to the right. Mercury is becoming much harder to see now, and over the next week will sink lower and lower toward the horizon and become lost in the Sun’s glare. The innermost planet will reappear in our morning sky out to the east next month.

August 3

Today the Moon will be at the closest point to Earth in its orbit, called perigee, at 7:00am. The distance between the two bodies will be 365,755 kilometres.

August 4

Look for the Moon and Saturn close together in the west in the early evening sky.

August 5

The Moon and the star Spica—the brightest star in the constellation Virgo—will appear close together tonight. The Moon will be about six Moon widths above the star.

August 6

It is First Quarter Moon today at 9:08pm. First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains throw nice shadows, making it easier to get that 3D effect.

August 8

Now almost three-quarters full, the Moon will be near the star Antares—the brightest star in the constellation Scorpius. Antares has a reddish colour, and to the naked eye it looks a bit like the planet Mars. In fact, its name means ‘rival of Mars’.

Stargazers

Make the most of the late-winter nights by doing some stargazing.

August 14

Full Moon will occur today at 4:58am.

August 16

If you’ve been wondering why Venus doesn’t appear to be in our evening or morning skies, it’s because it is lost in the glare of the Sun. Today marks its ‘superior conjunction’, which means that it is on the exact opposite side of the Sun from us.

August 17

Mercury, which has been lost in the glare of the setting Sun for a while now, today reaches ‘inferior conjunction’, which means that it is exactly between us and the Sun. Mercury will reappear low in the east in the morning sky next month.

August 19

Today the Moon will be at the farthest point from Earth in its orbit, called apogee, at 2:24am. The distance between the two bodies will be 405,159 kilometres.

August 21

Look out to the east this morning, and you’ll see the Moon and what looks like a very bright star above and to its left. That’s not a star; it’s the planet Jupiter. Even if you don’t have a telescope, a normal pair of binoculars should reveal up to four of Jupiter’s largest moons, looking like small pinpricks of light to one or both sides of the planets.

August 22

It is Last Quarter Moon today at 9:55pm.

August 26

If you’re an early riser, take a look out to the east and you’ll see the Moon very close to the planet Mars.

August 29

New Moon occurs today at 1:04pm.

August 31

Today the Moon will again be at the closest point to Earth in its orbit, perigee, this time at 3:36am. The distance between the two bodies will be 360,857 kilometres.

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Images courtesy IAU.

Get SpaceInfo.com.au daily updates by RSS or email! Click the RSS Feed link at the top right-hand corner of this page, and then save the RSS Feed page to your bookmarks. Or, enter your email address (privacy assured) and we’ll send you daily updates. Or follow us on Twitter, @spaceinfo_oz

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What’s up? Night sky for July 2011

Telescope inside a dome at night

Stargazing during winter is chilly, but the nights can often be crisp and clear. And there's plenty to see this month!

THE INNERMOST PLANET, Mercury, has delighted us in the morning sky for the past couple of months, but this month it makes a reappearance in our evening skies, in the west after sunset. It’ll be quite easy to see, above the horizon for around 100 minutes after the Sun sets at the beginning of the month, increasing to almost two-and-a-half hours after the Sun sets by the end of the month.

Also in the evening sky, to the north-west, is Saturn. The famous ringed planet will be on show during the first half of the night, setting around 11:00pm by the end of the month.

In the morning sky to the east, Jupiter and Mars are still putting on a show before sunrise.

Venus is too close to the Sun to be seen this month.

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere.

July 1

There will be a partial eclipse of the Sun today, but you’ll have to be an albatross or maybe a seal in order to see it. That’s because the Sun’s shadow will fall across a remote area of ocean between South Africa and Antarctica. Unless there are some fishing boats or a scientific expedition in the area, it’s entirely possible that no one will witness this eclipse which, at its maximum, will see less than 10% of the Sun’s disc covered by the Moon. And speaking of the Moon, New Moon occurs today at 6:54pm Sydney time (08:54 Universal Time).

 

View of the night sky for July 3, 2011

July 3, 2011, 5:15pm: The thin crescent Moon will sit just above the planet Mercury in the western sky after sunset.

 

July 3

Take a look out to the west after sunset, and you should see the planet Mercury above the horizon, and above it will be the thin crescent Moon.

July 5

Earth reaches aphelion today (or July 4 in the western hemisphere), which is the farthest point from the Sun in our orbit. The distance between Earth and Sun will be 152.1 million kilometres.

There’ll be an interesting sight out to the east in the morning sky today. The planet Mars will appear close to the star Aldebaran. Both are of similar brightness, and both have similar colouring—a sort of orangey-red.

In this evening’s sky, the Moon will sit above the bright star Regulus. Regulus is the brightest star in the constellation Leo. The amazing thing about Regulus is that, although to the naked eye it appears to be one star, in reality it is composed of four stars grouped into two pairs, all gravitationally bound to each other! This sort of thing is not too uncommon—many other stars are members of double, triple or quadruple systems too.

Position of the Moon, Spica and Saturn on July 8, 2011

July 8, 2011, 7:15pm: The Moon will be bracketed by the planet Saturn and the star Spica, in the north-western sky.

 

 

July 8

It is First Quarter Moon today at 4:29pm Sydney time (06:29 Universal Time). First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains throw nice shadows, making it easier to get that 3D effect. Also today, the Moon will be at the closest point to Earth in its orbit, called perigee, at 12:05am (14:05 on July 7, Universal Time). The distance between the two bodies will be 369,565 kilometres. And finally, tonight the Moon will appear reasonably near the planet Saturn.

July 9

A little more than half full, the Moon will appear quite close to the star Spica tonight. Spica, a blue giant star, is the brightest star in the constellation Virgo and the 15th-brightest star in our night sky.

Position of the Moon and Antares on July 12, 2011

July 12, 2011, 8:00pm: High in the northern sky, the Moon and the star Antares (the brightest star in the constellation Scorpius) will appear close together.

 

 

July 12

The now almost-full Moon will appear quite close to the star Antares tonight. Antares means “the rival of Mars’, and it’s not hard to see why, as it’s ruddy colour makes it look just like the fourth planet from the Sun. Antares is a red supergiant star, 800 times bigger than the Sun!

Today, the eighth planet from the Sun, Neptune, has completed one full orbit of the Sun since its discovery in 1846. Neptune takes almost 165 years to complete one circuit of the Sun. Neptune is too faint to be seen with the naked eye, but it is within the range of medium-and-larger backyard telescopes, if you know exactly where to look. This chart, provided by the Royal Astronomical Society of New Zealand, will help you to find it.

July 15

Full Moon occurs today at 4:40pm Sydney time (06:40 Universal Time).

July 20

Mercury reaches its greatest angle from the Sun today, so if you have a clear evening sky, why not take the opportunity to go out and spot it in the west after sunset?

Position of Mercury on July 20, 2011

July 20, 2011, 5:20pm: Mercury will be at its greatest angle from the Sun today, and visible in the west after sunset.

July 22

Today the Moon will reach the farthest point in its orbit around the Earth, called apogee, at a distance of 404,356 kilometres at 8:48am Sydney time (22:48 on July 21, Universal Time).

July 23

It is Last Quarter Moon today at 3:02pm Sydney time (05:02 Universal Time).

July 24

Slightly less than half full, the Moon will appear close to the planet Jupiter in this morning’s sky. Jupiter will be about 12 Moon widths above the Moon. Look a little further east and you’ll see Mars too. In between will be the beautiful star cluster called the Pleiades, also known as the Seven Sisters. Use binoculars or a small telescope and you’ll be delighted with the view.

Position of the Moon, Jupiter and Mars on July 24, 2011

July 24, 2011, 6:20am: The Moon and two planets—Jupiter and Mars—will be visible in the north-eastern sky before sunrise. See if you can spot the Pleiades star cluster as well.

July 25-28

In the western sky after sunset, the planet Mercury will appear close to the star Regulus (see July 5 for more information on this star).

July 28

The crescent Moon will appear very close to the planet Mars in this morning’s sky. They’ll be separated by only three Moon widths.

July 31

New Moon occurs today at 4:40am Sydney time (18:40 on July 30, Universal Time).

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Images courtesy IAU.

Get SpaceInfo.com.au daily updates by RSS or email! Click the RSS Feed link at the top right-hand corner of this page, and then save the RSS Feed page to your bookmarks. Or, enter your email address (privacy assured) and we’ll send you daily updates. Or follow us on Twitter, @spaceinfo_oz

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The carbon planet

Artist's impression of WASP 12b

Artist's impression of WASP 12b, a giant planet 1,200 light-years from Earth. It has more carbon than oxygen.

PLANETS SUCH AS EARTH have more oxygen than carbon, but what if the composition was reversed?

This is a question opened up by a recent discovery of a ‘diamond planet’ by US and UK scientists, led by Nikku Madhusudhan of the Massachusetts Institute of Technology, and including researchers from Belfast’s Queens University and the University of Warwick.

The planet is 1,200 light years away from Earth and was observed using NASA’s Spitzer Space Telescope.

Dr Marek Kukula of the Royal Greenwich Observatory in London, whose role is to interpret and comment on astronomical discoveries made by British scientists, explained that researchers initially used the SuperWASP (Wide Angle Search for Planets) robotic observatories operating continuously, all year around.

They detected the planet, then it was observed with the Spitzer Space telescope, which according to Dr Kukula “detected the heat coming from the planet, and from that heat signature they can tell what this planet is made from.”

Artist's impression of WASP 12b

WASP 12b strange nature suggests there's more than one way to make a planet.

Giant planet

The planet is very different to Earth.

“It’s a giant planet,” explains Dr Kukula, “a gas planet, a bit like Jupiter in our Solar System.”

“But the interesting thing that they’ve discovered is that it has a very different composition to the planets in our Solar System,” he adds. “So where our planets have a half fraction of oxygen then carbon, this planet has it the other way around, it has more carbon than oxygen.”

This suggests that there is more than one way to make a planetary system and the range of planets in the Universe could be much wider than previously thought.

Diamonds and graphite

Dr Kukula says that if there are smaller planets in the same planetary system with a similar composition, rich in carbon, their rocks could be rich in minerals such as carbon and diamonds, unlike Earth which has silica, the sand that rocks on Earth are made from.

“This is where this diamond planet idea comes from, they haven’t actually detected a diamond planet yet,” explains Dr Kukula.

It’s hypothetical, “but you can imagine bizarre landscapes with black graphite rocks lying around and the surface could be covered with tarry liquids rather than water.”

Adapted from information issued by The British Council / NASA / STScI / G. Bacon.

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Family of planets found

Artist's conception of the Kepler-11 system

This artist's conception of the newly discovered planetary system shows six planets orbiting the Sun-like star Kepler-11.

  • The star Kepler-11 has six planets
  • Some of them are not much bigger than Earth
  • Discovery was made using the Kepler space telescope

A REMARKABLE PLANETARY SYSTEM discovered by NASA’s Kepler space telescope has six planets circling a Sun-like star, including five small planets in tightly packed orbits.

Astronomers at the University of California, Santa Cruz, and their co-authors analysed the orbital characteristics of the system to determine the sizes and masses of the planets, and figure out their likely compositions.

All of the information gleaned is based on Kepler’s measurements of the changing brightness of the host star (called Kepler-11) as the planets passed in front of it, producing mini-eclipses called ‘transits’.

The five inner planets in the Kepler-11 system range from 2.3 to 13.5 times the mass of the Earth. Their orbital periods are all less than 50 Earth days, which means they are very close to their host star…so close that they would fit inside the orbit of Mercury in our Solar System.

The sixth planet is larger and farther out, with an orbital period of 118 days and an undetermined mass.

“Not only is this an amazing planetary system, it also validates a powerful new method to measure the masses of planets,” said Daniel Fabrycky, a Hubble postdoctoral fellow at UC Santa Cruz, who led the orbital analysis.

Fabrycky and Jack Lissauer, a scientist at NASA’S Ames Research Centre, are the lead authors of a paper on Kepler-11 published in the February 3 issue of Nature.

“Of the six planets, the most massive are potentially like Neptune and Uranus, but the three lowest mass planets are unlike anything we have in our Solar System,” said Jonathan Fortney, assistant professor of astronomy and astrophysics at UCSC, who led the work on understanding the structure and composition of the planets, along with UCSC graduate students Eric Lopez and Neil Miller.

Comparison of Kepler planet sizes with Earth and Jupiter

Planet comparisons. The six newly discovered Kepler-11 planets are represented by the circles on the bottom row. Earth, Jupiter, and estimated sizes of other Kepler planets are shown above. (RE stands for 'radius of Earth'.)

How the work was done

The Kepler space telescope detects planets that “transit” or pass in front of their host star, causing periodic dips in the brightness of the star as measured by the telescope’s sensitive photometer.

The amount of the brightness reduction tells scientists how big the planet is in terms of its radius. The time between transits tells them its orbital period.

To determine the planets’ masses, Fabrycky analysed slight variations in the orbital periods caused by gravitational interactions among the planets.

The timing of the transits is not perfectly regular, which is an indication that the planets are gravitationally interacting, says Fabrycky. The scientists’ computer models show that the system can remain stable on time scales of millions of years.

Previously, detections of transiting planets have been followed up with observations from powerful ground-based telescopes to confirm the planet and determine its mass using Doppler spectroscopy, which measures the “wobble” in the motion of the star caused by the gravitational tug of the planet.

Artist's drawing of the Kepler space telescope

Artist's drawing of the Kepler space telescope

With Kepler-11, however, the planets are too small and the star (2,000 light-years away) is too faint for this method to work.

And this is likely to be the case with many of the planets detected by the Kepler mission, the main goal of which is to find small, Earth-size planets in the habitable zones of their stars. See our related story.

A remarkable system

More than 100 transiting planets have been observed by Kepler and other telescopes, but the vast majority of them are Jupiter-like gas giants, and almost all of them are in (so far as is known) single-planet systems.

The Kepler-11 system is remarkable in terms of the number of planets, their small sizes, and their closely packed orbits. Before this, astronomers had determined both size and mass for only three exoplanets smaller than Neptune.

Now, this single planetary system has added five more.

The sixth planet in Kepler-11 is separated enough from the others that the orbital perturbation method can’t be used to determine its mass, Fabrycky said.

As is the case in our Solar System, all of the Kepler-11 planets orbit in more or less the same plane. This finding reinforces the idea that planets form in flattened discs of gas and dust (‘stellar discs’) spinning around a star, and the disc pattern is conserved after the planets have formed, Fabrycky said.

“The ‘coplanar’ orbits in our Solar System inspired this theory in the first place, and now we have another good example. But that and the Sun-like star are the only parts of Kepler-11 that are like the Solar System,” he said.

What are they like?

The densities of the planets provide clues to their compositions. All six planets have densities lower than Earth’s.

“It looks like the inner two could be mostly water, with possibly a thin skin of hydrogen-helium gas on top, like mini-Neptunes,” Fortney said. “The ones farther out have densities less than water, which seems to indicate significant hydrogen-helium atmospheres.”

Diagram comparing the Kepler-11 system to our Solar System

Diagram comparing the Kepler-11 system to our Solar System, showing how Kepler-11's five small, inner planets would fit within the orbit of Mercury in our Solar System.

That’s surprising, because a small, hot planet should have a hard time holding onto a lightweight atmosphere.

These planets are pretty hot because of their close orbits, and the hotter it is the more gravity you need to keep the atmosphere,” Fortney said.

“My students and I are still working on this, but our thoughts are that all these planets probably started with more massive hydrogen-helium atmospheres, and we see the remnants of those atmospheres on the ones farther out,” Fortney added. “The ones closer in have probably lost most of it.”

Comparing Neptunes and Jupiters

One reason a six-planet system is so exciting is that it allows scientists to make these kinds of comparisons among planets within the same system.

“That’s really powerful, because we can work out what’s happened to this system as a whole,” Fortney said. “Comparative planetary science is how we’ve come to understand our Solar System, so this is much better than just finding more solitary hot Jupiters around other stars.”

For example, the presence of small planets with hydrogen-helium atmospheres suggests that this system formed relatively quickly, he said. Studies indicate that stellar discs lose their hydrogen and helium gas within about 5 million years.

“So it tells us how quickly planets can form,” Fortney said.

The inner planets are so close together that it seems unlikely they formed where they are now, he added.

“At least some must have formed farther out and migrated inward. If a planet is embedded in a disc of gas, the drag on it leads to the planet spiralling inward over time. So formation and migration had to happen early on.”

Adapted from information issued by UCSC.

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Planets galore!

Artist's impression of an exoplanet system

Artist's impression of an exoplanet system. NASA's Kepler space telescope has now found 1,235 planet candidates within a small region of our Milky Way galaxy.

NASA’S KEPLER SPACE TELESCOPE has discovered its first Earth-size planet candidates and its first candidates in the habitable zone, a region where liquid water could exist on a planet’s surface.

Five of the potential planets are nearly Earth-size and orbit in the habitable zone of smaller, cooler stars than our Sun.

Candidates require follow-up observations to verify they are actual planets.

Kepler also found six confirmed planets orbiting a Sun-like star, Kepler-11. This is the largest group of transiting planets orbiting a single star yet discovered outside our Solar System. See our related story.

“In one generation we have gone from extraterrestrial planets being a mainstay of science fiction, to the present, where Kepler has helped turn science fiction into today’s reality,” said NASA Administrator Charles Bolden.

The discoveries are part of several hundred new planet candidates identified in new Kepler mission science data, released on Tuesday, February 1.

Diagram explaining a Kepler transit observation

Kepler detects the dip in starlight as a planet passes in front of a star, called a 'transit'.

A multitude of planets

Kepler looks for signs of planets by measuring tiny decreases in the brightness of stars caused by planets crossing in front of them. This is known as a transit.

The planets are too far away and too small for images of them to be made, but Kepler’s transit method can detect their presence.

The findings increase the number of planet candidates identified by Kepler to-date to 1,235. Of these, 68 are approximately Earth-size; 288 are super-Earth-size; 662 are Neptune-size; 165 are the size of Jupiter and 19 are larger than Jupiter.

Of the 54 new planet candidates found in the habitable zone, five are nearly Earth-sized. The remaining 49 habitable zone candidates range from super-Earth size—up to twice the size of Earth—to larger than Jupiter.

The findings are based on the results of observations conducted May 12 to September 17, 2009, of more than 156,000 stars in Kepler’s field of view, which covers approximately 1/400 of the sky.

“The fact that we’ve found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting Sun-like stars in our galaxy,” said William Borucki of NASA’s Ames Research Centre, the mission’s science principal investigator.

“We went from zero to 68 Earth-sized planet candidates and zero to 54 candidates in the habitable zone, some of which could have moons with liquid water.”

Star with a large family

Among the stars with planetary candidates, 170 show evidence of multiple planetary candidates.

Kepler-11, located approximately 2,000 light years from Earth, is the most tightly packed planetary system yet discovered. All six of its confirmed planets have orbits smaller than Venus, and five of the six have orbits smaller than Mercury’s.

The only other star with more than one confirmed transiting planet is Kepler-9, which has three.

Diagram comparing Kepler-11 system with the Solar System

A comparison of the orbits of the six planets in the Kepler-11 system with the orbits of Mercury and Venus in our Solar System.

“Kepler-11 is a remarkable system whose architecture and dynamics provide clues about its formation,” said Jack Lissauer, a planetary scientist and Kepler science team member at Ames.

“These six planets are mixtures of rock and gases, possibly including water. The rocky material accounts for most of the planets’ mass, while the gas takes up most of their volume,” he added.

“By measuring the sizes and masses of the five inner planets, we determined they are among the lowest-mass confirmed planets beyond our Solar System.”

All of the planets orbiting Kepler-11 are larger than Earth, with the largest ones being comparable in size to Uranus and Neptune. The innermost planet, Kepler-11b, is ten times closer to its star than Earth is to the Sun.

Moving outward, the other planets are Kepler-11c, Kepler-11d, Kepler-11e, Kepler-11f, and the outermost planet, Kepler-11g, which is half as far from its star as Earth is from the Sun.

The planets Kepler-11d, Kepler-11e and Kepler-11f have a significant amount of light gas, which indicates that they formed within a few million years of the system’s formation.

Kepler field-of-view star chart

This star chart illustrates the large patch of sky that NASA's Kepler mission is staring at during its three-and-a-half-year mission. The planet hunter's full field of view covers 100 square degrees.

Follow up needed

Since transits of planets in the habitable zone of Sun-like stars occur about once a year and require three transits for verification, it is expected to take three years to locate and verify Earth-size planets orbiting Sun-like stars.

The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planetary candidates and other objects of interest the spacecraft finds.

The star field that Kepler observes in the constellations Cygnus and Lyra can only be seen from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.

“The historic milestones Kepler makes with each new discovery will determine the course of every exoplanet mission to follow,” said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington.

Adapted from information issued by NASA. Image credits NASA, Tim Pyle, Software Bisque, G. Bacon/STScI.

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Square Kilometre Array is coming

THE SQUARE KILOMETRE ARRAY (SKA) will be a huge network of radio telescope antennae, all working in concert to provide unprecedentedly precise and sensitive views of the universe.

Able to see from the present day almost all the way to the Big Bang, and everything in between, it will answer fundamental questions about the origin of stars, galaxies and planetary systems.

Comprising thousands of separate antennae, connected electronically to form one large antenna thousands of kilometres wide, the SKA will have to be built on a large patch of real estate. Two regions are competing for the “hosting” rights—a joint Australia–New Zealand bid, and a bid comprising a number of southern African countries.

It is expected the decision about where the SKA is to be built will be made in 2012.

Related stories:

The Square Kilometre Array

Aussies and Kiwis forge cosmic connection

World’s biggest telescope – the Aussie bid

Video animation produced by Swinburne Astronomy Productions.

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Airborne observatory reaches milestone

SOFIA observatory

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a modified Boeing 747SP, equipped with a 2.5-metre-diameter telescope.

NASA’s STRATOSPHERIC OBSERVATORY for Infrared Astronomy, or SOFIA, has completed the first of three science flights to demonstrate the aircraft’s potential to make discoveries about the universe.

SOFIA is a heavily modified Boeing 747SP that cruises at altitudes between 39,000 and 45,000 feet. At that altitude, it is above most of the atmosphere that interferes with astronomical observations.

In particular, it is above most of the water vapour that inhibits observations at infrared wavelengths.

It will enable researchers to better understand a wide range of astronomical phenomena including how stars and planets are born, how organic substances form in interstellar space, and how supermassive black holes feed and grow.

“These initial science flights mark a significant milestone in SOFIA’s development and ability to conduct peer-reviewed science observations,” said NASA Astrophysics Division Director Jon Morse.

“We anticipate a number of important discoveries from this unique observatory, as well as extended investigations of discoveries by other space telescopes.”

SOFIA is fitted with a 2.5-metre-diameter telescope that views the sky through a hatch toward the back of the aircraft.

The telescope’s instruments can analyse light from a wide range of celestial objects, including warm interstellar gas and dust of bright star forming regions, by observing wavelengths between 0.3 and 1,600 microns. (A micron equals one millionth of a metre.) For comparison, the human eye sees light with wavelengths between 0.4 and 0.7 microns.

The airborne observatory is an international collaboration between NASA and the German Aerospace Centre, Deutsches Zentrum fur Luft und Raumfahrt (DLR).

Adapted from information issued by NASA.

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