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Fried Egg nebula home to hypergiant

ASTRONOMERS HAVE TAKEN AN IMAGE of a colossal star that belongs to one of the most rare classes of stars in the Universe…the yellow hypergiants.

The new picture is the best ever taken of a star in this class and shows for the first time a huge dusty double shell surrounding the star.

The star and its shells resemble an egg white around a yolky centre, leading the astronomers to nickname the object the Fried Egg Nebula.

The monster star, known to astronomers as IRAS 17163-3907, has a diameter about a thousand times bigger than our Sun.

And at a distance of about 13,000 light-years from Earth, it is the closest yellow hypergiant found to date and new observations show it shines some 500,000 times more brightly than the Sun.

Unexpected discovery

Yellow hypergiants are in an extremely active phase of their evolution, undergoing a series of explosive events. This particular star has ejected four times the mass of the Sun in just a few hundred years.

The material flung out during these bursts has formed the extensive double shell of the nebula, which is made of dust rich in silicates and mixed with gas.

Fried Egg Nebula

This picture of the nebula around a rare yellow hypergiant star called IRAS 17163-3907 is the best ever taken of a star in this class and shows for the first time a huge dusty double shell surrounding the star. The star and its shells resemble an egg white around a yolky centre, leading astronomers to nickname the object the Fried Egg Nebula.

“This object was known to glow brightly in the infrared but, surprisingly, nobody had identified it as a yellow hypergiant before,” said Eric Lagadec (European Southern Observatory, ESO), who led the team that produced the new images using ESO’s Very Large Telescope (VLT).

The next supernova?

If the Fried Egg Nebula were placed in the centre of the Solar System the Earth would lie deep within the star itself and the planet Jupiter would be orbiting just above its surface.

The much larger surrounding nebula would engulf all the planets and dwarf planets and even some of the comets that orbit far beyond the orbit of Neptune.

The outer shell has a radius of 10,000 times the distance from the Earth to the Sun.

The star is likely to soon die an explosive death—it will be one of the next supernova explosions in our galaxy.

Supernovae provide much-needed chemicals to the surrounding interstellar environment and the resulting shock waves can kick start the formation of new stars.

Adapted from information issued by ESO / E. Lagadec.

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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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Gallery: A fluffy galaxy

Galaxy NGC 3521

Galaxy NGC 3521 is relatively nearby, at a distance of only 35 million light-years. It's patchy spiral arms give it a fluffy look.

IT’S 35 MILLION LIGHT-YEARS AWAY and 50,000 light-years wide. It’s the spiral galaxy NGC 3521, a spectacular object with a bright and compact core or nucleus, surrounded by richly detailed spiral structure.

This new picture from the European Southern Observatory’s (ESO) Very Large Telescope shows that the most distinctive features of NGC 3521 are its long spiral arms, which are dotted with star-forming regions and interspersed with veins of dust.

The arms are rather irregular and patchy, making NGC 3521 a typical example of a ‘flocculent spiral galaxy’.

These types of galaxies have ‘fluffy’ spiral arms that contrast with the sweeping arms of ‘grand-design spirals’ such as the famous Whirlpool galaxy or M 51, discovered by Charles Messier.

NGC 3521 is bright and relatively close-by, and can easily be seen with a small telescope such as the one used by Messier to catalogue a series of hazy astronomical objects when he was searching for comets in the 1700s.

Strangely, the French astronomer seems to have missed this spiral even though he identified several other galaxies of similar brightness in the constellation of Leo.

It was only in the year that Messier published the final version of his catalogue, 1784, that another famous astronomer, William Herschel, discovered NGC 3521 early on in his more detailed surveys of the northern skies.

Through his larger, 47cm aperture, telescope, Herschel saw a “bright centre surrounded by nebulosity,” according to his observation notes.

In this new VLT picture, colourful, yet ill-defined spiral arms replace Herschel’s “nebulosity”. Older stars dominate the reddish area in the centre while young, hot blue stars permeate the arms further away from the core.

Download wallpapers of the spiral galaxy NGC 3521:

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Adapted from information issued by ESO / O. Maliy.

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Superstar spreads its wings

Nebula surrounding Betelgeuse

A nebula surrounds the red supergiant star Betelgeuse. The nebula forms as the behemoth sheds material into space. The black disc corresponds to a very bright part of the image that was masked to allow the fainter nebula to be seen. Earlier observations of the heart of the nebula can be seen in the central disc.

ASTRONOMERS HAVE IMAGED a complex and bright nebula around the supergiant star Betelgeuse in greater detail than ever before. This structure, which resembles flames emanating from the star, is formed as the behemoth sheds its gas into space.

Betelgeuse, a red supergiant in the constellation Orion, is one of the brightest stars in the night sky. It is also one of the biggest, being almost the size of the orbit of Jupiter—about four and half times the diameter of the Earth’s orbit.

Hubble image of the surface of Betelgeuse

This image of Betelgeuse, released in 1996, was the first direct image of a star other than the Sun, and it was made with the Hubble Space Telescope. The image revealed a mysterious hot spot—more than ten times the diameter of Earth—on the stellar behemoth's surface.

The Very Large Telescope (VLT) image shows the surrounding nebula, which is much bigger than the supergiant itself, stretching 60 billion kilometres away from the star’s surface—about 400 times the distance of the Earth from the Sun.

Red supergiants like Betelgeuse represent one of the last stages in the life of a massive star. In this short-lived phase, the star increases in size, and expels gas into space at a tremendous rate—it sheds immense quantities of material (about the mass of the Sun) in just 10,000 years.

The process by which material is shed from a star like Betelgeuse involves two processes. The first is the formation of huge plumes of gas (although much smaller than the nebula now imaged) extending into space from the star’s surface.

The other, which is behind the ejection of the plumes, is the vigorous up and down movement of giant bubbles in Betelgeuse’s atmosphere—like boiling water circulating in a pot.

Raw material for new planets

Earlier images using an instrument called NACO, revealed the plumes close in to the star. The new results show that those plumes are probably connected to structures in the outer nebula now imaged at infrared wavelengths with a different instrument, VISIR.

The nebula cannot be seen at visible light wavelengths, as the glare of Betelgeuse completely outshines it.

The irregular shape of the nebula indicates that the star did not eject its material in a symmetric way. The bubbles of stellar material and the giant plumes they originate may be responsible for the clumpy look of the nebula.

The material visible in the new image is most likely made of silicate and alumina dust. This is the same material that forms most of the crust of the Earth and other rocky planets. At some time in the distant past, the silicates that eventually formed the Earth were expelled by a massive (and now extinct) star similar to Betelgeuse.

Adapted from information issued by ESO / P. Kervella / Andrea Dupree (Harvard-Smithsonian CfA), Ronald Gilliland (STScI), NASA and ESA.

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Hidden cosmic treasures

OBSERVATIONS MADE WITH the European Southern Observatory’s (ESO) powerful ground-based telescopes are veritable treasures, stored in a huge archive usually only visited by professional astronomers on a mission.

And yet, an amateur astrophotographer from Russia managed to uncover a real gem from ESO’s Hidden Treasures, winning a trip to Chile to observe with the Very Large Telescope and take part in the observations.

How did he manage it? And could you do the same?

This podcast episode takes you behind the scenes of ESO’s Hidden Treasures competition and shows you how a group of determined and talented amateur astrophotographers managed to find and produce stunning astronomy pictures.

Adapted from information issued by ESO.

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Really cool stars

Artist’s impression of CFBDSIR 1458+10

Artist’s impression of the pair of brown dwarfs named CFBDSIR 1458+10. Observations suggest this is the coolest pair of brown dwarfs found so far. The colder of the two (background) could have a temperature similar to that of a cup of freshly made tea.

  • Brown dwarfs are halfway between big planets and small stars
  • They don’t shine, but give off only a small amount of heat
  • Newly found brown dwarf seems to be the coldest yet discovered

ASTRONOMERS HAVE FOUND a new candidate for the coldest known star—a ‘brown dwarf’ in a binary star system that has about the same temperature as a freshly made cup of tea.

That’s hot in human terms, but extraordinarily cold for the surface of a star.

This object is cool enough to begin crossing the blurred line dividing small, cold stars from big, hot planets.

Brown dwarfs are essentially failed stars—they don’t have enough mass for gravity to trigger the nuclear reactions that make stars shine.

The newly discovered brown dwarf, identified as CFBDSIR 1458+10B, is the dimmer member of a binary brown dwarf system located just 75 light-years from Earth.

The powerful X-shooter spectrograph on the European Southern Observatory’s (ESO) Very Large Telescope (VLT) was used to show that the object was very cool by brown dwarf standards.

“We were very excited to see that this object had such a low temperature, but we couldn’t have guessed that it would turn out to be a double system and have an even more interesting, even colder [star],” said Philippe Delorme of the Institut de planétologie et d’astrophysique de Grenoble (CNRS/Université Joseph Fourier), a co-author of the paper.

Keeping its cool

CFBDSIR 1458+10 is the name of the binary system. The individual stars are known as CFBDSIR 1458+10A and CFBDSIR 1458+10B, with the latter the fainter and cooler of the two. They seem to be orbiting each other at a separation of about three times the distance between the Earth and the Sun with a period of about thirty years.

Brown dwarf binary CFBDSIR 1458+10

Actual image of the brown dwarf binary CFBDSIR 1458+10, obtained using the Laser Guide Star (LGS) Adaptive Optics system on the Keck II Telescope in Hawaii. Adaptive optics cancels out much of Earth’s atmospheric interference, improving the image sharpness by a factor of 10.

The dimmer of the two dwarfs has now been found to have a temperature of about 100 degrees Celsius — the boiling point of water, and not much different from the temperature inside a sauna.

By comparison the temperature of the surface of the Sun is about 5,500 degrees Celsius.

“At such temperatures we expect the brown dwarf to have properties that are different from previously known brown dwarfs and much closer to those of giant exoplanets—it could even have water clouds in its atmosphere,” said Michael Liu of the University of Hawaii’s Institute for Astronomy, who is lead author of the paper describing this new work.

“In fact, once we start taking images of gas-giant planets around Sun-like stars in the near future, I expect that many of them will look like CFBDSIR 1458+10B.”

Three telescopes needed

Unravelling the secrets of this unique object involved exploiting the power of three different telescopes. CFBDSIR 1458+10 was first found to be a binary using the Laser Guide Star (LGS) Adaptive Optics system on the Keck II Telescope in Hawaii.

Liu and his colleagues then employed the Canada–France–Hawaii Telescope, also in Hawaii, to determine the distance to the brown dwarf duo using an infrared camera. Finally the ESO VLT was used to study the object’s infrared spectrum and measure its temperature.

The hunt for cool objects is a very active astronomical hot topic. The Spitzer Space Telescope has recently identified two other very faint objects as other possible contenders for the coolest known brown dwarfs, although their temperatures have not been measured so precisely.

Future observations will better determine how these objects compare to CFBDSIR 1458+10B.

Liu and his colleagues are planning to observe CFBDSIR 1458+10B again to better determine its properties and to begin mapping the binary’s orbit, which, after about a decade of monitoring, should allow astronomers to determine the binary’s mass.

Adapted from information issued by ESO / Michael Liu (University of Hawaii) / L. Calçada.

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Spiral galaxy seen in a new light

Infrared view of NGC 1365

An infrared view of NGC 1365, a beautiful barred spiral galaxy in the Fornax cluster of galaxies, about 60 million light-years from Earth.

  • Galaxy NGC 1365, the Great Barred Spiral Galaxy
  • 200,000 light-years wide, with two huge spiral arms
  • Located 60 million light-years from Earth

A new image taken with the powerful HAWK-I camera on the European Southern Observatory’s (ESO’s) Very Large Telescope in Chile shows the beautiful “barred spiral” galaxy NGC 1365 in infrared light.

NGC 1365 is a member of the Fornax cluster of galaxies, about 60 million light-years from Earth.

NGC 1365 is one of the best-known and most-studied barred spiral galaxies, sometimes nicknamed the Great Barred Spiral Galaxy because of its strikingly perfect form…a straight “bar” or middle section and two prominent outer spiral arms.

Closer to the centre there is also a second spiral structure, and the galaxy as a whole is laced with delicate lanes of interstellar dust.

Astronomers consider it an excellent “laboratory” for studying how spiral galaxies form and evolve.

The new infrared images from HAWK-I are less affected by the dust that obscures parts of the galaxy than images taken at visible light wavelengths, and they reveal very clearly the glow from vast numbers of stars in both the bar and the spiral arms.

The images were acquired to help astronomers understand the complex flow of gas within the galaxy and how it affects the reservoirs of gas from which new stars can form.

The huge bar disturbs the shape of the gravitational field of the galaxy and this leads to regions where gas becomes compressed, triggering the formation of new stars.

See the full-size, high-resolution version of the image (suitable for PC wallpaper) here.

Visible light and infrared views of NGC 1365

This comparison shows a visible-light image (left) of NGC 1365 along with the new infrared view (right). The infrared view "peels away" the veil of dust to reveal more stars beneath.

Black hole hidden in the core

Many huge young star clusters are visible in the main spiral arms, each containing hundreds or thousands of bright young stars that are less than 10 million years old.

The galaxy is too remote for single stars to be seen—most of the tiny clumps visible in the picture are really clusters of stars.

While the bar of the galaxy comprises mainly older stars long past their prime, many new stars are born in stellar “nurseries” of gas and dust in the inner spiral close to the core. Over the whole galaxy, stars are forming at a rate of about three times the mass of our Sun per year.

The bar also funnels gas and dust gravitationally into the very centre of the galaxy, where astronomers have found evidence for the presence of a super-massive black hole, well hidden among myriads of intensely bright new stars.

Here’s a video that zooms in on NGC 1365, alternating between visible wavelength and infrared wavelength views:

NGC 1365, including its two huge outer spiral arms, is around 200,000 light-years across. Different parts of the galaxy take different times to make a full rotation around the core, with the outer parts of the bar taking about 350 million years to complete one circuit.

NGC 1365 and other galaxies of its type have come to more prominence in recent years with new observations indicating that our Milky Way galaxy could also be of the barred spiral type.

Such galaxies are quite common—two thirds of spiral galaxies are barred according to recent estimates. Studying them can help astronomers understand our own galactic home.

Adapted from information issued by ESO / P. Grosbøl.

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Amazing telescope video

The European Southern Observatory has telescopes located at several sites in Chile, South America. Prime among them is the Very Large Telescope, or VLT.

The VLT is actually a number of telescopes that can work individually or in concert.

There are the four huge, main telescopes—each with main, or primary, mirrors that are 8.2 metres in diameter—plus several auxiliary telescopes with mirrors 1.8 metres in diameter.

The main mirrors are huge, round pieces of very special glass, carefully formed into shape with a gentle parabolic curve on their surface. Light coming in from space reflects off this curved surface and is brought to a focus.

But the light doesn’t reflect from the glass—it bounces off an extremely thin layer of aluminium that has been deposited on the glass, to give it a shiny, reflective surface.

Over time, this layer becomes tarnished and needs to be removed and replaced. The video above shows what’s involved in this process—and it’s a very involved process indeed!

A longer, utterly fascinating and highly-recommended video (but with no narration) can be found on the ESO web site.

Story by Jonathan Nally, editor SpaceInfo.com.au

Images and video courtesy ESO.

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3D view of exploding star

Artist’s impression of the material surrounding SN1987A

This artist’s impression of the material around a recently exploded star, known as Supernova 1987A (or SN 1987A), is based on observations which have for the first time revealed a three dimensional view of the distribution of the expelled material. This image shows the different elements present in SN 1987A: two outer rings, one inner ring and the deformed, innermost expelled material.

Astronomers using European Southern Observatory’s (ESO) Very Large Telescope (VLT) have for the first time obtained a three-dimensional view of the distribution of the innermost material expelled by a recently exploded star.

The original blast was not only powerful, according to the new results. It was also more concentrated in one particular direction.

This is a strong indication that the supernova must have been very turbulent, supporting the most recent computer models.

Unlike the Sun, which will die rather quietly, massive stars arriving at the end of their brief life explode as supernovae, hurling out a vast quantity of material.

An animation showing a 3D view of the supernova remnant.

An animation showing a 3D view of the supernova remnant.

In this class, Supernova 1987A (SN 1987A) in the nearby Large Magellanic Cloud galaxy occupies a very special place. Seen in 1987, it was the first supernova for 383 years bright enough to be seen in the sky with just the naked eye.

Because of its relative closeness, it has been possible for astronomers to study the explosion of a massive star and its aftermath in more detail than ever before.

SN 1987A has been a bonanza for astrophysicists. It provided several notable observational ‘firsts’: the detection of neutrinos from the collapsing inner stellar core triggering the explosion; the identification on archival photographic plates of the star before it exploded; the signs of a lopsided explosion; the direct observation of the radioactive elements produced during the blast; observation of the formation of dust in the supernova, as well as the detection of the gas surrounding the star.

A lopsided blast

New observations making use of a unique instrument, SINFONI, on the VLT have provided even deeper knowledge of this amazing event, as astronomers have now been able to make the first-ever 3D reconstruction of the central parts of the exploding material.

This view shows that the explosion was stronger and faster in some directions than others, leading to an irregular shape with some parts stretching out further into space.

Time sequence of Hubble images of SN1987A

A time sequence of Hubble Space Telescope images, taken in the 9 years from 1994 to 2003, showing the collision of the expanding supernova blast with a ring of dense material flung off by the star 20,000 years before it exploded.

The first material to be ejected from the explosion travelled at an incredible 100 million km per hour, which is about a tenth of the speed of light or around 100,000 times faster than a passenger jet.

Even at this breakneck speed it has taken the blast 10 years to reach a previously existing ring of gas and dust puffed out much earlier from the dying star. The images also demonstrate that another blast wave is travelling ten times more slowly and is being heated by radioactive elements created in the explosion.

“We have established the velocity distribution of the inner ejecta of Supernova 1987A,” says lead author Karina Kjær. “Just how a supernova explodes is not very well understood, but the way the star exploded is imprinted on this inner material. We can see that this material was not ejected symmetrically in all directions, but rather seems to have had a preferred direction. Besides, this direction is different to what was expected from the position of the ring.”

Such asymmetric behaviour was predicted by some of the most recent computer models of supernovae, which found that large-scale instabilities occur during the explosion. The new observations are thus the first direct confirmation of such models.

Adapted from information issued by ESO / L. Calçada.

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Planet’s perfect storm

Artist’s impression of H209458b and its Sun-like star

Astronomers have measured a superstorm in the atmosphere of a distant planet. This artist’s impression shows the Jupiter-like planet and its Sun-like host star.

  • HD209458b is a planet 150 light-years from Earth
  • 60% the mass of Jupiter, with similar carbon content
  • Fierce winds detected, driven by high temperatures

Astronomers studying a planet 150 light-years from Earth have detected a huge, heat-driven storm raging in its atmosphere.

HD209458b is about 60% as massive as Jupiter, orbiting a Sun-like star at a distance of only 1/20th that of the Sun to the Earth.

The planet always keeps one side facing its star, making that side very hot, while the other is much cooler. In fact, the intense heat from the star makes the planet’s dayside around 1,000 degrees Celsius.

“On Earth, big temperature differences inevitably lead to fierce winds, and as our new measurements reveal, the situation is no different on HD209458b,” says team member Simon Albrecht.

“HD209458b is definitely not a place for the faint-hearted. By studying the poisonous carbon monoxide gas with great accuracy we found evidence for a super wind, blowing at a speed of 5,000 to 10,000 km per hour,” says Ignas Snellen, who led the team of astronomers.

High-precision observations

HD209458b was the first exoplanet (ie. one that orbits a star other than our Sun) to be found “transiting”. Every 3.5 days the planet moves in front of its star, blocking a small portion of the starlight during a three-hour period.

During these events, a tiny fraction of the starlight filters through the planet’s atmosphere, leaving an imprint.

VLT

Enclosures of the four main VLT telescopes

A team of astronomers from the Leiden University, the Netherlands Institute for Space Research (SRON), and MIT in the United States, used the European Southern Observatorys’ (ESO) Very Large Telescope and its powerful CRIRES spectrograph to detect and analyse these faint fingerprints, studying the planet for about five hours as it passed in front of its star.

CRIRES enabled the astronomers to measure the spectrum of carbon monoxide gas in the planet’s atmosphere to high precision. “This high precision allows us to measure the velocity of the carbon monoxide gas for the first time using the Doppler effect,” says team member Remco de Kok.

Similar to Jupiter and Saturn

The astronomers achieved several other firsts, including directly measuring the velocity of the planet as it orbits its star.

“In general, the mass of an exoplanet is determined by measuring the wobble of the star and assuming a mass for the star, according to theory. Here, we have been able to measure the motion of the planet as well, and thus determine both the mass of the star and of the planet,” says co-author Ernst de Mooij.

Also for the first time, the astronomers have measured how much carbon is present in the atmosphere of this planet.

“It seems that H209458b is actually as carbon-rich as Jupiter and Saturn. This could indicate that it was formed in the same way,” says Snellen.

“In the future, astronomers may be able to use this type of observation to study the atmospheres of Earth-like planets, to determine whether life also exists elsewhere in the Universe.”

Adapted from information issued by ESO / L. Calçada.