Category Archives: Astronomy

Asteroids & Comets, Astronomy, Space Science

ESO: Observatory sees daily changes in bright spots on Ceres

March 16, 2016 TopSpacer

The latest report from ESO (European Southern Observatory):

Unexpected Changes of Bright Spots on Ceres Discovered

Observations made using the HARPS spectrograph at ESO’s La Silla Observatory in Chile have revealed unexpected changes in the bright spots on the dwarf planet Ceres. Although Ceres appears as little more than a point of light from the Earth, very careful study of its light shows not only the changes expected as Ceres rotates, but also that the spots brighten during the day and also show other variations. These observations suggest that the material of the spots is volatile and evaporates in the warm glow of sunlight.

This artist’s impression is based on a detailed map of the surface compiled from images taken from NASA’s Dawn spacecraft in orbit around the dwarf planet Ceres. It shows the very bright patches of material in the crater Occator and elsewhere. New observations using the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile have revealed unexpected daily changes on these spots, suggesting that they change under the influence of sunlight as Ceres rotates.

Ceres is the largest body in the asteroid belt between Mars and Jupiter and the only such object classed as a dwarf planet. NASA’s Dawn spacecraft has been in orbit around Ceres for more than a year and has mapped its surface in great detail. One of the biggest surprises has been the discovery of very bright spots, which reflect far more light than their much darker surroundings [1]. The most prominent of these spots lie inside the crater Occator and suggest that Ceres may be a much more active world than most of its asteroid neighbours.

This artist’s impression video [click here for higher resolution versions] is based on a detailed map of the surface compiled from images taken from NASA’s Dawn spacecraft in orbit around the dwarf planet Ceres. It shows the very bright patches of material in the crater Occator and elsewhere. New observations using the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile have revealed unexpected daily changes on these spots, suggesting that they change under the influence of sunlight as Ceres rotates.

This illustration shows how the features in the spectrum of the light reflected from the bright spots is alternately red and blue shifted slightly compared to the average light of Ceres as it rotates. This very subtle effect has been measured from the ground using the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile. The effect has been greatly exaggerated to make it visible and excludes the much brighter light coming from the rest of the disc of Ceres. Credit: ESO/L.Calçada/NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/Steve Albers

New and very precise observations using the HARPS spectrograph at the ESO 3.6-metre telescope at La Silla, Chile, have now not only detected the motion of the spots due to the rotation of Ceres about its axis, but also found unexpected additional variations suggesting that the material of the spots is volatile and evaporates in sunlight.

eso1609b[1] — This image taken from NASA’s Dawn spacecraft in orbit around the dwarf planet Ceres shows the very bright patches of material in the crater Occator and elsewhere. New observations using the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile have revealed unexpected daily changes on these spots, suggesting that they change under the influence of sunlight. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The lead author of the new study, Paolo Molaro, at the INAF–Trieste Astronomical Observatory, takes up the story:

“As soon as the Dawn spacecraft revealed the mysterious bright spots on the surface of Ceres, I immediately thought of the possible measurable effects from Earth. As Ceres rotates the spots approach the Earth and then recede again, which affects the spectrum of the reflected sunlight arriving at Earth.”

Ceres spins every nine hours and calculations showed that the effects due to the motion of the spots towards and away from the Earth caused by this rotation would be very small, of order 20 kilometres per hour. But this motion is big enough to be measurable via the Doppler effect with high-precision instruments such as HARPS.

This artist’s impression video is based on a detailed map of the surface compiled from images taken from NASA’s Dawn spacecraft in orbit around the dwarf planet Ceres. It shows the very bright patches of material in the crater Occator and elsewhere. New observations using the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile have revealed unexpected daily changes on these spots, suggesting that they change under the influence of sunlight as Ceres rotates. Credit: ESO/L.Calçada/NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/Steve Albers

The team observed Ceres with HARPS for a little over two nights in July and August 2015. “The result was a surprise,”adds Antonino Lanza, at the INAF–Catania Astrophysical Observatory and co-author of the study.

“We did find the expected changes to the spectrum from the rotation of Ceres, but with considerable other variations from night to night.”

The team concluded that the observed changes could be due to the presence of volatile substances that evaporate under the action of solar radiation [2]. When the spots inside the Occator crater are on the side illuminated by the Sun they form plumes that reflect sunlight very effectively. These plumes then evaporate quickly, lose reflectivity and produce the observed changes. This effect, however, changes from night to night, giving rise to additional random patterns, on both short and longer timescales.

If this interpretation is confirmed Ceres would seem to be very different from Vesta and the other main belt asteroids. Despite being relatively isolated, it seems to be internally active [3]. Ceres is known to be rich in water, but it is unclear whether this is related to the bright spots. The energy source that drives this continual leakage of material from the surface is also unknown.

Dawn is continuing to study Ceres and the behaviour of its mysterious spots. Observations from the ground with HARPS and other facilities will be able to continue even after the end of the space mission.

Notes

[1] Bright spots were also seen, with much less clarity, in earlier images of Ceres from the NASA/ESA Hubble Space Telescope taken in 2003 and 2004.

[2] It has been suggested that the highly reflective material in the spots on Ceres might be freshly exposed water ice or hydrated magnesium sulphates.

[3] Many of the most internally active bodies in the Solar System, such as the large satellites of Jupiter and Saturn, are subjected to strong tidal effects due to their proximity to the massive planets.

Astronomy

ESO: Sharpest view ever of dusty disc around an aging star

March 9, 2016 TopSpacer

The latest European Southern Observatory (ESO) report:

Sharpest View Ever of Dusty Disc Around Aging Star
VLTI finds discs around aging stars similar to those around young ones

The Very Large Telescope Interferometer at ESO’s Paranal Observatory in Chile has obtained the sharpest view ever of the dusty disc around an aging star. For the first time such features can be compared to those around young stars — and they look surprisingly similar. It is even possible that a disc appearing at the end of a star’s life might also create a second generation of planets.

The Very Large Telescope Interferometer at ESO’s Paranal Observatory in Chile has obtained the sharpest view ever of the dusty disc around the close pair of aging stars IRAS 08544-4431. For the first time such discs can be compared to the discs around young stars — and they look surprisingly similar. It is even possible that a disc appearing at the end of a star’s life might also create a second generation of planets. The inset shows the VLTI reconstructed image, with the brighter central star removed. The background view shows the surroundings of this star in the constellation of Vela (The Sails).

As they approach the ends of their lives many stars develop stable discs of gas and dust around them. This material was ejected by stellar winds, whilst the star was passing through the red giant stage of its evolution. These discs resemble those that form planets around young stars. But up to now astronomers have not been able to compare the two types, formed at the beginning and the end of the stellar life cycle.

Although there are many discs associated with young stars that are sufficiently near to us to be studied in depth, there are no corresponding old stars with discs that are close enough for us to obtain detailed images.

But this has now changed. A team of astronomers led by Michel Hillen and Hans Van Winckel from the Instituut voor Sterrenkunde in Leuven, Belgium, has used the full power of the Very Large Telescope Interferometer (VLTI) at ESO’s Paranal Observatory in Chile, armed with the PIONIER instrument, and the newly upgraded RAPID detector.

Their target was the old double star IRAS 08544-4431 [1], lying about 4000 light-years from Earth in the southern constellation of Vela (The Sails). This double star consists of a red giant star, which expelled the material in the surrounding dusty disc, and a less-evolved more normal star orbiting close to it.

Jacques Kluska, team member from Exeter University, United Kingdom, explains:

“By combining light from several telescopes of the Very Large Telescope Interferometer, we obtained an image of stunning sharpness — equivalent to what a telescope with a diameter of 150 metres would see. The resolution is so high that, for comparison, we could determine the size and shape of a one euro coin seen from a distance of two thousand kilometres.”

Thanks to the unprecedented sharpness of the images [2] from the Very Large Telescope Interferometer, and a new imaging technique that can remove the central stars from the image to reveal what lies around them, the team could dissect all the building blocks of the IRAS 08544-4431 system for the first time.

This video takes the viewer deep into a spectacular region of the southern Milky Way in the constellation of Vela (The Sails). We pass many interesting objects, including star formation regions and the blue filaments of a supernova remnant, before closing in on the faint star IRAS 08544-4431. This aging object is surrounded by a dusty disc that has been clearly resolved for the first time by the Very Large Telescope Interferometer at ESO’s Paranal Observatory in Chile. Credit: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org). Acknowledgement: Davide De Martin. Music: Johan B. Monell (www.johanmonell.com)

The most prominent feature of the image is the clearly resolved ring. The inner edge of the dust ring, seen for the first time in these observations, corresponds very well with the expected start of the dusty disc: closer to the stars, the dust would evaporate in the fierce radiation from the stars.

“We were also surprised to find a fainter glow that is probably coming from a small accretion disc around the companion star. We knew the star was double, but weren’t expecting to see the companion directly. It is really thanks to the jump in performance now provided by the new detector in PIONIER, that we are able to view the very inner regions of this distant system,”

adds lead author Michel Hillen.

The team finds that discs around old stars are indeed very similar to the planet-forming ones around young stars. Whether a second crop of planets can really form around these old stars is yet to be determined, but it is an intriguing possibility.

“Our observations and modelling open a new window to study the physics of these discs, as well as stellar evolution in double stars. For the first time the complex interactions between close binary systems and their dusty environments can now be resolved in space and time,”

concludes Hans Van Winckel.

This chart shows the location of the aging double star IRAS 08544-4431 in the constellation of Vela (The Sails). All stars visible to the naked eye on a dark and clear night are shown. This star is visible with a small telescope as an unremarkable single faint point of light.

Notes

[1] The name of the object indicates that it is a source of infrared radiation that was detected and catalogued by the IRAS satellite observatory in the 1980s.

[2] The resolution of the VLTI, used with the four Auxiliary Telescopes, was about one milliarcsecond (1/1000th of 1/3600th of a degree).

Astronomy, SETI

Video: Review of SETI projects and the $100M Breakthrough Listen Initiative

March 5, 2016 TopSpacer

In this SETI Institute seminar, Dr. Andrew Siemion, Director of the Berkeley SETI Research Center (BSRC) at the University of California, Berkeley, gives an excellent review of SETI projects past, present, and future and includes an

overview of the Breakthrough Listen Initiative, 100-million-dollar, 10-year search for extraterrestrial intelligence. Dr. Siemion will also discuss other SETI efforts ongoing at the BSRC, including the successful citizen science project SETI@Home, as well as a concerted effort to undertake panchromatic observations of the mysterious Kepler star KIC 8462852

Astronomy

ESO: “The Realm of Buried Giants” – crimson nebula lit by rare, massive stars

March 2, 2016 TopSpacer

Here is a new report from the European Southern Observatory (ESO):

The Realm of Buried Giants

In this huge new image clouds of crimson gas are illuminated by rare, massive stars that have only recently ignited and are still buried deep in thick dust clouds. These scorching-hot, very young stars are only fleeting characters on the cosmic stage and their origins remain mysterious. The vast nebula where these giants were born, along with its rich and fascinating surroundings, are captured here in fine detail by ESO’s VLT Survey Telescope (VST) at the Paranal Observatory in Chile.

In this huge image of part of the southern constellation of Norma (The Carpenter’s Square) wisps of crimson gas are illuminated by rare, massive stars that have only recently ignited and are still buried deep in thick dust clouds. These scorching-hot, very young stars are only fleeting characters on the cosmic stage and their origins remain mysterious. The vast nebula where these giants were born, known as RCW 106, is captured here in fine detail by ESO’s VLT Survey Telescope (VST), at the Paranal Observatory in Chile. The brightest part appears just above the centre of the image. Many other interesting objects are also captured in this wide-field image. For example the filaments to the right of the image are the remnants of an ancient supernova (SNR G332.4-00.4, also known as RCW 103), and the glowing red filaments at the lower left surround an unusual and very hot star (RCW 104, surrounding the Wolf–Rayet star WR 75). Patches of dark obscuring dust are also visible across the entire cosmic landscape.

RCW 106 is a sprawling cloud of gas and dust located about 12 000 light-years away in the southern constellation of Norma (The Carpenter’s Square). The region gets its name from being the 106th entry in a catalogue of H II regions in the southern Milky Way [1]. H II regions like RCW 106 are clouds of hydrogen gas that are being ionised by the intense starlight of scorching-hot, young stars, causing them to glow and display weird and wonderful shapes.

RCW 106 itself is the red cloud above centre in this new image, although much of this huge H II region is hidden by dust and it is much more extensive than the visible part. Many other unrelated objects are also visible in this wide-field VST image. For example, the filaments to the right of the image are the remnants of an ancient supernova, and the glowing red filaments at the lower left surround an unusual and very hot star [2]. Patches of dark obscuring dust are also visible across the entire cosmic landscape.

Astronomers have been studying RCW 106 for some time, although it is not the crimson clouds that draw their attention, but rather the mysterious origin of the massive and powerful stars buried within. Although they are very bright, these stars cannot be seen in visible-light images such as this one as the surrounding dust is too thick, but they make their presence clear in images of the region at longer wavelengths.

This video takes a close-up look at a huge image of part of the southern constellation of Norma (The Carpenter’s Square) where wisps of crimson gas are illuminated by rare, massive stars that have only recently ignited and are still buried deep in thick dust clouds. These scorching-hot, very young stars are only fleeting characters on the cosmic stage and their origins remain mysterious. The vast nebula where these giants were born, known as RCW 106, is captured here in fine detail by ESO’s VLT Survey Telescope (VST), at the Paranal Observatory in Chile.

The sequence starts with a view of RCW 104, filaments glowing in the intense radiation from a Wolf-Rayet star, passes over the supernova remnant RCW 103, and finally settles on RCW 106 itself.

For less massive stars like the Sun the process that brings them into existence is quite well understood — as clouds of gas are pulled together under gravity, density and temperature increase, and nuclear fusion begins — but for the most massive stars buried in regions like RCW 106 this explanation does not seem to be fully adequate. These stars — known to astronomers as O-type stars — may have masses many dozens of times the mass of the Sun and it is not clear how they manage to gather, and keep together, enough gas to form.

O-type stars likely form from the densest parts of the nebular clouds like RCW 106 and they are notoriously difficult to study. Apart from obscuration by dust, another challenge is the brevity of an O-type star’s life. They burn through their nuclear fuel in mere tens of millions of years, while the lightest stars have lifetimes that span many tens of billions of years. The difficulty of forming a star of this mass, and the shortness of their lifetimes, means that they are very rare — only one in every three million stars in our cosmic neighbourhood is an O-type star. None of those that do exist are close enough for detailed investigation and so the formation of these fleeting stellar giants remains mysterious, although their outsized influence is unmistakeable in glowing H II regions like this one.

eso1607d[1] — This chart shows the small and inconspicuous southern constellation of Norma (The Carpenter’s Square). Most of the stars visible to the naked eye on a clear dark night are shown. This region is in the plane of the Milky Way and hosts the huge star formation region RCW 106 (marked with a red circle), which is mostly hidden behind thick dust clouds and not visible in a small telescope. Credit: ESO/IAU and Sky & Telescope

Notes

[1] The catalogue was compiled in 1960 by three astronomers from the Mount Stromlo Observatory in Australia whose surnames were Rodgers, Campbell and Whiteoak, hence the prefix RCW.

[2] The supernova remnant is SNR G332.4-00.4, also known as RCW 103. It is about 2000 years old. The lower filaments are RCW 104, surrounding the Wolf–Rayet star WR 75. Although these objects bear RCW numbers, detailed later investigations revealed that neither of them were HII regions.