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From an ESA press release, September 14, 2016 :

The first catalogue of more than a billion stars from ESA’s Gaia satellite was published on September 14, 2016 – the largest all-sky survey of celestial objects to date.

On its way to assembling the most detailed 3D map ever made of our Milky Way galaxy, Gaia has pinned down the precise position on the sky and the brightness of 1.142 billion stars. As a taster of the richer catalogue to come in the near future, this data release also features the distances and the motions across the sky for more than two million stars.

gaia_s_first_sky_map_node_full_image_2

Credit: ESA/Gaia/DPAC

The map projection above shows an all-sky view of stars in the Milky Way and our neighboring galaxies, based on the first year or so of Gaia’s observations. It shows the density of stars observed by Gaia in each portion of the sky. Brighter regions indicate denser concentrations of stars, while darker regions correspond to patches of the sky where fewer stars are observed. Darker regions across the Galactic Plane correspond to dense clouds of interstellar gas and dust that absorb starlight along the line of sight. Many globular and open clusters – groupings of stars held together by their mutual gravity – are also sprinkled across the image.

Note that the faint curved features and dark stripes are not of astronomical origin but rather reflect Gaia’s scanning procedure. As this map is based on observations performed during the mission’s first year, the survey is not yet uniform across the sky. These artefacts will gradually disappear as more data are gathered during the five-year mission.

Links: ESA press release, Gaia sky map.

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From a press release of the European Space Agency (ESA), September 5, 2016:

Less than a month before the end of the mission, the Rosetta orbiter’s high-resolution camera has revealed the Philae lander wedged into a dark crack on Comet 67P/Churyumov-Gerasimenko.

philae_found

Credit: ESA/Rosetta/MPS for OSIRIS Team

The images were taken on September 2 by the OSIRIS narrow-angle camera as the orbiter came within 2.7 km of the surface and show the main body of the lander, along with two of its three legs.

The images also provide proof of Philae’s orientation, making it clear why establishing communications was so difficult following its landing on November 12, 2014.

The discovery comes less than a month before Rosetta descends to the comet’s surface. On September 30, the orbiter will be sent on a final one-way mission to investigate the comet from close up, including the open pits in the Ma’at region, where it is hoped that critical observations will help to reveal secrets of the body’s interior structure.

Link: full Rosetta mission press release, including further images and explanations.

From a press release of the European Space Agency:

Over the past week, ESA’s Integral satellite has been observing an exceptional outburst of high-energy light produced by a black hole that is devouring material from its stellar companion.

Black_hole_with_stellar_companion_node_full_image_2

Credit and copyright: ESA/ATG medialab

X-rays and gamma rays point to some of the most extreme phenomena in the Universe, such as stellar explosions, powerful outbursts and black holes feasting on their surroundings. In contrast to the peaceful view of the night sky we see with our eyes, the high-energy sky is a dynamic light show, from flickering sources that change their brightness dramatically in a few minutes to others that vary on timescales spanning years or even decades.

On 15 June 2015, a long-time acquaintance of X-ray and gamma ray astronomers made its comeback to the cosmic stage: V404 Cygni, a system comprising a black hole and a star orbiting one another. It is located in our Milky Way galaxy, almost 8000 light-years away in the constellation Cygnus, the Swan. In this type of binary system, material flows from the star towards the black hole and gathers in a disc, where it is heated up, shining brightly at optical, ultraviolet and X-ray wavelengths before spiralling into the black hole.

The V404 Cygni black hole system has not been this bright and active since 1989, when it was observed with the Japanese X-ray satellite Ginga and high-energy instruments on board the Mir space station.

Link: the full ESA press release.

The European Space Agency’s ExoMars mission is set for launch in 2018.  A rover and a lander are included, to search for evidence of past and present life on Mars. The orbiter, part of the ExoMars 2016 mission, will sample the Martian atmospheric trace gases, such as methane and provide communications. The rover will leave the landing platform and drill into the surface to search for potential fossils, relevant minerals, and organic molecules (with chirality as biomarkers).

ExoMars_combi_350

Credit: ESA

In addition to its scientific exploration, the mission will help test in-situ technologies that might pave the way for a future international Mars sample return mission.

Links: ExoMars 2018 mission overview; ESA Mars homepage.

Adapted from a European Space Agency press release, September 26, 2014:

ESA’s Rosetta mission will deploy its lander, Philae, to the surface of Comet 67P/Churyumov–Gerasimenko on November 12, 2014. Philae’s landing site, currently known as Site J, is located on the smaller of the comet’s two ‘lobes’, with a backup site on the larger lobe. The sites were selected just six weeks after Rosetta arrived at the comet on August 6, following its 10-year journey through the Solar System.

Philae’s primary landing site

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The main focus to date has been to survey 67P/Churyumov–Gerasimenko in order to prepare for the first ever attempt to soft-land on a comet. Site J was chosen unanimously over four other candidate sites as the primary landing site because the majority of terrain within a square kilometre area has slopes of less than 30° relative to the local vertical and because there are relatively few large boulders. The area also receives sufficient daily illumination to recharge Philae and continue surface science operations beyond the initial 64-hour battery-powered phase.

Final confirmation of the primary landing site and its landing scenario will be made on October 14 after a formal review, which will include the results of additional high-resolution analysis of the landing site and its back-up conducted in the meantime. Should the backup site be chosen at this stage, the landing attempt can still take place on November 12.

Links: the ESA press release, including links to further resources on Rosetta and Philae and this short movie showing Philae’s planned descent.

Adapted from an ESA press release, August 6, 2014:
After a decade-long journey chasing its target, ESA’s Rosetta has today become the first spacecraft to rendezvous with a comet, opening a new chapter in Solar System exploration. Comet 67P/Churyumov–Gerasimenko and Rosetta now lie 405 million kilometers from Earth, about half way between the orbits of Jupiter and Mars, rushing towards the inner Solar System at nearly 55,000 kilometers per hour.

Comet 67P/Churyumov-Gerasimenko on August 3, 2014

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The comet is in an elliptical 6.5-year orbit that takes it from beyond Jupiter at its furthest point, to between the orbits of Mars and Earth at its closest to the Sun. Rosetta will accompany it for over a year as they swing around the Sun and back out towards Jupiter again.
The journey to the comet was not straightforward, however. Since its launch in 2004, Rosetta had to make three gravity-assist flybys of Earth and one of Mars to help it on course to its rendezvous with the comet. It has traveled for ten years, five months and four days, clocking up 6.4 billion kilometers. Its complex course also allowed Rosetta to pass by asteroids Šteins and Lutetia, obtaining unprecedented views and scientific data on these two objects.

August 6 saw the last of a series of ten rendezvous manoeuvres that began in May to adjust Rosetta’s speed and trajectory gradually to match those of the comet. If any of these manoeuvres had failed, the mission would have been lost, and the spacecraft would simply have flown by the comet.

Links: the ESA press release, including further images; Rosetta fact-sheet.

From a press release of the Max Planck Institute for Solar System Research, July 17, 2014:
As ESA’s spacecraft Rosetta is slowly approaching its destination, Comet 67P/Churyumov-Gerasimenko (see p. 213) is again proving to be full of surprises. New images obtained by OSIRIS, the onboard scientific imaging system, confirm the body’s peculiar shape that earlier pictures had hinted at. 67P is obviously quite unlike any other comet visited so far. (See also previous post.)

“The distance still separating Rosetta from 67P is now far from astronomical,” says OSIRIS principal investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany. “It’s a trip of less than 12,000 kilometers. That’s comparable to travelling from Germany to Hawaii.”

However, while taking a snapshot of Mauna Kea, Hawaii’s highest mountain, from Germany is an impossible feat, Rosetta’s camera OSIRIS is doing a great job at catching ever clearer glimpses of its similarly sized destination. Images obtained on July 14th clearly show a tantalizing shape. The comet’s nucleus consists of two distinctly separated parts.

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

“This is unlike any other comet we have ever seen before,” says OSIRIS project manager Carsten Güttler from the MPS. “The images faintly remind me of a rubber ducky with a body and a head,” he adds with a laugh. How 67P received this duck-like shape is still unclear. “At this point we know too little about 67P to allow for more than an educated guess,” says Sierks. In the next months, the scientists hope to determine more of the comet’s physical and mineralogical properties. These could help decide, whether the comet’s body and head were formerly two individual bodies.

In order to get an idea of what seems to be a very unique body, the observed image data can be interpolated to create a smoother shape. “There is, of course, still uncertainty in these processed, filtered images and the surface will not be as smooth as it now appears,” Güttler points out. “But they help us the get a first idea.”

Links: the original MPS press release and media files; an interactive movie (requires a Flash player) depicting Rosetta’s journey through the Solar System to reach Comet 67/P C-G.

Adapted from an ESA press release, July 17, 2014:
New images of Comet 67P/Churyumov-Gerasimenko reveal an extraordinarily irregular shape (see p. 213). It has become clear that this is no ordinary comet. Like its name, it seems that comet 67P/C-G is in two parts.

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

ESA scientists have made this movie, using a sequence of 36 interpolated images each separated by 20 minutes, providing a truly stunning 360-degree preview of the overall complex shape of the comet. It supports the presence of two definite components – one segment seems to be rather elongated, while the other appears more bulbous. Indeed, some people have already likened the shape to a duck, with a distinct body and head. Note that the comet’s surface features won’t be as smooth as these processed images imply.

Dual objects like this – known as ‘contact binaries’ in comet and asteroid terminology – are not uncommon. Indeed, Comet 8P/Tuttle is thought to be such a contact binary; radio imaging by the ground-based Arecibo telescope in Puerto Rico in 2008 suggested that it comprises two sphere-like objects. Meanwhile, the bone-shaped Comet 103P/Hartley 2, imaged during NASA’s EPOXI flyby in 2011, revealed a comet with two distinct halves separated by a smooth region. In addition, observations of asteroid 25143 Itokawa by JAXA’s Hayabusa mission, combined with ground-based data, suggest an asteroid comprising two sections of highly contrasting densities.

Is Rosetta en-route to rendezvous with a similar breed of comet? The scientific rewards of studying such a comet would be high, as a number of possibilities exist as to how they form.

Links and further resources: the full ESA press release; link to unprocessed (still) image; link to movie.

From a European Space Agency (ESA) press release, May 16. 2014:

After eight years in orbit, ESA’s Venus Express orbiting mission has completed routine science observations and is preparing for a daring plunge into the planet’s hostile atmosphere. Its suite of seven instruments have provided a comprehensive study of the ionosphere, atmosphere and surface of Venus.

Credit: ESA, C. Carreau

Credit: ESA, C. Carreau

The spacecraft’s fuel supplies, necessary to maintain its elliptical orbit, are running low and will soon be exhausted. The routine science operations concluded this week and the spacecraft is being prepared for one final mission: to make a controlled plunge deeper into the atmosphere than ever before attempted.

This experimental ‘aerobraking’ phase is planned for June 18 – July 11, during which time some limited science measurements with the spacecraft’s magnetic field, solar wind and atom analyzing instruments will be possible. Also, temperature and pressure sensors will record the conditions that the spacecraft experiences.

It is possible that the remaining fuel in Venus Express will be exhausted during this phase or that the spacecraft does not survive these risky operations. But if the spacecraft is still healthy afterwards, its orbit will be raised again and limited operations will continue for several more months, fuel permitting. However, by the end of the year, it is likely that Venus Express will have made its final descent into the atmosphere of the planet, bringing a fantastic scientific endeavor to an end.

Links: ESA press release; link to aerobraking movie (approx 1 min 30 s).

 

 

A space-based observatory to search for planets orbiting alien stars has been selected as ESA’s third medium-class science mission. It is planned for launch by 2024.

The PLATO – PLAnetary Transits and Oscillations of stars – mission was selected by ESA’s Science Program Committee for implementation as part of its Cosmic Vision 2015-25 Program. The mission will address two key themes: what are the conditions for planet formation and the emergence of life, and how does the Solar System work? (See Chapter 9, p. 233.)

Credit: ESA (Thales/EADS Astrium)

PLATO will monitor relatively nearby stars, searching for tiny, regular dips in brightness as their planets transit in front of them, temporarily blocking out a small fraction of the starlight. By using 34 separate small telescopes and cameras, PLATO will search for planets around up to a million stars spread over half of the sky. It will also investigate seismic activity in the stars, enabling a precise characterization of the host sun of each planet discovered, including its mass, radius and age.

When coupled with ground-based radial velocity observations, PLATO’s measurements will allow a planet’s mass and radius to be calculated, and therefore its density, providing an indication of its composition.

The mission will identify and study thousands of exoplanetary systems, with an emphasis on discovering and characterizing Earth-size planets and super-Earths in the habitable zone of their parent stars – the distance from the star where liquid water could exist on the surface.

Data from ESA’s recently launched Gaia mission will help PLATO to provide precise characteristics of thousands of exoplanet systems. These systems will provide natural targets for detailed follow-up observations by future large ground- and space-based observatories.

Links: ESA press release.