European Association for Astronomy Education

Source: Caltech

Hundreds of extrasolar planets have been found over the past decade and a half, most of them solitary worlds orbiting their parent star in seeming isolation. With further observation, however, one in three of these systems have been found to have two or more planets. Planets, it appears, come in bunches. Most of these systems contain planets that orbit too far from one another to feel each other’s gravity. In just a handful of cases, planets have been found near enough to one another to interact gravitationally.

Now, however, John A. Johnson, an assistant professor of astronomy at the California Institute of Technology (Caltech), and his colleagues have found two systems with pairs of gas giant planets locked in an orbital embrace.

In one system—a planetary pair orbiting the massive, dying star HD 200964, located roughly 223 light-years from Earth-the intimate dance is closer and tighter than any previously seen. “This new planet pair came in an unexpected package,” says Johnson.

Adds Eric Ford of the University of Florida in Gainsville, “A planetary system with such closely spaced giant planets would be destroyed quickly if the planets weren’t doing such a well synchronized dance. This makes it a real puzzle how the planets could have found their rhythm.”

A paper by Johnson, Ford, and their collaborators describing the planets and their intriguing orbital dynamics has been accepted for publication in the Astronomical Journal (see http://arxiv.org/abs/1007.4552 for a preprint).

All of the four newly discovered exoplanets are gas giants more massive than Jupiter, and like most exoplanets were discovered by measuring the wobble, or Doppler shift, in the light emitted by their parent stars as the planets orbit around them. Surprisingly, however, the members of each pair are located remarkably close to one another.

For example, the distance between the planets orbiting HD 200964 occasionally is just .35 astronomical units (AU)—roughly 33 million miles—comparable to the distance between Earth and Mars. The planets orbiting the second star, 24 Sextanis (located 244 light-years from Earth) are .75 AU, or about 70 million miles. By comparison, Jupiter and Saturn are never less than 330 million miles apart.

Because of their large masses and close proximity, the exoplanet pairs exert a large gravitational force on each other. The gravitational tug between HD 200964′s two planets, for example, is 3,000,000 times greater than the gravitational force between Earth and Mars, 700 times larger than that between the Earth and the moon, and 4 times larger than the pull of our sun on the Earth.

Unlike the gas giants in our own solar system, the new planets are located comparatively close to their stars. The planets orbiting 24 Sextanis have orbital periods of 455 days (1.25 years) and 910 days (2.5 years), and the companions to HD 200964 periods of 630 days (1.75 years) and 830 days (2.3 years). Jupiter, by contrast, takes just under 12 Earth years to make one pass around the sun.

Planets often move around after they form, in a process known as migration. Migration is thought to be commonplace—it even occurred to some extent within our own solar system—but it isn’t orderly. Planets located farther out in the protoplanetary disk can migrate faster than those closer in, “so planets will cross paths and jostle each other around,” Johnson says. “The only way they can ‘get along’ and become stable is if they enter an orbital resonance.”

When planets are locked in an orbital resonance, their orbital periods are related by the ratio of two small integers. In a 2:1 resonance, for example, an outer planet will orbit its parent star once for every two orbits of the inner planet; in a 3:2 resonance, the outer planet will orbit two times for every three passes by the inner planet, and so forth. Such resonances are created by the gravitational influence of planets on one another.

“There are many locations in a protoplanetary disk where planets can form,” says Johnson. “It’s very unlikely, however, that two planets would just happen to form at locations where they have periods in one of these ratios.”

A 2:1 resonance—which is the case for the planets orbiting 24 Sextanis—is the most stable and the most common pattern. “Planets tend to get stuck in the 2:1. It’s like a really big pothole,” Johnson says. “But if a planet is moving very fast”—racing in from the outer part of the protoplanetary disk, where it formed, toward its parent star—”it can pass over a 2:1. As it moves in closer, the next step is a 5:3, then a 3:2, and then a 4:3.”

Johnson and his colleagues have found that the pair of planets orbiting HD 200964 is locked in just such a 4:3 resonance. “The closest analogy in our solar system is Titan and Hyperion, two moons of Saturn which also follow orbits synchronized in a 4:3 pattern,” says Ford. “But the planets orbiting HD 200964 interact much more strongly, since each is around 20,000 times more massive than Titan and Hyperion combined.”

“This is the tightest system that’s ever been discovered,” Johnson adds, “and we’re at a loss to explain why this happened. This is the latest in a long line of strange discoveries about extrasolar planets, and it shows that exoplanets continuously have this ability to surprise us. Each time we think we can explain them, something else comes along.”

Johnson and his colleagues found the two systems using data from the Keck Subgiants Planet Survey—a search for planets around stars from 40 to 100 percent larger than our own sun. Subgiants represent a class of stars that have evolved off the “main sequence,” and have run out of hydrogen for nuclear fusion, causing their core to collapse and their outer envelope to swell. Subgiants eventually become red giants—voluminous stars with big, puffy atmospheres that pulsate, making it difficult to detect the subtle spectral shifts caused by orbiting planets.

“Subgiants are rotating very slowly and they’re cool,” unlike rapidly rotating, hot main sequence stars, “but they haven’t expanded enough to be too fluffy and too jittery,” Johnson says. “They’re ‘Goldilocks’ stars: not too fast, not too hot, not too fluffy, not too jittery”—and, therefore, ideal for planet hunting.

“Right now, we’re monitoring 450 of these massive stars, and we are finding swarms of planets,” he says. “Around these stars, we are seeing three to four times more planets out to a distance of about 3 AU—the distance of our asteroid belt—than we see around main sequence stars. Stellar mass has a huge influence on frequency of planet occurrence, because the amount of raw material available to build planets scales with the mass of the star.”

Eventually, perhaps 10 or 100 million years from now, subgiant stars like HD 200964 and 24 Sextanis will become red giants. They will throw off their outer atmospheres, swelling to the point where they could engulf the inner planet of their dancing pair, and will throw off mass, changing the gravitational dynamics of their whole system. “The planets will then move out, and their orbits will become unstable,” Johnson says. “Most likely one of the planets will get flung out of the system completely”-and the dance will end.

The paper, “A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextanis and HD 200964,” was coauthored by Matthew Payne and Eric B. Ford of the University of Florida; Andrew W. Howard and Geoffrey W. Marcy of the University of California, Berkeley; Kelsey Clubb of San Francisco State University; Brendan P. Bowler of the University of Hawai’i at Manoa,; Gregory W. Henry of Tennessee State University; Debra A. Fischer, John Brewer, and Christian Schwab of Yale University; Sabine Reffert of ZAH-Landessternwarte; and Thomas Lowe of the UCO/Lick Observatory.

Source: ESA PR 15-2010

ESA’s Planck mission has delivered its first all-sky image. It not only provides new insight into the way stars and galaxies form but also tells us how the  Universe itself came to life after the Big Bang.
“This is the moment that Planck was conceived for,” says ESA Director of Science and Robotic Exploration, David Southwood. “We’re not giving the answer. We are opening the door to an Eldorado where scientists can seek the nuggets that will lead to deeper understanding of how our Universe came to be and how it works now. The image itself and its remarkable quality is a tribute to the engineers who built and have operated Planck. Now the scientific harvest must
begin.”
From the closest portions of the Milky Way to the furthest reaches of space and time, the new all-sky Planck image is an extraordinary treasure chest of new data for astronomers.
The main disc of our Galaxy runs across the centre of the image. Immediately striking are the streamers of cold dust reaching above and below the Milky Way.
This galactic web is where new stars are being formed, and Planck has found many locations where individual stars are edging toward birth or just beginning their cycle of development.
Less spectacular but perhaps more intriguing is the mottled backdrop at the top and bottom. This is the ‘cosmic microwave background radiation’ (CMBR). It is the oldest light in the Universe, the remains of the fireball out of which our Universe sprang into existence 13.7 billion years ago.

While the Milky Way shows us what the local Universe looks like now, those the microwave pattern is the cosmic blueprint from which today’s clusters and superclusters of galaxies were built. The different colours represent minute
differences in the temperature and density of matter across the sky. Somehow these small irregularities evolved into denser regions that became the galaxies of today.
The CMBR covers the entire sky but most of it is hidden in this image by the Milky Way’s emission, which must be digitally removed from the final data in order to see the microwave background in its entirety.
When this work is completed, Planck will show us the most precise picture of the microwave background ever obtained. The big question will be whether the data will reveal the cosmic signature of the primordial period called inflation.
This era is postulated to have taken place just after the Big Bang and resulted in the Universe expanding enormously in size over an extremely short period.
Planck continues to map the Universe. By the end of its mission in 2012, it will have completed four all-sky scans. The first full data release of the CMBR is planned for 2012. Before then, the catalogue containing individual objects in our
Galaxy and whole distant galaxies will be released in January 2011.
“This image is just a glimpse of what Planck will ultimately see,” says Jan Tauber, ESA’s Planck Project Scientist.(read more)

Source: Brown University

A research team led by Brown University has documented dozens of channels carved by melted water from glaciers located in the midlatitude region of Mars. The glaciofluvial valleys were carved in Mars’ most recent epoch, the team reports, supporting the idea that the Red Planet was home to diverse watery environments in its recent past. Results are published in Icarus. (read more)

Source: Royal Astronomical Society

Many of the Milky Way’s ancient stars are remnants of other smaller galaxies torn apart by violent galactic collisions around five billion years ago, according to researchers at Durham University, who publish their results in a new paper in the journal Monthly Notices of the Royal Astronomical Society. (read more)

Source: ESA

The SCIAMACHY sensor on ESA’s Envisat satellite has provided scientists with invaluable data on our planet, allowing them to map global air pollution and the distribution of greenhouse gases. (read more)

Credit: ESA/HST

A spectacular new NASA/ESA Hubble Space Telescope image — one of the largest ever released of a star-forming region — highlights N11, part of a complex network of gas clouds and star clusters within our neighbouring galaxy, the Large Magellanic Cloud. This region of energetic star formation is one of the most active in the nearby Universe.(read more)

Source: PHYSORG

A team of scientists from the Instituto Astrofísica de Canarias (IAC) and the University of Texas has succeeded in identifying one of the most complex organic molecules yet found in the material between the stars, the so-called interstellar medium. The discovery of anthracene could help resolve a decades-old astrophysical mystery concerning the production of organic molecules in space. The researchers report their findings in the journal Monthly Notices of the Royal Astronomical Society.(read more)

Source: ESA

ESA’s comet-chaser Rosetta is heading for a blind date with asteroid Lutetia. Rosetta does not yet know what Lutetia looks like but beautiful or otherwise the two will meet on 10 July. (read more)

Source: University of Colorado at Boulder

A vast ocean likely covered one-third of the surface of Mars some 3.5 billion years ago, according to a new study conducted by University of Colorado at Boulder scientists.

The CU-Boulder study is the first to combine the analysis of water-related features including scores of delta deposits and thousands of river valleys to test for the occurrence of an ocean sustained by a global hydrosphere on early Mars. While the notion of a large, ancient ocean on Mars has been repeatedly proposed and challenged over the past two decades, the new study provides further support for the idea of a sustained sea on the Red Planet during the Noachian era more than 3 billion years ago, said CU-Boulder researcher Gaetano Di Achille, lead author on the study.

A paper on the subject authored by Di Achille and CU-Boulder Assistant Professor Brian Hynek of the geological sciences department appears in the June 13 issue of Nature Geoscience. Both Di Achille and Hynek are affiliated with CU-Boulder’s Laboratory for Atmospheric and Space Physics.

More than half of the 52 river delta deposits identified by the CU researchers in the new study — each of which was fed by numerous river valleys — likely marked the boundaries of the proposed ocean, since all were at about the same elevation. The research team says twenty-nine of the 52 deltas were connected either to the ancient Mars ocean or to the groundwater table of the ocean and to several large, adjacent lakes. (read more)

Source: ESA

As the ISS circles Earth, it has begun tracking individual ships crossing the seas beneath. An experiment hosted by ESA’s Columbus module is testing the viability of monitoring global traffic from the Station’s orbit hundreds of kilometres up.(read more)

Source: AFP

Scientists in Australia’s vast Outback on Monday recovered a capsule of the Hyabusa mission that they hope contains the first piece of asteroid ever brought to Earth — perhaps offering a glimpse into ancient space history.

The pod was ejected from a Japanese space probe as the host vessel burned up in a spectacular display over Australia following a seven-year odyssey across the solar system to the far-off Itokawa asteroid.

It lay in the desert dust overnight before scientists were given the go-ahead to retrieve it after Aboriginal elders said it had not landed in any indigenous sacred sites. (read more)

Source: NASA /JPL

This test of the radar system to be used during the August 2012 descent and landing of the NASA Mars rover Curiosity mounted an engineering test model of the radar system onto the nose of a helicopter. Image Credit: NASA

Engineers with NASA’s Jet Propulsion Laboratory, Pasadena, Calif., are running diverse trials with a test version of the radar system that will enable NASA’s Mars Science Laboratory mission to put the Curiosity rover onto the Martian surface in August 2012.

One set of tests conducted over a desert lakebed at NASA’s Dryden Flight Research Center, Edwards, Calif., in May 2010 used flights with a helicopter simulating specific descent paths anticipated for Martian sites.

During the final stage of descent, NASA’s Mars Science Laboratory mission will use a “sky crane” maneuver to lower Curiosity on a bridle from the mission’s rocket-powered descent stage. The descent stage will carry Curiosity’s flight radar.

The testing at Dryden included lowering a rover mockup on a tether from the helicopter to assess how the sky crane maneuver will affect the radar’s descent-speed determinations by the radar. The helicopter carried the test radar on a special nose-mounted gimbal.

Helicopter-flown testing has also been conducted at other desert locations for experience in an assortment of terrains. Later in 2010, the team plans to test the higher-altitude, higher-velocity part of Curiosity’s radar-aided descent by flying the test radar on dives by an F/A-18 jet from Dryden.

Source: ESO

Astronomers often turn their telescopes to the Large Magellanic Cloud (LMC), one of the closest galaxies to our own Milky Way, in their quest to understand the Universe. In this spectacular new image from the Wide Field Imager (WFI) at ESO’s La Silla Observatory in Chile, a celestial menagerie of different objects and phenomena in part of the LMC is on display, ranging from vast globular clusters to the remains left by brilliant supernovae explosions. This fascinating observation provides data for a wide variety of research projects unravelling the life and death of stars and the evolution of galaxies. (read more)

Source: ESA

ESA has now opened the possibility of people to try to suggest a name for next mission to the ISS. An oportunity not to loose.

ESA’s promotion slogan is “ESA’s Italian astronaut Paolo Nespoli will soon visit the International Space Station, and he needs your help to name his mission.” (read more)

Source: ESA

ESA and its partners are launching a new kind of fitness initiative using the example of space explorers to promote exercise and healthy nutrition to young people worldwide. ‘Mission X: Train Like an Astronaut’ is boarding now in eight countries. (read more)

Source: DLR

The German-American Stratospheric Observatory for Infrared Astronomy, SOFIA, completed an important milestone by achieving ‘first light’ when it performed its first observations during the night between 25 and 26 May 2010. SOFIA is the only airborne observatory in the world, operated jointly by NASA and the German Aerospace Center (Deutsches Zentrum fur Luft- und Raumfahrt; DLR). The observatory carried out observations of astronomical objects at infrared wavelengths in flight. (read more)

Source: Chandra

A detailed study of Chandra observations over ten years shows that M31* was in a very dim, or quiet, state from 1999 to the beginning of 2006. However, on January 6, 2006, the black hole became more than a hundred times brighter, suggesting an outburst of X-rays. This was the first time such an event had been seen from a supermassive black hole in the nearby, local universe. After the outburst, M31* entered another relatively dim state, but was almost ten times brighter on average than before 2006. The outburst suggests a relatively high rate of matter falling onto M31* followed by a smaller, but still significant rate. (read more)

Source: ESA – oshi

Thousands of galaxies crowd into this Herschel image of the distant Universe. Each dot is an entire galaxy containing billions of stars.

For more than a decade, astronomers have puzzled over strangely bright galaxies in the distant Universe. These ‘luminous infrared galaxies’ appear to be creating stars at such phenomenal rates that they defy conventional theories of galaxy formation.

Now ESA’s Herschel infrared space observatory, with its ability for very sensitive mapping over wide areas, has seen thousands of these galaxies and pinpointed their locations, showing for the first time that they are packing themselves closely together, forming large clusters of galaxies by the force of their mutual gravity. (read more)

Source: NASA/SWIFT

Data from an ongoing survey by NASA’s Swift satellite have helped astronomers solve a decades-long mystery about why a small percentage of black holes emit vast amounts of energy.

Only about one percent of supermassive black holes exhibit this behavior. The new findings confirm that black holes “light up” when galaxies collide, and the data may offer insight into the future behavior of the black hole in our own Milky Way galaxy. The study will appear in the June 20 issue of The Astrophysical Journal Letters.

The intense emission from galaxy centers, or nuclei, arises near a supermassive black hole containing between a million and a billion times the sun’s mass. Giving off as much as 10 billion times the sun’s energy, some of these active galactic nuclei (AGN) are the most luminous objects in the universe. They include quasars and blazars. (read more)

Source: ESA – oshi

This glowing core is the stellar equivalent of an insect’s cocoon. Nestled in the bright centre are two newly forming stars. When they reach maturity they will begin to generate their own energy and shine out across the Universe.

Small, isolated clouds of forming stars are known as Bok Globules after the 20th century astronomer Bart Bok. Back in the 1940s, their identification was an important step towards the realisation that stars form from the condensation of gas clouds in space.

It was not until the Infrared Astronomical Satellite was launched in the 1980s, and the era of space-based infrared astronomy began, that the idea of Bok Globules as stellar cocoons was confirmed by João Yun and co-authors. (read more)