Orcus Patera, a mysterious crater on Mars

This image of Orcus Patera was acquired by ESA's Mars Express orbiter; see press release. Orcus is an elliptical depression near Mars's equator, near the well-known volcanoes of Elysium Mons and Olympus Mons. Its origin is unknown, possibly a volvanic feature, or perhaps a circular impact crater that was later deformed by tectonic forces.

HD 10180, a five-exoplanet system

Astronomers used the HARPS radial-velocity instrument (at the European Southern Observatory) to detect five exoplanets orbiting the star HD 10180. Two additional planets are also suspected, but their existence is uncertain due to their weak signal. These five make this exo-planetary system one of the most abundant discovered to date. The five planets are Neptune-class, and they all reside at distances interior to Mar's orbit about the Sun. The above graphic is an artist's rendition of this system. A press release is also available.

Rosetta spacecraft flies by asteroid Lutetia

The Rosetta spacecraft aquired several images of asteroid Lutetia. Rosetta is headed towards comet Churyumov-Gerasimenko, and will go into orbit about that comet in 2014. But this spacecraft also made a close pass at asteroid Lutetia while en route. Additional images are also posted at the European Space Agency's website. Lutetia might be a C type asteroid, ie a carbonaceous chondrite, which is a fairly common rocky asteroid that is also rich in organic molecules. Or else it is an M type asteroid, which is rich in metallic nickel-iron. M-types must have once resided deep inside the core of a much larger asteroid that likely fragmented early in the Solar System's history. These observations by Rosetta should resolve this asteroid's composition, and may provide clues about its origin.

Daphnis maintains the Keeler Gap

The small Saturnian satellite Daphnis is responsble for maintaining the narrow Keeler gap, which lies near the outer edge of Saturn's main A ring. Daphnis' gravitational pull on the nearer ring particles also sculpts the gap's edges, resulting in wakes that are downstream of the satellite. This Cassini image is available at the CICLOPS website.

Mass transfer in circumstellar disks

The left graphic is a near-infrared image of the heirachical star system SR24. The lower object is the star SR24S, and the nebulosity surrounding it is a protoplanetary disk that is composed mostly of hydrogen gas plus some dust. The stellar contribution to this image has been subtracted, which is why the disk appear dark in its center. The upper object SR24N is actually an unresolved binary star; that binary also has its own circumbinary disk such that the SR24N stellar pair + disk orbits the SR24S star + disk. The right graphic is a computer simulation of this system, which reveals that these two disks can transfer mass between each other through a `bridge' that passes through this system's L1 Lagrange point, which is one of three sites in this system where gravity + Coriolis forces balance to zero. Observations such as this will hopefully reveal whether binary stars might one day form planets, or if their disks are too disturbed to produce planets. This image was acquire by Satoshi Mayami at the Subaru Telescope. A preprint on this work is also available.

A big expoplanet in a wide orbit

The circled dots indicate the 8 Jupiter mass planet that was discovered by David Lafrenière and colleagues as it orbits the star 1RXS J160929.1-210524. A preprint is also available. These infrared images of the system are acquired at wavelengths of 3 (left) and 4 (right) microns. This giant exoplanet orbits about 300 AU away from the primary star (cross), which is quite remarkable, because current models of planet formation generally do not produce such large planets orbiting at such great distances from the star. However, binary stars do exist at these separations, so one might wonder whether these objects really are large exoplanets, or are perhaps rather small stars.

Giant exoplanet confirmed orbiting in debris disk

Beta Pictoris b is a giant extrasolar planet, having a mass of about 10 Jupiter masses. It was first detected by direct imaging in 2003, but not seen again in followup images acquired in 2008, so the suspicion then was that this faint dot was just a background star, and not a planet that is actually bound to the star. However that expolanet was later recovered again in images acquired in late 2009 by Anne-Marie Lagrange; those images show that the dot seen above is indeed bound to Beta Pictoris, and orbits at a distance of about 10 AU from the star. So it seems that beta Pic b wasn't seen in 2008 because it was passing in front of or behind the very much brighter star.

Beta Pictoris is also known for its huge circumstellar debris disk; that disk is seen edge-on by astronomers at Earth, and the above graphic---which by the way is not a real telescopic image, but is probably the merger of two separate images---shows that the planet's orbit is coplanar with the debris disk. This in fact is to be expected, because such debris disks are composed of dust grains that are produced by collisions among unseen planetesimals, which are also the seeds from which planets form from. See this press release from the European Southern Observatory for more details.