An earlier posting here described the “Grande Finale” of the Cassini spacecraft mission to Saturn. Here is a panel news conference held last week in which the panelists talked about the final activities of the spacecraft starting with a
final close flyby of Saturn’s moon Titan on April 22 [which] will reshape the Cassini spacecraft’s orbit so that it begins its final series of 22 weekly dives through the unexplored gap between the planet and its rings. The first of these dives is planned for April 26. Following these closer-than-ever encounters with the giant planet, Cassini will make a mission-ending plunge into Saturn’s upper atmosphere on Sept. 15.
Astronomers have detected an atmosphere around the super-Earth GJ 1132b. This marks the first detection of an atmosphere around a low-mass Super-Earth, in terms of radius and mass the most Earth-like planet around which an atmosphere has yet been detected. Thus, this is a significant step on the path towards the detection of life on an exoplanet. The team, which includes researchers from the Max Planck Institute for Astronomy, used the 2.2 m ESO/MPG telescope in Chile to take images of the planet’s host star GJ 1132, and measuring the slight decrease in brightness as the planet and its atmosphere absorbed some of the starlight while passing directly in front of their host star.
While it’s not the detection of life on another planet, it’s an important step in the right direction: the detection of an atmosphere around the super-Earth GJ 1132b marks the first time an atmosphere has been detected around a planet with a mass and radius close to that of Earth (1.6 Earth masses, and 1.4 Earth radii).
Astronomers’ current strategy for finding life on another planet is to detect the chemical composition of that planet’s atmosphere, on the look-out for certain chemical imbalances that require the presence of living organisms as an explanation. In the case of our own Earth, the presence of large amounts of oxygen is such a trace.
We’re still a long way from that detection though. Until the work described in this article, the (few!) observations of light from exoplanet atmospheres all involved planets much more massive than Earth: gas giants – relatives of our own Solar System’s Jupiter – and a large super-Earth with more than eight times the Earth’s mass. With the present observation, we’ve taken the first tentative steps into analyzing the atmosphere of smaller, lower-mass planets that are much more Earth-like in size and mass.
The planet in question, GJ 1132b, orbits the red dwarf star GJ 1132 in the Southern constellation Vela, at a distance of 39 light-years from us. Recently, the system has come under scrutiny by a team led by John Southworth (Keele University, UK). The project was conceived, and the observations coordinated, by Luigi Mancini, formerly of the Max Planck Institute for Astronomy (MPIA) and now working at the University of Rome Tor Vergata. Additional MPIA team members were Paul Mollière, and Thomas Henning.
The team used the GROND imager at the 2.2 m ESO/MPG telescope of the European Southern Observatory in Chile to observe the planet simultaneously in seven different wavelength bands. GJ 1132b is a transiting planet: From the perspective of an observer on Earth, it passes directly in front of its star every 1.6 days, blocking some of the star’s light.
The size of stars like GJ 1132 is well known from stellar models. From the fraction of starlight blocked by the planet, astronomers can deduce the planet’s size – in this case around 1.4 times the size of the Earth. Crucially, the new observations showed the planet to be larger one of the infrared wavelengths than at the others. This suggests the presence of an atmosphere that is opaque to this specific infrared light (making the planet appear larger), but transparent at all the others. Different possible versions of the atmosphere were then simulated by team members at the University of Cambridge and the Max Planck Institute for Astronomy. According to those models, an atmosphere rich in water and methane would explain the observations very well.
The discovery comes with the usual exoplanet caveats: while somewhat larger than Earth, and with 1.6 times Earth’s mass (as determined by earlier measurements), observations to date do not provide sufficient data to decide how similar or dissimilar GJ 1132b is to Earth. Possibilities include a “water world” with an atmosphere of hot steam.
The presence of the atmosphere is a reason for cautious optimism. M dwarfs are the most common types of star, and show high levels of activity; for some set-ups, this activity (in the shape of flares and particle streams) can be expected to blow away nearby planets’ atmospheres. GJ 1132b provides a hopeful counterexample of an atmosphere that has endured for billion of years (that is, long enough for us to detect it). Given the great number of M dwarf stars, such atmospheres could mean that the preconditions for life are quite common in the universe.
In any case, the new observations make GJ 1132b a high-priority target for further study by instruments such as the Hubble Space Telescope, ESO’s Very Large Telescope, and the James Webb Space Telescope slated for launch in 2018.
The team members are John Southworth (Keele University), Luigi Mancini (Max Planck Institute for Astronomy [MPIA], Universita die Roma Tor Vergata, INAF – Osservatorio Astrofisico di Torinio), Nikku Madhusudhan (University of Cambridge), Paul Mollière (MPIA), Simona Ciceri (Stockholm University), and Thomas Henning (MPIA).
The work described here has been published as J. Southworth et al., “Detection of the atmosphere of the 1.6 Earth mass exoplanet GJ 1132B” in the Astronomical Journal.
Stellar explosions are most often associated with supernovae, the spectacular deaths of stars. But new ALMA observations provide insights into explosions at the other end of the stellar life cycle, star birth. Astronomers captured these dramatic images as they explored the firework-like debris from the birth of a group of massive stars, demonstrating that star formation can be a violent and explosive process too.
1350 light years away, in the constellation of Orion (the Hunter), lies a dense and active star formation factory called the Orion Molecular Cloud 1 (OMC-1), part of the same complex as the famous Orion Nebula. Stars are born when a cloud of gas hundreds of times more massive than our Sun begins to collapse under its own gravity. In the densest regions, protostars ignite and begin to drift about randomly. Over time, some stars begin to fall toward a common centre of gravity, which is usually dominated by a particularly large protostar — and if the stars have a close encounter before they can escape their stellar nursery, violent interactions can occur.
Stellar explosions are most often associated with supernovae, the spectacular deaths of stars. But new ALMA observations of the Orion Nebula complex provide insights into explosions at the other end of the stellar life cycle, star birth. This ESOcast Light takes a quick look at the important facts.
About 100 000 years ago, several protostars started to form deep within the OMC-1. Gravity began to pull them together with ever-increasing speed, until 500 years ago two of them finally clashed. Astronomers are not sure whether they merely grazed each other or collided head-on, but either way it triggered a powerful eruption that launched other nearby protostars and hundreds of colossal streamers of gas and dust out into interstellar space at over 150 kilometres per second. This cataclysmic interaction released as much energy as our Sun emits in 10 million years.
Fast forward 500 years, and a team of astronomers led by John Bally (University of Colorado, USA) has used the Atacama Large Millimeter/submillimeter Array (ALMA) to peer into the heart of this cloud. There they found the flung-out debris from the explosive birth of this clump of massive stars, looking like a cosmic version of fireworks with giant streamers rocketing off in all directions.
This video takes the viewer deep into the famous constellation of Orion (The Hunter). Hidden behind the glowing gas, dark dust and bright young stars of the Orion Nebula complex lies a strange object — the remains of a 500 year old interaction of recently formed stars. A new image from ALMA, which reveals this feature more clearly than ever before, is shown at the end of the sequence. Credit: ALMA (ESO/NAOJ/NRAO), J. Bally/H. Drass et al./N. Risinger (skysurvey.org). Music: Johan B. Monell
Such explosions are expected to be relatively short-lived, the remnants like those seen by ALMA lasting only centuries. But although they are fleeting, such protostellar explosions may be relatively common. By destroying their parent cloud, these events might also help to regulate the pace of star formation in such giant molecular clouds.
Hints of the explosive nature of the debris in OMC-1 were first revealed by the Submillimeter Array in Hawaii in 2009. Bally and his team also observed this object in the near-infrared with the Gemini South telescope in Chile, revealing the remarkable structure of the streamers, which extend nearly a light-year from end to end.
The new ALMA images, however, showcase the explosive nature in high resolution, unveiling important details about the distribution and high-velocity motion of the carbon monoxide (CO) gas inside the streamers. This will help astronomers understand the underlying force of the blast, and what impact such events could have on star formation across the galaxy.
This video sequence compares a new ALMA image of an explosive event in the Orion star forming region with an image taken in infrared light using the HAWK-I camera on ESO’s Very Large Telescope. Credit: ALMA (ESO/NAOJ/NRAO)/J. Bally/H. Drass et al. Music: Johan B. Monell