Space Sunday: exoplanets, dark matter, rovers and recoveries

On August 15th, I wrote about rumours that an “Earth-like” planet has been found orbiting our nearest stellar neighbour, Proxima Centauri, 4.25 light years away from our own Sun. The news was first leaked by the German weekly magazine, Der Spiegel, which indicated the discovery had been made by a team at the European Southern Observatory’s (ESO)  La Silla facility – although ESO refused to comment at the time.

However, during a press conference held on August 24th, ESO did confirm the detection of a rocky planet orbiting Proxima Centauri. Dubbed Proxima b, the planet lies within the so-called “Goldilocks” habitable zone around its parent star – the orbit in which conditions are “just right” for the planet to harbour liquid water and offer the kind of conditions in which life might arise.

The ESO data reveals that Proxima b is orbits its parent star at a distance of roughly 7.5 million km (4.7 million miles), at the edge of the habitable zone, and does so every 11.2 terrestrial days and is about 1.3 times as massive as the Earth. The discovery came about by comparing multiple observations of the star over extended periods using two instruments at La Silla to look for signs of the star “wobbling” in its own spin as a result of planetary gravitational influences. Once identified, ESO called on other observatories around the world to carry out similar observations / comparisons to confirm their findings.

Although the planet lies within the “Goldilocks zone”, just how habitable is it likely to be is still open to question. Stars like Proxima Centauri, which is roughly one-seventh the diameter of our Sun, or just 1.5 times bigger than Jupiter, are volatile in nature, all activity within them entirely convective in nature, giving rise to massive stellar flares. As Proxima-B orbits so close to the star, it is entirely possible that over the aeons, such violent outbursts from Proxima Centauri have stripped away the planet’s atmosphere.

In addition, the preliminary data from ESO suggests the planet is either tidally locked to Proxima Centauri, or may have a 3:2 orbital resonance (i.e. three rotations for every two orbits) – either of which could make it an inhospitable place for life to gain a toe-hold. The first would leave one side in perpetual daylight and the other in perpetual night, while the second would limit any liquid water on the surface to the tropical zones.

Nevertheless, the discovery of another world in one part of our stellar backyard does raise the question of what NASA’s upcoming TESS mission might find when it starts searching the hundreds of nearby stars for evidence of exoplanets in 2018.

Juno’s Second Pass Over Jupiter

NASA’s Juno space craft made a second successful close sweep over the cloud-tops of Jupiter on Saturday, August 27th to complete its first full orbit around the planet. Speeding over the planet at a velocity of 208,000 km/h (130,000 mph) relative to Jupiter, Juno passed just 2,400 km (2,600 miles) above the cloud tops before heading back out into space, where it will again slowly decelerate under the influence of Jupiter’s immense gravity over the next 27 days, before it once again swing back towards the gas giant.

“Early post-flyby telemetry indicates that everything worked as planned and Juno is firing on all cylinders,” said Rick Nybakken, Juno project manager at NASA’s Jet Propulsion Laboratory, as telemetry on the flyby started being received on Earth some 48 mins after the flyby, which occurred at 13:44 UTC.

All of Juno’s science suite was in operation during the passage over Jupiter’s clouds. However, due to speed at which the gathered data can be returned to Earth, and given it cannot all be relayed in one go or necessarily continuously, it will be a week or more before everything has been transmitted back to Earth. Nevertheless the science team are already excited by the flyby.

“We are getting some intriguing early data returns as we speak,” Scott Bolton, principal investigator of Juno from the Southwest Research Institute, stated. Some of that data included initial images of Jupiter captured as Juno swept towards the planet during the run-up to periapsis. “We are in an orbit nobody has ever been in before, and these images give us a whole new perspective on this gas-giant world,” Bolton added.

The next time Juno passes over Jupiter’s cloud tops will be on October 19th. It won’t pass quite as close to the planet on that occasion, but it will attempt a final main engine burn, designed to swing the probe into a much tighter, 14-day orbit, at which time the full science mission will get commence.

A Dark Matter Galaxy

Dark matter is hypothetical matter undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects on visible matter. It was postulated to explain the “missing mass” in the universe, as only about 4% of the total energy density in the universe can be seen directly. It is thought that around 22% of the universe is composed of dark matter, and the remaining 74% is believed to be dark energy, an even stranger component, distributed diffusely in space. However, direct evidence of both dark matter and dark energy and a concrete understanding of their nature have remained elusive.

Now cosmologists have evidence of a massive galaxy almost entirely composed of dark matter. While it is not the first such galaxy to be found, its sheer size makes it somewhat unique and worthy of study.

Called Dragonfly 44, after the telescope system which first spotted it a little over a year ago, the galaxy is located in a cluster of galaxies beyond out own called the Coma galactic cluster. It was initially thought to be an “ultra-diffuse galaxy”, one of 47 such formations found within the Coma cluster, and considered a new “class” of galaxy. However, as the team responsible for its discovery looked a little more closely at it, they realised that gravitational influences from surrounding galaxies should have pulled it apart – yet something was apparently gluing it all together.

Using the W.M. Keck Observatory and the Gemini North Telescope in Hawaii, the team studied the velocities of stars in Dragonfly 44 over the course of several months in order to assess the potential mass of the galaxy – the faster the stars move, the greater the mass. These studies indicated that Dragonfly 44 is roughly equivalent in mass to our own Milky Way – but only one-hundredth of 1% of that mass can be accounted for by stars and “normal” matter; the remaining 99.9% of Dragonfly 44 appears to be dark matter.

Exactly how so massive a galaxy came into existence is a mystery in itself – as is the reason for the way the visible stars within it appear to be gathered into dense clusters. Equally intriguing is the potential for other such massive galaxies largely comprising dark matter to exist – some of them possibly close enough for us to detect the feeble signals that may finally reveal the true nature of dark matter.

A Mini-Mars Movie and NASA and China Prepare for 2020

On August 19th, 2016, NASA released a short video of the landscape surrounding their Mars Science Laboratory rover, Curiosity. Made up of dozens of images captured by the rover’s Mastcam on August 5th, 2016 (sol 1,421), the white-balanced video celebrates the 4th anniversary of Curiosity’s arrival on Mars and reveals a stunning vista.

The film starts with a look at a part of the “Murray Buttes”, a region the rover has been heading towards since commencing its climb up “Mount Sharp” in September 2014. The largest visible mesa, one the extreme left of the video, is about 90 metres (300ft) from the rover, and stands about 15 metres (50 ft) high and is about 61.5 metres (200 ft) long. As the scene pans, smaller mesas can be seen, other with the distant walls of Gale Crater.

The relatively flat foreground is part of the geological layer called the “Murray formation”, which extends about 200 metres (650ft) up the side of “Mount Sharp” between “Pahrump Hills”, the area which marked the start of Curiosity’s investigations of the mound and “Murray Buttes”. Both the formation and the buttes are informally named for Bruce Murray (1931-2013), a Caltech planetary scientist, co-founder of The Planetary Society and a former director of NASA’s Jet Propulsion Laboratory, Pasadena, California.

Meanwhile, on Earth, NASA has confirmed that their next Mars rover – still referred to as the Mars 2020 mission and which will be a “Curiosity-class” rover mission, utilising much of the technology and design of the current MSL mission – will be launched atop a United Space Alliance Atlas 5 541 rocket, when it lifts-off from Earth some time between July and September of 2020. The cost of the launch has been pegged at US $243 million, with the overall mission budgeted at some US $2.1 billion – slightly less than the initial cost for the current MSL mission.

At the same time, China has revealed more about its own 2020 mission to Mars. This will comprise an orbiter and lander combination, with the lander carrying a rover vehicle down to the surface of Mars.

The rover will have a mass of around 200 kg (441 lb) and will be solar-powered. It’s mass, size and shape make it superficially similar to NASA’s Mars Exploration Rover Opportunity, and like Opportunity, it will have a primary surface mission duration of around 90-92 days. Its lander vehicle will be similar to the Chang’e lander used to place China’s slightly smaller Yutu rover on the Moon in December 2013.

A suite of 13 science instruments is planned for the mission, although the split between rover / lander / orbiter hasn’t been completely specified. China’s Administration of Science, Technology and Industry for National Defence (SASTIND) has only so far indicated the rover will carry camera systems, a radiation detector and a ground-penetrating radar capable of soundings to a depth of 400 metres (1,300 ft).

The orbiter will act as a communications relay between the  lander / rover and Earth, and among its suite of instruments is expected to carry an imaging system, radar mapping instrument, a spectrometer to look for methane in the atmosphere of Mars and a space particle detector.

The mission will be launched some time in July or August 2020, atop a Long March 5, which will be China’s most powerful launch vehicle when it enters service in 2016 as China’s most powerful launch vehicle. In addition to its own science programme, the mission will act as a precursor for a Mars sample / return mission China plans to undertake around 2030.

If successful, the Chinese and NASA 2020 missions, together with Europe’s ExoMars, could  mean there could be as many as five rover vehicles operating on Mars in 2021.

Back from the Dead

In 2006, NASA launched a pair of space vehicles called the Solar Terrestrial Relations Observatory (STEREO), designed to study coronal mass ejections (CMEs) which can wreak havoc with Earth’s magnetic field and disrupt satellites on orbit and terrestrial power grids. However, in October 2014, contact was lost with one of the craft – STEREO-B – whilst preparing it for solar conjunction, when it would be on the opposite side of the Sun relative to Earth for just over 3 months, and thus out of communication. The mostly like cause of the loss of contact was a malfunction in the craft’s orientation system, which may have set it spinning.

Since the loss of contact, there have been monthly attempts to re-establish communications with STEREO-B, and on August 21st, they finally paid off. Communications were re-established sufficiently well enough for the mission team to issue crucial commands that will hopefully enable contact to be maintained.

STEREO-B is far from fully operational, but the mission team received enough information in return to understand its overall condition, and start planning the vehicle’s recovery, including assessing its health, re-establishing full attitude control, and evaluating all subsystems and instruments, hopefully returning STEREO-B to a fully operational status.