Tag Archives: Astronomy

Space update special: the 7-exoplanet system

An artist's impression of the sky from the outermost of the three TRAPPIST exoplanets in the star's habitable zone (see the 360-video below)

An artist’s impression of the sky from the outermost of the three TRAPPIST exoplanets in the star’s habitable zone (see the 360-video below). Credit: NASA

On Wednesday, February 22nd, US space agency NASA, working with a team of European astronomers, confirmed no fewer than seven extra-solar planets are orbiting a star some 39 light years away – with three of them within the so-called “Goldilocks zone” of habitability.

The star in question is TRAPPIST-1, named for the instruments used in its discovery, the Transiting Planets and Planetesimals Small Telescope (TRAPPIST),  and more formally known as 2MASS J23062928-0502285. Regular readers of my Space Sunday column might remember that I referred to the system back in November 2016, whilst discussing the James Webb Space Telescope and the hunt of exoplanets. The NASA announcement, which coincides with the publication of a new paper by the TRAPPIST team, adds dramatic new information to the distant star system.

The first two of the planets orbiting the star were located in May 2016, after the TRAPPIST team had studied the results of a continuous series of observations of the star between September and December 2015 using the telescope, located at the European Southern Observatory’s (ESO) La Silla Observatory in Chile.

Artist’s concept showing what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances. Credit: NASA

Artist’s concept showing what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances. Credit: NASA

What was intriguing about the two world was that not only were both within the so-called “Goldilocks zone” of their parent planet, where conditions might be “just right” for life to start, but both were roughly comparable to Earth in size, and therefore likely solid bodies, and spectral analysis suggested both have atmospheres.

A third planet, TRAPPIST-1d was also discovered the the same time, but it was behaving oddly. This prompted a further extended period of observation between September and October 2016, using both the ESO’s ground-based Very Large Telescope, and the Spitzer Space Telescope. This work revealed at “TRAPPIST-1d” was not one, but three worlds, again, all roughly in the Earth-sized category. Spitzer’s data additionally revealed two more planets of roughly the same size, taking the total to seven. Following this, Hubble turned its attention on the planets, looking for signs of hydrogen and helium – the chemical signatures that would indicate if any of them might be gas giants. It found none, further confirming they are likely rocky in nature.

The size, mass and density of these telluric worlds were obtained by measuring the periodic dips in TRAPPIST-1’s luminosity as a result of each of the planets passing in front of it. This allowed the international team studying the system to further assess whether each world was rocky, icy, or gaseous and determine which might be habitable.

trappist-1-3

Via: Space.com. Click for full size

TRAPPIST-1 is an ultra-cool red dwarf star only slightly larger than the planet Jupiter, and about 2,000 times dimmer than the sun.

Such stars, designated Class M, are the most frequent type of star in the Universe – making up an estimated 70% of stars in our galaxy alone. However, they do not radiate energy like our own sun, instead they are very volatile; all activity within them is entirely convective in nature, giving rise to massive stellar flares.

Given TRAPPIST-1 is so small, all of its planets orbit in very close proximity to it – closer than Mercury is to the Sun (the nearest orbits its parent star once every 1.5 terrestrial days, and the outermost, about once every 20 terrestrial days). This makes them very vulnerable to violent outbursts by the star, and could affect their surface conditions and their ability to retain an atmosphere.

This close proximity also means all of the planets are tidally locked – they always have the same side facing their sun. Thus they all are likely to have extremes of temperature, and those with an atmosphere are likely to have quite extreme weather as well. However – and conversely – it also means they could have the potential for liquid water to exist on their surfaces.

The innermost of the three planets in the habitable zone, TRAPPIST-1e, is very close in size to Earth, and receives about the same amount of light as Earth does, and may well have similar day time temperatures. The middle planet of the three, TRAPPIST-1f, meanwhile, might be a water rich world, also roughly the same size as Earth. It has a 9-day orbit, and receives about the same amount of light from its sun as Mars does from our own.

Another artist's impression of how the TRAPPIST system might look from the surface of one of the worlds - assuming they have liquid water present

Another artist’s impression of how the TRAPPIST system might look from the surface of one of TRAPPIST-1f, the middle one of the three planets in the star’s habitable zone – assuming it has liquid water present. Credit: NASA

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Space Sunday: Jupiter, Enceladus and Ceres; SLS, SpaceX and Dream Chaser

This stunning enhanced colour images of Jupiter's south polar region was captured by the JunoCam instrument aboard the Juno spacecraft on February 2nd, 2017. It reveals a complex series of interactions occurring in the fast-spinning atmosphere

This stunning enhanced colour images of Jupiter’s south polar region was captured by the JunoCam instrument aboard the Juno spacecraft on February 2nd, 2017. It reveals a complex series of interactions occurring in the fast-spinning atmosphere. Credit: NASA/JPL / SwRI

Following its latest close flyby of Jupiter – passing just 4,200 km (2,600 mi) above the gas giant’s cloud tops on February 2nd, 2017, NASA’s Juno mission spacecraft is now heading away from the planet once more and the next of its 53.5 day orbits. As I’ve previously reported in these Space Sunday columns, the original plan had been to use one of these close passes over the planet (October 2016), in conjunction with a sustained burn of the spacecraft’s British-built rocket motor, to move it into a short, 14-day period orbit around Jupiter.

However, a potential fault detected within the engine system meant the October burn was cancelled, and since then, engineers had been trying to assess if the issue  – a set of faulty valves – could be overcome, and the consequences of attempting an additional engine burn if not. No definitive answer has been found and so, following the February 2nd flyby, the decision was taken to cancel all plans for the engine burn and leave the spacecraft in its current 53.5 day orbit around Jupiter.

Doing so doesn’t compromise the overall mission objectives, but it does reduce the number of close passes over Jupiter the vehicle can make. If the reduced orbital period had been possible, the spacecraft would have made some 30 close flybys over Jupiter’s cloud tops during the primary mission period, set to end in July 2018. Remaining in the 53.5 day orbit means it will only make around 12 such close flybys in the same period.

The Juno spacecraft was supposed to complete two 53-day orbits around Jupiter, then lower its orbit Oct. 19 to fly around the planet once every 14 days. That engine burn has been postponed. Credit: NASA / JPL

The Juno spacecraft was supposed to complete two 53.5-day orbits around Jupiter in July and August 2016 (shown in green), before using its main engine to brake itself into a 14-primary science orbit (shown in blue). Due to continued concerns about the vehicle’s engine unit, the decisions has now been made to leave it in the 53.5 day orbit. Credit: NASA / JPL

A positive point with the spacecraft remaining in its more extended orbit is that it will spend less time within the harsher regions of Jupiter’s radiation belts, and could thus remain active for longer than the primary mission period – and mission planners are already considering applying for further funding to allow the mission to extend beyond July 2018. It also means that the spacecraft will be able to engage in additional science activities.

The close encounters with Jupiter have already allowed the spacecraft to probe deep within the planet’s cloud belts and discover they extend far deeper into the planet’s atmosphere than had been imagined, and that Jupiter’s magnetic field and auroras are more powerful than previously thought.

“Juno is providing spectacular results, and we are rewriting our ideas of how giant planets work,” Juno principal investigator Scott Bolton, of the South-west Research Institute in San Antonio, Texas, said of the decision to leave the spacecraft in its current orbit. “The science will be just as spectacular as with our original plan.”

NASA Considering Crewed Option for Orion / SLS First Launch

NASA is considering making the first launch of its new Space Launch System (SLS) rocket, currently slated for September 2018, a crewed mission.

Under the agency’s existing plans, the first launch of the new rocket, topped by an Orion Multi-Purpose Crew Vehicle and dubbed Exploration Mission 1 (EM-1), would have seen SLS send an uncrewed Orion vehicle to the Moon and back, with around 6 days spent in lunar orbit. A crewed flight of the SLS / Orion combination would not take place until at least 2021, when crew would use Orion to rendezvous to a small asteroid previously captured via robotic means and moved to an extended orbit around the Moon – an idea which has garnered a certain amount of criticism from politicians.

An artist's impression of a Space Launch System / Orion combination lifting off from Kennedy Space Centre's Pad 39B. Credit: NASA

An artist’s impression of a Space Launch System / Orion combination lifting off from Kennedy Space Centre’s Pad 39B. Credit: NASA

If approved, the new proposal – put forward by NASA’s Acting Administrator, Robert Lightfoot – would see the planned EM-1 mission pushed back to 2018 (allowing the Orion vehicle to be outfitted with the crew lift support and flight systems) and flown with a crew of two. While this would mean a delay in the initial launch of SLS / Orion, it could ultimately accelerate NASA’s plans, allowing the agency to present a wider choice of crewed missions in the 2020s, and respond to criticism that it is not doing enough to demonstrate how it plans to achieve a return to the Moon and / or  missions to Mars.

Enceladus: Cradle for Life?

On February 17th, 2005 NASA’s Cassini space probe, part of the Cassini / Huygen mission, made its first flyby of Saturn’s moon Enceladus.

Scientists were naturally curious about the 500 km (360 mi) diameter moon, which is the most reflective object in the solar system, but assumed it was essentially a dead, airless world. However, Cassini immediately found this was not the case.

A dramatic plume sprays water ice and vapor from the south polar region of Saturn's moon Enceladus. Cassini's first hint of this plume came during the spacecraft's first close flyby of the icy moon on February 17, 2005. Credit: NASA/JPL / Space Science Institute

A dramatic plume sprays water ice and vapour from the south polar region of Saturn’s moon Enceladus. Cassini’s first hint of this plume came during the spacecraft’s first close flyby of the icy moon on February 17, 2005. Credit: NASA/JPL / Space Science Institute

The first thing that happened was the magnetometer on the spacecraft revealed that Saturn’s magnetic field, which envelops Enceladus, was perturbed above the moon’s south pole in a way that didn’t make sense for an inactive world – it was as if there was some interaction with an atmosphere.

In the second flyby, a month later, Cassini found the interaction seemed to suggest a plume of water vapour was rising from the moon. Then, in the third flyby, in July 2005, the probe imaged geysers of water vapour erupting from the moon’s south polar region, and thus Enceladus became the target of intense study. So much so, that while only those initial 3 flybys of the moon had been a part of the primary Cassini /Huygens mission profile, the mission was updated to allow 20 more flyby of the moon.

Today, we know that beneath the mantle of ice enclosing Enceladus there is an ocean of liquid water – the geysers are the results of that water breaking through this ice and jetting into space, giving rise to Saturn’s E-ring in the process. This ocean is likely to be warmed and kept liquid by hydrothermal vents on the sea floor, and these in turn – just like the vents theorised to be on the ocean floor of Jupiter’s Europa – might provide all the ingredients for basic life to arise.

To celebrate the 12th anniversary of Cassini’s discoveries with Enceladus, NASA has released a video documenting those initial findings from 2005.

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Space Sunday: Martian quandaries, universal epochs and Jovian journeys

"Yellowknife Bay" a region examined by the Curiosity Rover in 2012/13 indicated that a lake was once present in Gale Crater. However, the same rock has revealed that potentially, there was not sufficient carbon dioxide present in the atmosphere to help keep the water unfrozen

“Yellowknife Bay” a region examined by the Curiosity Rover in 2013 indicated that a lake was once present in Gale Crater. However, the same rock has revealed that potentially, there was not sufficient carbon dioxide present in the atmosphere to help keep the water unfrozen. Credit: NASA

Mars scientists are wrestling with a problem. Ample evidence says ancient Mars was sometimes wet, with water flowing and pooling on the planet’s surface. Yet, the ancient sun was about one-third less warm and climate modellers struggle to produce scenarios that get the surface of Mars warm enough for keeping water unfrozen.

A leading theory is that ancient Mars had a thicker carbon-dioxide atmosphere forming a greenhouse-gas blanket, helping to warm the surface. However an analysis of data from NASA’s Mars rover Curiosity, suggests that even 3.5 billion years ago there was too little carbon dioxide present in the Martian atmosphere to provide enough greenhouse-effect warming to prevent water freezing.

The source of these findings is the very same bedrock in which the rover found sediments from an ancient lake in which microbes might have thrived. When analysing the bedrock, Curiosity detected no carbonate minerals, leading to the conclusion that Mars’ atmosphere was almost devoid of carbon dioxide when the lake existed 3.5 billion years ago. And that’s a quandary for scientists.

Curiosity took this selfie while at "Yellowknife Bay" in 2013 whilst gathering rock samples for analysis. Note that while the shadow of the rover's robot arm can be assn, the arm itself is blanked from the images purely as a result of the angles used in individual shots and the way the images have been stitched together to provide a view of the rover

Curiosity took this selfie while at “Yellowknife Bay” in 2013 whilst gathering rock samples for analysis. Note that while the shadow of the rover’s robot arm can be seen, the arm itself is blanked from the images purely as a result of the angles used in individual shots and the way the images have been stitched together to provide a view of the rover. Credit: NASA

“We’ve been particularly struck with the absence of carbonate minerals in sedimentary rock the rover has examined,” Thomas Bristow, the principal investigator for Curiosity’s Chemistry and Mineralogy (CheMin) instrument,  the primary source of the analysis work. “It would be really hard to get liquid water even if there were a hundred times more carbon dioxide in the atmosphere than what the mineral evidence in the rock tells us.”

In water, carbon dioxide combines with positively charged ions such as magnesium and ferrous iron to form carbonate minerals, and CheMin can identify carbonate if it makes up just a few percent of the rock. Yet Curiosity has made no definitive detection of carbonates in any lakebed rocks sampled since it landed in Gale Crater in 2012. However, other minerals – magnetite and clay minerals – not only indicated in the same rocks indicate the ions needed to form carbonates were readily available, they also provide evidence that subsequent conditions never became so acidic that carbonates would have dissolved away over time.

The dilemma between a warm, wet Mars and the lack of carbonates has actually been growing for years. For two decades researchers have been using spectrometers on Mars orbiters to search for carbonate that could have resulted from an early era of more abundant carbon dioxide in the atmosphere, only to find far less than anticipated. Yet clues such as isotope ratios in today’s Martian atmosphere continue to indicate the planet once held a much denser atmosphere than it does now, which has largely been seen as being rich in carbon dioxide. Thus, a paradox has arisen.

Curiosity uses a spectrometer on its robot arm to check a rock dubbed "John Klein" in "Yellowknife Bay" for its suitability as a drilling target, January 25th, 2013. The drill itself can be seen on the robot arm's "hand", pointing up and to the right

Curiosity uses a spectrometer on its robot arm to check a rock dubbed “John Klein” in “Yellowknife Bay” for its suitability as a drilling target, January 25th, 2013. The drill itself can be seen on the robot arm’s rotating “hand”, pointing up and to the right. Credit: NASA

It had been thought that the lack of evidence for carbonates when seen from orbit could simply be the result of  dust covering them, or the carbonates having moved underground. Finding them would thus resolve the paradox and reveal what had happened. However, the Curiosity results tend to overturn this idea. Simply put, the rover has failed to detect carbonate minerals precisely where they should be located, within rocks formed from sediments deposited under water.

“This analysis fits with many theoretical studies that the surface of Mars, even that long ago, was not warm enough for water to be liquid,” said Robert Haberle, a Mars-climate scientist at NASA Ames. “It’s really a puzzle to me.”

One idea put forward is that perhaps the lake was never a body of open water, but was covered in ice. The problem with this idea is none of the expected evidence for an ice-covered lake, such as large and deep cracks called ice wedges, or “dropstones,” which become embedded in soft lakebed sediments when they penetrate thinning ice, have been found. Thus, scientists have a lot of head scratching and theorising to do in order to make sense of the dilemma.

Traversing Mars with Curiosity

A simulated Curiosity rolls over the "Naukluft Plateau" in this still from Seán Doran's video simulation of the rover's traverse

A simulated Curiosity rolls over the “Naukluft Plateau” in this still from Seán Doran’s video simulation of the rover’s traverse. Credit: Seán Doran.

Ever wondered what it would be like to witness Curiosity trundling across the surface of Mars? Seán Doran has. What’s more, he’s been putting together animated films using Digital Terrain Model (DTM) data from the HiRISE imaging system on NASA’s Mars Reconnaissance Orbiter together with photomosaics of images from the rover, and combining them with a drivable correctly scaled model of the rover to provide movies of Curiosity as it rolls across Mars.

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Space Sunday: looking back on Earth and landing rockets and probes

The Earth and Moon, as seen from orbit over Mars, November 20th 2016

The Earth and Moon, as seen from orbit over Mars, November 20th 2016

Two marbles sit on a midnight background, one a swirl of blue, white, brown and green, the other tinted in shades of grey. Together they are the Earth and her Moon as seen by the most powerful imagining system currently orbiting the planet Mars.

It is, in fact a composite image, although Earth and the Moon are the correct sizes and the correct position / distance relative to one another. The images were captured by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter (MRO) on November 26th, 2016.

The images were taken to calibrate HiRISE data, since the reflectance of the moon’s Earth-facing side is well-known. As such, this is not the first image of our home planet and its natural satellite captured from Martian orbit, but it is one of the most striking. Whilst a composite image, only the Moon’s brightness has been altered to enhance its visibility; were it to be shown at the same brightness scale as Earth, it would barely be visible. That it appears to be unnaturally close to Earth is in fact an illusion of perspective: at the time the pictures were taken, the Moon was on the far side of Earth relative to Mars, and about to pass behind it.

The image of Earth shows Australia prominent in the central area of the image, its shape just discernible in this high-resolution image, taken when Mars and the MRO were 205 million kilometres (147 million miles) from Earth.

For me, this is another picture demonstrating just how small, fragile and unique our home world actually is.

 Falcon 9 Makes Triumphant Return to Flight

With Federal Aviation Authority (FAA) approval given, SpaceX, the private space company founded by Elon Musk, made a triumphant return to flight status with its Falcon 9 launch system on Saturday, January 14th.

January 14th, 2017: the SpaceX Falcon 9, carry 10 advanced Iridium Next communications satellites in its bulbous paylod fairing, lifts-off from Space Launch Complex 4E, Vandenberg Air Force Base, California Credit: SpaceX

January 14th, 2017: the SpaceX Falcon 9, carry 10 advanced Iridium NEXT communications satellites in its bulbous payload fairing, lifts-off from Space Launch Complex 4E, Vandenberg Air Force Base, California Credit: SpaceX

SpaceX launches had been suspended in September 2016, after a Falcon 9 and its US $200 million payload were loss in an explosion during what should have been a routine test just two days ahead of the planned launch (see here for more). Towards the end of 2016, and following extensive joint investigations involving NASA and the US Air Force (The Falcon 9 was located at Launch Complex 40 at the Canaveral Air Force Station when the explosion occurred), SpaceX were confident they had traced the root cause for the loss to a failure of process, rather than a structural or other failure within the vehicle itself. However, they had to wait until the FAA had reviewed the investigation findings and approved the Falcon 9’s return to flight readiness before they could resume operations.

The January 14th launch came via the SpaceX West Coast facilities, again leased from the US Air Force, and saw a Falcon 9 booster lift-off from Space Launch Complex 4E at Vandenberg Air Force Base in California. The rocket was carrying the first ten out of at least 70 advanced Iridium NEXT mobile voice and data relay satellites SpaceX will launch over the coming months, as Iridium Communications place a “constellation” of 81 of the satellites in orbit around the Earth in a US $3 billion project.

All ten satellites were successfully lifted to orbit and deployed following a pitch-perfect launch, which had to take place at precisely 9:54:34 local time (17:54:34 UT) in order for all ten satellites to be correctly deployed to reach their assigned orbits. However, all eyes were on the Falcon 9’s first stage, which was set to make a return to Earth for an at-sea landing aboard one of the company’s two autonomous drone landing barges, Just Follow The Instructions.

Down and safe: the Falcon 9 first stage, seen via a camera aboard the autonomous drone barge Just Follow The Instructions, shortly after touch-down on January 14th, 2017. Credit: SpaceX

Down and safe: the Falcon 9 first stage, seen via a camera aboard the autonomous drone barge Just Follow The Instructions, shortly after touch-down on January 14th, 2017. Credit: SpaceX

Operating the Falcon 9 on a basis of reusability is core to SpaceX’s future plans to reduce the overall cost of space launches. While the company has previously made six successful returns and landings with the Falcon 9 first stage, this being the first attempt since September 2016’s loss added further pressure on the attempt. but in the event, it went flawlessly.

After separation from the upper stage carrying the payload to orbit, the first stage of the Falcon 9 completed what are called “burn back” manoeuvres designed to drop it back into the denser atmosphere. Vanes on the rocket’s side were deployed to provide it with stability so that it dropped vertically back down to Earth, using its engines as a braking system and deploying landing legs shortly before touchdown – and the entire journey was captured on video, courtesy of camera built-into the rocket’s fuselage.

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