Category: Space Sunday

The European Southern Observatory (ESO), responsible for finding a planet orbiting the Sun’s nearest stellar neighbour, Proxima Centauri (see here for more), has now discovered another exoplanet orbiting a nearby star.

The star in question is Ross 128, a red dwarf located in the constellation of Virgo. As I’ve previously noted, red dwarf stars tend to be extremely violent in nature. Their internal action is entirely convective, making them unstable and subject to powerful solar flares, generating high levels of radiation in the ultraviolet and infra-red wavelengths which can leave planets like the one orbiting Proxima Centauri or those orbiting TRAPPIST-1 unlikely to support life.

However, Ross 128 is different. It is a “quiet” red dwarf; it experiences less in the way of flare activity, meaning any planets orbiting it will be exposed to less radiation and stellar wind. In particular, the planet discovered by ESO could potentially be habitable.

The planet, designated Ross 128 b, was discovered using the ESO’s High Accuracy Radial velocity Planet Searcher (HARPS), located at the La Silla Observatory in Chile. HARPS uses measurements of a star’s Doppler shift in order to determine if it moving back and forth, a sign that it has a system of planets. The data gathered by the instrument allowed astronomers to confirm Ross 128 b is a rocky world, with roughly 35% more mass than Earth, orbiting Ross 128 at a distance of about 0.05 AU, and with a period of 9.9 Earth days.

Measurements of Ross 128’s likely radiative output, combined with the planet’s distance from the star put it on or near the star’s habitable zone – the region around a star where a solid body planet might have both an atmosphere and liquid water on the surface. It receives around 38% more light from its star than Earth does from the Sun. This has allowed the team making the discovery to estimate that Ross 128 b’s equilibrium temperature is likely somewhere between -60 °C and 20 °C – close to what we experience here on Earth, making it a temperate planet.

That Ross 128 is a “quiet” older red dwarf, less prone to violent outbursts, means Ross 128 b may well have retained any atmosphere which may have formed around it. Whether or not Ross 128 b has an atmosphere has yet to be determined; if it does, given the planet is likely to be tidally locked, with the same same side always facing towards its star, any atmosphere the planet may have could be subject to extreme weather.

Even so, given what is currently known about Ross 128 b, were it to have an atmosphere and liquid water on the surface, it would be the closest potentially habitable exoplanet to Earth so far discovered. This alone means Ross 128 b is liable to be the subject of a lot of additional study over the coming months.

Nor is this the first time Ross 128 has been in the news this year. In July 2017, Abel Méndez, an astrobiologist at the Arecibo Radio Telescope, reported that on May 12th, 2017, during a 10-ten observation of Ross 128, the telescope received a 10-minute wide-band radio signal “almost periodic” in natures, and which decreased in frequency.

While some were quick to link this event with the November discovery of Ross 128 b, it’s worth pointing out that Arecibo, the Green Bank Telescope in West Virginia and the Allen Telescope Array (ATA) in northern California, have all spent time listening to Ross 128 without any of them hearing any repeat of the signal. Currently the most widely accepted explanation for the May 2017 signal is radio frequency interference from a satellite orbiting the Earth.

A Lava World with an Atmosphere?

And staying with exoplanets, 55 Cancri e, also named Janssen, has also been in the news this week.

One of the few exoplanets discovered prior to the Kepler mission, it is one of five planets orbiting 55 Cancri A, the G-class main sequence star which forms one half of the binary star system 55 Cancri, some 41 light years away from the Sun, in the constellation of Cancer. At 7.8 Earth masses, and with a diameter almost 50% that of Neptune, it has the distinction of being the first “super-Earth” discovered in orbit around a main sequence star similar to the Sun.

Discovered in August 20o4, the planet has been subject of extensive study. As the closest planet to its parent, it takes 2.8 days Earth days to complete one orbit, and is tidally locked, always keeping the same side facing its parent. A study of the planet using the Spitzer space telescope in 2013 led astronomers to the conclusion 55 Cencri e is likely carbon planet, dominated by lava flows on its sunward side. In 2016, observations using the Hubble Space Telescope indicated the planet may have a thin hydrogen and helium atmosphere with suggestions of hydrogen cyanide.

However, an international team led by Cambridge University in the UK, has been re-examining the data gathered by the Spitzer space telescope. Using an improved model of how energy would flow throughout the planet and radiate back into space, their findings indicate that temperatures on the “dark” side of the planet average 1,300 to 1,400 ^oC (2,400 to 2,600 ^oF), much closer to to the average 2,300 ^oC (4,200 ^oF) on the sunward side than previously thought.

These finding suggest 55 Cancri e has a far denser, more complex atmosphere than had been thought, one which acts as transfer mechanism for circulating heat around the planet. What’s more, this atmosphere may well contain nitrogen, water vapour and even oxygen—molecules found in our atmosphere, too—but with much higher temperatures throughout.

The overall conditions on the surface of the planet preclude free-flowing water or the opportunity for life to arise, but they also present a further mystery. Given its proximity to its parent star, in theory 33 Cancri 2e’s atmosphere should have been stripped away aeons ago by the solar wind. so there are still mysteries with the planet yet to be resolved.

Continue reading “Space Sunday: exoplanets and launch systems” →

Around the world on August 17th, 2017, some 70 telescopes and observatories – including the Laser Interferometer Gravitational-Wave Observatory (LIGO), responsible for confirming the existence of gravitational waves (see here and here for more) – quietly turned their attention on the same spot in the constellation Hydra.

“I don’t think it’s out of the question that this is the most observed astronomical event ever. It’s a thrilling notion, and a little overwhelming,” said LIGO spokesperson David Shoemaker. “We’ve got somewhere between a quarter and a third of all the world’s astronomers working with us.”

The reason? Hours earlier, an observatory in Chile had detected gravitational waves followed by a burst of gamma radiation – potentially the signature of two neutron stars colliding far beyond our galaxy. If so, the detection would be the first time gravitational waves have been observed originating from something other than the merger of two black holes. Hence, an alert was issued to observatories around the globe, resulting in the massed focusing on instruments on that single point in space.

Over the coming days, the data revealed that a collision between two neutron stars in what is referred two as a “kilonova”  – which sits between a star going nova and a super-massive star going supernova.  It marks the first confirmation that neutron star mergers can cause gamma ray bursts. However, there is much more to the event.

Neutron stars are the dense remnants of massive stars that long ago exploded as supernovae. The two stars in question are located in galaxy NGC 4993, 130 million light years from Earth. Originally, these stars were each around 10-20 times the mass of our sun; after each went supernova, they collapsed down to bodies around 16 km (10 mi) in diameter, comprised entirely of neutrons so densely packed, that despite their small size, each still had a mass perhaps twice that of our own Sun.

These two neutron stars, located close together, were gradually drawn together over the course of perhaps 11 billion years by their mutual gravities until they collided, venting huge amounts of energy across the spectrum and space-time in what astronomers call a “multi-messenger event”. It was the arrival of the light waves and gravitational waves here on Earth, 130 million years later, that astronomers from around the world were keen to observe, marking the first time a cosmological event of this nature has been observed in both gravitational waves and light, producing a huge amount of data for researchers to study.

Thanks to the alert sent out by the Chilean observatory, over 3,500 astronomers and more than 100 instruments  – including LIGO and a the Hubble Space Telescope responded, making the event the first to be observed through the detection of visible light and gravitational waves. Their findings are now being made public, and include some remarkable facts.

These include the first confirmation that neutron star mergers can cause gamma ray bursts – although there is some questions over what this might in fact mean. It also marks the first measurement of the universe’s expansion using gravitational waves.In addition, as the collision was recorded in wavelengths right across the electromagnetic spectrum, from radio to gamma rays, it is the first time a cosmological event of this nature has been observed in both gravitational waves and light. A further result of the observations is that astronomers have witnessed heavy elements being formed from the aftermath of the event.

“People have long suspected that heavy elements were made in neutron star mergers, but this is really the first time we’ve nailed that down,” Andrew Levan, an astronomer at the University of Warwick in the UK. “This merger made something like the mass of the Earth in gold, along with other heavy elements such as platinum, lead and uranium.”

It was actually the discovery that heavy elements were being formed in the material resulting from the collision which confirmed the event was an actual collision of two neutron stars. The elements would only be formed if neutrons were being ejected from the two stars to collide with lighter atoms in the surrounding space. Material would only be ejected if the objects in collision each had a surface, something black holes don’t have – they only have an event horizon.

This in turn indicated the event was far closer that the previous five detections of gravitational waves which have occurred since 2015. These have been the result of pairs of black holes merging, none of which have been closer than 1.3 billion light years away. That the gravitational waves were observed alongside of light waves also gave further confirmation of another of Einstein’s general relativity predictions: that light and gravitational waves travel and more-or-less the same speed.

Observations and data gathering continued after the initial explosion was detected, although the light from the collision faded over the 6-8 days following the event, and astronomers are keen to discover what has been left behind. Currently, the region of NGC 4993 where the kilonova occurred is obscured behind a cloud of matter and heavy elements, leading to questions on whether or not the two stars may have merged to form an even larger neutron star, or whether they collapsed into a black hole. Some of those studying the data gathered believe the gamma ray burst recorded after the initial detection of gravitational waves might be indicative of the latter, the result of matter left over from the event and collapse being drawn into the event horizon.

Summing up the significance of the event, astronomer Tony Piro from the Harvard–Smithsonian Centre for Astrophysics said, “The ability to study the same event with both gravitational waves and light is a real revolution in astronomy. We can now study the universe with completely different probes, which teaches things we could never know with only one or the other.”

Continue reading “Space Sunday: when neutron stars collide” →

I’ve written several times about the risk radiation poses to dee space missions; particularly Galactic Cosmic Rays (GCRs), the so-called “background radiation” left over from the big bang. As I’ve noted, while solar radiation – up to and including Solar Particle Events (SPEs or “solar storms”) can be reasonably well dealt with, on account of the particles being relatively low-energy – 13 centimetres (5 inches) of water or similar liquid – is pretty good protection against the primary radiation threat of SPEs, for example – GCRs are far harder to deal with.

However, there are materials which can block them. Again, I’ve written about Hydrogenated boron nitride nanotubes (BNNTs). These are something being developed by NASA’s Langley Flight Centre in Virginia; extremely flexible, they can be used in the construction of key elements of space vehicles – walls, floors, ceilings, for example – and can even be woven into a material used as a lining in space suits to protect astronauts.  Similarly, borated polyethylene – already used for radiation shielding in nuclear reactors aboard US naval vessels, medical vaults and linear accelerators, among other applications – offers a means to provide primary radiation protection within the structure of space vehicles.

However, these are only effective in stopping primary radiation damage – that is, damage cause by the direct impact of radiation on living cells. A far, far greater risk people in deep space will face is from so-called secondary radiation,  particularly in the case of GCRs.  simply put, when a GCR particle collides with another, it sends energetic neutrons, protons and other particles in all directions, which can collide with others. It’s like a bullet striking something and scattering shrapnel, potentially doing damage to a lot of cells if they strike a living body. The problem here is that the more material used to block the effects of primary radiation damage, the more the risk of secondary radiation damage is increased.

This means that there is unlikely to be a single solution to the issue of radiation exposure on deep space missions such as to Mars. Which is why scientists aren’t looking for one. NASA, for example has been conducting research into technologies such as BNNTs and magnetic shielding for space vehicles for over a decade. The latter, if possible, would use a magnetic field around a space vehicle to protect the crew, much as Earth’s magnetic field protects us. The problem here is that such systems currently require huge amounts of electrical power and can add a significant amount of mass to a space vehicle.

Another avenue of research being investigated is the use of pharmaceuticals as possible radiation inhibitors. Drugs such as potassium iodide, diethylenetriamine pentaacietic acid (DTPA) and the dye known as “Prussian blue” have for decades been used to treat radiation sickness. The theory is now that they could be used as part of a preventative regime of preventative treatment for astronauts on deep space missions.

The whole subject of radiation protection has become a focus in light of NASA’s “new” directive to return humans to the Moon and also because of Elon Musk’s determination to send humans to Mars, possibly as early as the mid-2020s. Because of this, NASA has been highlighting its research into radiation exposure management of late, which also includes solar weather forecasting (to help warn crews in deep space about the risk of SPEs, etc.), and in looking at 20+ years of orbital operations aboard the shuttle ISS and Russia’s MIr space station. All of this is leaving some at NASA feeling very positive about efforts to send humans beyond Earth orbit, as Pat Troutman, the NASA Human Exploration Strategic Analysis Lead, stated in a NASA press statement on the matter:

Some people think that radiation will keep NASA from sending people to Mars, but that’s not the current situation. When we add the various mitigation techniques up, we are optimistic it will lead to a successful Mars mission with a healthy crew that will live a very long and productive life after they return to Earth.

Whether progress on all fronts will be sufficiently advanced to encompass something like Elon Musk’s aggressive approach to human missions to Mars remains to be seen. However, with the “new” directive for NASA to return humans to the Moon, there’s a good chance we’ll see some of the current initiatives in radiation protection bearing fruit in the next few years.

The Risk Posed by Tiangong 1

Tiangong 1 (“Heavenly Palace 1”), the first Chinese orbital facility has been creating some sensationalist headlines of late.  Launched in 2011, the facility saw two crews spend time aboard it, prior to it being run on an automated basis from 2013. On March 21st, 2016 the Chinese Manned Space Engineering Office announced that they had disabled the facility’s data service in preparation for shifting their focus to the (then) upcoming Tiangong 2 facility and in allowing Tiangong 1’s orbit to decay so it would burn-up re-entering the upper atmosphere.

The time-frame from re-entry was predicted to be late 2017 / early 2018. However, around the time Tiangong 2 was launched the Chinese space agency admitted they’d lost attitude control of the laboratory, so they could no longer orient it as it orbits the Earth. As a result, the facility has been under scrutiny from Earth by individuals and groups monitoring the rate of its orbital decay.

One of these observers is astrophysicist Jonathan McDowell of Harvard university. In early October he released a statement indicating that as a loss of attitude control coupled with increased atmospheric friction has resulted in a sharp decline in Tiangong 1’s altitude to the point where it could see the vehicle re-enter the Earth’s atmosphere in the next few months. He also noted – accurately – that some elements of the 8.5 tonne vehicle could survive re-entry and reach the surface of the Earth (something the Chinese have always noted).

Unfortunately, his report led to some sensationalist responses from portions of the media. For example, one UK media tabloid blasted: “Out-of-control space station to smash into Earth THIS MONTH…and it could hit ANYWHERE. … A MASSIVE space station is hurtling towards Earth!” (block capital their own, not mine); other newspapers also highlighted the upper-end of the risk posed by the vehicle’s re-entry.

Needless to say such reports wildly over-egg the situation. The reality is that Tiangong’s orbit carries it over vast swathes of ocean and large areas of sparsely populated land. As such, while there is a risk of parts of the station reaching the ground, the chances of them hitting a populated area are remote. In this, Tiangong reflects the US Skylab mission in 1979 and the Russian Salyut 7 / Cosmos 1686 combination of 1991. Both of these where much larger than Tiangong 1 (77 tonnes and 40 tonnes respectively), both made an uncontrolled re-entry, and in both cases, wreckage did not cause loss of life.

Continue reading “Space Sunday: radiation, rings and pollution” →