Ask Space

Plants grown in space can help feed astronauts

SPACE EXPLORATION

Does astrobotany help future space exploration efforts?

Astrobotany is going to be critical for future space exploration, particularly in the realm of providing caloric support for extended spaceflight missions. In the near future it’s unlikely we will use plants as an oxygen source in a bioregenerative life-support system (BLSS) because gas exchange is more easily controlled manually than relying on plants to produce enough oxygen to support a crew. The science is just not precise or reliable enough to depend on just plants for oxygen. However, it will be a huge benefit to supplement caloric intake with plants in space.

The sustainability of harvest in space is another perk that cannot go overlooked. Resupplies to the International Space Station (ISS) are necessary, but resupplies beyond the relatively short distance to the ISS could become impossible, or not time or cost effective. Future missions will need to rely on sustainable plant growth to supplement caloric intake, and the added benefit is that it is supposed to be an immense help for astronaut’s mental health.

SOLAR SYSTEM

How do we predict space weather?

The Sun and interplanetary space are monitored for notable changes in solar-related phenomena that can provide forecasters clues about the chances for space weather storms. Space weather generally refers to activity on the Sun, in the large vacuum of space between Earth and the Sun and ultimately here at and around Earth. The Space Weather Prediction Center (SWPC) in Boulder, Colorado, is continuously staffed to monitor space weather and provide daily forecasts. Additionally, the SWPC issues warnings and alerts about substantial space weather storms and events, because they may impact technologies we rely upon today. The Sun goes through an 11-year cycle whereby solar activity is less common at solar minimum and more frequent at solar maximum. We are now heading towards solar maximum this year, so not only will solar activity increase, but strong space weather storms will become more probable. You can visit swpc.noaa.gov for all sorts of current space weather information and forecasts.

SPACE EXPLORATION

Is anyone responsible for space debris?

Space is an area beyond national jurisdiction. Like the high seas, space is governed through international law. The 1967 Outer Space Treaty and four other international space treaties that followed set out a framework and key principles to guide responsible behaviour. The 1972 Liability Convention specifies a compensation regime that would apply in many circumstances of damage caused by space debris falling to Earth, as well as when satellites collide in space.

This legal regime imposes liability on ‘launching states’ for damage caused by their space objects, which includes an absolute liability regime when they crash to Earth as debris. The liability under international space law is therefore imposed on countries, even where the space object or debris that causes the damage is privately owned or operated. The Liability Convention has only been previously invoked once – for the Cosmos

954 incident of 1978 – and therefore may not be regarded as a powerful disincentive. However, it’s likely to come into play in the future in a more crowded space environment and with more uncontrolled re-entries. Of course, this legal framework applies only after the damage occurs.

In addition, there are other regulatory ‘rules of the road’ that deal with space governance agreed through the United Nations Committee on the Peaceful Uses of Outer Space, including practical guidelines for debris mitigation and long-term sustainability of space activities. A globally coordinated space traffic management system will also be vital to avoid collisions that would result in loss of control of satellites, leaving them to tumble helplessly in orbit or fall back to Earth.

STARS

Why do discs form around young stars?

Many processes play a role in disc formation, but angular momentum is the principal quantity. The protostar and its disc are formed from the same cloud composed of gas and dust, which initially has some rotation – it has angular momentum, which is a measure of the direction and speed that something is rotating. The cloud collapses due to its own gravity, but angular momentum hinders this process, and the cloud collapses into a rotating ‘pancake’ rather than a sphere. If the central region contains enough dense gas, then a rotating protostar will form.

The gas and dust surrounding the new star continue to rotate. The amount of angular momentum that this gas and dust contains is one of the primary quantities that will determine its fate. If there is too little angular momentum, then the gas and dust will fall onto the star and increase its mass. However, if there is enough angular momentum, then the gas and dust will remain as a rotationally supported protostellar disc. At a large enough distance from the protostar, the orbiting gas and dust will no longer be rotationally supported, indicating the outer edge of the disc. This edge is reasonably well-defined, making the disc distinct from its surroundings.

STARS

What makes stars?

The interstellar medium – the material which fills the space between stars – provides the necessary raw materials for new stars to be born. It is made up of mostly hydrogen, some helium and a tiny amount of dust particles. Within the interstellar medium there are clouds of varying densities that are rich in molecules like hydrogen and carbon monoxide. These molecular-rich gas and dust clouds provide the ingredients that ultimately make up the building blocks of stars. In the densest regions of the interstellar medium, the core collapse of such a cloud can be triggered by a shock wave. These shock waves can be caused by a nearby supernova explosion, by a collision with another molecular cloud or even by passing through the spiral arm of a galaxy, like our very own Milky Way. Such a shock wave can cause the rapid infall of the molecular material to produce the core of a new star, which continues to accrete as the new star is born. These regions in the interstellar medium are stellar nurseries in the cosmos and are critical to the cycle of the life of a star.

SPACE EXPLORATION

How do spaceflight experiences change an astronaut’s life?

There are so many unforgettable aspects of life in space, including the experiments, the robotics and the spacewalks, but I think my most memorable moment took place when Peggy [Whitson, commander of the ISS’ Expedition 16] and her crew invited us to have dinner over in the service module. “You guys bring the vegetables, we’ll bring the meat,” they said, and we all congregated around the small table, with some floating above and others below. There we were: French, German, Russian, Asian-American, African-American, all listening to music and having a meal in space. Out the window we could see Afghanistan, Iraq and other troubled spots. 240 miles [386 kilometres] above those strife-torn places, we sat in peace with people we once counted among our nation’s enemies, bound by a common commitment to explore space for the benefit of all humanity. It was one of the most inspiring moments of my life. That day, I gained a newfound perspective on how it’s possible for different people to live and work together – definitely needed to bring that hope and optimism back home to planet Earth.

ASTROPHYSICS

Do we understand more about black hole mergers?

Hugely so. 20 years ago, you could still make an argument that maybe black holes aren’t real – they’re just a figment of mathematics. But with the Laser Interferometer Gravitational-Wave Observatory, with the collision of two black holes giving that first ripple in the fabric of space, and with Event Horizon Telescope, black holes have really come into their own. For someone like me who works on cuttingedge theoretical ideas, we’re struggling now to merge black holes and quantum mechanics to get a full understanding. And black holes are the prime theoretical laboratory for pushing our ideas to the limit. When we can fully understand black holes and quantum mechanics, I suspect our understanding of the universe is going to jump to a new level.