Space News & Blog Articles

Solar Sails are an enigmatic and majestic way to travel across the gulf of space. Drawing an analogy to the sail ships of the past, they are one of the most efficient ways of propelling craft in space. On Tuesday a RocketLab Electron rocket launched NASA’s new Advanced Composite Solar Sail System. It aims to test the deployment of large solar sails in low-earth orbit and on Wednesday, NASA confirmed they had successfully deployed a 9 metre sail. 

In 1886 the motor car was invented. In 1903 humans made their first powered flight. Just 58 years later, humans made their first trip into space on board a rocket. Rocket technology has changed significantly over the centuries, yes centuries. The development of the rocket started way back in the 13th Century with the Chinese and Mongolians firing rocket propelled arrows at each other. Things moved on somewhat since then and we now have solid and liquid rocket propellant, ion engines and solar sails with more technology in the wings. 

Solar sails are of particular interest because they harness the power of sun, or star light to propel probes across space. The idea isn’t knew though, Johannes Kepler (of planetary motion fame) first suggested that sunlight could be used to push spacecraft in the 17th Century in his works entitled ‘Somnium’. We had to wait until the 20h Century though before Russian scientist Konstantin Tsiolkovsky outlined the principle of how solar sails might actually work. Carl Sagan and other members of the Planetary Society start to propose missions using solar sails in the 70’s and 80’s but it wasn’t until 2010 that we saw the first practical solar sail vehicle, IKAROS.

The concept of solar sails is quite simple to understand, relying upon the pressure of sunlight. The sails are angled such that photons strike the reflective sail and bounce off it to push the spacecraft forward. It does of course take a lot of photons to accelerate a spacecraft using light but slowly, over time it is a very efficient propulsion system requiring no heavy engines or fuel tanks. This reduction of mass makes it easier for solar sails to be accelerated by sunlight but the sail sizes have been limited by the material and structure of the booms that support them. 

NASA have been working on the problem with their Next Generation Solar Sail Boom Technology. Their Advanced Composite Solar Sail System uses a CubeSat built by NanoAvionics to test a new composite boom support structure. It is made from flexible polymer and carbon fibre materials to create a stiffer, lighter alternative to existing support structure designs. 

Scientists detected the first long-predicted gravitational wave in 2015, and since then, researchers have been hungering for better detectors. But the Earth is warm and seismically noisy, and that will always limit the effectiveness of Earth-based detectors.

Is the Moon the right place for a new gravitational wave observatory? It might be. Sending telescopes into space worked well, and mounting a GW observatory on the Moon might, too, though the proposal is obviously very complex.

Most of astronomy is about light. The better we can sense it, the more we learn about nature. That’s why telescopes like the Hubble and the JWST are in space. Earth’s atmosphere distorts telescope images and even blocks some light, like infrared. Space telescopes get around both of those problems and have revolutionized astronomy.

Gravitational waves aren’t light, but sensing them still requires extreme sensitivity. Just as Earth’s atmosphere can introduce ‘noise’ into telescope observations, so can Earth’s seismic activity cause problems for gravitational wave detectors. The Moon has a big advantage over our dynamic, ever-changing planet: it has far less seismic activity.

We’ve known since the Apollo days that the Moon has seismic activity. But unlike Earth, most of its activity is related to tidal forces and tiny meteorite strikes. Most of its seismic activity is also weaker and much deeper than Earth’s. That’s attracted the attention of researchers developing the Lunar Gravitational-wave Antenna (LGWA).

Well over 5,000 planets have been found orbiting other star systems. One of the satellites hunting for them is TESS, the Transiting Exoplanet Survey Satellite. Astronomers using TESS think they are made a rather surprising discovery; their first free-floating – or rogue – planet. The planet was discovered using gravitational microlensing where the planet passed in front of a star, distorting its light and revealing its presence.

We are all familiar with the eight planets in our Solar System and perhaps becoming familiar with the concept of exoplanets. But there is another category of planet, the rogue planets. These mysterious objects travel through space without being gravitationally bound to any star. Their origin has been cause for much debate but popular theory suggests they were ejected from their host star system during formation, or perhaps later due to gravitational interaction. 

Simulations have suggested that these ‘free-floating planets’ or FFPs should be abundant in the Galaxy yet until now, not many have been detected. The popular theory of ejection from star systems may not be the full story though. It is now thought that different formation mechanisms will be responsible for different FFP masses. Those FFPs that are high mass may form in isolation from the collapse of gas whilst those at the low mass end (comparable to Earth) are likely to have been subjected to gravitational ejection from the system. A paper published in 2023 even suggests that those FFPs are likely to outnumber those bound planets across the Galaxy!

Detecting such wandering objects among the stars is rather more of a challenge than you might expect. Their limited emission (or reflection) of electromagnetic radiation makes them pretty much impossible to observe. Enter gravitational microlensing, a technique that relies upon an FFP passing in front of a star, it’s gravity then focussing light from the distant star resulting in a brief brightness change as the planet moves along its line of sight. To date, only three FFPs have been detected from Earth using this technique. 

A team of astronomers have been using TESS to search for such microlensing events. TESS was launched in April 2018 and whilst in orbit, scans large chunks of sky to monitor the brightness of tens of thousands of stars. The detection of light changes may reveal the passage of an FFP as it drifts silently in front of the star. It’s not an easy hunt though as asteroids in our Solar System, exoplanets bound to stars and even stellar flares can all give false indications but thankfully the team led by Michelle Kunimoto have algorithms that will help to identify potential targets.