Space News & Blog Articles

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. 

Artist impression of glory on exoplanet WASP-76b. Credit: ESA

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. 

Over the last few years I have been renovating my home. Building on Earth seems to be a fairly well understood process, after all we have many different materials to chose from. But what about future lunar explorers. As we head closer toward a permanent lunar base, astronauts will have very limited cargo carrying capability so will have to use local materials. On the Moon, that means relying upon the dusty lunar regolith that covers the surface. Researchers have now developed 20 different methods for creating building materials out of the stuff. They include solidification, sintering/melting, bonding solidification and confinement formation. But of all these, which is the best?

Apollo astronauts reported the surface of the Moon to be covered in a fine, powdery material, similar in texture to talcum powder. The material, known as the lunar regolith is thought to have formed by the constant bombardment from meteoroids over millions of years. The impacts bombarded the rocks on the Moon’s surface breaking them down into fine grains. The layer varies in depth across the surface from 5 metres to 10 metres and consists mostly of silicon dioxide, iron oxide, aluminium dioxide and a few other minerals. The fine nature of the dust makes it difficult for astronauts and machinery alike to operate on the surface and its sharp contours make it somewhat hazardous.

After taking the first boot print photo, Aldrin moved closer to the little rock and took this second shot. The dusty, sandy pebbly soil is also known as the lunar ‘regolith’. Click to enlarge. Credit: NASA

Any future engineers that visit the Moon to construct habitats will need to somehow employ the use of this material in their work. A paper published in the journal Engineering by Professor Feng from the Tsinghua University has conducted a review of possible techniques. Almost 20 techniques have been employed and these have been categorised into four main processes. 

In what I can only assume to be a process similar to concrete and its reaction with water, reaction solidification takes regolith particles and reacts them with other compounds. These will have to be transported to the Moon and, when mixed with regolith, will solidify. The process would create a solid material where regolith comprises 60% to 95% of the overall mixture. 

An alternative approach involves sintering or melting the regolith by subjecting it to high temperatures. The approach can create solid material composed of entirely regolith however, temperatures in excess of 1,000 degrees are required and this in itself will pose challenges and safety concerns on the lunar surface.