The Week in Space and Physics #15
Today’s Solar System is so ordered that, until somewhat recently, it almost seemed reasonable to believe it ran by clockwork. That is partly an artefact of the briefness of our civilization: on a longer scale, that of the hundreds of millennia, the planets drift, their orbits stretching and rebounding in unpredictable ways.
Yet that randomness is nothing compared to the chaos of the early Solar System. Violent collisions were common: a rock the size of Mars likely smashed into the Earth; Uranus somehow ended up on its side and something – though what we have no idea – almost halted the spin of Venus.
Some theories even suggest the early solar system had more planets; worlds since lost to the cold void of space amidst ancient turbulence. All this, however, ignores a complicating factor: the presence of other stars born with our Sun.
Stars form in clusters thousands strong; with each newborn star born less than a light year or so from any other. Over the aeons those sibling stars drift apart, scattering through the galaxy. A handful of the Sun’s sisters stars are known; but most are long gone, lost amongst the vastness of the galaxy. Traces of their presence, however, may remain imprinted on the solar system.
A new analysis of such infant clusters suggests that young stars occasionally steal planets from one another. Perhaps two percent of planets, the model says, are directly stolen, stripped from their parents by a passing star. Another two percent end up briefly alone, expelled from their homes, before they are adopted by another star. Others, less fortunate, are left to drift in the void alone; doomed to eternal darkness and cold.
Researchers think these stolen planets should be easy to find. They probably have unusual orbits and linger on the edge of solar systems, hundreds of billions of miles from their stars. Their chemical composition – if we can measure it – should also give them away, showing a subtle difference to other planets in their systems.
Does such a planet lie in our solar system? None of the known planets quite matches this description. They all, more or less, lie in the same plane and have steady, circular orbits. But there are hints that another planet lies in the distant darkness, far from the Sun. Could this be an interloper, a planet stolen or adopted long ago by our star?
A Cosmic Fountain of Youth
Black holes, new research suggests, might give birth to immortal stars: strange creatures feeding upon the streams of gas and debris rushing around their fringes. Such stars, if they really exist, are likely enormous: hundreds of times bigger than the Sun and millions of times brighter.
Galaxies occasionally go through active periods: a time when a sudden influx of new gas – perhaps from a collision with another galaxy – drives a wave of star birth. That gas can also feed a black hole; forming a disc of glowing gas, dust and debris swirling around the precipice of no return.
If a star happens to fall into this disc – which surely happens from time to time – they will find themselves amidst an almost inexhaustible source of fuel. Analysis suggests they would quickly fatten up, reaching three hundred times the mass of the Sun. Such behemoths should die quickly; burning through their fuel in ten million years or so.
Yet these stars have a way out. As they burn through their hydrogen fuel, they produce helium waste. Under the usual circumstances, this helium pollutes the star, forcing it to burn fuel less efficiently. On the edge of a black hole, however, powerful winds sweep away the helium, leaving the star to burn pure hydrogen.
That hydrogen fuel – normally exhausted within a few million years – is easily replaced from the gas swirling around the disc. The result is a massive star that can, if the galaxy stays active, theoretically live forever. Of course, these active periods are not eternal. Eventually even the most energetic galaxy calms down, the flow of gas ceases and the fuel source will begin to run low.
Still, the study could help resolve a puzzle. Astronomers know of around a hundred massive stars close to the heart of our galaxy, a place where such giants are not normally expected to be. Could these be leftovers from an active period in our galaxy, one that perhaps ended a few million years ago?
Black Hole Controversies
Researchers at the Event Horizon Telescope, a planet spanning radio observatory, recently made history publishing the first picture of the Milky Way’s central black hole. New research, however, suggests that image may just be an illusion; an artefact of data processing.
The Event Horizon Telescope is actually a collaboration of several telescopes scattered around the world. To capture images all these telescopes must work together, forming, in effect, a single vast radio observatory. The problem lies in the way the data from all these telescopes is combined into the final image.
That process requires astronomers to make certain assumptions about the data. Those are made with care – researchers even ran the process with several different assumptions to make sure the end results were the same. But a team based in Japan has now redone that work, and come up with a troublingly different result.
Their work suggests that the bright ring structure seen in the first black hole picture doesn’t actually exist. Instead they see two bright dots around the black hole, which, they think, correspond to jets of energy shooting away from the black hole.
Other astronomers seem sceptical. The ring around the black hole, they say, matches to theoretical predictions. The jets of energy should be faint at the frequencies observed; making it unlikely the telescope could pick them out so clearly. New measurements might help settle the dispute. The telescope has been hard at work making higher quality observations of M87*, the first black hole imaged.
Starliner a Success, At Last
Boeing’s Starliner capsule made a successful landing at White Sands, New Mexico last Wednesday evening. The touchdown brings an end to the capsule’s uncrewed test flight to the International Space Station and back. Its success likely paves the way for an important next step: to carry a crew of astronauts to the station.
This was Starliner’s second test flight: the first, held at the end of 2019, ended in failure. Software errors fired thrusters early, leaving the capsule in the wrong orbit. Unable to reach the station, Boeing were forced to bring Starliner back early and, ultimately, to redo the test.
After more than two years of remedial work, Boeing now seems to have fixed the core issues with Starliner. A few minor issues were encountered. Two thrusters failed during the flight and some delays occurred during docking, but these should not block further progress. NASA and Boeing will now start working towards a crewed test flight. That could take place later this year.