The Week in Space and Physics: The Old Smokers
The Week in Space and Physics: The Old Smokers
On new stars in the galaxy's centre, the next great observatory, Apophis and the dark fate of the gas giants.
The heart of our galaxy is a crowded place. Some ten million stars lie within three light years of its central point, locked in orbit around a supermassive black hole. Beyond that lies the galactic bulge; a collection of ten billion stars stretching ten thousand light years across.
That bulge must surely be a spectacular sight, but it is one mostly hidden from our eyes. Countless clouds of dust and gas lie between us and the galactic centre, blocking almost all the visible light coming from it. For a long time, then, the exact nature of the centre, and the stars that exist there, was mysterious.
Fortunately infrared telescopes can see through the haze of dust and gas, and so can reveal the secrets of the galactic centre. One such telescope - VISTA, located in the Atacama desert of Chile - spied out the shape of the galaxy’s heart in 2013, revealing the central bulge to look something like a peanut. Similar peanut bulges have been seen in other galaxies, and put together the evidence suggested the Milky Way has a barred spiral shape.
VISTA did not end its work there, however. Over the last decade, the telescope has taken part in a long term survey of the galactic bulge. The work aimed to create a dynamic portrait of the region, mapping out the centre of the Milky Way in time as well as space.
Among the billion stars the survey watched, some have turned out to be especially interesting. VISTA captured the outbursts of newborn stars, flaring out extreme eruptions of energy. More than thirty such events were seen, with some of the stars suddenly becoming hundreds of times brighter. Why this happens is still unknown, but it seems to result in a period of instability around the star, perhaps hindering the birth of new planets.
At least seven other stars appear to be of a new type, previously unknown to science. Each is an old star, passing through a late phase of stellar life in which they become red giants. For much of the time these stars are barely noticeable, glowing only faintly in their old age. Every now and then, however, they would suddenly throw out a cloud of dust, earning them the nickname ‘old smokers’.
The researchers behind the discovery note that the centre of the galaxy is rich in heavy elements. It is possible, they say, that those elements help the smoke clouds form, and thus explain why we see them only in the heart of the galaxy. In turn those stars may be helping to spread heavy elements through the Milky Way. The old smokers may, indeed, be sowing the seeds of the next generation of stars.
The Search for Life
Throughout the 1990s and early 2000s, NASA ran a program known as the Great Observatories. Thanks to it, four powerful telescopes were placed into orbit: Compton, Chandra, Spitzer and Hubble. Together they surveyed the cosmos in different frequencies of light, spanning from high energy gamma rays to visible light.
These telescopes pushed the limits of what space technology could do, leading to advances in optics and sensors that are now enabling even more powerful observatories. Individually they each made major discoveries, changing their areas of astronomy. By working together they helped reshape our understanding of the cosmos, allowing researchers to study the same object in a multitude of wavelengths.
That project, however, came to an end in the 2000s. Afterwards, much of NASA’s attention shifted to developing the James Webb, which finally reached space in 2021. With that done, NASA now has a chance to work on a new set of telescopes. First up will be the Nancy Grace Roman Telescope, which should launch in 2027. After that, NASA hopes to build a new generation of great observatories.
For now three telescopes are envisioned, each of which will launch during the 2040s. The first will be the Habitable Worlds Observatory, a six metre wide telescope designed to search for signs of life on distant planets. After will come an X-ray telescope, capable of picking out clouds of hot gas around black holes and in the hearts of galaxies, and an infrared telescope, designed to peer into the early universe.
NASA has already started work on the first of these, the Habitable Worlds Observatory. The project kicked off last year, with groups set up to sketch out a design and examine the science it could do. That, as a paper published in January laid out, includes selecting the planets it might survey.
The report includes a list of more than one hundred and sixty possible stars, each of which scientists think might have habitable worlds around them. Around fifty of them are considered ‘Tier A’, marking them out as especially promising. Each is likely to get studied in more detail; and one of them - in around two decades - could become the first known to host life beyond Earth.
Preparing for Armageddon
For a brief time, Apophis was considered the most dangerous asteroid in the Solar System. When it was discovered, in 2004, astronomers tracked its orbit and realised it would come perilously close to Earth in April 2029. Even if it missed - which was likely - a collision might follow a few years later, in 2036.
Fortunately later observations ruled these possibilities out. Apophis is no longer considered a threat to Earth - which is a good thing, given it is big enough to wipe out a small country. Still, Apophis will come startling close to Earth. On April 13, 2029, the asteroid will pass just twenty thousand miles over the Atlantic Ocean, placing it within touching distance of many of our satellites.
NASA has already redirected one of its probes to take a closer look at Apophis. Osiris-Rex, which recently returned a sample from the asteroid Bennu, is now heading towards Apophis, which it will spend around eighteen months examining in detail. Researchers hope that study will help rule out the prospect of any future impact.
This week, however, NASA is holding a workshop to consider ideas for other missions to visit Apophis. One possibility is to send two small satellites originally built to visit more distant asteroids. That mission was cancelled last year, and the satellites - already finished - were placed into storage.
Still, money seems to be an issue for NASA, and the agency appears reluctant to start work on new projects when ongoing ones - such as the Mars Sample Return and Titan explorer Dragonfly - are facing budget problems. The close approach of Apophis, though, may be too good an opportunity to miss.
The Afterlife of a Solar System
In a few billion years time, our Sun will begin to die. At first it will expand, growing into a red giant. Its outer layers could stretch as far as the orbit of Venus, and the innermost planets - from Mercury to Earth - will be consumed in its fire. The outer planets, however, will survive; and then go on to orbit the cooling dwarf star that our Sun will eventually become.
Though many examples of such dwarf stars are known, few planets have so far been found around them. Recently, however, two such worlds were spotted by the James Webb telescope. Both planets, which were seen around two separate stars, seem to be Jupiter-sized gas giants.
They could, therefore, offer a glimpse of the ultimate fate of our solar system. Though the Sun will burn on for another five billion years, it will eventually exhaust its fuel and die. But unlike bigger stars, it will linger on for billions of years more as a fading dwarf. Jupiter and Saturn would seem to have a long, dark afterlife ahead of them.