Antioquia astronomer Óscar Macías, a native of the municipality of El Peñol, Antioquia, discovered with the support of an international team of 16 people, the first millisecond pulsars found in a dwarf galaxy (a smaller galaxy found within the Milky Way) called the Sagittarius spheroidal.
Finding pulsars could change everything that was believed about these smaller galaxies. Scientists thought that they were places so old that they had no energy to power the universe, and now that pulsars exist means that this would be possible. This happens because they are born from the death of supermassive stars and have energy. “They are old stars that are between 5,000 and 6,000 million years old,” explains Macías.
across the milky way there are about 100,000 pulsars and they continue to expand, but they were not believed to be in these very old places, much older than the Solar System. The Sagittarius dwarf galaxy is as old as the Milky Way, which is 13 billion years old, compared to the Sun, which is barely 5 billion.
“A millisecond pulsar can be the size of Medellín, but with the mass of the Sun compressed into that space, so they are very heavy. Just a spoonful of one of them weighs what Mount Everest weighs.
In this investigation, then, the protagonists are the pulsars and the galaxy. But how was it discovered that she could harbor old stars?
The history
It all started with the discovery made by the Fermi Gamma-ray Space Telescope a decade ago. The tool revealed that at the center of the Milky Way there’s a couple of giant bubbles made up of gamma radiation, with a diameter of 50,000 light years: they are gigantic.
Scientists did not understand what was the power source that was creating and feeding these huge bubbles in the galaxy and the first theory was that they existed because of the supermassive black hole that is in the center of the Milky Way injecting jets of energy particles. That was the first theory about the creation of the famous Fermi bubbles. That is how they were named and they are fascinating and enigmatic.
They have been so strong that the team of 14 scientists led by Óscar Macías and his colleague Roland Crocker from the Australian National University dedicated themselves to investigating the brightest point found within these bubbles and which they named the Fermi cocoon located in the southern lobe of the bubbles.
This brightest spot caught the attention of scientists and they decided to investigate it to figure out where the gamma radiation was coming from.
What they did was collect data from the GAIA and Fermi telescopes that had information about the stars in the Sagittarius dwarf galaxy and realized that the light patch from the Fermi cocoon matches the distribution of stars in that galaxy: the stars ( pulsars) injected gamma radiation into the bubbles and it is not from the black hole, as previously believed.
The hypothesis that is already almost confirmed (some studies are missing to corroborate) by scientists is that the Sagittarius galaxy has millisecond pulsars —which rotate on themselves a thousand times every second— and that when they rotate, they emanate the energy that feeds the Fermi bubbles.
How was it achieved?
The Antioquian scientist Óscar Macías —who is currently in Amsterdam and is the only Latin American to participate in the research— and his team knew that the Sagittarius galaxy could be observed from Earth and from human vision it can only be seen through the bubbles. That is to say, at the other end of the Earth, passing through the Fermi bubbles, is the galaxy.
This location of all the elements allowed scientists to observe the Fermi cocoon and the stars of the Sagittarius galaxy.
Undoubtedly, this discovery will change what was believed about the satellite galaxies because it was believed that within them there were no star births, no gases, and no new elements emanating energy. “It was thought that due to its narrow orbit around the Milky Way, it lost most of its interstellar gas and its stars were torn from the core in long streams,” says the professor.
That is why there were only two alternatives: either the gamma rays came from dark matter that annihilates and produces light (when dark matter dies, this type of energy is produced) or pulsars emit this radiation. They have already ruled out that it is dark matter, so the last option is pulsars.
While scientists are certain that millisecond pulsars are there, they will corroborate their existence through radio waves and detect the ancient pulsations of these stars.
And so?
Scientists prove that ancient stellar objects like pulsars They are capable of generating energy and injecting gamma rays into the Milky Way, which are particles that could be harmful to life on Earth if it were not for the planet’s magnetic field.
Gamma radiation can affect the missions of astronauts going to the Moon or Mars since this energy source can cause cancer in humans.
“In the future, artificial magnetic fields should be built to protect astronauts from this energy,” says the scientist.
The study is a reason to reassess the high-energy emission capabilities of stellar objects thought to be inactive like these galaxies. It may also be a step to advance research on the annihilation of dark matter. It is believed that when this matter, “ubiquitous and mysterious substance”, is annihilated, it emanates great sources of energy.
For now, the Fermi bubbles are still there until it is confirmed that their creators are the pulsars discovered by Macías and his team of scientists from Antioquia.