A pulsar reveals invisible structures in the Milky Way

2024-07-18 18:47:52

Researchers at the University of Notre Dame, in the United States, are using pulsars, which are considered the best clocks in the universe, to identify invisible structures floating in the Milky Way. The precision of these rapidly rotating neutron stars, which emit pulses of light, enables them to detect unknown massive objects that could be rogue planets, white dwarfs, brown dwarfs or even clumps of dark matter. with them.

Pulsars are a type of neutron star that rotates rapidly and emits regular pulses of electromagnetic radiation, especially in the form of radio waves. They are the remnants of massive stars that exploded as supernovae. The pulsars’ rapid rotation and strong magnetic field cause beams of radiation to be emitted from their magnetic poles.

When these beams pass the Earth, they can be detected as regular pulses, hence the name “pulsar.” These pulses are extremely precise, making them excellent “cosmic clocks” used in various astronomical research.

Millisecond pulsars are being used to detect gravitational waves, but there are more invisible things they can find. (Image: NASA Goddard Space Flight Center)

The theory of general relativity and pulsars

• The key idea behind the University of Notre Dame research comes from the theory of general relativity. Being within a gravitational field affects the passage of time.
• So, Professor John LoSecco reasoned that this could be measurable, as long as one knows very well how often these pulses emit their pulses of light.
• Fortunately, many groups of scientists are working on catalogs precisely like this.
• The purpose of these catalogs is to create the Pulsar Timing Array.
• By using the pulses and knowing them quite accurately, these stellar objects can be used as gravitational wave observatories, over thousands of light years.
• However, getting the required accuracy was quite a feat.

Remove the movement

“The pulsar does not exist by itself. These pulses come from these millisecond pulsars, many of which are found in binary systems. So they’re moving, they’re orbiting something else. And so you have to remove all that movement. The Earth is moving around the Sun You must remove this movement. You have to remove all this movement to get the real arrival time,” Professor LoSecco, from the University of Notre Dame, explained to IFLScience.

If you remove the movement you will have the exact interval of the pulses. And if a huge object passes in front of your pulse, suddenly the pulse increases. An object with the mass of the Sun would create a delay of 10 microseconds. That’s a small thing in terms of human timing, but for accuracy in the Pulsar Timing Array, it’s a huge value.

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Sensing massive objects

“There were 12 candidates and they come from eight independent pulsars,” LoSecco told IFLScience. The pulsar catalog used 65 millisecond pulsars tracked for up to 10,000 days. Some events are statistically very significant. The masses involved may be relatively small. One of the objects was about a fifth of the mass of the Sun.

If these candidates are real, the question is: what are they? They could be giant rogue planets — planetary objects kicked out of their planetary systems. They could be small stellar objects such as a brown dwarf or a white dwarf. They could be clumps of dark matter, floating around the galaxy. The honest astrologer is saying that we can’t decide yet.

The concentrations of masses found are not necessarily planets or dark matter. (Image: sripfoto / Shutterstock.com)

“I was warned not to call them planets, not to call them dark matter, but to call them masses because you can’t tell what they are just by looking at the radio. I can’t even guarantee that they are dark. They could be a brown dwarf or some kind of white dwarf or something else,” Professor LoSecco told IFLScience.

Progress and future prospects

The ongoing research is exciting work and LoSecco is keen to hear other scientists’ views and opinions on the work. “I’m looking for people to review because it gives me ideas of what to go back and look at and be skeptical of the outcome,” he said.

Professor LoSecco presented his findings at this week’s National Astronomy Meeting at the University of Hull.