High-energy transient signals are most often determined to be gamma-ray burst events, but the recently-launched Einstein Probe has expanded astronomers’ ability to quickly respond to similar signals occurring at X-ray wavelengths. Now, a multi-wavelength study of EP240408a concludes that while many of the signal’s characteristics might lead to the conclusion that it is a gamma-ray burst, the non-detection at radio wavelengths precludes that possibility.
Recent News
Students Contribute to New Understanding of ‘Twinkling’ Pulsars
The flexible observing setup of the Green Bank Observatory’s 20-meter telescope enabled frequent, long-duration observations of eight pulsars, spanning two and a half years for a student-driven study carried out by students in the Pulsar Science Collaboratory program.
Double the Disks, Double the Discovery: New Insights into Planet Formation in DF Tau
Tucked away in a star-forming region in the Taurus constellation, a pair of circling stars are displaying some unexpected differences in the circumstellar disks of dust and gas that surround them. A new study led by researchers at Lowell Observatory, combining data from the Atacama Large Millimeter/submillimeter Array (ALMA) and Keck Observatory, has unveiled intriguing findings about planet formation in this binary star system, known as DF Tau, along with other systems in this region.
How Radio Astronomy Sees Magnetic Fields
Illustration of the magnetic field of a red dwarf star. Credit: Dana Berry; (NRAO/AUI/NSF)
Many objects in the Universe have magnetic fields. Planets such as Earth and Jupiter, the Sun and other stars, even galaxies billions of light years away. But these magnetic fields don’t typically emit light astronomers can see, not even in radio. So how do astronomers study the magnetic fields of distant stars and galaxies?
Although magnetic fields don’t emit light, charged particles moving in these magnetic fields often do. For example, aurora on Earth are caused by charged particles from the solar wind that are captured by Earth’s magnetic field. They spiral along the magnetic field lines until they strike our atmosphere near the north and south magnetic poles, which can create both visible and radio light. We can see the aurora on Earth and Jupiter as a beautiful curtain of colors. Astronomers have even observed the radio glow of the aurora of a brown dwarf.
When magnetic fields are extremely strong, charged particles caught in these fields can be accelerated to incredible speeds. As they accelerate around the magnetic field, the charges can emit light directly. It’s known as synchrotron radiation, and it’s often seen coming from the heated accretion disks of black holes. Astronomers can use synchrotron radiation to measure how fast the charges are moving, and how strong the magnetic field is. It has helped us understand how black holes can tear apart and consume stars and also lets astronomers determine the size of distant black hole.
The magnetic field in the distant 9io9 galaxy, as captured by ALMA. Credit: ALMA (ESO/NAOJ/NRAO)/J. Geach et al.
Astronomers can also map weak magnetic fields. The magnetic field of the Milky Way isn’t as strong as Earth’s, but it permeates our entire galaxy. Our galaxy is filled with charged particles in the form of ionized interstellar gas. This ionized gas doesn’t emit much light on its own, but it does affect light passing through it, particularly polarized light such as that emitted by pulsars. When polarized light passes through an ionized gas, its orientation rotates. The amount the polarization rotates depends on the frequency of the light. By comparing the polarization of pulsar light at different frequencies, astronomers can map the distribution of ionized gas in the galaxy. And since this gas aligns with the galactic magnetic field, they can map the field.
We can even measure the magnetic field of a galaxy billions of light-years away. Recently the Atacama Large Millimeter/submillimeter Array (ALMA) measured the magnetic field of a galaxy so distant its light took 11 billion years to reach us. This galaxy is particularly dusty, so ALMA observed light reflected and emitted by this dust. This light is polarized along the orientation of the dust grains, and since dust grains tend to align along magnetic field lines, astronomers could use this to map the galaxy’s magnetic field. It is the most distant galaxy known to have a magnetic field.
Astronomers don’t always need to see something to know that it’s there. They just need to see the effect they have on things they can see. From dark matter and dark energy to black holes and magnetic fields, radio astronomy helps us bring these invisible things to light.
This news article was originally published on NRAO website on September 21, 2023.
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NSF VLA Contributes Crucial Puzzle Piece to ‘Peculiar’ High Energy Transient
High-energy transient signals are most often determined to be gamma-ray burst events, but the recently-launched Einstein Probe has expanded astronomers’ ability to quickly respond to similar signals occurring at X-ray wavelengths. Now, a multi-wavelength study of EP240408a concludes that while many of the signal’s characteristics might lead to the conclusion that it is a gamma-ray burst, the non-detection at radio wavelengths precludes that possibility.
Students Contribute to New Understanding of ‘Twinkling’ Pulsars
The flexible observing setup of the Green Bank Observatory’s 20-meter telescope enabled frequent, long-duration observations of eight pulsars, spanning two and a half years for a student-driven study carried out by students in the Pulsar Science Collaboratory program.
Double the Disks, Double the Discovery: New Insights into Planet Formation in DF Tau
Tucked away in a star-forming region in the Taurus constellation, a pair of circling stars are displaying some unexpected differences in the circumstellar disks of dust and gas that surround them. A new study led by researchers at Lowell Observatory, combining data from the Atacama Large Millimeter/submillimeter Array (ALMA) and Keck Observatory, has unveiled intriguing findings about planet formation in this binary star system, known as DF Tau, along with other systems in this region.