Brian Koberlein, Author at Universe Today

January 8, 2025January 8, 2025 by Brian Koberlein

Astronomers are Losing the Night Sky (and Radio Sky) to Satellite Megaconstellations

How constellation satellites can create light pollution for radio telescopes. Credit: IAU CPS/NOIRLab/SKAO

When was the last time you looked up into the night sky and saw the Milky Way? If you happen to live in one of the truly remote areas of the world, your answer might be “last night.” If you live in one of the generally “rural” areas of your country, you might remember how you used to see the Milky Way regularly, but the rise of LEDs, particularly the blue/white ones, has gradually erased the Milky Way from your nights. For the large majority of humans on our small world, the answer is “never.”

January 6, 2025January 6, 2025 by Brian Koberlein

A Dragon Reveals Individual Stars From A Time When the Universe Was Half Its Present Age

The galactic cluster Abell 370, with the Dragon Arc highlighted. Credit: NASA, ESA, the Hubble SM4 ERO Team and ST-ECF

One powerful way to study the galaxies is to study individual stars. By looking at the ages, types, and distribution of stars in the Milky Way, we’ve captured a detailed snapshot of how our galaxy formed and evolved. The only problem with this approach is that we can only do this for a handful of galaxies. Even with the most powerful telescopes, we can only see individual stars in the Milky Way and nearby galaxies such as Andromeda. For galaxies billions of light years away, individual stars blur together, and the best we can do is observe the overall spectra of galaxies, not individual stars. But thanks to a chance alignment, we can now observe dozens of stars in a galaxy so distant we see it at a time when the Universe was half its present age.

January 3, 2025January 3, 2025 by Brian Koberlein

This Fast Radio Burst Definitely Came From a Neutron Star

An artist's impression of the origin of FRB 20221022A. Credit: Daniel Liévano

Fast radio bursts (FRBs) are notoriously difficult to study. They are flashes of radio light that can outshine a galaxy but often last for only a fraction of a second. For years, all we could do was observe them by random chance and wonder about their origins. Now, thanks to wide-field radio telescopes such as CHIME, we have some general understanding as to their cause. They seem to originate from highly magnetic neutron stars known as magnetars, but the details are still a matter of some debate. Now a team has used a method known as scintillation to reveal more clues about this mysterious phenomenon.

January 2, 2025January 2, 2025 by Brian Koberlein

Could Habitable White Dwarf Planets Retain Their Oceans? Maybe.

An artist’s impression of the white dwarf star WD1054–226 orbited by clouds of planetary debris and a major planet in the habitable zone. Credit Mark A. Garlick / markgarlick.com Licence type Attribution (CC BY 4.0)

Potentially habitable exoplanets are so incredibly common that astronomers have started to consider more unusual situations where life might arise. Perhaps life can be found on the moon of a hot Jupiter or lingering in the warm ocean of a rogue planet. Recently, there has even been the idea that habitable worlds might orbit white dwarfs. We know some white dwarfs have planets, and despite lacking nuclear fusion, white dwarfs do emit enough light and heat to have a habitable zone. But the question remains whether a planet could retain a water-rich environment through the red giant stage of a star before it becomes a white dwarf. This is the focus of a new study on the arXiv.

January 2, 2025January 2, 2025 by Brian Koberlein

The Webb Captures Spectra of Trans-Neptunian Objects, and Reveals a History of Our Solar System

Artistic representation of the distribution of trans-Neptunian objects in the planetesimal disk, with overlaid representative spectra of each compositional group highlighting the dominant molecules on their surfaces. Credit: William D. González Sierra/Florida Space Institute, University of Central Florida

Trans-Neptunian Objects (TNOs) are small planetoids that orbit the Sun beyond Neptune and Pluto. Their dark and icy character contains the remnant of the early solar system, and as such, they have the potential to reveal its history. But since they are small, distant, and dim, TNOs are very difficult to study. We know that different groups of TNOs have unique histories based on their surface colors and orbits. A new study has looked at their spectra, and it reveals a rich diversity unseen before now.

January 1, 2025January 1, 2025 by Brian Koberlein

New Study of Supernovae Data Suggests That Dark Energy is an Illusion

The evolution of the Universe as we know it. Credit: NASA

Dark energy is central to our modern understanding of cosmology. In the standard model, dark energy is what drives the expansion of the Universe. In general relativity, it’s described by a cosmological constant, making dark energy part of the structure of space and time. But as we’ve gathered more observational evidence, there are a few problems with our model. For one, the rate of cosmic expansion we observe depends on the observational method we use, known as the Hubble tension problem. For another, while we assume dark energy is uniform throughout the cosmos, there are some hints suggesting that might not be true. Now a new study argues we’ve got the whole thing wrong. Dark energy, the authors argue, doesn’t exist.

December 26, 2024December 26, 2024 by Brian Koberlein

Neutron Stars With Less Mass Than A White Dwarf Might Exist, and LIGO and Virgo Could Find Them

Illustration of a neutron star. Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA/GESTAR)

Most of the neutron stars we know of have a mass between 1.4 and 2.0 Suns. The upper limit makes sense, since, beyond about two solar masses, a neutron star would collapse to become a black hole. The lower limit also makes sense given the mass of white dwarfs. While neutron stars defy gravitational collapse thanks to the pressure between neutrons, white dwarfs defy gravity thanks to electron pressure. As first discovered by Subrahmanyan Chandrasekhar in 1930, white dwarfs can only support themselves up to what is now known as the Chandrasekhar Limit, or 1.4 solar masses. So it’s easy to assume that a neutron star must have at least that much mass. Otherwise, collapse would stop at a white dwarf. But that isn’t necessarily true.

December 23, 2024December 23, 2024 by Brian Koberlein

How Did Black Holes Grow So Quickly? The Jets

Artist’s impression of a bright, very early active galactic nucleus. Credit: NSF/AUI/NSF NRAO/B. Saxton

Within nearly every galaxy is a supermassive black hole. The beast at the heart of our galaxy contains the mass of millions of suns, while some of the largest supermassive black holes can be more than a billion solar masses. For years, it was thought that these black holes grew in mass over time, only reaching their current size after a billion years or more. But observations from the Webb telescope show that even the youngest galaxies contain massive black holes. So how could supermassive black holes grow so large so quickly? The key to the answer could be the powerful jets black holes can produce.

December 19, 2024December 19, 2024 by Brian Koberlein

Building the Black Hole Family Tree

Illustration of how black hole mergers might reveal their ancestors. Credit: Instituto Galego de Física de Altas Enerxías, IGFAE

In 2019, astronomers observed an unusual gravitational chirp. Known as GW190521, it was the last scream of gravitational waves as a black hole of 66 solar masses merged with a black hole of 85 solar masses to become a 142 solar mass black hole. The data were consistent with all the other black hole mergers we’ve observed. There was just one problem: an 85 solar mass black hole shouldn’t exist.

December 19, 2024December 19, 2024 by Brian Koberlein

A Binary Star Found Surprisingly Close to the Milky Way's Supermassive Black Hole

The newly discovered binary star D9, which is orbiting Sagittarius A*, the supermassive black hole at the centre of our galaxy. Credit: ESO/F. Peißker et al., S. Guisard

Binary stars are common throughout the galaxy. Roughly half the stars in the Milky Way are part of a binary or multiple system, so we would expect to find them almost everywhere. However, one place we wouldn’t expect to find a binary is at the center of the galaxy, close to the supermassive black hole Sagittarius A*. And yet, that is precisely where astronomers have recently found one.