Brian Koberlein, Author at Universe Today

December 11, 2024December 11, 2024 by Brian Koberlein

Tidal Steams of Interstellar Objects May Flow Through the Milky Way Like Braided Rivers

How tidal disruption can create a stream of interstellar objects. Credit: NAOC / Y. Zhang

We know that interstellar objects occasionally visit our solar system. So far, we have only discovered two interstellar objects (ISOs), but that’s mainly because we can only distinguish them from solar system bodies by their orbital motion, and that takes a series of observations over time. The two we have discovered, ?Oumuamua and Borisov, were only noticed because they had highly unusual orbits that moved through the inner solar system. But when sky survey telescopes such as the Vera Rubin Observatory come online, we will likely find new interstellar objects all the time. It’s estimated that several ISOs enter the solar system every year, and there could be hundreds of them passing by at any given time. But that raises an interesting question about how these objects arrive. Do they enter our solar system randomly from all directions, or do they appear in clusters a few at a time?

December 10, 2024December 10, 2024 by Brian Koberlein

High Velocity Clouds Comprise Less of the Milky Way’s Mass Than We Thought

Illustration of the stellar halo surrounding our Milky Way Galaxy. Credit: Melissa Weiss / Harvard & Smithsonian’s Center for Astrophysics

Sometimes in astronomy, a simple question has a difficult answer. One such question is this: what is the mass of our galaxy?

On Earth, we usually determine the mass of an object by placing it on a scale or balance. The weight of an object in Earth’s gravitational field lets us determine the mass. But we can’t put the Milky Way on a scale. Another difficulty with massing our galaxy is that there are two types of mass. There is the mass of dark matter that makes up most of the Milky Way’s mass, and there is all the regular matter like stars, planets, and us, which is known as baryonic matter.

December 9, 2024December 9, 2024 by Brian Koberlein

Do We Really Know What Becomes a Type Ia Supernova?

Illustration of a Type Ia supernova. Credit: Kiso Observatory, The University of Tokyo

Lots of things out in the Universe can cause a supernova, from the gravitational collapse of a massive star, to the collision of white dwarfs. But most of the supernovae we observe are in other galaxies, too distant for us to see the details of the process. So, instead, we categorize supernovae by observed characteristics such as the light curves of how they brighten and fade and the types of elements identified in their spectra. While this gives us some idea of the underlying cause, there are still things we don’t entirely understand. This is particularly true for one particular kind of supernova known as Type Ia.

December 8, 2024December 8, 2024 by Brian Koberlein

Observations by DESI Open the Door to Modified Gravity Models

The relations between various approaches of modified gravity. Credit: J. M. Ezquiaga and M. Zumalacárregui (2018)

The standard theory of cosmology is based upon four things: the structure of space and time, matter, dark matter, and dark energy. Of these, dark energy is the one we currently understand the least. Within the standard model, dark energy is part of the structure of space and time as described by general relativity. It is uniform throughout the cosmos and expressed as a parameter known as the cosmological constant. But initial observations from the Dark Energy Spectroscopic Instrument (DESI) suggest the rate of comic expansion may vary over time. If further observations reinforce this, it could open up cosmological models to alternatives to general relativity known as modified gravity.

December 5, 2024December 5, 2024 by Brian Koberlein

Cosmology is at a Crossroads, But New Instruments are Coming to Help

Illustration of the accelerating expansion of the universe. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab

Our understanding of the Universe is profound. Only a century ago, astronomers held a Great Debate to argue over whether our galaxy was an island universe, or whether nebulae such as Andromeda were galaxies in a much larger cosmos. Now we know that the Universe is billions of years old, ever expanding to billions of light-years across, and filled with not just stars and galaxies but with dark energy and cold dark matter. Astronomers summarize this understanding as the LCDM model, which is the standard model of cosmology. While the observational data we have strongly supports this model, it is not without its challenges.

December 4, 2024December 5, 2024 by Brian Koberlein

MeerKAT Confirms the Gravitational Wave Background of the Universe in Record Time

A MeerKAT antenna disk in front of an illustrated view of black holes and gravitational waves. Credit: Carl Knox, OzGrav, Swinburne University of Technology and South African Radio Astronomy Observatory

The Universe is a turbulent place. Stars are exploding, neutron stars collide, and supermassive black holes are merging. All of these things and many more create gravitational waves. As a result, the cosmos is filled with a rippling sea of gravitational vibrations. While we have been able to directly detect gravitational waves since 2016, gravitational wave astronomy is still in its infancy. We have only been able to observe the gravitational ripples of colliding stellar black holes. Even then, all we can really detect is the final gravitational chirp created in the last moments of merging.

December 4, 2024December 4, 2024 by Brian Koberlein

Maybe Venus Was Never Habitable

Earth and Venus. Why are they so different and what do the differences tell us about rocky exoplanet habitability? Image Credit: NASA

Although they are very different today, Venus, Earth, and Mars were very similar in their youth. All three were warm, with thick, water-rich atmospheres. But over time, Mars became a cold, dry planet with a thin atmosphere, and Venus became superheated, with a crushing, toxic sky. Only Earth became a warm ocean world teeming with life. But why?

December 3, 2024December 3, 2024 by Brian Koberlein

White Dwarfs Could Have Habitable Planets, Detectable by JWST

An Earth-sized remnant of a Sun-like star is ringed by dust and debris. Credit: NASA’s Goddard Space Flight Center/Scott Wiessinger

In a few billion years, our Sun will die. It will first enter a red giant stage, swelling in size to perhaps the orbit of Earth. Its outer layers will be cast off into space, while its core settles to become a white dwarf. Life on Earth will boil away, and our planet itself might be consumed by the Sun. White dwarfs are the fate of all midsize stars, and given the path of their demise, it seems reasonable to assume that any planets die with their sun. But the fate of white dwarf planets may not be lifeless after all.

December 2, 2024December 2, 2024 by Brian Koberlein

What's Inside Uranus and Neptune? A New Way to Find Out

Artist expoded view of an ice giant planet similar to Uranus and Neptune. Credit: @iammoteh/Quanta magazine

In our search for exoplanets, we’ve found that many of them fall into certain types or categories, such as Hot Jupiters, Super-Earths, and Ice Giants. While we don’t have any examples of the first two in our solar system, we do have two Ice Giants: Uranus and Neptune. They are mid-size gas planets formed in the cold outer regions of the solar system. Because of this, they are rich in water and other volatile compounds, and they are very different from large gas giants such as Jupiter. We still have a great deal to learn about these worlds, but what we’ve discovered so far has been surprising, such as the nature of their magnetic fields.

November 30, 2024November 30, 2024 by Brian Koberlein

Interstellar Objects Can't Hide From Vera Rubin

Artist impression of the interstellar comet 2I/Borisov as it travels through our solar system. Credit: NRAO/AUI/NSF, S. Dagnello

We have studied the skies for centuries, but we have only found two objects known to come from another star system. The first interstellar object to be confirmed was 1I/2017 U1, more commonly known as ?Oumuamua. It was discovered with the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) and stood out because of its large proper motion. Because ?Oumuamua swept through the inner solar system, it was relatively easy to distinguish. The second interstellar object, 2I/Borisov, stood out because it entered the inner solar system from well above the orbital plane. But while we have only discovered two alien visitors so far, astronomers think interstellar objects are common. It’s estimated that several of them visit our solar system each year, and there may be thousands within the orbit of Neptune on any given day. They just don’t stand out, so we don’t notice them. But that could soon change.