Astronomers have many ways to measure the distance to galaxies billions of light years away, but most of them rely upon standard candles. These are astrophysical processes that have a brightness we can calibrate, such as Cepheid variable stars or Type Ia supernovae. Of course, all of these standard candles have some inherent variability, so astronomers also look for where our assumptions about them can lead us astray. As a case in point, a recent study in The Astrophysical Journal shows how galactic dust can bias distance observations.
Continue reading “Dust Ruins Another Way of Measuring Distance in the Universe”The JWST Solves the Mystery of Ancient Light
The very early Universe was a dark place. It was packed with light-blocking hydrogen and not much else. Only when the first stars switched on and began illuminating their surroundings with UV radiation did light begin its reign. That occurred during the Epoch of Reionization.
But before the Universe became well-lit, a specific and mysterious type of light pierced the darkness: Lyman-alpha emissions.
Continue reading “The JWST Solves the Mystery of Ancient Light”Astronomers Rule Out One Explanation for the Hubble Tension
Perhaps the greatest and most frustrating mystery in cosmology is the Hubble tension problem. Put simply, all the observational evidence we have points to a Universe that began in a hot, dense state, and then expanded at an ever-increasing rate to become the Universe we see today. Every measurement of that expansion agrees with this, but where they don’t agree is on what that rate exactly is. We can measure expansion in lots of different ways, and while they are in the same general ballpark, their uncertainties are so small now that they don’t overlap. There is no value for the Hubble parameter that falls within the uncertainty of all measurements, hence the problem.
Continue reading “Astronomers Rule Out One Explanation for the Hubble Tension”1,500 New Type 1A Supernova Found as Part of the Dark Energy Survey
Supernova explosions are fascinating because they’re so cataclysmic, powerful, and awe-inspiring. They’re Nature’s summer blockbusters. Humans have recorded their existence in ancient astronomical records and stone carvings, and in our age, with telescopes.
Now, the Dark Energy Survey (DES) has uncovered the largest number of Type 1A supernovae ever found with a single telescope.
Continue reading “1,500 New Type 1A Supernova Found as Part of the Dark Energy Survey”Webb Sees a Supernova Go Off in a Gravitationally Lensed Galaxy – for the Second Time
Nature, in its infinite inventiveness, provides natural astronomical lenses that allow us to see objects beyond the normal reach of our telescopes. They’re called gravitational lenses, and a few years ago, the Hubble Space Telescope took advantage of one of them to spot a supernova explosion in a distant galaxy.
Now, the JWST has taken advantage of the same lens and found another supernova in the same galaxy.
Continue reading “Webb Sees a Supernova Go Off in a Gravitationally Lensed Galaxy – for the Second Time”Why Was it Tricky to Know the Distances to Galaxies JWST Was Seeing?
One of the chief objectives of the James Webb Space Telescope (JWST) is to study the formation and evolution of the earliest galaxies in the Universe, which emerged more than 13 billion years ago. To this end, scientists must identify galaxies from different cosmological epochs to explore how their properties have changed over time. This, in turn, requires precise dating techniques so astronomers are able to determine when (in the history of the Universe) an observed galaxy existed. The key is to measure the object’s redshift, which indicates how long its light has been traveling through space.
This is the purpose of the Cosmic Evolution Early Release Science Survey (CEERS), a collaborative research group that analyzes Webb data to learn more about galactic evolution. These galaxies are known as “high-redshift,” meaning that their light emissions are redshifted all the way into the infrared spectrum. Galaxies that existed ca. 13 billion years ago can only be observed in the near-infrared spectrum, which is now possible thanks to Webb’s Near-Infrared Camera (NIRCam). Even so, obtaining accurate redshift measurements from such distant galaxies is a very tricky, and requires advanced techniques.
Continue reading “Why Was it Tricky to Know the Distances to Galaxies JWST Was Seeing?”If Our Part of the Universe is Less Dense, Would That Explain the Hubble Tension?
In the 1920s, Edwin Hubble and Georges Lemaitre made a startling discovery that forever changed our perception of the Universe. Upon observing galaxies beyond the Milky Way and measuring their spectra, they determined that the Universe was expanding. By the 1990s, with the help of the Hubble Space Telescope, scientists took the deepest images of the Universe to date and made another startling discovery: the rate of expansion is speeding up! This parameter, denoted by Lambda, is integral to the accepted model of cosmology, known as the Lambda Cold Dark Matter (LCDM) model.
Since then, attempts to measure distances have produced a discrepancy known as the “Hubble Tension.” While it was hoped that the James Webb Space Telescope (JWST) would resolve this “crisis in cosmology,” its observations have only deepened the mystery. This has led to several proposed resolutions, including the idea that there was an “Early Dark Energy” shortly after the Big Bang. In a recent paper, an international team of astrophysicists proposed a new solution based on an alternate theory of gravity that states that our galaxy is in the center of an “under-density.”
Continue reading “If Our Part of the Universe is Less Dense, Would That Explain the Hubble Tension?”The Early Universe Had No Problem Making Barred Spiral Galaxies
Spiral galaxies like the Milky Way are like cosmic snowflakes—no two are exactly alike. For many years, astronomers thought spirals couldn’t exist until the universe was about half its present age. Now, a newly discovered galaxy in the early Universe is challenging that idea.
Continue reading “The Early Universe Had No Problem Making Barred Spiral Galaxies”There Aren’t Many Galaxies Like The Milky Way Nearby. Now We Know Why
The Milky Way is a barred spiral galaxy, maybe even a grand design spiral galaxy. We can’t be sure from our vantage point. But one thing is certain: there aren’t many disk galaxies like it in our part of the Universe called the supergalactic plane.
Continue reading “There Aren’t Many Galaxies Like The Milky Way Nearby. Now We Know Why”If You Account for the Laniakea Supercluster, The Hubble Tension Might Be Even Larger
One of the great unsolved mysteries of cosmology is known as the Hubble tension. It stems from our inability to pin down the precise rate of cosmic expansion. There are several ways to calculate this expansion, from observing distant supernovae to measuring the Doppler shift of maser light near supermassive black holes, and they all give slightly different results. Maybe we don’t fully understand the structure of the Universe, or maybe our view of the heavens is biased given that we are located deep within a galactic supercluster. As a new study shows, the bias problem is even worse than we thought.
Continue reading “If You Account for the Laniakea Supercluster, The Hubble Tension Might Be Even Larger”