If Gravity Can Exist Without Mass, That Could Explain Dark Matter

Researchers are making progress mapping dark matter, but they don't know what it is. This is a 3D density map of dark matter in the local universe, with the Milky Way marked by an X. Dots are galaxies, and the arrows indicate the directions of motion derived from the reconstructed gravitational potential of dark matter. Image Credit: Hong et al., doi: 10.3847/1538-4357/abf040.

Dark Matter is Nature’s poltergeist. We can see its effects, but we can’t see it, and we don’t know what it is. It’s as if Nature is playing tricks on us, hiding most of its mass and confounding our efforts to determine what it is.

Continue reading “If Gravity Can Exist Without Mass, That Could Explain Dark Matter”

Primordial Black Holes Can Only Explain a Fraction of Dark Matter

This artist's illustration shows what primordial black holes might look like. In reality, the black holes would struggle to form accretion disks, as shown. Image Credit: NASA’s Goddard Space Flight Center

What is Dark Matter? That question is prominent in discussions about the nature of the Universe. There are many proposed explanations for dark matter, both within the Standard Model and outside of it.

One proposed component of dark matter is primordial black holes, created in the early Universe without a collapsing star as a progenitor.

Continue reading “Primordial Black Holes Can Only Explain a Fraction of Dark Matter”

The JWST is Re-Writing Astronomy Textbooks

The first JWST Deep Field Image, showing large distant galaxies. The telescope's observations are revealing the previously unseen and are forcing a re-write of astronomy textbooks. Image Credit: NASA, ESA, CSA, STScI

When the James Webb Space Telescope was launched at the end of 2021, we expected stunning images and illuminating scientific results. So far, the powerful space telescope has lived up to our expectations. The JWST has shown us things about the early Universe we never anticipated.

Some of those results are forcing a rewrite of astronomy textbooks.

Continue reading “The JWST is Re-Writing Astronomy Textbooks”

Some Clever Ways to Search for Primordial Black Holes

Primordial Black Holes (PBHs) have recently received much attention in the physics community. One of the primary reasons is the potential link to dark matter. In effect, if PBHs can be proven to exist, there’s a very good chance that they are what dark matter, the invisible thing that makes up 85% of the universe’s mass, is made of. If proven, that would surely be a Nobel-level discovery in astrophysics. 

Continue reading “Some Clever Ways to Search for Primordial Black Holes”

Roman Space Telescope Will Be Hunting For Primordial Black Holes

This artist's illustration shows what primordial black holes might look like. In reality, the black holes would struggle to form accretion disks, as shown. Image Credit: NASA’s Goddard Space Flight Center

When astrophysicists observe the cosmos, they see different types of black holes. They range from gargantuan supermassive black holes with billions of solar masses to difficult-to-find intermediate-mass black holes (IMBHs) all the way down to smaller stellar-mass black holes.

But there may be another class of these objects: primordial black holes (PBHs) that formed in the very early Universe. If they exist, the Nancy Grace Roman Space Telescope should be able to spot them.

Continue reading “Roman Space Telescope Will Be Hunting For Primordial Black Holes”

The World's Largest Digital Camera is Complete. It Will Go Into the Vera Rubin Observatory

Researchers examine the LSST Camera. The camera will soon be shipped to Chile, where it will be the heart of Vera C. Rubin Observatory (right). Credit: Vera C. Rubin Observatory/DOE/SLAC

The Vera C. Rubin Observatory, formerly the Large Synoptic Survey Telescope (LSST), was formally proposed in 2001 to create an astronomical facility that could conduct deep-sky surveys using the latest technology. This includes a wide-field reflecting telescope with an 8.4-meter (~27.5-foot) primary mirror that relies on a novel three-mirror design (the Simonyi Survey Telescope) and a 3.2-megapixel Charge-Coupled Device (CCD) imaging camera (the LSST Camera). Once complete, Rubin will perform a 10-year survey of the southern sky known as the Legacy Survey of Space and Time (LSST).

While construction on the observatory itself did not begin until 2015, work began on the telescope’s digital cameras and primary mirror much sooner (in 2004 and 2007, respectively). After two decades of work, scientists and engineers at the Department of Energy’s (DOE) SLAC National Accelerator Laboratory and their collaborators announced the completion of the LSST Camera – the largest digital camera ever constructed. Once mounted on the Simonyi Survey Telescope, this camera will help researchers observe our Universe in unprecedented detail.

Continue reading “The World's Largest Digital Camera is Complete. It Will Go Into the Vera Rubin Observatory”

A New, More Accurate Measurement for the Clumpiness of the Universe

Clusters of galaxies as observed by the eROSITA instrument. Colors indicate the redshift of the clusters, up to about 9 billion years of lookback time. Credit: MPE, J. Sanders for the eROSITA consortium.
Clusters of galaxies as observed by the eROSITA instrument. The idea is to determine the clumpiness (or distribution) of matter in the Universe. Colors indicate the redshift of the clusters, up to about 9 billion years of lookback time. Credit: MPE, J. Sanders for the eROSITA consortium.

Cosmologists are wrestling with an interesting question: how much clumpiness does the Universe have? There are competing but not compatible measurements of cosmic clumpiness and that introduces a “tension” between the differing measurements. It involves the amount and distribution of matter in the Universe. However, dark energy and neutrinos are also in the mix. Now, results from a recent large X-ray survey of galaxy clusters may help “ease the tension”.

Continue reading “A New, More Accurate Measurement for the Clumpiness of the Universe”

Euclid Begins its 6-Year Survey of the Dark Universe

The areas that the space telescope Euclid will observe. Credit: ESA/Euclid/Euclid Consortium

On July 1, 2023, the Euclid Spacecraft launched with a clear mission: to map the dark and distant Universe. To achieve that goal, over the next 6 years, Euclid will make 40,000 observations of the sky beyond the Milky Way. From this data astronomers will be able to map the positions of billions of galaxies, allowing astronomers to observe the effects of dark matter.

Continue reading “Euclid Begins its 6-Year Survey of the Dark Universe”

How Does the Cosmic Web Drive Galaxy Evolution?

A computer simulation of what gas and stars in a galaxy cluster look like, and how they look embedded in the cosmic web. The assembly of galaxy clusters has implications for the clumpiness of the Universe throughout time. Credit: Yannick Bahé.
A computer simulation of what gas and stars in a galaxy cluster look like, and how they look embedded in the cosmic web. The assembly of galaxy clusters has implications for the clumpiness of the Universe throughout time. Credit: Yannick Bahé.

Galaxies experience a long strange trip through the cosmic web as they grow and evolve. It turns out that the neighborhoods they spend time in on the journey change their evolution, and that affects their star formation activity and alters their gas content.

Continue reading “How Does the Cosmic Web Drive Galaxy Evolution?”

Dust Ruins Another Way of Measuring Distance in the Universe

A dusty spiral galaxy known as M66. Credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble

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”