Lifeboat Foundation

The Dark Energy Spectroscopic Instrument (DESI) is a robotic instrument and spectrograph mounted on the Mayall Telescope in Kitt Peak, Arizona. The DESI collaboration aims primarily to understand the elusive Dark Energy. This is an energy of unknown source causing the Universe to accelerate in its expansion; this accelerating expansion is not predicted to occur for a universe that is filled with just ordinary matter and radiation (some more detail can be seen in this Astrobite). Since we still know so little about Dark Energy, a large galaxy survey can allow us to explore the history of the expansion of the Universe in more detail. The DESI instrument has 5,000 individual optical fibres controlled by robots that allow it to measure individual spectra of up to 5,000 galaxies in just a mere 20 minutes! Due to this design, and an observing program that optimises targets in the sky based on observing conditions, the survey will measure spectra of up to 35 million galaxies over 5 years. This will allow DESI to perform precise cosmological measurements, as a great volume of space and number of galaxies can be probed, and noise in the data products is reduced. This bite looks at the cosmology results from the collaboration’s analysis of the recently released Year 1 Data (YR1), in particular, via a signal that can be seen in the data known as Baryon Acoustic Oscillations.

DESI tracers

Continue reading “Results from the DESI (Dark Energy Spectroscopic Instrument) YR1 Data Release: a summary” »

A potentially controversial new study suggests that the universe’s expansion may be a mirage.

This new perspective on the universe may also provide answers to the mysteries surrounding dark energy and dark matter, which scientists estimate make up about 95% of all the energy and matter in the universe but are still poorly understood.

The accelerated expansion of the present universe, believed to be driven by a mysterious dark energy, is one of the greatest puzzles in our understanding of the cosmos. The standard model of cosmology called Lambda-CDM, explains this expansion as a cosmological constant in Einstein’s field equations. However, the cosmological constant itself lacks a complete theoretical understanding, particularly regarding its very small positive value.

It’s now thought that they could illuminate fundamental questions in physics, settle questions about Einstein’s theories, and even help explain the universe.

What makes PSR J1748–2446 famous for its weirdness? Easy. It is the celestial object that spins the fastest in the universe. It’s also a star whose surface is not just solid, but harder than a diamond. Compared to lead, its density is 50 trillion times higher. Compared to our Sun, its magnetic field sizzles a trillion times more intensely. It is, in essence, the most extreme form of neutron star.

When a heavy sun explodes in a supernova, the core of the sun, which has the mass of several million Earths, collapses into a tiny sphere and the rest of the sun shoots outward. This is how neutron stars are created. When this occurs, the inverse-square law of gravity goes into its demo-mode with a vengeance.

They calculated stellar populations without and with the presence of dark matter. With dark matter, more massive stars experienced a lower dark matter density, and hydrogen in their core fused more slowly and their evolution was slowed down. But stars in a higher dark matter density region were changed significantly—they maintained equilibrium through dark matter burning with less fusion or no fusion, which led to a new stellar population in an HR region above the main sequence.

“Our simulations show that stars can survive on dark matter as a fuel alone,” said lead co-author Isabelle John from Stockholm University, “and because there is an extremely large amount of dark matter near the Galactic Center, these stars become immortal,” staying forever young, occupying a new, distinct, observable region of the HR diagram.

Their dark matter model may be able to explain more of the known mysteries. “For lighter stars, we see in our simulations that they become very puffy and might even lose parts of their outer layers,” said John. She noted that “something similar to this might be observed at the Galactic Center: the so-called G-objects, which might be star-like, but with a gas cloud around them.”

By studying the geometry of model space-times, researchers offer alternative views of the universe’s first moments.

🌌🔭 The Chandra X-ray Observatory has been unveiling the mysteries of the universe for 25 years! Discover how its X-ray data helps scientists study black holes, supernovae, and the formation of galaxies. Learn about the incredible insights gained and what the future holds for X-ray astronomy. #SpaceResearch #BlackHoles #Chandra

NASA’s Chandra X-ray Observatory detects X-ray emissions from astronomical events.

Transferring information from one location to another without transmitting any particles or energy seems to run counter to everything we’ve learned in the history of physics.

Yet there is some solid reasoning that this ‘counterfactual communication’ might not only be plausible, but depending on how it works could reveal fundamental aspects of reality that have so far been hidden from view.

Counterfactual physics isn’t a new thing in itself, describing a way of deducing activity by an absence of something. In one sense, it’s pretty straight forward. If your dog barks at strangers, and you hear silence when the front door opens, you’ve received information that says a familiar person has entered your house in spite of the absence of sound.