Hubble constant Archives

November 14, 2024November 14, 2024 by Matt Williams

New Study Examines Cosmic Expansion, Leading to a New Drake Equation

An illustration of cosmic expansion. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab

In 1960, in preparation for the first SETI conference, Cornell astronomer Frank Drake formulated an equation to calculate the number of detectable extraterrestrial civilizations in our Milky Way. Rather than being a scientific principle, the equation was intended as a thought experiment that summarized the challenges SETI researchers faced. This became known as the Drake Equation, which remains foundational to the Search for Extraterrestrial Intelligence (SETI) to this day. Since then, astronomers and astrophysicists have proposed many updates and revisions for the equation.

This is motivated by ongoing research into the origins of life on Earth and the preconditions that led to its emergence. In a recent study, astrophysicists led by Durham University produced a new model for the emergence of life that focuses on the acceleration of the Universe’s expansion (aka. the Hubble Constant) and the number of stars formed. Since stars are essential to the emergence of life as we knot it, this model could be used to estimate the probability of intelligent life in our Universe and beyond (i.e., in a multiverse scenario).

October 18, 2024October 18, 2024 by Matt Williams

Check Out This Sneak Peek of the Euclid mission’s Cosmic Atlas

This mosaic made by ESA’s Euclid space telescopes constitutes about 1% of the wide survey that Euclid will capture during six years. Credit: ESA/Euclid/Euclid Consortium/NASA/CEA Paris-Saclay/J.-C. Cuillandre, E. Bertin, G. Anselmi

On July 1st, 2023 (Canada Day!), the ESA’s Euclid mission lifted off from Cape Canaveral, Florida, atop a SpaceX Falcon 9 rocket. As part of the ESA’s Cosmic Vision Programme, the purpose of this medium-class mission was to observe the “Dark Universe.” This will consist of observing billions of galaxies up to 10 billion light-years away to create the most extensive 3D map of the Universe ever created. This map will allow astronomers and cosmologists to trace the evolution of the cosmos, helping to resolve the mysteries of Dark Matter and Dark Energy.

The first images captured by Euclid were released by the ESA in November 2023 and May 2024, which provided a glimpse at their quality. On October 15th, 2024, the first piece of Euclid‘s great map of the Universe was revealed at the International Astronautical Congress (IAC) in Milan. This 208-gigapixel mosaic contains 260 observations made between March 25th and April 8th, 2024, and provides detailed imagery of millions of stars and galaxies. This mosaic accounts for just 1% of the wide survey that Euclid will cover over its six-year mission and provides a sneak peek at what the final map will look like.

October 3, 2024October 3, 2024 by Brian Koberlein

Gravitational Lens Confirms the Hubble Tension

Webb image showing the appearances of a lensed supernova. Credit: NASA, ESA, CSA, STScI

We’ve known the Universe is expanding for a long time. The first solid paper demonstrating cosmic expansion was published by Edwin Hubble in 1929, based on observations made by Vesto Slipher, Milton Humason, and Henrietta Leavitt. Because of this, the rate of cosmic expansion is known as the Hubble constant, or Hubble parameter, H₀. From this parameter, you can calculate things such as the age of the Universe since the Big Bang, so knowing the value of H₀ is central to our understanding of modern cosmology.

August 22, 2024August 22, 2024 by Evan Gough

Polaris, Earth’s North Star, Has A Surprisingly Spotted Surface

An artist's conception shows Polaris A with a close companion, known as Polaris Ab. Yet another companion star, Polaris B, can be seen as a speck in the background at right. Credit: STScI

Humanity’s been fortunate to have a star situated over Earth’s north pole. The star, known as Polaris, or the North Star, has guided many sailors safely to port. But Polaris is a fascinating star in its own right, not just because of its serendipitous position.

March 23, 2024March 23, 2024 by Scott Alan Johnston

Red Giants Offer a New Way to Measure Distance in the Universe

The Large Magellanic cloud. Credit: CTIO/NOIRLab/NSF/AURA/SMASH/D. Nidever (Montana State University) Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin.

For nearly three decades now, it’s been clear that the expansion of the Universe is speeding up. Some unknown quantity, dramatically dubbed ‘dark energy’, is pushing the Universe apart. But the rate at which the Universe’s expansion is increasing – called the Hubble Constant – hasn’t yet been nailed down to a single number.

Not for lack of trying.

March 15, 2024March 15, 2024 by Matt Williams

Webb Continues to Confirm That Universe is Behaving Strangely

Image of NGC 5468, a galaxy located about 130 million light-years from Earth, combines data from the Hubble and James Webb space telescopes. Credit: NASA/ESA/CSA/STScI/A. Riess (JHU/STScI)

Over a century ago, astronomers Edwin Hubble and Georges Lemaitre independently discovered that the Universe was expanding. Since then, scientists have attempted to measure the rate of expansion (known as the Hubble-Lemaitre Constant) to determine the origin, age, and ultimate fate of the Universe. This has proved very daunting, as ground-based telescopes yielded huge uncertainties, leading to age estimates of anywhere between 10 and 20 billion years! This disparity between these measurements, produced by different techniques, gave rise to what is known as the Hubble Tension.

It was hoped that the aptly named Hubble Space Telescope (launched in 1990) would resolve this tension by providing the deepest views of the Universe to date. After 34 years of continuous service, Hubble has managed to shrink the level of uncertainty but not eliminate it. This led some in the scientific community to suggest (as an Occam’s Razor solution) that Hubble‘s measurements were incorrect. But according to the latest data from the James Webb Space Telescope (JWST), Hubble’s successor, it appears that the venerable space telescope’s measurements were right all along.

December 21, 2023December 21, 2023 by Evan Gough

Webb Sees a Supernova Go Off in a Gravitationally Lensed Galaxy – for the Second Time

NASA’s James Webb Space Telescope has spotted a multiply-imaged supernova in a distant galaxy designated MRG-M0138. Image Credit: NASA, ESA, CSA, STScI, Justin Pierel (STScI) and Andrew Newman (Carnegie Institution for Science).

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.

December 8, 2023December 9, 2023 by Matt Williams

If Our Part of the Universe is Less Dense, Would That Explain the Hubble Tension?

Ten areas in the sky were selected as “deep fields” that the Dark Energy Camera imaged several times during the survey, providing a glimpse of distant galaxies and helping determine their 3D distribution in the cosmos. Credit: NSF/DES/NOIRLab/DOE/FNAL/AURA/University of Alaska Anchorage/

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.”

October 6, 2023October 6, 2023 by Matt Williams

Colliding Neutron Stars Could Help Measure the Expansion of the Universe

Artist's impression of two neutron stars colliding, known as a "kilonova" event. Credits: Elizabeth Wheatley (STScI)

According to some in the astrophysical community, there has been something of a “Crisis in Cosmology” in recent years. Though astronomers are all aware that the Universe is in a state of expansion, there has been some inconsistency when measuring the rate of it (aka. the Hubble Constant). This issue arises from the Cosmic Distance Ladder, where astronomers use different methods to measure relative distances over longer scales. This includes making local distance estimates using parallax measurements, nearby variable stars, and supernovae (“standard candles”).

They also conduct redshift measurements of the Cosmic Microwave Background (CMB), the relic radiation left over from the Big Bang, to determine cosmological distances. The discrepancy between these two methods is known as the “Hubble Tension,” and astronomers are eager to resolve it. In a recent study, an international team of astrophysicists from the Niels Bohr Institute suggested a novel method for measuring cosmic expansion. They argue that by observing colliding neutron stars (kilonovae), astronomers can relieve the tension and obtain consistent measurements of the Hubble Constant.

May 17, 2023May 17, 2023 by Brian Koberlein

Astronomers Have a New Way to Measure the Expansion of the Universe

Multiple observations of the Refsdal supernova. Credit: Kelly,et al

The cosmos is expanding at an ever-increasing rate. This cosmic acceleration is caused by dark energy, and it is a central aspect of the evolution of our universe. The rate of cosmic expansion can be expressed by a cosmological constant, commonly known as the Hubble constant, or Hubble parameter. But while astronomers generally agree this Hubble parameter exists, there is some disagreement as to its value.