Space News & Blog Articles

The standard model of cosmology is known as the LCDM model. Here, CDM stands for Cold Dark Matter, which makes up most of the matter in the universe, and L stands for Lambda, which is the symbol used in general relativity to represent dark energy or cosmic expansion. While the observational evidence we have largely supports the LCDM model, there are some issues with it. One of the most bothersome is known as cosmic tension.

It centers on our measurement of the Hubble constant, which tells us the rate at which the universe has expanded over time. There are lots of ways to measure the Hubble constant, from the brightness of distant supernovae, to the clustering of galaxies, to fluctuations in the cosmic background, to the light of microwave lasers. All of these methods have advantages and disadvantages, but if our cosmological model is right they should all agree within the limits of uncertainty.

The problem is, they don’t agree. Back in the early days of cosmology the uncertainty of our measurement was so large that all these results overlapped, but as our measurements got better it became clear different methods gave slightly different values for the Hubble constant. In polite company, astronomers say there is tension between these values.

This tension means that either our measurements are a bit off, or there is something wrong with our model. This has led some astronomers to propose some missing aspects to our model, such as how the mass of neutrinos might realign our Hubble values. But as new measurements of the Hubble constant keep coming in, it looks as if the tension is just getting worse. Now a new paper from Wendy Freedman argues that the tension problem isn’t that bad and that the tension will likely fade as the next generation of telescopes gives us even better data.

As it stands, the main tension in Hubble values arises between methods that rely upon the cosmic distance ladder, such as supernova observations, and those that don’t, such as the cosmic microwave background (CMB).

Sometimes simple and elegant solutions are all that is needed to solve a problem.  One problem that was searching for a solution was how to track microplastics.  These small particles of plastics are what results after the sun and friction (such as ocean waves) break down larger plastic objects.  They have become a huge problem in the ocean, wreaking havoc on ecosystems and their constituent organisms.  Now, a team from the University of Michigan have used data originally collected to monitor hurricanes to try to track microplastics, potentially helping to reign in a problem that threatens to engulf the world’s oceans.

The data the team used was collected by NASA’s Cyclone Global Navigation Satellite System (CYGNSS).  CYGNSS is a constellation of 8 microsatellites that launched in 2016 and normally monitors weather and ocean patterns to keep track of hurricanes.  Specifically they were interested in data collected on ocean roughness – or how choppy the ocean is.  Though placid oceans are not caused by only a single factor, one factor that contributes to it is the amount of debris in the ocean at a given location.

Much of that debris is made up of microplastics.  So the researchers theorized that calmer water would result from high concentrations of microplastics.  To find the calming effect of those microplastics though, they first had to control for another factor impacting choppiness – wind speed.  Luckily, CYGNSS also has data on wind speeds at the same locations it collected data on ocean roughness.  

With proper controls in place, the researchers then compared areas of calm seas with the areas of concentrated microplastics, as predicted by models. They matched up particularly well, lending credence to the idea that microplastics could be tracked via remote sensing of ocean roughness.

Example of microplastics captured in the Atlantic Ocean.
Credit – Nichole Trenholm / Ocean Research Project

Certain parts of the galaxy are more magical than others.  There are barren wastelands where barely a particle strays through occasionally, and there are fantastical nebulae that can literally light up the sky.  But beyond their good looks, those nebulae hold secrets to understanding some of the most important features of any galaxy – stars. Now, for the first time, a team from the University of Maryland managed to capture a high resolution image of one of the most active star-forming regions in our part of the galaxy.  Data from that image are not only spectacular, but can illuminate the details of the star formation process.

The instrument the team used to collect the most important parts of the data, known as SOFIA, is an amazing air-based telescopes.  Strapped to a modified 747 chassis, it specializes in capturing infrared images, just slightly out of the wavelengths that the human eye can see.  SOFIA turned its eye on a star forming region known as Westerlund 2, which is located in the RCW 49 nebula.  But the researchers didn’t stop there, using data collected in every wavelength from x-rays down to radio waves via different instruments.

Hubble image of a starforming nebula with the 747 housing SOFIA in the foreground.
Credit – Marc Pound / UMD

Luckily there was plenty of data to choose from.  That region of space had been the focus of previous studies, which hinted that there might be two bubbles of warm gas surrounding the region.  These types of gas bubbles have long been thought to play a role in star formation. Data from SOFIA definitively showed that there was in fact only one bubble, and that bubble is expanding.  The most likely cause of that expansion is a stellar wind launched by the formation of a massive star somewhere within the bubble itself.  

Gas bubbles aren’t the only material surrounding these formation regions though.  They’re joined by a “shell” made up of a form of ionized carbon.  Seen in the kaleidoscope of wavelengths the researchers analyzed, the shell and the gas bubbles intermingle with each other, but separating out individual wavelengths allowed for much higher resolution pictures of the bubbles (which were invisible in previous radio and sub-millimeter data) and shell (which glowed in a far-infrared band that SOFIA was able to collect).  

In Australia and South Africa, there are a series of radio telescopes that will be soon joined by a number of newly-constructed facilities to form the Square Kilometer Array (SKA). Once established, the SKA will have a collecting area that measures a million square meters (close to 2 million square yards). It will also be 50 times more sensitive than any radio telescope currently in operation, and be able to conduct surveys ten thousand times faster.

During a historic meeting that took place on June 29th, 2021, the member states that make up the SKAO Council voted to commence construction. By the late 2020s, when it’s expected to gather its first light, the array will consist of thousands of dishes and up to a million low-frequency antennas. These will enable it to conduct all kinds of scientific operations, from scanning the earliest periods in the Universe to searching for extraterrestrial intelligence (SETI).

At its core, the SKA relies on a process known as interferometry, where light from cosmic sources is gathered by multiple telescopes and then combined to create high-resolution images. For radio telescopes, this technique has the added advantage of allowing for observations where only a subset of the full array is available. With such a large collecting area, the SKA will allow for all kinds of revolutionary science.

A Huge Effort

The SKA consists of four “precursor facilities,” which include the MeerKAT and the Hydrogen Epoch of Reionization Array (HERA) in South Africa, and the Australian SKA Pathfinder (ASKAP) and Murchison Widefield Array (MWA) in Australia. Beyond these, there are also the “pathfinder” facilities located outside of these two countries, consisting of the Allen Telescope Array in northern California and the Low-Frequency Array (LOFAR) in the Netherlands.

These facilities are divided into two networks designated SKA-Low and SKA-Mid, which describe the radio frequency range they will cover. The decision to approve construction comes on the heels of two major developmental milestones for the SKAO. First, there was the publication of two key documents last year, the Observatory’s Construction Proposal and Observatory Establishment and Delivery Plan, and an executive summary of both.

One of the hardest things to reconcile in science is when new data either complicates or refutes previously findings.  It’s even more difficult when those findings were widely publicized and heralded around the community.  But that is how science works – the theories must fit the data.  So when a team from JPL analyzed data from Mars Express about the Martian South Pole, they realized the findings announced in 2018 about subsurface lakes on Mars might have been more fraught than they had originally thought.

That original discovery was announced after scientists found particularly bright spots in radar signals under the surface that were interpreted as being from liquid water.  Located in the region called the “South Polar Layered Deposits”, layers of water, dry ice, and dust have been intermixed over millions of years as Mars’ axial tilt changed. In lower layers, temperatures were high enough that sufficiently salty water could potentially be liquid.

When looking over data from the entirety of the Martian south pole, the JPL scientists noticed the same highly reflective surface in dozens of additional places under the surface.   Some appeared to be within 1.6 km (1 mile) of the surface.  Unfortunately, that also means the temperature would be a chilly -63 C (-81 F). Even with a massive amount of perchlorates (a special kind of salt prevalent on Mars), water would still be frozen at those temperatures.

First, the investigators, Jeffrey Plaut and Aditya Khuller from JPL (Khuller is now at ASU), tried to think of other potential heat sources that could increase the temperature in the areas they saw the highly reflective features.  An obvious candidate would be volcanism, which is potentially responsible for undersea oceans on other worlds in the solar system.  However, there is no other evidence of active volcanism at the south pole, so the researchers ruled it out as a heat source.

Visualization from the original 2018 study showing the reflected radar signals that were interpreted as lakes.
Credit –  Context map: NASA/Viking; THEMIS background: NASA/JPL-Caltech/Arizona State University; MARSIS data: ESA/NASA/JPL/ASI/Univ. Rome; R. Orosei et al 2018