Space News & Blog Articles

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

Space exploration is driven by technology – sometimes literally in the case of propulsion technologies.  Solar sails are one of those propulsion technologies that has been getting a lot of attention lately.  They have some obvious advantages, such as not requiring fuel, and their ability to last almost indefinitely.  But they have some disadvantages too, not the least of which is how difficult they are to deploy in space.  Now, a team from NASA’s Langley Research Center has developed a novel time of composite boom that they believe can help solve that weakness of solar sails, and they have a technology demonstration mission coming up next year to prove it.

The mission, known as the “Advanced Composite Solar Sail System” (ACS3) mission is designed around a 12U CubeSat, which measures in at a tiny 23cm x 23 cm x 34 cm (9 in x 9 in x 13 in). The solar sail it hopes to deploy will come in at almost 200 square meters (527 sq ft), and both it and its composite booms will fit inside the CubeSat enclosure, which is not much larger than a toaster oven.

The booms themselves are made out of a novel composite that is 75% lighter than previous deployable booms, while also suffering from only 1% of the thermal distortion that previous metallic booms were subjected to.  They also conveniently roll into a 18 cm (7”) diameter spool that can be easily stored and easily deployed once the CubeSat is in space.

Its deployment mechanism still requires power, however, so the ACS3 mission will use a small solar panel to collect enough power to enable that deployment. But once it is fully unfurled, the mission will switch to a technology demonstration of actually adjusting the CubeSat’s orbit using only solar radiation pressure – the driving force of solar sails.

Solar sails themselves are only as effective as their size allows them to be – larger sizes means more radiation pressure and faster acceleration.  Therefore, the team behind the composite booms are also developing a larger boom system that would allow them to deploy solar sails that will come in at a whopping half an acre (2,000 sq meters).  Its spools would need to be slightly longer, but the cost to benefit ratio is huge.

Planet formation is notoriously difficult to study.  Not only does the process take millions of years, making it impossible to observe in real time, there are myriad factors that play into it, making it difficult to distinguish cause and effect.  What we do know is that planets form from features known as protoplanetary disks, which are made up of gas and dust surrounding young stars.  And now a team using ALMA have found a star system that has a protoplanetary disk and enough variability to help them nail down some details of how exactly the process of planet formation works.

The research is described in two new papers in The Astrophysical Journal.  They describe the star system Elias 2-27, which is located about 400 light years from Earth in Ophiuchus, the Serpent Bearer.  It has attracted the attention of astronomers for the last 5 years, first being studied in 2016 when it revealed a pinwheel of dust surrounding the star.

Usually protoplanetary disks don’t take the shape of a pinwheel, which is more commonly found in galactic formations such as the Pinwheel Galaxy.  Researchers speculated that the two pinwheel arms visible around the star were caused by gravitational instabilities, which could also contribute to planetary formation processes.  But they needed further data to prove their idea.

That is where the new papers come in.  Data that was collected over the last 5 years proved the existence of gravitational instabilities, but also found a few things that weren’t caught in the first round of data.  It appears there may have been more material accreting to the disk itself, causing more gravitational chaos. More surprisingly, some parts of the protoplanetary disk were much taller than others.

This type of “vertical asymmetry” had never been observed before in a protoplanetary disk, and allowed the researchers to take a step forward in one of the computational hurdles that block the path to fully understanding planetary formation.  Computational members of the team had predicted that gravitational instabilities might cause the huge pillars of matter that appear to tower over the disk.  Those towers also open up the possibility of calculating the actual quantity of material present in the disk itself – a measurement that has eluded planetary scientists so far.