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From the time of its writing in the 2nd century CE, Claudius Ptolemy’s Almagest stood at the forefront of mathematical astronomy for nearly 1,500 years. This work included a catalog of 1,025 stars, listing their coordinates (in ecliptic longitude and latitude) and brightnesses. While astronomers within a few centuries realized that the models for the sun, moon, and planets all had issues (which we today recognize as being a result of them being incorrect, geocentric models relying on circles and epicycles instead of a heliocentric model with elliptical orbits), the catalog of stars was generally believed to be correct.

That was, until the end of the 16th century, when the renowned observation astronomer Tycho Brahe realized that there was a fundamental flaw with the catalog: the ecliptic longitudes were low by an average of 1 degree.

What’s more, Brahe proposed an explanation for why. He suggested that Ptolemy had stolen the data from the astronomer Hipparchus some 250 years earlier, and then incorrectly updated the coordinates.

The question of whether this was a cosmic coincidence or the oldest case of scientific plagiarism is a question that historians of astronomy have argued for over 400 years.

The Accusation

To understand why Brahe made this accusation, we must first understand the favored coordinate system of astronomers at the time: the ecliptic coordinate system.

The universe was simply different when it was younger. Recently astronomers have discovered that complex physics in the young cosmos may have led to the development of supermassive stars, each one weighing up to 100,000 times the mass of the Sun.

We currently have no observations of the formation of the first stars in the universe, which is thought to have taken place when our cosmos was only a few hundred million years old. To understand this important epoch, astronomers turn to sophisticated computer simulations to test out models of how the first stars formed.

Over the years astronomers have wrestled with the key question of what is the typical size of the first stars. Some early estimates predicted that the first stars could be hundreds of times more massive than the Sun, while later simulation suggested that they would be more normally sized. 

Recently a team of researchers have put together a new round of simulations and come to a very surprising conclusion. Their simulations specifically looked at a phenomenon known as cold accretion. To build large stars you have to pull a lot of material into a very small volume very quickly. And you have to do it without raising the temperature of the material, because warmer material will prevent itself from collapsing. So you need some method of removing heat from material as it collapses very quickly.

Earlier simulations had found the appearance of dense pockets within early galaxies that cool off rapidly from emitting radiation, but did not have the resolution needed to follow their further evolution. The new research takes it a step further by examining how the cold dense pockets that initially form in the early universe behave. 

The European Space Agency successfully tested a solar-sail-type device to speed up the deorbit time for a used cubesat carrier in Earth orbit.  The so-called breaking sail, the Drag Augmentation Deorbiting System (ADEO) was deployed from an ION satellite carrier in late December 2022. Engineers estimate the sail will reduce the time it takes for the carrier to reenter Earth’s atmosphere from 4-5 years to approximately 15 months.

The sail is one of many ideas and efforts to reduce space junk in Earth orbit.   

“We want to establish a zero debris policy, which means if you bring a spacecraft into orbit you have to remove it,” said Josef Aschbacher, ESA Director General.

Last year, China successfully deployed a similar sail from a Long March 2 rocket.

ESA says the sail provides a passive method of deorbiting by increasing the atmospheric surface drag effect and causing an accelerated decay in the satellite’s orbital altitude. “The satellite will eventually burn-up in the atmosphere, providing a quicker, residue-free method of disposal.”

The James Webb Space Telescope is back to full science operations. One of the telescope’s instruments, the Near Infrared Imager and Slitless Spectrograph (NIRISS) had been offline since January 15 due to a communications error. But engineers worked through the problem and were able to return the instrument to full operations. 

“NASA and CSA [Canadian Space Agency] partnered to approach the problem as technically possible, using a detailed consideration of all areas of operation of the instrument,” said Julie Van Campen, Webb Integrated Science Instrument Module (ISIM) systems engineer at NASA’s Goddard Space Flight Center, in a blog post update.

The instrument, built by CSA, was returned to full operations on January 31. The problem began when a communications delay within the science instrument caused its flight software to time out. Engineers determined the cause of the issue was a hit by a galactic cosmic ray, a form of high-energy radiation from outside our solar system that can sometimes disrupt electrical systems.

Van Campen said encountering cosmic rays is a normal and expected part of operating any spacecraft, and that this cosmic ray event affected logic in the solid-state circuitry of NIRISS electronics known as the Field Programmable Gate Array. JWST engineers determined that rebooting the instrument would bring it back to full functionality.

“They analyzed all possible methods to safely recover the electronics. When performing the operation, reviews were held at each intermediate step,” she said. “We are now happy to report that Webb’s NIRISS instrument is back online, and is performing optimally.”