Space News & Blog Articles

New Comet C/2023 A3 Tsuchinshan-ATLAS may put on a show at the end of next year.

Could this one be the next great comet? Though caution is always warranted when it comes to icy interlopers from the Oort Cloud, a recent discovery has given us pause, and a reason to take notice. We’re talking about the recent discovery of Comet C/2023 A3 Tsuchinshan-ATLAS, just announced last week.

The discovery announcement came out of CBAT (The Central Bureau for Astronomical Telegrams) Number 5228 released on February 28th. The comet was sighted independently by the ATLAS (Asteroid Terrestrial-impact Last Alert System) automated sky survey, and earlier data from the Tsuchinshan (Zijinshan or ‘Purple Mountain’) observatory in China, hence the double moniker. The comet turned up in earlier observations from Purple Mountain Observatory’s XuYi Station going back all the way to January 9th, 2023, that’s why it ended up with an A3 designation, which is usually reserved for comets discovered in early January.

The specifics for the comet are certainly interesting: the comet was discovered as a faint +19th magnitude fuzzball, and currently shines at +18th magnitude in the constellation Serpens Caput. Its current distance is 7.2 AU (670 million miles/1.08 billion kilometers) from the Sun, out beyond the orbit of Jupiter.

On an 80,660 year retrograde orbit with a 139 degree inclination relative to the ecliptic plane, the comet will reach perihelion on September 28th, 2024 at 0.39 AU from the Sun… though it will also only be 22 degrees as seen from the Earth, and lost in the Sun’s glare. Things get a bit better in the succeeding weeks, as the comet makes its closest Earth approach of 0.476 AU on October 13th. Best views are expected around this time as the comet emerges from the Sun’s glare low in the dawn sky, post perihelion. The comet may reach a brilliant magnitude 0, through +3 or so is more conservative. A phenomenon known as forward scattering may work in the comet’s favor, increasing its apparent brightness.

In the 1930s, astrophysicists theorized that at the end of their life cycle, particularly massive stars would collapse, leaving behind remnants of infinite mass and density. As a proposed resolution to Einstein’s field equations (for his Theory of General Relativity), these objects came to be known as “black holes” because nothing (even light) could escape them. By the 1960s, astronomers began to infer the existence of these objects based on the observable effects they have on neighboring objects and their surrounding environment.

Despite improvements in instruments and interferometry (which led to the first images of M87 and Sagittarius A*), the study of black holes still relies on indirect methods. In a recent study, a team of Japanese researchers identified an unusual cloud of gas that appears to have been elongated by a massive, compact object that it orbits. Since there are no massive stars in its vicinity, they theorize that the cloud (nicknamed the “Tadpole” because of its shape) orbits a black hole roughly 27,000 light-years away in the constellation Sagittarius.

The research team was led by Miyuki Kaneko, a School of Fundamental Science and Technology (SFST) at Keio University. He was joined by astrophysicists and engineers from the SFST, the Technology Institute of Science and Technology (Keio University), the National Astronomical Observatory of Japan (NAOJ), Kanagawa University, and the Center for AStronomy at Ibaraki University. The paper that describes their findings was recently published in The Astrophysical Journal.

Annotated map of the Milky Way Galaxy with the constellations that cross the galactic plane in each direction and the known most prominent components. Credit: Pablo Carlos Budassi

The team used data from the James Clerk Maxwell Telescope at the East Asian Observatory and the NAOJ’s Nobeyama 45-meter Radio Telescope to observe the Tadpole molecular gas cloud. They noted that the cloud is unique due to its characteristic head-tail structure, position, and velocity. Based on its kinematics and changes in line intensity along its orbit, the team determined that the best fit was a black hole. They were also able to constrain its mass, which they estimated to be 1 million times the mass of our Sun.

Black holes and neutron stars are among the odder denizens of the cosmic zoo. They’re both dense collections of matter and, except for supermassive black holes, are the end states of massive stars. Fundamentally, they’re two different types of objects that are detectable via the activity in the accretion disks that form around them. Astronomers recently observed an object that acted like a black hole but turned out to be a neutron star. The clues lay in the accretion disk surrounding it.

Where do accretion disks come from? And, why do they brighten up with flares and outbursts? In the case of binary systems, that material comes from companion stars that feed them as much (or more) than they can eat. The accretion disks respond in various ways, often forming hotspots and blasting out jets of radiation. Yet, in many respects, understanding some of the disk activities had to wait for extensive, multi-wavelength studies of their outbursts.

Monitoring Odd Behavior in an Accretion Disk

When astronomers first saw a weirdly bright object called J1858.6-0814, they first assumed it was a black hole with a companion star. It gave off a series of flares that extended across the electromagnetic spectrum, from radio to x-rays. After a lot of observations and head-scratching, the team members realized that this thing is a neutron star with a solid surface. There’s an accretion disk around it created by a companion star. The bright flares come from instability in that accretion disk and high-speed ejections of material away from the objects.

According to IAC researcher Federico Vincentelli, the lead scientist studying this object, the instabilities affect the behavior of the accretion disk around the neutron star. “Matter from the disk is launched within an outflow or a jet,” he said. “Some may still fall onto the black hole or neutron star. However, the exact fraction of matter which goes either way is still unknown. This dramatic process remains poorly understood and, until now, has only been observed in detail in a system in which the compact object is a black hole.”

Understanding X-ray Binary J1858.6-0814

X-ray binaries are basically pairs of objects—usually a black hole or a neutron star, plus a companion star—that are bright in x-rays. J1858.6-0814 is in a special class called a low-mass x-ray binary. Stars in such pairs have masses below around 1.5 solar masses. The neutron star has a mass somewhere between 10 and 25 solar masses. There’s a great deal of interactivity between the members as the star shares its material with its companion. When that happens at a neutron star, the material doesn’t fall straight onto the surface. It spirals around into the accretion disk. As it does, it undergoes friction heating, loses its potential energy, and eventually contributes to those instabilities Vincentelli describes.

Mars is a long way from Earth, making it challenging to communicate with. That difficult communication is becoming ever more important as we launch more and more craft to the Red Planet. It will become absolutely critical when we send actual people there. So what can be done to increase the speed of communications between our solar system’s blue and red planets? A paper from researchers primarily based in Spain looks at different networking topologies that could help solve some of the communication problems. 

Typically, communication with Mars is done through a system known as the Deep Space Network (DSN). Essentially, it is a set of giant ground-based communication satellites spread worldwide. Their primary purpose is to communicate directly with every probe launched beyond Earth’s orbit, including those surrounding Mars. Some systems on the ground on Mars also use satellites in orbit around the planet, such as the Mars Reconnaissance Orbiter (MRO), which then broadcasts those signals to the DSN.

There are several problems with this configuration, including the single point of failure, and size of the equipment needed to send signals back, and the fact that the Sun interrupts communications for a significant chunk of the time. If one of the DSN satellites goes down, or, worse yet, MRO stops operating, communications to most of the scientific equipment on the Red planet could get much dicier. Network engineers on Earth build in redundancy paths specifically to avoid this single point of failure problem.

Some signals do lose their strength, even without the presence of an atmosphere in space, so to effectively send high-speed information over long distances, the antennas on these craft have to be massive. Sometimes they exceed the size of the fairing they are launched in, though there are techniques to unpack an antenna in space itself. But an even more significant communication challenge is the Sun.

It might not seem like it, but about 30% of the time, Earth cannot communicate with Mars directly. This is mainly because they are on opposite sides of the Sun from one another – or nearly so, anyway. The radiation blasts off of our local star scrambles most, if not all, communications, making talking to missions like Spirit and Perseverance near impossible when the planets are thus aligned.