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The Sun isn’t the only star in this galactic neighbourhood. Other stars also call this neighbourhood home. But what’s the neighbourhood’s history? What triggered the birth of all those stars?

A team of astronomers say they’ve pieced the history together and identified the trigger: a series of supernovae explosions that began about 14 million years ago.

A series of stars in our neighbourhood exploded as supernovae starting about 14 million years ago. They created a vast bubble of gas about 1,000 light-years across called the Local Bubble. In the middle of that void sits the Sun. The Sun’s neighbours formed on the edge of that bubble, and the preceding supernova explosions were the catalyst for their formation.

A new study published in the journal Nature presents the findings. The title is “Star formation near the Sun is driven by expansion of the Local Bubble.” Catherine Zucker is the lead author and she’s an astronomer and data visualization expert.

“We’ve calculated that about 15 supernovae have gone off over millions of years to form the Local Bubble that we see today.”

Catherine Zucker, lead author, NASA Hubble Fellow at STScI.

Stars form from clouds of hydrogen gas called Giant Molecular Clouds (GMC.) For a star to form, enough of the gas has to gather in one spot. This happens when the density of the gas varies. Due to gravity, density begets more density, and if enough time passes and if conditions are right, sufficient gas clumps together to trigger fusion, and a star is born.

But stars can also form when supernovae explode. Supernova explosions release a tremendous amount of energy, and that energy travels outward in a shockwave. The shockwave pushes gas together into clouds and creates greater density. That can lead to new stars.

That’s what happened in our neighbourhood, and it formed stars on the edge of the Local Bubble, which is also the edge of supernova shockwaves. Inside the Local Bubble, the density of the Interstellar Medium (ISM) is much lower than the density of the ISM throughout the Milky Way. The series of supernovae explosions pushed the gas aside, forming the edge of the bubble of dense ISM and driving star formation there.

“This is an incredible detective story, driven by both data and theory.”

Alyssa Goodman, study co-author, CfA Professor.

The edge of the bubble has fragmented and collapsed over time into star-forming clouds. Its once-smooth edge is gone. The team reports that there are seven star-forming regions on the bubble’s surface in the form of molecular clouds. These include Orion A and Orion B, both prominent parts of the Orion Molecular Cloud Complex. “Remarkably, we find that every well-known molecular cloud within ~200 pc of the Sun lies on the surface of the Local Bubble,” the paper says. The exception might be the Perseus Molecular Cloud.

The star formation didn’t happen all at once. In their paper, the authors point out that it happened in four distinct epochs: 10 Myr ago, 6 Myr ago, 4 Myr ago, and in the present age. They don’t know exactly how many supernovae exploded to create the bubble, but they’ve constrained it between 8 and 26, settling on 15 as the most likely number. “We’ve calculated that about 15 supernovae have gone off over millions of years to form the Local Bubble that we see today,” said Zucker, who is now a NASA Hubble Fellow at STScI.

This figure shows the evolution of the Local Bubble and sequential star formation at the surface of its expanding shell. Selected time snapshots (seen from a top-down projection) are shown here. The central figure shows the present day. Stellar cluster tracebacks are shown with the coloured paths. Prior to the cluster birth, the tracebacks are shown as unfilled circles meant to guide the eye, since the modelling is insensitive to the dynamics of the gas before its conversion into stars. After the cluster birth, the tracebacks are shown with filled circles and terminate in a large dot, which marks the cluster’s current position. For time snapshots ? 14 Myr ago, we overlay a model for the evolution of the Local Bubble (purple sphere). The solar orbit is shown in yellow dots and indicates that the Sun entered the Local Bubble approximately 5 Myr ago. Image Credit: Zucker et al 2022. Did you miss our previous article…
https://www.mansbrand.com/exoplanet-found-with-a-highly-eccentric-orbit/

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Hubble is Offline Because of a Problem with one of its Gyros

Hubble Servicing Mission 4 1024x575 1 jpg

The rich flow of scientific data—and stunning images—that comes from the Hubble Space Telescope is being interrupted by gyro problems. One of the telescope’s three remaining gyros gave faulty readings, and the Hubble automatically entered safe mode. In safe mode, science operations are suspended.

Without gyros, the Hubble can’t orient itself properly. Gyros measure the telescope’s turn rate and help the telescope know where it’s pointed. They’re part of the system that keeps the space telescope pointed in the right direction. There’s no indication of any problems with Hubble’s instruments, like its Wide-Field Camera 3 or its Advanced Camera for Surveys.

This all began on November 19th when Hubble went into safe mode. Engineers recovered the telescope, and regular science operations resumed the following day. However, the unstable gyro caused problems again, and the space telescope suspended science operations again on the 21st. It was recovered again, then went back into safe mode on November 23rd. That’s where things stand now.

NASA is working to resume science operations of the Hubble Space Telescope after it entered safe mode Nov. 23 due to an ongoing gyroscope issue. Hubble’s instruments are stable, and the telescope is in good health: https://t.co/QOdJJ9WjYh pic.twitter.com/URRHYV3Le8

— Hubble (@NASAHubble) November 29, 2023

The Hubble was launched with six original gyros, but they failed fairly rapidly. During its last shuttle servicing mission in 2009, the Hubble received six new gyros. Three of them were the older type that failed fairly quickly, and three were new ones. The three older ones from 2009 have failed, and Hubble has three remaining gyros, and all of them have a more modern design. It can operate with a single functioning gyro, though it’s less efficient.

This image shows astronaut Mike Massimino during Service Mission 4 to the Hubble in 2009. Astronaut Mike Good is in the background. During SM-4, Hubble received new gyroscopes, as well as two new scientific instruments – the Cosmic Origins Spectrograph (COS) and Wide Field Camera 3 (WFC3). Image Credit: NASA
This image shows astronaut Mike Massimino during Service Mission 4 to the Hubble in 2009. Astronaut Mike Good is in the background. During SM-4, Hubble received new gyroscopes, as well as two new scientific instruments – the Cosmic Origins Spectrograph (COS) and Wide Field Camera 3 (WFC3). Image Credit: NASA

Each gyro is a small cylinder filled with fluid. Inside the fluid, an internal float spins thousands of times per second. The original six gyros and three of the 2009 replacements contained bromine in the fluid. The bromine ate away at the gyros, causing their eventual demise.

One of the Hubble's gyros. Older ones had bromine in their interior fluid, which ate away at the gyros, causing their demise. Image Credit: NASA
One of the Hubble’s gyros. Older ones had bromine in their interior fluid, which ate away at the gyros, causing their demise. Image Credit: NASA

This isn’t the first time failing gyros have caused a shutdown in Hubble’s science operations. The preceding incident happened in 2018. At that time, Ken Sembach was the Director of the Space Telescope Science Institute (STScI.) In an interview, he expressed some frustration, telling Business Insider, “We’ve had some issues with this gyro in the past, and we’ve got some possible leads on the current problem. But the thing that’s been clear on Hubble is that these gyros all have a mind of their own. I don’t think anybody really knows what’s going on with it right now.”

The gyros are just part of the system that keeps Hubble pointed where astronomers want it pointed. The system also includes reaction wheels and fine guidance sensors
Did you miss our previous article…
https://mansbrand.com/spider-pulsars-are-tearing-apart-stars-in-the-omega-cluster/

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Spider Pulsars are Tearing Apart Stars in the Omega Cluster

Black widow binary March 2018 Garlick 1024x659 1 jpg

Pulsars are extreme objects. They’re what’s left over when a massive star collapses on itself and explodes as a supernova. This creates a neutron star. Neutron stars spin, and some of them emit radiation. When they emit radiation from their poles that we can see, we call them pulsars.

In the last decade or so, astrophysicists have discovered many more millisecond pulsars, ones that rotate very rapidly. Not only is the number of known pulsars increasing, but researchers have also identified pulsar sub-types that have companions. These are called spider pulsars, and their companions face great peril. New research sheds light on how spider pulsars in Omega Centauri are tearing their companions to pieces with their powerful outflows.

The first spider pulsar ever discovered is PSR B1957+20, more widely known as the Black Widow Pulsar. It has a companion that’s either a brown dwarf or a super Jupiter. High-energy outflows from the Black Widow are destroying its companion. All pulsars that destroy their companions are known as spider pulsars, but there are two further sub-types of spider pulsars: redback pulsars and black widow pulsars.

Black widow binary March 2018 Garlick 1024x659 2 jpg
Artist’s impression of the pulsar PSR B1957+20 (seen in the background) through the cloud of gas enveloping its brown dwarf star companion. Credit: Dr. Mark A. Garlick; Dunlap Institute for Astronomy & Astrophysics, University of Toronto

Researchers working with the Chandra Space Telescope have examined Omega Centauri to learn more about how spider pulsars destroy their binary companions. Their work will be published in the Monthly Notices of the Royal Astronomical Society. The title is “A Chandra X-ray study of millisecond pulsars in the globular cluster Omega Centauri: a correlation between spider pulsar companion mass and X-ray luminosity.” The authors are Jiaqi Zhao and Craig O. Heinke, both from the Physics Department at the University of Alberta, Edmonton, Canada.

Omega Centauri is the largest globular cluster (GC) that we know of in the Milky Way. It’s almost 16,000 light-years away and contains about 10 million stars. Some of those stars are spider pulsars, a class of millisecond pulsars with companions.

Visualization of a fast-rotating pulsar. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab
Visualization of a fast-rotating pulsar. Credit: NASA’s Goddard Space Flight Center Conceptual Image Lab

Spider pulsars are terribly destructive neighbours. Their energetic winds methodically strip away their companions’ outer layers. To understand more about this phenomenon, the pair of researchers examined Chandra data from Omega Centauri, home to 18 recently discovered spider pulsars.

“Millisecond pulsars (MSPs) are faint X-ray sources commonly observed in Galactic globular clusters (GCs),” the researchers write. “In this work, we investigate 18 MSPs newly found in the GC Omega Centauri and search for their X-ray counterparts using Chandra observations.”

Out of the 18 millisecond pulsars, 11 of them emit x-rays that Chandra can see. Five of them are spider pulsars near Omega Centauri’s center. They combined these with Chandra’s observations of 26 spider pulsars in 12 other globular clusters. Using this data, the pair of researchers examined empirical correlations between X-ray luminosities and the minimum masses of their companions.

Did you miss our previous article…
https://mansbrand.com/not-getting-enough-data-from-mars-set-up-a-solar-system-pony-express/

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Not Getting Enough Data From Mars? Set Up A Solar System Pony Express

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Getting data in from deep space can be difficult. Almost all of our missions that have flown into deep space use the Deep Space Network, a system of transmitters and receivers that already imposes constraints on the amount of data we can transfer from the far reaches of space. So a team led by Joshua Vander Hook, then at NASA’s Jet Propulsion Laboratory and now at a start-up called Outrider.ai, came up with a way to dramatically enhance the throughput of the DSN. In so doing, they gave it a very catchy name – the Solar System Pony Express.

Dr. Vander Hook was initially supported by a NASA Institute for Advanced Concepts (NIAC) grant in 2021. The basic concept utilizes what is known as a “cycler” orbit, where a spacecraft repeatedly orbits between two bodies in the solar system using their gravity wells to swing around in sync with when their orbits pass each other. 

In this case, the spacecraft would consist of a communications relay module that would collect high-throughput data from an observer module parked in orbit around the other body. The observer module would consistently download data from the missions operating in its local area and then, when a relay module gets close, would rapidly send all of that data to the cycling spacecraft. The cycler then returns to Earth, where another rapid download process begins, and the cycle repeats itself.

Fraser discusses some of the problems of communicating with deep space probes – especially those going to other stars.

That sounds like the Pony Express – a system in the 1800s whereby mail carriers would ride physical ponies (or horses) to deliver mail occasionally to remote outposts in the American West. In another homage to that mail carrier heritage, the team named the cycling relay satellites “data mules.”

Those data mules would have a long trip between Earth and their target destination. It might come as no surprise that in much of the literature surrounding the idea that the target destination was Mars. Buzz Aldrin, the most famous proponent of cycler orbits, suggested that cycler “castles” could effectively shuttle people and goods between Mars and Earth. But in this new configuration, instead of physical things, it would be more beneficial to ship data.

image 1
Another Depiction of how the observer / data mule interaction would go.
Credit – Marc Sanchez-Net et al.

Calculations described in a paper released last year estimate that with as little as six data mules, the network could provide a bandwidth of 1 petabyte a year from the surface of Mars while only requiring a minor allocation of time on the DSN. That would potentially allow some real-time high-definition video from the red planet, which would undoubtedly be attractive to many of the inhabitants of its nearest neighbor.

However, such high data rates come at a cost. In the case of the Solar System Pony Express, that cost is latency. The high throughput data transfer possible between the observer and a data mule, and then again from the data mule back to a receiving station on Earth, is only possible if they are in physical proximity to each other, as the network would use a type of high-throughput optical communications network. And since cycler orbits can take years, it would be years after the data was collected on the red planet that anyone could use it.

That is not a show stopper – indeed, many people would be okay with waiting for over a year for a high-definition video from Mars if that is the only way for them to see it. But it makes funding such a mission more difficult given the immediate feedback culture prevalent in many of today’s media. Give the authors credit, though – they recognize this limitation and, as all good scientists do, mention that it would be a good topic for further study.

For right now, that further study seems to be on hold. Dr. Vander Hook has moved on to other non-space-related efforts. While there has been some interest from researchers elsewhere, such as a paper from the University of Illinois, there’s currently no clear path forward for the project. But, there will always be a desire for more data transfer from farther out in the solar system. If the Pony Express is the most cost-effective way to get it at the beginning of our explorations, then don’t be surprised if this concept is resurrected sometime in the future.

Learn More:
Pascarella et al – Low-thrust trajectory optimization for the solar system pony
Did you miss our previous article…
https://mansbrand.com/a-protoplanetary-disc-has-been-found-in-another-galaxy/

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