The first roadblock facing humans as we seek to expand our presence in the solar system lies in technology. NASA reports that it takes about seven months (measured in Earth days) to travel from our planet’s surface to Mars. Thrillist notes that travel to the Moon only requires a three-day journey, while exploration of Jupiter or Saturn (the next bodies out from Mars) would require a lengthy, six- or seven-year voyage, respectively. On a technical level, our current means of launching satellites and humans at these distant bodies is exactly that, a launch (via NASA). In order to make space travel more feasible for human explorers, we would need to develop a propulsion system that could continually deliver powered flight to a spacecraft, or at least the ability to continually augment flight speed, rather than simply relying on initial launch velocity to carry the craft along to its final destination.
This means a combination of two distinct realities: Humans must develop a brand new means of propulsion that requires far less storage space and mass, a revolutionary idea to be sure; and we must develop the ability to hop between planets and refuel along this lengthy journey. Therefore, technological advancement that would support increased space travel would require both colonization and a capacity for extracting mineral resources from the surfaces of neighboring planets and moons. Continuous habitation in new worlds would be required to support these efforts.
UBC Okanagan study to investigate where Eurasian watermilfoil occurs in lakes – Vernon Morning Star
A UBC Okanagan pilot project is seeking to better pinpoint and map where the beginnings of Eurasian watermilfoil (EWM) infestation occurs in the large lakes within the Okanagan Valley watershed.
If this pilot project proves successful, it could become a blueprint for other jurisdictions to follow in their own battles with this aquatic plant or other invasive aquatic species, says UBCO assistant professor Mathieu Bourbonnais.
Bourbonnais, with the Irving K. Barber Faculty of Science, is overseeing the project with the assistance of masters graduate student Mackenzie Clarke.
The data modelling prototype is using the technology of topobathymetric lidar, the science of simultaneously measuring and recording three distinct surfaces – land, water and submerged land up to 20 metres below the water surface – using airborne laser-based infrared imagery sensors.
Bourbonnais says being able to better identify potential or small milfoil patches will give better control management tools for the Okanagan Basin Water Board’s Euroasian watermilfoil harvest program, which currently is about an $800,000 a year initiative to try and control the growth and limit the damage of the invasive water plant.
It could also potentially target specific watermilfoil growth sites before they grow out of control near valley lake areas deemed sensitive by Environment Canada for the preservation of the Rocky Mountain Ridge Mussels.
He said EWM has been a formidable invasive aquatic plant species to control since it was introduced into the Okanagan Valley lake system some 40 years ago.
It has also illustrated to the water board the need to be stringent when trying to avoid the Zebra and Quagga mussels from being introduced into the lake system.
Like watermilfoil, there is no solution for removing the mussels once they are introduced into a lake system. It is a rooted submerged plant inhabiting the shallows waters of lakes across North America.
EWM originated from Asia, Europe and Northern Africa and has spread rapidly, introduced in North America from the ballast water of ships or aquarium activities.
Bourbonnais said a lake choked with watermilfoil growth impacts the biodiversity and food webs reliant on the lake habitat, alter the water temperature and impacts its recreational use for swimmers and boaters.
“The impact of invasive species on our lake aquatic systems costs billions of dollars to deal with across the country. It definitely has an impact both ecologically and economically,” he said.
The pilot project fieldwork will be done by early spring, he said, with the hope it provides data upon which to target areas for harvesting leading up to the permit application process next year.
“The goal is the Okanagan Basin Water Board can take the data generated from this research model and liaise with the province and federal government on how to go forward,” he said.
“We hope it can help the management strategy of where to send the lake rototillers to pull up the plants.”
How Do Stars Get Kicked Out of Globular Clusters? – Universe Today
Globular clusters are densely-packed collections of stars bound together gravitationally in roughly-shaped spheres. They contain hundreds of thousands of stars. Some might contain millions of stars.
Sometimes globular clusters (GCs) kick stars out of their gravitational group. How does that work?
There are a few things that can cause GCs to eject stars. Gravitational scattering, supernovae, tidal disruption events, and physical collisions could all be responsible. Whatever’s behind it, the gradual ejection of stars from GCs is an established phenomenon.
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The evidence for stellar ejection from GCs is in the tidal tails that stream out from them.
A new study based on data from the ESA’s Gaia mission aims to understand how GCs eject stars. Its title is “Stellar Escape from Globular Clusters I: Escape Mechanisms and Properties at Ejection.” It’s been submitted to the Astrophysical Journal, and the lead author is Newlin Weatherford, an astronomy Ph.D. student at Northwestern University in Illinois.
“Recent exquisite kinematic data from the Gaia space telescope has revealed numerous stellar streams in the Milky Way (MW) and traced the origin of many to specific MWGCs, highlighting the need for further examination of stellar escape from these clusters,” the authors write. This study is the first of a series, and the authors examine all the escape mechanisms and how each one contributes to GC star loss.
GCs are some of the oldest stellar associations in the Milky Way. Individual GC stars are also older and have lower metallicity than the Milky Way’s general population. Nearly all galaxies host GCs, and in spiral galaxies like ours, the GCs are mostly found in the halo. The Milky way hosts more than 150 of them. Astronomers used to think that stars in a GC form from the same molecular cloud, but now they know that that’s not true. GCs contain stars of different ages and metallicities.
GCs are different from their cousins, the open clusters (OCs). OCs are most often found in the disks of spiral galaxies, have more heavy elements, and are less dense and also smaller than GCs. OCs have only a few thousand stars, and there are more than 1100 of them in the Milky Way.
GCs are unique, and astronomers consider them tracers of galactic evolution. Thanks largely to the ESA’s Gaia spacecraft, we know more about GCs. Gaia helped reveal the presence of numerous stellar streams coming from the Milky Way’s globular clusters. As the authors explain in their paper, “These drawn-out associations of stars on similar orbits are likely debris from disrupted dwarf galaxies and their GCs, shorn off by Galactic tides during accretion by the MW (Milky Way.)”
Gaia did more than spot these streams. It was able to connect some streams to specific GCs. “Gaia’s exquisite kinematic data has firmly tied the origins of ~10 especially thin streams to specific MWGCs,” the authors write. The Palomar 5 GC and its streams are well-known examples. The streams are excellent tracers of the Milky Way’s evolution. (Palomar 5 gained even more notoriety in astronomy recently when a 2021 paper found more than 100 black holes in its center.)
Observations of these types of tails, both from stars ejected from GCs, and from interacting and merging galaxies, are an extremely active area of research. There are many astounding images of these interactions. But as the authors point out, “… the theoretical study of stellar escape from GCs has a longer history.” Astronomers have come up with different mechanisms for these escapes, and this paper starts with a review of each one.
The authors divide escape mechanisms into two categories: Evaporation and Ejection. Evaporation is gradual, while ejection is more abrupt. The following are brief descriptions of each of the ejection methods, beginning with the Evaporation category.
Two-Body Relaxation: the motions of each body induce granular perturbations that create exchanges in energy and momentum in the bodies. Over time, stars can be ejected from GCs.
Cluster mass loss: stars lose mass over time, and that can affect the gravitational binding that holds stars in the cluster.
Sharply time-dependent tides: MWGCs orbit the Milky Way in eccentric and inclined orbits. The galactic tide will be stronger at some points in the orbit. The changing gravity can allow stars to exit the GCs.
The second broad category is Ejection. These are events typically involving single stars that are ejected rapidly and dramatically.
Strong Encounters: a close passage between two or more bodies that provides a strong enough kick to eject a star.
(Near)-Contact Recoil: encounters so close that tides, internal stellar processes, and/or relativistic effects are relevant. This includes collisions and gravitational waves.
Stellar Evolution Recoil: This includes the powerful forces unleashed when a star goes supernova, for example, or when a black hole or neutron star is formed.
Since there was no way to go and observe a statistically significant number of GC ejections, the team of researchers took what data was available and performed simulations. They used what’s called the CMC Cluster Catalog.
The study is concerned with the two types of GCs: non-core collapsed and core-collapsed. They’re different from each other and are a fundamental property of GCs, so the team simulated both types.
Core collapse in GCs occurs when the more massive stars in a GC encounter less massive stars. This creates a dynamic process that, over time, drives some stars out of the center of the GC towards the outside. This creates a net loss of kinetic energy in the core, so the remaining stars in the GCs core take up less space, creating a collapsed core.
An important astronomical principle plays a role in the team’s results. Two-body relaxation is a fundamental aspect of stellar associations that has far-reaching effects. It’s a complicated topic, but it basically describes the ways that stars in stellar associations, such as GCs, interact gravitationally and share kinetic energy with each other. It shows that star-to-star interactions drive GCs to evolve during the lifetime of the galaxy they’re attached to.
Not surprisingly, the researchers found that two-body relaxation plays a powerful role. That conclusion lines up with the established theory. “Consistent with longstanding theory and numerical modelling, we find that two-body relaxation in the cluster core dominates the overall escape rate,” they write.
They also found that “… central strong encounters involving binaries contribute especially high-speed
ejections, as do supernovae and gravitational wave-driven mergers.” This also lines up with other research.
But one of their results is new. It concerns three-body binary formation (3BBF.) 3BBF is when three bodies collide to form a new binary object. “We have also shown for the first time that three-body binary formation plays a significant role in the escape dynamics of non-core-collapsed GCs typical of those in the MW. BHs are an essential catalyst for this process,” they write. “3BBF dominates the rate of present-day high-speed ejections over any other mechanism,” they explain, as long as significant numbers of BHs remain in the GCs core. 3BBFs also produce a significant number of hypervelocity stars.
In their conclusion, the authors explain that “… this study provides a broad sense of the escape mechanisms and demographics of escapers from GCs,” while also noting that the results are “not immediately comparable to Gaia observations.” That’s why this work is the first in a series of papers. In their follow-up paper, they intend to integrate the trajectories of escaped stars and construct their velocity distributions to reproduce tidal tails. After that work, they hope that they’ll have a clearer understanding of how stars escaping from GC contribute to galactic evolution.
In a third paper, they intend to “… identify likely past members (‘extratidal candidates’) of specific MWGCs and directly compare the mock ejecta from our cluster models to the Gaia data.” This will get closer to some of the core questions surrounding GCs and the Milky Way’s evolution: how do stellar streams form? How many BHs are there in GCs? What role do supernovae play?
“Ultimately, we hope to better understand stellar stream formation and, in an ideal case, leverage the new
observables from Gaia to better constrain uncertain properties about MWGCs, such as BH content, SNe kicks, and the initial mass function, which affect ejection velocities and the cluster evaporation rate.”
This study is an interesting look at how a number of natural phenomena all contribute to galactic evolution. The evolution of individual stars, how individual stars interact gravitationally and how they form binary objects, the tidal interactions between globular clusters and their host galaxies, two-body relaxation, and even three-body binary formation. Throw in supernovae and hypervelocity stars.
Each one of these topics can form the basis of an entire career in astrophysics. It’s easy to see why follow-up studies are needed. Once they’re completed, we’ll have a much better picture of how galaxies, specifically our own Milky Way, evolve.
How to see Mars at its brightest at opposition this week
Stargazers in the northern hemisphere are in for a treat this week as Mars has reached its closest point to Earth, giving the best view of the red planet until the 2030s. Mars made its closest approach to Earth on the night of November 30 to December 1, but the best views are yet to come as the planet reaches a point called opposition on the night of December 7 to December 8. Opposition is when Mars is directly opposite the sun as seen from Earth, which means this is when Mars will be at its brightest.
The reason that the closest approach and opposition are a few days apart is because of the elliptical nature of the planets’ orbits. Neither Earth nor Mars orbits in a perfect circle around the sun, so there are times when they are a little closer or a little further away. These small differences account for the few days’ delay between closest approach and opposition. The elliptical nature of Mars’s orbit is also why there will be such a great view of the planet this week. Mars won’t come back this close to Earth until 2033.
This diagram from the U.K.’s Royal Astronomy Society shows how to locate Mars in the night sky on the evening of December 8. Mars should be one of the brightest objects in the skies, so if you’re lucky to have clear weather overhead at night then you should easily be able to spot the planet with binoculars or a telescope. At this time, Mars will be around 50 million miles away.
December 8 is also a great time to look for Mars as you may be able to spot the moon moving in front of the planet, called an occultation, depending on where in the northern hemisphere you are located. For exact times to look out for this event by U.S. region, head over to Sky and Telescope for more information.
According to Sky at Night magazine, you should be able to observe Mars using almost any telescope, but adding a Barlow lens to your setup will give you a better view and enhance the darker and lighter patches on the planet. You may be able to see features on Mars like its polar ice caps, its patches of light and dark which are called albedo features, and perhaps even certain large geological features like basins and plains.
Some of the most dramatic views of Mars will be on the night of December 8, but if that doesn’t work out for you then you should also look to the skies in the week before and after this date as you should still be able to get a good view then.
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