Astronomy

Where can I find a list of retrograde Milky Way stars?

Where can I find a list of retrograde Milky Way stars?


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I read in papers that the Milky Way contains some retrograde stars (retrograde to the Milky Way rotation). Does anybody know where I can find a list of them, possibly including data on their distance from the Milky way center? many thanks


The Milky Way's outer halo has many globular clusters with a retrograde orbit (about 40% of all clusters in Milky Way). One of the more prominent example include Kapteyn's star which is highly retrograde due to it being ripped from a dwarf galaxy and merging with the Milky Way.

However, the structure of the halo is a topic of an ongoing debate. Several studies have claimed that the halo consists of two distinct components. The "inner" halo consists of more metal-rich, prograde stars and "outer" halo consisting of metal-poor, retrograde stars. These findings have been challenged many times due to the argument on the topic of "duality of motion".

More readings here:

  1. Carollo et al. 2007
  2. Kravtsov 2001
  3. Kordopatis et al. 2020

Summary:: Looking for a model--any model but one in particular--of extragalactic stellar motion.

Is there any pattern at all to the motion of extragalactic stars passing within one or two galactic radii of Milky Way on hyperbolic transits?

couldnt even find any extragalactic stars that fit your idea. I went through a large list of specific extragalactic ( to the Milky Way) stars
and all but 1 or 2 were associated with other galaxies

So, what stars did you have in mind ?

I have not heard of any reason to believe they deviate from Newton or Einstein.

The distance to stars is usually listed with an error range. If the star in question is 2 galactic radii away from us distance measurements are very suspicious. A single star's motion can be caused but a wide variety of factors.

Most hypervelocity stars were ejected from the Milky Way. Extragalactic stars that were ejected from some other galaxy but did arrive here are going to be extremely rare. In a few billion years when Milky Way and Andromeda are about to merge they will temporarily become more common.


Highlights

  1. By calculating the age of the stars, the researchers were able to determine, for the first time, that the stars captured from Gaia-Enceladus have similar or slightly younger ages compared to the majority of stars that were born inside the Milky Way.

Washington: New study led by researchers at Ohio State University provides the latest evidence into the timing of how our early Milky Way came together, including the merger with a key satellite galaxy.

Their results were published in the journal Nature Astronomy. Using relatively new methods in astronomy, the researchers were able to identify the most precise ages currently possible for a sample of about a hundred red giant stars in the galaxy.

With this and other data, the researchers were able to show what was happening when the Milky Way merged with an orbiting satellite galaxy, known as Gaia-Enceladus, about 10 billion years ago.

"Our evidence suggests that when the merger occurred, the Milky Way had already formed a large population of its own stars," said Fiorenzo Vincenzo, co-author of the study and a fellow in The Ohio State University`s Center for Cosmology and Astroparticle Physics.

Many of those "homemade" stars ended up in the thick disc in the middle of the galaxy, while most that were captured from Gaia-Enceladus are in the outer halo of the galaxy.

"The merging event with Gaia-Enceladus is thought to be one of the most important in the Milky Way`s history, shaping how we observe it today," said Josefina Montalban, with the School of Physics and Astronomy at the University of Birmingham in the U.K., who led the project.

By calculating the age of the stars, the researchers were able to determine, for the first time, that the stars captured from Gaia-Enceladus have similar or slightly younger ages compared to the majority of stars that were born inside the Milky Way.

A violent merger between two galaxies can`t help but shake things up, Vincenzo said. Results showed that the merger changed the orbits of the stars already in the galaxy, making them more eccentric.

Vincenzo compared the stars` movements to a dance, where the stars from the former Gaia-Enceladus move differently than those born within the Milky Way.

The stars even "dress" differently, Vincenzo said, with stars from outside showing different chemical compositions from those born inside the Milky Way.

The researchers used several different approaches and data sources to conduct their study.

One way the researchers were able to get such precise ages of the stars was through the use of asteroseismology, a relatively new field that probes the internal structure of stars.

Asteroseismologists study oscillations in stars, which are sound waves that ripple through their interiors, said Mathieu Vrard, a postdoctoral research associate in Ohio State`s Department of Astronomy.

"That allows us to get very precise ages for the stars, which are important in determining the chronology of when events happened in the early Milky Way," Vrard said.

The study also used a spectroscopic survey, called APOGEE, which provides the chemical composition of stars- another aid in determining their ages.

"We have shown the great potential of asteroseismology, in combination with spectroscopy, to age-date individual stars," Montalban said.

This study is just the first step, according to the researchers."We now intend to apply this approach to larger samples of stars and to include even more subtle features of the frequency spectra.

This will eventually lead to a much sharper view of the Milky Way`s assembly history and evolution, creating a timeline of how our galaxy developed," Vincenzo said.


Mysterious ‘yellowballs’ littering the Milky Way are clusters of newborn stars

The Milky Way is strewn with ‘yellowballs’ (circled in this false-color infrared panorama from the Spitzer Space Telescope), regions of ionized gas bubbles where baby stars are born.

Charles Kerton/Iowa State University, Spitzer/NASA

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Scientists have cracked the case of mysterious cosmic objects dubbed “yellowballs.” The celestial specks mark the birthplaces of many kinds of stars with a wide range of masses, rather than single supermassive stars, researchers report April 13 in the Astrophysical Journal.

The stars in the clusters are relatively young, only about 100,000 years old. “I think of these as stars in utero,” says Grace Wolf-Chase, an astronomer at the Planetary Science Institute who is based in Naperville, Ill. For comparison, the massive stars forming in the Orion nebula are about 3 million years old, and the middle-aged sun is 4.6 billion years old.

Volunteers with the Milky Way Project first identified the objects while scouring pictures of the galaxy taken by the Spitzer Space Telescope. The now-defunct observatory saw the cosmos in infrared light, which let astronomers take a sort of stellar ultrasound “to probe what’s going on in these cold environments before the stars are actually born,” says Wolf-Chase.

Citizen scientists had been looking through these images for baby stars thought to be at least 10 times the mass of the sun that were blowing giant bubbles of ionized gas. A year or two into the project, some users began labeling certain objects with the tag #yellowballs¸ because that’s what they looked like in the false-color images. Between 2010 and 2015, the volunteers found 928 yellowballs.

Wolf-Chase’s team initially thought the balls represented early stage gas bubbles. But because yellowballs were a serendipitous discovery, the researchers knew they probably hadn’t caught enough of them to definitively ID the objects. In 2016, the team asked Milky Way Project volunteers to find more. By the following year, the group had spotted more than 6,000 yellowballs.

Astronomers first thought ‘yellowballs’ (circled left) were precursors to gas bubbles blown around massive, young stars (right). But a new study suggests yellowballs are actually clusters of less massive stars. JPL-Caltech/NASA

Wolf-Chase and colleagues compared about 500 of those balls to existing catalogs of star clusters and other structures to try to figure out what they were. “Now we have a good answer: They’re infant star clusters,” Wolf-Chase says. The clusters blow ionized bubbles of their own, similar to the stellar bubbles blown by single young, big stars.

Wolf-Chase hopes researchers will be able to use the work to pick out yellowballs with telescopes like the James Webb Space Telescope, which is due to launch in October, and figure out more about the balls’ physical properties.

Questions or comments on this article? E-mail us at [email protected]

A version of this article appears in the June 5, 2021 issue of Science News.


Where to Go Stargazing in Bryce Canyon

Photo credit: Barton Davis Smith via Flickr

While there are quite a few overlooks great for stargazing in Bryce Canyon, some are better than others. These overlooks will offer similar but different scenery, especially the first and last.

  • Natural Bridge Overlook – This overlook will offer a different view than most others. Instead of just hoodoos, you’ll get to admire the stars over (and under!) the natural bridge.
  • Inspiration Point, Sunset Point, or Sunrise Points – These are all great views over the Bryce Amphitheater, the most iconic area of the park. The skies are wide open. You can’t go wrong here.
  • Farview Point – This viewpoint can be appreciated best during the day offering views of Arizona 160 miles away, but that just means there is plenty of open skies to see the stars. It may be less busy than the Bryce Amphitheater area.
  • Mossy Cave Trail – This is the place to escape the crowds since it isn’t on the main scenic road. Back out on Highway 12, you’ll find the Mossy Cave Trail and parking area. There is also a waterfall here offering a different foreground for stargazing that stands out from the rest of the park scenery.

While there are plenty of places within Bryce Canyon National Park to go stargazing, you can find stellar stargazing in the whole area. The skies are incredibly dark in this area making it a prime stargazing destination.


Milky Way not unusual, astronomers find

The first detailed cross-section of a galaxy broadly similar to the Milky Way, published today, reveals that our galaxy evolved gradually, instead of being the result of a violent mash-up. The finding throws the origin story of our home into doubt.

The galaxy, dubbed UGC 10738, turns out to have distinct 'thick' and 'thin' discs similar to those of the Milky Way. This suggests, contrary to previous theories, that such structures are not the result of a rare long-ago collision with a smaller galaxy. They appear to be the product of more peaceful change.

And that is a game-changer. It means that our spiral galaxy home isn't the product of a freak accident. Instead, it is typical.

The finding was made by a team led by Nicholas Scott and Jesse van de Sande, from Australia's ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) and the University of Sydney.

"Our observations indicate that the Milky Way's thin and thick discs didn't come about because of a gigantic mash-up, but a sort-of 'default' path of galaxy formation and evolution," said Dr Scott.

"From these results we think galaxies with the Milky Way's particular structures and properties could be described as the 'normal' ones."

This conclusion - published in The Astrophysical Journal Letters- has two profound implications.

"It was thought that the Milky Way's thin and thick discs formed after a rare violent merger, and so probably wouldn't be found in other spiral galaxies," said Dr Scott.

"Our research shows that's probably wrong, and it evolved 'naturally' without catastrophic interventions. This means Milky Way-type galaxies are probably very common.

"It also means we can use existing very detailed observations of the Milky Way as tools to better analyse much more distant galaxies which, for obvious reasons, we can't see as well."

The research shows that UGC 10738, like the Milky Way, has a thick disc consisting mainly of ancient stars - identified by their low ratio of iron to hydrogen and helium. Its thin disc stars are more recent and contain more metal.

(The Sun is a thin disc star and comprises about 1.5% elements heavier than helium. Thick disc stars have three to 10 times less.)

Although such discs have been previously observed in other galaxies, it was impossible to tell whether they hosted the same type of star distribution - and therefore similar origins. Scott, van de Sande and colleagues solved this problem by using the European Southern Observatory's Very Large Telescope in Chile to observe UGC 10738, situated 320 million light years away.

The galaxy is angled "edge on", so looking at it offered effectively a cross-section of its structure.

"Using an instrument called the multi-unit spectroscopic explorer, or MUSE, we were able to assess the metal ratios of the stars in its thick and thin discs," explained Dr van de Sande.

"They were pretty much the same as those in the Milky Way - ancient stars in the thick disc, younger stars in the thin one. We're looking at some other galaxies to make sure, but that's pretty strong evidence that the two galaxies evolved in the same way."

Dr Scott said UGC 10738's edge-on orientation meant it was simple to see which type of stars were in each disc.

"It's a bit like telling apart short people from tall people," he said. "It you try to do it from overhead it's impossible, but it if you look from the side it's relatively easy."

Co-author Professor Ken Freeman from the Australian National University said, "This is an important step forward in understanding how disk galaxies assembled long ago. We know a lot about how the Milky Way formed, but there was always the worry that the Milky Way is not a typical spiral galaxy. Now we can see that the Milky Way's formation is fairly typical of how other disk galaxies were assembled".

ASTRO 3D director, Professor Lisa Kewley, added: "This work shows how the Milky Way fits into the much bigger puzzle of how spiral galaxies formed across 13 billion years of cosmic time."

Other co-authors are based at Macquarie University in Australia and Germany's Max-Planck-Institut fur Extraterrestrische Physik.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.


The Bushcamp Company Bilimungwe Bushcamp, Zambia

The brand-new eco-friendly Star Deck at Bilimungwe Bushcamp in Zambia’s Luangwa National Park—teeming with hippos, elephants, lions, giraffe and all the gorgeous gazelle species you could wish to see—gives safarigoers a 360-degree view of the night sky. All the guides are trained in stargazing, and can point out individual stars, planets and constellations using laser pointers and an astronomical telescope.


These Nyx Stars in Milky Way Came from Outside the Galaxy

T he Milky Way contains hundreds of millions of stars, but not all of them are native to our galaxy. Astronomers have now found stars in our home galaxy that formed outside our family of stars.

Nyx, a cluster of roughly 250 stars recently discovered within our galaxy, display velocities showing they originated outside our galaxy. This stellar stream likely arrived as part of a dwarf galaxy that merged with the Milky Way long ago. As the cluster approached the Milky Way, this family of stars was stretched out by gravity from our galaxy, pulling the cluster like taffy.

On July 28, Dr. Lina Necib, an astrophysicist at the heart of this discovery, will appear on Astronomy News with The Cosmic Companion — make sure to tune in!

Using FIRE (Feedback In Realistic Environments) simulations, astronomers are able to model groups of stars, revealing the origin of these stellar furnaces. Starting models soon after the Big Bang, this simulation, one of the largest models of its type, shows how galaxies form into the formations we see today. Even using supercomputers, these nine simulations took months to complete.

The GAIA spacecraft, launched in 2013, is on a mission to create 3D maps of a billion stars in and beyond the Milky Way.

“It’s the largest kinematic study to date. The observatory provides the motions of one billion stars. A subset of it, seven million stars, have 3D velocities, which means that we can know exactly where a star is and its motion. We’ve gone from very small datasets to doing massive analyses that we couldn’t do before to understand the structure of the Milky Way,” Lina Necib, a postdoctoral scholar in theoretical physics at Caltech, explains.

A sample of virtual galaxies developed by FIRE. (Background stars are just for artistic effect.) Image credit: Northwestern University.

Combining the findings of GAIA and FIRE, Necib and her team were able to model these stars using deep learning methods. They found that the Milky Way, once thought to have experienced few collisions, may have merged with a greater number of small galaxies than previously believed.

“Galaxies form by swallowing other galaxies. We’ve assumed that the Milky Way had a quiet merger history, and for a while it was concerning how quiet it was because our simulations show a lot of mergers. Now, with access to a lot of smaller structures, we understand it wasn’t as quiet as it seemed,” Necib describes.

Mock Sausage without the Tempeh

Data from a billion stars is impossible to study by humans without the assistance of dedicated computer systems.

“We can’t stare at seven million stars and figure out what they’re doing. What we did in this series of projects was use the Gaia mock catalogs,” Necib explains.

The Gaia mock catalogs, developed by Robyn Sanderson of the University of Pennsylvania, examines what astronomers would see if the FIRE simulations were correct, and seen by GAIA.

Lina Necib of Caltech, the astrophysicist who headed this discovery, will appear on The Cosmic Companion July 28. Image credit: Northwestern University

“We needed to make sure that we’re not learning artificial things about the simulation, but really what’s going on in the data. For that, we had to give it a little bit of help and tell it to reweigh certain known elements to give it a bit of an anchor,” Necib explains.

The team tested the simulation on known features of the Milky Way, including the Gaia Sausage, a distinct collection of stars once part of a dwarf galaxy, which merged with the Milky Way sometime between six and 10 billion years ago. These stars have a distinct orbital shape, which showed up in the simulations, along with halo stars which give our galaxy its shape, providing evidence the models were correct.

By studying baryons (a class of subatomic particle), the Ananke framework, developed at Northwestern University, models the behavior of stars.

“The Ananke framework generates realistic synthetic stellar surveys from cosmological baryonic simulations… The result is a self-consistent, dust-extincted synthetic survey of each simulated galaxy that leaves intact important observational relationships between gas, dust extinction, stellar populations, and dark matter,” researchers at Northwestern report.

The model also revealed a group of 250 stars traveling toward the center of the Milky Way, while also orbiting around the galaxy.

“The Nyx stars were found on two stages. First through a machine learning algorithm led by my collaborator Bryan Ostdiek, where we trained on the Ananke simulations to distinguish accreted stars (stars born in other galaxies and brought in through mergers) and disk stars, stars born in the Milky Way. After this first run, Bryan handed me a catalog of stars with an accretion score. I then used a clustering algorithm in kinematics to find these particular stars. Said another way, these stars have very specific motion, where they are corotating with the disk of the Milky Way, but they are also going to the center of the galaxy. This is interesting as it would be the first evidence of a merger that happened parallel to the disk,” Necib tells The Cosmic Companion.




When Dr. Necib first saw this data, she assumed the findings were in error, and did not inform her colleagues about the finding for three weeks. During that time, she realized that what she was seeing was real, and brought the data to her fellow researchers.

Necib searched previous findings to see if anyone else had previously discovered this group of stars, and found she was the first researcher to recognize the group. This gave the researcher the chance to name this unusual family of stars. She named the group Nyx, in honor of the Greek Goddess of the night.

The FIRE simulation provides realistic modeling of stars, but it is not specifically designed to model the Milky Way. The model was modified through experience learned from particle physics experiments conducted at the Large Hadron Collider (LHC) near Geneva.

“At the LHC, we have incredible simulations, but we worry that machines trained on them may learn the simulation and not real physics. In a similar way, the FIRE galaxies provide a wonderful environment to train our models, but they are not the Milky Way. We had to learn not only what could help us identify the interesting stars in simulation, but also how to get this to generalize to our real galaxy,” explained physicist Bryan Ostdiek of Harvard University.

The image of the synthetic survey was made by Professor Robyn Sanderson, (University of Pennsylvania, and Center of Computational astrophysics) out of one of the synthetic Gaia surveys of the Latte simulations — it’s the star-by-star sum of all the starlight that would be observed by Gaia in its three color filters, for one of our simulated galaxies. It was produced in the same way as this image made from the real Gaia survey (though using slightly different color channels). This image originally appeared here.

The team developed methods to track stars in the simulation, labeling each as being born in, or outside, the virtual galaxy being studied. This was then used to train the deep learning model, and applied to other FIRE galaxies.

“Accreted stars at the location of the sun are about 1–2% of the stars, making them very hard to find without dedicated techniques, which is why using machine learning was very helpful in this case,” Necib tells The Cosmic Companion.

Necib plans to continue her work on these Nyx stars, and similar bodies, using data currently collected by GAIA, as well as performing additional research, using some of the most powerful telescopes in the world.

“I am very excited about the third data release of Gaia, which should be next year. Other than that, with my collaborator Alexander Ji, I have two approved observing proposals at Keck in Hawaii, and Magellan in Chile to observe the chemical abundances of Nyx stars and therefore confirm their origin,” Necib explains.

This study was detailed in an article published in the journal Nature Astronomy.

This finding, and other ones that further this research, help us learn more about the galaxy we all call home.


9 . Book a cruise with a resident astronomer.

Cunard's Queen Mary 2 and Viking Ocean Cruises' Viking Orion not only teach about the stars in their onboard planetariums, but they regularly bring astronomers onboard to give presentations and lead stargazing sessions. Cunard partners with members of the U.K.'s Royal Astronomical Society, while Viking hires its own resident astronomers. During these official stargazing sessions, the astronomers will work with the captain to turn off some of the ship's exterior lights to create the darkness needed for excellent sky-watching. Princess Cruises also offers stargazing as part of its Discovery at Sea programming.

Other cruise lines might bring astronomy lecturers onboard select sailings, and there's a good chance they'll lead a stargazing session onboard. Look for these guest speakers on long sailings or ones with many sea days. You can often find advance information about lecturers on a cruise line's website under the section on enrichment programming.


Maker Challenge Measure the Milky Way with Stars

This cluster can help us measure the Milky Way!

Maker Challenge Recap

For this maker challenge, students move through the engineering design process.  They investigate Python and Jupyter Notebook to analyze real astronomical images in order to calculate the interstellar distance to a star cluster across the Milky Way from our own Solar System. They learn how to write Python code that runs in a Jupyter Notebook so they can determine the brightness of stars in an astronomical image. Next, students complete the functions in the project to determine how far away a single star in the cluster is from Earth. This is a chance to try hands-on astronomical research techniques in the field of aperture photometry. The real astronomical image data will be directly manipulated and analyzed by code the students create. Groups compare their final images and results to answer questions about the astronomy of stars and stellar distances within the Milky Way. Students experience their discoveries the same way Harvard scientist Harlow Shapley first learned the true size and shape of the Milky Way.

Maker Materials & Supplies

  • A computer running Windows, Mac OS X, Linux, or Chrome OS
  • Access to a web browser such as Chrome, Microsoft Edge, or Firefox
  • At least one of the following (tested on all 3):
    • Access to the internet and Microsoft Azure Notebook
    • Install Anaconda Distribution of Python with Jupyter Notebook
    • Access to Google Colaboatory (free access)

    Worksheets and Attachments

    More Curriculum Like This

    Students are introduced to the basic known facts about the universe, and how engineers help us explore the many mysteries of space.

    Kickoff

    Did you know the first person to figure out the size and shape of the Milky Way galaxy, Harlow Shapley, had nothing more than some pictures of stars in far-off star clusters? We can figure out a lot about a given star, including how far it is from us, by analyzing the light it emits. Based on this information, how can we measure astronomical distances? One technique is to use "standard candles," which are astronomical objects that have well-known brightness. (See Resources below for more information). By measuring how bright an object appears to us and knowing the actual brightness from some analysis, we can work out how far the object is from us. This is where the inverse square law comes in.

    The inverse square law is one of the most useful tools in astronomy. The law says that light spreads out as it rushes away from a star such that the brightness of the light decreases by a factor of 1 divided the change in distance squared. How is the inverse square law related to the relation for finding the surface area of a sphere?

    Shapley used a handy tool for a standard candle called RR Lyrae variable stars. We will do the same thing here. A variable star literally swells up and gets brighter and redder and then after a time shrinks again and gets dimmer and bluer. Imagine if the sun became 50% bigger than normal in the morning but by the evening shrink to 50% smaller than normal. It would make Earth a hard place to live. What is the astronomical term we use for the intrinsic brightness of a star? All we need to do is use some clever math and the inverse square law and we can measure distances in the Milky Way once we find one of these variable stars.

    We have five images of a globular cluster full of these RR Lyrae stars. Each image was taken in the same night. If we look at the images as an animation, the RR Lyrae stars are the ones that appear to blink brighter and dimmer. We will choose one and measure its light using some Python code.

    Scientists often have to work on software engineering projects like this. We will write only some new code, but we will mainly take existing code and make it do something new! We will engineer a solution to the given problem using the software tools and techniques available to us.

    This is an interactive programming project called a Jupyter Notebook. There is background information, examples, and live code to run, test, and complete. All of this happens directly in your web browser rather than using a separate application.

    Resources

    • Refer to the Engineering Design Process hub on TeachEngineering to guide your students through the challenge. For design process documentation, utilize the Engineering Design Process Notebook.
    • If students need some background, the free OpenStax Astronomy text is a great choice it contains a section about variable stars as standard candles.
    • Here is an animation of images with the RR Lyrae stars clearly visible as they change brightness.
    • Students can use the free web-based Microsoft Azure Notebook service to complete their project.
    • You can also have students install the Anaconda Distribution on their own Windows, Linux, or Mac computers so they can run the Python-based Jupyter Notebook locally. changing as it shrinks and expands from HubbleESA.
    • Included with the student Jupyter Notebook is a teacher notebook with solutions provided.

    Maker Time

    The best way to start is to dive in! The supplied Jupyter Notebook has some background information, sample code, and the start code for you to complete. Start by loading the Jupyter Notebook on your computer. That might be by uploading the notebook to the Azure Notebook server or by starting Jupyter Notebook on your own computer and opening the starter notebook. We are using the Jupyter Notebook software (either local or online) to edit and write Python code. Python coding is becoming a big part of modern astronomical research. You’re using the same tools as professional astronomers in this activity.

    The challenge here is to complete the code left blank by reading through the example code and working with other students to make your code work as expected. There are questions scattered throughout for you to answer in addition to the code to be completed.

    Read through the background info until you get to the “Coding and Questions” section. Each cell in the Jupyter Notebook will have questions for you to answer as you interact with completed code or code to complete on your own and sometimes both. Don’t forget to test your solutions using the examples provided before moving on to the next cell. You’ll need all the parts to work individually before putting them together as a whole.

    Starter code for finding stellar distances.

    Starter code for processing the images.

    Many of the code cells are meant to be read and then run, but not altered, since they run correctly to start with. Below is a list of the functions to complete and descriptions of the incomplete cells for students to finish. Any code that has an ellipsis (…) needs to be completed.

    • distance_modulus – Function to find the distance of an astronomical object in parsecs if given the apparent (m) and absolute (M) magnitudes of the object. Use some algebra and rearrange the distance modulus equation to return the distance in parsecs of the object. Don't forget how exponents work: x^2 (x squared) would be written as x**2.

    Distance modulus formula: m - M = -5 - log10⁡(d)

    • process_image
      • This function consumes:
        • a filename which can be local or a URL for a FITS file,
        • the starting and ending points marking the bounding box for the image,
        • and whether or not the image needs to be flipped (both vertical and horizontal)
        • the apparent magnitude of the target star
        • Get the image data using the filename and mirror flag.
        • Get the subtracted data and background using the data from step 1
        • Extract a list of sources using the subtracted data, the background, and the given x and y pairs (2 x values and 2 y values).
        • Set the target as the center of the image.
        • Get the flux for our target star.
        • Get the flux for our calibration star.
        • Determine the apparent magnitude of the calibration star.
        • Calibrate the apparent magnitude of the target star.
        • Print and return our target star magnitude.

        The 5 cells that call the “process_image” function will produce a number and also an image. This is image number 5 with the targets selected.

        Example of one of the images post-processing.

        Note that the calibration star magnitude should be around 14.81 for each of the 5 processed images. The magnitude of the target star should vary between about 14.2 at the brightest and 15.5 at the dimmest.

        The distance in the teacher notebook to cluster NGC 3201 yields a distance of 4.87 kpc or 15884 light years. For comparison, the Milky Way is about 100,000 light years across, and the sun is about 25,000 light years from the edge of the Milky Way galaxy.

        Description of cells for students to complete using Jupyter Notebook:

        Wrap Up

        How far away is NGC 3201? According to other researchers, the distance to NGC 3201 is 16 kly or 4.9 kpc. How does your analysis compare?

        Students should share their code and their results with one another. Consider a gallery walk or take volunteers to project the final result from various groups for the class to see. Discuss where difficulties arose and tackle questions about how students’ algorithms compared with one another.

        What would have to change if we selected a new target star? How could we apply what we have done here for a different star cluster?

        • You probably want students to turn on the line numbering in Jupyter Notebook.
        • Have students go to View->Toggle Line Numbers in the menu bar.
        • Software engineering is meant to be a collaborative process. It’s best to treat this activity as a group activity and have groups share ideas and solutions to problems between themselves.

        Copyright

        Contributors

        Supporting Program

        Acknowledgements

        This activity was developed as part of the Research Experience for Teachers through the Office of STEM Engagement and the Department of Electrical and Computer Engineering at Rice University supported by the National Science Foundation under grant number IIS 1730574. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation or Rice University.


        Watch the video: 10 Most Scary SIGNALS From Space (September 2022).