Category Archives: Results

New Results for Milky Way Project Yellowballs!

What are “Yellowballs?” Shortly after the Milky Way Project (MWP) was launched in December 2010, volunteers began using the discussion board to inquire about small, roundish “yellow” features they identified in infrared images acquired by the Spitzer Space Telescope. These images use a blue-green-red color scheme to represent light at three infrared wavelengths that are invisible to our eyes. The (unanticipated) distinctive appearance of these objects comes from their similar brightness and extent at two of these wavelengths: 8 microns, displayed in green, and 24 microns, displayed in red. The yellow color is produced where green and red overlap in these digital images. Our early research to answer the volunteers’ question, “What are these `yellow balls’?” suggested that they are produced by young stars as they heat the surrounding gas and dust from which they were born. The figure below shows the appearance of a typical yellowball (or YB) in a MWP image.  In 2016, the MWP was relaunched with a new interface that included a tool that let users identify and measure the sizes of YBs. Since YBs were first discovered, over 20,000 volunteers contributed to their identification, and by 2017, volunteers catalogued more than 6,000 YBs across roughly 300 square degrees of the Milky Way. 

New star-forming regions. We’ve conducted a pilot study of 516 of these YBs that lie in a 20-square-degree region of the Milky Way, which we chose for its overlap with other large surveys and catalogs. Our pilot study has shown that the majority of YBs are associated with protoclusters – clusters of very young stars that are about a light-year in extent (less than the average distance between mature stars.) Stars in protoclusters are still in the process of growing by gravitationally accumulating gas from their birth environments. YBs that represent new detections of star-forming regions in a 6-square-degree subset of our pilot region are circled in the two-color (8 microns: green, 24 microns: red) image shown below. YBs present a “snapshot” of developing protoclusters across a wide range of stellar masses and brightness. Our pilot study results indicate a majority of YBs are associated with protoclusters that will form stars less than ten times the mass of the Sun.

YBs show unique “color” trends. The ratio of an object’s brightness at different wavelengths (or what astronomers call an object’s “color”) can tell us a lot about the object’s physical properties. We developed a semi-automated tool that enabled us to conduct photometry (measure the brightness) of YBs at different wavelengths. One interesting feature of the new YBs is that their infrared colors tend to be different from the infrared colors of YBs that have counterparts in catalogs of massive star formation (including stars more than ten times as massive as the Sun). If this preliminary result holds up for the full YB catalog, it could give us direct insight into differences between environments that do and don’t produce massive stars. We would like to understand these differences because massive stars eventually explode as supernovae that seed their environments with heavy elements. There’s a lot of evidence that our Solar System formed in the company of massive stars.

The figure below shows a “color-color plot” taken from our forthcoming publication. This figure plots the ratios of total brightness at different wavelengths (24 to 8 microns vs. 70 to 24 microns) using a logarithmic scale. Astronomers use these color-color plots to explore how stars’ colors separate based on their physical properties. This color-color plot shows that some of our YBs are associated with massive stars; these YBs are indicated in red. However, a large population of our YBs, indicated in black, are not associated with any previously studied object. These objects are generally in the lower right part of our color-color plot, indicating that they are less massive and cooler then the objects in the upper left. This implies there is a large number of previously unstudied star-forming regions that have been discovered by MWP volunteers. Expanding our pilot region to the full catalog of more than 6,000 YBs will allow us to better determine the physical properties of these new star-forming regions.

Volunteers did a great job measuring YB sizes!  MWP volunteers used a circular tool to measure the sizes of YBs. To assess how closely user measurements reflect the actual extent of the infrared emission from the YBs, we compared the user measurements to a 2D model that enabled us to quantify the sizes of YBs. The figure below compares the sizes measured by users to the results of the model for YBs that best fit the model. It indicates a very good correlation between these two measurements. The vertical green lines show the deviations in individual measurements from the average. This illustrates the “power of the crowd” – on average, volunteers did a great job measuring YB sizes!

Stay tuned…  Our next step is to extend our analysis to the entire YB catalog, which contains more than 6,000 YBs spanning the Milky Way. To do this, we are in the process of adapting our photometry tool to make it more user-friendly and allow astronomy students and possibly even citizen scientists to help us rapidly complete photometry on the entire dataset.

Our pilot study was recently accepted for publication in the Astrophysical Journal. Our early results on YBs were also presented in the Astrophysical Journal, and in an article in Frontiers for Young Minds, a journal for children and teens.

SuperWASP Variable Stars – Update

The following is an update from the SuperWASP Vairable Stars research team. Enjoy!

Welcome to the Spring 2020 update! In this blog, we will be sharing some updates and discoveries from the SuperWASP Variable Stars project.

What are we aiming to do?

We are trying to discover the weirdest variable stars!

Stars are the building blocks of the Universe, and finding out more about them is a cornerstone of astrophysics. Variable stars (stars which change in brightness) are incredibly important to learning more about the Universe, because their periodic changes allow us to probe the underlying physics of the stars themselves.

We have asked citizen scientists to classify variable stars based on their photometric light curves (the amount of light over time), which helps us to determine what type of variable star we’re observing. Classifying these stars serves two purposes: firstly to create large catalogues of stars of a similar type which allows us to determine characteristics of the population; and secondly, to identify rare objects displaying unusual behaviour, which can offer unique insights into stellar structure and evolution.

We have 1.6 million variable stars detected by the SuperWASP telescope to classify, and we need your help! By getting involved, we can build up a better idea of what types of stars are in the night sky.

What have we discovered so far?

We’ve done some initial analysis on the first 300,000 classifications to get a breakdown of how many of each type of star is in our dataset.

So far it looks like there’s a lot of junk light curves in the dataset, which we expected. The programme written to detect periods in variable stars often picks up exactly a day or a lunar month, which it mistakes for a real period. Importantly though, you’ve classified a huge number of real and exciting light curves!

We’re especially excited to do some digging into what the “unknown” light curves are… are there new discoveries hidden in there? Once we’ve completed the next batch of classifications, we’ll do some more to see whether the breakdown of types of stars changes.

An exciting discovery…

In late 2018, while building this Zooniverse project, we came across an unusual star. This Northern hemisphere object, TYC-3251-903-1, is a relatively bright object (V=11.3) which has previously not been identified as a binary system. Although the light curve is characteristic of an eclipsing contact binary star, the period is ~42 days, notably longer than the characteristic contact binary period of less than 1 day.

Spurred on by this discovery, we identified a further 16 candidate near-contact red giant eclipsing binaries through searches of archival data. We were excited to find that citizen scientists had also discovered 10 more candidates through this project!

Figure 1: Artist’s impression of a contact binary star [Mark A. Garlick] Over the past 18 months, we’ve carried out an observing campaign of these 27 candidate binaries using telescopes from across the world. We have taken multi-colour photometry using The Open University’s own PIRATE telescope, and the Las Cumbres Observatory robotic telescopes, and spectroscopy of Northern candidates with the Liverpool Telescope, and Southern candidates using SALT. We’ve also spent two weeks in South Africa on the 74-inch telescope to take further spectroscopy.

Of the 10 candidate binaries discovered by citizen scientists, we were happy to be able to take spectroscopic observations for 8 whilst in South Africa, and we have confirmed that at least 2 are, in fact, binaries! Thank you citizen scientists!

Why is this discovery important?

Figure 2: V838 Mon and its light echo [ESA/NASA]

The majority of contact or near-contact binaries consist of small (K/M dwarf) stars in close orbits with periods of less than 1 day. But for stars in a binary in a contact binary to have such long periods requires both the stars to be giant. This is a previously unknown configuration…

Interestingly, a newly identified type of stellar explosion, known as a red nova, is thought to be caused by the merger of a giant binary system, just like the ones we’ve discovered.

Red novae are characterised by a red colour, a slow expansion rate, and a lower luminosity than supernovae. Very little is known about red novae, and only one has been observed pre-nova, V1309 Sco, and that was only discovered through archival data. A famous example of a possible red nova is the 2002 outburst in V838 Mon. Astronomers believe that this was likely to have been a red nova caused by a binary star merger, forming the largest known star for a short period of time after the explosion.

So, by studying these near-contact red giant eclipsing binaries, we have an unrivalled opportunity to identify and understand binary star mergers before the merger event itself, and advance our understanding of red novae.

What changes have we made?

Since the SuperWASP Variable Stars Zooniverse project started, we’ve made a few changes to make the project more enjoyable. We’ve reduced the number of classifications needed to retire a target, and we’ve also reduced the number of classifications of “junk” light curves needed to retire it. This means you should see more interesting, real, light curves.

We’ve also started a Twitter account, where we’ll be sharing updates about the project, the weird and wacky light curves you find, and getting involved in citizen science and astronomy communities. You can follow us here: www.twitter.com/SuperWASP_stars

What’s next?

We still have thousands of stars to classify, so we need your help!

Once we have more classifications, we will be beginning to turn the results into a publicly available, searchable website, a bit like the ASAS-SN Catalogue of Variable Stars (https://asas-sn.osu.edu/variables). Work on this is likely to begin towards the end of 2020, but we’ll keep you updated.

We’re also working on a paper on the near-contact red giant binary stars, which will include some of the discoveries by citizen scientists. Expect that towards the end of 2020, too.

Otherwise, watch this space for more discoveries and updates!

We would like to thank the thousands of citizen scientists who have put time into this Zooniverse project. If you ever have any questions or suggestions, please get in touch.

Heidi & the SuperWASP Variable Stars team.

28 New Planet Candidates Discovered on Exoplanet Explorers

The team behind the Exoplanet Explorers project has just published a Research Note of the American Astronomical Society announcing the discovery of 28 new exoplanet candidates uncovered by Zooniverse volunteers taking part in the project.

Nine of these candidates are most likely rocky planets, with the rest being gaseous. The sizes of these potential exoplanets range from two thirds the size of Earth to twice the size of Neptune!

This figure shows the transit dips for all 28 exoplanet candidates. Zink et al., 2019

You can find out more about these exoplanet candidates in the actual research note at https://iopscience.iop.org/article/10.3847/2515-5172/ab0a02, and in this blog post by the Exoplanet Explorers research team http://www.jonzink.com/blogEE.html.

Finally, both the Exoplanet Explorers and Zooniverse teams would like to extend their deep gratitude to all the volunteers who took part in the project and made these amazing discoveries possible.