The volunteers on our Planet Hunters TESS project have helped discover another planetary system! The new system, HD 152843, consists of two planets that are similar in size to Neptune and Saturn in our own solar system, orbiting around a bright star that is similar to our own Sun. This exciting discovery follows on from our validation of the long-period planet around an evolved (old) star, TOI-813, and from our recent paper outlining the discovery of 90 Planet Hunters TESS planet candidates, which gives us encouragement that there are a lot more exciting systems to be found with your help!
Figure: The data obtained by NASA’s Transiting Exoplanet Survey Satellite which shows two transiting planets. The plot shows the brightness of the star HD 152843 over a period of about a month. The dips appear where the planets passed in front of the star and blocked some of its light from getting to Earth.
Multi-planet systems, like this one, are particularly interesting as they allow us to study how planets form and evolve. This is because the two planets that we have in this system must have necessarily formed out of the same material at the same time, but evolved in different ways resulting in the different planet properties that we now observe.
Even though there are already hundreds of confirmed multi-planet systems, the number of multi-planet systems with stars that are bright enough such that we can study them using ground-based telescopes remains very small. However, the brightness of this new citizen science found system, HD 152843, makes it an ideal target for follow-up observations, allowing us to measure the planet masses and possibly even probe their atmospheric composition.
This discovery was made possibly with the help of tens of thousands of citizen scientists who helped to visually inspect data obtained by NASA’s Transiting Exoplanet Survey Satellite, in the search for distant worlds. We thank all of the citizen scientists taking part in the project who continue to help with the discovery of exciting new planet systems and in particular to Safaa Alhassan, Elisabeth M. L. Baeten, Stewart J. Bean, David M. Bundy, Vitaly Efremov, Richard Ferstenou, Brian L. Goodwin, Michelle Hof, Tony Hoffman, Alexander Hubert, Lily Lau, Sam Lee, David Maetschke, Klaus Peltsch, Cesar Rubio-Alfaro, Gary M. Wilson, the citizen scientists who directly helped with this discovery and who have become co-authors of the discovery paper.
The paper has been published by the Monthly Notices of the Royal Astronomical Society (MNRAS) journal and you can find a version of it on arXiv at: https://arxiv.org/pdf/2106.04603.pdf.
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.
Main-belt asteroid 2001 SE101 passing in front of the Crab Nebula (M1). The streak appears curved due to Hubble’s orbital motion around the Earth. Credit: ESA/Hubble & NASA, M. Thévenot (@AstroMelina); CC BY 4.0
Last week, the European Space Agency released the above Image of the Week from the Hubble Asteroid Hunter project. It shows an asteroid passing in front of the Crab Nebula, M1, an image found in the ESA HST archives by citizen scientist Melina Thevenot, who created a colour image of it.
Hubble Asteroid Hunter was created using our Zooniverse Panoptes platform by a team of researchers from the European Space Agency, and launched on International Asteroid Day (30 June 2019) with the aim of identifying serendipitous observations of asteroids in archival Hubble data. Over the almost three decades of observations, HST provided a vast wealth of images that are available in the archives. Many of these images targeting far away galaxies or clusters contain photobombing asteroids, passing in front of the intended targets (for example asteroids passing in front of Abell 370 cluster in the Hubble Frontier Fields – https://hubblesite.org/contents/media/images/2017/33/4082-Image.html?keyword=Asteroids) . Rather than being a nuisance, astronomers realised that the images can be used to better characterise the asteroids themselves and determine their orbits.
A pipeline was set up in ESA’s discovery portal (ESA Sky – https://sky.esa.int/) that matches the asteroids’ predicted positions in both time and space from the IAU Minor Planet Center database with the European HST archival images. The predicted positions of these objects, nevertheless, have some uncertainties as the ephemerides are not always known to great precision. This is a great opportunity for citizen scientists to inspect Hubble images and mark the positions of the trails. Knowing the exact positions of the trails allows researchers to update the ephemerides of the asteroids, and better characterise their orbits. This is important, especially for Near-Earth Objects, which can be potentially hazardous for the Earth.
So far, over 1900 citizen scientists participated in the project, providing over 300,000 classifications. The project was extended with images from the ecliptic plane to search for potentially unknown asteroids, and with other longer exposure archival images to search for possible past interstellar visitors, such as 2I/Borisov. The volunteers have the chance of exploring beautiful Hubble images of galaxies, clusters and gravitational lenses with these new images!
This is the first of two guest posts from the Exoplanet Explorers research team announcing two new planets discovered by their Zooniverse volunteers. This post was written by Jessie Christiansen.
Hello citizen scientists! We are here at the 233rd meeting of the American Astronomical Society, the biggest astronomy meeting in the US of the year (around 3000 astronomers, depending on how many attendees are ultimately affected by the government shutdown). I’m excited to share that on Monday morning, we are making a couple of new exoplanet announcements as a result of your work here on Zooniverse, using the Exoplanet Explorers project!
Last year at the same meeting, we announced the discovery of K2-138. This was a system of five small planets around a K star (an orange dwarf star). The planets all have very short orbital periods (from 2.5 to 12.8 days! Recall that in our solar system the shortest period planet is Mercury, with a period of ~88 days) that form an unbroken chain of near-resonances. These resonances offer tantalizing clues as to how this system formed, a question we are still trying to answer for exoplanet systems in general. The resonances also beg the question – how far could the chain continue? This was the longest unbroken chain of near first-order resonances which had been found (by anyone, let alone citizen scientists!).
At the time, we had hints of a sixth planet in the system. In the original data analysed by citizen scientists, there were two anomalous events that could not be accounted for by the five known planets – events that must have been caused by at least one, if not more, additional planets. If they were both due to a single additional planet, then we could predict when the next event caused by that planet would happen – and we did. We were awarded time on the NASA Spitzer Space Telescope at the predicted time, and BOOM. There it was. A third event, shown below, confirming that the two previous events were indeed caused by the same planet, a planet for which we now knew the size and period.
So, without further ado, I’d like to introduce K2-138 g! It is a planet just a little bit smaller than Neptune (which means it is slightly larger than the other five planets in the system, which are all between the size of Earth and Neptune). It has a period of about 42 days, which means it’s pretty warm (400 degrees K) and therefore not habitable. Also, very interestingly, it is not on the resonant chain – it’s significantly further out than the next planet in the chain would be. In fact, it’s far enough out that there is a noticeable gap – a gap that is big enough to hide more planets on the chain. If these planets exist, they don’t seem to be transiting, but that doesn’t mean they couldn’t be detected in other ways, including by measuring the effect of their presence on the other planets that do transit. The planet is being published in a forthcoming paper that will be led by Dr Kevin Hardegree-Ullman, a postdoctoral research fellow at Caltech/IPAC.
In the meantime, astronomers are still studying the previously identified planets, in particular to try to measure their masses. Having tightly packed systems that are near resonance like K2-138 provides a fantastic test-bed for examining all sorts of planet formation and migration theories, so we are excited to see what will come from this amazing system discovered by citizen scientists on Zooniverse in years to come!
We are also announcing a second new exoplanet system discovered by Exoplanet Explorers, but I will let Adina Feinstein, the lead author of that paper, introduce you to that exciting discovery.
The Milky Way Project (MWP) is complete. It took about three years and 50,000 volunteers have trawled all our images multiple times and drawn more than 1,000,000 bubbles and several million other objects, including star clusters, green knots, and galaxies. We have produced several papers already and more are on the way. It’s been a huge success but: there’s even more data!
And so it is with glee that we announce the brand new Milky Way Project! It’s got more data, more objects to find, and it’s even more gorgeous.
The new MWP is being launched to include data from different regions of the galaxy in a new infrared wavelength combination. The new data consists of Spitzer/IRAC images from two surveys: Vela-Carina, which is essentially an extension of GLIMPSE covering Galactic longitudes 255°–295°, and GLIMPSE 3D, which extends GLIMPSE 1+2 to higher Galactic latitudes (at selected longitudes only). The images combine 3.6, 4.5, and 8.0 µm in the “classic” Spitzer/IRAC color scheme. There are roughly 40,000 images to go through.
An EGO shines below a bright star cluster
Star Cluster
Beautiful Data
Galaxy
Hollow Shells
The latest Zooniverse technology and design is being brought to bear on this big data problem. We are using our newest features to retire images with nothing in them (as determined by the volunteers of course) and to give more screen time to those parts of the galaxy where there are lots of pillars, bubbles and clusters – as well as other things. We’re marking more objects – bow shocks, pillars, EGOs – and getting rid of some older ones that either aren’t visible in the new data or weren’t as scientifically useful as we’d hoped (specifically: red fuzzies and green knots).
We’ve also upgraded to the newest version of Talk, and have kept all your original comments so you can still see the previous data and the objects that were found there. The new Milky Way Project is teeming with more galaxies, stars clusters and unknown objects than the original MWP.
It’s very exciting! There are tens of thousands of images from the Spitzer Space Telescope to look through. By telling us what you see in this infrared data, we can better understand how stars form. Dive in now and start classifying at www.milkywayproject.org – we need your help to map and measure our galaxy.
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