Tag Archives: Space

Exoplanet Explorers Discoveries – A Sixth Planet in the K2-138 System

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.

A Brand New Milky Way Project

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
An EGO shines below a bright star cluster

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).

Screenshot 2013-12-11 21.46.46

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.