Our First Paper: the Discovery of Brown Dwarf WISEA 1101+5400

Our first paper was published in the Astrophysical Journal Letters, Volume 841, Number 2 on May 24.   Hooray!!   (It may be easier to read here.)

The paper announces the discovery of our first brown dwarf, shows a spectrum we took of the brown dwarf, and describes the Backyard Worlds: Planet 9 project. There’s a press release from the American Museum of Natural History, a nice NPR story about it featuring Rosa Castro, and several other news stories.

Of course, this paper is already out-of-date.  In the time it took to write the paper, you’ve discovered at least twelve more good brown dwarf candidates.  And we used those discoveries to make an even better estimate of the sensitivity of our search than the one that appears in the paper. But let’s talk more about the paper and our first discovery, a source called WISEA 1101+5400 which we now know is a real brown dwarf, spectral type T5.5.   Here is WISEA 1101+5400’s flipbook.

You may recall that shortly after launch, we were all excited about a faint dipole/mover, which Bob Fletcher had flagged on talk and Tamara Stajic reported on the Think-You’ve-Got-One form.  That’s WISEA 1101+5400.  A few weeks later, science team member Jackie Faherty nabbed a spectrum of it using NASA’s Infrared Telescope Facility.  Here’s a nice plot of the spectrum, created by science team member Joe Filippazzo comparing the our object’s spectrum (black) to the spectrum of another T5.5 brown dwarf (red).  It’s a great match! The extra wiggles in our spectrum are simply noise.

Figure3.cropped

The quality of the match demonstrates that WISEA 1101+5400 is indeed a brown dwarf, and tells us that its temperature is in the range 900-1500 Kelvin (1200 – 2200 degrees Fahrenheit).  We can tell the temperature range by looking at what molecules show up in the spectrum.  The spectrum shows features associated with water, methane, iron hydride, potassium, and molecular hydrogen, labelled above.  If the brown dwarf were hotter or cooler, the relative sizes of the dips in the spectrum from each molecule would be different.

Knowing the brown dwarf’s spectral type also teaches us roughly how bright it is, intrinsically.  And since we know that the brightness of an astronomical object falls off as the inverse distance to it, squared, we can compare our images of WISEA 1101+5400 to those of other brown dwarfs to estimate its distance:  roughly 34 parsecs or about 111 light years.  For comparison, the closest known brown dwarf is the binary Luhman 16AB at 6.59 light years.

So what does this discovery mean for our understanding of brown dwarfs?  Well, there are already a few hundred T dwarfs known–and this new one turns out to be somewhat run-of-the mill.  It’s not super cool, and it’s not in a moving group, for example.  Its infrared colors are close to the average colors for brown dwarfs with this spectral type.  So we haven’t shattered any paradigms or broken any records with this object just yet.

But the discovery is a dramatic proof-of-concept.  Just the fact that we found it, only six days after launch, shows that we’re on the right track toward lots more discoveries.  Also, Zooniverse founder Chris Lintott tells me that our paper now holds the record for fastest publication from a Zooniverse project.   How cool is that?

This is a moment to celebrate.  Congratulations to us!!   Let’s make some more discoveries and write some more papers together.

Marc

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