42 Confirmed Brown Dwarfs and Counting

Hey everybody!   Thanks to your efforts, we’re now up to 879 brown dwarf candidates.  Wow.  We’ve been following up your discoveries as fast as we can, getting spectra to determine their spectral types and distances, test for membership in moving groups, and look for unusual features. For the coolest objects, we’ve also been working on taking new images.  Here’s a little update on all this follow-up work.

First of all, we have a big stack of new spectra. Jackie Faherty confirmed 17 of our brown dwarf candidates with the ARCoIRIS spectrograph on the Blanco 4m telescope in Chile, and Jonathan Gagné, Jackie Faherty and Michaela Allen observed another batch of 8 targets with the SpeX spectrograph on NASA’s Infrared Telescope Facility (IRTF).  Of those 8 we observed with IRTF, 6 are brown dwarfs. The other two are late Ms; one has a co-mover (spotted by Tadeas Cernohous) and the other has an unusual J band flux that threw off our initial spectral type estimate.

Picture of Michaela Allen’s desk at NASA Goddard Space Flight Center while she was observing our brown dwarf candidates remotely with the IRTF telescope.

That’s right, Michaela, our TALK moderator, is now participating in observing runs! Michaela is spending her summer as a NASA intern here at Goddard Space Flight Center in exotic Greenbelt, Maryland.  She’s working on our Gemini data, and looking through the long long list of moving objects you have found that did not appear, at first glance, to be brown dwarfs.  You can follow her on Twitter @sasstronaut42 to find out more about how her summer is going, and you’ll hear more about her work later on.

Thanks to Jackie, Jonathan and Michaela’s hard work, I can now say that we have confirmed a total of 42 brown dwarfs.  These confirmed objects include 10 L dwarfs and 32 T dwarfs.  Of these, fourteen are closer than 20 parsecs, and four are closer than 15 parsecs. Congrats to Nikolaj Stevnbak Andersen, Dan Caselden, Guillaume Colin, Sam Goodman,  and Melina Thevenot, whose TYGO form submissions were observed with ARCOIRIS and confirmed to be brown dwarfs!   And congrats to Nikolaj Stevnbak Andersen, Dan Caselden, Tadeas Cernohous and Guillaume Colin, whose TYGO submissions were observed with IRTF and confirmed to brown dwarfs!  I believe those are Nikolaj’s, Tadeas’s and Melina’s first brown dwarf discoveries.

The “seeing” at IRTF was only about 0.8 arcseconds, which is poor for that site, and there were thin cirrus clouds. So we were only able to take decent spectra of objects brighter than about 16th magnitude in J band.  So this run was a bit disappointing.  But just today we learned that we won four more nights on IRTF this fall! 

In fact, here’s a summary of our follow-up program so far—where we’ve been an where we’re going.    The “R” value is the spectral resolution of the spectrograph we’re using. R = the central wavelength of the spectrum divided by the smallest difference in wavelengths the spectrograph can distinguish.   So larger R means finer resolution.  But finer resolution comes at a cost; you need to collect more light to begin with if you’re going to spread it out more by wavelength.

Table 1. Status of our follow-up observing program.
Gemini-North/NIRI Fast Turnaround J/K band imaging 9.2 hours, 16 targets Images of 16 targets obtained
Magellan/FIRE Prism R~450 17 targets Spectra of 17 targets obtained
Apache Point Observatory (APO)/Triplespec R~3500 1 night Bad weather, spectra of 2 targets obtained
Blanco 4 m/ARCoIRIS R~3500 2 nights Spectra of 17 BDs obtained (see above!)
Magellan/FIRE Echelle R~7000 1 target Spectrum of 1 target obtained 2/3/18, RV measured
Infrared Telescope Facility (IRTF)/SpeX R~150 2 nights, 20 targets 1 night weathered out, spectra of 8 targets obtained during second night (see above!)
HST/WFC3 F125W/F105W imaging 5 orbits, 5 targets Awarded 5 orbits
Mont Mégantic/CPAPIR J-band imaging 8.5 hours, 60 targets

 

Awarded time to observe 60 targets. Images of 12 obtained May 2018
Magellan/FIRE Prism

 

R~450 1 night, 20 targets Awarded 1 night in 2018B
Keck/NIRES

 

R~2700

 

1.5 nights, 10 targets Awarded 1.5 nights in 2018B
Spitzer

 

3.6 and 4.5 micron imaging 26.8 hours, 65 targets Awarded 26.8 hours
Infrared Telescope Facility (IRTF)/SpeX R~150 4 nights, 40 targets Awarded 4 nights in 2018B
Gemini-South/Flamingos 2 R~600 13.7 hours, 27 targets Proposal Submitted, Pending
Magellan/FourStar J-band imaging 1 night, 8 targets Proposal Submitted, Pending
Gemini-North/GNIRS R~11,800 9.4 hours, 5 targets Proposal Submitted, Pending

Keep up the amazing work!  And stay tuned for more cool discoveries!!

Marc

 

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Guest Blog Post by Peter Jalowiczor

(One of our volunteers, Peter Jalowiczor, gave a talk about Backyard Worlds: Planet 9 at his own astronomy club.  Today’s informative blog post is his report about the experience. Did you know that brown dwarfs get smaller the more massive they are?  Read on. -Marc)

I had the pleasure to give a talk at one of the UK’s leading Astronomical Societies: the MSAS (the Mexborough and Swinton Astronomical Society). The society is situated ~20 km from Sheffield (pop, 570,000) in England and was founded in 1978.  Every Thursday evening is a great social occasion centred on a lecture.  At least once a month, some academic visits the society to present on an aspect of Astronomy. Academics really enjoy visiting and describe this place as an Aladdin’s cave as may be seen by some of the photos!

2018 146 MSAS Presentation
The first slide of Peter’s presentation.

The evening was divided-up into two parts consisting of two completely different presentations. One sent by Marc specially for the occasion and the other prepared weeks in advance by myself. They turned out to complement each other perfectly (thank you Marc!). You’re welcome, Peter! -Marc

  1. The First Presentation

I started with an introduction to the Science team and the important fact that Planet Nine is presumed to exist. It is estimated to be around 10 Earth masses, on an elliptical orbit, averaging a=700 AU because of visible disruption in the orbits of detached Kuiper Belt Objects. Next, the nearest neighbours to the Sun were discussed with examples of these BD systems and the prizes of participating in BYW:P9 included discovering such objects.

The flipbook was introduced followed by examples of what to mark and what not to mark: the submissions procedure. How this would be related to the Astronomical software/ procedures described in the second presentation blended both presentations ideally.

The successes of BYW:P9 include the discovery of a T Dwarf in the first few days of the project!

2018 166 MSAS Presentation
Members of the Mexborough and Swinton Astronomical Society, enjoying Peter’s presentation, and thinking up tough questions (see below).
  1. The Second Presentation

I started with a comprehensive description of brown dwarfs, with the three main categories and their associated spectral classes; this culminated in a review of the mass-radius relationship from solar-type stars to the terrestrial planets (G. Chabrier et. al., 2008). A chart demonstrated the decrease (compression) of BD radii with mass before the critical mass is reached as a BD turns into a star. After this point the radius increases dramatically. The positions of L, T and Y objects and sub-BD objects was discussed down to Jovian mass.

MassRadiusdiagram
Mass-radius diagram for planet, brown dwarfs and low-mass stars, from Fortney, Baraffe and Militzer 2014.  More massive brown dwarfs are slightly smaller than less massive ones.

 

Second, I a gave detailed description of the 2MASS project and the WISE mission, the wavebands in which the detectors operated and the positions of the IR bands on the electromagnetic spectrum. 2MASS: j=1.235um, h=1.662um, k=2.159um. WISE: W1=3.4um, W2=4.6um, W3= 12um, W4=22um. I showed that WISE goes much deeper than 2MASS into the Mid-Infrared.

Third, I gave a complete overview of the astronomical tools used: the Backyard Worlds: Planet 9 flipbook, which is at the heart of the project, SIMBAD, VizieR, IRSA Finderchart and BYE Tools (Wiseview).

Fourth, I showed a home video of how everything comes together.

Fifth, I described the project’s results by showing a presentation of the spreadsheet that has been built-up. I described how the photometry of 2MASS and WISE come into this, i.e., W1-W2, J-W2 and how these differences can be used to constrain the spectral types of objects. I referred to photometric Brown Dwarf classification charts from Skrzypek, N., et al.,

I showed clips from Backyard Worlds: Planet 9 Hangouts to demonstrate the international calibre of this project, which put on a completely different light on everything.

Illustration of the spectral coverage provided by the DustPedia database, showing filter response functions of all bands for which we present data. As can be seen, the data we employ effectively provides complete sampling of over five orders of magnitude in wavelength. Response functions of the bands for which we present both imagery and aperture-matched photometry are traced with solid lines. Bands for which we present supplementary external photometry are traced with dashed lines. Bands for which we present imagery only are traced with dotted lines.
The spectral bands used by 10 different survey telescopes. 2MASS (blue) and WISE (leftmost greeen) are the surveys we use in Backyard Worlds: Planet 9.

And finally!

  • The principle aims of the project are to discover Brown Dwarfs and Planet Nine. Red Dwarfs are a secondary target and are being catalogued.
  • Volunteers are encouraged to distinguish real celestial objects from image artefacts in data from NASA’s WISE mission
  • roughly 5 million classifications of images from NASA’s WISE telescope.
  • 432 objects of interest for the follow up campaign, mostly newly discovered BD candidates. We now have more than 500!  -Marc
  • Planet Nine has remained elusive, as have Planet X and Tyche (instruments are sensitive to gas giants out to about 50,000 astronomical units from the Sun).

Peter Jalowiczor

There was also Question and Answer Session at the end of the lecture.  I’ve attempted to answer some of the questions. –Marc

Q: What causes the ‘ghosts’/artefacts in the images?

A: Though the optics in the WISE telescope are first rate, they are not perfect; some black surfaces are not perfectly black, and some transparent optics are partly reflective.  As a result, the light from particularly bright stars can create secondary images from bouncing around more than, ideally, it should.  Those appear as artifacts and ghosts.  –Marc

Q: The candidates submissions procedure. If it is listed in a Red Dwarf catalog. There seemed to be contradiction in what I said and what seemed to implied by the project. (e.g. I don’t submit a candidate if it is listed in a Red Dwarf catalog in VizieR). Whereas there could be objects listed in Red Dwarf catalogues that are misclassified? Should such objects be submitted or not? It would save time for the user.

A: The rule is: if it’s moving and it’s not in SIMBAD (and not a ghost or star or other artifact), please submit it to the Think-You’ve-Got-One form. Sorry for the confusion!  -Marc

Q: Brown Dwarfs or Brown Dwarves? One member picked-up on this after I used this (I was using Brown Dwarfs). It turns out that Dwarfs is American English and Dwarves is British English. I was ‘instructed’ to write properly!

A:  I’m no expert on British English, but perhaps you could consult with the Extrasolar Planets and Brown Dwarfs group at the University of Hertfordshire

Thank you, Peter, for being such a compelling ambassador for Backyard Worlds: Planet 9, and for composing this delightful blog post. –Marc

BYWP9 Peter Jalowiczor
Pete at his computer working on Backyard Worlds: Planet 9.