Pieces of Planets
Today, UVic graduate student Jess Speedie and her supervisor Ruobing Dong have just posted a nice preprint on arXiv where they demonstrate how ALMA can detect spiral structure in the circumstellar disks around young stars that indicate the presence of forming planets. Using hydrodynamic simulations and calculating what the emission from such structure would look like if ALMA were to observe it (at around 850 microns wavelength; Band 7), the paper shows that such spirals can be easily spotted in just a few hours of observation, if they are present. For illustration, attached below is a picture from their simulations, showing the disk with the spiral structure easily seen. At present, however, detection of such spirals by ALMA has been relatively rare, but then again, ALMA observations have tended to be not terribly long because its sensitivity is already so much better than previous facilities at its wavelength range. So, in effect, Jess and Ruobing (along with their collaborator Richard Booth in England) are laying down a case for much longer observations than have been so far the typical length. Indeed, the observatory has been trying to stimulate the community to ask for more time per project, and make even better use of its incredible sensitivity. According to Jess’ models, it’s possible to detect young planets with masses as low as a third of Neptune’s mass, or about six times that of the Earth. Interestingly, a lot of the structure induced by forming planets depends on the contrast between the spiral structure and the underlying disk, and such an indicator can be teased out of the data better by subtracting a model of that underlying disk from the data. Well done, Jess and Ruobing! Here’s a link to the preprint, and the paper itself will be published soon in The Astrophysical Journal.
The disks that Jess and Ruobing are modeling are composed of gas and dust, and the latter clumps together into bigger pieces that form planets. These are called “planetesimals.” Want to own something like that up close? Well, yesterday I came across a website where you can buy a meteorite that seems to have originated from the Moon at least, along with a spiffy book about the Apollo 11 mission called “MoonFire,” written by famed novelist Norman F. Mailer. The book has been published by the Taschen company and according to their website you have to contact them to find out how much it all costs. I suspected that the cost was not going to be low, as only 12 copies of the book + meteorite were made and only three appear to be left on Taschen’s website. Well, fortunately I found a different website with an actual price, CA$1,024,100, which is remarkably precise. What’s that extra $100 for? (The website in question, thisiswhyimbroke.com, showcases a lot of rather expensive gear and is worth checking out for fun.) Even though Valentine’s Day was a few weeks ago, it’s not too late to buy something for the person you tend to moon over, if you have the cash that is. After all, “when the Moon hits your eye, like a big pizza pie, that’s amore,” right? Anyway, maybe this is incredibly overpriced but you get to have bragging rights, I guess. Something to think about if you hit the Lotto 6/49 jackpot this weekend!
From Speedie, Booth, & Dong (2022)