Yes folks, I said Friday! And this is no normal Friday; it is the Friday of Memorial Day weekend. Any other year I’d be on my way to a Science Fiction convention, and this year I kind of am. The long-running Balticon convention has gone entirely virtual and entirely free. I’ll be tuning in to watch and even giving a couple of presentations. If you are looking for a way to spend your weekend, this may be your answer. Catch it all on Balticon.org.
A lot of podcasts take the summer off and start heading into hiatus around now. We aren’t going to do that to you. We’re here for the duration. That said, we need to do some spring cleaning of our websites, and next week we will only be running a show on Monday. We will be back in a week, with a lot of science to catch up on.
Today’s news isn’t a lot, but it ends with something to look forward to.
Our first story has us looking inward toward the center of the Milky Way galaxy. In 2017, the Atacama Large Millimeter/submillimeter Array (ALMA) stared toward our system’s heart of darkness, Sag A*, a 4 million solar mass black hole. There they found a flicker of light, hanging on, in a mind-breaking orbit. Some small radio emitter has been found orbiting at just 0.2 AU from Sag A*. This is half the size of Mercury’s orbit!
According to team member Tomoharu Oka, “This emission could be related with some exotic phenomena occurring at the very vicinity of the supermassive black hole.” Whatever it is, the emitter is giving us yet one more test of relativity. As the light source orbits Sag A*, relativity says we should see the emission greatly amplified when its motion is moving toward us. It is this amplification they believe is being seen.
This bit of emission probably isn’t anything out of the norm – it is just newly noticed. It is perfectly normal for hotspots to exist in disks of material like the disk around Sag A*. What makes this so cool is that we found it. This is one heck of a challenging observation and analysis, and my hat is off to the team behind this work.
This rapidly orbiting object could be part of what is making the Event Horizon Telescope images so hard to process. Oka goes on to remind us of a problem we’ve all faced in our own photography: “the faster the movement is, the more difficult it is to take a photo of the object.” In this case, we have radio emissions flying across a radio image taken over many hours. I personally can only hope that careful analysis of the time-series images will allow the streaks of emission to be carefully removed.
A lot of people think that astronomy is as simple as taking nice images, looking at them, and then getting good science. The reality is that a whole lot of work goes into processing images to figure out where the science is hiding.
The ATLAS team, for instance, goes to all kinds of measures to find and study comets and asteroids. To find things, they will take image after image of the same field, process them to get the sky levels identical, despite changing moonlight and other factors, and then subtract images from one another so the stars disappear while moving objects pop out to be seen. They will then combine images so that stars appear to streak while moving objects appear as single points that can be more easily seen. These processes are what found the recently self-destructed Comet ATLAS. It is also the process that found asteroid 2019 LD2, an object that refuses to behave as an asteroid should.
Found out near Jupiter last June and classified as a Trojan asteroid, 2019 LD2 grew itself a tiny tail as volatile materials got heated by the sun and pushed away by the solar wind. This tail was confirmed last July, and its development was followed until geometry took this active asteroid out of our view and hid it behind the Sun. Now visible again, the team has once again confirmed that this is an asteroid with a tiny tail, and it has been active for roughly a year. While periodic activity has been observed in other objects, such as the rock-throwing Bennu, this long a period of activity hasn’t been seen before. It is unclear why LD2 is so active, but, to quote the press release, “Maybe Jupiter captured it only recently from a more distant orbit where surface ice could still survive. Maybe it recently suffered a landslide or an impact from another asteroid, exposing ice that used to be buried under layers of protective rock. New observations to find out are being acquired and evaluated.”
The universe is full of surprises, and each new set of observations makes it clear that space is full of things our human minds can’t come up with on their own. This need to see what is out there is part of why we robotically explore, and our team is really looking forward to one piece of exploration that is scheduled for this fall. We are super pleased to share that the OSIRIS-REx mission is now scheduled to collect materials from the surface of the asteroid Bennu on October 20, and the material will be collected from the Nightingale site. When this happens, we will bring it to you live, right here on Twitch.tv/CosmoQuestX.
But for now, this is all we have for today.
ALMA Spots Twinkling Heart of Milky Way
- ALMA Observatory news article
- “Time Variations in the Flux Density of Sgr A* at 230 GHz Detected with ALMA,” Yuhei Iwata et al., 2020 April 2, Astrophysical Journal Letters (Preprint on arxiv.org)
UH ATLAS telescope discovers first-of-its-kind asteroid
NASA’s OSIRIS-REx Ready for Touchdown on Asteroid Bennu
Written and Hosted by Pamela Gay
Audio and Video Editing by Ally Pelphrey
Content Editing by Beth Johnson
Intro and Outro music by Kevin MacLeod, https://incompetech.com/music/