Let’s jump out to look at a big galaxy in the Hubble Deep Field.

As we head into year two of pandemic lockdown, I for one know it’s time to buy new yoga pants in maybe a size larger. Let’s face it, sometimes things just grow, but before any of us should start to feel bad about our personal mass enhancements, we need to put everything in perspective: no matter how many random Oreos I may eat, my gains are insignificant compared to those of galaxies in the early universe.

Back in 1995, the Hubble Space Telescope pointed at what was believed to be one of the blankest regions of the sky for ten days. The goal was to see what faint objects might be out there, otherwise lost in the light of all the nearer or brighter objects. The answer was galaxies; this tiny field contains over 3000 galaxies, and one of those galaxies, HDF850.1, is a massive star-forming system 12.5 billion light-years away. This galaxy is putting out stars at a rate of a few hundred per year; this is the highest known star formation rate ever seen. 

A new paper by Rosa Calvi and company in Monthly Notices of the Royal Astronomical Society looks at the environment around HDF850.1 and finds 23 observable companions in a complex structure around it. These systems are thought to be just the brightest members of a massive galaxy cluster forming in the early universe. Over time, these galaxies will interact and move together to form a cluster that, if we could see it as it appears today, would look something like the nearby Virgo Galaxy Cluster. Put another way, this massive system is so massive that it has gravitationally pulled in its neighbors while spitting out hundreds of stars a year.

I suddenly feel better about my personal growth over the last year.

From massive galaxies, we now turn toward massive stars and an easy-sounding problem that has turned out to be quite hard. Also, this research article came with a really pretty picture we wanted to share. Long story short, researchers have been struggling to find ways to accurately measure the temperatures of red giant stars like Betelguese in a consistent manner. These stars have complex atmospheres that are highly variable, and many of the normal ways we have for measuring a star’s temperature don’t work so well with that chaotic atmosphere. We need to know stellar temperatures, however, to make sure our models describing how these stars live and die as violent supernovae are correct. 

Iron has come to the rescue. This particular atom can be found in the outer parts of stars and is highly sensitive to temperature. Like all atoms, iron absorbs light at specific colors, and how much light it absorbs at each color depends on temperature. By comparing how much light is absorbed at different colors, researchers from the University of Tokyo have been able to accurately measure the temperatures of red giants and determine that theory and reality match nicely.

As for this stunning image, that red asterisk of light is the star Betelgeuse. Next time you look at the constellation Orion, know that the entire region is rich in these clouds of star formation, and the stars we see are just the brightest sampling of what’s out there.

What we see with our eyes is just the faintest tracing of everything going on in the sky, and it’s often the accidental discoveries that are the most memorable. Recently, researchers using the Juno mission’s Ultraviolet Spectrograph were purposely observing aurorae around Jupiter when they accidentally observed a bright meteoroid explode in Jupiter’s atmosphere. The explosion took place about 140 miles above Jupiter’s cloud tops, and its brightness was consistent with an object between 550 and 3300 pounds. Basically, a car-sized rock exploded above Jupiter and was accidentally caught on camera in the process.

We used to think these kinds of events were rare, with the 1994 impact of Shoemaker-Levy 9 being the first broadly observed impact. We’re now learning they aren’t so much rare as generally brief, and unless you happen to be watching Jupiter at just the right moment, they tend to go unnoticed. Remarkably, most impacts are spotted by amateur astronomers. You never know exactly what you could discover by looking up.

And sometimes, you have to look down to understand what you might someday find when you look up. Researchers from the University of Rhode Island’s Graduate School of Oceanography have published a new paper in Nature Communications describing how life living beneath the seafloor can survive off chemicals released through radioactive reactions. Specifically, naturally occurring radiation can split water molecules into hydrogen and oxidants, and this process is much more effective in seafloor sediment than in open water.

According to Steven D’Hondt, a co-author of this study: If you can support life in subsurface marine sediment and other subsurface environments from natural radioactive splitting of water, then maybe you can support life the same way in other worlds. Some of the same minerals are present on Mars, and as long as you have those wet catalytic minerals, you’re going to have this process. If you can catalyze production of radiolytic chemicals at high rates in the wet Martian subsurface, you could potentially sustain life at the same levels that it’s sustained in marine sediment.

As a reminder, marine sediment is extremely rich in microbial and other life, implying Mars could be rich in tiny lifeforms just waiting to be found.

Percy, we’re looking at you. Please go find fossils of past life that will let us know if we should go looking for current life.

More Information

Largest Cluster of Galaxies in Early Universe Discovered

• IAC press release
• “Probing the existence of a rich galaxy overdensity at z = 5.2,” Rosa Calvi et al., 2021 January 5, Monthly Notices of the Royal Astronomical Society

Accurately Measuring Temperatures of Red Supergiants

• The University of Tokyo press release
• “Effective temperatures of red supergiants estimated from line-depth ratios of iron lines in the YJ bands, 0.97-1.32μm,” Daisuke Taniguchi et al., 2021 February 28, Monthly Notices of the Royal Astronomical Society

An Accidental Image of a Meteoroid Explosion at Jupiter

• SwRI press release
• “Detection of a Bolide in Jupiter’s Atmosphere With Juno UVS,” Rohini S. Giles et al., 2021 February 9, Geophysical Research Letters

Microbes Beneath Seafloor Survive on Radioactivity

• The University of Rhode Island press release
• “The contribution of water radiolysis to marine sedimentary life,” Justine F. Sauvage et al., 2021 February 26, Nature Communications