Rubin peers deep into Sextans 

Astronomers would know that Sextans is one of the faintest, dullest constellations in the night sky. The brightest star in the entire constellation is only about magnitude 4.5 and there's not exactly a lot of them!  Not much happening in the that region above our heads and because this, it provide a rare viewport into much deeper space.

When we look toward Sextans, we're looking "out" through our local spiral arm and into intergalactic space, rather than along the flat plane of our galaxy, the pale white river of stars we see on clear nights and simply call the Milky Way.

It means there's a clear view with fewer stars and interstellar dust clouds between us and really, really open space.  Sections of sky that telescopes can stare at for extended periods are called "Deep Fields" and this area in Sextans is referred to as the COSMOS Field. This area of about two square degrees has been extensively studied to learn about how galaxies form, including an extended period of observation with the HST (Hubble Space Telescope). There's been some two million galaxies observed in this region, of all ages. 

Now the 8.4-metre Simonyi Survey Telescope at the NSF–DOE Vera C. Rubin Observatory has peered into the COSMOS Field and released Rubin’s Early Data Preview 2 (EDP2), the first data preview based on observations from the LSST Camera. The EDP2 release covers some 3000 square degrees or around one-sixth of the visible southern sky. The COSMOS Field is no doubt the highlight of the views!

We're used to seeing rich star Milky Way star fields, capturing vast numbers of individual stars and dust clouds. In this new image, with so few Milky Way stars in the foreground, almost all of the points of light we see are not distant suns, but zooming further in reveals them to be individual galaxies. 

Even with so few foreground stars, Rubin's sensitivity picks up faint glowing galactic cirrus, wisps of interstellar dust in our own galaxy. 

Despite the COSMOS Field being observed for more than two decades, it's of immense value for Rubin as it allows further fine tuning of the instrument while also watching for any observable changes. 

“The COSMOS field is a very important one for LSST science,” says Phil Marshall, Deputy Director of Rubin Observatory at SLAC. “Its wealth of prior observations, and its repeated targeting both during commissioning and as one of the LSST’s deep fields, will make it very valuable as a testing ground for scientists as they get ready to take on the survey data.”

Read more here.

Why is the Sun's corona so hot?

A massive Solar Telescope reveals a hidden process on the Sun

Some amazing images coming out the week from the world's largest Solar Telescope, NSF Daniel K. Inouye Solar Telescope near the summit of Maui’s Haleakalā. (We featured this telescope last year in another blog article.)

The U.S. National Science Foundation Daniel K. Inouye Solar Telescope in Maui, Hawaiʻi. Image via: NSF/NSO/AURA/MPS

They confirm the discovery of regions Kelvin-Helmholtz instability (KHI) in the form of small, swirling, intense patterns on the surface of the Sun in regions of magnetic activity. These are visible on the photosphere, which is the lowest layer of the Sun's atmosphere and the part of our nearest star that we actually see. KHI had been theorized for some time, but these observations are their long awaited confirmation. 

“We believe that the discovery of Kelvin-Helmholtz instability in the solar photosphere, backed up by analysis of numerical simulations, is a major step forward in our understanding of the dynamics and evolution of solar and stellar plasma, and will serve as a basis for future discoveries.“ said Dr. David Boboltz, Deputy Director at the National Solar Observatory.

One of the mysteries that has baffled astronomers is while the temperature of the photosphere is approx. 5,500 degrees C, the outer reaches of the Sun or the corona that we can see during total Solar Eclipses like the one in Europe next week or in Australia in 2028 and 2030 can be over a million degrees even though it's much further away.

What appears to be happening is that KHI events causing swirling vortexes around the edges of magnetic regions on the Sun and these vortexes are maybe a key part of the mechanism that increases the temperature of the corona. 

Part of the discovery process used computer simulations of KHI regions that were compared with observations to help confirm astronomer's theories about their formation and structure.  

”Kelvin-Helmholtz instability is likely a mechanism that contributes to the heating of the outer atmosphere and is part of the solution of the longstanding enigma of why stars have a million degrees Kelvin hot corona.” said Dr. Thomas Rimmele, Chief Technologist at the National Solar Observatory.

The Sun is immensely complex and still we're still learning about how our nearest star works. You can read more about the discovery of this hidden Solar process here. 

Korean probe spots the SpaceX rocket impact site on the Moon

You've no doubt heard about a SpaceX Falcon 9 upper-stage rocket booster hitting the Moon during the week. This was used to send the Blue Ghost and Hakuto-R probes to the Moon in 2025.

There were quite a few keen sky watchers keeping an eye out for the impact, but it was always going to be too small and awkward to be spotted from here on Earth with amateur telescopes. ESO reported that astronomers using the Very Large Telescope detected sodium and lithium gas in lunar material thrown up by the roughly 4,000 kg piece of debris, with the plume lasting five to ten minutes after impact.

Korea Aerospace Research Institute images, showing before and after images of the Moon’s surface of there the SpaceX booster impacted this week. Check out their post here.

The region where booster impacted into the surface was spotted by Danuri, a Moon orbiting spacecraft from the Korea Aerospace Research Institute.

Danuri made multiple passes over the site taking from photos from Lunar orbit.

The impact was confirmed in the images. NASA's Lunar Reconnaissance Orbiter (LRO) will pass over the region in the coming month or so and provide better imaging of the crash site. 

Next week: What the El Niño pattern could mean for astronomers over the next few months. 

Cheers,

Earl White

BINTEL

8th August 2026