I'm sorry for the super late Night Sky article this month (and for the lack of posts in general recently)! I've been in California these past few weeks visiting Caltech, continuing my work with Professor Lynne Hillenbrand. I had a really really lovely time, and also made lots of progress on our project :) 

JWST anniversary !

The 12th of July marked the 1 year anniversary of the first 5 images released by NASA/ESA from the James Webb Space Telescope mission. To celebrate this occasion, NASA/ESA have released another stunning image – this time of the Rho Ophiuchi cloud complex, the closest star-forming region to Earth. As you can see above, it looks out of this world!

Webb’s image shows a region containing approximately 50 young stars, all of them similar in mass to our Sun, or smaller. The darkest areas are the densest, where thick dust surrounds forming protostars. Huge jets of molecular hydrogen (represented in red) dominate the image, appearing horizontally across the upper third and vertically on the right. These occur when a star first bursts through its natal envelope of cosmic dust, shooting out a pair of opposing jets into space like a newborn first stretching her arms out into the world. In contrast, the star S1 has carved out a glowing cave of dust in the lower half of the image. It's the only star in the image that is significantly more massive than the Sun.

Saturn through the eyes of JWST

Saturn is just so so beautiful! This new image shows lots of detail within its ring system, along with several of the planet's moons – Dione, Enceladus, and Tethys. Additional deeper exposure images will allow scientists to probe some of Saturn's fainter rings, not visible in the image above, including the thin G ring and the diffuse E ring.

Saturn's rings are made up of an array of rocky and icy fragments – the particles range in size from a grain of sand to a few as large as mountains on Earth. Researchers recently used Webb to explore Enceladus and found a large plume jetting from the southern pole of the moon that contains both particles and plentiful amounts of water vapour (check out last month's article for more deets).

CEERS

JWST's CEERS survey involves using the fancy new telescope to find the most distant galaxies in our universe. Finkelstein et al used an image produced by the survey to measure the redshift of Maisie's Galaxy. Using still images to determine galactic distance is a bit dodgy and we should take this result with a grain of salt, but they determined the redshift to be z=11.8, corresponding to the galaxy hanging around when our universe was just 370 million years old. Recent results from JWST have led some researchers to believe that our universe is a lot older than we initially thought (i.e., Rajendra P Gupta, 2023) – I'll discuss these results in a future post.

Another paper published in July using the CEERS data claims to have found the most distant galaxy with a growing supermassive black hole (SMBH) in its centre (known as an active galactic nuclei (AGN) or quasar). This seems to be slightly older than Maisie's Galaxy (by ~200 million years), but it's still a really big deal. One of the big open questions in modern astrophysics is: when and how do the first SMBHs form in our universe? The only process that we know of which can create a black hole is if a star goes supernova. For that to be the case here, however, the physical limit at which a black hole can grow by would be violated. People are now speculating that maybe there's another way to make a black hole in the super early universe – for example, gas clouds collapsing and forming black holes rather than stars; there's actually Hubble Telescope data which supports this hypothesis.

Larson et al came to the conclusion that a SMBH resides in this galaxy by analysing its spectra. When the gas which emits the analysed light is moving, the peaks seen on a typical spectra get smeared out as the radiated electromagnetic wave gets Doppler shifted – this is what we see happen in closeby SMBHs. The potential caveat here is that Larson et al reached their conclusions by assuming that SMBHs in the present universe behave in the same way as those in the earlier universe. The spectral patterns that we're seeing could just be due to stellar activity rather than black hole activity. The only way to know for sure is to travel back in time and visit this mysterious galaxy :)

Voyager 2

In the month of July, a wrong command was somehow sent to the Voyager 2 probe, changing its position and severing contact 🫥. After comms were lost, the probe was unable to receive any commands or send back any data to NASA's Deep Space Network.

A happy ending 🥳: on the 4th of August, NASA confirmed that connection with Voyager 2 was restored! Whew.

July/August meteor showers

July and August are all about meteor showers! In case you're unfamiliar, a meteor shower is when the Earth passes through clouds of debris left behind by comets and that debris burns up in the Earth's atmosphere as a 'shooting star'.

The Delta Aquariids meteor shower is running from ~12th July till 23rd August, with the peak on 29th July. The Perseids meteor shower is taking place from ~17th July through August and is one of the brightest meteor showers of the year! In the darkest of skies, it produces around 60 meteors per hour (approx 1 meteor per minute)! It's expected to peak on the 13th-14th of August.

Summer triangle

If you're out stargazing this month, make sure to keep an eye out for the 'summer triangle' of stars! The summer triangle consists of the stars Vega, Altair, and Deneb. They're super bright and can be seen directly overhead in the months of July/August in the UK.

The summer triangle serves as a stellar calendar. When the stars of the summer triangle light up the eastern twilight dusk in middle to late June, it’s a sign of spring giving way to summer. On the other hand, when the summer triangle is seen high in the south to overhead at dusk and early evening, it indicates that summer is transitioning into autumn.

published: 07/08/23 by kaan evcimen