Geminids meteor shower

Mid-December saw the peak of the Geminids meteor shower, one of the best meteor showers of the year! There were up to 120 meteors per hour in the darkest of skies. As the name suggests, the shooting stars were visible in the constellation Gemini, meaning that the prettiest sights were seen in the northern hemisphere.

Tellurium formation in kilonova

This paper details how Levan et al. used the James Webb Space Telescope (JWST) to study the remnant of one of the brightest gamma ray bursts (GRB) ever and found evidence that an element known as tellurium was made in that burst.

A gamma ray burst is a huge intense release of energy we observe in the form of gamma rays (very short wavelengths of electromagnetic radiation). Gamma ray bursts release more energy in a few seconds than our Sun will in its entire lifetime! There's still some debate behind what causes these incredible events, but the leading theory is that it's down to a combination of a supernova of some sorts and a merger of neutron stars.

The JWST image in the paper (fig 2 on page 11) points out the detection of the afterglow of the GRB. They managed to get the spectrum of the afterglow itself and found that it's very similar in shape to the spectrum of GRB AT2017gfo, which we know was produced by a kilonova (when 2 neutron stars merge together). We know this as the gravitational waves produced by such an event was detected by the LIGO (Laser Interferometer Gravitational-Wave Observatory) detector. It's therefore likely that this new GRB also came from a kilonova.

The spectrum also reveals a 'bump' at 2.1 microns, which Levan et al. interpret as evidence for tellurium emission. For centuries now astronomers have been trying to work out where all of the elements on the periodic table actually came from. We know that after stars leave the main sequence, they survive by fusing heavier and heavier elements up to iron. After iron, there is a net loss in energy produced from fusion, so it's still a mystery as to how elements heavier than iron came to be.

Pebble drift in protoplanetary discs

Banzatti et al. used JWST to observe 4 different protoplanetary discs (PPD), the discs where planets form shortly after a star's birth. Using these detections, they wanted to test a hypothesis of planetary formation known as pebble drift.

The outer regions of the PPD are very cold as this is the point furthest away from the central star, so we can expect ice formation in these regions. The particles within the PPD interact with one another on long timescales and exchange energy on occasion through collisions. In such an interaction, the heavier particles lose the most energy while the lighter particles gain energy and zip off. As these heavier particles lose energy, they drift inwards due to the star's gravity and that's what can deliver heavier elements and water to the inner regions of the PPD. If these interactions continue, the temperature of these initially heavy particles will increase and they will cross what's known as the "snow line" – this is basically just the point at which the ice melts into water vapour. So if these bodies can make it in that far, we expect there to be a relatively large concentration of water vapour at this snow line.

From analysing the water spectra from these 4 PPDs, they found that the data supports this pebble drift hypothesis. As JWST observes more PPDs, we'll be able to further understand the mechanisms behind this hypothesis.

First extragalactic protoplanetary disc spotted

Continuing the PPD theme: for the first time in a star outside of our own Milky Way Galaxy, a PPD has been spotted – in the Large Magellanic Cloud, a dwarf galaxy orbiting our own galaxy.

McLeod et al. used the Atacama Large Millimeter Array to observe a massive young star in the Large Magellanic Cloud and found direct evidence for the existence of a PPD around it.

Winter solstice

The 22nd of December was the shortest day of this year, with the winter solstice occurring at 3:27am! From now till the summer solstice (which'll take place on the 20th of June 2024), the days will get longer each day. I think it's so sad when the days are really short – I'm so excited for the summer! ☺️

Quadrantids meteor shower

Heading into the new year, those of us in the northern hemisphere have another meteor shower to look forward to. The Quadrantids meteor shower will peak next year on the 4th of January with an estimated 100 meteors per hour on a clear night.

Supernova Cassiopeia A imaged by JWST

NASA have released an incredible image of supernova remnant Cassiopeia A.

The most visible colours in the NIRCam image are bright orange and light pink, with these representing the inner shell of Cassiopeia A. Within this region are small knots of sulfur, oxygen, argon, and neon gas which came from the star that exploded over 10,300 years ago. Because we see this wreckage as it was so long ago in the past, a portion of the gas and dust within will have already started to move away to form interstellar dust clouds that'll eventually collapse to birth new stars.

Herbig Haro 797

The image below shows a new JWST image of the Harbig Haro object 797 (HH 797). Herbig-Haro objects are luminous regions surrounding newborn stars (known as protostars) and are formed when stellar winds or jets of gas spewing from these newborn stars form shockwaves as they collide with nearby gas and dust at high speeds. HH 797, which dominates the lower half of the image, is located close to the young open star cluster IC 348.

Galactic gathering

The vast galaxy cluster SDSS J1226+2152 in the constellation Coma Berenices can be seen distorting the images of distant background galaxies into streaks and smears of light in this new JWST image. This is a spectacular example of gravitational lensing, a phenomenon which occurs when a massive celestial object such as a galaxy cluster deforms spacetime and causes the path of light from distant objects to be bent as if God himself was manipulating these beams of light.

Just like their optical namesakes, gravitational lenses can magnify as well as distort distant galaxies. This allows astrophysicists to observe the finer details of galaxies that would usually be too distant to clearly resolve. In the case of one of the objects in the image, SGAS J122651.3+215220, the combination of gravitational lensing and Webb’s observational capabilities will allow astronomers to measure where, and how fast, stars are forming and also gain insight into the environments which support star formation in these lensed galaxies.

To the few of you still reading, happy new year!!

I hope 2024 brings you all the happiness in the universe 🪐🌌🥰

published: 25/12/23 by kaan evcimen