Astronomy Object of the Week - No.5

It's been a while since the last Astro Object of the Week, but here it is! This'll be a little introduction to the variable star SS Cygni, located in the constellation Cygnus, the Swan.

First things first: SS Cygni is categorized as a lot of different things, including a cataclysmic variable star, U Geminorum type dwarf star, and dwarf nova. As a cataclysmic variable star, it will eventually trigger a Type Ia supernova. SS Cygni is a binary system consisting of a white dwarf and a red dwarf that are so close together that one revolutionary period is only a little over six and a half hours long.

Throughout its rotations, the white dwarf will accrete matter from its companion, a common characteristic of dwarf novas. These white dwarfs are also involved in periodic outbursts in which the luminosity will increases due to instability in the accretion disk, every seven to eight weeks in this case.

When the mass of the white dwarf is close enough to or over the Chandrasekhar limit (1.4 solar masses), runaway carbon fusion will occur and lead to a spectacular (yet morbid) display of colors.

The Marsupials of Australia

Good day, mates! It's been a week since I got back from my trip Down Under and visited the Australian cities of Sydney, Melbourne, and Gold Coast and the New Zealand cities of Queenstown (South Island) and Auckland (North Island).

It was a wonderful trip in general, but one of my favourite places on my journey was probably the Gold Coast. Here, I got to visit the Currumbin Wildlife Sanctuary, where I met some of the cutest and most amazing animals in the world, including koalas and kangaroos. The collection of species at the sanctuary reflected the fauna of Australia as a whole and therefore a large number of marsupial mammals, which I'll be talking about today.

Marsupials are interesting as mammals since they only occur in the Americas and Australasia (Australia, New Zealand, New Guinea), and 70% of those 334 extant species are endemic to Australia. Some of the most widely known Australian marsupials are koalas, kangaroos, wallabies, wombats, possums, and Tasmanian devils. Placental mammals are very rare in Australia, and the dingo, another famous Australian animal, is not actually a native species.

 

The most iconic characteristic of marsupial species is that the young are carried in a pouch after birth. There are also differences in other anatomical structures, including the brain; the marsupial brain does not have a corpus callosum that connects the brain hemispheres as Eutherians do. The skull and skeleton are also different.

However, perhaps the most marked difference is definitely in the reproductive system, in both structure and gestation process. Pregnancy is very short, and the embryo is born in an early stage of reproduction, reducing the risks of long-term pregnancies. This newborn joey finds its way to its mother's pouch and latches onto one of the many nipples there, from which it will receive food and develop more fully to one day be able to live out of the pouch.

Now here are some cute marsupials for your viewing enjoyment!