The Twin Jet Nebula

The Twin Jet NebulaThis cosmic butterfly is called the Twin Jet Nebula. It’s a planetary nebula but not just any planetary nebula—it’s a bipolar nebula.

An ordinary planetary nebulae have one star at its center. A bipolar nebulae has a binary star system. The wings of the Twin Jet Nebula are thought to be caused by the motion of its two central stars around each other. As the dying main star and its white dwarf companion orbit around their common center of mass, the ejected gas from the dying star is pulled into the two lobes. The two stars at the heart of the nebula circle one another about every 100 years. This rotation not only forms the wings of the butterfly and the two jets, it also allows the white dwarf to strip gas from its larger companion which then forms a large disc of material around the stars extending out for billions of kilometers, up to 15 times the orbit of Pluto. Even though that disk is of huuge, it is still too small to be seen on the image taken by Hubble.

Image Credit: ESA / NASA

A Star and a Nebula

A cosmic coupleThat’s the star Hen 2-427 (aka WR 124) at the center of this picture. It’s surrounded by the nebula M1-67. They’re found in the constellation of Sagittarius about 15,000 light-years away. The star shines brightly at the very center of these hot clumps of surrounding gas that it’s ejecting into space at over 150,000 km per hour.

Hen 2-427 is a Wolf–Rayet star. Named after the astronomers Charles Wolf and Georges Rayet, Wolf–Rayet stars are super-hot and characterized by a fierce ejection of mass. In this case, that results in the nebula M1-67 which is estimated to be less than 10,000 years old, a newbie in astronomical terms,

Image Credit: ESA

A Colorful Bubble

Little gemThis is NGC 6818. It’s a planetary nebula also known as the Little Gem Nebula. It about 6,000 light-years away in the constellation Sagittarius. The cloud is a bit more than half a light-year across, huge compared to its central star  but still a little gem as nebulas go.

When stars like the Sun are read to “retire,” they shed their outer layers into space which creates glowing clouds of gas called planetary nebulae. The ejection of mass is uneven, and planetary nebulae often have very complex shapes. NGC 6818 has a bright and enclosed central bubble surrounded by a larger, more diffuse cloud. It appears that the stellar wind from the central star propels the outflowing material, shaping NGC 6818. As the fast stellar wind smashes through the slower-moving cloud, it creates particularly bright blowouts in the bubble’s outer layers.

Image Credit: NASA

A Starbursting Galaxy

This is the dwarf galaxy known as NGC 1140. It lies 60 million light-years away in the constellation of Eridanus. It has an irregular form, much like the Large Magellanic Cloud, a small galaxy that orbits the Milky Way. This small galaxy is undergoing a starburst. Despite being only about one-tenth the size of the Milky Way, it is creating stars at about the same rate—the equivalent of one star the size of our sun being created per year. The galaxy is full of bright, blue-white, young stars.

Galaxies like NGC 1140 are of particular interest to astronomers because their composition makes them similar to the intensely star-forming galaxies in the early Universe, and those early Universe galaxies were the building blocks of present-day large galaxies like our Milky Way. Because they are so far away, the early Universe galaxies are harder to study, so these closer starbursting galaxies are a good substitute for studyingt galaxy evolution.

Its vigorous star formation eventually will have a very destructive effect on this small dwarf galaxy. When the larger stars in the galaxy die and explode as supernovae, the gas blown into space may escape the gravitational pull of the galaxy. The ejection of gas from the galaxy throws away one of the building blocks for future star formation. Thus, NGC 1140’s starburst cannot last for long.

Image Credit: ESA