One Ring to Rule Them All


Zw II 28 is a ring galaxy. Ring galaxies are thought to form when one galaxy passes through the disc of another, larger one. Because galaxies are mostly empty space, such “collisions” are not as destructive as one might suppose. The probability of two stars physically colliding is nearly zero. It’s the gravitational effects of the two galaxies that causes disruption, upsetting the balance both galaxies and causing the pair to redistribute to form a dense central core surrounded by bright stars. In the process, clouds of gas and dust collapse, triggering intense star formation in the outer ring and filling it with hot, young, blue stars.

Zw II 28’s sparkling pink and purple loop is not typical of a ring galaxy. It lacks a visible central companion, but recent observations using Hubble have shown that there may be a possible companion lurking just inside the ring, where the loop seems to double back on itself.

Image Credit: ESA / NASA

HH 901


Herbig Haro 901 is a multiple light-years tall pillar of gas and dust inside the star-forming region know as the Carina Nebula. It contains several massive young stars which emit powerful jets that emerge from the cloud. Some of the jets create bow-shock patterns similar to the bow waves of a ship plowing through the ocean. Very few of these stars can be seen  because the gas and dust block starlight, but in an infrared view, more stars become visible. The visible-light colors result from the glow of different gases: oxygen (blue), hydrogen/nitrogen (green), and sulfur (red). The Carina Nebula is approximately 7,500 light years from Earth.

Video Credit: NASA / ESA / STScI

A Light in a Cloud


RNO91A very young star is being born in the dark cloud LDN 43, a massive aggregation of gas, dust, and ices, a bit more than 500 light-years away in the constellation of Ophiuchus (The Serpent Bearer). Dust and gas float in space, and as gravity pulls the matter together, some clumps grown to form stars

This newborn star is hidden from direct view. We can only see it’s light reflected onto the plumes of the dark cloud. It’s be cataloged as RNO 91. It’s a pre-main sequence star. It has not yet started burning hydrogen in its core, so the energy that causes RNO 91 to shine comes from gravitational contraction. As the star is compressed by its own weight, it will eventually reach a critical mass, its hydrogen will begin to undergo the same fusion process that drives our Sun, and RNO 91 will become an adult star. However, the adolescent star is still bright enough to shine and generate powerful stellar winds, intense X-rays, and radio emission.

RNO 91 is a variable star with about half the mass of the Sun. A dusty, icy disk surrounds it, stretching out to over 1,700 times the distance from Earth to the Sun. It is possible that this disk may host protoplanets and ,ay evolve into a fully-fledged planetary system.

Image Credit: NASA