A Dwarf Galaxy


A messy star factoryThis is the blue compact dwarf galaxy known as Markarian 209. Because galaxies of this type are rich in gas and poor in heavy elements, astronomers use them to study star formation. Such conditions are believed to be similar to those existing in the early Universe. Markarian 209 has been studied extensively. It is filled with diffuse gas and peppered with star-forming regions towards its core. The lighter blue cloudy region towards the top right of the galaxy is filled with very young and hot newborn stars.

It was initially thought to be a young galaxy undergoing its initial period of star formation. However, research showed that Markarian 209 is actually very old. It is thought to have never had a dormant period with no stars forming that lasted for longer than 100 million years. Most of stars in Markarian 209 are quite young, under 3 million years old. Our Sun is around 4.6 billion years old.

A scattering of other bright galaxies can be seen across the frame of this Hubble image, including the bright golden oval that could be mistaken as part of Markarian 209 but is in fact a background galaxy.

Image Credit: ESA / NASA
Acknowledgement: Nick Rose

NGC 4102


This is no supermodel spiralNGC 4102 lies in the northern constellation of Ursa Major (The Great Bear). It contains what is known as a LINER, or low-ionization nuclear emission-line region. That means its nucleus emits particular types of radiation, emission from weakly-ionised or neutral atoms of certain elements. That’s not very unusual. About one third of all nearby galaxies are thought to be LINER galaxies.

Many LINER galaxies also contain intense regions of star formation. This is thought to be intrinsically linked to their galactic centers, but the reason why is still a mystery. It may be that the starbursts pour fuel inwards to fuel the LINERs, or this active central region might trigger the starbursts. NGC 4102 does indeed contain a starburst region near its center where stars are being created at a more rapid rate than in a normal galaxy.

Image Credit: NASA / ESA

An X-Ray View (And Infrared Too)


ngc2207_chandraA few weeks ago, I posted a Hubble image of two merging galaxies, NGC 2207 and IC 2163. This composite image of those galaxies contains Chandra x-ray data in pink, optical light data from the Hubble in red, green, and blue (appearing as blue, white, orange, and brown), and infrared data from the Spitzer Space Telescope in red.

Image Credit: NASA