Atoms or their constituents account for a mere 4.9 percent of the universe. The rest is dark matter, so understanding this ubiquitous yet mysterious substance is a prime goal of modern astrophysics. By studying the spatial distribution of gamma-ray emission in the Milky Way, astronomers believe they have now identified a signature of dark matter annihilation.
In this Hubble Space Telescope image we see an irregular dwarf galaxy known as UGC 4459, located in the constellation of Ursa Major (The Great Bear). While UGC 4459’s diffused and disorganised stellar population of several billion sounds impressive, this is small when compared to the 200 to 300 billion stars in the Milky Way.
This image shows a lonely galaxy known as Wolf-Lundmark-Melotte, or WLM for short. Although considered part of our Local Group of dozens of galaxies, WLM stands alone at the group’s outer edges as one of its most remote members. In fact, WLM is so small and secluded that it may never have interacted with any other galaxy in the history of the universe.
The lightest few chemical elements formed minutes after the Big Bang. Most heavier elements in the periodic table are created by stars, either from internal nuclear fusion or in catastrophic explosions. New observations of a dwarf galaxy discovered last year show that the heaviest elements, such as gold and lead, are likely left over from rare collisions between two neutron stars.
A strange new kind of galactic beast has been spotted in the cosmic wilderness. Dubbed “super spirals,” these unprecedented galaxies dwarf our own spiral galaxy, the Milky Way, and compete in size and brightness with the largest galaxies in the universe. The galaxies have long hidden in plain sight by mimicking the appearance of typical spirals.
Two astronomy students from Leiden University have mapped the entire Milky Way Galaxy in dwarf stars for the first time. They show that there are a total of 58 billion dwarf stars, of which seven percent reside in the outer regions of our galaxy. This result is the most comprehensive model ever for the distribution of these stars.
Astronomers have used computer simulations based on theoretical models to explain massive star formation observed in dwarf galaxies. Researchers in the US and the Netherlands found that during a dark matter satellite’s closest approach to a dwarf galaxy, through gravity it compresses the gas in the dwarf, triggering significant episodes of starbursts.
Peering deep into the early universe, this picturesque parallel field observation from the NASA/ESA Hubble Space Telescope reveals thousands of colourful galaxies swimming in the inky blackness of space in the constellation Sculptor. This spectacular skyscape was captured during the study of the giant galaxy cluster Abell 2744, otherwise known as Pandora’s Box.
Astronomers for the first time have detected repeating short bursts of radio waves from an enigmatic source that is likely located well beyond the edge of our Milky Way galaxy. The findings indicate that these “fast radio bursts” come from an extremely powerful object which occasionally produces multiple bursts in under a minute.
Surrounding the black hole at the centre of our Milky Way galaxy and stretching out to about 700 light-years, is a dense zone of activity called the Central Molecular Zone (CMZ). It contains many dense molecular clouds that would normally be expected to produce new stars, but which are instead eerily desolate. Where did the CMZ come from? No place else in the Milky Way is remotely like it.
© 2019 Pole Star Publications Limited