February 10, 2016

London at Night seen from the International Space Station

London at Night from Space
London at Night

ISS, Orbit of the Earth
30 January, 2016

Image Credit: ESA/NASA

NGC 4639 with Massive Black Hole seen by Hubble Space Telescope

galaxy massive black hole

NGC 4639 is a beautiful example of a type of galaxy known as a barred spiral. It lies over 70 million light-years away in the constellation of Virgo and is one of about 1,500 galaxies that make up the Virgo Cluster.

In this image, taken by the NASA/ESA Hubble Space Telescope, one can clearly see the bar running through the bright, round core of the galaxy. Bars are found in around two-thirds of spiral galaxies, and are thought to be a natural phase in their evolution.

The galaxy’s spiral arms are sprinkled with bright regions of active star formation. Each of these tiny jewels is actually several hundred light-years across and contains hundreds or thousands of newly formed stars. But NGC 4639 also conceals a dark secret in its core — a massive black hole that is consuming the surrounding gas.

This is known as an active galactic nucleus (AGN), and is revealed by characteristic features in the spectrum of light from the galaxy and by X-rays produced close to the black hole as the hot gas plunges towards it.

Most galaxies are thought to contain a black hole at the center. NGC 4639 is in fact a very weak example of an AGN, demonstrating that AGNs exist over a large range of activity, from galaxies like NGC 4639 to distant quasars, where the parent galaxy is almost completely dominated by the emissions from the AGN.

Image Credit: ESA/Hubble & NASA
Explanation from: http://www.nasa.gov/image-feature/goddard/hubble-sees-elegant-spiral-hiding-a-hungry-monster

Largest stars in the Universe: UY Scuti

UY Scuti is one of the biggest known stars, has a radius of approximately 1 708 ± 120 solar radii or a diameter of 2.4 billion km (2 400 000 000 km) and 25 to 40 Solar mass

Distance from the Sun to UY Scuti is approximately 9 500 light-years

Comparison: Earth - Sun - UY Scuti (Radius)

Comparison: Earth - Sun - UY Scuti (Radius)

UY Scuti pictured from the Rutherford Observatory

UY Scuti

UY Scuti compared to the Sun

Largest star in the UniverseUY Scuti compared to the Sun