What is at the center of our galaxy?

Here’s a very interesting question: What exactly is at the center of our galaxy? Is there a black hole ? How do we go about studying it?

image

A group of researchers from UCLA’s Galactic center group were inspired by the same question and decided to look at a region in the sky where they believed was the center of our milky way galaxy.

And this is what they found of the trajectories of stars surrounding the proposed center of the galaxy:

image

The star in the middle is the proposed center of our galaxy.These images were taken through the years 1996 – 2016 (see top right of gif).

The first thing that you notice about these stars is that they are orbiting a point in space. This is very similar of how planets in our solar system are orbiting the sun.

image

                                                 Source

One of the special stars in that animation is S0-2 which completes its elliptical orbit in only 15 years!

( it takes the sun approximately 225-250 million years to complete one journey around the galaxy’s center )

image

But having this knowledge of how small the orbit is, we can use Kepler’s law to find out the Mass at the center of the galaxy:

image

And we get the mass of the center as a staggering 4 million times the mass of the Sun.

Let’s take a look at the orbits once again:

image

The radius of this object at the center, in order to avoid collision with the rest of the objects has to be about the diameter of Uranus’s orbit.

So, an object that has 4 million times the mass of the Sun. and diameter of Uranus’s orbit .. Hmm.. The only astronomical object that would fit this characteristic is a Super Massive Black Hole (SMBH)

And that’s why we believe that at the center of our galaxy is a SMBH.

image

Hope you guys liked this post. Have a good one!


* This is how the actual data of the stars orbiting this apparent black hole looks like:

image

**(Lecture) Dr. Andrea M. Ghez “The Monster at the Heart of Our Galaxy”

*** (TED Talk) Andrea Ghez: The hunt for a supermassive black hole
 

     
   
 

All images/animations featured in this post were created by Prof. Andrea Ghez and her
research team at UCLA and are from data sets obtained with the W. M.
Keck Telescopes

coolthingoftheday:

Saturn’s hexagon is a hexagonal cloud pattern that has persisted at the North Pole of Saturn since its discovery in 1981. At the time, Cassini was only able to take infrared photographs of the phenomenon until it passed into sunlight in 2009, at which point amateur photographers managed to be able to photograph it from Earth. 

The structure is roughly 20,000 miles (32,000 km) wide, which is larger than Earth; and thermal images show that it reaches roughly 60 miles (100 km) down into Saturn’s interior.

Read an explanation of how Saturn’s hexagon works here: [x]

Saturn’s fascinating geometry

From the images produced from Voyager and Cassini, scientists were able to develop models that commensurated with the data obtained. Here’s what they found :

image
  1. The Hexagon is associated with an eastward zonal jet moving at more than 200 mph.
    The cause of the Hexagon is believed to be a jet stream, similar to the
    ones that we experience on Earth. The path of the jet itself appears to
    follow the hexagon’s outline.
  2. The Hexagon rotates at roughly the same rate as Saturn’s overall rotation.
    While we observe individual storms and cloud patterns moving at
    different speeds within the Hexagon, the vertices of the Hexagon move at
    almost exactly the same rotational speed as that of Saturn itself.

How do we know this ?

We know this because we can experimentally reproduce the Saturn’s hexagon on earth in a laboratory. ( If you are interested in the technical details of the experiment – click here and here)

The setup is simple :

Researchers placed a 30-liter cylinder of water on a slowly spinning table. ( The water representing the Saturn’s atmosphere )

Inside this tank, they placed a small ring that spun more
rapidly than the cylinder. This created a miniature artificial “jet
stream” that the researchers tracked with a green dye.

The results of which follow below

image

                                                    Source

image

                                                    Source

These models however are still unable to dictate the exact phenomenon that is happening on Saturn, but surely they offer insight into the bizarre phenomenon that dwells in the celestial.

Bonus – Color Change

image

These images from the NASA’s Cassini spacecraft show the changing appearance of Saturn’s north polar region between 2012 and 2016.

The change is thought to be an effect of Saturn’s season ( Yes! Saturn has seasons ). Scientists are still probing into the causes for this change.

image

The universe is a beautiful place.

Have a great day!

Celestial Wonders- Binary Stars.

image

The twins of the stellar world are binary star systems.A binary star is a star system consisting of two stars orbiting around their common center of mass.When two stars appear close together in the sky, the situation is known as an “optical double”. This means that although the stars are aligned along the same line of sight, they may be at completely different distances from us. This occurs in constellations; however, two stars in the same constellation can also be part of a binary system.

image

Artist’s impression of the sight from a (hypothetical) moon of planet HD 188753 Ab (upper left), which orbits a triple star system( yes, a Triple Star system!). The brightest companion is just below the horizon.

image

Binary star systems are very important in astrophysics because calculations of their orbits allow the masses of their component stars to be directly determined, which in turn allows other stellar parameters, such as radius and density, to be indirectly estimated. This also determines an empirical mass-luminosity relationship (MLR) from which the masses of single stars can be estimated.

It is estimated that approximately 1/3 of the star systems in the Milky Way are binary or multiple, with the remaining 2/3 consisting of single stars.

The Brightest star in the sky is a binary.

image

This is true. When it was discovered in 1844 by the German astronomer Bessel, the system was classed as an astrometric binary, because the companion star, Sirius B, was too faint to be seen. Bessel, who was also a mathematician, determined by calculations that Sirius B existed after observing that the proper of Sirius A (the main star) followed a wavy path in the sky, rather than a uniform path. Sirius can now be studied as a visual binary because, with improving technology and therefore improved telescopes, Sirius B was able to be seen, although not for 20 years after Bessel had correctly predicted its existence.

Black Holes in a binary System ?

image

The term “binary system” is not used exclusively for star systems, but also for planets, asteroids, and galaxies which rotate around a common center of gravity. However, this is not a trick question; even in star binaries, the companion can be a black hole. An example of this is Cygnus X-1.

The universe is pretty amazing huh?…