Today’s Image of the Day from the European Space Agency features UGC 5460, a spiral galaxy that is located about 60 million light-years away in the constellation Ursa Major. 

“This image combines four different wavelengths of light to reveal UGC 5460’s central bar of stars, winding spiral arms and bright blue star clusters. Also captured in the upper left-hand corner of this image is a far closer object: a star just 577 light-years away in our own galaxy,” said ESA.

“UGC 5460 has hosted two recent supernovae named SN 2011ht and SN 2015as. It’s because of these two stellar explosions that Hubble targeted this galaxy, collecting data for three observing programmes that aim to study various kinds of supernovae.” 

A core-collapse supernova 

SN 2015as is an example of a core-collapse supernova. This type of supernova occurs when the core of a massive star – typically with more than 8 times the mass of the sun – can no longer support its own gravity after exhausting its nuclear fuel. 

This causes the core to collapse under its own weight, leading to an extremely violent explosion. The collapse triggers the release of an enormous amount of energy, expelling the outer layers of the star into space.

In the aftermath of the explosion, a dense remnant is created. This is often a neutron star or black hole, depending on the mass of the original star. Core-collapse supernovae are some of the most powerful events in the universe.

According to ESA, Hubble observations of SN 2015as will help researchers understand what happens when the expanding shockwave of a supernova collides with the gas that surrounds the exploded star.

Rare stars with large eruptions 

“SN 2011ht might have been a core-collapse supernova as well, but it could also be an impostor called a luminous blue variable. Luminous blue variables are rare stars that experience eruptions so large that they can mimic supernovae,” noted ESA.

“Crucially, luminous blue variables emerge from these eruptions unscathed, while stars that go supernova do not. Hubble will search for a stellar survivor at SN 2011ht’s location, and the explosion’s identity may be revealed at last.”

What is a spiral galaxy?

Spiral galaxies are some of the most recognizable and beautiful structures in the universe. They are known for their distinctive arms that spiral outward from a central bulge. 

These galaxies are typically composed of stars, gas, dust, and dark matter. The arms are often sites of intense star formation, where clouds of gas collapse to form new stars. 

In the center of a spiral galaxy lies a dense concentration of older stars and, often, a supermassive black hole.

Structure of a spiral galaxy 

The structure of a spiral galaxy is generally divided into three main components: the disk, the bulge, and the halo. 

The disk is where the spiral arms are located and contains most of the galaxy’s visible stars and interstellar medium. 

The bulge is a tightly packed region of older stars at the core, and the halo consists of a sparse collection of stars and globular clusters that surround the galaxy. 

Spiral galaxies can be classified into different types based on the tightness and number of their spiral arms, as well as the size of their central bulge.

The Milky Way galaxy

Our solar system is located within a large spiral galaxy known as the Milky Way. The name refers to its appearance as a dim, milky band of light stretching across the night sky. 

The term “Milky Way” comes from ancient Greek mythology, where it was associated the goddess Hera’s milk spilling into the sky. In Greek, it was called “Galaxias Kyklos,” meaning “milky circle.” 

Spanning about 100,000 light-years in diameter, the Milky Way is composed of stars, gas, dust, and dark matter. The galaxy has a distinct disk shape with spiral arms that wind outward from a central bulge, which houses a supermassive black hole. 

Our sun is located in one of the spiral arms – known as the Orion Arm – positioned roughly halfway from the center to the outer edge. 

The Milky Way is part of a small group of galaxies called the Local Group, which includes the Andromeda Galaxy and several smaller galaxies.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–