Hubble spots a supernova in the constellation Gemini 

Today’s Image of the Day from the European Space Agency features a galaxy that is located about 600 million light-years away in the constellation Gemini. The Hubble Space Telescope observed a supernova in this galaxy – which appears as a bright blue dot in the photograph.

“This picture was taken roughly two months after a supernova named SN 2022aajn was discovered in this galaxy. The supernova is visible as a blue dot at the center of the image, brightening the hazy body of the galaxy,” noted ESA.

What is a supernova?

Supernovae are spectacular explosions marking the violent deaths of stars. These cosmic events are so luminous they can briefly outshine entire galaxies and radiate more energy in a few weeks than our Sun will in its entire lifetime. 

Supernovae explosions release heavy elements like carbon, oxygen, and iron into the interstellar medium. This stellar debris becomes the building blocks for new stars, planets, and even life itself. 

Supernovae also produce neutron stars or black holes, depending on the remaining core’s mass after the explosion.

Types of supernovae 

There are two main types of supernovae, classified based on their causes. Type I supernovae occur when a white dwarf in a binary system accretes material from its companion star, eventually reaching a critical mass and triggering a runaway nuclear reaction. 

Type II supernovae happen when a massive star, at least eight times the mass of the Sun, exhausts its nuclear fuel. Unable to support its own gravity, the core collapses, resulting in a massive explosion that ejects the outer layers into space.

Measuring the distance to faraway galaxies 

According to ESA, SN 2022aajn is a Type Ia supernova. “Supernovae of this type help astronomers measure the distance to faraway galaxies. This is possible because Type Ia supernovae are thought to be of the same intrinsic luminosity – no matter how bright they seem from Earth, they put out the same amount of light as other Type Ia supernovae.”

This means that researchers can calculate the distance to the supernova and its host galaxy by comparing the observed brightness to the expected brightness.

“This seemingly simple measurement method is complicated by cosmic dust. The farther away a supernova is, the fainter and redder it will appear – but intergalactic dust can make a supernova appear fainter and redder as well,” explained ESA.

“To understand this complication, researchers will use Hubble to survey a total of 100 Type Ia supernovae in seven wavelength bands from the ultraviolet to the near-infrared.”

By analyzing the brightness of supernovae across multiple wavelengths, researchers can distinguish between the influences of dust and distance, refining our measurements of galaxies that exist billions of light-years away.

How many galaxies exist?

The number of galaxies in the universe is estimated to be around two trillion, based on observations from Hubble and more recent data from the James Webb Space Telescope. 

This estimate is derived from deep-field surveys that reveal countless galaxies, each containing billions to trillions of stars. 

However, because our observations are limited by current technology and the vastness of the cosmos, the actual number could be even higher. 

Many galaxies remain unseen due to their extreme distances, faintness, or obstruction by cosmic dust.

The constellation Gemini 

Gemini is one of the 12 zodiac constellations and is best known for representing the mythological twins Castor and Pollux. It is located in the northern celestial hemisphere and is most visible during winter in the Northern Hemisphere. 

The constellation is bordered by Taurus to the west, Cancer to the east, and Orion to the south.

The two brightest stars in Gemini – Castor and Pollux – represent the heads of the twins and are easy to spot. Pollux, the brighter of the two, is an orange giant star about 34 light-years from Earth, while Castor is a more complex system made up of six stars. 

The constellation also contains several notable deep-sky objects, including the open cluster Messier 35, which is a beautiful collection of young stars located near Gemini’s western border.

Image Credit: ESA 

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