A dazzling collection of galaxies and supernovae imaged by Hubble

This Hubble Space Telescope Image Collection from NASA/ESA, captured between 2003 and 2021, features host galaxies of Cepheid variable stars and type Ia supernovae. These two celestial phenomena are crucial tools used by astronomers to determine astronomical distance and are used to improve the measurement of Hubble constantthe expansion rate of the Universe.

Each of the images in this special collection features a spiral galaxy that hosts both Cepheid variables and a special class of supernovae, two remarkable stellar phenomena that apparently have little in common but are very useful to astronomers.

Like Cepheid variable stars they are pulsating stars that brighten and darken regularly.

Like type Ia supernovae are the catastrophic explosions that mark the death of a hot, dense white dwarf.

From the vast collection of Cepheid and supernova variables in galaxies observed by Hubble, in its three-decade quest to accurately measure the rate of expansion of the Universe, were chosen (top to bottom and left to right) :

NGC 7541, NGC 3021, NGC 5643, NGC 3254, NGC 3147, NGC 105, NGC 2608, NGC 3583, NGC 3147, Mr 1337, NGC 5861, NGC 2525, NGC 1015, CGU 9391, NGC 691, NGC 7678, NGC 2442, NGC 5468, NGC 5917, NGC 4639, NGC 3972, The Antennae Galaxies, NGC 5584, M106, NGC-7250, NGC 3370, NGC 5728, NGC 4424, NGC 1559, NGC 3982, NGC 1448, NGC 4680, M101, NGC 1365, NGC 7329 and NGC 3447.

Measure the distance to a celestial body

Both phenomena can be used by astronomers to measure how far away a celestial body is, which is a huge challenge for astronomers. It can be difficult to distinguish between objects that are dark and relatively close to Earth and those that are bright and distant.

To help overcome this challenge, astronomers have developed something called the Cosmic Distance Scale, a series of methods for determining distances, organized by the relative distances that can be measured.

Two important steps on this scale are Cepheid variables and supernovae: Cepheid variables because the period over which they pulsate can be used to calculate their distance, and supernovae because each explosion of a Type Ia supernova always has the same luminosity, meaning that the glow emanating from and seen from Earth can be used to determine its distance.

All galaxies featured in this collection host Cepheid variable stars and have had at least one Type Ia supernova explosion in the past 40 years. One of the galaxies, NGC 2525, even contained a supernova which was captured in real time.

One of Hubble’s main scientific goals: to measure the expansion rate of the Universe

Even before its launch, one of Hubble’s primary scientific goals was to observe Cepheid variables and supernovae. These observations can help measure the rate of expansion of the Universe, a value astronomers call the Hubble constant. Generations of astronomers have refined this value over nearly 30 years using data from more than 1,000 hours of work from Hubble.

When Hubble was launched in 1990, the rate of expansion of the Universe was so uncertain that its age could be as little as 8 or 20 billion years.

After 30 years of painstaking work using the telescope’s extraordinary observing power, several teams of astronomers have managed to achieve a more accurate rate of just over 1% – a figure that can be used to predict that the Universe will double in size in 10 billion years. .

More recently, a team of astronomers called SH0ES used observations of every supernova seen by Hubble over the past 30 years – including those of the galaxies pictured here – to determine the value of Hubble’s constant at 73.04 ± 1 :04 kms-1 Mpc. -1.

“That’s what the Hubble Space Telescope was built for. We get the standard measurement of the Universe from telescopes,” says Nobel Laureate Adam Riess of Johns Hopkins University, who leads the team. SH0ES “This is Hubble’s masterpiece.”

O article of the Riess team, to be published in the Special Focus edition of The Astrophysical Journalreports how the biggest – and probably the last – update to Hubble’s constant was completed.

From the vast collection of Cepheid and supernova variables in galaxies observed by Hubble, in its three-decade quest to accurately measure the rate of expansion of the Universe, were chosen (top to bottom and left to right) :

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