Hubble points to our Milky Way's ancient past

We've known for some time that the Milky Way is the result of a number of mergers and collisions with smaller galaxies stretching back billions of years. Some of these collisions such as the one with the Sagittarius Dwarf that started about 6 billion years are actually still underway! Before that, the Milky Way consumed a galaxy referred to as the Gaia-Sausage-Enceladus around10 billion years ago. In the distant future, the Milky Way will merge with the Andromeda galaxy, most likely on a Tuesday afternoon, although some astronomers are not certain of this happening. 

Many of the larger galaxies we observe are the results of these types of mergers and we have a ring-side seat to see these. Being embedded into one of the arms of the Milky Way it's been harder to establish the history of own galaxy. 

“Our home is the Milky Way galaxy, but we do not know how our house was built,” said Davide Massari, lead author, Astrophysics and Space Science Observatory of Bologna in Italy. “In this paper we discover where the first significant batch of bricks came from: a dwarf galaxy that we call LKH.”

An illustration of the early collision of galaxies in the Milky Way's history. Image via NASA, ESA, Joseph Olmsted (STScI)

The used the Hubble Space Telescope to examine globular clusters, large groups of stars that are so tightly bound together by gravity and their stars tall formed at the same time and evolve together. They're also some of the most spectacular objects to view through a telescope and we've covered them in more detail in a blog post here.

Stars in some of these globular clusters were found to have formed outside the Milky Way and are remnants of the earlier LKH galaxy. 

This discovery points to have merger occurring 11.8 billion years ago, extending the known merger timeline 1.8 billion back in into the past. The LKH dwarf galaxy is estimated to have contained around 500 million solar masses in stars which was a significant percentage of the mass of the Milky Way at the time. 

“Some past studies have argued that the earliest phases of our galaxy’s evolution were defined by stars born only in our galaxy,” says Massari. “Here, we have shown that stars born in external galaxies also need to be considered.”

More studies of these globular clusters are planned to continue digging into the Milky Way's past.  One thing to note about galaxy mergers is that while billions of stars, planets, vast interstellar gas clouds and dark matter "whack" into each other, due to the enormous distance between these objects, physical collisions between stars don't occur. Think of it more as thin clouds of smoke blowing into each other,  

Read more here

Nancy Grace Roman Space Telescope is about to launch

An exciting time for astronomers as the latest space telescope is heading to space ahead of time and under budget! It's due to head into space aboard a SpaceX Falcon Heavy rocket next Sunday our time from the Launch Complex 39A at NASA’s Kennedy Space Center in Florida.

Named after NASA's Dr. Nancy Grace Roman who was the space agency's first chief astronomer and often called the "mother of Hubble".

A NASA illustration of the Roman Space Telescope

Roman's main 2.4 metre diameter mirror is the same size as Hubble, but only a quarter the weight due to advances in material technologies in the decades since.

Camera

This wide-field space telescope carries The Wide Field Instrument, or WFI. 

This is a 300-megapixel infrared camera that will give Roman the same
angular resolution as Hubble, however it will capture around 100 times the field of view of Hubble and larger than a full Moon. 

It will also carry a Coronagraph, which will cover the bright disk of stars in the hope of revealing faint details of their exoplanets. 

Science

We'll cover what Roman hopes to achieve in coming articles, but some of its main objects include study dark matter and energy, explore exoplanets and the structure of the Universe.

Where is it being sent to?

Roman is headed to the second Sun-Earth Lagrange point, about 1.6 million km away, where its stable orbit will be balanced between the Sun and the Earth. The Earth won't block much the view, and the space telescope will be less impacted by heat. This is also the same orbit where the James Webb Space Telescope is located. Very chance of them colliding however as they'll be in orbits millions of kms apart...

Catch the best globular cluster tonight 

Speaking of globular clusters, you can easily spot tonight the brightest of them and the largest one in the Milky Way galaxy, Omega Centauri.

The view from Sydney towards the southwest tonight, 22nd Aug, at about 6.30pm

You will see the Southern Cross on its "side" and Omega Centauri sits in the rich star clouds that in that part of the sky. It's just on the edge of visibility with your eyes, a small fuzzy ball in binoculars and a simply amazing sight in a telescope of any size. 

How good is the view? Many of our customers just starting out on their astronomy journey pop in to see me at BINTEL and ask whether they'll be able to see rings of Saturn or the bands and moons of Jupiter. I tell them, "Yes, but just wait until you see Omega Centauri!"

Plus, Omega Centauri mightn't be from the Milky Way.  Astronomers consider it a left over core of a dwarf galaxy the Milky Way ate billions of years ago.  When you peer up at it tonight, you're looking at the same kind of galaxy leftover the Hubble team has been checking out.

Cheers,

Earl White

BINTEL

22nd August 2026