The Milky Way’s Last Merger Event Was More Recent Than Thought

Our home galaxy as seen by the European Space Agency’s Gaia satellite. Image Credit: ESA/Gaia/DPAC

The Milky Way is only as massive as it is because of collisions and mergers with other galaxies. This is a messy process, and we see the same thing happening with other galaxies throughout the Universe. Currently, we see the Milky Way nibbling at its two satellite galaxies, the Large and Small Magellanic Clouds. Their fate is likely sealed, and they’ll be absorbed into our galaxy.

Researchers thought the last major merger occurred in the Milky Way’s distant past, between 8 and 11 billion years ago. But new research amplifies the idea that it was much more recent: less than 3 billion years ago.

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The Milky Way’s Most Massive Stellar Black Hole is Only 2,000 Light Years Away

This image shows the locations of the first three black holes discovered by ESA's Gaia mission in the Milky Way. Gaia Black Hole 1 (BH1) is located just 1560 light-years away from us in the direction of the constellation Ophiuchus; Gaia BH2 is 3800 light-years away in the constellation Centaurus; Gaia BH3 is in the constellation Aquila, at a distance of 1926 light-years from Earth. In galactic terms, these black holes reside in our cosmic backyard. Image Credit: ESA/Gaia/DPAC. Licence CC BY-SA 3.0 IGO

Astronomers have found the largest stellar mass black hole in the Milky Way so far. At 33 solar masses, it dwarfs the previous record-holder, Cygnus X-1, which has only 21 solar masses. Most stellar mass black holes have about 10 solar masses, making the new one—Gaia BH3—a true giant.

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For its Next Trick, Gaia Could Help Detect Background Gravitational Waves in the Universe

Artist impression of ESA's Gaia satellite observing the Milky Way. The background image of the sky is compiled from data from more than 1.8 billion stars. It shows the total brightness and colour of stars observed by Gaia
Artist impression of ESA's Gaia satellite observing the Milky Way (Credit : ESA/ATG medialab; Milky Way: ESA/Gaia/DPAC)

Ripples in a pond can be captivating on a nice sunny day as can ripples in the very fabric of space, although the latter are a little harder to observe.  Using the highly tuned Gaia probe, a team of astronomers propose that it might just be possible to detect gravitational waves through the disturbance they impart on the movement of asteroids in our Solar System!

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Gaia is so Accurate it Can Predict Microlensing Events

ESA/Gaia/DPAC; CC BY-SA 3.0 IGO. Acknowledgement: A. Moitinho.

The ESA’s Gaia Observatory continues its astrometry mission, which consists of measuring the positions, distances, and motions of stars (and the positions of orbiting exoplanets) with unprecedented precision. Launched in 2013 and with a five-year nominal mission (2014-2019), the mission is expected to remain in operation until 2025. Once complete, the mission data will be used to create the most detailed 3D space catalog ever, totaling more than 1 billion astronomical objects – including stars, planets, comets, asteroids, and quasars.

Another benefit of this data, according to a team of researchers led by the Chinese Academy of Sciences (CAS), is the ability to predict future microlensing events. Similar to gravitational lensing, this phenomenon occurs when light from background sources is deflected and amplified by foreground objects. Using information from Gaia‘s third data release (DR3), the team predicted 4500 microlensing events, 1664 of which are unlike any we have seen. These events will allow astronomers to conduct lucrative research into distant star systems, exoplanets, and other celestial objects.

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A Huge New Gaia Data Release: More Stars, Gravitational Lenses and Asteroids

The ESA's Gaia observatory expanded its targets to include the tightly-packed center of Omega Centauri, an ancient globular cluster. Image Credit: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO. Acknowedgements: Michele Trabucchi, Nami Mowlavi and Thomas Lebzelter

The ESA’s Gaia mission is releasing a new tranche of astronomical data. The mission has released three regular, massive hauls of data since it launched in 2013, named Gaia DR1, DR2, and DR3. The ESA is calling this one a ‘focused product release,’ and while it’s smaller than the previous three releases, it’s still impactful.

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Gaia is Now Finding Planets. Could it Find Another Earth?

Artist's impression of the ESA's Gaia Observatory. Credit: ESA

The ESA launched Gaia in 2013 with one overarching goal: to map more than one billion stars in the Milky Way. Its vast collection of data is frequently used in published research. Gaia is an ambitious mission, though it seldom makes headlines on its own.

But that could change.

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Astronomers Find a Planet Using Gaia Data

Artist view of a Jupiter-like exoplanet. Credit: NASA/Goddard Space Flight Center/S. Wiessinger

The ESA’s Gaia mission is our most accurate star-measuring spacecraft. It’s busy mapping the positions and radial velocities of one billion stars in the Milky Way. The mission’s goal is to create a representative map of the galaxy’s stellar population with unprecedented accuracy. The mission has released 3 sets of data since its inception, leading to many discoveries.

Now a team of astronomers has found an exoplanet with help from Gaia, an unintended result of the ambitious mission.

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Not Just Stars. Gaia Mapped a Diverse and Shifting Universe of Variable Objects

We’ve reported on Gaia’s incredible data-collection abilities in the past. Recently, it released DR3, its latest data set, with over 1.8 billion objects in it. That’s a lot of data to sift through, and one of the most effective ways to do so is through machine learning. A group of researchers did just that by using a supervised learning algorithm to classify a particular type of object found in the data set. The result is one of the world’s most comprehensive catalogs of the type of astronomical object known as variables.

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How Do Stars Get Kicked Out of Globular Clusters?

Hubble image of Messier 54, a globular cluster located in the Sagittarius Dwarf Galaxy. Credit: ESA/Hubble & NASA

Globular clusters are densely-packed collections of stars bound together gravitationally in roughly-shaped spheres. They contain hundreds of thousands of stars. Some might contain millions of stars.

Sometimes globular clusters (GCs) kick stars out of their gravitational group. How does that work?

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Astronomers Find a Sun-like Star Orbiting a Nearby Black Hole

Gaia BH1 is a Sun-like star co-orbiting with a black hole estimated at 10 times the Sun's mass. Credit: ESO/L. Calcada

In 1916, Karl Schwarzchild theorized the existence of black holes as a resolution to Einstein’s field equations for his Theory of General Relativity. By the mid-20th century, astronomers began detecting black holes for the first time using indirect methods, which consisted of observing their effects on surrounding objects and space. Since the 1980s, scientists have studied supermassive black holes (SMBHs), which reside at the center of most massive galaxies in the Universe. And by April 2019, the Event Horizon Telescope (EHT) collaboration released the first image ever taken of an SMBH.

These observations are an opportunity to test the laws of physics under the most extreme conditions and offer insights into the forces that shaped the Universe. According to a recent study, an international research team relied on data from the ESA’s Gaia Observatory to observe a Sun-like star with strange orbital characteristics. Due to the nature of its orbit, the team concluded that it must be part of a black hole binary system. This makes it the nearest black hole to our Solar System and implies the existence of a sizable population of dormant black holes in our galaxy.

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