Astronomers Detect the Faint Glow of Stars in Between Galaxies

Light 'between' the groups of galaxies – the "intra-group light" – however dim, is radiated from stars stripped from their home galaxy. Image Credit: MARTÍNEZ-LOMBILLA ET AL./UNSW SYDNEY

Not all stars are members of galaxies. Some stars exist in the space between galaxies, though they didn’t form there. They’re called intra-group stars, and astronomers study them by observing their light, called intra-group light (IGL.)

They’re challenging to observe because their light is extremely faint and overpowered by the light of nearby galaxies.

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Subaru Telescope can now Analyze 2,400 Galaxies Simultaneously

First light is an exciting time for astronomers and engineers who help bring new telescopes up to speed. One of the most recent and significant first light milestones recently occurred at the Subaru Telescope in Hawai’i. Though it has been in operation since 2005, the National Astronomical Observatory of Japan’s (NAOJ) main telescope recently received an upgrade that will allow it to simultaneously observe 2400 astronomical objects at once over a patch of sky the size of several moons.

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A Planet has Been Found That Shifts In and Out of the Habitable Zone

Schematic diagram of the newly discovered Ross 508 planetary system. The green region represents the habitable zone where liquid water can exist on the planetary surface. The planetary orbit is shown as a blue line. Credit: Astrobiology Center.

A super-Earth planet has been found orbiting a red dwarf star, only 37 light-years from the Earth. Named Ross 508 b, the newly found world has an unusual elliptical orbit that causes it to shift in and out of the habitable zone. Therefore, part of the time conditions would be conducive for liquid water to exist on the planet’s surface, but other times it wouldn’t.

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Hubble Has Been Watching This Planet Form for 13 Years

Researchers were able to directly image newly forming exoplanet AB Aurigae b over a 13-year span using Hubble’s Space Telescope Imaging Spectrograph (STIS) and its Near Infrared Camera and Multi-Object Spectrograph (NICMOS). In the top right, Hubble’s NICMOS image captured in 2007 shows AB Aurigae b in a due south position compared to its host star, which is covered by the instrument’s coronagraph. The image captured in 2021 by STIS shows the protoplanet has moved in a counterclockwise motion over time. Credits: Science: NASA, ESA, Thayne Currie (Subaru Telescope, Eureka Scientific Inc.); Image Processing: Thayne Currie (Subaru Telescope, Eureka Scientific Inc.), Alyssa Pagan (STScI)

Hubble’s most remarkable feature might be its longevity. The Hubble has been operating for almost 32 years and has fed us a consistent diet of science—and eye candy—during that time. For 13 of its 32 years, it’s been checking in on a protoplanet forming in a young solar system about 530 light-years away.

Planet formation is always a messy process. But in this case, the planet’s formation is an “intense and violent process,” according to the authors of a new study.

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Astronomers Look at Super-Earths That had Their Atmospheres Stripped Away by Their Stars

Figure 1: Artist’s conceptual image showing the sizes of the planets observed in this study. The radius of TOI-1634 is 1.5 times larger than Earth’s radius and TOI-1685 is 1.8 times larger. The planets would appear red, due to the light from the red dwarf stars they orbit. (Credit: Astrobiology Center, NINS)

As the planets of our Solar System demonstrate, understanding the solar dynamics of a system is a crucial aspect of determining habitability. Because of its protective magnetic field, Earth has maintained a fluffy atmosphere for billions of years, ensuring a stable climate for life to evolve. In contrast, other rocky planets that orbit our Sun are either airless, have super-dense (Venus), or have very thin atmospheres (Mars) due to their interactions with the Sun.

In recent years, astronomers have been on the lookout for this same process when studying extrasolar planets. For instance, an international team of astronomers led by the National Astronomical Observatory of Japan (NAOJ) recently conducted follow-up observations of two Super-Earths that orbit very closely to their respective stars. These planets, which have no thick primordial atmospheres, represent a chance to investigate the evolution of atmospheres on hot rocky planets.

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Astronomers set a new Record and Find the Farthest Galaxy. Its Light Took 13.4 Billion Years to Reach us

Galaxy GN-z11 superimposed on an image from the GOODS-North survey. Credit: NASA/ESA/P. Oesch (Yale University)/G. Brammer (STScI)/P. van Dokkum (Yale University)/G. Illingworth (University of California, Santa Cruz)

Since time immemorial, philosophers and scholars have contemplated the beginning of time and even tried to determine when all things began. It’s only been in the age of modern astronomy that we’ve come close to answering that question with a fair degree of certainty. According to the most widely-accepted cosmological models, the Universe began with the Bang Bang roughly 13.8 billion years ago.

Even so, astronomers are still uncertain about what the early Universe looked like since this period coincided with the cosmic “Dark Ages.” Therefore, astronomers keep pushing the limits of their instruments to see when the earliest galaxies formed. Thanks to new research by an international team of astronomers, the oldest and most distant galaxy observed in our Universe to date (GN-z11) has been identified!

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Astronomers Capture a Direct Image of a Brown Dwarf

First direct image of a brown dwarf star in a system not unlike our own.

The field of exoplanet photography is just getting underway, with astronomers around the world striving to capture clear images of the more than 4000 exoplanets discovered to date. Some of these exoplanets are more interesting to image and research than others.  That is certainly the case for a type of exoplanet called a brown dwarf.  And now scientists have captured the first ever image of exactly that type of exoplanet.

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Cosmic Void Contains Fewer Galaxies than Expected, which, Ironically, Makes it Harder for Light to get Through

A computer simulation of the distribution of matter in the universe. Orange regions host galaxies; blue structures are gas and dark matter. Credit: TNG Collaboration

According to the Big Bang Theory of cosmology, the Universe began roughly 13.8 billion years ago as all matter in the Universe began to expand from a single point of infinite density. Over the next few billion years, the fundamental forces of the Universe began to separate from each other and subatomic particles and atoms formed. In time, this first stars and galaxies formed, giving rise to the large-scale structure of the Universe.

However, it was only by roughly 1 billion years after the Big Bang that the Universe began to become transparent. By about 12 billion years ago, intergalactic space was filled with gas that was much less transparent than it is now, with variations from place to place. To address why this was, a team of astronomers recently used the world’s largest telescope to search for galaxies of young stars in a huge volume of space.

The study which details their findings recently appeared in The Astrophysical Journal under the title “Evidence for Large-scale Fluctuations in the Metagalactic Ionizing Background Near Redshift Six“. The study was led by George D. Becker, a professor of astrophysics at the University of California Riverside, and included members from the University of California, Los Angeles (UCLA), and the University of California, Santa Barbara (UCSB).

This illustration shows the evolution of the Universe, from the Big Bang on the left, to modern times on the right. Credit: NASA

For the sake of their study, the team used the Subaru Telescope – the world’s largest telescope, located at the Mauna Kea Observatories in Hawaii – to examine a 500 million light-year volume of space as it existed roughly 12 billion years ago. Using this data, the team considered two possible models that could account for the variations in transparency that astronomers have been seeing during this cosmic epoch.

On the one hand, if the region contained a small number of galaxies, the team would conclude that startlight could not penetrate very far through the intergalactic gas. On the other hand, if it contained an unusually large number of galaxies, this would indicate that the region had cooled significantly over the previous several hundred million years. Prior to their observations, Beck and his team were expecting to find that it was the latter.

However, what they found was that the region contained far fewer galaxies than expected – which indicated that the opaqueness of the region was due to a lack of starlight. As Steven Furlanetto, a UCLA professor of astronomy and a co-author of the research, explained in a recent UCLA press release:

“It was a rare case in astronomy where two competing models, both of which were compelling in their own way, offered precisely opposite predictions, and we were lucky that those predictions were testable… It is not that the opacity is a cause of the lack of galaxies. Instead, it’s the other way around.”

In addition to addressing an enduring mystery in astronomy, this study also has implications for our understanding of how the Universe evolved over time. According to our current cosmological models, the period that took place roughly 380,000 t0 150 million years after the Big Bang is known as the “Dark Ages”. Most of the photons in the Universe were interacting with electrons and protons at this time, which means radiation from this period is undetectable by our current instruments.

However, by about 1 billion years after the Big Bang, the first stars and galaxies had formed. It is further believed that ultraviolet light from these first galaxies filled the Universe and is what allowed for the gas in deep space to become transparent. This would have occurred earlier in regions with more galaxies, the astronomers concluded, hence why there are variations in transparency.

In short, if more ultraviolet radiation from galaxies would lead to greater transparency in the early Universe, then the existence of fewer nearby galaxies would cause certain regions to be murkier. In the future, Becker and his team hope to further study this region of space and others like it in the hope that it will reveal clues about how the first galaxies illuminated the Universe during that early period, which remains a subject of inquiry at this point.

This research is also expected to shed more light on how the early Universe evolved, gradually giving rise to the one that are familiar with today. And as next-generation instruments are able to probe deeper into space (and hence, further back in time), we just may come to understand how existence as we know it all unfolded.

Further Reading: UCLA, The Astrophysical Journal

Galaxies Swell due to Explosive Action of New Stars

Artist’s impression of a disk galaxy transforming in to an elliptical galaxy. Stars are actively formed in the massive reservoir of dust and gas at the center of the galaxy. Credit: NAOJ

In 1926, famed astronomer Edwin Hubble developed his morphological classification scheme for galaxies. This method divided galaxies into three basic groups – Elliptical, Spiral and Lenticular – based on their shapes. Since then, astronomers have devoted considerable time and effort in an attempt to determine how galaxies have evolved over the course of billions of years to become these shapes.

One of th most widely-accepted theories is that galaxies changed by merging, where smaller clouds of stars – bound by mutual gravity – came together, altering the size and shape of a galaxy over time. However, a new study by an international team of researchers has revealed that galaxies could actually assumed their modern shapes through the formation of new stars within their centers.

The study, titled “Rotating Starburst Cores in Massive Galaxies at z = 2.5“, was recently published in the Astrophysical Journal Letters. Led by Ken-ichi Tadaki – a postdoctoral researcher with the Max Planck Institute for Extraterrestrial Physics and the National Astronomical Observatory of Japan (NAOJ) – the team conducted observations of distant galaxies in order to get a better understanding of galactic metamorphosis.

Evolution diagram of a galaxy. First the galaxy is dominated by the disk component (left) but active star formation occurs in the huge dust and gas cloud at the center of the galaxy (center). Then the galaxy is dominated by the stellar bulge and becomes an elliptical (or lenticular) galaxy. Credit: NAOJ

This involved using ground-based telescopes to study 25 galaxies that were at a distance of about 11 billion light-years from Earth. At this distance, the team was seeing what these galaxies looked like 11 billion years ago, or roughly 3 billion years after the Big Bang. This early epoch coincides with a period of peak galaxy formation in the Universe, when the foundations of most galaxies were being formed. As Dr. Tadaki indicated in a NAOJ press release:

“Massive elliptical galaxies are believed to be formed from collisions of disk galaxies. But, it is uncertain whether all the elliptical galaxies have experienced galaxy collision. There may be an alternative path.”

Capturing the faint light of these distant galaxies was no easy task and the team needed three ground-based telescopes to resolve them properly. They began by using the NAOJ’s 8.2-m Subaru Telescope in Hawaii to pick out the 25 galaxies in this epoch. Then they targeted them for observations with the NASA/ESA Hubble Space Telescope (HST) and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.

Whereas the HST captured light from stars to discern the shape of the galaxies (as they existed 11 billion years ago), the ALMA array observed submillimeter waves  emitted by the cold clouds of dust and gas – where new stars are being formed. By combining the two, they were able to complete a detailed picture of how these galaxies looked 11 billion years ago when their shapes were still evolving.

Observation images of a galaxy 11 billion light-years away. Credit: ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, Tadaki et al.

What they found was rather telling. The HST images indicated that early galaxies were dominated by a disk component, as opposed to the central bulge feature we’ve come to associate with spiral and lenticular galaxies. Meanwhile, the ALMA images showed that there were massive reservoirs of gas and dust near the centers of these galaxies, which coincided with a very high rate of star formation.

To rule out alternate possibility that this intense star formation was being caused by mergers, the team also used data from the European Southern Observatory’s Very Large Telescope (VLT) – located at the Paranal Observatory in Chile – to confirm that there were no indications of massive galaxy collisions taking place at the time. As Dr. Tadaki explained:

“Here, we obtained firm evidence that dense galactic cores can be formed without galaxy collisions. They can also be formed by intense star formation in the heart of the galaxy.”

These findings could lead astronomers to rethink their current theories about galactic evolution and howthey came to adopt features like a central bulge and spiral arms. It could also lead to a rethink of our models regarding cosmic evolution, not to mention the history of own galaxy. Who knows? It might even cause astronomers to rethink what might happen in a few billion years, when the Milky Way is set to collide with the Andromeda Galaxy.

As always, the further we probe into the Universe, the more it reveals. With every revelation that does not fit our expectations, our hypotheses are forced to undergo revision.

Further Reading: ALMAAstrophysical Journal Letters