The Case of the “Missing Exoplanets”

An illustration of the variations among the more than 5,000 known exoplanets discovered since the 1990s. Credit: NASA/JPL-Caltech

Today, the number of confirmed exoplanets stands at 5,197 in 3,888 planetary systems, with another 8,992 candidates awaiting confirmation. The majority have been particularly massive planets, ranging from Jupiter and Neptune-sized gas giants, which have radii about 2.5 times that of Earth. Another statistically significant population has been rocky planets that measure about 1.4 Earth radii (aka. “Super-Earths”). This presents a mystery to astronomers, especially where the exoplanets discovered by the venerable Kepler Space Telescope are concerned.

Of the more than 2,600 planets Kepler discovered, there’s an apparent rarity of exoplanets with a radius of about 1.8 times that of Earth – which they refer to as the “radius valley.” A second mystery, known as “peas in a pod,” refers to neighboring planets of similar size found in hundreds of planetary systems with harmonious orbits. In a study led by the Cycles of Life-Essential Volatile Elements in Rocky Planets (CLEVER) project at Rice University, an international team of astrophysicists provide a new model that accounts for the interplay of forces acting on newborn planets that could explain these two mysteries.

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China Launches Mengtian, the Last Major Module to its Space Station

Artist's rendering of the completed Tiangong space station. Credit: Shujianyang/Wikimedia

On the afternoon of Monday, October 31st, 2022 (Halloween!), China launched the Mengtian laboratory cabin module into space, where it will join the Tiangong modular space station. This module, whose name translates to “Dreaming of the Heavens,” is the second laboratory and final addition to Tiangong (“Palace in the Sky”). This successful launch places China one step closer to completing its first long-term space station, roughly one-fifth the mass of the International Space Station (ISS) and comparable in size to Russia’s decommissioned Mir space station.

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Hubble saw Multiple Light Echoes Reflecting off Rings of Dust From a Supernova Explosion

Artist view of a supernova explosion. Credit: NASA

When stars reach the end of their life cycle, they experience gravitational collapse at their centers and explode in a fiery burst (a supernova). This causes them to shed their outer layers and sends an intense burst of light and high-energy short-wavelength radiation (like X-rays and gamma-rays) out in all directions. This process also creates cosmic rays, which consist of protons and atomic nuclei that are accelerated to close to the speed of light. And on rare occasions, supernovae can also create “light echoes,” rings of light that spread out from the site of the original explosion.

These echoes will appear months to years after the supernova occurs as light from the explosion interacts with the layers of dust in the vicinity. Using the Hubble Space Telescope (HST), an international team of astronomers was able to document the emergence and evolution of multiple light echoes (LEs). The team traced these echoes to a stripped-envelope supernova (SN 2016adj) located in the central dust lane of Centaurus A, a galaxy located 10 to 16 million light-years away in the constellation of Centaurus.

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Mars is Mostly Dead. There's Still Magma Inside, so it's Slightly Alive

Artist's concept of InSight "taking the pulse of Mars". Credit: NASA/JPL-Caltech

Since February 2019, NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander has been making the first-ever measurements of tectonics on another planet. The key to this is InSight’s Seismic Experiment for Interior Structure (SEIS) instrument (developed by seismologists and geophysicists at ETH Zurich), which has been on the surface listening for signs of “marsquakes.” The dataset it has gathered (over 1,300 seismic events) has largely confirmed what planetary scientists have long suspected: that Mars is largely quiet.

However, a research team led by ETH Zurich recently analyzed a cluster of more than 20 recent marsquakes, which revealed something very interesting. Based on the location and spectral character of these events, they determined that most of Mars’ widely distributed surface faults are not seismically active. Nevertheless, most of the 20 seismic events observed originated in the vicinity of Cerberus Fossae, a region consisting of rifts (or graben). These results suggest that geological activity and volcanism still play an active role in shaping the Martian surface.

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What Happens to Hot Jupiters when their Star Becomes a Red Giant?

This artist’s impression shows an ultra-hot exoplanet as it is about to transit in front of its host star. Using the ESPRESSO instrument of ESO’s Very Large Telescope, astronomers have found the heaviest element yet in an exoplanet's atmosphere, barium, in the two ultra-hot Jupiters WASP-76 b and WASP-121 b. Image Credit: ESO

The study of extrasolar planets has led to some astounding discoveries, many of which have defied the expectations of astronomers and challenged our notions about the forms planetary systems can take. For example, the discovery of Jupiter-sized planets that orbit closely to their stars (“Hot Jupiters”) defied what astronomers suspected about gas giants. Previously, the general consensus was that gas giants form beyond the “Frost Line” – the boundary beyond which volatile elements (like water) freeze solid – and remain there for the rest of their lives.

Interestingly, this will happen when our Sun leaves its main sequence phase and enters its Red Giant Branch (RGB) phase. This raises the question of what happens to Hot Jupiters when their parent stars expand to become Red Giants. Using advanced 3D simulations, a team of researchers led by the Compact Object Mergers: Population Astrophysics and Statistics (COMPAS) consortium simulated how red giants will expand to engulf Hot Jupiters. Their findings could answer another mystery confronting astronomers, which is why some binary systems have one rapidly-rotating star with strange chemical compositions.

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The Moon had Volcanoes More Recently Than Previously Believed

New measurements of lunar rocks have demonstrated that the ancient moon generated a dynamo magnetic field in its liquid metallic core (innermost red shell). The results raise the possibility of two different mechanisms — one that may have driven an earlier, much stronger dynamo, and a second that kept the moon’s core simmering at a much slower boil toward the end of its lifetime. Credit: Hernán Cañellas/Benjamin Weiss

Fifty years ago, NASA and the Soviet space program conducted the first sample-return missions from the Moon. This included lunar rocks brought back to Earth by the Apollo astronauts and those obtained by robotic missions that were part of the Soviet Luna Program. The analysis of these rocks revealed a great deal about the Moon’s composition, formation, and geological history. In particular, scientists concluded that the rocks were formed from volcanic eruptions more than three billion years ago.

In recent years, there has been a resurgence in lunar exploration as NASA and other space agencies have sent robotic missions to the Moon (in preparation for crewed missions). For instance, China has sent multiple orbiters, landers, and rovers to the Moon as part of the Chang’e program, including sample-return missions. A new study led by planetary scientists from the Chinese Academy of Sciences (CAS) analyzed samples obtained by the Chang’e-5 rover dated to two billion years ago. Their research could provide valuable insight into how young volcanism shaped the lunar surface.

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When Should Robots Take Risks Exploring Other Worlds?

The path followed by Perseverance in the Jezero Crater since landing in February 2021. Credit: NASA

On May 1st, 2009, after five years on the Martian surface, the Spirit rover got stuck in a patch of soft sand (where it would remain for the rest of its mission). On February 13th, 2019, NASA officials declared that Spirit’s sister – the Opportunity rover – had concluded its mission after a planetary dust storm forced it into hibernation mode about seven months prior. And in March 2017, the Curiosity rover’s wheels showed signs of their first break, thanks to years of traveling over rough terrain. Such are the risks of sending rover missions to other planets in search of discoveries that can lead to scientific breakthroughs.

But what constitutes an acceptable risk for a robotic mission, and when are mission controllers justified in taking them? As it turns out, a pair of researchers from the Robotics Institute‘s School of Computer Science at Carnegie Mellon University (CMU) in Pittsburgh have developed a new approach for weighing the risks against the scientific value of sending planetary rovers into dangerous situations. The researchers are now working with NASA to implement their approach for future robotic missions to the Moon, Mars, and other potentially-hazardous environments in the Solar System.

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Did Supermassive Black Holes Collapse Directly out of Giant Clouds of gas? It Could Depend on Magnetic Fields

This artist’s impression shows a possible seed for the formation of a supermassive black hole. Credit: NASA/CXC/M. Weiss

Roughly half a century ago, astronomers realized that the powerful radio source coming from the center of our galaxy (Sagitarrius A*) was a “monster” black hole. Since then, they have found that supermassive black holes (SMBHs) reside at the center of most massive galaxies. This leads to what is known as Active Galactic Nuclei (AGN) or quasars, where the central region of a galaxy is so energetic that it outshines all of the stars in its galactic disk. In all that time, astronomers have puzzled over how these behemoths (which play a crucial role in galactic evolution) originated.

Astronomers suspect that the seeds that formed SMBHs were created from giant clouds of dust that collapsed without first becoming stars – aka. Direct Collapse Black Holes (DCBHs). However, the role of magnetic fields in the formation of DCBHs has remained unclear since none of the previous studies have been able to simulate the full accretion periods. To investigate this, an international team of astronomers ran a series of 3D cosmological magneto-hydrodynamic (MHD) simulations that accounted for DCBH formation and showed that magnetic fields grow with the accretion disks and stabilize them over time.

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NASA Announces the Team who'll be Studying UFO Data. It's a Pretty Impressive List

UFO encounter video
Cockpit video shows an anomalous aerial encounter in 2015. Credit: U.S Navy Video

In June, NASA announced that it had commissioned an independent study team to investigate unidentified aerial phenomena (UAPs) from a scientific perspective. Last week, NASA announced the members of the independent team that will study observed events in the sky that cannot be identified as aircraft or natural phenomena. These sixteen individuals, a collection of scientists and researchers from premier institutions across the U.S., will analyze all possible data sources that could help NASA and other agencies learn more about this phenomenon.

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Here are Four Ways JWST Could Detect Alien Life

Artist conception of the James Webb Space Telescope. Credit: NASA GSFC/CIL/Adriana Manrique Gutierrez

Less than a year after it went to space, the James Webb Space Telescope (JWST) has already demonstrated its worth many times over. The images it has acquired of distant galaxies, nebulae, exoplanet atmospheres, and deep fields are the most detailed and sensitive ever taken. And yet, one of the most exciting aspects of its mission is just getting started: the search for evidence of life beyond Earth. This will consist of Webb using its powerful infrared instruments to look for chemical signatures associated with life and biological processes (aka. biosignatures).

The chemical signatures vary, each representing a different pathway toward the potential discovery of life. According to The Conversation’s Joanna Barstow, a planetary scientist and an Ernest Rutherford Fellow at The Open University specializing in the study of exoplanet atmospheres, there are four ways that Webb could do this. These include looking for chemicals that lifeforms depend on, chemical byproducts produced by living organisms, chemicals essential to maintaining a stable climate, and chemicals that shouldn’t coexist.

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