Just when cosmologists have a workable theory for when and how galaxy collisions happened in the early Universe, something challenges it. In this case, the challenger is a collision of two massive galaxy clusters that combined to form a gigantic galaxy cluster.
They happened when the Universe was half its age and according to theory, that’s too early. The result of the collision is the El Gordo galaxy cluster. And, its existence challenges the best-accepted theory of cosmology, called the Lambda-cold dark matter (usually abbreviated as LCDM) standard model.
LCDM basically sets constraints (or parameters) on the origin and evolution of structure in the Universe. It has three parts. One is the cosmological constant Lambda (L). It’s associated with dark energy. The second denotes dark matter (labeled CDM). The third is basically ordinary matter (often referred to as “baryonic”). This is a simple way of expressing how the properties of the cosmos that we see came into existence. Essentially, it explains the large-scale structure of the Universe as seen in the Cosmic Microwave Background. It also describes the distribution of galaxies, the abundances of hydrogen, helium, and lithium, and the accelerating expansion of the universe.
So, how does El Gordo and its time-clashing birth process play havoc with LCDM? In that model, galaxies form first in the Universe. Then, later on, they begin to combine to create larger galaxies and clusters of galaxies. That takes time, so having them show up so early—as El Gordo did—in cosmic history is a problem.
Understanding Gigantic Galaxy Cluster Formation
A research team led by Elena Asencio from the University of Bonn, figured out when this collision happened by looking at simulations of the interaction. After detailed analysis, they estimated the mass of the resulting “El Gordo” cluster by using gravitational lensed light from background galaxies. This weak lensing and the mass of the cluster come from Hubble Space Telescope observations and compared with more recent studies by JWST.
The Bullet Cluster is another of several gigantic galaxy clusters challenging the Lambda-cold dark matter theory of structure formation in the early Universe. Credit: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.
The authors then searched through less detailed cosmological LCDM simulations covering a very large volume. They were hunting for simulated cluster pairs. The aim was to count how many of these are broadly analogous to what El Gordo was like shortly before the collision. The team used an innovative “lightcone tomography” method. It considers that more distant objects are viewed further back in time when there was less structure.
The results revealed that the tension with LCDM is very severe for any plausible collision velocity. Moreover, the remaining uncertainty in El Gordo’s mass isn’t as significant. But, there are still other issues to work out. One of them is timing in the early Universe. As mentioned, the collision that produced El Gordo happened too soon. You could make it happen if the collision takes place more quickly. And a simulation shows that. But, while it is possible to get a simulation that looks like El Gordo after the quick collision, such an event is too rare in LCDM. It would be very unusual to find two such massive clusters within striking distance so early in cosmic history. Then, they have to be headed towards each other at a really high speed. That really stretches credibility.
El Gordo and Other Clusters Raise the Tension
The team’s new study and the more precise mass measurement may lead to more efforts to simulate El Gordo to better understand this enigmatic object. That’s because Ascensio and her colleagues were able to get a reliable mass measurement for El Gordo. It actually seems to work better with the LCDM model. However, some issues remain. “This does reduce the tension with LCDM,” said Ascensio, “but it is still highly significant for any plausible collision velocity. Hundreds of detailed simulations
If Exoplanets Have Lightning, it’ll Complicate the Search for Life
Discovering exoplanets is almost routine now. We’ve found over 5,500 exoplanets, and the next step is to study their atmospheres and look for biosignatures. The James Webb Space Telescope is leading the way in that effort. But in some exoplanet atmospheres, lightning could make the JWST’s job more difficult by obscuring some potential biosignatures while amplifying others.
Detecting biosignatures in the atmospheres of distant planets is fraught with difficulties. They don’t advertise their presence, and the signals we receive from exoplanet atmospheres are complicated. New research adds another complication to the effort. It says that lightning can mask the presence of things like ozone, an indication that complex life could exist on a planet. It can also amplify the presence of compounds like methane, which is considered to be a promising biosignature.
The new research is “The effect of lightning on the atmospheric chemistry of exoplanets and potential biosignatures,” and it’s been accepted for publication in the journal Astronomy and Astrophysics. The lead author is Patrick Barth, a researcher from the Space Research Institute at the Austrian Academy of Sciences.
While we’ve discovered over 5,500 exoplanets, only 69 of them are in the potentially habitable zones around their stars. They’re rocky planets that receive enough energy from their stars to potentially maintain liquid water on their surfaces. Our search for biosignatures is focused on this small number of planets.
This is an artist’s illustration of the exoplanet TRAPPIST-1d, a potentially habitable exoplanet about 40 light-years away. Planets like these are prime targets for JWST’s spectrometry. Image Credit: By NASA/JPL-Caltech – Cropped from: PIA22093: TRAPPIST-1 Planet Lineup – Updated Feb. 2018, Public Domain, https://commons.wikimedia.org/w/index.php?curid=76364484
The important next step is to determine if these planets have atmospheres and then what the composition of those atmospheres is. The JWST is our most powerful instrument for these purposes. But in order to understand what the JWST shows us in distant atmospheres, we have to know what its signals tell us. Research like this helps scientists prepare for the JWST’s observations by alerting them to potential false positives and masked biosignatures.
This JWST spectra isn’t part of this research, but it shows how the powerful space telescope can
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Titan Probably Doesn’t Have the Amino Acids Needed for Life to Emerge
Does Saturn’s largest moon, Titan, possess the necessary ingredients for life to exist? This is what a recent study published in Astrobiology hopes to address as a team of international researchers led by Western University investigated if Titan, with its lakes of liquid methane and ethane, could possess the necessary organic materials, such as amino acids, that could be used to produce life on the small moon. This study holds the potential to help researchers and the public better understand the geochemical and biological processes necessary for life to emerge throughout the cosmos.
Along with its liquid lakes of methane and ethane, Titan is also strongly hypothesized to possess a subsurface liquid water ocean like Saturn’s icy moon, Enceladus, and Jupiter’s icy moon, Europa. For the study, the researchers used data from impact cratering from comets to estimate the number of organic molecules that could relocate from Titan’s surface to its subsurface liquid water ocean. The team hypothesized that when comets strike Titan’s surface, their icy materials would melt from the heat of the impact and mix with the surface organics, resulting in a unique mixture. However, the heavier liquid water would then sink to the subsurface, slowly filling the subsurface ocean over time.
Artist’s cutaway illustration displaying Titan’s subsurface ocean (blue). (Credit: NASA/JPL)
After accounting for a presumed annual number of cometary impacts on Titan’s surface throughout its billions of years of existence, the researchers then calculated how much water would make its way from the surface to the subsurface ocean. In the end, the team concluded that the amount of glycine, which is the most basic amino acid that forms the proteins to create life, was measured at no greater than 7,500 kilograms/year (16,530 pounds/year). This amount approximately equals the size of a smaller African forest elephant, hence indicating number of organic materials that exist on Titan is quite miniscule.
“One elephant per year of glycine into an ocean 12 times the volume of Earth’s oceans is not sufficient to sustain life,” said Dr. Catherine Neish, who is an associate professor in the Department of Earth Sciences at Western University and lead author of the study. “In the past, people often assumed that water equals life, but they neglected the fact that life needs other elements, in particular carbon.”
While Dr. Neish’s study presents somewhat dire implications for finding life on Titan, this study comes on the heels of a recent investigation into how organic hazes on ancient Earth could have contained the necessary building blocks of life, including nucleobases and amino acids, which could hold implications for finding life on Titan due to the moon’s hazy atmosphere. For this study, the researchers used laboratory experiments to determine that “warm little ponds” on ancient Earth could host nucleobases. Both studies offer profound insights into the processes responsible for both creating and sustaining life beyond Earth, and further research is undoubtedly required to better understand these processes.
One such research opportunity that could help solidify these studies could be NASA’s upcoming Dragonfly mission, which is a quadcopter designed to search Titan’s surface for signs of potential habitability with Dr. Neish assigned as a mission co-investigator. Dragonfly currently has a scheduled launch date of July 2028, arriving at Saturn’s largest moon sometime in 2034. While Dragonfly will not be the first aircraft on another world, as that honor goes to NASA’s Ingenuity Mars Helicopter, it will be the first aircraft to land and operate in the outer solar system. Dragonfly will launch more than 20 years after the European Space Agency’s Huygens probe landed on Titan in January 2005, beaming back images of rounded rocks that could have formed from liquid processes.
What new discoveries will scientists make about Titan and its potential for life in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
The post Titan Probably Doesn’t Have the Amino Acids Needed for Life to Emerge appeared first on Universe Today
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Astronomers Discover a New Meteor Shower. The Source is Comet 46P/Wirtanen
Like many of you, I love a good meteor shower. I have fond memories of the Leonid meteor storm back in 1999 when several hundred per hour were seen at peak. Sadly meteor storms are not that common unlike meteor showers of which, there are about 20 major showers per year. Wait, there’s another one and this time it comes from the debris left behind from Comet 46P/Wirtanen with an expected peak on December 12. Last year, 23 meteors were seen on that night that matched the location of the comets trail.
Comets (and some asteroids) leave a trail of debris behind them like a trail of celestial breadcrumbs. If the orbit of a comet crosses the orbit of the Earth then the particles from the debris (that are often no larger than grains of sand) collide with our atmosphere. At the immense speeds (of the order of 60 km per second, the particles falling through the atmosphere cause the gas to glow giving rise to the classic shooting star we see in the sky. Because the orbits of Earth and comets are relatively fixed, this process repeats itself every time we go through the same part of the orbit giving us the familiar annual meteor showers.
One such comet that it seems may become host to a new annual shower is Comet 46P/Wirtanen (46P). It nearly hit the headlines previously when it had been initially selected as the target for the Rosetta mission which, as you may recall, visited 67P/Churyumov-Gerasimenko instead. 46P is known as a short period comet taking 5.4 years to complete one orbit of the Sun. It is among the family of comets known as a Jupiter comet which has a most distant point from the Sun of between 5 and 6 astronomical units (1 AU is the average distance between the Sun and Earth). Observations have suggested it has a diameter of about 1.4km.
Comet 67P/Churyumov-Gerasimenko from Rosetta mission (Credit – NASA)
Due to the high levels of ice present in comets, it’s not unusual for active areas on their surface to appear as the ices sublimate into gasses or pockets of gas escape. Observations using the TRAPPIST telescope (The Transiting Planets and Planetesimals Small Telescope) suggest 40% of the surface is active which is higher than the usual 5-10% for Jupiter family comets. A recent study found the presence of mm sized dust particles in the comet’s coma which should be visible upon entering Earth’s atmosphere.
The orbit of 46P has a very low minimum orbit intersection distance (MOID) to Earth of just 0.071AU. The MOID between two objects that orbit a common point is the distance between the closest points of their orbits. The low MOID and the mm sized particles mean there is a high liklihood it could be the source of a meteor shower. Previous observations however have revealed no positive confirmation of peaks in 2017 and 2019.
During the 2017 and 2019 predictions, it seems the low velocity of the particles coupled with the radiant (the point of apparent origin of the shower) below the horizon suggest that visibility may have been severely limited. The radiant of this predicted shower is in the constellation Sculptor and the shower has been dubbed the Lambda Sculptorids.
The prediction for the 2023 shower, which predicted an encounter from a stream of debris from an outburst in 1974, suggested an outburst of meteors on December 12 between 12:08 and 20:06. A further outburst was predicted between 17:05 and 06:26 on December 13. The team who presented their findings in Astronomy and Astrophysics reported meteor activity as predicted and detected 23 meteors from the new shower on the night of December 12 2023. The team are now looking at the models to see what we might expect to see this year and whether Lamba Sculptorids need to be added to our list of annual meteor showers.
Source : Observations of the new meteor shower from comet 46P/Wirtanen
The post Astronomers Discover a New Meteor Shower. The Source is Comet 46P/Wirtanen appeared first on Universe Today.
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