The Astronomy Thread

[Flinn]

Euclid test images tease of riches to come.

The latest ESA space telescope, Euclid, has eventually reached the L2 point and it's now under calibration procedures. After a first few hours of panic due to an unexpected issue with sun light contaminating the VIS (Euclid’s VISible instrument), which has been found to probably be a small gap and solved by changing orientation, the telescope has started to send back images both in the visible light and infrared.





The NISP instrument (Euclid’s Near-Infrared Spectrometer and Photometer) is also capable of catching images in "grism mode"



as the same ESA scientists say

This special way of looking at the Universe allows us to determine what each galaxy is made of, which allows us to evaluate its distance from Earth.

Anyways, those are just the first test images, so more and better are expected to come in the next months.

edit: forgot to say that Euclid's main mission is to study both dark matter and dark energy.

As of today there are a total of 26 working space "telescopes" in orbit (both Earth's orbit or around one of the Lagrange points), 11 more are planned to be launched in 4 years from now, with a few more grand projects being developed for the following decades.

[Flinn]

Begging anyone's pardon if I'm back on this matter again, but what is due is due

As per the possible secondary issues, there's one thing to consider: it's not just about "pushing them away", but rather about "putting them in a new orbit that is safe for the Earth and will not interact with any other body and that might cause secondary, unpredictable issues", that is. On this regard we are absolutely far from being able to grant that it will be the latter, for 2 reasons mainly: first, we can't know with precision the mass of an asteroid (an absolutely must to have data if one wants to be as precise as possible in knowing in advance the result of a calculated impact) if we won't send another probe to investigate the asteroid, and that will add more money and time needs to the mission, rendering it even less likely to be on time, so we are likely going to shot in the dark and just hope that we don't have made it worse; second one, is the effective composition, size and direction of debris that's impossible to calculate, due to both lack of precise info on composition, size, speed, mass, rotation etc of the asteroid, coupled with the computing power needed to make that calculation that I doubt exists today on Earth.

Asteroid behaving unexpectedly after Nasa's deliberate DART crash.

To be fair, Nasa already mentioned that they were studying the secondary effects of the debris tail a few weeks ago. It does not change the fact that the system as it is today leaves huge gaps in terms of "precision" (as a general meaning I mean), which definitely is a major issue for a mission which claims to have proven that Nasa can successfully defend Earth from asteroid impacts, when what they actually did was to shot in the dark, literally.

IMO, of the 3 possible solutions* studied over the years, this one is the less good and the one more likely to cause secondary unpredictable effects, but also the cheapest one, that's why it was the only one to be tested so far.

* The other two "proposed" systems are either nuking the asteroid or using a probe/solar sail to push them away. The former presents similar issues with DART for what concerns unpredictable secondary effects (high chances of not being able to vaporize completely the asteroid and thus sending debris at very high speed running around the Solar system), the latter would be an extremely complex system to develop but it's probably the best solution at all: attaching a probe to an asteroid and thus being able to modify it's orbit (possibly multiple times) without creating secondary unpredictable issues.

But really, the main issue here is that as long as we won't be able to define with precision in advance what an asteroid is composed of, its mass, rotation, speed etc, so the asteroid/comet characteristics, every attempt to modify/destroy those who might represent a menace to Earth will have a certain degree of unpredictability, that could make the mission fail or even make the situation worse.

[conon394]

But really, the main issue here is that as long as we won't be able to define with precision in advance what an asteroid is composed of, its mass, rotation, speed etc, so the asteroid/comet characteristics, every attempt to modify/destroy those who might represent a menace to Earth will have a certain degree of unpredictability, that could make the mission fail or even make the situation worse.

Which of course to my mind just means its worth tests every alternative multiple times.

[sumskilz]

From a recent NASA post (my emphasis):

A new investigation with NASA’s James Webb Space Telescope into K2-18 b, an exoplanet 8.6 times as massive as Earth, has revealed the presence of carbon-bearing molecules including methane and carbon dioxide. Webb’s discovery adds to recent studies suggesting that K2-18 b could be a Hycean exoplanet, one which has the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface.

The first insight into the atmospheric properties of this habitable-zone exoplanet came from observations with NASA’s Hubble Space Telescope, which prompted further studies that have since changed our understanding of the system.

K2-18 b orbits the cool dwarf star K2-18 in the habitable zone and lies 120 light-years from Earth in the constellation Leo. Exoplanets such as K2-18 b, which have sizes between those of Earth and Neptune, are unlike anything in our solar system. This lack of equivalent nearby planets means that these ‘sub-Neptunes’ are poorly understood, and the nature of their atmospheres is a matter of active debate among astronomers.

The suggestion that the sub-Neptune K2-18 b could be a Hycean exoplanet is intriguing, as some astronomers believe that these worlds are promising environments to search for evidence for life on exoplanets.

"Our findings underscore the importance of considering diverse habitable environments in the search for life elsewhere," explained Nikku Madhusudhan, an astronomer at the University of Cambridge and lead author of the paper announcing these results. "Traditionally, the search for life on exoplanets has focused primarily on smaller rocky planets, but the larger Hycean worlds are significantly more conducive to atmospheric observations."

The abundance of methane and carbon dioxide, and shortage of ammonia, support the hypothesis that there may be a water ocean underneath a hydrogen-rich atmosphere in K2-18 b. These initial Webb observations also provided a possible detection of a molecule called dimethyl sulfide (DMS). On Earth, this is only produced by life. The bulk of the DMS in Earth’s atmosphere is emitted from phytoplankton in marine environments.

Caveats:

The inference of DMS is less robust and requires further validation. “Upcoming Webb observations should be able to confirm if DMS is indeed present in the atmosphere of K2-18 b at significant levels,” explained Madhusudhan.

While K2-18 b lies in the habitable zone, and is now known to harbor carbon-bearing molecules, this does not necessarily mean that the planet can support life. The planet's large size — with a radius 2.6 times the radius of Earth — means that the planet’s interior likely contains a large mantle of high-pressure ice, like Neptune, but with a thinner hydrogen-rich atmosphere and an ocean surface. Hycean worlds are predicted to have oceans of water. However, it is also possible that the ocean is too hot to be habitable or be liquid.

[Flinn]

HH 211 - WEBB did it again!

Spoiler for large image: 

Herbig-Haro objects (see the wikipedia page for reference) have been studied extensively by various telescopes (mainly Hubble and Spitzer) but never before with such a level of details. The HH 211 in particular is situated at approx 1000 light years from us (so relatively close in terms of astronomic distances) and it's part of the IC 348 nebula, within the Perseus Constellation.

The HH phase is at an early stage of stellar formation (approx 100-200 million years age), and is estimated to last for about 100.000 years. In this phase the new star has already started the nuclear fusion, but it's still accumulating material from the accretion disk. As it is possible to see from the image, the quantity of material that the star is "swallowing" is so high that it basically blackens any light emission (the black area in the center): the two jets of material from the poles are the result of this very process (the star is actually expelling a large percentage of the gas that it's falling on it), while the "visual" effect are in fact caused by the interaction of those expelled gases (at a faster than sound speed) with the rest of the gases already present in the surrounding space.

The image in itself is not only an eye candy, but it's also extremely useful for scientists who are studying the earlier phases of stars' life (a field were we still have to learn a lot, a large part of the mechanics involved are still not fully explained). Previously to this phase there's the so called Bok globule, which is considered to be the very earliest stage of star formation (when the gases are already collapsing but the nuclear fusion hasn't started yet).
If you want to know more, here you can find a general introduction to the matter of star formation.

For a deeper look at the image, follow this link; just click on Zoom image (bottom left) and enjoy it.

[Flinn]

From a recent NASA post (my emphasis):

Caveats:

Planned to reply before to this and then forgot

However, while the finding of DMS is undoubtedly interesting and unique in some ways, it's still very far to be a definitive evidence of life, sadly. First of all, it needs to be confirmed and better measured; second, even though on Earth DMS is a byproduct of life, it doesn't mean that it has to be so everywhere else: probable? yes! certain? not!.. because if there's something we are learning the most as we keep exploring the space, is that variables are absolutely infinite in the Universe, thus it's wise to not to give anything as accounted just because it is so somewhere else. But again, this finding is very interesting, as it is the first time ever for DMS.

As per the actual habitability of K2-18 b, the main problem I see is that it orbits a Red Dwarf, which, despite being the most abundant kind of star, is not very likely to be hosting habitable planets or anyways planets that can sustain life in general.

The theorized habitability of red dwarf systems is determined by a large number of factors. Modern evidence indicates that planets in red dwarf systems are unlikely to be habitable, due to their low stellar flux, high probability of tidal locking and thus likely lack of magnetospheres and atmospheres, small circumstellar habitable zones and the high stellar variation experienced by planets of red dwarf stars, impeding their planetary habitability. However, the ubiquity and longevity of red dwarfs could provide ample opportunity to realize any small possibility of habitability.

A major impediment to life developing in these systems is the intense tidal heating caused by the proximity of planets to their host red dwarfs.[1][2] Other tidal effects reduce the probability of life around red dwarfs, such as the extreme temperature differences created by one side of habitable-zone planets permanently facing the star, and the other perpetually turned away and lack of planetary axial tilts. Still, a planetary atmosphere may redistribute the heat, making temperatures more uniform.[3][2] Non-tidal factors further reduce the prospects for life in red-dwarf systems, such as extreme stellar variation, spectral energy distributions shifted to the infrared relative to the Sun, (though a planetary magnetic field could protect from these flares) and small circumstellar habitable zones due to low light output.[2]

There are, however, a few factors that could increase the likelihood of life on red dwarf planets. Intense cloud formation on the star-facing side of a tidally locked planet may reduce overall thermal flux and drastically reduce equilibrium temperature differences between the two sides of the planet.[4] In addition, the sheer number of red dwarfs statistically increases the probability that there might exist habitable planets orbiting some of them. Red dwarfs account for about 85% of stars in the Milky Way[5][6] and the vast majority of stars in spiral and elliptical galaxies. There are expected to be tens of billions of super-Earth planets in the habitable zones of red dwarf stars in the Milky Way.[7]

Other than this, K2-18 b is said to be an Hycean planet (meaning a body of iced water covered by a planet wide ocean), thus again very unlikely to be able to sustain evolved life.

There are a lot of "ifs" when it comes to what could be a "habitable" planet, honestly, we are just a the very beginning of our adventure on that regard. Some scientists make this comparison, with regards of spotting life in the Universe: so far we have only sampled a cup of water over the whole of the oceans, seas, rivers and any other body of water on Earth representing the observable Universe and we have looked at it from the top of a skyscraper while the cup remains at the ground level.

In other words is not only extremely unlikely that we would have spotted any form of life at all, but in case it should have been a very evolved one (you could see a fish in a cap of water, not literally seeing it, but you can spot it moving even from afar.. and that's what we could see now, the indirect evidence of life, and the more advanced this life is, the more likely it is to have caused significative and traceable modifications to the atmosphere of the planet), and that kind of life is even less likely to be present anywhere close to us (or not, until we found one we won't really know). However, our limited experience also means that we still lack all the possible methods of spotting life from afar (or even simply spotting planets).

As I said, we are really at the very beginning of this adventure and we have still know to learn almost everything about it... although one thing I think we have learned: variability (see it as infinite possibilities) is the rule in the Universe, thus no matter what, when we'll find life, it will be where we would not have expected it and in form that we most likely haven't even imagined yet.

[Flinn]

ESA's Euclid Space Telescope, because there's not just WEBB.

Euclid space telescope is releasing the first images, the one above in particular is indicative of the special characteristics of this telescope, or the ability to scan very large areas of the sky with an unprecedented level of details. While WEBB (and Hubble before) aims at more detailed and zoomed images (among the other things, of course), Euclid is meant to give a wider, and yet detailed, image of the Universe. For instance, the image above, is showing 1000 galaxies in close up and a 100.000 more on the background (up to 10 billions light years far, some of them were completely unknown before this shoot was taken). Euclid has been put in space by a Falcon 9 launcher this past July, and later placed itself in the L2 point (where both WEBB and GAIA are already located, at approx 1.5 million Km from Earth); mission is expected to last for at the least 6 years.

Mission objectives
Euclid is designed to explore the evolution of the dark Universe. It will make a 3D-map of the Universe (with time as the third dimension) by observing billions of galaxies out to 10 billion light-years, across more than a third of the sky.

and

Key questions
Euclid is designed to tackle some of the most important questions in cosmology:

What is the structure and history of the cosmic web?
What is the nature of dark matter?
How has the expansion of the Universe changed over time?
What is the nature of dark energy?
Is our understanding of gravity complete?

All those questions are absolutely central to unravel what we still fail to understand of the Universe and, in practical terms, of the reality we live in. To put things in perspective, if we want to make a rough calculation, we could say that we don't know, as of today, what 95% of the Universe is made of.. yes, 95%. This is the combined value of Dark Matter and Dark Energy.. but what are those?

In simplistic terms: Dark Matter (circa 27%) is a form of matter that only interacts with the regular matter via gravity (aka it shapes the distribution of mass in the Universe but do not interact with any electromagnetic force), while Dark Energy (circa 68%) is the force that makes the Universe expand. I'm not going into detailed explanation of both, that would require many pages of discussion and a certain degree of understanding of Physics (in particular of quantum mechanic), that only little are interested in and even less fully understand (if you really want to expand, check here and here). What is important in this instance, is the fact that our ignorance of the Universe, is, literally, overwhelmingly superior to our knowledge of the same: that is not surprising to be honest, considering that we have started to study it in details only a few decades ago. The very idea of "dark" matter and energy does define the concept of something still obscure to us, that we lack the basics to understand still... we are now in that phase where we are understanding the basic laws that regulate it and we are thus literally inventing and developing the tools necessary to dug deeper into this knowledge.

Euclid will be a heck of a tool in that regard, of course it integrates and combines with all the other tools that we are now in operation (both in space or at ground level) as well as with those who operated in the past (ie. Spitzer) or that will operare in the future (i.e. ATHENA); one thing is certain, the quantity of information which Euclid and the other tools are pouring in is absolutely overwhelming and will increase exponentially in the future, to the point that our real main concern will be (and probably already is) by whom and how fast that data will be analyzed and, mostly important, understood.. AI and quantum computing will certainly help, but my feeling is that the unique ability of the human mind to put facts in perspective as well as taking an "oblique" view of reality, will play a fundamental role in unfolding the understanding of the Universe.

[Gaius Baltar]

Total eclipse across the central US on April 8th, 2024.