News from the search for extraterrestrial life 9


In our universe

The universe (as far as we know) has now been mapped:

Full sky map showing the 56,000 galaxies of Cosmicflows-4 with distance measurements. Each dot represents a galaxy, and the color of the dot indicates the distance from us, with blue tones near and redder tones farther away. In this view, the obscuring plane of the Milky Way mostly corresponds to the edges but also intersects the center of the figure / University of Hawaii

With 56,000 galaxies, there would, in principle, be plenty of places to look for life: “Galaxies, such as the Milky Way, are the building blocks of the universe, each made up of several hundred billion stars. ” –

A big obstacle to exploration is, of course, the speed of light; most galaxies are many light years away and nothing travels faster than light. Incidentally, a group of astronomers recently claimed to have detected matter exceeding the speed of light.

We asked theoretical physicist Rob Sheldon about it and he said, “No, it’s not faster than the speed of light. Most superluminal objects resemble teasing a cat with a laser pointer. The light spot is moving incredibly fast for the cat, but in reality the light spot is not the same photons at point A as at point B. It’s only because the cat thinks the light spot is an object, that he thinks he has a superluminal effect. speeds. Sabine Hossenfelder explains it in more detail here.

Of course, we’re just as likely to find a life closer to home anyway.

Around our galaxy

Recently there has been some interest in orbiting planets white dwarf stars — old stars running out of fuel (but not any time soon). Stony Brook astrophysicist Paul Sutter comments that many of them host planets in their habitable zones: “Because the usual methods of looking for transits or changes in exoplanet motion won’t work for white dwarfs. , astronomers come up with a much simpler way to search for planets around white dwarfs: just look at them. sun and the Earth’s temperature). This means that the infrared light coming from a white dwarf would also contain some of the infrared light from the orbiting planet. Comparing this combined light with a white dwarf that we know is has no planets around it, we were able to detect the exoplanet., October 12, 2022 The document is in free access.

Meanwhile, we learn that “Webb sees organic molecules at the hearts of galaxies, surprisingly close to active supermassive black holes” (Evan Gough, Universe today, October 13, 2022): “The molecules in this study are polycyclic aromatic hydrocarbons (PAHs). They are important building blocks for prebiotic compounds. These compounds may have played a role in the early formation of life. But they are not only attractive to scientists because of their connection to life. When PAHs are illuminated by optical and UV radiation from stars, they are excited and are very bright in the infrared emission bands. So observing them tells astronomers a lot about the conditions inside the galaxy.

Is methyl bromide an ideal biosignature?

“Methylation is so prevalent on Earth that we expect life anywhere else to achieve it. Most cells have mechanisms to expel harmful substances,” said PhD Michaela Leung. student at the University of California, Riverside, in the Alternative Earths and NExSS Virtual Planetary Laboratory teams of NASA.

A methylated gas, methyl bromide (CH3Br) has several advantages over other gases traditionally targeted in the search for life outside our solar system.

In a new study, Leung and his colleagues explored and quantified these benefits. Scientific News (October 11, 2022) The document is open access.

Methyl bromide is less likely to be created by anything other than life than some other methyls. The researchers think it would be easier to detect MB around an M dwarf star than here in the solar system.

Finally, could there be life on rogue planets – planets that stray from the stars?

Harvard astronomer Avi Loeb, known for his walks on the wild side, tells us at Medium, “Could rogue planets harbor life? If Earth had been kicked out of the solar system, its oceans would have frozen. In a paper I wrote with my former post-doc, Manasvi Lingam, we showed that a landmass ocean world would have developed a layer of ice tens of kilometers thick, but that liquid water could have existed under the ice. Liquid water is heated by the radioactivity of isotopes from the rocky core of the planet. Nutrients and hydrothermal vents at the bottom of the ocean could give rise to single-celled organisms and bacteria similar to those in Earth’s early history. However, without an oxygen-rich atmosphere above the ocean and some landmasses, complex life in the form of multicellular organisms is unlikely to thrive on these rogue planets, unless they are not. pre-existed before the planet was driven from its parent. daycare.” (October 3, 2022)

We’ll see if life is possible under these circumstances, but NASA thinks rogue planets may be plentiful in our galaxy.

In our solar system

NASA is preparing a set of eight instruments for the Ocean Worlds Life Surveyor (OWLS) to search for life on Jupiter’s moon Europa and Saturn’s moon Enceladus.

In the 2030s, the Europa Clipper should be able to “spot shallow lakes erupting icy ‘lava'” – a good place to check for life.

To Universe today, Evan Gough offers a reflection: “If Earth were an exoplanet, it would still be difficult to determine if there is life here”: “A new study shows that finding evidence of life on Earth may depend on the season that extraterrestrial astronomers observe. (October 14, 2022) Here’s the open-access study that explains why.

Insofar as the universe seems well tuned for life, it is reasonable to hope to find life on other planets, even if even today the search is not easy. Speaking of fine tuning, this The New Atlantis abstract:

Since physicists haven’t uncovered a deep underlying reason why these constants are what they are, we might well ask the seemingly simple question: what if they were different? What would happen in a hypothetical universe where the fundamental constants of nature had other values?

There is nothing mathematically wrong with these hypothetical universes. But there is one thing they almost always lack: life. Or, indeed, anything remotely resembling life. Or even the complexity that life relies on to store information, gather nutrients and reproduce. A universe that has only small changes in the fundamental constants might not possess any of the chemical bonds that give us molecules, so say goodbye to DNA, along with rocks, water, and planets. Further adjustments could make it impossible to form stars or even atoms. And with certain values ​​for the physical constants, the universe would have disappeared in a fraction of a second. That the constants are all arranged in what is, mathematically speaking, the most improbable combination that makes possible our grand, complex, life-bearing universe is what physicists mean when they speak of the “fine-tuning” of the universe for life.

Luke A. Barnes“The fine tuning of the laws of nature” at The New Atlantis (Fall 2015)

Nothing has changed since, so just keep looking…!

Since last week : News from the Search for Extraterrestrial Life 8. Saturn’s moon Enceladus may contain abundant phosphorus, essential for life. An experiment with bacteria and algae shows that planets orbiting the most common type of star could receive enough light to support life.


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