This day in history November 16, 2019-Hello to aliens?
8 responses | 0 likes
Started by metmike - Nov. 16, 2019, 11:19 p.m.

Read, learn and remember history. Pick out some good ones.


https://en.wikipedia.org/wiki/November_16


1974 – The Arecibo message is broadcast from the Arecibo Radio Telescope in Puerto Rico. It was aimed at the current location of the globular star cluster Messier 13 some 25,000 light years away. The message will reach empty space by the time it finally arrives since the cluster will have changed position.

Comments
By metmike - Nov. 16, 2019, 11:23 p.m.
Like Reply

Arecibo message

https://en.wikipedia.org/wiki/Arecibo_message

The Arecibo message is a 1974 interstellar radio message carrying basic information about humanity and Earth sent to globular star cluster M13 in the hope that extraterrestrial intelligence might receive and decipher it. The message was broadcast into space a single time via frequency modulated radio waves at a ceremony to mark the remodeling of the Arecibo radio telescope in Puerto Rico on 16 November 1974.[1][2] The message was aimed at the current location of M13 some 25,000 light years away because M13 was a large and close collection of stars that was available in the sky at the time and place of the ceremony.


Since it will take nearly 25,000 years for the message to reach its intended destination (and an additional 25,000 years for any reply), the Arecibo message is viewed as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials. In fact, the core of M13, to which the message was aimed, will no longer be in that location when the message arrives.[1] However, as the proper motion of M13 is small, the message will still arrive near the center of the cluster.[7] According to the Cornell News press release of November 12, 1999, the real purpose of the message was not to make contact, but to demonstrate the capabilities of newly installed equipment at the radio telescope

By metmike - Nov. 16, 2019, 11:26 p.m.
Like Reply

Is there life on other planets?

https://exoplanets.nasa.gov/faq/5/is-there-life-on-other-planets/

The ultimate goal of NASA's exoplanet program is to find unmistakable signs of current life on a planet beyond Earth. How soon that can happen depends on two unknowns: the prevalence of life in the galaxy and how lucky we get as we take those first, tentative, exploratory steps.

By metmike - Nov. 16, 2019, 11:28 p.m.
Like Reply

Signs of Alien Life Will Be Found by 2025, NASA's Chief Scientist Predicts


https://www.space.com/29041-alien-life-evidence-by-2025-nasa.html

By metmike - Nov. 16, 2019, 11:32 p.m.
Like Reply

Drake Equation: Estimating the Odds of Finding E.T.

https://www.space.com/25219-drake-equation.html


The Drake Equation is used to estimate the number of communicating civilizations in the cosmos, or more simply put, the odds of finding intelligent life in the universe.

First proposed by radio astronomer Frank Drake in 1961, the equation calculates the number of communicating civilizations by multiplying several variables. It's usually written, according to the Search for Extraterrestrial Intelligence (SETI), as:

N = The number of civilizations in the Milky Way galaxy whose electromagnetic emissions are detectable.

R* = The rate of formation of stars suitable for the development of intelligent life.

fp = The fraction of those stars with planetary systems.

ne = The number of planets, per solar system, with an environment suitable for life.

fl = The fraction of suitable planets on which life actually appears.

fi = The fraction of life bearing planets on which intelligent life emerges.

fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.

L = The length of time such civilizations release detectable signals into space.

The challenge (at least for now) is that astronomers don't have firm numbers on any of those variables, so any calculation of the Drake Equation remains a rough estimate for now. There have been, however, discoveries in some of these fields that give astronomers a better chance of finding the answer.

The recent discoveries of rocky worlds near Proxima Centauri (a star of the Alpha Centauri system) and TRAPPIST-1 have increased the public's attention on the search for life. These stars, however, are red dwarfs that might be too volatile for life. More study is needed to understand where life might be possible, and whether it could persist long enough to communicate with other civilizations.

By metmike - Nov. 16, 2019, 11:35 p.m.
Like Reply

The Drake Equation: What Are the Odds That Aliens Exist?

http://blogs.discovermagazine.com/crux/2018/10/19/drake-equation-odds-aliens-exist/


Looking for Life

The next question is, once a star has planets, how many of them are capable of supporting life? This is where we start hitting roadblocks. We only know of one planet that does have life. We can argue about whether Mars could have in the past. We can define habitable zones where planets can support liquid water on their surfaces, but what about worlds like Europa, with subsurface oceans? What about tidally locked planets around dwarf stars? The number is highly variable. We think it’s somewhere between 3 and 5 right now, but that could be higher or very much lower, depending on how you define habitability.

And then we start really plunging into the unknown. What fraction of planets that could support life actually develop living creatures? Again, we know of just one so far that has. This number is very much an unknown. Is this 100%? Or do we count Titan and Europa and Mars and Venus and say it’s only 20% in our solar system?

Past this, what fraction of planets with life host intelligent life? Possible good luck here: 100% of the planets with life we know of have intelligent life. On the other hand, out of the millions of species that have existed in Earth’s history, only one of them has achieved sentience. So maybe the odds are not so great. Maybe there are a lot of planets with giraffes, but none others with humans.

By metmike - Nov. 16, 2019, 11:37 p.m.
Like Reply

https://www.space.com/41080-alien-life-may-be-rare-today.html

In 1950, Italian-American physicist Enrico Fermi looked to the skies and asked, "Where are they?" If the universe is filled with alien civilizations, why have none of them contacted Earth? The question, referred to as the Fermi paradox, provided the fuel for the Drake equation.

The Drake equation has never sought a definite number. Instead, it has been used to make a rough estimate of the number of detectable civilizations in the Milky Way (N). According to the equation,

N = RfpncflfifcL

That number is based on the rate of star formation per year (R), the fraction of stars with planets (fp), the number of habitable planets per system of planets (nc), the fraction of those planets with life (fl), the fraction of life that is intelligent (fi), the fraction of intelligent civilizations that are detectable (fc), and the average lifetime of such civilizations in years (L).

By metmike - Nov. 16, 2019, 11:45 p.m.
Like Reply

A Goldilocks zone for planet size

Research redefines lower limit for planet size habitability

https://www.sciencedaily.com/releases/2019/09/190911142740.htm]

Generally, planets are considered habitable if they can maintain surface liquid water long enough to allow for the evolution of life, conservatively about one billion years. Astronomers hunt for these habitable planets within specific distances of certain types of stars -- stars that are smaller, cooler and lower mass than our Sun have a habitable zone much closer than larger, hotter stars.

When planets get too small, however, they lose their atmospheres altogether and the liquid surface water either freezes or vaporizes. The researchers demonstrated that there is a critical size below which a planet can never be habitable, meaning the habitable zone is bounded not only in space, but also in planet size.

The researchers found that the critical size is about 2.7 percent the mass of Earth. If an object is smaller than 2.7 percent the mass of Earth, its atmosphere will escape before it ever has the chance to develop surface liquid water, similar to what happens to comets in the Solar System today. To put that into context, the Moon is 1.2 percent of Earth mass and Mercury is 5.53 percent.

By metmike - Nov. 16, 2019, 11:50 p.m.
Like Reply

Circumstellar habitable zone

https://en.wikipedia.org/wiki/Circumstellar_habitable_zone

In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.[1][2][3][4][5] The bounds of the CHZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to Earth's biosphere, the nature of the CHZ and the objects within it may be instrumental in determining the scope and distribution of planets capable of supporting Earth-like extraterrestrial life and intelligence.

The habitable zone is also called the Goldilocks zone, a metaphor of the children's fairy tale of "Goldilocks and the Three Bears", in which a little girl chooses from sets of three items, ignoring the ones that are too extreme (large or small, hot or cold, etc.), and settling on the one in the middle, which is "just right".


 

Natural shielding against space weather, such as the magnetosphere depicted in this artistic rendition, may be required for planets to sustain surface water for prolonged periods.