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Astronomy Megathread 🌌🔭
- Thread starter Quick_Silver
- Start date
------ Post added on Nov 3, 2021 at 9:59 AM
------ Post added on Nov 4, 2021 at 11:00 AM
Once again an asteroid barely missed Earth last week, and no one knew it was coming. 
An asteroid about the size of a refrigerator shot past Earth last week, and astronomers didn't know the object existed until hours after it was gone.
It was a close call (from a cosmic perspective); the space rock's trajectory on Oct. 24 carried it over Antarctica within 1,800 miles (3,000 kilometers) of Earth — closer than some satellites — making it the third-closest asteroid to approach the planet without actually hitting it.
Scientists were unaware of the object, dubbed Asteroid 2021 UA1, because it approached Earth's daytime side from the direction of the sun, so the comparatively dim and small visitor went undetected until about 4 hours after passing by at its closest point.
But with a diameter of just 6.6 feet (2 meters), UA1 was too small to pose a threat. Even if it had struck Earth, most of its rocky body would have burned away in the atmosphere before it could hit the ground.
For an object to be considered dangerous, it has to measure at least 460 feet (140 m) in diameter, NASA says. UA1 may not have been big enough to threaten the planet, but what about bigger asteroids that might be headed our way? NASA is also investigating defensive technologies for protecting Earth from possible collisions with larger space rocks, through deflection.
The Double Asteroid Redirection Test (DART), scheduled to launch Nov. 24, will test a method for diverting asteroids by hitting them with high-speed remote-controlled spaceships.
Scientists will send the DART spacecraft hurtling into the near-Earth binary asteroid Didymos, which is shaped like a spinning top and has two bodies; the bigger one measures about 2,600 feet (780 m) in diameter, and its smaller moonlet measures around 520 feet (160 m) in diameter.
Cepheid Variables - Henrietta Swan Leavitt - The unnoticed US woman who gave the world the "Universal Cosmic Yardstick" to measure the Universe.
Henrietta Swan Leavitt was one of many women "computers" who worked at Harvard University, cataloging stars around the turn of the last century. Women could be paid less than men, and were generally seen as detail-oriented and suited for the often boring and rote work of data analysis. They were also barred from operating Harvard’s telescopes, limiting their other astronomical options. Leavitt’s particular assignment was Cepheid variable stars. It was one of the Harvard Observatory's great projects, begun by Edward C. Pickering, of determining the brightnesses of all measurable stars.
A Cepheid variable star is a type that pulsates and vary regularly in brightness in periods ranging from a few days to several months. A Cepheid progresses through a complete cycle from maximum brightness to minimum and then back to maximum again. Outer layer pulsations alternately increase and decrease the star's size and temperature, both of which affect the star's luminosity.
The "Polaris" (or the "Pole Star"/"North Star") is a Cepheid variable.
What Leavitt discovered in 1908 was that the fundamental brightness of a Cepheid is directly related to its pulse rate. This means that if two Cepheid stars have the same pulse rate but one is dimmer than the other, then we can tell that the dimmer one is farther from us. Since there is a precise relationship between distance and brightness – like gravity it is an inverse-square law – precise distances to all Cepheid stars were now within the grasp of astronomers.
Leavitt published her work and pointed out that someone merely needed to work out the "Parallax" (a way of calculating distance that works only on very nearby stars) of a tiny handful of her variable stars to calibrate the system, and turn her rough picture of “near or far” into an accurate map complete with marked distances. Within a year, a Danish astronomer named Ejnar Hertzsprung did exactly this.
Sadly, as with many other female scientists of her time, Leavitt's contributions to her field went largely unacknowledged by the scientific peers. Her work went unnoticed for nearly a decade. She never received any fame for her work. She was made head of stellar photometry at the Harvard College Observatory in 1921, but did not live long enough to enjoy her new role. She died of stomach cancer on the 12 December 1921 aged 53 years.
It was Edwin Hubble who used her work and showed how large the Universe is.
Today there are efforts to acknowledge her work and offer due recognition, as one article mentions -
"As she had lived quietly, unnoticed, so her death left barely a ripple among her peers: to the extent that when, in 1925, the Swedish mathematician Gösta Mittag-Leffler wrote her a letter:
'Honoured Miss Leavitt, your admirable discovery ... has impressed me so deeply that I feel seriously inclined to nominate you to the Nobel Prize in Physics for 1926,' he had to be informed that she had in fact been dead for four years. As the Nobel Prize is not awarded posthumously, Leavitt never received her nomination."
Using Leavitt's Law - or the Period-Luminosity relationship that she discovered, others later calculated the distances to Cepheid variables in galaxies outside our own Milky Way. In doing so, they discovered that our Universe is expanding, starting from a single point more than 14 billion years ago at the Big Bang - a discovery that would have never been possible without the Leavitt Law.
The most dramatic application was Hubble’s use in 1924 of a Cepheid variable to determine the distance to the great nebula in Andromeda, which was the first distance measurement for a galaxy outside the Milky Way.
Henrietta Swan Leavitt was one of many women "computers" who worked at Harvard University, cataloging stars around the turn of the last century. Women could be paid less than men, and were generally seen as detail-oriented and suited for the often boring and rote work of data analysis. They were also barred from operating Harvard’s telescopes, limiting their other astronomical options. Leavitt’s particular assignment was Cepheid variable stars. It was one of the Harvard Observatory's great projects, begun by Edward C. Pickering, of determining the brightnesses of all measurable stars.
A Cepheid variable star is a type that pulsates and vary regularly in brightness in periods ranging from a few days to several months. A Cepheid progresses through a complete cycle from maximum brightness to minimum and then back to maximum again. Outer layer pulsations alternately increase and decrease the star's size and temperature, both of which affect the star's luminosity.
The "Polaris" (or the "Pole Star"/"North Star") is a Cepheid variable.
What Leavitt discovered in 1908 was that the fundamental brightness of a Cepheid is directly related to its pulse rate. This means that if two Cepheid stars have the same pulse rate but one is dimmer than the other, then we can tell that the dimmer one is farther from us. Since there is a precise relationship between distance and brightness – like gravity it is an inverse-square law – precise distances to all Cepheid stars were now within the grasp of astronomers.
Leavitt published her work and pointed out that someone merely needed to work out the "Parallax" (a way of calculating distance that works only on very nearby stars) of a tiny handful of her variable stars to calibrate the system, and turn her rough picture of “near or far” into an accurate map complete with marked distances. Within a year, a Danish astronomer named Ejnar Hertzsprung did exactly this.
Sadly, as with many other female scientists of her time, Leavitt's contributions to her field went largely unacknowledged by the scientific peers. Her work went unnoticed for nearly a decade. She never received any fame for her work. She was made head of stellar photometry at the Harvard College Observatory in 1921, but did not live long enough to enjoy her new role. She died of stomach cancer on the 12 December 1921 aged 53 years.
It was Edwin Hubble who used her work and showed how large the Universe is.
Today there are efforts to acknowledge her work and offer due recognition, as one article mentions -
"As she had lived quietly, unnoticed, so her death left barely a ripple among her peers: to the extent that when, in 1925, the Swedish mathematician Gösta Mittag-Leffler wrote her a letter:
'Honoured Miss Leavitt, your admirable discovery ... has impressed me so deeply that I feel seriously inclined to nominate you to the Nobel Prize in Physics for 1926,' he had to be informed that she had in fact been dead for four years. As the Nobel Prize is not awarded posthumously, Leavitt never received her nomination."
Using Leavitt's Law - or the Period-Luminosity relationship that she discovered, others later calculated the distances to Cepheid variables in galaxies outside our own Milky Way. In doing so, they discovered that our Universe is expanding, starting from a single point more than 14 billion years ago at the Big Bang - a discovery that would have never been possible without the Leavitt Law.
The most dramatic application was Hubble’s use in 1924 of a Cepheid variable to determine the distance to the great nebula in Andromeda, which was the first distance measurement for a galaxy outside the Milky Way.
Artemis program
The Artemis program is a United States-led international human spaceflight program. Its primary goal is to return humans to the Moon, specifically the lunar south pole, by 2025. If successful, it will include the first crewed lunar landing mission since Apollo 17 in 1972, the last lunar flight of the Apollo program.
NASA to provide Artemis update
The Artemis program is a United States-led international human spaceflight program. Its primary goal is to return humans to the Moon, specifically the lunar south pole, by 2025. If successful, it will include the first crewed lunar landing mission since Apollo 17 in 1972, the last lunar flight of the Apollo program.
NASA to provide Artemis update
Great Observatories - A new video on the James Webb Telescope & it's capabilities.
NASA's SpaceX Crew-3 Astronauts Arrive at the Space Station
------ Post added on Nov 12, 2021 at 5:08 PM
The Earth May Just Have A Temporary Second Moon In Its Orbit - For the next 300 years.
Our planet may also have a second moon first discovered in 2016, according to a new study.
It's called Kamo’oalewa, which in Hawaiian means moving celestial object, and it obviously circles the Earth. But it does not follow a traditional path instead it circles in a corkscrew-like trajectory. It's also tiny measuring a mere 50 m (164 ft) across. The scientists who discovered it describe its orbit as a dance. “It’s primarily influenced just by the sun’s gravity, but this pattern shows up because it’s also — but not quite — on an Earth-like orbit. So it’s this sort of odd dance,”
A graduate student Ben Sharkey of the Lunar and Planetary Laboratory at the University of Arizona, the lead author of the paper.
Where does this wondrous second moon come from? Well, the researchers write in their study that they believe it to be "lunar material." That is not hard to believe. After all, our moon is constantly being bombarded by celestial objects, it's only logical that a piece of it might go flying off and then find itself in the vicinity of Earth.
To prove this point, Sharkey turned to a published paper on lunar samples brought back by the Apollo 14 mission in 1971. He found that when he compared the data he was getting in his telescope with what the geologists from the first study surfaced in their rock labs, the results matched.
This means that not only is Kamo’oalewa a second moon to our Earth, but it is also actually a small part of our already existing moon. And that makes it even more wonderful.
However, our extra moon won't stay close to us for very long. Sharkey and others estimate that after 300 years it will break its orbit and go off on its own. Wherever it heads next, we wish it luck on its travels.
Channel එක නම් මගේ 
. මාස ගාණකට පස්සේ පොඩි වීඩියෝ එකක් හැදුවා. 
. මාස ගාණකට පස්සේ පොඩි වීඩියෝ එකක් හැදුවා.
Comet Leonard is the comet of the year. It will be visible to naked eyes in December 2021. Comet A1 Leonard was discovered on 3rd January 2021 and at that time, it was about 5 astronomical units away. But now, the comet has come closer to the Earth and will be easily visible to naked eyes in December from the Northern and Southern Hemispheres. It will reach an apparent magnitude of +4 and hence can be seen through unaided eyes and even binoculars or a small telescope. Comet Leonard might reach an apparent magnitude of +1, which means it might become way brighter than predicted. The best day to see comet Leonard with naked eyes is 6 December with it will be just 5 degrees away from Bootes' brightest star, Arcturus. This video explains in detail how to see comet Leonard with naked eyes.
Top astronomical events in December 2021
December 1: Neptune ends retrograde motion
December 3: Conjunction of Moon and Mars
December 4: Total Solar Eclipse
December 6: Comet Leonard
December 7: Venus at greatest brightness
December 8-9: Moon, Jupiter, and Saturn
December 12: Comet Leonard at perigee
December 13: Comet Leonard becomes an evening object
December 14: Geminid meteor shower
December 17: Comet Leonard and Venus
December 19: Full Moon
December 21: The Winter Solstice
December 22: Ursid Meteor Shower
------ Post added on Dec 3, 2021 at 9:17 AM
Top astronomical events in December 2021
December 1: Neptune ends retrograde motion
December 3: Conjunction of Moon and Mars
December 4: Total Solar Eclipse
December 6: Comet Leonard
December 7: Venus at greatest brightness
December 8-9: Moon, Jupiter, and Saturn
December 12: Comet Leonard at perigee
December 13: Comet Leonard becomes an evening object
December 14: Geminid meteor shower
December 17: Comet Leonard and Venus
December 19: Full Moon
December 21: The Winter Solstice
December 22: Ursid Meteor Shower
------ Post added on Dec 3, 2021 at 9:17 AM
Another recent video on the James Webb...
------ Post added on Dec 18, 2021 at 6:25 AM
Potential of SpaceX Starship
------ Post added on Dec 18, 2021 at 6:25 AM
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