The Astronomy Thread

[xsited1]

Post all things Astronomy whether political or not.

I'll start.

Lowell Observatory in Flagstaff, Arizona, sometimes has open nights for the public. Back in the 90s, I once saw Saturn through their main telescope, the 24" Alvan Clark Refracting Telescope. The view was breathtaking.





Lowell Observatory

 

[American Horse]

Collisions of stars are incredibly unlikely; they occupy such a relatively miniscule volume of space, that even when a pair of galaxies collide, few if any of their constituent stars crash into each other.

Objects in space like planets are much more likely to collide if they orbit each other or orbit a common primary object. In our own solar system Venus doesn’t deserve to smash into anything, since it’s orbit is so perfectly circular.
But Mercury is not so well behaved. Its orbit – already the most lopsided – wildly changes shape. Influences from faraway Jupiter will eventually make its path so elliptical that it will swing out to Venus. Then those two worlds MAY collide.

Here's a fair approximation of what that might look like.
Mercury's diameter is 40 percent that of Venus

 

[Trajan]

Collisions of stars are incredibly unlikely; they occupy such a relatively miniscule volume of space, that even when a pair of galaxies collide, few if any of their constituent stars crash into each other.

Objects in space like planets are much more likely to collide if they orbit each other or orbit a common primary object. In our own solar system Venus doesn’t deserve to smash into anything, since it’s orbit is so perfectly circular.
But Mercury is not so well behaved. Its orbit – already the most lopsided – wildly changes shape. Influences from faraway Jupiter will eventually make its path so elliptical that it will swing out to Venus. Then those two worlds MAY collide.

Here's a fair approximation of what that might look like.
Mercury's diameter is 40 percent that of Venus

interesting..what the timeline on that?

 

[Trajan]

the Egyptians figured out the circumference of the Earth by using a known height,a ruler and digging a hole...anyone ( minus google) know how?

 

[American Horse]

Objects in space like planets are much more likely to collide if they orbit each other or orbit a common primary object. In our own solar system Venus doesn’t deserve to smash into anything, since it’s orbit is so perfectly circular.
But Mercury is not so well behaved. Its orbit – already the most lopsided – wildly changes shape. Influences from faraway Jupiter will eventually make its path so elliptical that it will swing out to Venus. Then those two worlds MAY collide.

interesting..what the timeline on that?

It's indefinite because Mercury's orbital plane wobbles taking it both N & S of the orbital plane of Venus. It could even miss Venus and approach a collision with Earth instead. If that path is followed and there's near-hit versus a direct hit with Earth, it could even be ejected by the slingshot effect from the solar system, that being the remotest likelihood.

Edit: I can see how Earth's diameter can be determined by those tools by taking measurements in two locations a known distance apart if they lay on a north/south line but I don't see the need for digging a hole in the ground unless it be to produce a leveling method for measuring a shadow on a plane.

 

[Mr. H.]

the Egyptians figured out the circumference of the Earth by using a known height,a ruler and digging a hole...anyone ( minus google) know how?

They dug the hole to the center of the earth, measured it and multiplied by 2. The result was then multiplied by pi.

Hey- here's a nifty site: a new astro pic every day.

Astronomy Picture of the Day Archive

 

[xsited1]

During the years from 1758 to 1782 Charles Messier, a French astronomer (1730 - 1817), compiled a list of approximately 100 diffuse objects that were difficult to distinguish from comets through the telescopes of the day. Discovering comets was the way to make a name for yourself in astronomy in the 18th century -- Messier's first aim was to catalog the objects that were often mistaken for comets.

Fortunately for us, the Messier Catalog became well known for a much higher purpose, as a collection of the most beautiful objects in the sky including nebulae, star clusters, and galaxies.

SEDS Messier Database

Here's M42 in the constellation Orion:



Messier

 

[American Horse]

Here's a "free copy" of a Tool - the SimSolar - Solar System Simulator - with a visual of the positions of all the planets, earth/moon on the current date or any date between 2/23/1915 and 2/25/2086

here's a small gif image of what it looks like elliptically;
it can expand to a full overhead computer screen view

 

[asterism]

the Egyptians figured out the circumference of the Earth by using a known height,a ruler and digging a hole...anyone ( minus google) know how?

I thought it was actually two holes (wells) and Eratosthenes new the distance between them.

 

[asterism]

Stellarium, and awesome (and free) program for just about all platforms.

Stellarium

It's a personal planetarium with the ability to see what the sky looks like at any time and location on the planet.

 

[asterism]

A tool to show the positions of Jupiter's moons:

SkyandTelescope.com

(free registration required, use Mailinator - Let Them Eat Spam! for disposable email addresses)

 

[xsited1]

The “Bucket List” for Backyard Stargazers

1. A Supernova
2. The Great Orion Nebula
3. A Bright Comet
4. The Southern Sky
5. A Meteor Storm
6. The Transit of Venus
7. The Green Flash
8. Total Solar Eclipse
9. Sunrise on the Moon
10. The Omega Centauri Star Cluster

The “Bucket List” for Backyard Stargazers | One-Minute Astronomer

I have not seen a supernova, but I did see a nova that was visible to the naked eye when I was very young:

V1500 Cygni or Nova Cygni 1975 was a bright nova occurring in 1975 in the constellation Cygnus.

Nova Cygni 1975 | StarDate Online

 

[Trajan]

Objects in space like planets are much more likely to collide if they orbit each other or orbit a common primary object. In our own solar system Venus doesn’t deserve to smash into anything, since it’s orbit is so perfectly circular.
But Mercury is not so well behaved. Its orbit – already the most lopsided – wildly changes shape. Influences from faraway Jupiter will eventually make its path so elliptical that it will swing out to Venus. Then those two worlds MAY collide.

interesting..what the timeline on that?

It's indefinite because Mercury's orbital plane wobbles taking it both N & S of the orbital plane of Venus. It could even miss Venus and approach a collision with Earth instead. If that path is followed and there's near-hit versus a direct hit with Earth, it could even be ejected by the slingshot effect from the solar system, that being the remotest likelihood.

Edit: I can see how Earth's diameter can be determined by those tools by taking measurements in two locations a known distance apart if they lay on a north/south line but I don't see the need for digging a hole in the ground unless it be to produce a leveling method for measuring a shadow on a plane.

well done you're close. they dug a measured hole, put a measured height at the lip,some think a truncated obelisk ( Mastaba?), the translation I saw surmised that anyway, they marked the time the hole swallowed its shadow, marked time, then marked the moment it swallowed its shadow again. The extrapolation from there is relatively simple.

I'd like to meet the man or woman who thought of the method. Sounds trivial now, but, then? It was genius.

I am something of a pyramidiot ( lol) I have been to I think 18. I happen to agree with the theory that the Great Pyramid was an all in one marker that encompasses or that is encompassed measurements that expressed everything they knew of the heavens the earth and mathematics incl. the closest they could get to the value of pi etc. The Greeks merely rediscovered what they already knew.

 

[Trajan]

Love this story- Galileo discovered the isochronism of the pendulum by watching a lamp swing on a nail in the Tower of Pisa by measuring its oscillation in amplitude by heart beat. He figured out that the time of each swing no matter how high you started the swing or low, the time was exactly the same. unreal.

 

[syrenn]

The “Bucket List” for Backyard Stargazers

1. A Supernova
2. The Great Orion Nebula
3. A Bright Comet
4. The Southern Sky
5. A Meteor Storm
6. The Transit of Venus
7. The Green Flash
8. Total Solar Eclipse
9. Sunrise on the Moon
10. The Omega Centauri Star Cluster

The “Bucket List” for Backyard Stargazers | One-Minute Astronomer

I have not seen a supernova, but I did see a nova that was visible to the naked eye when I was very young:

V1500 Cygni or Nova Cygni 1975 was a bright nova occurring in 1975 in the constellation Cygnus.

Nova Cygni 1975 | StarDate Online

LOL, not sure if the green flash would be under astronomy. Its on my list too.

 

[Mini 14]

Thierry Legault - International Space Station and Discovery before docking

Now this is truly amazing....video of an astronaut space-walking, from an amateur, land-based telescope!

About 12 years ago, my friend and I spent 3 years trying to get good quality video of the shuttle through a 10" LX-200 and NO CCD.

Out of about 200 hours of effort, we wound up with 40 seconds of a blob that *might* look triangular.....at 4am.....in bitter cold.......if you'd been sipping Old Forester and coffee for 8 hours, non-stop.

 

[xsited1]

The “Bucket List” for Backyard Stargazers

1. A Supernova
2. The Great Orion Nebula
3. A Bright Comet
4. The Southern Sky
5. A Meteor Storm
6. The Transit of Venus
7. The Green Flash
8. Total Solar Eclipse
9. Sunrise on the Moon
10. The Omega Centauri Star Cluster

The “Bucket List” for Backyard Stargazers | One-Minute Astronomer

I have not seen a supernova, but I did see a nova that was visible to the naked eye when I was very young:

V1500 Cygni or Nova Cygni 1975 was a bright nova occurring in 1975 in the constellation Cygnus.

Nova Cygni 1975 | StarDate Online

LOL, not sure if the green flash would be under astronomy. Its on my list too.

I have never observed the green flash phenomenon, most likely because I am red-green colorblind, although I have seen the zodiacal light several times. You need to have an unobstructed view of the horizon and I usually don't, but I'm going on a cruise this Summer so I'll be looking for it. Here's more information:

The green flash is an atmospheric refractive phenomenon that occurs shortly after sunset or before sunrise where the top edge of the Sun will momentarily turn green. It is seen rarely by the naked eye, primarily because it requires specific conditions to occur, but also because it requires the observer to know what to look for. Despite the name, there is no "flash"; the event only lasts from a fraction of a second to at the longest, a few seconds.

Mount Wilson Observatory

 

[Old Rocks]

Season 22, Episode 11 | Oregon Field Guide | PBS Video

 

[xsited1]

My youngest told me today that he has trouble making out the constellations. Here's one he's just about got memorized:

View attachment $orion.bmp

The easiest way to find it is to look for the short diagonal line of three stars. That's Orion's belt. Just below them you'll see another, fainter line of stars that forms Orion's sword. One of the objects in Orion's sword isn't a star at all. It's a nebula — a cloud of gas and dust that's like a giant fluorescent bulb. Hot young stars inside the nebula pump energy into its gas, causing the gas to glow. The is the Orion Nebula. Grab a pair of binoculars and check it out.

Orion Nebula - Messier Object 42

Have fun!

 

[waltky]

Big ol' full moon comin'...

Will March 19 'Supermoon' Trigger Natural Disasters?
Thu Mar 10, 11 - On March 19, the moon will swing around Earth more closely than it has in the past 18 years, lighting up the night sky from just 221,567 miles (356,577 kilometers) away. On top of that, it will be full. And one astrologer believes it could inflict massive damage on the planet.

Richard Nolle, a noted astrologer who runs the website astropro.com, has famously termed the upcoming full moon at lunar perigee (the closest approach during its orbit) an "extreme supermoon." When the moon goes super-extreme, Nolle says, chaos will ensue: Huge storms, earthquakes, volcanoes and other natural disasters can be expected to wreak havoc on Earth. (It should be noted that astrology is not a real science, but merely makes connections between astronomical and mystical events.) But do we really need to start stocking survival shelters in preparation for the supermoon?

The question is not actually so crazy. In fact scientists have studied related scenarios for decades. Even under normal conditions, the moon is close enough to Earth to make its weighty presence felt: It causes the ebb and flow of the ocean tides. The moon's gravity can even cause small but measureable ebbs and flows in the continents, called "land tides" or "solid Earth tides," too. The tides are greatest during full and new moons, when the sun and moon are aligned either on the same or opposite sides of the Earth.

According to John Vidale, a seismologist at the University of Washington in Seattle and director of the Pacific Northwest Seismic Network, particularly dramatic land and ocean tides do trigger earthquakes. "Both the moon and sun do stress the Earth a tiny bit, and when we look hard we can see a very small increase in tectonic activity when they're aligned," Vidale told Life's Little Mysteries, a sister site to SPACE.com. At times of full and new moons, "you see a less-than-1-percent increase in earthquake activity, and a slightly higher response in volcanoes."

The effect of tides on seismic activity is greatest in subduction zones such as the Pacific Northwest, where one tectonic plate is sliding under another. William Wilcock, another seismologist at the University of Washington, explained: "When you have a low tide, there's less water, so the pressure on the seafloor is smaller. That pressure is clamping the fault together, so when it's not there, it makes it easier for the fault to slip."

According to Wilcock, earthquake activity in subduction zones at low tides is 10 percent higher than at other times of the day, but he hasn't observed any correlations between earthquake activity and especially low tides at new and full moons. Vidale has observed only a very small correlation. What about during a lunar perigee? Can we expect more earthquakes and volcanic eruptions on March 19, when the full moon will be so close?

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