Astronomy

Another New Spur In Our Galaxy?

2021-08-18T18:46:15Z

Posted by: dewline

Looks like a "Serpens-Sagittarius Spur" newly recognized as such based on Phil Plait's commentary today here:

https://www.syfy.com/syfywire/newly-discovered-structure-in-the-milky-way

Opinions?

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GAIA EDR3 By The Numbers

2020-12-05T02:25:22Z

Posted by: dewline

Admittedly, this is from the official ESA Flickr account, so...they've got something to promote, and I think it's worth promoting.

I want to see hardcopy "looking down along the Z-axis" maps, to be honest.

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Software: Gaia Sky

2020-05-03T14:29:42Z

Posted by: dewline

Is anyone here using this software?

https://zah.uni-heidelberg.de/institutes/ari/gaia/outreach/gaiasky/

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Mars Occultation

2020-02-27T14:31:25Z

Posted by: dewline

Sourced from coudal_feed:

https://www.instagram.com/p/B8uNIVDJjif/

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TWITTER: Betelgeuse Status

2020-02-15T14:43:40Z

Posted by: dewline

For people wanting to keep an eye on that particular star via Twitter:

https://twitter.com/betelbot

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GAIA-Related Question

2019-10-07T01:53:54Z

Posted by: dewline

Anyone else keeping this bookmark on their browser(s)?

https://twitter.com/hashtag/gaiadr2?f=tweets&vertical=default&src=hash

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First direct image of a black hole

2019-04-10T17:21:35Z

Posted by: seasonoftowers

The image is all over the 'net, but thought I'd also link to the papers, and the soon-to-happen Reddit AMA

You know shit's good when you need to correct for the drift of the polar ice cap so that the components of your radio telescope network (one of which is located in Antarctica) stay in sync and continue acting like a single giant radio telescope the size of the goddamn planet.

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Link: Large Exomoon Likely Orbits a Faraway World

2019-03-28T21:16:58Z

Posted by: steorra

It seems like we've found a moon orbiting an extrasolar planet. The moon is approximately Neptune-sized and the planet is approximately Jupiter-sized (which could cover a large range of masses, because once things get about as massive as Saturn they mostly get denser rather than bigger when you add more mass, until they hit star size.)

Large Exomoon Likely Orbits a Faraway World

Teachey and Kipping found that two aspects of the transit data from Hubble were consistent with their exomoon hypothesis. First, the planet transited the star 1.25 hours earlier than expected on the basis of the orbital period measured by Kepler. “That is indicative of something gravitationally tugging on the planet” during this particular transit, Kipping explained.
[...]
Second, the Hubble observations of the host star’s brightness showed two dips in brightness instead of just the one from the planet. “The location, shape, and depth of this event appear consistent with a Neptune-sized moon [also] transiting in front of the star,” Kipping said. The team also saw this secondary dip in the star’s light in some of the Kepler transits.

I wonder if they'll be able to infer enough information about the exomoon's orbit to work out anything about the masses of the planet and moon. I'm guessing likely not, but it is impressive how much information astronomers are able to squeeze out of seemingly tiny amounts of data, so maybe.

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Link: Charon’s icy surface erupted from an underground ocean

2019-03-09T18:01:36Z

Posted by: steorra

Charon’s icy surface erupted from an underground ocean

So the more plausible explanation is that the underground ocean escaped overground, allowing an icy slush to flood out over Vulcan Planitia. This could have occurred through cryovolcanism, the ice version of normal volcanoes. But these weren’t violent, Krakatoa-style eruptions. Instead, they would have been a slow creep of material through cracks in Charon’s surface.

A slightly more dramatic version of this slow flood depends not on small cracks, but on large-scale rupturing of Charon’s upper layers. In this scenario, the surface doesn’t just crack, but founders into huge chunks which sink or tilt into the slushy ocean.

This would have probably caused a faster flooding, but the end result looks identical as far as New Horizons’ images can show.

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Link: "Some big moons in the Kuiper belt"

2019-03-02T18:24:32Z

Posted by: steorra

(Cross-posted to my own journal)

There's a neat post by Emily Lakdawalla about "Some big moons in the Kuiper belt" It's a year old, but I just read it recently.

It talks about how Eris's moon Dysnomia and Orcus's moon Vanth are bigger than previously thought. This means that they are also darker in colour than previously thought - a bigger surface must be darker-coloured to produce the same brightness from earth that we see.

This ends up meaning that Eris and Dysnomia are almost opposites in brightness: Eris reflects 99% of the light that falls on it, while Dysnomia reflects around 4%, making it darker than coal!

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Identify-this-world quiz

2019-02-22T08:01:56Z

Posted by: steorra

I happened upon this neat quiz by the amazing Emily Lakdawalla. There are pictures of the surfaces of 18 solid solar system worlds, all to roughly the same scale of 1 km/pixel, and you can try to guess which picture is which world. Some are pretty easy if you've spent much time looking at space imagery, and some are quite difficult.

The answers are here.

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Potentially a bit off-topic

2018-12-08T07:21:00Z

Posted by: seasonoftowers

Hello, and hope I'm not too off-topic with stargazing gear discussion, but does anyone have any recommendation for a good 15mm 1.25' aperture telescope eyepiece? Looking for usability with glasses, good performance on a f5 telescope and non-Televue/Pentax prices, preferably

Thanks!

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Changes in Earth's lights at night

2017-04-28T20:39:32Z

Posted by: steorra

Lights On | Lights Out

This piece has some nice graphics and discussion of changes in nocturnal satellite images of Earth between 2012 and 2016. There's a slider where you can compare two maps directly, as well as processed images showing increased lighting in blue and decreased lighting in pink.

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Please allow me to introduce myself

2017-04-07T18:13:35Z

Posted by: thewayne

I'm not a man of wealth and fame. My main interest in astronomy is the fact that I'm married to an astronomer: I do enjoy astronomy, I'm just not a scientist. My wife operates the 3.5 meter telescope at Apache Point Observatory, and also runs the APOLLO lunar laser ranging experiment (got some good results last night in marginal weather). And she is famous, at least in some circles: she was the final segment of the Mythbusters episode in 2008 debunking the 'man has never been to the moon' garbage, along with several other TV programs.

We're hoping to head up to Oregon to see the solar eclipse this year, we'll see what happens. I had hoped to buy a solar telescope to take some photos of it, but I've been unemployed for about 10 months now, so that's not too likely. Maybe I can kitbash something together.

If you like big telescope pictures, or are interested in a video that I made about the lunar laser ranging conducted at APO, I have a photography web site. I need to upload a couple of photos of the Clark telescope at Lowell Observatory that I shot in February, unfortunately the Pluto Discovery Telescope and dome are closed for a refurb. I'm hoping next year to be able to get some fresh photos of them.

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Imaging Black Holes

2017-04-07T18:04:54Z

Posted by: thewayne

I saw this on Slashdot this morning, I wonder how long it will take to integrate the data and start producing results.

Earth-Sized Telescope Set To Snap First Picture of a Black Hole (newscientist.com) 52

Posted by msmash on Friday April 07, 2017 @08:40AM from the big-picture dept.

An anonymous reader writes from a New Scientist report: This week, we will have our first chance to take a picture of the supermassive black hole at the centre of our galaxy. The image could teach us how black holes work and even how the largest and smallest forces governing the universe fit together. The Event Horizon Telescope is switching on. It consists of eight radio observatories around the world, including telescopes in Spain, the US and Antarctica. And for just four or five nights between 5 and 14 April, if the weather is clear at all of the observatories, they will all turn on at once. Each telescope will point at Sagittarius A, the supermassive black hole at the centre of the Milky Way, and measure every radio wave coming from its direction. Linking together observatories spread across such a huge area and combining their observations to filter out extra light will effectively create a powerful "virtual telescope" almost the size of Earth. These telescopes will together capture sharper and more detailed data than we've ever had from Sagittarius A, which we still know very little about, as well as the larger black hole at the centre of nearby galaxy M87. With the telescopes generating a total of 2 petabytes of data per night -- enough to store the full genomes of some 2 billion people -- astronomers hope to take the first image of the event horizon around a black hole, and the bright matter hurtling around it.

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Venus-type planets and Super-Earths with Water Vapour

2017-04-07T02:35:32Z

Posted by: dewline

Subjects of interest:

1. Kepler 1649b
2. GJ 1132b

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Alpha Centauri B's planet - maybe not after all

2013-05-28T14:24:23Z

Posted by: steorra

Back in October I wrote about Alpha Centauri B's first known planet, and associated discoveries about Alpha Centauri B. I talked about all the work that went into filtering out noise (redshift and blueshift from other sources) to find the signal from the planet.

Well, that was a very complex process, and some work since then has followed up and suggests that it may have gone awry, and there may not be a planet after all. Here's an article with more info:
No Planet of Alpha Centauri B?

It doesn't conclude for sure that there is no planet, but it casts doubt on the idea that there is; ultimately, more data will be needed to resolve the issue, and we might have to wait a while for that data, since the orbits of Alpha Centauri A and B are bringing them closer together in the sky from our point of view, which will make it impossible to study just the light of Alpha Centauri B without some light from Alpha Centauri A getting mixed in.

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Cassini spots mini Nile River on Saturn moon

2012-12-12T20:33:19Z

Posted by: steorra

Cassini spots mini Nile River on Saturn moon

Cassini's radar imaging of Titan has spotted evidence for a 400 km long river on Titan, with its mouth in a lake. Lakes and rivers on Titan are made of liquid methane/ethane, not water, which is frozen rock-like at Titan's temperatures. The riverbed-shaped structure is apparently full of liquid, not a dry empty riverbed, because it appears dark to the radar, indicating that it has a smooth surface.

I'm not sure why it's compared specifically to the Nile river.

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Alpha Centauri B's first known planet, and associated discoveries about Alpha Centauri B

2012-10-17T19:13:24Z

Posted by: steorra

A piece of big astronomy news came out yesterday: An earth-sized planet has been discovered orbiting Alpha Centauri B, a relatively sun-like star (a bit smaller and fainter than the Sun) in the nearest star system to the Sun. The planet is not particularly earth-like, though, since it orbits the star in only about 3.2 days, and thus would be extremely hot.

I started to write a long entry talking about Alpha Centauri system the system and the discovery, but I think instead I'm going to link a few articles - there are many more that could easily be found - and talk a bit about some things I noticed in reading the original paper.

( News stories )

( Links to the original paper )

I gave the paper a quick reading, and while some of it was too technical for me to understand, I was able to follow the basics of it. And I was once again amazed by the amounts of information that astronomers are able to squeeze out of apparently tiny amounts of data - in this case, the spectrum of a star observed repeatedly over time.

( Details )

Here's an article that talks about some of the noise sources in non-academic terms.

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Seems that the meteor on September 21st didn't go around the world after all

2012-10-10T14:15:05Z

Posted by: steorra

I posted about a week ago about a double meteor sighting on September 21st where calculations seemed to show that they were in fact the same object which had once skimmed through Earth's atmosphere, then out again, then gone around the earth and re-entered the atmosphere.

Other/newer calculations are showing that that seems not to have happened after all. Instead, it seems like it really was just two independent fireballs.

I'm not sure the question is 100% resolved yet. Science takes time.

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Leaving the solar system

2012-10-07T17:39:40Z

Posted by: steorra

I keep seeing articles about how Voyager 1 is leaving the solar system, or about to leave the solar system, or may just have left the solar system. An example is a science blog post titled More evidence that Voyager has exited the solar system.

These articles are talking about a real and interesting phenomenon, but I find the description of it as "leaving the solar system" misleading.

What they are primarily talking about is Voyager leaving the sun's heliosphere, the region of space affected by the charged particles of thesolar wind. Outside the heliosphere is the interstellar medium. Passing the heliopause between the heliosphere and the interstellar medium is crossing a significant boundary between a kind of space that is heavily influenced by the sun and one that isn't. So it is a significant event that Voyager 1 is passing this boundary, and in the process giving us evidence about the location of the boundary and what conditions are like at it and on either side of it.

Voyager 1 is currently about 122 astronomical units (au) from the sun, or 122 times earth's distance from the sun. That's a long ways away, but there are still many objects in the solar system whose orbits take them out that far; not only many comets, but also Sedna, which goes as far as 940 au from the sun at its most distant. And the Oort cloud, a hypothesized reservoir of comets that have never yet come close to the sun, is hypothesized to be between around 5000 and 50,000 au from the sun. All these orbits are still orbiting the sun, and thus still part of the solar system. It seems misleading to me to say that Voyager 1 is leaving the solar system when it's still well within the orbits of many things orbiting the sun.

But crossing the heliopause is still neat and noteworthy.

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"Amazing Meteor Boomerangs Around Earth"

2012-10-02T22:49:29Z

Posted by: steorra

Amazing Meteor Boomerangs Around Earth

In the evening of September 21st, a bright fireball meteor was seen in western Europe and the British Isles.

A few hours later, a bright fireball was seen in eastern North America.

At first, this seemed like it had to be a coincidence - two independent bright fireballs that happened oddly to occur on the same day. It couldn't just be that the fireball had crossed the Atlantic - for one thing, that would have taken much less time than a few hours.

It turns out, though, that calculations of the meteor's path indicate that they were actually the same object; it had just gone all the way around the earth in between. It had skimmed shallowly through the edge of the atmosphere making a fireball as it passed over Europe and the British Isles, and then out again on the other side. Its passage through the atmosphere slowed it down enough to put it into an elliptical orbit around the earth. It went around the earth once-and-a-bit, and came back down to atmospheric height over North America, where it entered the atmosphere again as another fireball, never to exit again.

(One simplification I made in the above story is that the meteor actually fragmented during its first pass through the atmosphere; the fireball seen over North America would have been probably just the biggest fragment of it.)

EDIT: Newer calculations show that this story is probably not accurate after all.

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Comet ISON (C/2012 S1)

2012-09-26T03:30:50Z

Posted by: steorra

There's a recently-discovered comet that could put on a spectacular show in late 2013 - at its brightest (when it's hard to see because it's really close to the sun), it could be brighter than the full moon, and visible in daytime.

However, predicting comet brightness is notoriously difficult, and this one could end up being nothing spectacular; Comet Kohoutek (C/1973 E1) in 1973 is a famous case of something that was predicted to be brilliant but didn't live up to prediction.

Bill Gray, whom Emily Lakdawalla consulted on the matter, estimates that it has a 30% chance of being awesome, and a 60% chance of being a dud. (And what about that other 10%? He doesn't say.)

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5th moon of Pluto

2012-07-15T18:53:48Z

Posted by: steorra

A fifth moon of Pluto has been discovered.

Here is a Hubble Space Telescope press release.

And here is an article from Sky and Telescope.

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Evidence for subsurface oceans on Titan

2012-06-29T01:22:10Z

Posted by: steorra

Cassini has found evidence that Titan has liquid water beneath its surface. Saturn causes tidal distortions in Titan; if Titan were solid all the way through, we'd expect to see relatively small tidal distortions, but Cassini has instead found much larger ones, which suggests that part of its interior is liquid and thus more easily distorted.

Here are two articles on the topic, one from NASA and one from ESA.

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