Ancient Galaxies Fed On Gas, Not Collisions

The Sombrero Galaxy. Credit: ESO/P. Barthe

[/caption]The traditional picture of galaxy growth is not pretty. In fact, it’s a kind of cosmic cannibalism: two galaxies are caught in ominous tango, eventually melding together in a fiery collision, thus spurring on an intense but short-lived bout of star formation. Now, new research suggests that most galaxies in the early Universe increased their stellar populations in a considerably less violent way, simply by burning through their own gas over long periods of time.

The research was conducted by a group of astronomers at NASA’s Spitzer Science Center in Pasadena, California. The team used the Spitzer Space Telescope to peer at 70 distant galaxies that flourished when the Universe was only 1-2 billion years old. The spectra of 70% of these galaxies showed an abundance of H alpha, an excited form of hydrogen gas that is prevalent in busy star-forming regions. Today, only one out of every thousand galaxies carries such an abundance of H alpha; in fact, the team estimates that star formation in the early Universe outpaced that of today by a factor of 100!

This split view shows how a normal spiral galaxy around our local universe (left) might have looked back in the distant universe, when astronomers think galaxies would have been filled with larger populations of hot, bright stars (right). Image credit: NASA/JPL-Caltech/STScI

Not only did these early galaxies crank out stars much faster than their modern-day counterparts, but they created much larger stars as well. By grazing on their own stores of gas, galaxies from this epoch routinely formed stars up to 100 solar masses in size.

These impressive bouts of star formation occurred over the course of hundreds of millions of years. The extremely long time scales involved suggest that while they probably played a minor role, galaxy mergers were not the main precursor to star formation in the Universe’s younger years. “This type of galactic cannibalism was rare,” said Ranga-Ram Chary, a member of the team. “Instead, we are seeing evidence for a mechanism of galaxy growth in which a typical galaxy fed itself through a steady stream of gas, making stars at a much faster rate than previously thought.” Even on cosmic scales, it would seem that slow and steady really does win the race.

Source: JPL

Most Distant Quasar Opens Window Into Early Universe

Quasar
Quasar

[/caption]Astronomers have uncovered yet another clue in their quest to understand the Universe’s early life: the most distant quasar ever observed. At a redshift of 7.1, it is a relic from when the cosmos was just 770 million years old – just 5% of its age today.

Quasars are extremely old, outrageously luminous balls of radiation that were prevalent in the early Universe. Each is thought to have been fueled at its core by an incredibly powerful supermassive black hole. The most recent discovery (which carries the romantic name ULAS J1120+0641) is noteworthy for a couple of reasons. First of all, its supermassive black hole weighs approximately two billion solar masses – an impressive feat of gravity so soon after the Big Bang. It is also incredibly bright, given its great distance. “Objects that lie at such large distance are almost impossible to find in visible-light surveys because their light is stretched by the expansion of the universe,” said Dr. Simon Dye of the University of Nottingham, a member of the team that discovered the object. “This means that by the time their light gets to Earth, most of it ends up in the infrared part of the electromagnetic spectrum.” Due to these effects, only about 100 visible quasars exist in the sky at redshifts higher than 7.

Up until recently, the most distant quasar observed was at a redshift of 6.4; but thanks to this discovery, astronomers can probe 100 million years further into the history of the Universe than ever before. Careful study of ULAS J1120+0641 and its properties will enable scientists to learn more about galaxy formation and supermassive black hole growth in early epochs. The research was published in the June 30 issue of Nature.

For further reading, see related paper by Chris Willot, Monster in the Early Universe

Source: EurekAlert

Astronomy Cast Ep. 224: Orion

Orion Nebula. Image credit: Hubble

Most people know how to find two constellations: the Big Dipper, and Orion the Hunter. You can teach a small child to find Orion, and at the right time of year, they’ll find it in seconds. There’s so much going on in this spectacular constellation, from the star formation in the Orion Nebula to mighty red supergiant Betelgeuse, ready to explode. Let’s learn about the history and science of the constellation Orion.

Click here to download the episode.

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Orion shownotes and transcript.

Noctilucent Clouds and A Bright Northern Star

Noctilucent Cloud display with the bright star Capella over West Berkshire UK Credit: Adrian West

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Noctilucent Clouds are finally here! Well, at least they were for me at about 3:00am on the 29th of June.

I have heard that there have been some sightings, but for me, this mornings display heralds the new NLC season – a month later than usual?

Conditions were amazingly warm, and the night was still and magical as I looked northwards from my home in West Berkshire UK. I couldn’t help but notice a burning bright star almost due North and quite low, Capella in the constellation of Auriga! This is when I spotted the first faint wisps of noctilucent cloud.

Capella isn’t always in the North, but it is this time of year and it usually makes a guest appearance during morning noctilucent cloud displays.

Noctilucent clouds are very rare and tenuous clouds on the edge of space and occur at altitudes of around 76 to 85 kilometers (47 to 53 miles).

They are only seen when conditions are just right (still not fully understood) after sunset or before sunrise. They are illuminated by the sun, which is still way below the horizon from the observers location. Due to their very delicate nature, noctilucent clouds can only be seen at these times. More info on what NLC’s are, can be found here

Will you see any NLC’s?

Noctilucent clouds over Saimaa. Credit: Wikipedia

The longest day – Summer Solstice 21st June 2011

Solstice Sunset Credit:Adrian West

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June 21st, 2011 is Summer Solstice – the longest day of the year.

This is the time when the Sun is at its highest or most northerly point in the sky in the Northern Hemisphere and when we receive the most hours of daylight. If you live in the Southern Hemisphere it is the reverse, so you will be having “Winter Solstice.”

Also known as “Midsummer” the Summer Solstice gets its name from the Latin for sol (sun) and sistere (to stand still). The Sun reaches its most Northerly point and momentarily stands still before starting its journey South in the sky again until it reaches its most Southerly point “Winter Solstice”, before repeating the cycle. This is basically how we get our seasons.

It’s not actually the Sun that moves North or South over the seasons although it may appear so. It’s the Earths axial tilt that causes the Sun to change position in the sky as the Earth orbits the Sun throughout the year.

Why Are There Seasons
The angle of the Sun and the Earth's seasons. Image credit: NASA

Summer Solstice/ Midsummer is steeped in ancient folklore especially in Northern Europe with the most famous place directly related to it being Stonehenge, where the sun has been worshiped for thousands of years.

Stonehenge Credit: bistrochic.net

The Sun reaches its most Northerly point in the sky at 17:16 UTC momentarily and from that point forward starts to make its way South. This means the days will get shorter and shorter until Winter Solstice in December.

A New Way to do Science? Live-Tweeting Observations of Haumea

How the transit of transit of the dwarf planet Haumea by its moon, Namaka would have looked if we could have seen it directly. Credit: Mike Brown

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Back when I first started using Twitter in 2008, I never would have guessed this social media outlet could be used as a conduit for engaging the public about science. But it is facilitating open science in several ways. For example, if you follow Mike Brown on Twitter (@plutokiller) you may have seen a flurry of Tweets from him last weekend as he live-Tweeted his observations of a transit of dwarf planet Haumea by its moon, Namaka. While Brown was at the 4-meter William Herschel telescope on La Palma in the Canary Islands, he explained the process and released multiple plots showing in real time how Haumea dimmed as Namaka passed in front. “This event was particularly live-tweet friendly,” he said on Thursday during a Q&A (again on Twitter) about how he shared his observations live. “We’d know a clear result instantly. Given the chance, I will def[intely] do it again!”

The observations were a success and “spectacular,” Brown said, but it was a little risky in that the transit wasn’t exactly a sure thing, and he might have suddenly — and publicly — had to report that he and his team had incorrectly predicted the transit. But it worked out – after a little hitch – and Brown said that live Tweeting the event gave people a chance to see how science really works in real time. “Normally people would just see the finished paper… the fun part of live tweeting the event was that people could follow as the data came in and hypotheses changed.” (The initial data was much different than expected).

You can see the stream of data as it arrived archived on Brown’s Twitpic page:

“One main reason to watch transit was to measure size & shape of Haumea, since it is so weird,” Brown Tweeted, and said that he’ll be spending the summer analyzing the data he got during the transit to learn more about the football-shaped, spinning dwarf planet.

If you missed the live-Tweeting, you can look back at Brown’s Twitter page), and Nature Blogs has archived the Tweeted Q&A the blog sponsored with Brown on Thursday, June 16, 2011.

It’s science in action.

You can follow Universe Today senior editor Nancy Atkinson on Twitter: @Nancy_A. Follow Universe Today for the latest space and astronomy news on Twitter @universetoday and on Facebook.

Why Can We See Multiple ISS Passes Right Now?

Four ISS passes over the UK last night. Credit: Mark Humpage

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Last night in the UK, US and Europe, we were spoiled with multiple and bright ISS passes. Not just one or two, but up to six passes were able to be viewed throughout the evening in some locations.

This is quite rare as normally we get only one or maybe two visible passes in the evening or morning.

So why are we getting as many as four to six passes per night?

The ISS did receive an orbital boost and its altitude increased by around 20 kilometers. The orbital height of the ISS has an effect on how many visible passes there are at present in the Northern hemisphere. Another reason is because of the time of year.

We are only a week or so away from the Summer Solstice, the time of year when the Northern hemisphere receives the most hours of sunlight. Naturally this means we only have a few hours of darkness and the further North you go, the shorter the nights are and in some locations this time of year, it doesn’t ever get truly dark.

So why does this affect the ISS?

Basically the ISS visible passes have increased due to the station being illuminated much more by the Sun as there are more hours of sunlight right now, but the effect will wear off when we pass through Summer solstice and the nights get longer again.

Take advantage of this rare time and go outside and enjoy the ISS as much as you can in this series of visible passes.

Need to know how and when you can see the ISS? NASA has a Skywatch page where you can find your specific city to look for satellite sighting info.

Spaceweather.com, has a Satellite Tracker Tool. Just put in your zip code (good for the US and Canada) to find out what satellites will be flying over your house.

Heaven’s Above also has a city search, but also you can input your exact latitude and longitude for exact sighting information, helpful if you live out in the country.

Credit: Mark Humpage

Double Spaceship Sighting Alert — and Last Chance to See Endeavour in Orbit

The ISS and space shuttle Endeavour as seen from Lancaster County, Pennsylvania at 4:50am EDT on May 30, 2011. Credit: Beth Katz

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UPDATE: And we have a sighting! Beth Katz from Pennsylvania in the US sent us this image,an 8 second exposure of the ISS and Endeavour taken early this morning. “We observed them seeming even further apart and then closer as they moved away from us,” Beth said via email.

Space shuttle Endeavour will undock from the ISS just before midnight EDT on Sunday night/Monday morning at 11:55 pm EDT (3:55 UTC) and depending where you live, you might have an opportunity to see the two spaceships flying in tandem. People in Europe might have the chance to see the two spaceships right after they separate in the early morning hours, and people in the US/Canada/Mexico might be able to see the two flying close to each other. This is an incredible sight, and will be the last opportunity to see Endeavour in orbit, as she will be retired after she lands and completes the STS-134 mission. The station and shuttle will appear in the night or early morning sky as a closely-spaced pair of bright lights. The ISS is bigger, so will appear as the brighter object trailing the smaller Discovery as they move across the sky.

On Monday night/Tuesday morning, there will be another chance to see the two ships, although they will be widely separated.

To find out if you’ll be able to see the two spaceships in your area, there are a few different sites to check out:


NASA has a Skywatch page where you can find your specific city to look for satellite sighting info.

Spaceweather.com, has a Satellite Tracker Tool. Just put in your zip code (good for the US and Canada) to find out what satellites will be flying over your house.

Heaven’s Above also has a city search, but also you can input your exact latitude and longitude for exact sighting information, helpful if you live out in the country.

Seeing the two spacecraft flying closely in tandem is a very unique and thrilling sight. Good luck! If you manage to capture any images, send them to Nancy.

Coming Soon – Night Shining Noctilucent Clouds

Noctilucent Cloud Display Credit: Adrian West

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Soon you may see an eerie spectacle on clear summer nights if you are located at latitudes between 50° and 70° north and south of the equator: Noctilucent Clouds.

These ghostly apparitions are a delight to see and are quite rare. It is incredibly difficult to predict exactly when they will appear, but we do know they should begin to appear soon.

The season for Noctilucent Clouds (Noctilucent = Latin for “Night Shining”) starts early June and continues into late July. They are seen just after dusk, or before dawn and an apparition can last around an hour.

These mysterious clouds, with their bizarre tenuous wispy shapes reminiscent of ripples in sand or the changing surface of a pool of water, spread like a glowing web across the northern sky. Colours can range from brilliant whites, with tinges of blue, pink and orange.

Formed by tiny ice crystals, they are the highest clouds in the Earth’s atmosphere, located in the mesosphere at altitudes of around 76 to 85 kilometers (47 to 53 miles) almost at the edge of space.

They are normally too faint to be seen, and are visible only when illuminated by sunlight from below the horizon, while the lower layers of the atmosphere are in the Earth’s shadow. Noctilucent clouds are not fully understood and are a recently discovered meteorological phenomenon, only being recorded for about 120 years.

Noctilucent clouds can only form under very restrictive conditions, and their occurrence can be used as a guide to changes in the upper atmosphere. Since their relatively recent classification, the occurrence of noctilucent clouds appears to be increasing in frequency, brightness and extent.

There is evidence that the relatively recent appearance of noctilucent clouds and their gradual increase, may be linked to climate change. Another recent theory is that some of these bright displays come from particulates and water vapour in the atmosphere left over from Space Shuttle launches.

How can you see them? Over the next couple of months look north during dusk and dawn and try and spot this mysterious and elusive phenomenon. They are best seen when the sun is between 6 and 16 degrees below the horizon, and seem to occur more frequently in the Northern hemisphere than the Southern.

Good luck!

Noctilucent clouds over Blair, Nebraska, USA. Credit: Mike Hollingshead