Monster Galaxies Nibble On Smaller Ones to Get  Bigger

Galaxies grow by eating other galaxies — that’s a given in the cosmos. It’s also true that galaxies spend much of their productive lives making stars from the gas they contain. These two galactic activities began with the first proto-galactic “shreds” that began to combine to grow today’s galaxies. It has continued ever since.

The Milky Way is a good example of this. It formed some 13 billion years ago and grew larger by consuming stars and gas from other, smaller galaxies. It is, in fact, still cannibalizing some dwarf galaxies and may eventually gobble up the Large and Small Magellanic Clouds in a few billion years.

In the future, the Milky Way and the Andromeda Galaxy — currently some 2.5 million light-years apart — will collide. It’s very likely that the  much-more-massive Andromeda will cannibalize the Milky Way. Ultimately the new galaxy that’s formed will undergo a superburst of star formation, using up the gases from the two combined galaxies. Astronomers have seen massive starburst knots at other galaxy collisions, so it’s very likely a feature of most galaxy collisions.

Researchers are now working to pin down some of the complexities of this galaxy-evolution-by-cannibalism mechanism. A team  in Australia is using spectroscopic observations 0f light and radio waves from distant galaxies to find many sites where galaxies are merging, larger ones pigging out on smaller ones. Interestingly, although the galaxies undergo starburst events during the mergers, eventually many of the most massive galaxies created from these collisions eventually stop making stars. The reasons may be related to events occurring within their active central cores (where many galaxies have supermassive black holes that could be sending jets out to space and somehow disrupting the normal course of events).

The group studied many merging galaxies and characterized the shapes they saw. Each of the galaxies in the image at the left from their survey captures a galaxy collision in a snapshot of time. You can see some are about to merge and others have passed by each other, interacted, and are about to go for a second pass. Ultimately each of these mergers will result in a monster galaxy.

The group also created an animation from a computer model showing the interaction of the Milky Way and Andromeda, which will commence in about five billion years. Ultimately, both galaxies will lose their separate identities and become a new, more massive version of the originals.

Andromeda and the Milky Way Collide! from ICRAR on Vimeo. In about five billion years time, nearby massive galaxy Andromeda will merge with our own galaxy, the Milky Way, in an act of galactic cannibalism (technically Andromeda will be eating us, as it’s the bigger of the two galaxies.). There haven’t been any large mergers with our galaxy recently, but we can see the remnants of galaxies that have previously been snacked on by the Milky Way. We’re also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds sometime in the future.
This simulation shows what will happen when the Milky Way and Andromeda get closer together and then collide, and then finally come together once more to merge into an even bigger galaxy.
Simulation Credit: Prof Chris power (ICRAR-UWA), Dr Alex Hobbs (ETH Zurich), Prof Justin Reid (University of Surrey), Dr Dave Cole (University of Central Lancashire) and the Theoretical Astrophysics Group at the University of Leicester.Video Production Credit: Pete Wheeler, ICRAR.

In the far distant figure, many billions of years from now, galaxies in clusters and groups will likely have merged into a few supergiant monster galaxies. This will markedly change the look of the cosmos in ways that astronomers can now only speculate about. Stay tuned!

Here are a few things that caught my eye today from the mailbag.

Red Planet News

This week the MAVEN mission slips into orbit around Mars after a 10-month journey to the Red Planet. MAVEN is a climate science mission designed and led by scientists and students at the University of Colorado and as it settles into orbit it, will start studying the Martian atmosphere for clues to the history of water there. The existence of water both on the surface and in the atmosphere is important when you want to figure out if life ever existed on the planet (or still does). We can see surface characteristics that look like something flowed across the landscapes: river beds, dry lakebeds, the shores of ancient oceans — all these point to the existence of water sometime in the past.

Finding clues to water in Mars’s atmosphere is more challenging, requiring instruments that can measure the amounts of water in the upper and mid-atmosphere levels of the planet, as well as other gases in the thin envelope that surrounds the planet. For example, the amount of an isotope of hydrogen called deuterium can help tell how much water may have escaped from Mars in the past.

In a lucky piece of serendipity, the MAVEN scientists will also get the chance study Comet C/2013 A1 Siding Spring as it passes very near Mars on its first trip through the solar system in . The idea is to use the spacecraft ultraviolet imaging spectrograph to study the tail components and measure their effects on the upper atmosphere of the planet.

MAVEN isn’t the only spacecraft to check out the comet during the Mars flyby.  The Indian space agency’s Mars Orbiter Mission (MOM) will arrive at the planet on September 24th, 2014, for an extended mission. The European Space Agency’s Mars Express spacecraft will also look at the comet and collect data. In addition, if conditions are safe enough to allow, the Mars Reconnaissance Orbiter’s HiRISE imaging system will acquire images, and the Mars Rovers Curiosity and Opportunity could, at the very least, watch for meteors in the sky as cometary tail pieces fall to the surface of Mars. All of the observations by orbiting and surface craft will be subject to last-minute changes if it looks like particles from the comet could pose a large threat. So far, however, mission controllers are relatively optimistic about being able to study a comet from the surface of another world. You can read more about mission preparations for the comet flyby in this Space.com article.

It’s “Back to the Future” for NASA’s Astronauts

The announcement yesterday that NASA had selected Boeing to build an Apollo-similar capsule for its much-vaunted return to spaceflight didn’t take a lot of people by surprise. I would have preferred something more modern-looking and exciting, like the Sierra Nevada Dream Chaser (which at least looks like a sexy, souped-up shuttle). Instead we have a capsule with updated WiFi and Dreamliner-style lighting that can seat 7 and be reused up to 10 times. It really feels like “back to the future” with designs we’ve seen before (like decades ago).  I did see that Sierra Nevada still plans to go to test flight in 2016 with the Dream Chaser, so maybe it will stay a viable alternative.

The good news about NASA’s selection is that we finally can point to a definite date (or as definite as it gets) for return to flight for the U.S. (and not having to depend on Russia for a ride to space). The announcement yesterday pointed toward a 2017 flight certification for the CTS-100.

NASA Continues Climate Change Studies

NASA’s science studies aren’t limited to distant planets and never have been. For many years, the space agency has been studying Earth as a planet, right down to changes in its surface and climate. In particular, NASA is studying how rising global temperatures affect the Arctic. The Arctic Radiation — IceBridge Sea and Ice Experiment (ARISE) is an airborne campaign to collect temperature data. this is particularly important since Arctic warming is happening 2-3 times faster than global warming.  The study was designed to look at the specific relationship between sea ice (and its retreat), and the Arctic climate. Arctic sea ice reflects sunlight away from Earth, moderating warming in the region. When sea ice is lost, more heat from the Sun gets absorbed by the ocean’s surface and that adds to Arctic warming. Loss of sea ice leads to more extensive areas of open water, which allows more moisture to get pumped into the air. That forms clouds, which can either enhance or reduce warming. Understanding the complexities of warming and its effect on the Arctic will help scientists better understand the complete climate system that operates on our planet. Learn more about NASA’s current research in the Arctic in this article released earlier this week.