Seeing Double

This particular object in the constellation Lepus stands out from the crowd. It’s actually  two separate galaxies whooshing past each other at about 2 million km/h. That’s probably so fast that they won’t merge and form a single galaxy. However, because they’ll pass within about 20,000 light-years of each other, the galaxies will distort one another through the force of gravity, warping each other on a grand scale.

Image Credit: ESA / NASA

A Pair of Galaxies

MRK 1034This pair of galaxies, called MRK 1034, lies in the constellation of Triangulum (The Triangle) in the northern sky. The two similar galaxies, PGC 9074 and PGC 9071, are close enough to one another to be tied together by gravity, but because we are seeing them as they are just beginning to interact gravitationally, there aren’t any large distortions noticeable. Yet. Wait a few hundred million years.

We see both spiral galaxies top down from our point of view. At the bottom PGC 9074 shows a bright bulge and two spiral arms tightly wound around its nucleus, features which classify it as a type Sa galaxy. PGC 9071 isa type Sb galaxy with a fainter bulge and the spiral arms further apart. The spiral arms of both show dark patches of dust mixed with blue clusters of recently-formed stars. Older, cooler stars can be found in the glowing, compact yellowish bulge towards the galactic centers, and each galaxy is surrounded by a much fainter round halo of old stars.

So what would we likely see after waiting a few hundred million years? As these two neighbors attract each other, the process of star formation will be increased, and tidal forces will throw out long tails of stars and gas. Eventually, the interacting galaxies should merge together into a new, larger galaxy.

Image Credit: NASA

Watching Big Brother

NGC 6744This is NGC 6744, one of the galaxies most similar to our Milky Way in the local group of galaxies. From the Earth’s point of view it’s found in the southern sky in the constellation of Pavo (the Peacock) at a distance of about 30 million light-years. This ultraviolet view highlights the vast extent of its spiral arms; NGC 6744 is the Milky Way’s big brother, with a disk stretching 175,000 light-years across. A small, distorted companion galaxy is located nearby, similar to the Large Magellanic Cloud near our galaxy. This companion, called NGC 6744A, can be seen at the upper right as a blob in the main galaxy’s outer arm.

Image Credit: NASA

Mergers and Acquisitions

galactic_mergerSeveral telescopes have teamed up to examine a rare and massive merger of two galaxies that took place when the universe was just 3 billion years old (that was over 10 billion years ago). The galaxies, collectively called HXMM01, were creating a couple of thousand new star a year as they merged. These days, our galaxy, the Milky Way, hatches about two to three a year. The total number of stars in both colliding galaxies averages is around 400 billion.

The Herschel Space Observatory first spotted the collision in images taken with infrared light (the image at left). Follow-up observations from other telescopes showed the extreme degree of star-formation taking place in the merger.

The merging galaxies are circled in the close up view (on the right). The red data from the Smithsonian Astrophysical Observatory’s Submillimeter Array atop Mauna Kea, Hawaii, show dust-enshrouded regions of star formation. The green data, taken by the National Radio Astronomy Observatory’s Very Large Array, near Socorro, N.M., show carbon monoxide gas in the galaxies.

Blue shows visible starlight. The blue blobs outside of the circle are galaxies located closer to us as seen via near-infrared light observations are from the Hubble Space Telescope and the W.M. Keck Observatory atop Mauna Kea, Hawaii.

Image credit: ESA/NASA/JPL-Caltech/UC Irvine/STScI/Keck/NRAO/SAO

Galactic Old Timers

hs-2012-48a-670Astronomers have uncovered seven primitive galaxies that formed more than 13 billion years ago, when the universe was less than 4 percent of its present age. The deepest images to date from the Hubble Space Telescope show the first statistically significant sample that gives us an idea of how abundant galaxies were in the era when they were first forming.

The newly discovered galaxies are seen as they looked 380 to 600 million years after the big bang. Astronomers study the distant universe in near-infrared light because the expansion of space stretches ultraviolet and visible light from galaxies into infrared wavelengths, a phenomenon called redshift. The farther away a galaxy, the greater its redshift. One of these galaxies may be a distance record breaker, observed 380 million years after the big bang, corresponding to a redshift of 11.9.

The hot stars in the first galaxies provided radiation to warm the cold hydrogen that formed soon after the big bang. That made the universe transparent to light, allowing us to look far back into time. The galaxies in the new study are seen in this early epoch. Data shows that this was a gradual process, occurring over several hundred million years, with galaxies slowly building up their stars and chemical elements.

Image Credit: NASA

When Galaxies Collide

If we’re talking a pair of old Fords, the result is scrap metal. If we mean a couple of large groups of stars, the result is more spectacular. When one galaxy tries to hitch a ride with another, as with this pair in the constellation Corvus (The Crow), the stars in them usually don’t hit each other. Galaxies are mostly empty space, and stars only take up only a small amount of that space. During the slow, hundred million year collision, one galaxy can rip the other apart gravitationally, and the dust and gas common to both galaxies does collide. In clash of titans shown in the Hubble image above, dark dust pillars result from massive molecular clouds are being compressed during the galactic encounter, further resulting in the rapid birth of millions of stars.

Image Credit: NASA