Andromeda and The Milky Way – Collision in 3, 2, 1…

…billion years.

Looking From Our Milky Way toward the Andromeda Galaxy
Image Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas, and A. Mellinger

With a small telescope, you can see the Andromeda Galaxy as a thin disk near the top of the image, and just off to the left side of the Milky Way, which stretches from top to bottom.

Thanks to the four refurbishing missions by the Space Shuttle, NASA has been able to gather extended data on the motion of the Andromeda Galaxy and the Milky Way. Based in this data, we now know how and when the two galaxies will collide.

Below, Andromeda and the Milky Way move closer, pass each other in a burst of star formation due to the tidal disruption, and eventually coalesce into an Elliptical Galaxy.

1.37 Billion
The Andromeda Galaxy Is Clearly Visible 1.37 Billion Years in the Future

2.06 Billion
2.06 Billion Years in the Future, Andromeda Dominates the Night Sky

3.49 Billion
3.49 Billion Years in the Future, Andromeda Dominates the Night Sky

3.78 Billion
Tidal Disruption Begins to Distort the Galaxies at 3.78 Billion Years

3.86 Billion
With Tidal Disruption Comes a Massive Outburst of Star Formation

3.98 Billion
Massive Distortion of Both Galaxies Occurs as They Pass Around 3.98 Billion Years

4.60 Billion
Star Formation has Begun on a Massive Scale 4.60 Billion Years

5.83 Billion
After Another Billion Years, Massive Stars Have Gone Nova

7.00 Billion
The Two Central Regions of the Galaxies Have Coalesced into an Elliptical Galaxy

Kepler Mission Extension

2321 Planets
2321 Potential Planet Discoveries by Kepler Space Observatory
Image Credit: NASA Ames / Wendy Stenzel

The Kepler mission, discoverer of 2,321 possible planets around stars in the region near Cygnus (star map) in our Milky Way galaxy, has been extended through 2016 based on a recommendation from the Agency’s Senior Review (pdf document)

Also, Kepler has discovered 2,165 eclipsing binary stars. Binary stars for when most of the mass of the solar system ring condenses or accretes into a single body with enough mass to ignite a fusion reaction, rather than several Jupiter and Neptune sized objects with some rocky planets.

The Kepler Mission has a Quick Guide, which explains the workings of the observatory.

Kepler Systems
Multi-Planet Systems Discovered by the Kepler Space Observatory (not to scale)
Image Credit: NASA Ames / Dan Fabrycky, UC Santa Cruz

The above diagram illustrates the multi-planet systems found by Kepler. The maps represent the relative sizes of the systems and the relative size of the planets in each system. They are not scaled in relation to the central star.


Image Credit: NASA / JPL-Caltech / UCLA

The Wide-field Infrared Survey Explorer (WISE) mission has just released the image above showing Everything in the infrared spectrum. Approximately 560 million stars, galaxies, gas clouds, near-Earth asteroids and other objects are included in the image.

Visible in the image:

  • Large and Small Magellanic clouds to the bottom right
  • The Andromeda galaxy forms a small blue streak to the lower left
  • The Rho Ophiuchi cloud complex, only 130 light years away, above the galactic center

More Planets than Stars – But Axial Tilt is the Key to Life

There is an average of more than one planet per star in the Milky Way
Image Credit: NASA / ESA / ESO

With the forthcoming publication in the journal Nature on 12 January, it is estimated that there are more than 100 billion planets in our Milky Way galaxy. That means more than one planet per star, and results show that there are more rocky small Earth-like planets than giant Jupiter-size gas planets.

Most recent discoveries have come from the Kepler Observatory using transit observations. Some of the earliest confirmation of gas giants came from radial velocity Doppler observations.

The conclusions in the Nature article are based on micro-lensing studies.

Recent results from the Kepler Observatory have shown the existence of three small, rocky planets around the star KOI-961, a red dwarf. These three planets, named KOI-961.01, KOI-961.02 and KOI-961.03, are 0.78, 0.73 and 0.57 times the radius of Earth. The smallest is about the size of Mars (see below). Follow-up observations were made by the Palomar Observatory, near San Diego, and the Keck Observatory atop Mauna Kea in Hawaii.

Relative size of the three rocky planets around KOI-961
Image Credit: NASA / JPL-Caltech

Since it is now clear that rocky planets exist around millions, if not billions, of stars, the question arises as to whether there is life on them, and whether it may resemble life on Earth.

Whether a planet exists in the “Goldilocks” region around a star depends on many factors. Three factors include the type of star, how far away from the star the planet resides and the atmospheric pressure of the planet. A red dwarf, such as Gliese 581, means the planet has to be closer than the Earth to our Sun. A white hot star means the planet has to be farther away. And if the atmosphere is low, like Mars, or to high, like Venus, liquid water is not likely.

A fourth factor is axial tilt. If a planet has no axial tilt (the spin axis is perpendicular to the plane of its orbit around the star) then the polar regions freeze and the equatorial regions bake. There is little exchange between these regions due to atmospheric circulation. Axial tilt, such as the Earth has, allows distribution of heat between the equator and the poles.

Even if a planet has axial tilt, a recent study shows that interaction at a close distance (within the “Goldilocks” region) with red dwarf will eliminate axial tilt in less than 100 million years. Bacteria on Earth required 1,000 million years to evolve. Theoretically, a planet with no axial tilt could possess bands between the equator and the poles where liquid water would exist. But, it is quite possible the atmosphere would collapse, with gases being driven off into space at the very hot equator, and freezing solid on the ground at the poles. Such a possibility faces the planets around KOI 961.

Systems with stars like our Sun present better possibilities. The “Goldilocks” conditions exist much farther out, and axial tilt is eliminated much more slowly, as our Earth is witness. Systems such as Kepler-22b are good candidates.

The conclusion drawn from these studies is that systems similar to our Solar System present the best opportunities for life.

Black Hole in the Milky Way Galaxy Set to Devour Gas Cloud

Video Credit: ESO / MPE / M. Schartmann / L. Calçada

A cloud of gas is being pulled closer to the supermassive black hole lurking in the center of our galaxy, 27,000 light-years away. This unprecedented discovery is being monitored by an international team of scientists using the European Southern Observatory’s Very Large Telescope (VLT). The cool cloud, composed mainly of hydrogen and helium, with a mass three-times that of Earth, has been picking up speed, and by 2013, astronomers will hopefully see some fireworks. By then, the first wisps of gas should be sucked into the black hole’s event horizon causing the black hole to flare brightly.

Lyman Alpha Blob

Alpha Lyman Blob by the European Southern Observatory
Image Credit: ESO / M. Hayes

The European Southern Observatory‘s Very Large Telescope has returned images and data from a vast cloud of glowing gas at the edge of the observable universe. The paper appears in Nature: “Central Powering of the Largest Lyman-alpha Nebula is Revealed by Polarized Radiation”. The object is a “Lyman-alpha-blob” and has entire galaxies embedded in it.

The Object in the paper is known as LAB-1 and was discovered in 2000. It has a diameter of 300,000 light years (our Milky Way is 100,000 light years across). LAB-1 has several primordial galaxies inside, including one with an active core (quasar).

There have been two competing theories about the light emitted by these distant (11-12 billion light years) objects. One idea is that the collapsing gas clouds making up a blob creates the energy that is radiated. A second theory is that the blob is large enough to contain one or more galaxies, which provide the energy needed to shine so brightly. The paper provides evidence for this latter theory.