We’ve talked about gravitational lensing before.  You know what that is; it’s when light is bent in response to the gravitational pull of an object of respectable mass.  Say you’re looking at a very distant light source, like a galaxy.  If there is a massive object between you and the light source (like a massive planet), you will see the light bent around the object — it looks like a distortion in your telescope.

Image shamelessly lifted from NASA/Goddard Space Flight

It’s not a distortion… it’s something that was discussed way back in 1924 (Orest Chwolson) and 1912 (Albert Einstein).  This effect wasn’t scientifically proven until 1979.  It’s scary sometimes to think about how smart these people were, you know?  How great it would be to have Einstein or Galileo in modern times.  Think what they could do with our telescopes today.

Anyway, one very interesting thing about the lensing we’re seeing today is that we see light bending around some massive source of gravity that we can’t see.  It’s not black holes (we’re getting good at pinpointing those), and they don’t think there’s a massive planet there… it’s just light reacting to something we haven’t seen yet.  Wow.  Could it be dark matter, you think?  Something else?

NASA/Goddard Space Flight web site

The distortion effect is called Einstein Rings, and I did a post on them a while back.  You can read it here if you’d like.

Basically, light will move in a fairly straight path away from it’s source unless it’s acted upon, either by a source of gravity, warps in the fabric of space-time, or something else.  You know light consists of tiny, discrete packages of photons; it exists as a wave-particle duality that can be influenced and acted upon.  Gravitational lensing is when you see light being influenced.  Isn’t that cool?  That’s particle physics, and I know you guys love your physics!

Studies from the lensing in the Hubble ST images has even given scientists a rough idea of the location of “something else” in the visible star field.  Here’s what the 3D image of it looks like:

NASA/ESA/Richard Massey

This is believed to be the location of dark matter.  Of course, nobody can prove that’s what it is yet, but it’s not anything else we’ve seen so far.  Mostly because nothing else except gravitational lensing can “see” it.  Something’s there, and it has mass.

The field is still young, and there’s no telling what we’ll find with it in the future, or in what direction the field will take us.  It’s wide open; waiting for you to fill in the blanks.

In the meanwhile, we get this:

Hubble star field showing lensing, NASA/ESA/ACS, Racah, UCO/Lick Observatory

Most people aren’t aware that between 1961 and 1984, the USSR sent a series of probes to Venus.  All together, ten probes were landed on the surface of Venus, and thirteen were able to return atmospheric data from the planet.

“Venera” is the Russian word for “Venus”, it looks kinda like this in Cyrillic:  Behepa.

Believed location of the Venera landers, archival image

The series was very successful, becoming the first man-made device to enter the atmosphere of another planet (Venera 4), to soft-land on another planet (Venera 7), to return images from another planet surface (Venera 9), and to perform radar mapping of Venus (Venera 15).  Of course, during the time period this occurred, the US and the USSR were fussy with each other, so this amazing accomplishment didn’t receive a lot of air time in the West.

Venera 7 lander capsule, NASA archival image

The probes started out designed to land on a planet much like Earth, but when the atmosphere of Venus was discovered to be so much heavier and more hostile than that of Earth, the hull of the probes was strengthened to survive entry and landing.  We got the first images from the surface of Venus from the Venera probes:

Venera 9 panorama of Venusian surface (1975), archival image

The Venera orbiters mapped much of the surface of Venus, while the landers returned information of surface conditions, including some soil samples.  Venera 12 possibly even recorded lighting on Venus.

An interesting aside is that one of the Venera series that didn’t make it out of Earth’s orbit, becoming renamed “Kosmos 96″, is believed to have crash-landed near Kecksburg, Pennsylvania.  It then became tangled up in what was known as the “Kecksburg Incident” among UFO enthusiasts.

All in all, the Venera series is a wonderful chapter in space exploration… one that didn’t receive near the attention it deserved.  Do you remember Venera?

Looking quite a bit like the captured asteroids they probably are, the Martian moons were predicted by the astronomer Johannes Kepler (1571-1630), and written into the plot of Gulliver’s Travels in 1726.

The tiny Martian moons Phobos and Deimos were discovered by Asaph Hall in August, 1877.  Deimos on the 12th, Phobos on the 18th.  Hall was specifically looking for moons around Mars when he found them.  The names come from the Iliad; Phobus and Deimus were the children of Ares, the Greek god of war (“Mars” is the Roman name for the same entity).

NASA/JPL Phobos and Deimos

Thought to be ancient captures, Phobos will eventually break apart and crash into Mars while Deimos will be pushed away from Mars, eventually drifting free.

NASA/ESA JPL Mars, Phobos, Deimos to scale

Phobos, the larger of the two moons, is also the closest moon to its primary than any other moon in the solar system.  It orbits so fast, so close to the planet that from the surface of Mars Phobos will rise in the West and set in the East.  Phobos is heavily cratered; the largest being the Stickney Crater, which looks to have almost disrupted the tiny moon.  The surface of Phobos is also grooved, thought to have formed as the moon passes through planetary ejecta from impacts on Mars.  Once thought to be hollow, Phobos is now known to be extremely porous.

Deimos, the personification of terror, is the smaller, more distant moon.  It is about 12.6 km is diameter, and shows the same weathered surface as Phobos.  Not as much is known about this little moon.  Even from the surface of Mars, Deimos appears to be a very bright star.

In astronomy, a Trojan is an asteroid or moon that shares an orbit with a larger asteroid or moon, but does not collide with it.  The Trojan orbits within one of the Lagrangian points of stability ahead or behind the main body.

Usually the asteroids which accompany Jupiter around its orbit come to mind when you mention the Trojans.  The Jupiter asteroids were the first discovered, and are believed to be almost as numerous as those in the asteroid belt.  Since the Jupiter Trojans were discovered, scientist have found “Trojans” in the orbits of Mars, Neptune, and Saturn.

Discovered in Jupiter’s orbit in 1906 (588 Achilles was the first one), there have been 4,076 Jupiter Trojans found so far.  There are believed to be over a million Jupiter Trojans larger than 1 km in diameter.  As in the main asteroid belt, the Trojans form asteroid “families”.  Currently, most scientist believe the Trojans are “captured” Kuiper Belt Objects.  Sometimes the “capture” appears to imperfect.  The comet Shoemaker-Levy 9 is believed to have been one such imperfect capture.

Currently there are only four known Mars Trojans, and seven around Neptune.  There may be many more Trojans than those recorded so far; we’re just not in a position to see them yet.  Perhaps when New Horizons passes Neptune…

Martian Trojans, image by Andrew Buck, all rights reserved

There is some speculation that the Trojans are a source for new short-period comets and Centaurs.  Considering the four discovered around Mars, that puts them in our very near back yard.

Sit down, children, and let me tell you a story:  About 65.5 million years ago, whatever life forms there were present on this planet would have seen a terrible thing; they would have seen the end of the world.  A 10-15 km asteroid impacted the Earth in the Yucatan Peninsula with a force of over a billion times that of the nuclear blasts at Hiroshima and Nagasaki, combined.  The asteroid landed in a bed of gypsum, which would have released sulfur dioxide into the atmosphere.  There would have been a tremendous blast force, dust clouds, megatsunamis higher than any we’ve ever imagined, and an infrared pulse that would have lasted hours, killing by radiation.  Volcanic eruptions, global firestorms… well, I said it was the end of the world.  Anything specialized to an environment, that was picky about what it ate, or larger than a crocodile pretty much went extinct.  Anything that was small and could eat detritus (that would be non-living organic matter like fecal material and other organic trash) had a better chance.

Artist impression of Chicxulub Impact, NASA/JPL

Moving forward to the present time, in 1978 geophysicists working for the oil industry took a look at a strangely symmetrical crater at Chicxulub.  They read 1960s geological studies that theorized the crater was caused by an ancient impact.  The results of their exploration of the area were published in 1981, coincidentally the same year experimental physicist Luis Alvarez published his hypothesis that the K-T Extinction was caused by an impact.  Well, of course it was.  An international panel of 41 scientists has finally looked over all the evidence and have agreed that the extinction event was caused, at least in part, by the impact.  There were other global troubles at the time, which may or may not have caused some species to go extinct, but the event was definitely tipped over and put on the front burner by the impact.

Chixculub Crater, NASA/JPL

The Chicxulub crater itself is more than 180 km in diameter, which makes it one of the largest confirmed impact craters on Earth.  Material recovered from Chicxulub crater has been identified in part as shocked quartz, tektites, large deposits of iridium, andesite glass, and breccia.  You find these features in association with impacts.  I don’t think anyone really would argue that Chicxulub crater was caused by an impact.  Nothing else could have caused it.  It can’t be reproduced by natural Earth processes, and nothing causes shocked quartz except an impact.

Certainly, not every circular structure on the Earth is an impact crater (cough cough volcano), but this one definitely is from an impact; and when it formed, the world ended. I don’t know how many other times it’s happened here (definitely more than once), but I can tell you it will happen again.

Hypervelocity stars, such as the on referenced in Tom’s post, are stars which are moving so fast they have achieved escape velocity from the galaxy.  Sounds cool, but they’re also known as “exiled stars”, so maybe not so much.  They achieve velocity through gravity assist; by getting too close to something of high mass (like a supermassive black hole), and getting a sling-shot out of the galaxy.  The star maintains its shape and life cycle, but any planets that were around it would’ve been lost by the sling.  These are incredible forces you’re dealing with.  There is nothing gentle about the process.

Chandra image of Sgr A*, NASA/CXC/MIT/F. Baganoff, et al

We use the same process when we sling our spacecraft around planets to give them a speed-boost.  It works VERY well.

How common is such an event we don’t know.  We’ve found 16 so far.  The original companion planets of the stars may be on their way out of the galaxy, also, but since they aren’t shiny we don’t see them.  They aren’t still circling their star, that’s for certain.  They all may eventually be captured, but it won’t be in this galaxy.  They’re outta here.

Theorized in 1988 and discovered in 2005, not much yet is known about HVS.  So far, the theory runs that there may be as many as 1,000 of them in the Milky Way Galaxy.  Considering there are 100 billion stars in the Milky Way, that’s not a whole lot.  Still, they sure aren’t hanging around waiting for us to take their picture.  We could be getting new ones all the time.

Some scientists think our HVS could be stars our galaxy originally captured from an orbiting dwarf galaxy which got too close.  Some neutron stars are inferred to be at high velocity, but that’s the result of an asymmetrical supernova.  Not only did it supernova, it supernovaed messily.  An example of that would be the neutron star RX J0822-4300, which moves at 0.5% of light speed, or about 1500 km/s.  That speed doesn’t grab you?  The 125X1400mm shell fired out of a tank travels at about 1700 m/s.  Or about 6120 km/h.  Hmmm, that’s kilometers per second vs kilometers per hour.  These puppies aren’t wasting time.

The first HVS discovered is SDSS J090744.99+024506.8.  Its “other” name is The Outcast Star.  I don’t know which is worse.  One thing is for sure; there are a lot of strange, strange things in the universe.  Some of them in our own back yard.