Huygens Probe on Titan; Cassini's Final Year; Milky Way Ripping off Neighbors | SFN #190

A look back at the touchdown of the Huygens lander on Titan some twelve years ago and a look ahead at what’s in store for the Cassini later this year; and astronomers find distant stars in the Milky Way were probably ripped off of another galaxy.

Published by Tony Darnell on 13th Jan, 2017

Hello Space Fans and welcome to another edition of Space Fan News. This week, a look back at the astonishing touchdown of the Huygens lander on Saturn’s moon Titan some twelve years ago and a look ahead at what’s in store for the Cassini Spacecraft later this year; and astronomers discover that the most distant stars in the Milky Way were probably ripped off of another galaxy.

First up, this happened before I started doing SFN but because this year marks the last year of operation for one of the most successful solar system probes we’ve ever launched, the Cassini Spacecraft, I wanted to show you this incredibly remarkable video of the descent of the Huygens probe that flew along with Cassini and was destined to land on the enigmatic moon, Titan.

The Huygens lander was built by the European Space Agency as part of the Cassini mission to explore the Saturnian system. Because Titan has a thick atmosphere, we couldn’t really get any details of the surface from above, we needed to land there, so Huygens was detached from the Cassini spacecraft in 2006 for a parachute descent and landing on the surface.

I can never get enough watching this video. While there are some animations at the beginning 30 seconds or so, what I’m about to show you is real data, the actual images taken as the Huygens probe landed.

I downloaded this video from JPL and since they did a great job producing it, I just added some narration of the titles. This video really does speak for itself.

I haven’t said this in a while, but that is just like downtown. Amazing.

Cassini completed its initial four-year mission to explore the Saturn System in June 2008 and the first extended mission, which was called the 'Cassini Equinox Mission', in September 2010.

Then there was a second extended mission, called the 'Cassini Solstice Mission' which his underway now and will continue until September 2017; this will allow scientists to study the Saturnian system until the summer solstice is passed in May 2017.

By the time this new extension is completed the Cassini mission will have covered (since it arrived in the system) one half of a Saturnian year.

So watch this channel folks because in September of this year, the Cassini mission will finally come to a close with something they are dubbing the Grand Finale.

It begins in April, just a couple of months from now, a close flyby of Titan will reshape the spacecraft's orbit so that it passes through the gap between Saturn and the rings - an unexplored space only about 1,500 miles (2,400 kilometers) wide. The spacecraft is expected to make 22 plunges through this gap, beginning with its first dive on April 27.

During the Grand Finale, Cassini will make the closest-ever observations of Saturn, mapping the planet's magnetic and gravity fields with exquisite precision and returning ultra-close views of the atmosphere.

Scientists also hope to gain new insights into Saturn's interior structure, the precise length of a Saturn day, and the total mass of the rings -- which may finally help settle the question of their age.

The spacecraft will also directly analyze dust-sized particles in the main rings and sample the outer reaches of Saturn's atmosphere -- both first-time measurements for the mission.

The Grand Finale will come to a dramatic end on Sept. 15, 2017, as Cassini dives into Saturn's atmosphere, returning data about the planet's chemical composition until its signal is lost. Friction with the atmosphere will cause the spacecraft to burn up like a meteor soon afterward.

So 2017 will bring an exciting conclusion to an amazing mission, one which has taught us more about Saturn and it’s moons than anything that came before. So stay tuned for this channel for updates cuz I will keep you posted as the year progresses.

Next, astronomers who care about what’s going on in the outer reaches of our Milky Way Galaxy have been running some simulations based on observations of ground based telescopes and surveys like the Sloan Digital Sky Survey and found that it looks like our galaxy has been ripping off stars from other, nearby galaxies.

The 11 farthest known stars in our galaxy are located about 300,000 light-years from Earth, well outside the Milky Way's spiral disk. This new research by Harvard astronomers shows that half of those stars might have been ripped from another galaxy: particularly the Sagittarius dwarf galaxy.

Moreover, they are members of a lengthy stream of stars, known as the Sagittarius stream, which extends one million light-years across, or 10 times the width of our galaxy.

The Sagittarius dwarf is one of dozens of mini-galaxies that surround the Milky Way. Over the age of the universe it made several loops around our galaxy. And each time it passes, the Milky Way's gravitational tides tug at it, pulling it apart like taffy.

The Harvard team used computer models to simulate the movements of the Sagittarius dwarf over the past 8 billion years. They tweaked the simulation by varying its initial velocity and angle of approach to the Milky Way until they found what best matched current observations.

At the beginning of the simulation, the Sagittarius dwarf weighed about 10 billion times the mass of our Sun, or about one percent of the Milky Way's mass. Their calculations showed that over time, the dwarf galaxy lost about a third of its stars and a full nine-tenths of its dark matter.

This resulted in three distinct streams of stars that reach as far as one million light-years from the Milky Way's center. They stretch all the way out to the edge of the Milky Way halo and sculpt one of the largest structures observable on the sky.

What’s more, five of the 11 most distant stars in our galaxy have positions and velocities that match what you would expect of stars stripped from the Sagittarius dwarf. The other six do not appear to be from Sagittarius, but might have been removed from a different dwarf galaxy.

It still blows me away that we can do this, starting with observations of what we see going on today, we run some computer models that span billions of years to help us explain what might have been going on in the distant past.

Of course, some of the assumptions that went into making the model may be shown to ultimately be wrong or a little off and need tweaking, but at present it does the best job of describing what we’re seeing when we look through our telescopes at the most distant stars in our galaxy.

Well that’s it for this week Space Fans, I want to thank our sponsor for this week’s episode: dot space domains. DOTSPACE is the new age extension of choice for the space community! As a space enthusiast or professional, you can now get a web address that defines what you do.

Click on this link for a special deal for all my viewers: Register your very own .space domain name for only $2.99, visit www.launch.space.​ This is a good time to stake out your claim to some really cool domain names before everyone else grabs them.

And don’t even think about it: I got DeepAstronomy.space weeks ago. I plan to use it for some online courses I’m creating.

Thanks also to all of the SFN Patreon Patrons, you guys are hard core and make this program possible so big thanks. Thanks to all of you for watching and as always, Keep Looking Up!


Comments

No comments on this page. Be the first?