Solar sailing

Solar sails have been long-discussed as a way to propel spacecraft.  The sails exploit the fact that solar wind exerts pressure on a mirrored surface.   This can be used for propulsion in a way that is akin to sails used by sailboats.

LightSail® is a solar sail project from the Planetary Society that has championed solar sailing for decades. The Society’s LightSail-2 spacecraft, launched 25 June 2019, is the first spacecraft in Earth’s orbit propelled solely by sunlight. On 31 July 2019, the LightSail-2’s orbit was raised, showing that solar sailing is a viable means of propulsion for CubeSats—small, standardised spacecraft that are part of a global effort to lower the cost of space exploration.

 The image above shows LightSail-2's sail after its deployment.

Hayabusa heading home

Japan's Hayabusa-2 spacecraft has departed from the asteroid Ryugu with samples of its soil and begun its year-long journey back to Earth. 

Hayabusa-2 was launched in 2014. Three and a half years later, it reached the asteroid Ryugu, located about 300 million km (190 million miles) from Earth.  The spacecraft is expected to return to Earth in December 2020, dropping a capsule containing the rock samples in the South Australian desert.  

Following its arrival in June 2018, the spacecraft made touchdowns twice, collecting data and rock samples from the Ryugu - a primitive space rock leftover from the early days of the Solar System

Scientists believed these would be more pristine samples, since they would not have been exposed to the harsh environment of space. They were the first underground samples collected from an asteroid in space history.

While asteroids are some of the oldest objects in space, Ryugu belongs to a particularly primitive type of space rock, and may contain clues about the conditions and chemistry of the early days of the Solar System - some 4.5 billion years ago.

Oumuamua

On October 19, 2017, astronomers at Hawaii’s PanSTARRS telescope detected an object in the sky that was moving unusually fast and likely had originated from another solar system. As it was the first interstellar object to be detected within our solar system, they named it Oumuamua, the Hawaiian word for a scout or messenger. (Artist depiction in Wikipedia)

An article at Scientific American describes six unusual facts about Oumuamua. The first one being that astronomers didn’t expect such an object to exist but the most unusual fact about it is that it deviates from an orbit that is shaped by the gravitational force of our sun. As the object is moving, in a hyperbolic trajectory, the question arises what gives it the extra acceleration.  As Oumuamua’s acceleration has not been seen with asteroids astronomers wandered whether the object may be an Unidentified Foreign Object sent to our solar system by an alien civilization.

It is known that there are conditions similar to those on Earth in a quarter of all planetary systems around other stars and there are 100 billion stellar systems in our galaxy the Milky Way.  Also 100 billion galaxies exist in the known universe making the existence of other intelligent beings elsewhere likely.  Could other intelligent beings send a scout to observe our solar system?  Future discoveries about the Cosmos will unravel mysteries such as Oumuamua, fast radio bursts, or what happens to space-time inside a black hole.

An Epic Journey

Voyager I & II are celebrating 40 years of exploration this August and September. Image from NASA.

Amazing planetary encounters in Voyagers’ journey includes discovering the first active volcanoes beyond Earth, on Jupiter’s moon Io and hints of a subsurface ocean on Jupiter’s moon Europa.

Voyager I (top) launched on September 5, 1977, has traveled beyond our solar bubble into interstellar space almost 13 billion miles from Earth. Voyager II (bottom) launched on August 20, 1977, is still exploring the outer layer of the solar bubble, is almost 11 billion miles from Earth. Image NASA/JPL-Caltech

Now that Voyager I has left the solar system, its next big spaceflight milestone comes with a flyby of a star called AC +79 3888, which lies 17.6 light-years from Earth, in 40,000 years from now.  Although the spacecrafts’ science instruments will be turned off by 2030, they’ll continue their journeys at their speed of more than 30,000 mph, completing an orbit within our Milky Way galaxy every 225 million years. 

Each spacecraft carries a Golden Record of Earth sounds, pictures and messages. Since the spacecraft journey could last for millions of years, these time capsules could one day tell the story of human civilization on planet Earth. 

και αν μας βρητε ακομα ζωντανους, εδω στη Ιθακη             

θα σας καλοσωρισουμε, με δωρο αντι δωρου                

και θα γλεντησουμε μαζυ, διοτι ετσι ειναι το εθιμο μας, 

με αυτους που ειναι ποντοποροι

but if you found him alive, here in Ithaca

we would have replied in kind, gift for gift,

and entertained you warmly..

that’s the old custom, when one has led the way

                                                                               from Homer’s Odyssey 24.315-18