New Horizons’ New Horizons

It’s been almost six years since the New Horizons spacecraft snapped a ton of photos of Pluto and Charon as it whizzed by.  At that time, it was entering the inner edge of our solar system’s Kuiper Belt, a vast doughnut shaped ring of cometary objects and dwarf planets.  Pluto is now considered a Kuiper Belt Object (KBO), a dwarf planet, and the first Kuiper Belt Object found.

Four years later, on New Year’s Day 2019, New Horizons made history by encountering the KBO 486958 Arrokoth (formerly Ultima Thule), snapping some photos and taking spectrophotometric measurements. Arrokoth is a word from the extinct Powhatan language, tidewater region of Virginia.  It means “cloud”. We have learned Arrokoth is a contact binary object, where two objects have fused together after bumping into each other.  It has one large and one small lobe.  It is made up of frozen volatiles (ices) of methanol, hydrogen cyanide, other organic compounds, and water ice.  This is the most distant object an Earthly spacecraft has explored and pictured.

Now it is three years later, and New Horizons continues to press on.  On April 17th New Horizons became the fifth spacecraft to reach 50 AU (astronomical units) distance from our Sun.  That’s 50x the Earth-Sun distance or 50 x 93,000,000 miles.  Only Pioneers 10 and 11, and Voyagers 1 and 2 have gone this far.  So, in commemoration of this milestone, New Horizons took a snapshot of Voyager 1’s position in space.  They are way too separated to see Voyager 1, but it’s out there!

More recently something funny has turned up, and it might turn the cosmology and astrophysics world on its head.  Then again, it might be nothing.

As part of New Horizons’ mission, using its Long Range Reconnaissance Imager (LORRI) camera it measures the cosmic optical background. Comparing its results with that predicted by existing data it seems there is more light than there should be.  Twice as much! This is after subtracting all known and predicted sources of visible light including stars, galaxies (even those too faint for the camera to resolve), and dust scattered Milky Way starlight (from galactic cirrus).  This is big, too big to ignore.  Now what?  I guess report it and see what happens.

This finding was reported in the January 10th Astrophysical Journal and at the 237th meeting of the American Astronomical Society.  The Earth didn’t stop turning, and fortunately, no one’s head exploded.

Cosmologists find this intriguing and are looking at possible explanations for this anomaly. Maybe the team underestimated the how scattered Milky Way light contributes to the optical background.  They might be missing free-roaming stars, undiscovered black holes, faint galaxies.

Or, maybe it has something to do with dark matter, eh? Maybe they are detecting swarms of axions, the hypothetical dark matter particle.

Maybe not.

What’s in the Sky?

June 1; dawn; south-southwest:  A nearly last quarter Moon hangs with Jupiter and Saturn