Planets Everywhere!

In the movie 2001: A Space Odyssey Dr. Dave Bowman gasps “my God, it’s full of stars!” as he gets pulled into the Monolith orbiting Jupiter.

The mantra of astronomy and our existence…it’s all about stars because without stars there is no light.  That’s true and I’m glad we’re here because of stars, especially the Sun.  Another mantra in astronomy has been that stars and their planets by in large stay in their home galaxies.  That paradigm is changing.

In recent years astronomers have discovered isolated intergalactic stars, not gravity bound to a galaxy. That’s news for sure but I had wondered for years if our universe might be littered with interstellar and intergalactic planets too.  Why not?  They could be out there, but we just can’t see them.

Well, my wondering is over, at least regarding interstellar planets.

A dozen interstellar objects have been observed so far, including the luckily caught solar system interloper’s ‘Oumuamua, in 2017 and 2I/Borisov in 2019. We still do not have sensitive enough equipment to find extra solar planets that are not orbiting a star.  Astronomers have found some independent planets so far using what’s called microlensing of a background star’s image when a planet moves in front, due to the planet’s mass.  That will change this decade as two new observatories in the works go live. They will be sensitive enough to spot planets sailing through interstellar space.

On a mountain in Chile the Vera C. Rubin Observatory is expected to begin operations in 2023.  Its mirror is big at 8.4m (330.7 inches) and has a 3200-megapixel camera to boot!  That’s right, 3.2 gigapixels, the biggest digital camera in the world and will survey the entire sky every three nights.  It will be used in three optical configurations depending on the study task.  They are M1 (8.4m f/1.18), M2 (3.4m f/1.00), and M3 (5.0m f/0.83).  That’s some fast optics!

The Nancy Grace Roman Space Telescope will be even higher up, in outer space at what’s termed the Sun-Earth L2 orbit (a Lagrange point, where gravity balances between the Sun and Earth, maintaining a relatively stable position for the satellite).  It’s also a great spot for reducing observing constraints – the Earth will mostly be out of the way.  This roughly Hubble sized telescope (2.4m or 94.5 inches) is designed as a three mirror anastigmat with a very wide well corrected view.  Among its objectives is to look for exoplanets.

Will they find more “independent” planets?  Astronomers are confident they will find many, possibly a bucket load in each field.  If they do, this might result in a modification of how we think of dark matter.  We’ll see.

Without a star to orbit, planets much smaller that Jupiter will be eternally frozen, and they all will be dark.

What’s in the Sky?

March 18 & 19; one hour after sunset; west: A waxing crescent Moon is in Taurus with Mars, Aldebaran, and the Pleiades.